CA2192579C - Method and apparatus for location finding in a cdma system - Google Patents
Method and apparatus for location finding in a cdma systemInfo
- Publication number
- CA2192579C CA2192579C CA002192579A CA2192579A CA2192579C CA 2192579 C CA2192579 C CA 2192579C CA 002192579 A CA002192579 A CA 002192579A CA 2192579 A CA2192579 A CA 2192579A CA 2192579 C CA2192579 C CA 2192579C
- Authority
- CA
- Canada
- Prior art keywords
- subscriber
- signal
- location
- determining
- base station
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/14—Determining absolute distances from a plurality of spaced points of known location
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/14—Determining absolute distances from a plurality of spaced points of known location
- G01S5/145—Using a supplementary range measurement, e.g. based on pseudo-range measurements
Abstract
A method and apparatus for determining the location of a communication unit in a CDMA system includes in a first embodiment, sending a location request via a spread spectrum signal to the subscriber (140), and receiving in return a subscriber signal including a response message showing a receive time of a particular symbol of the base's spreading sequence and a transmit time of a particular symbol of the subscriber's spreading sequence. The base (130), along with other receiving base(s) (140), also receives a predetermined symbol of the subscriber spreading sequence, and each determines a respective receive time of the predetermined symbol. The received information is then processed, along with known base location and delay information, to determine the subscriber location. If insufficient number of bases are capable of communicating with the subscriber, for example due to high loading/interference, auxiliairy bases (121) are also provided for receiving from or transmitting to the subscriber.
Description
~WO 96/35958 2 1 9 2 5 7 g PCT/US96103797 METHOD AND APPARATUS FOR LOCATION FINDING
IN A CDMA SYSTEM
Field of the Invention The present invention relates, in general, to wireless communication systems and, more particularly, to a method and apparatus for locating a subscriber unit in a Code Division 10 Multiple Access (CDMA) wireless communication system.
Background of the Invention In a wireless communication system it is often desirable 15 to locate users who are making calls. Applications for such a technology would include 911-emergency services, so that policelfire/ambulance services could be dispatched to a user making a call. Other applications would include fraud detection, police investigations, and the like.
Previously installed cellular systems had little capability in this regard. For example, in AMPS (Advanced Mobile Phone System) Cellular Radio, a user could be located within a cell by determining which base station antenna was 25 used to serve the user. However a cell could be as large as 3-5 miles in radius, making this information practically useless.
Since many of the dense urban cell sites are now much smaller, and many of the urbanlsuburban cell sites are now sectorized, using sectored antennas to limit a channel's 30 service area to just one sector of a cell, the coverage areas of a cell are now smaller. However, the area even in these smaller cells can still be more than one square mile. This still makes locating a user impractical for most purposes. Other radio systems, like US Digital Cellular (USDC) and Group 35 Speciale Mobile (GSM) use the same method of identifying the W0 961359~8 PCT/US96/03797 ~
21~379
IN A CDMA SYSTEM
Field of the Invention The present invention relates, in general, to wireless communication systems and, more particularly, to a method and apparatus for locating a subscriber unit in a Code Division 10 Multiple Access (CDMA) wireless communication system.
Background of the Invention In a wireless communication system it is often desirable 15 to locate users who are making calls. Applications for such a technology would include 911-emergency services, so that policelfire/ambulance services could be dispatched to a user making a call. Other applications would include fraud detection, police investigations, and the like.
Previously installed cellular systems had little capability in this regard. For example, in AMPS (Advanced Mobile Phone System) Cellular Radio, a user could be located within a cell by determining which base station antenna was 25 used to serve the user. However a cell could be as large as 3-5 miles in radius, making this information practically useless.
Since many of the dense urban cell sites are now much smaller, and many of the urbanlsuburban cell sites are now sectorized, using sectored antennas to limit a channel's 30 service area to just one sector of a cell, the coverage areas of a cell are now smaller. However, the area even in these smaller cells can still be more than one square mile. This still makes locating a user impractical for most purposes. Other radio systems, like US Digital Cellular (USDC) and Group 35 Speciale Mobile (GSM) use the same method of identifying the W0 961359~8 PCT/US96/03797 ~
21~379
- 2 -cell or sector, and thus could do no better than the AMPS
system .
While there are other location alternatives, such as the use of Global Positioning System (GPS) units at the subscriber unit, or triangulation onto a transmitting subscriber unit, these and similar approaches are too costly to be used by most subscribers, or in the case of triangulation, require other costly and time-consuming resources to be dedicated.
There remains therefore a need for an improved, cost-efficient approach for locating subscribers in a wireless communication system.
Brief Description of the Drawings FIG. 1 is a simplified diagram illustrating a cellular system which may employ the present invention;
FIG. 2 is a block diagram of a CDMA receiver at a subscriber unit according to an embodiment of the invention;
FIG. 3 is a diagram illustrating location finding of a CDMA subscriber unit according to an embodiment of the invention;
FIG. 4 is a diagram illustrating a timing sequence used in d~ler",i"i"g propagation delay for location of a CDMA
subscriber unit according to an embodiment of the invention;
FIG. 5 is a block diagram of a CDMA receiver at a base station according to an embodiment of the invention;
FIG. 6 is a timeline diagram illustrating propagation and delay times used in calculating a subscriber according to an embodiment of the invention;
FIG. 7 is a flow chart illustrating the process by which a subscriber measures base station signals according to an
system .
While there are other location alternatives, such as the use of Global Positioning System (GPS) units at the subscriber unit, or triangulation onto a transmitting subscriber unit, these and similar approaches are too costly to be used by most subscribers, or in the case of triangulation, require other costly and time-consuming resources to be dedicated.
There remains therefore a need for an improved, cost-efficient approach for locating subscribers in a wireless communication system.
Brief Description of the Drawings FIG. 1 is a simplified diagram illustrating a cellular system which may employ the present invention;
FIG. 2 is a block diagram of a CDMA receiver at a subscriber unit according to an embodiment of the invention;
FIG. 3 is a diagram illustrating location finding of a CDMA subscriber unit according to an embodiment of the invention;
FIG. 4 is a diagram illustrating a timing sequence used in d~ler",i"i"g propagation delay for location of a CDMA
subscriber unit according to an embodiment of the invention;
FIG. 5 is a block diagram of a CDMA receiver at a base station according to an embodiment of the invention;
FIG. 6 is a timeline diagram illustrating propagation and delay times used in calculating a subscriber according to an embodiment of the invention;
FIG. 7 is a flow chart illustrating the process by which a subscriber measures base station signals according to an
3 5 embodiment of the invention;
~ WO 96/35958 21 92 ~ 7 9 PCT/llS96103797 ,, . . . ' .
- 3- . -.:
FIG. 8 is a flow chart illustrating the process by which a base station measures subscriber signals according to an embodiment of the invention.
Detailed Description of the Drawings These problems and others are solved by an improved method and apparatus according to the invention. A presently 10 preferred embodiment of the invention is a system for determining the location of a user in a Code Division Multiple Access (CDMA) cellular system. Using the CDMA modulation information, an estimate of the time of flight or propagation is made of the first arriving ray at a subscriber unit. The first 15 ray received typically represents the shortest path between the base and subscriber, and the time of flight estimate allows the c~lclliAtiQn of the distance between the subscriber and the base station. By calculating the distance to multiple, e.g., three, sites, a specific subscriber location can be calculated 20 limited by the accuracies of the measurement timing and other processing delays~
In the preferred embodiment the time of flight of the signal between each base and subscriber is c~lc~ t~d 2 5 automatically within a correlation receiver. The processing steps involve the transl"i~sion of a Pseudo Noise (PN) sequence coded signal time-aligned to under a chip accuracy (e.g., 1/16th of a chip), and correlating on this signal at the receiver using a correlation algorithm. Because the modulation 30 sequence (e.g., a PN sequence) is known and used in ~ synchlullkation/despreading, a precise time of reception of a given chip can be determined. By dt:lellll ,i"g reception time for multiple related signals, a time delay can be c~lc~ t~d and used to determine a position estimate.
WO 96/35958 . ~ ~ t PCT/I~S96103797 ~
21923~~i 4_ In one implementation, the subscriber uses known PN
sequence and offset information to i~d,etermine which related PN
chips from different bases (standard and/or auxiliary bases) that were transmitted at the same time, and also determines 5 the time of reception of these related chips. From the difference between the reception times, a time differential and thus distance differential is determined. Using the distance differentials and known positions of the bases, a position estimate is determined. Where a subscriber is only in 10 communication with one or two bases, additional bases may be forced into an active set (including auxiliary sites, if needed) so that time measurements can be made by the subscriber.
In another implementation, receiving base sites are 15 controlled to make time measurements of selected chips, and the difference in receive time is used to similarly calculate the subscriber position. Where additional receive sites are needed because of interference and the like, auxiliary sites are controlled so as to receive the signals l,dnsr,lilled from the 20 subscriber unit. If necessary, in case of an en,elyellcy~ the subscriber unit is powered up to a maximum power level such that at least three base stations can receive and make a time estimate of the signal. Further, where more precise measurements are needed, a special location message can be 2 5 transmitted to the subscriber. Upon receipt, the subscriber determines a chip/time offset for a response signal, encodes the offset and transmits the response signal. Upon decoding the offset and comparing the receive times of a same chip (e.g., the first chip of a frame) used in det~r,l, li,lg the offset, 30 a delay compensated time value is deter"~ ~ed for the various propagation paths, and the position determined therefrom.
Finally, since it might be difficult to get a received signal at bases further away, an emergency load shedding can be performed at the nearby bases to provide extra range, since 35 capacity can be traded off for range in a CDMA radio system.
~WO 96/359~8 2 :) 7 9 PCT/USg6/03797 Thus coverage is improved, and location finding is made more reliably.
Turning now to FIG. 1, a cellular system is generally depicted as 100 having a hexagonal cell pattern with base stations 110, 120, 130, and a subscriber 140. Auxiliary base units 121 are also located between bases 110, 120 and 130.
The distance between bases 110, 121 and 130 and the subscriber unit 140 is estimated by determining the time of flight or propagation of the first arriving ray which is measured from a predefined reference time to the point in time that the receiver performs a correlation on the transmitted signal. This is made more difficult, in that the distance estimate may be overestimated, or underestimated since the measurement is made to an arbitrary time reference point in the receiver (a precise measurement would only be available if a more accurate (and costly) timing system such as one derived from a GPS signal or atomic clock is used in the subscriber 140). Thus, the distances 150, 160 and 170, respectively, may be longer or shorter than the actual distance between each base 110, 121, 130 and the subscriber 140 based on correlation to a chip rate (at an ap~ l~"d",dlely 814 nanosecond (ns) chip rate (i.e., the rate of the fully spread signal, which is determined in TIA (Telecommunications Industry A~soci~liQn) Intermim Standard IS-95A by the PN
sequence rate), or approximately 250 meters (m) per chip; so it is desirable to achieve time measurements at faster than the chip rate). In FIG. 1, the distance 150 is shown to be overestimated indicating a point 125 beyond the subscriber 3 0 unit's actual location. Likewise points 115 and 135 are also ~ overestimated. These points will be corrected by the distance processing described below, yielding an estimate much closer to the subscriber's true location.
WO 96135958 ~ . PCTIUS96/03797 219257g -6 -FIG. 2 is a block diagram illustrating a CDMA subscriber unit 200 having a CDMA receiver 201, locator unit 202, and transmitter 203. The receiver 201 has a common RF (radio frequency) front end 205 which feeds three independent rake inputs, 210, 220, 230. These rake units 210, 220 and 230 can lock onto three different received rays that are approximately one PN chip time or more apart, which is typical of a direct sequence spread spectrum (DSSS) receiver. The searcher 240 scans for new correlation peaks at faster than the chip rate (in 1 0 the preferred case allowing for resolutions as fast as the 50 ns clock rate), and can reassign the rake inputs based on its best estimate of current channel conditions. Normally, the correlators for rakes 210, 220 and 230 lock onto the three strongest rays that are avaiiable, and when a second or third 1 5 base station can supply a signal sufficiently strong, they are reserved for locking onto these other base stations signals which are also delayed in time more than one PN chip time respectively, as described by the IS-95A Standard. If only two base stations are sufficiently strong, then two rays are 20 dedicated, one for each base station, and the third ray to the strongest remaining ray for either base station.
When a location finding function is desired by the subscriber 200, it is preferable to attempt to find three 2 5 different base stations, one for each ray so that sufficient information is available to accurately estimate the location.
Thus, to connect to three base sites the rakes 210, 220 and 230 are adjusted so that at least three base unit signals are decoded. If available, emergency pilot generators (such as 3 0 auxiliary base unit 121 of FIG. 1) physically located between the base sites could be activated in response to a beacon request in order to blanket the area with additional reference signals, allowing the subscriber to make location estimates based on these pilot generators as well as the standard base 35 sites. These auxiliary units would have a different PN offset ~W0 96135958 1 925 79 ~ t~ ~ ' PCTIUS96103797 ~, than the surrounding base stations, and would typically be equipped with a GPS receiver for proper synchlol1i~dlion/timing~ They would be coupled to the base stations or other controller in the infrastructure by any 5 convenient means, e.g. wireless or twisted pair cable. Their activation is preferably accomplished by a request to the controlier, or command from the serving base station to a local auxiliary unit under its control, upon indication by the subscriber that less than three bases are available.
10 Alternatively, the auxiliary units could be equipped with scanning receivers that, in response to a request signal by a subscriber, would begin transmitting for a limited period (e.g., 5 seconds, in order to minimize system interference). By appropriate placement, such auxiliary units can be used to 15 reduce uncertainties at certain locations or generally increase the accuracy of position finding in strategic areas, such as major highways, malls, or central business districts. Because of the interference-limiting nature of a CDMA system, in some cases only one base station will be able to receive the 2 0 subscriber's signal, and vice-versa, so the auxiliary units are needed to obtain the necessary multiple readings.
The relative time of reception of each signal is determined by using information about the leading edge (or 2 5 alternately, the peaks) of related correlation peaks in the searcher, and adjusting this by an offset determined in a fine time alignment circuit (e.g., delay lock loops (DLLs) 215, 225 or 235 for each branch, coupled with filters 250-270).
Preferably related correlation peaks are those received on 30 different branches but within one chip of each other. In this ~ approach, the precise time of the leading edge is determined, along with the PN sequence number (i.e., the chip position (e.g., number 245) of the repeating PN sequence (e.g., app~uxi",dt~,ly 16,000 chips in length)). Using the already determined PN
35 sequence offset, and the system design where the base PN
WO 96/359~;8 : F~ 797 _ 2192~79 8 sequence is the same for each base station, and transmitted at the same system time plus or minus a unique PN sequence offset, the difference in re!àtive times yields a difference in propagation path delay. This is illustrated in FIG. 3. At time 5 T0 two bases B1 and B2 are lldns",itli"g, but base B1 transmits PN chip 0, while base B2 transmits PN chip 256 since it has a PN sequence offset of 256 chips. At some time T1, after location finding is activated, the subscriber determines that the leading edge of PN chip 4 from B1 has been 1 0 received. The next leading edge of a PN chip from base B2 is received 1/8th of a chip later at time T2, and the chip is determined to be the 280th in the PN sequence. From these receive times and PN numbers, the propagation delay difference is calculated to be ((PNB2 - offset) + (receive 1 5 difference, T2-T1)) - (PNB1 - offset) = ((261-256) + (1/8)) -(4-0) = 1 1/8 chips ~ 814 ns/chip = 916 ns. At applc,ki",dt~,ly 1/3 meter (m) per ns p,opayt.Lion speed for a radio signal, this translates into about 300 m difference in propagation path distances. The precision in location is only iimited by the 20 system clock rate being used and degree of sy"uhluni,dtion.
Where all base stations are using GPS timing inrum~alioll, synchronized transmissions (i.e., of the leading edges of chips) to within 50 ns (or approximately 1/16th of the chip rate) are currently possible. With a local clock generating at least the 25 same 20 MHz clock rate, location to within 100 ns or 30 m is possible .
Retuming to FIG. 2, DLLs 215, 225, and 235 are fed back to each rake 210, 220 and 230, respectively, for adjusting the 30 signals to output fine time aligned signals. As noted above, the DLL outputs can also serve as fine phase offset i"roll"dlion for adjusting the receive times of the PN chips, preferably after filtering in Low Pass Filters (LPFs) 250, 260, 270 for each channel, respectively, which effectively averages 35 the outputs of each DLL 215, 225, 235. This averaged fine -~WO 9G/35958 21 g 2 S 7 9 PCTNS96/03797 g r ~
phase offset information, together with the chip number/times/base identification or offset (i.e. B1-B3 information) from searcher 240 (which is also adapted for PN
chip/time detection), are fed to location searcher 280.
Location searcher 280 takes the fine phase offset information from each branch and corrects the time of reception from searcher 240 for each chip, to give a corrected relative time of reception for each branch. From the earliest time, say B1 (i.e., the time the signal from base 1 is received), the 1 0 difference tB21 and tB31 in reception time for the other signals B2 and B3 is determined, and the cor,e~,ol1ding distances dB21 and dB31 determined. One thus knows that the distance from bases 1 (110), 2 (120) and 3 (130) are dB1, (dB1 + dB21) and (dB1 + dB31), respectively. Further, from the PN
1 5 offsets, the identity of the bases are known and their geographic position can be retriev0d from memory 281. It is then a simple matter of performing a search routine to determine, one such as illustrated in FIG. 4, to determine the geographic coordinates of the mobile. In the example of FIG. 4, the known base locations are used to define three lines L12 (151), L23 (152) and L13 (153). The distances dB21 and dB31 are subtracted from lines L12 (151), L23 (152) and L23 (152), L13 (153) respectively, and the remaining segments bisected by normal lines N12 (154), N23 (156) and N13 (155). The intersection of these lines N12 (154), N23 (156) and N13 (155) is the position of the subscriber 140. This information could then be sent to the serving base station for forwarding to a requesting party of serving location register, or could be forwarded for use by the subscriber (e.g., on a map grid or 3 0 other location device, not shown).
Alternatively, if base site location information is not available to the subscriber, the phase offset, chip, timing and base offset information can be sent in a location request signal to a serving base station. There, a location searcher can WO 96/35958 ~ ?, ~ I PCT/I~S96/03797 ~
2 ~ n ~ 0 -S ~
access its own database and determine the subscriber location.
This location information is then transmitted back in a location response message to the subscriber or other requesting entity.
A preferred approach, however, for location using infrastructure equipment can be seen with reference now to FIG. 5, which generally depicts a block diagram of a CDMA
infrastructure system 300 having a first CDMA base station 10 301. Base 301 has a common RF front end 3û5 which feeds four independent rake inputs, shown as 310, 320, ... 330. These rakes can lock onto four different received rays that are at least one PN chip time apart, which is typical of a DSSS
receiver. The two searchers 340 scan for new correlation 15 peaks, and can reassign the rakes based on its best estimate of current channel conditions. Normally, the four correlators of rakes 310, 320, 330 lock onto the four strongest rays that are available.
2 0 When a location finding function is desired, two general approaches are av~ lr cither passive (i.e., no subscriber unit response) or active. In either case it is preferable to find at least three different base stations capable of receiving a subscriber signal, so that sufficient information is available to estimate the location. In a first en,l;~odi",e"l passive mode, four rake branches 310, 320 ... 330 of base 301 are used to detect an uplink signal. From each rake, a Delay Lock Loop (DLL) is used to generate an estimate of the timing (i.e., adjustment) of the correlated ray This more accurately 30 estimates the time of the correlation, similar to the process used by the subscriber unit above. Searcher and Chip/Time Detector 340 peak correlates the signal on each branch, and also determines the best branch to use (preferably based on the earliest received peak for the same chip, but other 35 selection techniques may be used to determine a current best ~WO 96~359~8 1 9 2 ~ 7g PCT~S96/03797 ., r~
branch); this best branch signal is used in determining PN chip and receive time information, similar to that in subscriber searcher 240.
To initiate a location process, in a preferred embodiment a command is initiated within the system 300, most likely at a regional entity such as a mobile switching center (MSC) 365, operations center, or perhaps within a connected network such as PSTN (public switched telephone network) 375. A location request is then plucessed via home location register (HLR) 366 to determine the currently serving base station(s). Upon receipt of a location command, plocessor 350 of base 301 (and similar processors of other serving bases) uses detector 340 to determine a chip receive time. Preferably this is accor", ' ~hed by all bases detel", li"g the leading edge rise time of a specified group of PN chips, for example by determining the rise time for each 64th chip (i.e., PN sequence number 0, 64, 128, etc.) for a pledetel", ,ed number of chips, e.g., 10. This information is then forwarded by each base 2 0 receiver, along with its iD (identification), to a designated entity, e.g. Iocation searcher 361 of BSC (base site controller) 360, or location searcher 367 of HLR 366, etc.. Thus, the difference in receive time for the same chips, each chip being derived from the same single chip ~l~ns",;ssiol1, may be used 25 to determine propagation delay differences. In other words, for each chip number the differential between receive times at the different bases yields a propagation difference, and location may be determining this information in conjunction with the known location of the receiving bases, in a similar 30 manner as described above with FIG. 4. By taking plural sets of information in a relatively short time frame (e.g., 10 times, every 64 chips, across about 500 ",;~ ,cseconds), and averaging ~ or otherwise best-fit calculating using the determined positions, position errors can be minimized. A skilled artisan 35 will appreciate that other approaches can be used in the actual W O 96135958 ~ ~ ~ ' PC~rrU596103797 ~
2 1 9 2 ~ 7 ~ - 1 2 -calculation. For example, a detection at the same system time(s) for leading edges within one chip of the desiy"ated time(s), along with time differences from the designated system time and chip number, could be used in determining the 5 propagation delay differences (albeit, an additional error may arise because the transmit time for the different chips is limited by the accuracy of the subscriber's clock rate; even if a 50 ns clock cycle were present, this is still more error than present from a transl";ssio" of the same chip (which has no 1 0 timing error). What is important is that the chip ID (e.g., number/position in the PN sequence) and precise time of reception (e.g., leading edge, or peak, at the oversampled clock rate) at different bases be used in determining the subscriber location .
In a preferred embodiment for active location, a two-way ranging system is implemented using both chip receive time information and certain response information from the subscriber. In this embodiment, the process is again initiated 20 with a location request in the system infrastructure, forwarded to base 301 which is in communication with the subscriber. Processor 350 forwards a location request signal (LOC_S 351) for app,upridl~ encoding by encoder 352 and spreading modulator 355. Using a system clock 353 25 (preferably GPS derived, but other precise means such as an atomic clock may be used), fine time adjuster 354 (e.g., a strobe generator) controls the modulator 355 to precisely output the leading edge of the output chips, preferably within 50ns accuracy. Processor 350 also determines via modulator 30 355 and clock 353 a precise system time for a reference chip (say, chip 1024 of a sequence of 16384 chips, at system time TS(0)), from which other chip tran ",ission times can later be determined. The output chip sequence is then transmitted to the subscriber.
~WO 96/3S958 ~ 2 ~ 7 ~ ~ f ~ - PCT/llS96103797 . ~
Referring once more to FIG. 2, following demodulation and receipt of the location request signal 351, processor 280 controls searcher 240 to determine ID and timing information for a next PN chip, in a similar manner as described above. For 5 purposes of illustration, let us say the determined chip is 1088 (of the base PN sequence) at subscriber relative time TR(0). In order to provide accurate ill~c,lll,dliol1 for turn around time within the subscriber, processor 280 then determines a local time at which a predetermined chip of the subscriber PN
10 sequence will next be l,~nsr"illed. For convenience, this predetermined chip is preferably selected as one of a repeating series (say every 50th chip of the subscriber's PN sequence) yet to be transmitted (say, chip 100); almost any other chip could be selected, e.g., the first chip for the next 20 ms frame, 15 but preferably with a view to minimizing subscriber precise-timing output requirements and system location processing. In any event, the selected chip's local time for output from modulator 291 of transmitter circuit 203 is determined, e.g., by determining a current chip's output time (e.g., via PN/Time 2 0 detector 292) and calculating forward to determine the predetermined chip's output time (say, chip 100 at TR(24 1/16), relative time here being measured in chip rate intervals). Of course, if no current ll~ns",issiol1 is in progress a sufficient delay time would be given (e.g., approximately 2 25 seconds) for the bases to train to the subscriber's PN sequence before transmission of the predetermined chip. The processor would then forward a location response signal RESP 282 for encoding by encoder 290, and would control modulator 291 to precisely output the predetermined chip at the determined 30 time (i.e., TR(24 1/16)), and, if a periodic group of chips is to ~ be monitored, to precisely output any subsequent chips of the periodic group (e.g., chips 150, 200, etc.) for a predetermined period. The RESP 282 would include the base chip information (1088, TR(0)), the predetermined chip information (100, TR(24 35 1/16), and, if not already known by the infrastructure as part WO 96135958 = PCTIIIS96/03797 2192a79 -1 4-of the subscriber unit profile, a predelt:r",;"ed (i.e., calibrated/calculated) subscriber delay factor for pre-acquisition and post-output delays (i.e., the time it takes a signal at the antenna to reach searcher 240, and for an output 5 signal to be radiated at the antenna following the time-precise output from modulator 291).
Returning to FIG. 5, at the same time the system controls base 301 to send the location request signal 351, it also 10 notifies the other communicating bases to begin storing location information. Where there are less than 3 bases in communication (i.e., soft-handoff) or capable of receiving the subscriber signal, the originating entity (e.g., location searchers/processors 361 or 367) will command one or more 15 auxiliary base stations, such as base 356, located in the vicinity of the serving bases to begin receiving at the subscriber's designated frequency. Thus, in the simplest imple-"enl~lion the auxiliary bases could be tunable receivers with a precise system clock (e.g., a GPS-corrected clock); if an 20 auxiliary base was not connected via wireline to a BSC, the auxiliary base could be implemented as fixed subscriber unit (such as a wireless access fixed unit (WAFU)), the only difference from a subscriber being that the WAFU would be operating at system time (e.g., via the GPS clock). In this 2 5 latter embodiment the WAFU would communicate its location response i"rur" ,ation via its own serving base station, e.g .
base 3û1.
All receiving bases, e.g., base 301 and auxiliary base 3 0 356, begin storing subscriber chip/time information upon initiation of the location request. The stored information could be the time (e.g., leading edge receive time) and chip number for each chip received for a predetermined period.
Rather than saving every chip, which in one 20 ms frame would 35 mean close to 25,000 entries, a periodic number of chips (e.g., ~lg2~79 ~ WO 96/35958 ; ~, PCTIUS96/03797 ~ ,~
every 50th chip in the sequence) is preferably used by all receiving bases; in this latter case the subscriber would be configured as ~iiscu~sed above so as to choose a predetermined chip that is one of these periodic chips (such as chip 100). A
skilled artisan will appreciate that any number of periods, or specific chips (e.g., the first chip of a frame) can be used, as long as information is being gathered on the same chip(s) at all bases in order to minimize error. Preferably, for convenience, an appropriately configured subscriber will select the 1 0 predetermined chip so as to coincide with the chip(s) being monitored for by the bases, thus simplifying later calculations; the selection could be based on preprogramming, or upon data in the location request signal 351 indicating the chip(s)/period to be monitored (in which case only the 1 5 predetermined chip(s) need be precisely outputted).
Upon receiving the spread RESP signal from the subscriber (preferably sent via in-band signaling with any ongoing voice/data communications), pl~,cesso,~ 350 and 358 of bases 301 and 356 detect the signal and predetermined chip information, and forward some predetermined number of chip/time pairs to location searcher 361 or 367. For example, to allow for averaging to improve accuracy, each base 301, 356 may forward 8 chip/time pairs, starting with the predetermined chip and its receive time (e.g., pairs 1100, TS(28 7/16)}, ~150, TS(78 7/16)}, ... {450, TS(378 8/16)}, along with the RESP signal information (e.g., the base chip/time pair {(base)1088, TR(O)}, the predetermined chip/time pair {(subscriber)100, TR(24 1/16)}, and known 3 0 delay factor {4/32}). A timeline illustrating this sequence is ~ shown in FIG. 6. TS(O) represents a starting system time, shown here as the 0th bit of the system clock for convenience, while TR(O) represents the subscriber's relative clock time.
PNB1 (1088) represents the 1088th chip in the first base 35 station's (301) PN sequence, while PNS(100) represents the W O 96/35958 2 1 9 2 5 7 9 PC~rrUS96/03797 ~
100th chip in the subscriber's PN sequence. Thus, base chip 1088 is outputted at system time 0, and radiated from the base antenna a transmit delay time ~tB1 later. After a propagation delay ~P1 and subscriber receive delay time ~rS
5 (i.e., from the subscriber antenna to detector 240) later, detector 240 determines chip 1088 to be received at TR(0).
Processor 280 then determines the next 50th chip of the subscriber sequence to be chip 100, and calculates from a current subscriber chip/time that the output time for chip 100 1 0 will be TR(24 1/16). Knowing the calibrated delays ~rS and ~tS (the delay from output to antenna radiation), say 2/32 chips each, the subscriber sends the RESP signal 282 including information, e.g., [{1088,TR(0)}, {100,TR(24 1 /16), {4/32}].
1 5 Base 301 detector 240 receives subscriber chip 100 at system time TS(28 7/16) and base 357 receives it at time TS(29 7/16), with propagation and receive (i.e., antenna to detector) delays of ~P2, ~rB1 and ~P3, ~rB2, respectively.
Similar repeat measurements are also performed, for example 20 base 301 receiving chip 150 at time TS(78 7/16), the subscriber having controlled the output time of chip 150 to TR(74 1/16), i.e., precisely 50 chips (40,700 ns) later.
After a pred~ ",il,ed number of pairs are determined, 2 5 the chip/time information and response signal information are forwarded to the location searcher 361 or 367. The searcher 361 or 367 then cAIclll~tRs the propagation delays, e.g., ~P1 -~P3, using the other known i"~ol",a~ion. In this case, let the calibrated base delays ~tB1, ~rB1 and ~rB2 be 5/32, 3/32 and 30 3132 chips. Because ~P1 is essentially the same as ~P2, then 2~P1 = (TS(28 7/16)-TS(0)) - (~tB1 + ~rB1) - (TR(24 1/16) -TR(0)) (~rS + ~tS) Eq.1 ~2~ l ~
W096/35958 PCT~S96/03797 - 17- ~ "
= (28 7/16) - (8/32) - (24 1/16) - (4132) = 4 chips Thus, ~P1 is 2 chips, or 1628 ns, and the propagation path length is about 488 m (+/- 30 m at 100 ns total uncertainty).
Once ~P1 is known, ~P3 can similarly be c~lc~ terl yielding in the illustrated case a time of 3 chips and distance of 733 m.
10 By calculating the propagation path length for at least three receivers, and retrieving the location information on the receiving bases (e.g., from ~l~t~h~.~e~ 362 or 368) the position of the subscriber may be determined by calculating the unique point (or small region of highest probability) at which the 15 respective propagation paths can all intersect. The process is repeated for each time/chip set. Each calculated point (or centroid of the probably region) is then used in determining the subscriber location, e.g. most simply by averaging, although any suitable process for fitting determining a most likely 20 point/region from multiple points/regions can be used. The location of the most likely poinVregion is preferably stored in the user profile database 369 of HLR 366. Additionally, the entire process can be repeated after one or more further periods of time, on the order of seconds or minutes, with the 25 plural most likely regions being used to determine a speed and direction of travel of the subscriber; if an accurate enough subscriber clock is being used so drift is under 50 ns for an extended period of multiple minutes (i.e., the subscriber clock's offset from the system time is known for that period), 30 repeated detections at the bases could be performed without the need to repeat the request signal). Finally, the determined location, and travel speed/direction, are forwarded to the ~ originally requesting entity, e.g. to operator 370 or via PSTN
375.
W096/35958 ~ PCT/US96/03797 ~
7 ~ - 1 8 -~ iJ V
A particular advantage of using the active location process over the inactive one is that, if desired, three-dimensional information can be more accurately determined.
This is particularly useful in urban or hilly areas, where the 5 angle of incline for the propagation paths can be significantly greater than 0 degrees from the horizon. While three dimensional coordinates of the bases, and known topography of a first approximation subscriber location, can be used to increase the accuracy of the passive process, a skilled artisan 10 will appreciate that a better approximation can be derived from the measured propagation time, as opposed to just differences in propagation times. Because the determined propagation paths are as accurate in three dimensions, it is just a matter of additional processing of the z-axis (i.e., third 15 dimension) coordinates of the base site locations, along with their x- and y-axis coordinates, to determine the three-dimensional region of probable location. If this is compared against known building and topographical information, location to within +/- 8 stories (at 100 ns uncertainty) or better in a 2 0 single building is may be possible. Additional information, such as relative received signal strengths and likely path loss characteristics into a building, could be used to further narrow the region of probable location.
2 5 FIG. 7, generally designated as 400, is an illustrative flow chart of the system process for a subscriber measuring base station signals to obtain a location estimate. The process is started in block 405, which represents the occurrence of a location command to be performed by the subscriber (e.g., by subscriber initiation, or automatically based on other indicator such as a motion sensor indicating a vehicle crash). Block 410 checks the status of the subscriber and a decision is made 415 based on whether or not the subscriber is in 3-way soft handoff. If it is not, block 420 is executed which tests to see if there are three bases in the 2192~79 ~WO 96/359~8 PCT/I~S96/03797 -19- ~ ~ ~
.~ .
candidate set. If not, decision block 425 is tested to check the threshold of adding bases to the candidate set. If this is not at the minimum, block 430 reduces the threshold and returns to process step 420. If block 425 is at a minimum level already, block 450 is executed. This block differentiates the location function between an emergency and non-emergency function.
Thus, if a non-emergency function is being processed, system level changes are permitted only when the level of use is not high, since this could result in users loosing service by raising 1 0 the interference level. In a non-emergency at high system loading, block 460 is executed. If an emergency is indicated, block 455 is executed before block 460. This occurs preferably in response to an emergency beacon signal to which the auxiliary pilot generators are tuned, and will 1 5 automatically respond to; alternatively, an emergency signal can be sent to a serving base and l~r-Jcessed to control the auxiliary bases to activate. In the latter case, a second non-emergency request signal could be similarly used, with an activation command being generated if the control processor (e.g., processor/searcher 361 of BSC 360 in FIG. 5) indicates system loading is beneath a loading threshold. Block 455 thus activates nearby pilot generators that provide more complete coverage of the service area by multiple sites, allowing the subscriber to receive a signal from multiple bases. Block 460 2 5 tests to see if the subscriber is in 3-way soft handoff. If not, the subscriber is instructed 465 to form a 3-way soft handoff condition using the largest rays from at least three base stations. If the result of 460 was positive, or block 465 was completed, block 440 is executed and the collection of data is made as described above in connection with FIG. 2. This data is used to process the location estimate (e.g., in searcher 280 using additional data from memory 281 of FIG. 2), and the system is returned to nominal conditions 445.
WO96/35958 P~ /03797~
219257~ -20-Returning to block 415, if the subscriber is in 3-way handoff, block 440 is executed. Returning to block 420, if there are three bases in the candidate set, block 435 is executed, which places three different bases in the active set.
5 Then block 440 is executed, as described earlier, followed by block 445.
FIG. 8, generally designated as 500, is an illustrative flow chart of the process for the base stations measuring the 1 0 subscriber unit to obtain a location estimate. The process starts in block 505 when the location function is activated.
Block 510 checks the status of the subscriber and a decision is made 515 based on whether or not the subscriber is in 3-way soft handoff. If it is not, block 520 is optionally executed, 1 5 which tests to see if there are three bases in the candidate set. If not, decision block 525 is tested to check the threshold of adding bases to the candidate set. If this is not at the minimum, block 530 reduces the threshold and returns to process step 520. If block 525 is at a minimum level already, 2 0 block 535 is executed, which will continue the prucessi"g of the location e~li",dlion, but now with only two bases, which is less accurate than the desired case of having three bases in the measurements. Returning to block 515, if the subscriber is in 3-way soft handoff, or block 520 if three bases are in the 25 candidate set, then block 540 is executed. Block 540 insures that the three base stations are active for receiving the subscriber's signal. Then block 545 is optionally execllt.orl This biock tests to see if each base can receive the subscriber.
If each base can, block 550 is executed which sends a location 30 request signal if in active mode, and in both modes collects the available data and processes the location estimate in the manner described above. Block 555 follows returning all parameters to normal and the measurements are complete.
Returning to block 545, if less than three bases can receive 3 5 the subscriber, block 546 tests to see if auxiliary base units ~WO 96135958 ~ ) 7 9 PCT/US96103797 are available. If so, the local auxiliary sites are activated in block 547, and block 560 tests to see if an emergency is indicated. If not, only the bases that are received can be used in the measurements, and this can degrade the quality of the 5 estimate. If an emergency is indicated (e.g., by a subscriber signal such as the dialed digits 911, or emergency request from an authorized entity connected to the infrastructure), block 565 is executed to test if the subscriber unit is at maximum power. If not, block 570 is executed to increase the 1 0 power and the process returns to block 540. If block 565 is at maximum power, block 575 tests to see if each base can receive the subscriber. If so, block 550 is executed; otherwise the cell loading is reduced by block 580 to increase the effective range of the cells in the active set that are having 1 5 difficulty receiving the subscriber unit. Then block 585 tests to see if the load shedding limit has been reached, and if so, block 550 is executed; otherwise, decision block 575 is executed again to test to see if each base can now receive the subscriber.
Thus, it will be apparent to one skilled in the art that there has been provided in accordance with the invention, a method and apparatus for estimating the location of a subscriber unit of a wireless communication system that fully 2 5 satisfies the objectives, aims, and advantages set forth above.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to 30 those skilled in the art in light of the foregoing description.
~ For example, while the searchers 240 and 280 of the subscriber unit 200 and searcher 340 and processor 350, and ~ other circuits, of the base station 301 are described in terms of specific logical/functional circuitry relationships, one 35 skilled in the art will appreciate that such may be embodied in W096/35958 ~ PCT/IJS96/03797 ~
a variety of ways, such as appropriately configured and programmed processors, ASlCs (application specific integrated circuits), and DSPs (digital signal plucessol:,). Further, the invention is not limited to determining location via chip 5 information in an IS-95 CDMA system, but has applicability to any CDMA system using spreading symbol sequences. Thus, it should be understood that the invention may include in a first embodiment of active searching: a method and apparatus operable for determining the location of a subscriber unit in a 10 CDMA wireless communication system having plural base stations, col"prisi"g: (a) sending a first spread spectrum signal including a location request from a first base station of the plural base stations to the subscriber unit, the spread spectrum signal being spread by a known first sequence of 15 spreading symbols; (b) receiving at the first base station a second spread spectrum signal including a response message from the subscriber unit, the second spread spectrum signal being spread by a known second sequence of spreading symbols, and the response message ~;OIIl~lib;llSl a receive time of a first 20 symbol of the first sequence and a transmit time of a first symbol of the second sequence; (c) receiving a predetermined symbol of the second sequence at the first base station and at least a second base station, and determining a first and a second receive time of the predetermined symbol at the first 25 and second base station, respectively; and (d) determining a location of the subscriber unit from the receive time of the first symbol of the first sequence by the subscriber unit, the transmit time of the first symbol of the second sequence by the subscriber unit, the first and second receive times of the 30 predetermined symbol, and known information about the first and at least second base stations. A further ~",bo.lh"er,l may include: a method and apparatus operable for determining a subscriber location in a CDMA communication system having plural base stations, comprising: (a) receiving a signal from 35 the subscriber at each of a first base station, a second base . 21g2379 W O 96135958 PC~rrUS96/03797 - 2 3 - , . .
station and a third base station, the signal being formed via modulation by a known sequence of spreading symbols; (b) determining a first receive time of a symbol of the known sequence of spreading symbols at the first base station, a 5 second receive time of the symbol at the second base station, and a third receive time of the symbol at the third base station; and (c) determining the location of the subscriber unit in a location processor from the first, second and third receive times and further known information about the first, second 10 and third base stations. In yet another embodiment there is: a subscriber unit operable for determining its own location while communicating in a CDMA wireless communication system having plural base stations, the subscriber unit comprising: (a) receiver means for receiving a first signal 15 from a first base station of the plural base stations and a second signal from a second base station of the plural base stations, the first and second signals being formed via modulation by a known first sequence of spreading symbols and a known second sequence of spreading symbols, respectively;
2 0 (b) detector means for determining a first receive time of a first symbol of the first sequence, and a second receive time of a further symbol of the second sequence; and (c) location processor means for determining the location of the subscriber unit from the first and second receive times and further known 25 information about the first and second base stations. A yet further emboiment includes: a method for determining a location of a subscriber in a CDMA communication system having plural base units including active base stations and inactive units, comprising: (a) receiving a signal indicative of 3 0 an emergency; (b) determining if at least three of the active base stations can receive a signal from the subscriber, and if not, activating at least one of the inactive units as an auxiliary base station; (c) controlling a group consisting of at least three of the active base stations which can receive a 3 5 signal from the subscriber, and any auxiliary base stations 2192~7~ -24-activated in step (b), to each transmit a spread spectrum signal having a same symbol sequence; (d) clel~n~ .,g each receive time at the subscriber of a same symbol of the symbol sequence for each spread spectrum signal transmitted in step 5 (c), respectively, and sending a response from the subscriber including said each receive time; and (d) determining the location of the subscriber from said each receive time and further known information about the group.
Accold;,l~Jly, it is intended that the invention not be limited by the foregoing description of embodiments, but to embrace all such alterations, modifications, and variations in accordance with the spirit and scope of the appended claims.
15 We claim:
~ WO 96/35958 21 92 ~ 7 9 PCT/llS96103797 ,, . . . ' .
- 3- . -.:
FIG. 8 is a flow chart illustrating the process by which a base station measures subscriber signals according to an embodiment of the invention.
Detailed Description of the Drawings These problems and others are solved by an improved method and apparatus according to the invention. A presently 10 preferred embodiment of the invention is a system for determining the location of a user in a Code Division Multiple Access (CDMA) cellular system. Using the CDMA modulation information, an estimate of the time of flight or propagation is made of the first arriving ray at a subscriber unit. The first 15 ray received typically represents the shortest path between the base and subscriber, and the time of flight estimate allows the c~lclliAtiQn of the distance between the subscriber and the base station. By calculating the distance to multiple, e.g., three, sites, a specific subscriber location can be calculated 20 limited by the accuracies of the measurement timing and other processing delays~
In the preferred embodiment the time of flight of the signal between each base and subscriber is c~lc~ t~d 2 5 automatically within a correlation receiver. The processing steps involve the transl"i~sion of a Pseudo Noise (PN) sequence coded signal time-aligned to under a chip accuracy (e.g., 1/16th of a chip), and correlating on this signal at the receiver using a correlation algorithm. Because the modulation 30 sequence (e.g., a PN sequence) is known and used in ~ synchlullkation/despreading, a precise time of reception of a given chip can be determined. By dt:lellll ,i"g reception time for multiple related signals, a time delay can be c~lc~ t~d and used to determine a position estimate.
WO 96/35958 . ~ ~ t PCT/I~S96103797 ~
21923~~i 4_ In one implementation, the subscriber uses known PN
sequence and offset information to i~d,etermine which related PN
chips from different bases (standard and/or auxiliary bases) that were transmitted at the same time, and also determines 5 the time of reception of these related chips. From the difference between the reception times, a time differential and thus distance differential is determined. Using the distance differentials and known positions of the bases, a position estimate is determined. Where a subscriber is only in 10 communication with one or two bases, additional bases may be forced into an active set (including auxiliary sites, if needed) so that time measurements can be made by the subscriber.
In another implementation, receiving base sites are 15 controlled to make time measurements of selected chips, and the difference in receive time is used to similarly calculate the subscriber position. Where additional receive sites are needed because of interference and the like, auxiliary sites are controlled so as to receive the signals l,dnsr,lilled from the 20 subscriber unit. If necessary, in case of an en,elyellcy~ the subscriber unit is powered up to a maximum power level such that at least three base stations can receive and make a time estimate of the signal. Further, where more precise measurements are needed, a special location message can be 2 5 transmitted to the subscriber. Upon receipt, the subscriber determines a chip/time offset for a response signal, encodes the offset and transmits the response signal. Upon decoding the offset and comparing the receive times of a same chip (e.g., the first chip of a frame) used in det~r,l, li,lg the offset, 30 a delay compensated time value is deter"~ ~ed for the various propagation paths, and the position determined therefrom.
Finally, since it might be difficult to get a received signal at bases further away, an emergency load shedding can be performed at the nearby bases to provide extra range, since 35 capacity can be traded off for range in a CDMA radio system.
~WO 96/359~8 2 :) 7 9 PCT/USg6/03797 Thus coverage is improved, and location finding is made more reliably.
Turning now to FIG. 1, a cellular system is generally depicted as 100 having a hexagonal cell pattern with base stations 110, 120, 130, and a subscriber 140. Auxiliary base units 121 are also located between bases 110, 120 and 130.
The distance between bases 110, 121 and 130 and the subscriber unit 140 is estimated by determining the time of flight or propagation of the first arriving ray which is measured from a predefined reference time to the point in time that the receiver performs a correlation on the transmitted signal. This is made more difficult, in that the distance estimate may be overestimated, or underestimated since the measurement is made to an arbitrary time reference point in the receiver (a precise measurement would only be available if a more accurate (and costly) timing system such as one derived from a GPS signal or atomic clock is used in the subscriber 140). Thus, the distances 150, 160 and 170, respectively, may be longer or shorter than the actual distance between each base 110, 121, 130 and the subscriber 140 based on correlation to a chip rate (at an ap~ l~"d",dlely 814 nanosecond (ns) chip rate (i.e., the rate of the fully spread signal, which is determined in TIA (Telecommunications Industry A~soci~liQn) Intermim Standard IS-95A by the PN
sequence rate), or approximately 250 meters (m) per chip; so it is desirable to achieve time measurements at faster than the chip rate). In FIG. 1, the distance 150 is shown to be overestimated indicating a point 125 beyond the subscriber 3 0 unit's actual location. Likewise points 115 and 135 are also ~ overestimated. These points will be corrected by the distance processing described below, yielding an estimate much closer to the subscriber's true location.
WO 96135958 ~ . PCTIUS96/03797 219257g -6 -FIG. 2 is a block diagram illustrating a CDMA subscriber unit 200 having a CDMA receiver 201, locator unit 202, and transmitter 203. The receiver 201 has a common RF (radio frequency) front end 205 which feeds three independent rake inputs, 210, 220, 230. These rake units 210, 220 and 230 can lock onto three different received rays that are approximately one PN chip time or more apart, which is typical of a direct sequence spread spectrum (DSSS) receiver. The searcher 240 scans for new correlation peaks at faster than the chip rate (in 1 0 the preferred case allowing for resolutions as fast as the 50 ns clock rate), and can reassign the rake inputs based on its best estimate of current channel conditions. Normally, the correlators for rakes 210, 220 and 230 lock onto the three strongest rays that are avaiiable, and when a second or third 1 5 base station can supply a signal sufficiently strong, they are reserved for locking onto these other base stations signals which are also delayed in time more than one PN chip time respectively, as described by the IS-95A Standard. If only two base stations are sufficiently strong, then two rays are 20 dedicated, one for each base station, and the third ray to the strongest remaining ray for either base station.
When a location finding function is desired by the subscriber 200, it is preferable to attempt to find three 2 5 different base stations, one for each ray so that sufficient information is available to accurately estimate the location.
Thus, to connect to three base sites the rakes 210, 220 and 230 are adjusted so that at least three base unit signals are decoded. If available, emergency pilot generators (such as 3 0 auxiliary base unit 121 of FIG. 1) physically located between the base sites could be activated in response to a beacon request in order to blanket the area with additional reference signals, allowing the subscriber to make location estimates based on these pilot generators as well as the standard base 35 sites. These auxiliary units would have a different PN offset ~W0 96135958 1 925 79 ~ t~ ~ ' PCTIUS96103797 ~, than the surrounding base stations, and would typically be equipped with a GPS receiver for proper synchlol1i~dlion/timing~ They would be coupled to the base stations or other controller in the infrastructure by any 5 convenient means, e.g. wireless or twisted pair cable. Their activation is preferably accomplished by a request to the controlier, or command from the serving base station to a local auxiliary unit under its control, upon indication by the subscriber that less than three bases are available.
10 Alternatively, the auxiliary units could be equipped with scanning receivers that, in response to a request signal by a subscriber, would begin transmitting for a limited period (e.g., 5 seconds, in order to minimize system interference). By appropriate placement, such auxiliary units can be used to 15 reduce uncertainties at certain locations or generally increase the accuracy of position finding in strategic areas, such as major highways, malls, or central business districts. Because of the interference-limiting nature of a CDMA system, in some cases only one base station will be able to receive the 2 0 subscriber's signal, and vice-versa, so the auxiliary units are needed to obtain the necessary multiple readings.
The relative time of reception of each signal is determined by using information about the leading edge (or 2 5 alternately, the peaks) of related correlation peaks in the searcher, and adjusting this by an offset determined in a fine time alignment circuit (e.g., delay lock loops (DLLs) 215, 225 or 235 for each branch, coupled with filters 250-270).
Preferably related correlation peaks are those received on 30 different branches but within one chip of each other. In this ~ approach, the precise time of the leading edge is determined, along with the PN sequence number (i.e., the chip position (e.g., number 245) of the repeating PN sequence (e.g., app~uxi",dt~,ly 16,000 chips in length)). Using the already determined PN
35 sequence offset, and the system design where the base PN
WO 96/359~;8 : F~ 797 _ 2192~79 8 sequence is the same for each base station, and transmitted at the same system time plus or minus a unique PN sequence offset, the difference in re!àtive times yields a difference in propagation path delay. This is illustrated in FIG. 3. At time 5 T0 two bases B1 and B2 are lldns",itli"g, but base B1 transmits PN chip 0, while base B2 transmits PN chip 256 since it has a PN sequence offset of 256 chips. At some time T1, after location finding is activated, the subscriber determines that the leading edge of PN chip 4 from B1 has been 1 0 received. The next leading edge of a PN chip from base B2 is received 1/8th of a chip later at time T2, and the chip is determined to be the 280th in the PN sequence. From these receive times and PN numbers, the propagation delay difference is calculated to be ((PNB2 - offset) + (receive 1 5 difference, T2-T1)) - (PNB1 - offset) = ((261-256) + (1/8)) -(4-0) = 1 1/8 chips ~ 814 ns/chip = 916 ns. At applc,ki",dt~,ly 1/3 meter (m) per ns p,opayt.Lion speed for a radio signal, this translates into about 300 m difference in propagation path distances. The precision in location is only iimited by the 20 system clock rate being used and degree of sy"uhluni,dtion.
Where all base stations are using GPS timing inrum~alioll, synchronized transmissions (i.e., of the leading edges of chips) to within 50 ns (or approximately 1/16th of the chip rate) are currently possible. With a local clock generating at least the 25 same 20 MHz clock rate, location to within 100 ns or 30 m is possible .
Retuming to FIG. 2, DLLs 215, 225, and 235 are fed back to each rake 210, 220 and 230, respectively, for adjusting the 30 signals to output fine time aligned signals. As noted above, the DLL outputs can also serve as fine phase offset i"roll"dlion for adjusting the receive times of the PN chips, preferably after filtering in Low Pass Filters (LPFs) 250, 260, 270 for each channel, respectively, which effectively averages 35 the outputs of each DLL 215, 225, 235. This averaged fine -~WO 9G/35958 21 g 2 S 7 9 PCTNS96/03797 g r ~
phase offset information, together with the chip number/times/base identification or offset (i.e. B1-B3 information) from searcher 240 (which is also adapted for PN
chip/time detection), are fed to location searcher 280.
Location searcher 280 takes the fine phase offset information from each branch and corrects the time of reception from searcher 240 for each chip, to give a corrected relative time of reception for each branch. From the earliest time, say B1 (i.e., the time the signal from base 1 is received), the 1 0 difference tB21 and tB31 in reception time for the other signals B2 and B3 is determined, and the cor,e~,ol1ding distances dB21 and dB31 determined. One thus knows that the distance from bases 1 (110), 2 (120) and 3 (130) are dB1, (dB1 + dB21) and (dB1 + dB31), respectively. Further, from the PN
1 5 offsets, the identity of the bases are known and their geographic position can be retriev0d from memory 281. It is then a simple matter of performing a search routine to determine, one such as illustrated in FIG. 4, to determine the geographic coordinates of the mobile. In the example of FIG. 4, the known base locations are used to define three lines L12 (151), L23 (152) and L13 (153). The distances dB21 and dB31 are subtracted from lines L12 (151), L23 (152) and L23 (152), L13 (153) respectively, and the remaining segments bisected by normal lines N12 (154), N23 (156) and N13 (155). The intersection of these lines N12 (154), N23 (156) and N13 (155) is the position of the subscriber 140. This information could then be sent to the serving base station for forwarding to a requesting party of serving location register, or could be forwarded for use by the subscriber (e.g., on a map grid or 3 0 other location device, not shown).
Alternatively, if base site location information is not available to the subscriber, the phase offset, chip, timing and base offset information can be sent in a location request signal to a serving base station. There, a location searcher can WO 96/35958 ~ ?, ~ I PCT/I~S96/03797 ~
2 ~ n ~ 0 -S ~
access its own database and determine the subscriber location.
This location information is then transmitted back in a location response message to the subscriber or other requesting entity.
A preferred approach, however, for location using infrastructure equipment can be seen with reference now to FIG. 5, which generally depicts a block diagram of a CDMA
infrastructure system 300 having a first CDMA base station 10 301. Base 301 has a common RF front end 3û5 which feeds four independent rake inputs, shown as 310, 320, ... 330. These rakes can lock onto four different received rays that are at least one PN chip time apart, which is typical of a DSSS
receiver. The two searchers 340 scan for new correlation 15 peaks, and can reassign the rakes based on its best estimate of current channel conditions. Normally, the four correlators of rakes 310, 320, 330 lock onto the four strongest rays that are available.
2 0 When a location finding function is desired, two general approaches are av~ lr cither passive (i.e., no subscriber unit response) or active. In either case it is preferable to find at least three different base stations capable of receiving a subscriber signal, so that sufficient information is available to estimate the location. In a first en,l;~odi",e"l passive mode, four rake branches 310, 320 ... 330 of base 301 are used to detect an uplink signal. From each rake, a Delay Lock Loop (DLL) is used to generate an estimate of the timing (i.e., adjustment) of the correlated ray This more accurately 30 estimates the time of the correlation, similar to the process used by the subscriber unit above. Searcher and Chip/Time Detector 340 peak correlates the signal on each branch, and also determines the best branch to use (preferably based on the earliest received peak for the same chip, but other 35 selection techniques may be used to determine a current best ~WO 96~359~8 1 9 2 ~ 7g PCT~S96/03797 ., r~
branch); this best branch signal is used in determining PN chip and receive time information, similar to that in subscriber searcher 240.
To initiate a location process, in a preferred embodiment a command is initiated within the system 300, most likely at a regional entity such as a mobile switching center (MSC) 365, operations center, or perhaps within a connected network such as PSTN (public switched telephone network) 375. A location request is then plucessed via home location register (HLR) 366 to determine the currently serving base station(s). Upon receipt of a location command, plocessor 350 of base 301 (and similar processors of other serving bases) uses detector 340 to determine a chip receive time. Preferably this is accor", ' ~hed by all bases detel", li"g the leading edge rise time of a specified group of PN chips, for example by determining the rise time for each 64th chip (i.e., PN sequence number 0, 64, 128, etc.) for a pledetel", ,ed number of chips, e.g., 10. This information is then forwarded by each base 2 0 receiver, along with its iD (identification), to a designated entity, e.g. Iocation searcher 361 of BSC (base site controller) 360, or location searcher 367 of HLR 366, etc.. Thus, the difference in receive time for the same chips, each chip being derived from the same single chip ~l~ns",;ssiol1, may be used 25 to determine propagation delay differences. In other words, for each chip number the differential between receive times at the different bases yields a propagation difference, and location may be determining this information in conjunction with the known location of the receiving bases, in a similar 30 manner as described above with FIG. 4. By taking plural sets of information in a relatively short time frame (e.g., 10 times, every 64 chips, across about 500 ",;~ ,cseconds), and averaging ~ or otherwise best-fit calculating using the determined positions, position errors can be minimized. A skilled artisan 35 will appreciate that other approaches can be used in the actual W O 96135958 ~ ~ ~ ' PC~rrU596103797 ~
2 1 9 2 ~ 7 ~ - 1 2 -calculation. For example, a detection at the same system time(s) for leading edges within one chip of the desiy"ated time(s), along with time differences from the designated system time and chip number, could be used in determining the 5 propagation delay differences (albeit, an additional error may arise because the transmit time for the different chips is limited by the accuracy of the subscriber's clock rate; even if a 50 ns clock cycle were present, this is still more error than present from a transl";ssio" of the same chip (which has no 1 0 timing error). What is important is that the chip ID (e.g., number/position in the PN sequence) and precise time of reception (e.g., leading edge, or peak, at the oversampled clock rate) at different bases be used in determining the subscriber location .
In a preferred embodiment for active location, a two-way ranging system is implemented using both chip receive time information and certain response information from the subscriber. In this embodiment, the process is again initiated 20 with a location request in the system infrastructure, forwarded to base 301 which is in communication with the subscriber. Processor 350 forwards a location request signal (LOC_S 351) for app,upridl~ encoding by encoder 352 and spreading modulator 355. Using a system clock 353 25 (preferably GPS derived, but other precise means such as an atomic clock may be used), fine time adjuster 354 (e.g., a strobe generator) controls the modulator 355 to precisely output the leading edge of the output chips, preferably within 50ns accuracy. Processor 350 also determines via modulator 30 355 and clock 353 a precise system time for a reference chip (say, chip 1024 of a sequence of 16384 chips, at system time TS(0)), from which other chip tran ",ission times can later be determined. The output chip sequence is then transmitted to the subscriber.
~WO 96/3S958 ~ 2 ~ 7 ~ ~ f ~ - PCT/llS96103797 . ~
Referring once more to FIG. 2, following demodulation and receipt of the location request signal 351, processor 280 controls searcher 240 to determine ID and timing information for a next PN chip, in a similar manner as described above. For 5 purposes of illustration, let us say the determined chip is 1088 (of the base PN sequence) at subscriber relative time TR(0). In order to provide accurate ill~c,lll,dliol1 for turn around time within the subscriber, processor 280 then determines a local time at which a predetermined chip of the subscriber PN
10 sequence will next be l,~nsr"illed. For convenience, this predetermined chip is preferably selected as one of a repeating series (say every 50th chip of the subscriber's PN sequence) yet to be transmitted (say, chip 100); almost any other chip could be selected, e.g., the first chip for the next 20 ms frame, 15 but preferably with a view to minimizing subscriber precise-timing output requirements and system location processing. In any event, the selected chip's local time for output from modulator 291 of transmitter circuit 203 is determined, e.g., by determining a current chip's output time (e.g., via PN/Time 2 0 detector 292) and calculating forward to determine the predetermined chip's output time (say, chip 100 at TR(24 1/16), relative time here being measured in chip rate intervals). Of course, if no current ll~ns",issiol1 is in progress a sufficient delay time would be given (e.g., approximately 2 25 seconds) for the bases to train to the subscriber's PN sequence before transmission of the predetermined chip. The processor would then forward a location response signal RESP 282 for encoding by encoder 290, and would control modulator 291 to precisely output the predetermined chip at the determined 30 time (i.e., TR(24 1/16)), and, if a periodic group of chips is to ~ be monitored, to precisely output any subsequent chips of the periodic group (e.g., chips 150, 200, etc.) for a predetermined period. The RESP 282 would include the base chip information (1088, TR(0)), the predetermined chip information (100, TR(24 35 1/16), and, if not already known by the infrastructure as part WO 96135958 = PCTIIIS96/03797 2192a79 -1 4-of the subscriber unit profile, a predelt:r",;"ed (i.e., calibrated/calculated) subscriber delay factor for pre-acquisition and post-output delays (i.e., the time it takes a signal at the antenna to reach searcher 240, and for an output 5 signal to be radiated at the antenna following the time-precise output from modulator 291).
Returning to FIG. 5, at the same time the system controls base 301 to send the location request signal 351, it also 10 notifies the other communicating bases to begin storing location information. Where there are less than 3 bases in communication (i.e., soft-handoff) or capable of receiving the subscriber signal, the originating entity (e.g., location searchers/processors 361 or 367) will command one or more 15 auxiliary base stations, such as base 356, located in the vicinity of the serving bases to begin receiving at the subscriber's designated frequency. Thus, in the simplest imple-"enl~lion the auxiliary bases could be tunable receivers with a precise system clock (e.g., a GPS-corrected clock); if an 20 auxiliary base was not connected via wireline to a BSC, the auxiliary base could be implemented as fixed subscriber unit (such as a wireless access fixed unit (WAFU)), the only difference from a subscriber being that the WAFU would be operating at system time (e.g., via the GPS clock). In this 2 5 latter embodiment the WAFU would communicate its location response i"rur" ,ation via its own serving base station, e.g .
base 3û1.
All receiving bases, e.g., base 301 and auxiliary base 3 0 356, begin storing subscriber chip/time information upon initiation of the location request. The stored information could be the time (e.g., leading edge receive time) and chip number for each chip received for a predetermined period.
Rather than saving every chip, which in one 20 ms frame would 35 mean close to 25,000 entries, a periodic number of chips (e.g., ~lg2~79 ~ WO 96/35958 ; ~, PCTIUS96/03797 ~ ,~
every 50th chip in the sequence) is preferably used by all receiving bases; in this latter case the subscriber would be configured as ~iiscu~sed above so as to choose a predetermined chip that is one of these periodic chips (such as chip 100). A
skilled artisan will appreciate that any number of periods, or specific chips (e.g., the first chip of a frame) can be used, as long as information is being gathered on the same chip(s) at all bases in order to minimize error. Preferably, for convenience, an appropriately configured subscriber will select the 1 0 predetermined chip so as to coincide with the chip(s) being monitored for by the bases, thus simplifying later calculations; the selection could be based on preprogramming, or upon data in the location request signal 351 indicating the chip(s)/period to be monitored (in which case only the 1 5 predetermined chip(s) need be precisely outputted).
Upon receiving the spread RESP signal from the subscriber (preferably sent via in-band signaling with any ongoing voice/data communications), pl~,cesso,~ 350 and 358 of bases 301 and 356 detect the signal and predetermined chip information, and forward some predetermined number of chip/time pairs to location searcher 361 or 367. For example, to allow for averaging to improve accuracy, each base 301, 356 may forward 8 chip/time pairs, starting with the predetermined chip and its receive time (e.g., pairs 1100, TS(28 7/16)}, ~150, TS(78 7/16)}, ... {450, TS(378 8/16)}, along with the RESP signal information (e.g., the base chip/time pair {(base)1088, TR(O)}, the predetermined chip/time pair {(subscriber)100, TR(24 1/16)}, and known 3 0 delay factor {4/32}). A timeline illustrating this sequence is ~ shown in FIG. 6. TS(O) represents a starting system time, shown here as the 0th bit of the system clock for convenience, while TR(O) represents the subscriber's relative clock time.
PNB1 (1088) represents the 1088th chip in the first base 35 station's (301) PN sequence, while PNS(100) represents the W O 96/35958 2 1 9 2 5 7 9 PC~rrUS96/03797 ~
100th chip in the subscriber's PN sequence. Thus, base chip 1088 is outputted at system time 0, and radiated from the base antenna a transmit delay time ~tB1 later. After a propagation delay ~P1 and subscriber receive delay time ~rS
5 (i.e., from the subscriber antenna to detector 240) later, detector 240 determines chip 1088 to be received at TR(0).
Processor 280 then determines the next 50th chip of the subscriber sequence to be chip 100, and calculates from a current subscriber chip/time that the output time for chip 100 1 0 will be TR(24 1/16). Knowing the calibrated delays ~rS and ~tS (the delay from output to antenna radiation), say 2/32 chips each, the subscriber sends the RESP signal 282 including information, e.g., [{1088,TR(0)}, {100,TR(24 1 /16), {4/32}].
1 5 Base 301 detector 240 receives subscriber chip 100 at system time TS(28 7/16) and base 357 receives it at time TS(29 7/16), with propagation and receive (i.e., antenna to detector) delays of ~P2, ~rB1 and ~P3, ~rB2, respectively.
Similar repeat measurements are also performed, for example 20 base 301 receiving chip 150 at time TS(78 7/16), the subscriber having controlled the output time of chip 150 to TR(74 1/16), i.e., precisely 50 chips (40,700 ns) later.
After a pred~ ",il,ed number of pairs are determined, 2 5 the chip/time information and response signal information are forwarded to the location searcher 361 or 367. The searcher 361 or 367 then cAIclll~tRs the propagation delays, e.g., ~P1 -~P3, using the other known i"~ol",a~ion. In this case, let the calibrated base delays ~tB1, ~rB1 and ~rB2 be 5/32, 3/32 and 30 3132 chips. Because ~P1 is essentially the same as ~P2, then 2~P1 = (TS(28 7/16)-TS(0)) - (~tB1 + ~rB1) - (TR(24 1/16) -TR(0)) (~rS + ~tS) Eq.1 ~2~ l ~
W096/35958 PCT~S96/03797 - 17- ~ "
= (28 7/16) - (8/32) - (24 1/16) - (4132) = 4 chips Thus, ~P1 is 2 chips, or 1628 ns, and the propagation path length is about 488 m (+/- 30 m at 100 ns total uncertainty).
Once ~P1 is known, ~P3 can similarly be c~lc~ terl yielding in the illustrated case a time of 3 chips and distance of 733 m.
10 By calculating the propagation path length for at least three receivers, and retrieving the location information on the receiving bases (e.g., from ~l~t~h~.~e~ 362 or 368) the position of the subscriber may be determined by calculating the unique point (or small region of highest probability) at which the 15 respective propagation paths can all intersect. The process is repeated for each time/chip set. Each calculated point (or centroid of the probably region) is then used in determining the subscriber location, e.g. most simply by averaging, although any suitable process for fitting determining a most likely 20 point/region from multiple points/regions can be used. The location of the most likely poinVregion is preferably stored in the user profile database 369 of HLR 366. Additionally, the entire process can be repeated after one or more further periods of time, on the order of seconds or minutes, with the 25 plural most likely regions being used to determine a speed and direction of travel of the subscriber; if an accurate enough subscriber clock is being used so drift is under 50 ns for an extended period of multiple minutes (i.e., the subscriber clock's offset from the system time is known for that period), 30 repeated detections at the bases could be performed without the need to repeat the request signal). Finally, the determined location, and travel speed/direction, are forwarded to the ~ originally requesting entity, e.g. to operator 370 or via PSTN
375.
W096/35958 ~ PCT/US96/03797 ~
7 ~ - 1 8 -~ iJ V
A particular advantage of using the active location process over the inactive one is that, if desired, three-dimensional information can be more accurately determined.
This is particularly useful in urban or hilly areas, where the 5 angle of incline for the propagation paths can be significantly greater than 0 degrees from the horizon. While three dimensional coordinates of the bases, and known topography of a first approximation subscriber location, can be used to increase the accuracy of the passive process, a skilled artisan 10 will appreciate that a better approximation can be derived from the measured propagation time, as opposed to just differences in propagation times. Because the determined propagation paths are as accurate in three dimensions, it is just a matter of additional processing of the z-axis (i.e., third 15 dimension) coordinates of the base site locations, along with their x- and y-axis coordinates, to determine the three-dimensional region of probable location. If this is compared against known building and topographical information, location to within +/- 8 stories (at 100 ns uncertainty) or better in a 2 0 single building is may be possible. Additional information, such as relative received signal strengths and likely path loss characteristics into a building, could be used to further narrow the region of probable location.
2 5 FIG. 7, generally designated as 400, is an illustrative flow chart of the system process for a subscriber measuring base station signals to obtain a location estimate. The process is started in block 405, which represents the occurrence of a location command to be performed by the subscriber (e.g., by subscriber initiation, or automatically based on other indicator such as a motion sensor indicating a vehicle crash). Block 410 checks the status of the subscriber and a decision is made 415 based on whether or not the subscriber is in 3-way soft handoff. If it is not, block 420 is executed which tests to see if there are three bases in the 2192~79 ~WO 96/359~8 PCT/I~S96/03797 -19- ~ ~ ~
.~ .
candidate set. If not, decision block 425 is tested to check the threshold of adding bases to the candidate set. If this is not at the minimum, block 430 reduces the threshold and returns to process step 420. If block 425 is at a minimum level already, block 450 is executed. This block differentiates the location function between an emergency and non-emergency function.
Thus, if a non-emergency function is being processed, system level changes are permitted only when the level of use is not high, since this could result in users loosing service by raising 1 0 the interference level. In a non-emergency at high system loading, block 460 is executed. If an emergency is indicated, block 455 is executed before block 460. This occurs preferably in response to an emergency beacon signal to which the auxiliary pilot generators are tuned, and will 1 5 automatically respond to; alternatively, an emergency signal can be sent to a serving base and l~r-Jcessed to control the auxiliary bases to activate. In the latter case, a second non-emergency request signal could be similarly used, with an activation command being generated if the control processor (e.g., processor/searcher 361 of BSC 360 in FIG. 5) indicates system loading is beneath a loading threshold. Block 455 thus activates nearby pilot generators that provide more complete coverage of the service area by multiple sites, allowing the subscriber to receive a signal from multiple bases. Block 460 2 5 tests to see if the subscriber is in 3-way soft handoff. If not, the subscriber is instructed 465 to form a 3-way soft handoff condition using the largest rays from at least three base stations. If the result of 460 was positive, or block 465 was completed, block 440 is executed and the collection of data is made as described above in connection with FIG. 2. This data is used to process the location estimate (e.g., in searcher 280 using additional data from memory 281 of FIG. 2), and the system is returned to nominal conditions 445.
WO96/35958 P~ /03797~
219257~ -20-Returning to block 415, if the subscriber is in 3-way handoff, block 440 is executed. Returning to block 420, if there are three bases in the candidate set, block 435 is executed, which places three different bases in the active set.
5 Then block 440 is executed, as described earlier, followed by block 445.
FIG. 8, generally designated as 500, is an illustrative flow chart of the process for the base stations measuring the 1 0 subscriber unit to obtain a location estimate. The process starts in block 505 when the location function is activated.
Block 510 checks the status of the subscriber and a decision is made 515 based on whether or not the subscriber is in 3-way soft handoff. If it is not, block 520 is optionally executed, 1 5 which tests to see if there are three bases in the candidate set. If not, decision block 525 is tested to check the threshold of adding bases to the candidate set. If this is not at the minimum, block 530 reduces the threshold and returns to process step 520. If block 525 is at a minimum level already, 2 0 block 535 is executed, which will continue the prucessi"g of the location e~li",dlion, but now with only two bases, which is less accurate than the desired case of having three bases in the measurements. Returning to block 515, if the subscriber is in 3-way soft handoff, or block 520 if three bases are in the 25 candidate set, then block 540 is executed. Block 540 insures that the three base stations are active for receiving the subscriber's signal. Then block 545 is optionally execllt.orl This biock tests to see if each base can receive the subscriber.
If each base can, block 550 is executed which sends a location 30 request signal if in active mode, and in both modes collects the available data and processes the location estimate in the manner described above. Block 555 follows returning all parameters to normal and the measurements are complete.
Returning to block 545, if less than three bases can receive 3 5 the subscriber, block 546 tests to see if auxiliary base units ~WO 96135958 ~ ) 7 9 PCT/US96103797 are available. If so, the local auxiliary sites are activated in block 547, and block 560 tests to see if an emergency is indicated. If not, only the bases that are received can be used in the measurements, and this can degrade the quality of the 5 estimate. If an emergency is indicated (e.g., by a subscriber signal such as the dialed digits 911, or emergency request from an authorized entity connected to the infrastructure), block 565 is executed to test if the subscriber unit is at maximum power. If not, block 570 is executed to increase the 1 0 power and the process returns to block 540. If block 565 is at maximum power, block 575 tests to see if each base can receive the subscriber. If so, block 550 is executed; otherwise the cell loading is reduced by block 580 to increase the effective range of the cells in the active set that are having 1 5 difficulty receiving the subscriber unit. Then block 585 tests to see if the load shedding limit has been reached, and if so, block 550 is executed; otherwise, decision block 575 is executed again to test to see if each base can now receive the subscriber.
Thus, it will be apparent to one skilled in the art that there has been provided in accordance with the invention, a method and apparatus for estimating the location of a subscriber unit of a wireless communication system that fully 2 5 satisfies the objectives, aims, and advantages set forth above.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to 30 those skilled in the art in light of the foregoing description.
~ For example, while the searchers 240 and 280 of the subscriber unit 200 and searcher 340 and processor 350, and ~ other circuits, of the base station 301 are described in terms of specific logical/functional circuitry relationships, one 35 skilled in the art will appreciate that such may be embodied in W096/35958 ~ PCT/IJS96/03797 ~
a variety of ways, such as appropriately configured and programmed processors, ASlCs (application specific integrated circuits), and DSPs (digital signal plucessol:,). Further, the invention is not limited to determining location via chip 5 information in an IS-95 CDMA system, but has applicability to any CDMA system using spreading symbol sequences. Thus, it should be understood that the invention may include in a first embodiment of active searching: a method and apparatus operable for determining the location of a subscriber unit in a 10 CDMA wireless communication system having plural base stations, col"prisi"g: (a) sending a first spread spectrum signal including a location request from a first base station of the plural base stations to the subscriber unit, the spread spectrum signal being spread by a known first sequence of 15 spreading symbols; (b) receiving at the first base station a second spread spectrum signal including a response message from the subscriber unit, the second spread spectrum signal being spread by a known second sequence of spreading symbols, and the response message ~;OIIl~lib;llSl a receive time of a first 20 symbol of the first sequence and a transmit time of a first symbol of the second sequence; (c) receiving a predetermined symbol of the second sequence at the first base station and at least a second base station, and determining a first and a second receive time of the predetermined symbol at the first 25 and second base station, respectively; and (d) determining a location of the subscriber unit from the receive time of the first symbol of the first sequence by the subscriber unit, the transmit time of the first symbol of the second sequence by the subscriber unit, the first and second receive times of the 30 predetermined symbol, and known information about the first and at least second base stations. A further ~",bo.lh"er,l may include: a method and apparatus operable for determining a subscriber location in a CDMA communication system having plural base stations, comprising: (a) receiving a signal from 35 the subscriber at each of a first base station, a second base . 21g2379 W O 96135958 PC~rrUS96/03797 - 2 3 - , . .
station and a third base station, the signal being formed via modulation by a known sequence of spreading symbols; (b) determining a first receive time of a symbol of the known sequence of spreading symbols at the first base station, a 5 second receive time of the symbol at the second base station, and a third receive time of the symbol at the third base station; and (c) determining the location of the subscriber unit in a location processor from the first, second and third receive times and further known information about the first, second 10 and third base stations. In yet another embodiment there is: a subscriber unit operable for determining its own location while communicating in a CDMA wireless communication system having plural base stations, the subscriber unit comprising: (a) receiver means for receiving a first signal 15 from a first base station of the plural base stations and a second signal from a second base station of the plural base stations, the first and second signals being formed via modulation by a known first sequence of spreading symbols and a known second sequence of spreading symbols, respectively;
2 0 (b) detector means for determining a first receive time of a first symbol of the first sequence, and a second receive time of a further symbol of the second sequence; and (c) location processor means for determining the location of the subscriber unit from the first and second receive times and further known 25 information about the first and second base stations. A yet further emboiment includes: a method for determining a location of a subscriber in a CDMA communication system having plural base units including active base stations and inactive units, comprising: (a) receiving a signal indicative of 3 0 an emergency; (b) determining if at least three of the active base stations can receive a signal from the subscriber, and if not, activating at least one of the inactive units as an auxiliary base station; (c) controlling a group consisting of at least three of the active base stations which can receive a 3 5 signal from the subscriber, and any auxiliary base stations 2192~7~ -24-activated in step (b), to each transmit a spread spectrum signal having a same symbol sequence; (d) clel~n~ .,g each receive time at the subscriber of a same symbol of the symbol sequence for each spread spectrum signal transmitted in step 5 (c), respectively, and sending a response from the subscriber including said each receive time; and (d) determining the location of the subscriber from said each receive time and further known information about the group.
Accold;,l~Jly, it is intended that the invention not be limited by the foregoing description of embodiments, but to embrace all such alterations, modifications, and variations in accordance with the spirit and scope of the appended claims.
15 We claim:
Claims (10)
1. A method for determining the location of a subscriber unit in a wireless communication system, the method comprising the steps of:
sending a first signal including a location request from a first base station to the subscriber unit;
receiving a second signal including a response message from the subscriber unit, the response message comprising a receive time of the first signal and a transmit time of the second signal;
receiving a predetermined symbol associated with the second signal at the first base station and a second base station, and determining a first and a second receive time of the predetermined symbol at the first and second base station, respectively; and determining a location of the subscriber unit from the receive time of the first signal by the subscriber unit, the transmit time of the second signal by the subscriber unit, the first and second receive times of the predetermined symbol, and from predetermined information about the first and second base stations.
sending a first signal including a location request from a first base station to the subscriber unit;
receiving a second signal including a response message from the subscriber unit, the response message comprising a receive time of the first signal and a transmit time of the second signal;
receiving a predetermined symbol associated with the second signal at the first base station and a second base station, and determining a first and a second receive time of the predetermined symbol at the first and second base station, respectively; and determining a location of the subscriber unit from the receive time of the first signal by the subscriber unit, the transmit time of the second signal by the subscriber unit, the first and second receive times of the predetermined symbol, and from predetermined information about the first and second base stations.
2. The method of claim 1, wherein said predetermined information comprises location and processing delay information.
3. A wireless communication system for locating a communication unit, the wireless communication system comprising:
(a) a first base station comprising:
(i) a first base station transmitter sending a first spread spectrum signal including a location request to the communication unit;
(ii) a first base station receiver receiving a second spread spectrum signal including a response message from the communication unit, the response message including a receive time of the first signal and a transmit time of the signal, the first base station receiver further comprising a first base station detector receiving a predetermined symbol of the second signal from the communication unit and determining a receive time of the predetermined symbol;
(b) a second base station comprising a second receiver for receiving the predetermined symbol of the second signal and determining a second receive time of the predetermined symbol; and (c) a controller responsive to the first and second base stations, the controller comprising means for determining a location of the communication unit from the receive time of the first signal, the transmit time of the first signal, the first and second receive times of the predetermined symbol, and predetermined information about the first and second base stations.
(a) a first base station comprising:
(i) a first base station transmitter sending a first spread spectrum signal including a location request to the communication unit;
(ii) a first base station receiver receiving a second spread spectrum signal including a response message from the communication unit, the response message including a receive time of the first signal and a transmit time of the signal, the first base station receiver further comprising a first base station detector receiving a predetermined symbol of the second signal from the communication unit and determining a receive time of the predetermined symbol;
(b) a second base station comprising a second receiver for receiving the predetermined symbol of the second signal and determining a second receive time of the predetermined symbol; and (c) a controller responsive to the first and second base stations, the controller comprising means for determining a location of the communication unit from the receive time of the first signal, the transmit time of the first signal, the first and second receive times of the predetermined symbol, and predetermined information about the first and second base stations.
4. A method for determining a subscriber unit location in a communication system, the method comprising the steps of:
(a) receiving a signal from the subscriber unit at a first base station and at a second base station, the signal being formed via modulation by a sequence of spreading symbols;
(b) determining a first receive time of a symbol of the sequence of spreading symbols at the first base station, (c) determining a second receive time of the symbol at the second base station; and (d) determining the location of the subscriber unit from the first and second receive times and further predetermined information about the first and second base stations.
(a) receiving a signal from the subscriber unit at a first base station and at a second base station, the signal being formed via modulation by a sequence of spreading symbols;
(b) determining a first receive time of a symbol of the sequence of spreading symbols at the first base station, (c) determining a second receive time of the symbol at the second base station; and (d) determining the location of the subscriber unit from the first and second receive times and further predetermined information about the first and second base stations.
5. A communication system having plural base stations and operable for locating a communication unit, the communication system comprising:
a controller responsive to a first and a second base station, each of the first and second base stations comprising a receiver operable for receiving a signal from the communication unit, the signal being formed via modulation by a sequence of spreading symbols, and a detector operable for determining a receive time of a symbol of the sequence; and a location processor responsive to the controller operable for requesting the first and second base stations to determine first and second receive times of a particular symbol of the sequence, and for determining a location of the communication unit from the first and second receive times and further information about the first and second base stations.
a controller responsive to a first and a second base station, each of the first and second base stations comprising a receiver operable for receiving a signal from the communication unit, the signal being formed via modulation by a sequence of spreading symbols, and a detector operable for determining a receive time of a symbol of the sequence; and a location processor responsive to the controller operable for requesting the first and second base stations to determine first and second receive times of a particular symbol of the sequence, and for determining a location of the communication unit from the first and second receive times and further information about the first and second base stations.
6. A method for determining the location of a subscriber unit communicating in a wireless communication system having plural base stations, comprising, in the subscriber unit:
(a) receiving a first signal from a first base station of the plural base stations and a second signal from a second base station of the plural base stations, the first and second signals being formed based on a first sequence of symbols and a second sequence of symbols, respectively;
(b) determining a first receive time of a first symbol of the first sequence, and a second receive time of a further symbol of the second sequence; and (c) determining the location of the subscriber unit from the first and second receive times and further information about the first and second base stations.
(a) receiving a first signal from a first base station of the plural base stations and a second signal from a second base station of the plural base stations, the first and second signals being formed based on a first sequence of symbols and a second sequence of symbols, respectively;
(b) determining a first receive time of a first symbol of the first sequence, and a second receive time of a further symbol of the second sequence; and (c) determining the location of the subscriber unit from the first and second receive times and further information about the first and second base stations.
7. The method of claim 6, wherein the first and second sequences are identical sequences of spreading symbols having first and second sequence offsets of a first and a second predetermined number of symbols, respectively.
8. A method for determining a location of a subscriber in a communication system having plural base units including active base stations and inactive units, the method comprising the steps of:
activating at least one of the inactive units as an auxiliary base station;
controlling a group comprising at least one of the active base stations which can receive a signal from the subscriber and any auxiliary base stations activated, to each transmit a signal; and determining the location of the subscriber based on each of said signals.
activating at least one of the inactive units as an auxiliary base station;
controlling a group comprising at least one of the active base stations which can receive a signal from the subscriber and any auxiliary base stations activated, to each transmit a signal; and determining the location of the subscriber based on each of said signals.
9. The method of claim 8, further comprising the step of determining a receive time at the subscriber for each of said signals.
10. An apparatus for determining a location of a subscriber in a communication system having plural base units including active base stations and inactive units, the apparatus comprising:
means for activating at least one of the inactive units as an auxiliary base station;
means for controlling a group comprising at least one of the active base stations which can receive a signal from the subscriber and any auxiliary base stations activated, to each transmit a signal; and means for determining the location of the subscriber based on each of said signals.
means for activating at least one of the inactive units as an auxiliary base station;
means for controlling a group comprising at least one of the active base stations which can receive a signal from the subscriber and any auxiliary base stations activated, to each transmit a signal; and means for determining the location of the subscriber based on each of said signals.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/436,760 US5508708A (en) | 1995-05-08 | 1995-05-08 | Method and apparatus for location finding in a CDMA system |
US08/436,760 | 1995-05-08 | ||
PCT/US1996/003797 WO1996035958A1 (en) | 1995-05-08 | 1996-03-21 | Method and apparatus for location finding in a cdma system |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2192579A1 CA2192579A1 (en) | 1996-11-14 |
CA2192579C true CA2192579C (en) | 1999-09-07 |
Family
ID=23733723
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002192579A Expired - Lifetime CA2192579C (en) | 1995-05-08 | 1996-03-21 | Method and apparatus for location finding in a cdma system |
Country Status (15)
Country | Link |
---|---|
US (3) | US5508708A (en) |
JP (1) | JP3254682B2 (en) |
KR (1) | KR100208647B1 (en) |
CN (1) | CN1097734C (en) |
BR (1) | BR9606340A (en) |
CA (1) | CA2192579C (en) |
FI (1) | FI115886B (en) |
FR (1) | FR2734108B1 (en) |
GB (1) | GB2304500B (en) |
IL (1) | IL117654A (en) |
IT (1) | IT1284380B1 (en) |
PL (1) | PL180276B1 (en) |
RU (1) | RU2127963C1 (en) |
SE (1) | SE517676C2 (en) |
WO (1) | WO1996035958A1 (en) |
Families Citing this family (284)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5519760A (en) | 1994-06-22 | 1996-05-21 | Gte Laboratories Incorporated | Cellular network-based location system |
WO1996039781A1 (en) * | 1995-06-06 | 1996-12-12 | Flash Comm, Inc. | Determining propagating and clear frequency in wireless data communications network |
US5765112A (en) | 1995-06-06 | 1998-06-09 | Flash Comm. Inc. | Low cost wide area network for data communication using outbound message specifying inbound message time and frequency |
US5734963A (en) | 1995-06-06 | 1998-03-31 | Flash Comm, Inc. | Remote initiated messaging apparatus and method in a two way wireless data communications network |
US6885652B1 (en) | 1995-06-30 | 2005-04-26 | Interdigital Technology Corporation | Code division multiple access (CDMA) communication system |
US7020111B2 (en) | 1996-06-27 | 2006-03-28 | Interdigital Technology Corporation | System for using rapid acquisition spreading codes for spread-spectrum communications |
US7072380B2 (en) * | 1995-06-30 | 2006-07-04 | Interdigital Technology Corporation | Apparatus for initial power control for spread-spectrum communications |
US7929498B2 (en) | 1995-06-30 | 2011-04-19 | Interdigital Technology Corporation | Adaptive forward power control and adaptive reverse power control for spread-spectrum communications |
ZA965340B (en) | 1995-06-30 | 1997-01-27 | Interdigital Tech Corp | Code division multiple access (cdma) communication system |
FI101445B (en) * | 1995-10-03 | 1998-06-15 | Nokia Mobile Phones Ltd | Mobile location system |
JPH09163441A (en) * | 1995-12-06 | 1997-06-20 | Sony Corp | Portable telephone set and network for the same |
JPH09261128A (en) * | 1996-03-22 | 1997-10-03 | Matsushita Electric Ind Co Ltd | Spread spectrum communication equipment |
EP0800319A1 (en) * | 1996-04-02 | 1997-10-08 | Hewlett-Packard Company | Locating method for mobile radio systems |
GB2355159B (en) * | 1996-06-06 | 2001-06-13 | Qualcomm Inc | Determining the position of a mobile station in a CDMA cellular telephone system |
US6034635A (en) * | 1996-06-06 | 2000-03-07 | Gilhousen; Klein S. | Method for using only two base stations for determining the position of a mobile subscriber in a CDMA cellular telephone system |
GB2330488B (en) * | 1996-06-06 | 2001-03-07 | Qualcomm Inc | Using a signal with increased power for determining the position of a mobile subscriber in a CDMA cellular telephone system |
GB2357223B (en) * | 1996-06-06 | 2001-08-15 | Qualcomm Inc | Determining the position of a mobile station in a cellular telephone system |
US6195046B1 (en) * | 1996-06-06 | 2001-02-27 | Klein S. Gilhousen | Base station with slave antenna for determining the position of a mobile subscriber in a CDMA cellular telephone system |
US5943014A (en) * | 1996-06-06 | 1999-08-24 | Qualcom Incorporated | Using a signal with increased power for determining the position of a mobile subscriber in a CDMA cellular telephone system |
US5926761A (en) * | 1996-06-11 | 1999-07-20 | Motorola, Inc. | Method and apparatus for mitigating the effects of interference in a wireless communication system |
US5675344A (en) * | 1996-06-28 | 1997-10-07 | Motorola, Inc. | Method and apparatus for locating a mobile station in a spread spectrum communication system |
US5945948A (en) * | 1996-09-03 | 1999-08-31 | Motorola, Inc. | Method and apparatus for location finding in a communication system |
US9134398B2 (en) | 1996-09-09 | 2015-09-15 | Tracbeam Llc | Wireless location using network centric location estimators |
US6249252B1 (en) | 1996-09-09 | 2001-06-19 | Tracbeam Llc | Wireless location using multiple location estimators |
US6236365B1 (en) | 1996-09-09 | 2001-05-22 | Tracbeam, Llc | Location of a mobile station using a plurality of commercial wireless infrastructures |
US7903029B2 (en) | 1996-09-09 | 2011-03-08 | Tracbeam Llc | Wireless location routing applications and architecture therefor |
US7714778B2 (en) | 1997-08-20 | 2010-05-11 | Tracbeam Llc | Wireless location gateway and applications therefor |
CA2265875C (en) * | 1996-09-09 | 2007-01-16 | Dennis Jay Dupray | Location of a mobile station |
KR19980021532A (en) * | 1996-09-17 | 1998-06-25 | 유기범 | How to locate MS location in CDM personal mobile communication |
US5748084A (en) * | 1996-11-18 | 1998-05-05 | Isikoff; Jeremy M. | Device security system |
JPH10173630A (en) * | 1996-12-13 | 1998-06-26 | Nec Corp | Cdma chip-synchronizing circuit |
US6785550B1 (en) * | 2000-11-28 | 2004-08-31 | Lucent Technologies Inc. | Mobile location estimation in a wireless communication system |
US6163696A (en) * | 1996-12-31 | 2000-12-19 | Lucent Technologies Inc. | Mobile location estimation in a wireless communication system |
JPH10200506A (en) * | 1997-01-06 | 1998-07-31 | Sony Corp | Receiver, receiving method and terminal in radio system |
JPH10200505A (en) * | 1997-01-06 | 1998-07-31 | Sony Corp | Receiver, reception method and terminal equipment for radio system |
US5945949A (en) * | 1997-01-13 | 1999-08-31 | Lucent Technologies Inc. | Mobile station position determination in a wireless communication system |
JPH10200508A (en) * | 1997-01-14 | 1998-07-31 | Sony Corp | Terminal equipment for radio system and search method |
US5963866A (en) * | 1997-01-15 | 1999-10-05 | Lucent Technologies Inc. | Wireless location messaging |
KR100206310B1 (en) * | 1997-01-17 | 1999-07-01 | 윤종용 | Method and apparatus for system time broadcating and status/alarm management of gpsr |
JPH10209919A (en) * | 1997-01-21 | 1998-08-07 | Sony Corp | Equipment, method for reception and terminal equipment for portable telephone system |
US5903844A (en) * | 1997-02-04 | 1999-05-11 | Motorola, Inc. | Method and apparatus for determining remote unit location in a communication system |
US5905961A (en) * | 1997-02-05 | 1999-05-18 | Motorola, Inc. | Method and apparatus for managing remote unit increased power transmission during location |
US6148219A (en) * | 1997-02-18 | 2000-11-14 | Itt Manufacturing Enterprises, Inc. | Positioning system for CDMA/PCS communications system |
US6148195A (en) * | 1997-02-18 | 2000-11-14 | Itt Manufacturing Enterprises, Inc. | Phase agile antenna for use in position determination |
US6154656A (en) * | 1997-02-27 | 2000-11-28 | Ericsson Inc. | Wireless communication device and system incorporating location-determining means |
US6898197B1 (en) * | 1997-02-28 | 2005-05-24 | Interdigital Technology Corporation | Geolocation of a mobile terminal in a CDMA communication system |
US5943331A (en) * | 1997-02-28 | 1999-08-24 | Interdigital Technology Corporation | Orthogonal code synchronization system and method for spread spectrum CDMA communications |
US6091948A (en) * | 1997-02-28 | 2000-07-18 | Oki Telecom, Inc. | One number service using mobile assisted call forwarding facilities |
DE69824064T2 (en) | 1997-03-14 | 2005-06-23 | Ntt Mobile Communications Network Inc. | Position estimation of a mobile station for a cellular mobile communication system |
US6233459B1 (en) | 1997-04-10 | 2001-05-15 | The Atlantis Company, Limited, Japan | System for providing Geolocation of a mobile transceiver |
US5973643A (en) * | 1997-04-11 | 1999-10-26 | Corsair Communications, Inc. | Method and apparatus for mobile emitter location |
US5842130A (en) * | 1997-05-29 | 1998-11-24 | Motorola, Inc. | Method for identifying a mobile unit in a wireless communication system |
US6023607A (en) * | 1997-05-30 | 2000-02-08 | Nokia Telecommunication Oy | Radio system and a call setup method |
US6167274A (en) * | 1997-06-03 | 2000-12-26 | At&T Wireless Svcs. Inc. | Method for locating a mobile station |
US6118977A (en) | 1997-09-11 | 2000-09-12 | Lucent Technologies, Inc. | Telecommunications-assisted satellite positioning system |
US6011974A (en) * | 1997-09-23 | 2000-01-04 | Telefonaktiebolaget L M Ericsson (Publ) | Method and system for determining position of a cellular mobile terminal |
US6097958A (en) * | 1997-10-10 | 2000-08-01 | Northern Telecom Limited | Method and apparatus for locating and tracking cellular telephones in a CDMA cellular communication network |
US6157842A (en) * | 1997-10-16 | 2000-12-05 | Telefonaktiebolaget Lm Ericsson | System and method for positioning a mobile station in a CDMA cellular system |
FI974153A (en) | 1997-11-06 | 1999-05-07 | Nokia Mobile Phones Ltd | Procedure and arrangement for determining the location of a mobile station |
US6006097A (en) * | 1997-11-24 | 1999-12-21 | Telefonaktiebolaget L M Ericsson (Publ) | Method for determining position of mobile communication terminals |
US6195342B1 (en) | 1997-11-25 | 2001-02-27 | Motorola, Inc. | Method for determining hand-off candidates in a neighbor set in a CDMA communication system |
US5999522A (en) * | 1997-11-26 | 1999-12-07 | Motorola, Inc. | Method and apparatus for determining hand-off candidates in a communication system |
US6134228A (en) * | 1997-12-12 | 2000-10-17 | Telefonaktiebolaget Lm Ericsson (Publ) | Method and system for determining the position of a mobile terminal in a CDMA mobile communications system |
US6507741B1 (en) * | 1997-12-17 | 2003-01-14 | Nortel Networks Limited | RF Repeater with delay to improve hard handoff performance |
KR100290926B1 (en) * | 1997-12-27 | 2001-07-12 | 서평원 | Method of tracing location of mobile subscriber |
US6038438A (en) * | 1997-12-30 | 2000-03-14 | Ericsson, Inc. | Emergency radio beacon capable mobile communication system mobile telephone and method |
US6175587B1 (en) * | 1997-12-30 | 2001-01-16 | Motorola, Inc. | Communication device and method for interference suppression in a DS-CDMA system |
US6097959A (en) * | 1998-01-29 | 2000-08-01 | Ericsson Inc. | System and method for accurate positioning of mobile terminals |
US6603751B1 (en) | 1998-02-13 | 2003-08-05 | Qualcomm Incorporated | Method and system for performing a handoff in a wireless communication system, such as a hard handoff |
JP3436879B2 (en) | 1998-03-05 | 2003-08-18 | 松下電器産業株式会社 | Distance detecting method and device |
JPH11353257A (en) * | 1998-03-12 | 1999-12-24 | Sun Microsyst Inc | Detection system and method of location of user accessing computer application |
US6009091A (en) * | 1998-03-13 | 1999-12-28 | Motorola, Inc. | Method and apparatus for mobile station location within a communication system |
US6226317B1 (en) * | 1998-03-30 | 2001-05-01 | Motorola, Inc. | Method and system for aiding in the location of a subscriber unit in a spread spectrum communication system |
US6188888B1 (en) | 1998-03-30 | 2001-02-13 | Oki Telecom, Inc. | Charging unit and wireless telephone having multi-number call forwarding capability |
KR100293934B1 (en) * | 1998-04-13 | 2001-07-12 | 윤종용 | Apparatus and method for transmitting message using common channel in cdma system |
US6014102A (en) * | 1998-04-17 | 2000-01-11 | Motorola, Inc. | Method and apparatus for calibrating location finding equipment within a communication system |
US5999124A (en) * | 1998-04-22 | 1999-12-07 | Snaptrack, Inc, | Satellite positioning system augmentation with wireless communication signals |
FI107219B (en) * | 1998-05-04 | 2001-06-15 | Nokia Networks Oy | Procedure for measuring timing of signals and radio systems |
US20030194033A1 (en) | 1998-05-21 | 2003-10-16 | Tiedemann Edward G. | Method and apparatus for coordinating transmission of short messages with hard handoff searches in a wireless communications system |
US6799046B1 (en) | 1998-06-10 | 2004-09-28 | Nortel Networks Limited | Method and system for locating a mobile telephone within a mobile telephone communication network |
US5969679A (en) * | 1998-06-30 | 1999-10-19 | Lucent Technologies Inc. | Method and apparatus for determining whether a wireless station is operating within a prescribed geographic region |
KR100413418B1 (en) | 1998-07-10 | 2004-02-14 | 엘지전자 주식회사 | Separated Soft Handoff Control Method of Reverse Link |
US6330452B1 (en) | 1998-08-06 | 2001-12-11 | Cell-Loc Inc. | Network-based wireless location system to position AMPs (FDMA) cellular telephones, part I |
RU2225079C2 (en) * | 1998-08-07 | 2004-02-27 | Телефонактиеболагет Лм Эрикссон (Пабл) | Improvements in measuring time difference observed in downlink |
US6490454B1 (en) | 1998-08-07 | 2002-12-03 | Telefonaktiebolaget Lm Ericsson (Publ) | Downlink observed time difference measurements |
US6665332B1 (en) | 1998-09-09 | 2003-12-16 | Allen Telecom, Inc. | CDMA geolocation system |
DE19844296A1 (en) * | 1998-09-18 | 2000-03-23 | Biotronik Mess & Therapieg | Arrangement for patient monitoring |
US6269246B1 (en) | 1998-09-22 | 2001-07-31 | Ppm, Inc. | Location determination using RF fingerprinting |
US6393294B1 (en) * | 1998-09-22 | 2002-05-21 | Polaris Wireless, Inc. | Location determination using RF fingerprinting |
US6208297B1 (en) | 1998-10-09 | 2001-03-27 | Cell-Loc Inc. | Methods and apparatus to position a mobile receiver using downlink signals, part I |
US6204812B1 (en) | 1998-10-09 | 2001-03-20 | Cell-Loc Inc. | Methods and apparatus to position a mobile receiver using downlink signals, part II |
US6266014B1 (en) | 1998-10-09 | 2001-07-24 | Cell-Loc Inc. | Methods and apparatus to position a mobile receiver using downlink signals part IV |
US20030146871A1 (en) * | 1998-11-24 | 2003-08-07 | Tracbeam Llc | Wireless location using signal direction and time difference of arrival |
US8135413B2 (en) | 1998-11-24 | 2012-03-13 | Tracbeam Llc | Platform and applications for wireless location and other complex services |
KR100378124B1 (en) * | 1998-12-10 | 2003-06-19 | 삼성전자주식회사 | Device and method for estimating the position of terminal in mobile communication system |
US7089000B1 (en) | 1999-03-18 | 2006-08-08 | The Directv Group, Inc. | Multi-node wireless communication system with multiple transponding platforms |
US6785553B2 (en) | 1998-12-10 | 2004-08-31 | The Directv Group, Inc. | Position location of multiple transponding platforms and users using two-way ranging as a calibration reference for GPS |
US6337980B1 (en) | 1999-03-18 | 2002-01-08 | Hughes Electronics Corporation | Multiple satellite mobile communications method and apparatus for hand-held terminals |
KR100487243B1 (en) * | 1998-12-17 | 2005-08-31 | 삼성전자주식회사 | Device and method for estimating the position of terminal in mobile communication system |
US6587446B2 (en) | 1999-02-11 | 2003-07-01 | Qualcomm Incorporated | Handoff in a wireless communication system |
US7215954B1 (en) | 1999-03-18 | 2007-05-08 | The Directv Group, Inc. | Resource allocation method for multi-platform communication system |
US6920309B1 (en) | 1999-03-18 | 2005-07-19 | The Directv Group, Inc. | User positioning technique for multi-platform communication system |
US6603800B1 (en) * | 1999-03-22 | 2003-08-05 | Interdigital Technology Corporation | CDMA location |
US6242167B1 (en) | 1999-04-12 | 2001-06-05 | Rentech, Inc. | Developer for use with carbonless copy paper and photo imaging systems |
GB9908944D0 (en) * | 1999-04-19 | 1999-06-16 | Nokia Telecommunications Oy | Method and system for locating a station in a wireless network |
US6397074B1 (en) * | 1999-05-07 | 2002-05-28 | Nokia Mobile Phones Limited | GPS assistance data delivery method and system |
JP2001061176A (en) * | 1999-08-20 | 2001-03-06 | Pioneer Electronic Corp | Communication system |
JP3595738B2 (en) * | 1999-08-30 | 2004-12-02 | 松下電器産業株式会社 | Distance detecting method, position detecting method and device therefor |
EP1286735A1 (en) | 1999-09-24 | 2003-03-05 | Dennis Jay Dupray | Geographically constrained network services |
US6275707B1 (en) * | 1999-10-08 | 2001-08-14 | Motorola, Inc. | Method and apparatus for assigning location estimates from a first transceiver to a second transceiver |
US6677895B1 (en) | 1999-11-16 | 2004-01-13 | Harris Corporation | System and method for determining the location of a transmitting mobile unit |
US6405047B1 (en) * | 1999-12-01 | 2002-06-11 | Samsung Electronics, Co., Ltd. | Device and method for tracking mobile station's position in mobile communication system |
DE19961516A1 (en) | 1999-12-20 | 2001-07-05 | Siemens Ag | Method for controlling connection forwarding in a radio communication system |
US6404388B1 (en) | 2000-01-21 | 2002-06-11 | At&T Wireless Services, Inc. | Method and apparatus for enhanced 911 location using power control in a wireless system |
JP4292442B2 (en) * | 2000-01-31 | 2009-07-08 | ソニー株式会社 | Global positioning system receiver and portable radio terminal |
US6603977B1 (en) * | 2000-02-04 | 2003-08-05 | Sbc Properties, Lp | Location information system for a wireless communication device and method therefor |
US6662014B1 (en) | 2000-02-04 | 2003-12-09 | Sbc Properties, L.P. | Location privacy manager for a wireless communication device and method therefor |
US6970708B1 (en) * | 2000-02-05 | 2005-11-29 | Ericsson Inc. | System and method for improving channel monitoring in a cellular system |
KR100359213B1 (en) * | 2000-03-30 | 2002-11-07 | 주식회사 하이닉스반도체 | Location Search Method of Mobile Station Using the Message in Base Transceiver Station System |
US6963548B1 (en) | 2000-04-17 | 2005-11-08 | The Directv Group, Inc. | Coherent synchronization of code division multiple access signals |
US7302224B2 (en) * | 2000-05-03 | 2007-11-27 | The Directv Group, Inc. | Communication system for rebroadcasting electronic content within local area network |
US7254118B1 (en) | 2000-05-22 | 2007-08-07 | Qualcomm Incorporated | Method and apparatus in a CDMA communication system |
US10641861B2 (en) | 2000-06-02 | 2020-05-05 | Dennis J. Dupray | Services and applications for a communications network |
US9875492B2 (en) | 2001-05-22 | 2018-01-23 | Dennis J. Dupray | Real estate transaction system |
US10684350B2 (en) | 2000-06-02 | 2020-06-16 | Tracbeam Llc | Services and applications for a communications network |
US6756937B1 (en) | 2000-06-06 | 2004-06-29 | The Directv Group, Inc. | Stratospheric platforms based mobile communications architecture |
US6388615B1 (en) * | 2000-06-06 | 2002-05-14 | Hughes Electronics Corporation | Micro cell architecture for mobile user tracking communication system |
US7257418B1 (en) | 2000-08-31 | 2007-08-14 | The Directv Group, Inc. | Rapid user acquisition by a ground-based beamformer |
US6763242B1 (en) | 2000-09-14 | 2004-07-13 | The Directv Group, Inc. | Resource assignment system and method for determining the same |
US6697629B1 (en) * | 2000-10-11 | 2004-02-24 | Qualcomm, Incorporated | Method and apparatus for measuring timing of signals received from multiple base stations in a CDMA communication system |
JP2002152799A (en) * | 2000-11-09 | 2002-05-24 | Uniden Corp | System and method for detecting private branch position and terminal |
ATE506828T1 (en) * | 2000-11-14 | 2011-05-15 | Symbol Technologies Inc | METHODS AND DEVICES FOR DETERMINING THE LOCATION OF AN OBJECT IN MOBILE NETWORK |
US6845240B2 (en) | 2000-12-11 | 2005-01-18 | Grayson Wireless | System and method for analog cellular radio geolocation |
US6952158B2 (en) * | 2000-12-11 | 2005-10-04 | Kennedy Jr Joseph P | Pseudolite positioning system and method |
US6891813B2 (en) | 2000-12-12 | 2005-05-10 | The Directv Group, Inc. | Dynamic cell CDMA code assignment system and method |
US6519464B1 (en) * | 2000-12-14 | 2003-02-11 | Pulse-Link, Inc. | Use of third party ultra wideband devices to establish geo-positional data |
US7254401B2 (en) * | 2000-12-19 | 2007-08-07 | Nokia Corporation | Network-based method and system for determining a location of user equipment in CDMA networks |
DE10101503A1 (en) * | 2001-01-12 | 2002-07-25 | Siemens Ag | Method for coordinating transmission interruptions of a multiplicity of base stations of a cellular radio communication system and associated radio communication system |
US6920329B2 (en) * | 2001-01-16 | 2005-07-19 | Allen Telecom | Method and system for applying wireless geolocation technology |
US6941107B2 (en) * | 2001-01-19 | 2005-09-06 | The Directv Group, Inc. | Stratospheric platform based surface vehicle tracking and mobile data network |
JP3543769B2 (en) * | 2001-02-19 | 2004-07-21 | 株式会社日立製作所 | Device for measuring the position of mobile terminals |
US6934548B1 (en) * | 2001-08-10 | 2005-08-23 | Lawrence A. Gould | Methods for detecting, computing and disseminating location information associated with emergency 911 wireless transmissions |
DE10113545A1 (en) * | 2001-03-20 | 2002-10-02 | Tenovis Gmbh & Co Kg | Circuit module position determination for transmitting position of object using circuit modules for transmitting position, circuit modules for picking up position and central processing circuit module |
DE10118777A1 (en) * | 2001-04-17 | 2002-12-05 | Juergen Daesler | Position determination system for mobile radio apparatus compares received station pattern, formed by mobile apparatus, with reference database |
US20020183960A1 (en) * | 2001-05-02 | 2002-12-05 | Chiou Ta-Gang | Method and system for estimating subject position based on chaos theory |
US7363043B2 (en) * | 2001-05-18 | 2008-04-22 | Southwest Research Institute | Passive GSM-based self-locating device |
US7925210B2 (en) * | 2001-05-21 | 2011-04-12 | Sirf Technology, Inc. | Synchronizing a radio network with end user radio terminals |
US8082096B2 (en) | 2001-05-22 | 2011-12-20 | Tracbeam Llc | Wireless location routing applications and architecture therefor |
US7072666B1 (en) * | 2001-06-21 | 2006-07-04 | Spring Spectrum L.P. | Method and system for communicating location in a cellular wireless system |
US7092722B1 (en) | 2001-07-26 | 2006-08-15 | Sprint Spectrum L.P. | Method and system for establishing mobile station active set based on mobile station location |
US7158559B2 (en) * | 2002-01-15 | 2007-01-02 | Tensor Comm, Inc. | Serial cancellation receiver design for a coded signal processing engine |
US8085889B1 (en) | 2005-04-11 | 2011-12-27 | Rambus Inc. | Methods for managing alignment and latency in interference cancellation |
US6871077B2 (en) | 2001-10-09 | 2005-03-22 | Grayson Wireless | System and method for geolocating a wireless mobile unit from a single base station using repeatable ambiguous measurements |
US6728545B1 (en) * | 2001-11-16 | 2004-04-27 | Meshnetworks, Inc. | System and method for computing the location of a mobile terminal in a wireless communications network |
US20050101277A1 (en) * | 2001-11-19 | 2005-05-12 | Narayan Anand P. | Gain control for interference cancellation |
US20040146093A1 (en) * | 2002-10-31 | 2004-07-29 | Olson Eric S. | Systems and methods for reducing interference in CDMA systems |
US7260506B2 (en) * | 2001-11-19 | 2007-08-21 | Tensorcomm, Inc. | Orthogonalization and directional filtering |
US7394879B2 (en) * | 2001-11-19 | 2008-07-01 | Tensorcomm, Inc. | Systems and methods for parallel signal cancellation |
FR2832897B1 (en) * | 2001-11-23 | 2004-02-27 | Evolium Sas | METHOD FOR CELL CHANGE IN A PACKET MOBILE RADIO COMMUNICATION CELL SYSTEM |
DE10159086A1 (en) * | 2001-12-01 | 2003-06-12 | Alcatel Sa | Method for determining the distance between a mobile station and a base station |
US6812889B2 (en) | 2002-01-24 | 2004-11-02 | Motorola, Inc. | Methods and apparatus for determining a direction of arrival in a wireless communication system |
US20030157943A1 (en) * | 2002-01-29 | 2003-08-21 | John Sabat | Method and apparatus for auxiliary pilot signal for mobile phone location |
JP4034571B2 (en) * | 2002-02-08 | 2008-01-16 | 松下電器産業株式会社 | Synchronization detection circuit |
US20040203420A1 (en) * | 2002-04-10 | 2004-10-14 | Rick Roland R. | Method and apparatus for calculating a representative measurement from multiple data measurements |
US7366492B1 (en) | 2002-05-03 | 2008-04-29 | Verizon Corporate Services Group Inc. | Method and system for mobile location detection using handoff information |
US20040208238A1 (en) * | 2002-06-25 | 2004-10-21 | Thomas John K. | Systems and methods for location estimation in spread spectrum communication systems |
US7299063B2 (en) | 2002-07-01 | 2007-11-20 | Sony Corporation | Wireless communication system, wireless communication device and wireless communication method, and computer program |
US7360210B1 (en) | 2002-07-03 | 2008-04-15 | Sprint Spectrum L.P. | Method and system for dynamically varying intermediation functions in a communication path between a content server and a client station |
US7801945B1 (en) | 2002-07-03 | 2010-09-21 | Sprint Spectrum L.P. | Method and system for inserting web content through intermediation between a content server and a client station |
US7568002B1 (en) | 2002-07-03 | 2009-07-28 | Sprint Spectrum L.P. | Method and system for embellishing web content during transmission between a content server and a client station |
US8032149B2 (en) | 2002-08-29 | 2011-10-04 | Andrew Llc | Tasking and reporting method and implementation for wireless appliance location systems |
US7519373B2 (en) * | 2002-08-29 | 2009-04-14 | Andrew Llc | System and method for geo-location of mobile appliances using diverse standard tasking and reporting |
US8761321B2 (en) * | 2005-04-07 | 2014-06-24 | Iii Holdings 1, Llc | Optimal feedback weighting for soft-decision cancellers |
US7787572B2 (en) * | 2005-04-07 | 2010-08-31 | Rambus Inc. | Advanced signal processors for interference cancellation in baseband receivers |
US7876810B2 (en) * | 2005-04-07 | 2011-01-25 | Rambus Inc. | Soft weighted interference cancellation for CDMA systems |
US7463609B2 (en) * | 2005-07-29 | 2008-12-09 | Tensorcomm, Inc | Interference cancellation within wireless transceivers |
US7808937B2 (en) | 2005-04-07 | 2010-10-05 | Rambus, Inc. | Variable interference cancellation technology for CDMA systems |
US20050180364A1 (en) * | 2002-09-20 | 2005-08-18 | Vijay Nagarajan | Construction of projection operators for interference cancellation |
US7577186B2 (en) * | 2002-09-20 | 2009-08-18 | Tensorcomm, Inc | Interference matrix construction |
WO2004028022A1 (en) * | 2002-09-23 | 2004-04-01 | Tensorcomm Inc. | Method and apparatus for selectively applying interference cancellation in spread spectrum systems |
US8005128B1 (en) | 2003-09-23 | 2011-08-23 | Rambus Inc. | Methods for estimation and interference cancellation for signal processing |
US8179946B2 (en) | 2003-09-23 | 2012-05-15 | Rambus Inc. | Systems and methods for control of advanced receivers |
US20050123080A1 (en) * | 2002-11-15 | 2005-06-09 | Narayan Anand P. | Systems and methods for serial cancellation |
AU2003301493A1 (en) * | 2002-10-15 | 2004-05-04 | Tensorcomm Inc. | Method and apparatus for interference suppression with efficient matrix inversion in a ds-cdma system |
WO2004036812A2 (en) * | 2002-10-15 | 2004-04-29 | Tensorcomm Inc. | Method and apparatus for channel amplitude estimation and interference vector construction |
EP1559291B1 (en) * | 2002-11-08 | 2012-08-01 | Nokia Corporation | Handling location services independently from the cellular communication system |
US7162252B2 (en) * | 2002-12-23 | 2007-01-09 | Andrew Corporation | Method and apparatus for supporting multiple wireless carrier mobile station location requirements with a common network overlay location system |
CN1830163B (en) * | 2003-05-23 | 2011-11-09 | 讯宝科技公司 | Method for calibrating target positioning system |
US7429914B2 (en) * | 2003-06-04 | 2008-09-30 | Andrew Corporation | System and method for CDMA geolocation |
EP1494488A1 (en) * | 2003-07-01 | 2005-01-05 | Precisa Instruments AG | Mobile phone comprising position computation means |
DE10332551B4 (en) * | 2003-07-17 | 2006-11-09 | Jülg, Thomas, Dipl.-Ing. Dr. | Method for determining position |
KR20050011868A (en) * | 2003-07-24 | 2005-01-31 | 유티스타콤코리아 유한회사 | Device and method for tracking position of cellular phone using beacon in mobile communication system |
US7079609B2 (en) * | 2003-07-31 | 2006-07-18 | Motorola, Inc. | Method and apparatus for reducing interference within a communication system |
GB2406021A (en) * | 2003-09-12 | 2005-03-16 | Matsushita Electric Ind Co Ltd | Power efficient method for a mobile terminal to determine its location by processing only parts of the received signal |
US8234373B1 (en) | 2003-10-27 | 2012-07-31 | Sprint Spectrum L.P. | Method and system for managing payment for web content based on size of the web content |
US20050105600A1 (en) * | 2003-11-14 | 2005-05-19 | Okulus Networks Inc. | System and method for location tracking using wireless networks |
US20050169354A1 (en) * | 2004-01-23 | 2005-08-04 | Olson Eric S. | Systems and methods for searching interference canceled data |
US7477710B2 (en) * | 2004-01-23 | 2009-01-13 | Tensorcomm, Inc | Systems and methods for analog to digital conversion with a signal cancellation system of a receiver |
KR100573203B1 (en) * | 2004-03-17 | 2006-04-24 | 에스케이 텔레콤주식회사 | Method and System for Determining Position of Terminal by Using Location Detector in GPS Satellite-Invisible Area |
US6876325B1 (en) | 2004-04-01 | 2005-04-05 | Itt Manufacturing Enterprises, Inc. | System and method for location-finding using communication signals |
US7187327B2 (en) * | 2004-04-01 | 2007-03-06 | Itt Manufacturing Enterprises, Inc. | Method and system for determining the position of an object |
US7272495B2 (en) | 2004-04-01 | 2007-09-18 | Itt Manufacturing Enterprises, Inc. | System and method for inverse multilateration |
US9172679B1 (en) | 2004-04-14 | 2015-10-27 | Sprint Spectrum L.P. | Secure intermediation system and method |
US7853782B1 (en) | 2004-04-14 | 2010-12-14 | Sprint Spectrum L.P. | Secure intermediation system and method |
US7512973B1 (en) | 2004-09-08 | 2009-03-31 | Sprint Spectrum L.P. | Wireless-access-provider intermediation to facilliate digital rights management for third party hosted content |
US8023554B2 (en) * | 2004-10-06 | 2011-09-20 | Broadcom Corporation | Method and system for single antenna receiver system for WCDMA |
JP2006118881A (en) * | 2004-10-19 | 2006-05-11 | Ntt Docomo Inc | Location positioning system and location positioning method |
US7600011B1 (en) | 2004-11-04 | 2009-10-06 | Sprint Spectrum L.P. | Use of a domain name server to direct web communications to an intermediation platform |
US20060125689A1 (en) * | 2004-12-10 | 2006-06-15 | Narayan Anand P | Interference cancellation in a receive diversity system |
CN1327743C (en) * | 2005-01-25 | 2007-07-18 | 华为技术有限公司 | Method of processing delaying type position requirement |
US7826516B2 (en) | 2005-11-15 | 2010-11-02 | Rambus Inc. | Iterative interference canceller for wireless multiple-access systems with multiple receive antennas |
US20060229051A1 (en) * | 2005-04-07 | 2006-10-12 | Narayan Anand P | Interference selection and cancellation for CDMA communications |
US8320264B2 (en) * | 2005-05-17 | 2012-11-27 | Andrew Llc | Method and apparatus for determining path loss by active signal detection |
US7583654B2 (en) * | 2005-12-28 | 2009-09-01 | Honeywell International Inc. | Sub-frame synchronized multiplexing |
US9354321B2 (en) | 2006-03-06 | 2016-05-31 | Qualcomm Incorporated | Method for position determination with measurement stitching |
US7719994B2 (en) * | 2006-04-26 | 2010-05-18 | Honeywell International Inc. | Sub-frame synchronized ranging |
US8019339B2 (en) | 2006-05-16 | 2011-09-13 | Andrew Llc | Using serving area identification in a mixed access network environment |
US8000701B2 (en) | 2006-05-16 | 2011-08-16 | Andrew, Llc | Correlation mechanism to communicate in a dual-plane architecture |
US8000702B2 (en) * | 2006-05-16 | 2011-08-16 | Andrew, Llc | Optimizing location services performance by combining user plane and control plane architectures |
US7688747B2 (en) * | 2006-08-30 | 2010-03-30 | Honeywell International Inc. | Sub-frame synchronized residual ranging |
JP4728923B2 (en) * | 2006-09-26 | 2011-07-20 | 富士通株式会社 | Wireless positioning system |
CN101536449B (en) * | 2006-11-06 | 2014-04-16 | 高通股份有限公司 | Cell search based on beacon in a wireless communication system |
KR100926292B1 (en) | 2006-12-04 | 2009-11-12 | 한국전자통신연구원 | Distance estimation method between two sensor nodes using round trip time delay |
US7515092B2 (en) * | 2007-01-17 | 2009-04-07 | Honeywell International Inc. | Sub-frame synchronized residual radar |
CA2677087A1 (en) | 2007-02-05 | 2008-08-14 | Andrew Corporation | System and method for optimizing location estimate of mobile unit |
US8005050B2 (en) | 2007-03-23 | 2011-08-23 | Lgc Wireless, Inc. | Localization of a mobile device in distributed antenna communications system |
JP5201861B2 (en) * | 2007-03-27 | 2013-06-05 | 富士通コンポーネント株式会社 | Information providing system and information providing method |
US7941163B2 (en) * | 2007-06-29 | 2011-05-10 | Alcatel-Lucent Usa Inc. | Determining the location of a wireless mobile communications device |
US8195204B1 (en) | 2007-07-25 | 2012-06-05 | Sprint Spectrum L.P. | Method and apparatus for scanning sectors in order of distance from mobile station |
US7881263B1 (en) | 2007-07-31 | 2011-02-01 | Sprint Spectrum L.P. | Method for use of azimuth and bearing data to select a serving sector for a mobile station |
US20090061892A1 (en) * | 2007-08-27 | 2009-03-05 | Via Telecom, Inc. | Location assisted connection to femtocell |
US8103267B2 (en) * | 2007-09-26 | 2012-01-24 | Via Telecom, Inc. | Femtocell base station with mobile station capability |
US8937936B2 (en) * | 2007-10-05 | 2015-01-20 | Via Telecom Inc. | Acquiring time synchronization and location information with a femtocell |
US8248923B2 (en) * | 2007-10-05 | 2012-08-21 | Via Telecom, Inc. | Automatic provisioning of admission policy for femtocell |
US9363770B2 (en) * | 2007-10-05 | 2016-06-07 | Ipcomm | Automatic provisioning of handoff parameters for femtocell |
US8223683B2 (en) * | 2007-10-05 | 2012-07-17 | VIA Telecom, Inc | Automatic provisioning of femtocell |
US8213391B2 (en) * | 2007-10-05 | 2012-07-03 | Via Telecom, Inc. | Time synchronization of femtocell |
US8170585B2 (en) | 2007-11-14 | 2012-05-01 | Andrew, Llc | Ranging in UMTS networks |
US8447319B2 (en) * | 2007-11-15 | 2013-05-21 | Andrew Llc | System and method for locating UMTS user equipment using measurement reports |
CN101437287B (en) * | 2007-11-15 | 2011-01-19 | 展讯通信(上海)有限公司 | Method and system for wireless localization through assistant base station update |
US7800530B2 (en) * | 2007-12-07 | 2010-09-21 | Andrew, Llc | Method and system for providing assistance data for A-GPS location of handsets in wireless networks |
US8520659B2 (en) * | 2007-12-18 | 2013-08-27 | Airvana Llc | Absolute time recovery |
US20090154401A1 (en) * | 2007-12-18 | 2009-06-18 | Motorola, Inc. | Methods and systems for initial ranging |
US8379625B2 (en) * | 2007-12-18 | 2013-02-19 | Airvana Llc | Obtaining time information in a cellular network |
US9026129B2 (en) * | 2007-12-19 | 2015-05-05 | Qualcomm Incorporated | Systems and methods for locating a mobile device |
US8140107B1 (en) | 2008-01-04 | 2012-03-20 | Sprint Spectrum L.P. | Method and system for selective power control of wireless coverage areas |
US8213955B2 (en) | 2008-05-01 | 2012-07-03 | Andrew, Llc | Network measurement report caching for location of mobile devices |
US8744493B2 (en) * | 2008-05-28 | 2014-06-03 | Via Telecom, Inc. | Localized silence area for mobile devices |
US8073463B2 (en) | 2008-10-06 | 2011-12-06 | Andrew, Llc | System and method of UMTS UE location using uplink dedicated physical control channel and downlink synchronization channel |
US8762519B2 (en) * | 2008-10-28 | 2014-06-24 | Andrew Llc | System and method for providing location services for multiple access networks from a single location server |
WO2010052673A1 (en) * | 2008-11-06 | 2010-05-14 | Nokia Siemens Networks Oy | Wireless device location services |
US8964692B2 (en) | 2008-11-10 | 2015-02-24 | Qualcomm Incorporated | Spectrum sensing of bluetooth using a sequence of energy detection measurements |
US8035557B2 (en) * | 2008-11-24 | 2011-10-11 | Andrew, Llc | System and method for server side detection of falsified satellite measurements |
US8380222B2 (en) | 2008-11-26 | 2013-02-19 | Andrew Llc | System and method for multiple range estimation location |
US8249622B2 (en) * | 2008-11-26 | 2012-08-21 | Andrew, Llc | System and method for multiple range estimation location |
US8160609B2 (en) * | 2008-11-26 | 2012-04-17 | Andrew Llc | System and method for multiple range estimation location |
US7916071B2 (en) * | 2008-12-23 | 2011-03-29 | Andrew, Llc | System and method for determining a reference location of a mobile device |
US8391884B2 (en) * | 2009-03-26 | 2013-03-05 | Andrew Llc | System and method for managing created location contexts in a location server |
US8699409B2 (en) * | 2009-04-08 | 2014-04-15 | Qualcomm Incorporated | Methods and apparatuses for providing peer-to-peer positioning in wireless networks |
US9001811B2 (en) | 2009-05-19 | 2015-04-07 | Adc Telecommunications, Inc. | Method of inserting CDMA beacon pilots in output of distributed remote antenna nodes |
US8290510B2 (en) * | 2009-06-11 | 2012-10-16 | Andrew Llc | System and method for SUPL held interworking |
US9074897B2 (en) | 2009-06-15 | 2015-07-07 | Qualcomm Incorporated | Real-time data with post-processing |
WO2011016804A1 (en) | 2009-08-05 | 2011-02-10 | Andrew Llc | System and method for hybrid location in an lte network |
US8217832B2 (en) * | 2009-09-23 | 2012-07-10 | Andrew, Llc | Enhancing location accuracy using multiple satellite measurements based on environment |
US8289210B2 (en) | 2009-10-15 | 2012-10-16 | Andrew Llc | Location measurement acquisition adaptive optimization |
US8188920B2 (en) * | 2009-10-15 | 2012-05-29 | Andrew, Llc | Location measurement acquisition optimization with Monte Carlo simulation |
US9331798B2 (en) * | 2010-01-08 | 2016-05-03 | Commscope Technologies Llc | System and method for mobile location by proximity detection |
US8718673B2 (en) | 2010-05-21 | 2014-05-06 | Maple Acquisition Llc | System and method for location assurance of a mobile device |
US8704707B2 (en) | 2010-06-02 | 2014-04-22 | Qualcomm Incorporated | Position determination using measurements from past and present epochs |
US8478275B1 (en) | 2010-08-05 | 2013-07-02 | Sprint Spectrum L.P. | Conditional assignment of connection identifiers to help avoid communication errors |
US9538493B2 (en) | 2010-08-23 | 2017-01-03 | Finetrak, Llc | Locating a mobile station and applications therefor |
CN101974786B (en) * | 2010-09-09 | 2013-03-13 | 浙江省农业科学院 | Method for constructing eukaryote cDNA library and special primers thereof |
US8958754B2 (en) | 2010-09-29 | 2015-02-17 | Andrew, Llc | System and method for sub-coherent integration for geo-location using weak or intermittent signals |
US8489122B2 (en) | 2010-12-09 | 2013-07-16 | Andrew Llc | System and method for total flight time ratio pattern matching |
US8625490B2 (en) | 2011-01-07 | 2014-01-07 | Apple Inc. | Multiple granularity location determination |
US8526968B2 (en) | 2011-02-14 | 2013-09-03 | Andrew Llc | System and method for mobile location by dynamic clustering |
US9715001B2 (en) | 2011-06-13 | 2017-07-25 | Commscope Technologies Llc | Mobile location in a remote radio head environment |
US8670425B1 (en) | 2011-08-09 | 2014-03-11 | Sprint Spectrum L.P. | Use of past duration of stay as trigger to scan for wireless coverage |
US9423508B2 (en) | 2012-01-12 | 2016-08-23 | Commscope Technologies Llc | Autonomous Transmit Chain Delay Measurements |
US8897813B2 (en) | 2012-02-03 | 2014-11-25 | Andrew Llc | LTE user equipment positioning system and method |
US8848565B2 (en) * | 2012-07-12 | 2014-09-30 | Qualcomm Incorporated | Method for performing measurements and positioning in a network based WLAN positioning system |
CN105100292B (en) | 2014-05-12 | 2018-12-18 | 阿里巴巴集团控股有限公司 | Determine the method and device of the position of terminal |
FR3103339B1 (en) * | 2019-11-14 | 2022-12-30 | Thales Sa | METHOD AND SYSTEM FOR LOCATION AND SATELLITE COMMUNICATION OF A GROUND-FIXED RADIO-ELECTRIC TERMINAL USING AT LEAST ONE TRAVELING SATELLITE |
CN113568023A (en) * | 2020-04-28 | 2021-10-29 | 广州汽车集团股份有限公司 | Vehicle-mounted positioning method and vehicle-mounted positioning module |
Family Cites Families (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL8103475A (en) * | 1981-07-23 | 1983-02-16 | Hollandse Signaalapparaten Bv | ENERGY CONVERTER. |
US4670906A (en) * | 1986-04-02 | 1987-06-02 | Motorola, Inc. | Data communications system transmitter selection method and apparatus |
EP0331858B1 (en) * | 1988-03-08 | 1993-08-25 | International Business Machines Corporation | Multi-rate voice encoding method and device |
FR2646302B1 (en) * | 1989-04-25 | 1993-01-15 | Matra Communication | PSEUDO-SYNCHRONIZATION METHOD OF A TIME MULTIPLEXED COMMUNICATION NETWORK AND APPLICATIONS |
JPH02287399A (en) * | 1989-04-28 | 1990-11-27 | Fujitsu Ltd | Vector quantization control system |
US5247357A (en) * | 1989-05-31 | 1993-09-21 | Scientific Atlanta, Inc. | Image compression method and apparatus employing distortion adaptive tree search vector quantization with avoidance of transmission of redundant image data |
US4974099A (en) * | 1989-06-21 | 1990-11-27 | International Mobile Machines Corporation | Communication signal compression system and method |
US5021794A (en) * | 1989-08-15 | 1991-06-04 | Lawrence Robert A | Personal emergency locator system |
US4963030A (en) * | 1989-11-29 | 1990-10-16 | California Institute Of Technology | Distributed-block vector quantization coder |
SE466376B (en) * | 1990-09-13 | 1992-02-03 | Televerket | PROCEDURES FOR LOCALIZATION IN MOBILE RADIO SYSTEM |
US5218716A (en) * | 1990-11-05 | 1993-06-08 | Motorola, Inc. | Method for locating a communication unit within a multi mode communication system |
US5218618A (en) * | 1990-11-07 | 1993-06-08 | Hughes Aircraft Company | Cellular telephone service using spread spectrum transmission |
US5365544A (en) * | 1990-12-05 | 1994-11-15 | Interdigital Technology Corporation | CDMA communications and geolocation system and method |
IT1241358B (en) * | 1990-12-20 | 1994-01-10 | Sip | VOICE SIGNAL CODING SYSTEM WITH NESTED SUBCODE |
ES2166355T3 (en) * | 1991-06-11 | 2002-04-16 | Qualcomm Inc | VARIABLE SPEED VOCODIFIER. |
US5365516A (en) * | 1991-08-16 | 1994-11-15 | Pinpoint Communications, Inc. | Communication system and method for determining the location of a transponder unit |
US5293645A (en) * | 1991-10-04 | 1994-03-08 | Sharp Microelectronics Technology, Inc. | Apparatus and method for locating mobile and portable radio terminals in a radio network |
US5218367A (en) * | 1992-06-01 | 1993-06-08 | Trackmobile | Vehicle tracking system |
US5396541A (en) * | 1992-10-23 | 1995-03-07 | At&T Corp. | Call handoff in a wireless telephone system |
US5341456A (en) * | 1992-12-02 | 1994-08-23 | Qualcomm Incorporated | Method for determining speech encoding rate in a variable rate vocoder |
FR2709366B1 (en) * | 1993-03-26 | 2001-09-14 | Motorola Inc | Method for storing reflection coefficient vectors. |
US5404376A (en) * | 1993-09-09 | 1995-04-04 | Ericsson-Ge Mobile Communications Inc. | Navigation assistance for call handling in mobile telephone systems |
-
1995
- 1995-05-08 US US08/436,760 patent/US5508708A/en not_active Expired - Lifetime
-
1996
- 1996-02-16 US US08/601,315 patent/US5736964A/en not_active Expired - Lifetime
- 1996-03-21 BR BR9606340A patent/BR9606340A/en not_active IP Right Cessation
- 1996-03-21 JP JP53404296A patent/JP3254682B2/en not_active Expired - Fee Related
- 1996-03-21 CA CA002192579A patent/CA2192579C/en not_active Expired - Lifetime
- 1996-03-21 CN CN96190397A patent/CN1097734C/en not_active Expired - Lifetime
- 1996-03-21 PL PL96318057A patent/PL180276B1/en unknown
- 1996-03-21 RU RU97101879A patent/RU2127963C1/en active
- 1996-03-21 GB GB9625755A patent/GB2304500B/en not_active Expired - Lifetime
- 1996-03-21 KR KR1019970700060A patent/KR100208647B1/en not_active IP Right Cessation
- 1996-03-21 WO PCT/US1996/003797 patent/WO1996035958A1/en active IP Right Grant
- 1996-03-26 IL IL11765496A patent/IL117654A/en not_active IP Right Cessation
- 1996-04-23 FR FR9605090A patent/FR2734108B1/en not_active Expired - Fee Related
- 1996-05-06 IT IT96RM000306A patent/IT1284380B1/en active IP Right Grant
- 1996-12-02 SE SE9604432A patent/SE517676C2/en not_active IP Right Cessation
- 1996-12-30 FI FI965257A patent/FI115886B/en not_active IP Right Cessation
-
1997
- 1997-04-24 US US08/842,350 patent/US5764188A/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
SE9604432D0 (en) | 1996-12-02 |
FI965257A (en) | 1996-12-31 |
GB2304500A (en) | 1997-03-19 |
SE9604432L (en) | 1997-03-07 |
CA2192579A1 (en) | 1996-11-14 |
FR2734108A1 (en) | 1996-11-15 |
ITRM960306A1 (en) | 1997-11-06 |
PL318057A1 (en) | 1997-05-12 |
GB2304500B (en) | 1999-12-01 |
RU2127963C1 (en) | 1999-03-20 |
SE517676C2 (en) | 2002-07-02 |
BR9606340A (en) | 1997-09-02 |
JPH10505723A (en) | 1998-06-02 |
FI965257A0 (en) | 1996-12-30 |
PL180276B1 (en) | 2001-01-31 |
IL117654A0 (en) | 1996-07-23 |
GB9625755D0 (en) | 1997-01-29 |
FR2734108B1 (en) | 2000-03-10 |
IT1284380B1 (en) | 1998-05-18 |
US5508708A (en) | 1996-04-16 |
WO1996035958A1 (en) | 1996-11-14 |
FI115886B (en) | 2005-07-29 |
IL117654A (en) | 2000-02-29 |
US5736964A (en) | 1998-04-07 |
CN1097734C (en) | 2003-01-01 |
CN1152356A (en) | 1997-06-18 |
ITRM960306A0 (en) | 1996-05-06 |
KR970705034A (en) | 1997-09-06 |
JP3254682B2 (en) | 2002-02-12 |
KR100208647B1 (en) | 1999-07-15 |
US5764188A (en) | 1998-06-09 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2192579C (en) | Method and apparatus for location finding in a cdma system | |
US5945948A (en) | Method and apparatus for location finding in a communication system | |
US6658258B1 (en) | Method and apparatus for estimating the location of a mobile terminal | |
CA2388743C (en) | Method and apparatus for determining the position location using reduced number of gps satellites and synchronized and unsynchronized base stations | |
JP4482645B2 (en) | Method and apparatus for performing wireless communication system synchronization | |
KR100899465B1 (en) | Method and apparatus for estimating the position of a terminal based on identification codes for transmission sources | |
US6525689B2 (en) | Method of despreading GPS spread spectrum signals | |
Caffery et al. | Radio location in urban CDMA microcells | |
CA2548669A1 (en) | Tdoa/gps hybrid wireless location system | |
AU2002305231A1 (en) | Method and apparatus for estimating the position of a terminal based on identification codes for transmission sources | |
US20030008664A1 (en) | Method and apparatus for estimating the postion of a terminal based on identification codes for transmission sources | |
US6888817B1 (en) | Method and apparatus for positioning a mobile station in a TDMA system | |
KR100622218B1 (en) | Apparatus and method for location determination by single cell in mobile communication system | |
US6961543B2 (en) | Pilot phase measurement error estimator for position location | |
JP3750438B2 (en) | Location information system | |
KR100227783B1 (en) | Method for identifying car position in the cdma mobile system | |
GB2357014A (en) | Locating a mobile transmitting at high power with a three antenna base station | |
Chen | Location estimation in CDMA systems: enhanced measurement on pilot channels |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
MKEX | Expiry |
Effective date: 20160321 |