CA2054198C - Communications system using spread spectrum and leaky transmission line - Google Patents
Communications system using spread spectrum and leaky transmission lineInfo
- Publication number
- CA2054198C CA2054198C CA002054198A CA2054198A CA2054198C CA 2054198 C CA2054198 C CA 2054198C CA 002054198 A CA002054198 A CA 002054198A CA 2054198 A CA2054198 A CA 2054198A CA 2054198 C CA2054198 C CA 2054198C
- Authority
- CA
- Canada
- Prior art keywords
- transmission line
- spread spectrum
- leaky transmission
- mhz
- frequency band
- 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 - Fee Related
Links
- 238000001228 spectrum Methods 0.000 title claims abstract description 62
- 238000004891 communication Methods 0.000 title claims abstract description 57
- 230000006854 communication Effects 0.000 title claims abstract description 56
- 230000005540 biological transmission Effects 0.000 title claims description 76
- 238000010168 coupling process Methods 0.000 claims description 22
- 238000005859 coupling reaction Methods 0.000 claims description 22
- 230000008878 coupling Effects 0.000 claims description 21
- 230000007423 decrease Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 claims description 3
- 230000001902 propagating effect Effects 0.000 claims description 3
- 230000008054 signal transmission Effects 0.000 claims 1
- 238000001914 filtration Methods 0.000 abstract description 2
- 238000002955 isolation Methods 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 description 7
- 230000005855 radiation Effects 0.000 description 6
- 230000035945 sensitivity Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 108010003272 Hyaluronate lyase Proteins 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000007175 bidirectional communication Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000001413 cellular effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 230000000153 supplemental effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- H04B5/48—
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
-
- H04B5/28—
Abstract
A spread spectrum communications system uses a leaky coaxial cable for cost effective radio communication in enclosed areas. The system includes radio units (12) which communicate with a transceiver, the transceiver being coupled to the leaky coaxial cable (16). Full-duplex communication includes a first frequency band (F1) for transmitting spread spectrum signals from the transceiver to the radio units at power levels which are adjusted to take advantage of the losses associated with leaky coaxial cable, and a second frequency band (F2) for transmitting spread spectrum signals from the radio units to the transceiver at the more conventional spread spectrum power levels specified by the FCC. The present invention employs this split band configuration to accommodate communication over leaky coaxial cable without expensive and bulky filtering for isolation between the transmit and receive signals.
Description
WO 91~1~068 PCr/~1~91/0i779 co;~lrNIcATIoN 8Y8T~ U8ING ~PRE~D :~
8PEC~ D LE~Y T~AN8MI88ION LINE
Fiel~ Of The Inventio~
The present invention relates generally to radio communication systems and, more particularl~, to radio communication systems employing spread spectrum and S radiating transmission line technologies.
,~ .
Baclc~roun~ Of The Invention Spread spectrum technology has been known for some time. A spread spectrum system is one in which the transmitted slgnal is spread over a wide frequency band.
Typically, the frequency band over which the transmitted signal is spread is wider, by a substantial margin, than the minimum bandwidth required to transmit the information being sent. For example, a spread spectrum system may convert a base-band signal having a bandwidth of a few kilo-Hertz (kHz) to a spread spectrum signal having a -- bandwidth of many Giga-Hertz (GHz), and transmit the signal using that wider bandwidth.
Spread ~spectrum signals are typically generated using , 20 - code-modulation such as frequency hopping or direct sequence coding. Becau$e of this code modulation, the - _~ower transmitted i9 low in any narrow frequency region.
he power density of a spread spectrum signal is far less =- than that of more conventional signals in which all the transmitted power is sent in a band of frequencies commensurate with the baseband information bandwidth.
WO91/15068 PCT/~'S91/017~"~
Z C ~ ~ 2 Spread spectrum communication provides a number of advantages over more conventional types of communication systems. These advantages include selective addressing capability, coupled access for code division multiplexing, message screening from eavesdroppers and low-density power spectra for signal hiding. These characteristics are useful and highly desirable in many types of radio communication systems. These and other characteristics of , spread spectrum technology are described in SPREAD SPECTRUM
SYSTEMS, edited by Robert C. Dixon, published by John Wiley & Sons, Inc. (1984). ;
For purposes of background information dealing with ~ ~
conventional spread spectrum systems, as well as for l `
supplemental information dealing with modular yet 15 conventional segments of the illustrative embodiments set I i I ,.
forth herein, the reader's attention is directed to the 'I
following references: U.S. Pat. Nos. 4,'455,651, and 4,086,~504, dealing with wireless systems employing spread spectrum techniques; U.5. Pat. No. 4,438,5'19, dealing with ~20 a narrow-bandwidth spread spectrum system using an AC power - line as an antenna; U.S. Pat. No. 4,475,iO8,~concerning a voiceldata spread spectrum system; U.S.'Pat. No.- 4,320,514, dealing with a spread spectrum radio receiver ~or frequency hopped signals; and U.S. Pat. No. 4,'672,605,- dealing with a'"''L~ 25 data/voice communication system based on'spe~trum spreading. ~ ~
One rather unique type of radio aommunication system ~ ' employs a radiating (or "leaky") transmisslon line, such as , ' ~'091/1506~ ~ PCT/US91/01779 . . ~
leaky coaxial cable, throughout a confined area to provide -coverage in that~area. Leaky transmission line is advantageous, because it provides for total aoverage of a restricted area. Thus, it is not uncommon to find leaky transmission line in tunnels, offices and other areas that are frequency-blocked from externally located wide area coverage communication systems.
Combining leaky transmission line with spread spectrum technology in a single system, to realize the advantages of lO both technologies, has been recognized as a worthwhile ;
objective. For example, in U.S. Patent No. 4,866,732 these technologies are described as part of a single system having radio units communicating over a radiating ¦
transmission line, with each radio unit communicating using lS~ a uniquely~;assigned spreading code. Unfortunately, there are probiems associated with the implementation of this ¦ `~
technological combination which have not been overcome. ;~
A fundamental problem with such a system involves regulations defined by~the Federal Communications Commission~ (FCC). The FCC has allocated certain bands for use of spre~ad~spectrum radio transmLssions having a power level of up to one Watt. These FCC bands~are commonly -~
referred to as the Industrial, Scientiflc and Medical (ISM) bands and are respectively assigned to the frequency ranges of 902-928 MHz, 2400-2483.5 MHz and= 5-7~5-5850 MHz.
. . .
Although operation at 2400-2483.5 MHz is conceivable with leaky coaxial cable, there remains a- number of unsolved problems concerning coupling losses and attenuation in WO91~15068 PCT/~S91/01779 a -~
4 ~-leaky coaxial cable at this frequency. Moreover, due to attenuation, leaky coaxial ca~le is not typically useful - ;;
for frequency transmissions in excess of 2 GHz. Thus, the most practical ISM band is in the 902-928 MHz region.
The 26 MHz bandwidth in the 902-928 MHz region is, however, narrow and complicates full-duplex spread spectrum communication over leaky coaxial cable. This is because a 26 MHz bandwidth does not allow for the provision of sufficient isolation between the transmit and receive 10 signals without the aid of extènsive filtering tools, which ~ ~
can be expensive and occupy an excessive amount of space. -Accordingly, there is a need for a spread spectrum -communication system using leaky coaxLal cable that can be ;~
implemented in a cost effective manner while overcoming the 1, ',"
15 afore-mentioned problems. ! ~
~,,, ummary Of The In~ontion It is a general object of the present invention to provide a spread spectrum communication system which uses leaky transmission line to provide communication in a prescribed communication coverage area. ~`
It is a more specific object of the present invention to provide a full-duplex spread spectrum communication system using leaky coaxial cable to provide communication within the guidelines established by the FCC in a cost-effective and space-conscious manner. `
According to a preferred embodiment, the present invention provides a communication system comprising a leaky transmission line coupled to a transceiver for providing two-way radio coverage in separated first ~n~
second frequency bands. The leaky transmission line is used for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area, and the transceiver is used for providing spread spectrum signals to the leaky transmission line in a first frequency band and at-a first predetermined power level. A plurality ~ of radio units, situated within the prescribed coverage area, receive the spread spectrum signals transmitte~ f~o~
the leaky transmission line in the first frequency band and transmit spread spectrum signals to the transceiver, via -~ the leaky transDission line, in the second frequenc~u~
These bands are selected with respect to the transmission 15~ restrictions set forth by the FCC. Further, the leaky transmission line decreases the power level of the spread spectrum signals provided by the transceiver means to a second preselected power Ievel so as not to encroach the I `
guidelines set forth by the FCC concerning spread spectrum 20 ~ ~signals.
~; Preferably, the power level of the signals leaving the transceiv~er is set, according to the couplinq and attenuation losses of the cable, so as to maximize the power level of the signals rad~ating from the ca~le without ~: h: .
exceeding the threshold. It i8 in this manner that the leaky transmission line may be used to decrease the power }evel of the spread spectrum signals provided by the transceiver means to the second preselected power level.
WO91/1~068 ~ PCT/~'S91/01779 . ~
Brief De~cription Of The Drawina~
Other objects and ad~antages of the present invention will become apparent upon reading the following detailed ~`
description and upon reference to the drawings in which~
S FI~. 1 is a block diagram of a radio communication system, illustrating one embodiment of the present ` f invention; and FIG. 2 is a block diagram of another radio communication system, illustrating other aspects of the , .
preæent invention~
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereo~ have been shown by way of example in the drawings and will herein be described in detail. It should be ~understood, howèver, that it is not intended to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, quivalents~, and alternatives falling within the spirit and .,. ,~;
~ scope o~f the invention as definèd~by-the app-nded claims. i`
:~ ~ : ;~
;~
... ~
. . ' , . ..
~: . .
-- . .
.~ : ': , .
: ~' ~, Wo91/15068 z ~ PCTJ~!S91/0~779 Detaile~ Description Of T~e PrQferred Embodiment~
The present invention is directed to spread spectrum communication systems employing radiating (or leaky) transmission lines, e.g., ~eaky coaxial cables for two-way radio communication, for example, full-duplex or half-duplex communication. Because of certain problems that are ;
solved by the present invention, it is especially suited for a spread spectrum system providing full-duplex communication in narrow coverage areas.
10Referring now to FIG. l, the present invention is illustrated in the form of a radio communication system having radio units 12 and a control station 18. Actual coupling of radio frequency (RF) signals between the I, control station 18 and the radio units 12 can be accomplished in several ways. By way of illustration only, .:
the representative system of FIG. l includes a repeater 14, which may be a transceiver or translator, and a leaky transmission line 16 for-such coupling. The repeater 14 may include a conventional bi-directional amplifier and transceiver means (not shown) suitable for transmission of - , . .. . .
the spread spectrum signàl.~ These elements are used to provide two-way radio communication from the control station 18 to the radio units 12 in a first radio frequency band (Fl), and in a second~freguency band tF2) from the ~- 25 radio units 12 to the co~tro~-station 18. More specifically, the leaky transmission line is in the form of radiating cable of either the slotted type or other form wherein the slots or other openings disposed on the ;
WO91~1506~ PCT/~!S91/01 79 metallic outer conductor of the cable permit a controlled portion of the electromagnetic signals being transmitted therethrough to propagate along the length of the ca~le so that any radio units 12 disposed in the vicinity of such leaky transmission line may receive the signals being radiated therefrom. The leaky transmission line approach is particularly advantageous in bi-directional communication systems because electromagnetic signals transmitted near the transmission line lengths are coupled into the radiation slots and carried back along the length of the cable to the control station. I
Accordingly, RF signals transmitted by mobile or r~`
portable radio units in the RF coverage area of the control ¦ ~
.~
station 18 can be picked up directly by the leaky 15 transmission line 16 and relayed to the control station 18. Ii , Signals transmitted from the control station 18 to the radio units 12 travel in essentially the opposite manner.
In a similar arrangement, by using other repeaters 14, the control station 18 can also link radio units 12 in different coverage areas defined by respective leaky transmission lines 16. This configuration is useful in a number of different kinds of two-way radio systems. For example, it may used in cellular telephone communication or trunked radio communication, or in vehicle telemètry ¦ `
applications where a test vehicle ~e.g., auto, bus, military wheeled or track vehicle) is connected to a data acquisition computer using spread spectrum radio communications over leaky transmission line. Another WO91/1~068 Z ~ - PCT/~!S91/01779 application is in a factory, office or institution where leaky transmission line is distributed therethrough to provide the necessary coverage.
- In the second frequency band, communication from the radio unit 12 to the control station 18 may be implemented using conventional spread spectrum technology at conventional power levels. For example, this signal path may include either direct sequence or frequency hopping - type spread spectrum communication where the signals are transmitted in the 902-928 MHz region and at conventional power levels into the leaky transmission line 16. This ;
implementation is consistent with FCC frequency band allocations for spread spectrum transm~issions, as the 902-92~8 MHz~region is one of the ISM bands allocated for spread spectrum use by the FCC.
In the first frequency band, radio signal , .
.
~ communication is implemented from the control station 18 to .
the radio units 12 without interfering with the signals in the æecond frequency band and without exceeding FCC ~ L' restrictions. Based on the spreading factor, spread spectrum communication can spread the signal over the ~ ~
entire frequency band. In addition, based on available - -~~-bandwidth of the frequency band, it is possible to provide ~ for diff-rent spreading factors up to that factor that will ---- ``
spread the signal over the entire band. This causes both _ _-transmit and receive si~nals to interfere with one another if they are carried simultaneously in a single 26 MHz region, such as the desirable 902-928 MHz region which is WO91/15068 ~ PCT/US91/01779 10 - .
the most practical region. As will be discussed, FCC
requirements restrict use of frequencies outside the ISM
bands.
The present invention overcome~ this problem, through ;~-proper selection of the frequency bands and appropriate power level selection. With the second frequency band assigned to the 902-928 MHz region, the first frequency band is selected in one of two ways. First, it can be selected from a region outside of those bands which are designated as restricted by the FCC (i.e., a non-restricted region). Second, it can be selected as the 2400-2483.5 MHz ISM band if consideration is given to increase power to overcome attenuation and coupling loss. Within that non- `~
restricted region, the transmitted signal power level is 15 maximum at the point that the signal is coupled to the ¦
leaky transmission line to the extent possible without exceeding the FCC power restrictions concerning intentional radiators. Within the 2400-2483.5 MHz ISM band, consideration is~given to increasing the power level of the signal in order to increase the length of the leaky transmission~line and/or to increase the distance between the leaky transmission line and the radio units.
The following tables, Tables l and 2, are provided to illustrate how~the first frequency band may be selected. ;
25 Tables l and~-Z-respectively list the FCC restricted bands ~
-- , ~
below 2 GHz and the available (or non-restricted) frequency bands for intentional radiation between 960 MHz and 2.2 GHz.
WO91/1~068 X~ PCT/US91/01779 Table 1: FCC Restricted Bands Below 2 GHz ~ , _ Frequencies in MHz _ _ _ . : .
0.090-0.110 162.0125-167.17 -0.49-0.51 167.72-173.2
8PEC~ D LE~Y T~AN8MI88ION LINE
Fiel~ Of The Inventio~
The present invention relates generally to radio communication systems and, more particularl~, to radio communication systems employing spread spectrum and S radiating transmission line technologies.
,~ .
Baclc~roun~ Of The Invention Spread spectrum technology has been known for some time. A spread spectrum system is one in which the transmitted slgnal is spread over a wide frequency band.
Typically, the frequency band over which the transmitted signal is spread is wider, by a substantial margin, than the minimum bandwidth required to transmit the information being sent. For example, a spread spectrum system may convert a base-band signal having a bandwidth of a few kilo-Hertz (kHz) to a spread spectrum signal having a -- bandwidth of many Giga-Hertz (GHz), and transmit the signal using that wider bandwidth.
Spread ~spectrum signals are typically generated using , 20 - code-modulation such as frequency hopping or direct sequence coding. Becau$e of this code modulation, the - _~ower transmitted i9 low in any narrow frequency region.
he power density of a spread spectrum signal is far less =- than that of more conventional signals in which all the transmitted power is sent in a band of frequencies commensurate with the baseband information bandwidth.
WO91/15068 PCT/~'S91/017~"~
Z C ~ ~ 2 Spread spectrum communication provides a number of advantages over more conventional types of communication systems. These advantages include selective addressing capability, coupled access for code division multiplexing, message screening from eavesdroppers and low-density power spectra for signal hiding. These characteristics are useful and highly desirable in many types of radio communication systems. These and other characteristics of , spread spectrum technology are described in SPREAD SPECTRUM
SYSTEMS, edited by Robert C. Dixon, published by John Wiley & Sons, Inc. (1984). ;
For purposes of background information dealing with ~ ~
conventional spread spectrum systems, as well as for l `
supplemental information dealing with modular yet 15 conventional segments of the illustrative embodiments set I i I ,.
forth herein, the reader's attention is directed to the 'I
following references: U.S. Pat. Nos. 4,'455,651, and 4,086,~504, dealing with wireless systems employing spread spectrum techniques; U.5. Pat. No. 4,438,5'19, dealing with ~20 a narrow-bandwidth spread spectrum system using an AC power - line as an antenna; U.S. Pat. No. 4,475,iO8,~concerning a voiceldata spread spectrum system; U.S.'Pat. No.- 4,320,514, dealing with a spread spectrum radio receiver ~or frequency hopped signals; and U.S. Pat. No. 4,'672,605,- dealing with a'"''L~ 25 data/voice communication system based on'spe~trum spreading. ~ ~
One rather unique type of radio aommunication system ~ ' employs a radiating (or "leaky") transmisslon line, such as , ' ~'091/1506~ ~ PCT/US91/01779 . . ~
leaky coaxial cable, throughout a confined area to provide -coverage in that~area. Leaky transmission line is advantageous, because it provides for total aoverage of a restricted area. Thus, it is not uncommon to find leaky transmission line in tunnels, offices and other areas that are frequency-blocked from externally located wide area coverage communication systems.
Combining leaky transmission line with spread spectrum technology in a single system, to realize the advantages of lO both technologies, has been recognized as a worthwhile ;
objective. For example, in U.S. Patent No. 4,866,732 these technologies are described as part of a single system having radio units communicating over a radiating ¦
transmission line, with each radio unit communicating using lS~ a uniquely~;assigned spreading code. Unfortunately, there are probiems associated with the implementation of this ¦ `~
technological combination which have not been overcome. ;~
A fundamental problem with such a system involves regulations defined by~the Federal Communications Commission~ (FCC). The FCC has allocated certain bands for use of spre~ad~spectrum radio transmLssions having a power level of up to one Watt. These FCC bands~are commonly -~
referred to as the Industrial, Scientiflc and Medical (ISM) bands and are respectively assigned to the frequency ranges of 902-928 MHz, 2400-2483.5 MHz and= 5-7~5-5850 MHz.
. . .
Although operation at 2400-2483.5 MHz is conceivable with leaky coaxial cable, there remains a- number of unsolved problems concerning coupling losses and attenuation in WO91~15068 PCT/~S91/01779 a -~
4 ~-leaky coaxial cable at this frequency. Moreover, due to attenuation, leaky coaxial ca~le is not typically useful - ;;
for frequency transmissions in excess of 2 GHz. Thus, the most practical ISM band is in the 902-928 MHz region.
The 26 MHz bandwidth in the 902-928 MHz region is, however, narrow and complicates full-duplex spread spectrum communication over leaky coaxial cable. This is because a 26 MHz bandwidth does not allow for the provision of sufficient isolation between the transmit and receive 10 signals without the aid of extènsive filtering tools, which ~ ~
can be expensive and occupy an excessive amount of space. -Accordingly, there is a need for a spread spectrum -communication system using leaky coaxLal cable that can be ;~
implemented in a cost effective manner while overcoming the 1, ',"
15 afore-mentioned problems. ! ~
~,,, ummary Of The In~ontion It is a general object of the present invention to provide a spread spectrum communication system which uses leaky transmission line to provide communication in a prescribed communication coverage area. ~`
It is a more specific object of the present invention to provide a full-duplex spread spectrum communication system using leaky coaxial cable to provide communication within the guidelines established by the FCC in a cost-effective and space-conscious manner. `
According to a preferred embodiment, the present invention provides a communication system comprising a leaky transmission line coupled to a transceiver for providing two-way radio coverage in separated first ~n~
second frequency bands. The leaky transmission line is used for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area, and the transceiver is used for providing spread spectrum signals to the leaky transmission line in a first frequency band and at-a first predetermined power level. A plurality ~ of radio units, situated within the prescribed coverage area, receive the spread spectrum signals transmitte~ f~o~
the leaky transmission line in the first frequency band and transmit spread spectrum signals to the transceiver, via -~ the leaky transDission line, in the second frequenc~u~
These bands are selected with respect to the transmission 15~ restrictions set forth by the FCC. Further, the leaky transmission line decreases the power level of the spread spectrum signals provided by the transceiver means to a second preselected power Ievel so as not to encroach the I `
guidelines set forth by the FCC concerning spread spectrum 20 ~ ~signals.
~; Preferably, the power level of the signals leaving the transceiv~er is set, according to the couplinq and attenuation losses of the cable, so as to maximize the power level of the signals rad~ating from the ca~le without ~: h: .
exceeding the threshold. It i8 in this manner that the leaky transmission line may be used to decrease the power }evel of the spread spectrum signals provided by the transceiver means to the second preselected power level.
WO91/1~068 ~ PCT/~'S91/01779 . ~
Brief De~cription Of The Drawina~
Other objects and ad~antages of the present invention will become apparent upon reading the following detailed ~`
description and upon reference to the drawings in which~
S FI~. 1 is a block diagram of a radio communication system, illustrating one embodiment of the present ` f invention; and FIG. 2 is a block diagram of another radio communication system, illustrating other aspects of the , .
preæent invention~
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereo~ have been shown by way of example in the drawings and will herein be described in detail. It should be ~understood, howèver, that it is not intended to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, quivalents~, and alternatives falling within the spirit and .,. ,~;
~ scope o~f the invention as definèd~by-the app-nded claims. i`
:~ ~ : ;~
;~
... ~
. . ' , . ..
~: . .
-- . .
.~ : ': , .
: ~' ~, Wo91/15068 z ~ PCTJ~!S91/0~779 Detaile~ Description Of T~e PrQferred Embodiment~
The present invention is directed to spread spectrum communication systems employing radiating (or leaky) transmission lines, e.g., ~eaky coaxial cables for two-way radio communication, for example, full-duplex or half-duplex communication. Because of certain problems that are ;
solved by the present invention, it is especially suited for a spread spectrum system providing full-duplex communication in narrow coverage areas.
10Referring now to FIG. l, the present invention is illustrated in the form of a radio communication system having radio units 12 and a control station 18. Actual coupling of radio frequency (RF) signals between the I, control station 18 and the radio units 12 can be accomplished in several ways. By way of illustration only, .:
the representative system of FIG. l includes a repeater 14, which may be a transceiver or translator, and a leaky transmission line 16 for-such coupling. The repeater 14 may include a conventional bi-directional amplifier and transceiver means (not shown) suitable for transmission of - , . .. . .
the spread spectrum signàl.~ These elements are used to provide two-way radio communication from the control station 18 to the radio units 12 in a first radio frequency band (Fl), and in a second~freguency band tF2) from the ~- 25 radio units 12 to the co~tro~-station 18. More specifically, the leaky transmission line is in the form of radiating cable of either the slotted type or other form wherein the slots or other openings disposed on the ;
WO91~1506~ PCT/~!S91/01 79 metallic outer conductor of the cable permit a controlled portion of the electromagnetic signals being transmitted therethrough to propagate along the length of the ca~le so that any radio units 12 disposed in the vicinity of such leaky transmission line may receive the signals being radiated therefrom. The leaky transmission line approach is particularly advantageous in bi-directional communication systems because electromagnetic signals transmitted near the transmission line lengths are coupled into the radiation slots and carried back along the length of the cable to the control station. I
Accordingly, RF signals transmitted by mobile or r~`
portable radio units in the RF coverage area of the control ¦ ~
.~
station 18 can be picked up directly by the leaky 15 transmission line 16 and relayed to the control station 18. Ii , Signals transmitted from the control station 18 to the radio units 12 travel in essentially the opposite manner.
In a similar arrangement, by using other repeaters 14, the control station 18 can also link radio units 12 in different coverage areas defined by respective leaky transmission lines 16. This configuration is useful in a number of different kinds of two-way radio systems. For example, it may used in cellular telephone communication or trunked radio communication, or in vehicle telemètry ¦ `
applications where a test vehicle ~e.g., auto, bus, military wheeled or track vehicle) is connected to a data acquisition computer using spread spectrum radio communications over leaky transmission line. Another WO91/1~068 Z ~ - PCT/~!S91/01779 application is in a factory, office or institution where leaky transmission line is distributed therethrough to provide the necessary coverage.
- In the second frequency band, communication from the radio unit 12 to the control station 18 may be implemented using conventional spread spectrum technology at conventional power levels. For example, this signal path may include either direct sequence or frequency hopping - type spread spectrum communication where the signals are transmitted in the 902-928 MHz region and at conventional power levels into the leaky transmission line 16. This ;
implementation is consistent with FCC frequency band allocations for spread spectrum transm~issions, as the 902-92~8 MHz~region is one of the ISM bands allocated for spread spectrum use by the FCC.
In the first frequency band, radio signal , .
.
~ communication is implemented from the control station 18 to .
the radio units 12 without interfering with the signals in the æecond frequency band and without exceeding FCC ~ L' restrictions. Based on the spreading factor, spread spectrum communication can spread the signal over the ~ ~
entire frequency band. In addition, based on available - -~~-bandwidth of the frequency band, it is possible to provide ~ for diff-rent spreading factors up to that factor that will ---- ``
spread the signal over the entire band. This causes both _ _-transmit and receive si~nals to interfere with one another if they are carried simultaneously in a single 26 MHz region, such as the desirable 902-928 MHz region which is WO91/15068 ~ PCT/US91/01779 10 - .
the most practical region. As will be discussed, FCC
requirements restrict use of frequencies outside the ISM
bands.
The present invention overcome~ this problem, through ;~-proper selection of the frequency bands and appropriate power level selection. With the second frequency band assigned to the 902-928 MHz region, the first frequency band is selected in one of two ways. First, it can be selected from a region outside of those bands which are designated as restricted by the FCC (i.e., a non-restricted region). Second, it can be selected as the 2400-2483.5 MHz ISM band if consideration is given to increase power to overcome attenuation and coupling loss. Within that non- `~
restricted region, the transmitted signal power level is 15 maximum at the point that the signal is coupled to the ¦
leaky transmission line to the extent possible without exceeding the FCC power restrictions concerning intentional radiators. Within the 2400-2483.5 MHz ISM band, consideration is~given to increasing the power level of the signal in order to increase the length of the leaky transmission~line and/or to increase the distance between the leaky transmission line and the radio units.
The following tables, Tables l and 2, are provided to illustrate how~the first frequency band may be selected. ;
25 Tables l and~-Z-respectively list the FCC restricted bands ~
-- , ~
below 2 GHz and the available (or non-restricted) frequency bands for intentional radiation between 960 MHz and 2.2 GHz.
WO91/1~068 X~ PCT/US91/01779 Table 1: FCC Restricted Bands Below 2 GHz ~ , _ Frequencies in MHz _ _ _ . : .
0.090-0.110 162.0125-167.17 -0.49-0.51 167.72-173.2
2.1735-2.19~5 240-285 .
8.3~2-8.366 322-335.4 13.36-13.41 399.9-410 25.5-25.67 608-614 37.5-38.25 960-1240 :
73-75.4 1300-1427 :
108-121.94 1435-1626.5 1~3-138 1660-1710 149.9-150.05 1717.8-1722.2 :~
156.7-156.9 ~.
. . .
. ~
Table 2: Non-restricted Bands Between 960 MHz and 2.2 GHz ~-....
;-~
Available Band Bandwidth Frequency in MHz in MHz . ~ .
_ _ "~
: 1626.5-1660 33.5 1710-1717.8 7.8 1722.2-2200 477.8 Preferably, the first frequency band, for transmission .~
to the radio units 12, is selected from this set of bands in Table 2.~
:
- Maximizing-the transmitted signal power level at the .
point that the signal is coupled to the leaky transmission . .
line requires the acknowledgement of two parameters. These :~
.
, are the FCC power restrictions concerning spread spectrum - . _ --- - -- :
radio t-ransmissions and the losses associated with the leaky transmission line. Presently, the FCC power _ restrictions are based on a limit of power delivered to the antenna. This restriction is sometimes interpreted as the U~091/1~068 ~ PCT/U~1/0]779 equivalent of a signal field strength at a distance of three meters from the antenna. Due to losses associated with leaky transmission line, when u~ing leaky coaxial cable rather than an antenna, the power delivered to the j i 5 antenna (or leaky transmission line) does not correspond `
directly to the signal field strength at a distance of three meters. Thus, it possible to deliver more power to the leaky coaxial cable than to other more conventional antenna-like devices. In any case, the signal loss through the leaky transmission line should be calculated and this power level implemented accordingly. ~-With regard to the losses associated with leaky transmission line, there are two primary characteristics - that define such losses. ~These characteristics are attenuation and coupling loss. Attenuation is the measure of the signal Ioss along the cable, and it is normally specified in decibels (dB) per lO0 feet. Attenuation values range from fractional parts of l dB at low -frequencies for large cable sizes to above ll dB for hlgher frequencies for small cable sizes.
Coupling loss is related to the measure of the signal which is radiated from the leaky coaxial cable and is defined as the difference between the signal level in the cable and the signal level received by a 0 dB gain~`antenna.
2S Coupling loss is commonly specified in dB at a s~ecl~fied `~ distance typically, 20-feet or approximately 6.l meters, from the cable. Coupling loss varies significantly along the length of the cable due to the geometry of the location WO9]/15068 Z ~J ~ PCT/US91/01779 in which it is mounted. Conventional cables have coupling losses greater than 50 dB, and loss values are commonly in the range of 60 to 90 dB. Generally, lower coupling values result in higher internal/longitudinal attenuation. .
Table 3 (below) lists the attenuation and coupling losses for popular RADIAX0 cables available from Andrew Corp., Orland Park, Illinois.
WO 91/l5068 ~ PCr/~'S91/01-79 `14 Table 3 Attenuation and Coupling Losses .
for Popular Andrew RADIAX~ Cables .
_ . !., Cable Type Frequency Attenuation Coupling Loss at 20 ft MHz dB/100 ft dB ~;
RX1-2 30 1.1 57 150 3.1 55 450 6.6 64 ~:
900 9.6 67 :
1700 Not Recommended Not Recommended RXL2-2 30 0.65 65 150 1.6 56 900 4.3 68 1700 6.3 74 `:
~ ' RXL4.-1 1 30 O.33 62 lS0 0.94 : 58 450 2.1 63 900 3.4 68 1700 5.6 73 _ I .
RXL5-1 30 0.21 65 lS0 0.54 58 450 1.1 63 : 900 1.9 69 1700 3.1 72 :
. ~,:
~RXL6-1 30 0.17 68 150 0.39 59 450 0.80 66 ~ ~:
: . 9OO 1.4 71 1700 2.3 73 RXL7.--1- 30 O.lS 63 : ~~ ~~ lS0 0.33 61 - 450 0.61 68 -. . . goO 1.0 72 1700 2.7 77 .
~ . . , ~.
..
.~ .
.. I
. ~
WO91/1~068 2~ 3~ PCT/US91/017~9 As will be described in detail below, thç above tables - may be used to determine the maximum signal power level at the point that the signal in the first frequency band is coupled from the repeater 14 to the leaky transmission line 16, in view of the FCC power restrictions. This determination may be made for any arrangement of leaky transmission line. `~
If desirable or necessary, the maximum signal power level at the point that the signal in the first frequency band is coupled from the repeater 14 to the leaky transmission line 16 may also be determined using the , `
criteria of a signal field strength at a distance of three -meters from the antenna. For example, using the FCC
intentional radiation emission limit for any given frequency, the field strength at the applicable distance from the leaky transmission line may be measured while adjusting the signal power level applied thereto from the repeater. These FCC radiation emission limits are provided `
~ below in Table 4:
Table 4 F.C.C. Intentional Radiation Emission Limits:
,, Frequency Field Strength Measurement Distance ; _1 _ _`_ MHz microvolts/meter meteræ
. .
O.009-0.490 2,400/F (kHz) 300 0.490-1.705 24,000/F (kHz) 30 l'~
-_ _-- ~1.705-30.0 30 3 -_ 30-88 lO0 3 ~ 216-960 200 3 _ Above 960 500 3 :
WO91/1~068 PCT/US91/01779 ~
~~ J~ 16 ;
Use of the above tables is demonstrated in the following example, in which a ~ink budget is calculated to provide the maximum signal power level at the point that the signal is coupled from the repeater 14 to the leaky transmission line 16. In such a calculation, three fundamental constraints should be taken into account. ~`
These are the level of signal allowed by the FCC, the maximum required distance between line repeaters (amplifiers), and the maximum required standoff distance from the leaky feeder for radio unit coverage; each is properly considered in the example.
The example includes the first frequency band being selected from Table 2 as the 1240-1300 MHz (1250 MHz) band, and the second frequency band being selected as the 902-928 MHz ISM band. Thus, Table 4 would require a signal strength of no more than 500 microvolts/meter (~V/m) at 3 !`
meters from the leaky transmission line. This restriction for-the 1240-1300 MHz band is defined by the FCC in Part l5, Subpart C -Intentional Radiators, section 15.209, as 500 ~V/m at 3 meters. Further, assuming the use of l-l/4 inch leaky feeder (e.g., Andrew Corporation RXL-6 Radiax~), a coaxial mode power of approximatel-y--l7 dBm will result in a field strength of 500 ~V/m at 3 meters. At 1250 MHz, .
the longitudinal attenuation of this leaky feeder is 6.0 dB
per lO0 meters, and the coupling_ioss at 20 feet (6.l meters) is 72 dB. For a radio unit~receiver sensitivity of --102 dBm, the following link budget for the repeater (amplifier) to radio unit path is derived assuming the worst càse conditions of being at the farthest point from an amplifier and a 5 dB null in the leaky feeder.
Line Amplifier Output Power - 17.0 dB~
RADIAX~ Attenuation for lO0 feet - l.8 dB
RADIAX~ Coupling Lo8s at 20 feet - 72.0 dB
Coupling Loss Yariation - 5.0 dB - `
Signal Power at Radio Unit - 95.8 d8m Receiver Sensitivity -102.0 dBm The difference between the signal power at the radio lO unit and the receiver sensitivity is 6.2 dB; this is the ~;
"link margin," which permits an overall variation from these calculations of up to 6.2 dB, while ensuring reception by the radio units at distances of not more than 20 feet from the leaky transmission line. `
In FIG. 2, another radio communication arrangement using leaky transmission line is illustrated in accordance with the present invention. This arrangement is similar to that shown in FIG. 1 and includes common elements. The control station 18 in FIG. 2 may be viewed as incorporating the repeaters 14 referred to in connection with FIG. l.
Two additional elements, not shown in FIG. 1, are a non- ;
leaky length of transmission line 22 and a conventional amplifier 20. ~The non-1eaky-length of transmission line 22 is useful for areas in which ~radio unit coverage is not necessary.
Each amplifier 20 is-uoed to boost the level of the signals traveling in the= ~aky transmission line 16 to provide maximum signal power levels without exceeding FCC
power restrictions. Due to the coupling and attenuation losses which are inherent to the leaky transmission line, WO 91/15068 PCT/~!S91/01779 ~ ~ J ~
these amplifiers 20 may be required depending on the lengths of each leaky transmission line 16.
Also included in FIG. 2 is a conventional power meter 24 for measuring the signal strength at a specified , 5 distance from the leaky transmission line 16. Such ;~
measurements may be used to implement the power levels in accordance with the FCC radiation emission limits (as listed above in Table 4), with each amplifier 20 being adjusted to meet the FCC guidelines.
- Alternatively, interpreting the FCC spread spectrum power restrictions as limiting the power delivered to the antenna to be the equivalent of that which will produce a given signa} field strength at a predetermined distance ; from the leaky transmission line 16, each amplifier 20 may ¦
be adjusted to amplify the signa}s such that it compensates for the losses in the leaky transmission line 16. Such an interpretation may be used to deli~er more than one Watt of signal power to the leaky transmiæsion line 16. This additional power allows for an increased distance between the amplifiers 20, and, therefore, makes the system more -~ practical for operation-in the 2400-2483.5 MHz ISM band.
The following example demonstrates the maximum distance between amplifiers 20 for a spread spectrum system ; using the 2400-2483.5 MHz ISM band for the first frequency ~ 25 band (communication to the radio units), and the 902-928 ; MHz ISM band for the second frequency band tcommunication from the radio units). The allowable signal level for spread spectrum operation in the 2400-2483.5 MHz ISM band 2~ `3~3 ~
WO 91/15068 PC'r/~lS91/01779 is defined in Part 15, Subpart C - Intentional Radiators, ;~
Section 15.247, as one Watt. As in the previous example, the maximum required longitudinal distance between line amplifiers, and the maximum required standoff distance from the leaky feeder for radio unit coverage are accounted for in the example itself.
In this example, a 1-1/4 inch leaky transmission line (e.g., Andrew Corporation RXL-6 Radiax~) is used for the répeater (amplifier) to radio unit communications path at ` ~
10 2400 MHz. At 2400 MHz, the longitudinal attenuation of ~.
this leaky feeder is 10.05 dB per loO meters and the t~ -coupling loss at 20 feet (6.1 meters) is 74 dB. For a receiver sensitivity of -102 dBm, the following repeater¦ !
(amplifier) to radio unit communications path link budget is derived.
~ ,.
Line Amplifier Output Power + 30.0 dBm - RADIAX~ Attenuation for 1230 feet - 37.7 dB
RADIAX~ Coupling Loss at 80 feet - 86.0 d8 ;~ Coupling Loss Variation - 5.0 dB
Signal Power at Radio Unit - 98.7 dBm Receiver Sensitivity -102.0 dBm In this example, the link margin is 3.3 dB with - reception by the radio units at distances from the leaky transmission line of 80 feet or less. Although this example includes introducin~ to the leaky transmission line a spread spectrum signal~having a power level of only one Watt, using additional power will allow for more distance~ -between the amplifiers and/or greater distance between the leaky transmission line and the radio units.
~'091/1~068 PC~S91/01779 2 ~ J -~ ; 20 Accordingly, the present invention realizes a ~ practical i~plementation of a communication system which uses and enjoys all the advantages associated with both leaky transmission line and spread spectrum communication.
,i"
Not only is this invention well suited for any leaky coaxial arrangement, reduced costs are realized in larger application using the additional power that is available in the previously discussed interpretation of the FCC
- restrictîons for spread spectrum communication.
While the invention has been particularly shown and described with reference to various embodiments, it will be ~' ~r recognized by those skilled in the art that other modifications and changes may be made to the present invention described above without departing from the spirit and scope thereof. As an example, other bands could be used in place of those discussed above in connection wi~h FIGS. l and 2. More specifically, the present invention contemplates using the 906-928 MHz ISM band for communication from the radio units, and using the 906-928 MHz ISM band for communication to the radio units.
- . ~
. - .
8.3~2-8.366 322-335.4 13.36-13.41 399.9-410 25.5-25.67 608-614 37.5-38.25 960-1240 :
73-75.4 1300-1427 :
108-121.94 1435-1626.5 1~3-138 1660-1710 149.9-150.05 1717.8-1722.2 :~
156.7-156.9 ~.
. . .
. ~
Table 2: Non-restricted Bands Between 960 MHz and 2.2 GHz ~-....
;-~
Available Band Bandwidth Frequency in MHz in MHz . ~ .
_ _ "~
: 1626.5-1660 33.5 1710-1717.8 7.8 1722.2-2200 477.8 Preferably, the first frequency band, for transmission .~
to the radio units 12, is selected from this set of bands in Table 2.~
:
- Maximizing-the transmitted signal power level at the .
point that the signal is coupled to the leaky transmission . .
line requires the acknowledgement of two parameters. These :~
.
, are the FCC power restrictions concerning spread spectrum - . _ --- - -- :
radio t-ransmissions and the losses associated with the leaky transmission line. Presently, the FCC power _ restrictions are based on a limit of power delivered to the antenna. This restriction is sometimes interpreted as the U~091/1~068 ~ PCT/U~1/0]779 equivalent of a signal field strength at a distance of three meters from the antenna. Due to losses associated with leaky transmission line, when u~ing leaky coaxial cable rather than an antenna, the power delivered to the j i 5 antenna (or leaky transmission line) does not correspond `
directly to the signal field strength at a distance of three meters. Thus, it possible to deliver more power to the leaky coaxial cable than to other more conventional antenna-like devices. In any case, the signal loss through the leaky transmission line should be calculated and this power level implemented accordingly. ~-With regard to the losses associated with leaky transmission line, there are two primary characteristics - that define such losses. ~These characteristics are attenuation and coupling loss. Attenuation is the measure of the signal Ioss along the cable, and it is normally specified in decibels (dB) per lO0 feet. Attenuation values range from fractional parts of l dB at low -frequencies for large cable sizes to above ll dB for hlgher frequencies for small cable sizes.
Coupling loss is related to the measure of the signal which is radiated from the leaky coaxial cable and is defined as the difference between the signal level in the cable and the signal level received by a 0 dB gain~`antenna.
2S Coupling loss is commonly specified in dB at a s~ecl~fied `~ distance typically, 20-feet or approximately 6.l meters, from the cable. Coupling loss varies significantly along the length of the cable due to the geometry of the location WO9]/15068 Z ~J ~ PCT/US91/01779 in which it is mounted. Conventional cables have coupling losses greater than 50 dB, and loss values are commonly in the range of 60 to 90 dB. Generally, lower coupling values result in higher internal/longitudinal attenuation. .
Table 3 (below) lists the attenuation and coupling losses for popular RADIAX0 cables available from Andrew Corp., Orland Park, Illinois.
WO 91/l5068 ~ PCr/~'S91/01-79 `14 Table 3 Attenuation and Coupling Losses .
for Popular Andrew RADIAX~ Cables .
_ . !., Cable Type Frequency Attenuation Coupling Loss at 20 ft MHz dB/100 ft dB ~;
RX1-2 30 1.1 57 150 3.1 55 450 6.6 64 ~:
900 9.6 67 :
1700 Not Recommended Not Recommended RXL2-2 30 0.65 65 150 1.6 56 900 4.3 68 1700 6.3 74 `:
~ ' RXL4.-1 1 30 O.33 62 lS0 0.94 : 58 450 2.1 63 900 3.4 68 1700 5.6 73 _ I .
RXL5-1 30 0.21 65 lS0 0.54 58 450 1.1 63 : 900 1.9 69 1700 3.1 72 :
. ~,:
~RXL6-1 30 0.17 68 150 0.39 59 450 0.80 66 ~ ~:
: . 9OO 1.4 71 1700 2.3 73 RXL7.--1- 30 O.lS 63 : ~~ ~~ lS0 0.33 61 - 450 0.61 68 -. . . goO 1.0 72 1700 2.7 77 .
~ . . , ~.
..
.~ .
.. I
. ~
WO91/1~068 2~ 3~ PCT/US91/017~9 As will be described in detail below, thç above tables - may be used to determine the maximum signal power level at the point that the signal in the first frequency band is coupled from the repeater 14 to the leaky transmission line 16, in view of the FCC power restrictions. This determination may be made for any arrangement of leaky transmission line. `~
If desirable or necessary, the maximum signal power level at the point that the signal in the first frequency band is coupled from the repeater 14 to the leaky transmission line 16 may also be determined using the , `
criteria of a signal field strength at a distance of three -meters from the antenna. For example, using the FCC
intentional radiation emission limit for any given frequency, the field strength at the applicable distance from the leaky transmission line may be measured while adjusting the signal power level applied thereto from the repeater. These FCC radiation emission limits are provided `
~ below in Table 4:
Table 4 F.C.C. Intentional Radiation Emission Limits:
,, Frequency Field Strength Measurement Distance ; _1 _ _`_ MHz microvolts/meter meteræ
. .
O.009-0.490 2,400/F (kHz) 300 0.490-1.705 24,000/F (kHz) 30 l'~
-_ _-- ~1.705-30.0 30 3 -_ 30-88 lO0 3 ~ 216-960 200 3 _ Above 960 500 3 :
WO91/1~068 PCT/US91/01779 ~
~~ J~ 16 ;
Use of the above tables is demonstrated in the following example, in which a ~ink budget is calculated to provide the maximum signal power level at the point that the signal is coupled from the repeater 14 to the leaky transmission line 16. In such a calculation, three fundamental constraints should be taken into account. ~`
These are the level of signal allowed by the FCC, the maximum required distance between line repeaters (amplifiers), and the maximum required standoff distance from the leaky feeder for radio unit coverage; each is properly considered in the example.
The example includes the first frequency band being selected from Table 2 as the 1240-1300 MHz (1250 MHz) band, and the second frequency band being selected as the 902-928 MHz ISM band. Thus, Table 4 would require a signal strength of no more than 500 microvolts/meter (~V/m) at 3 !`
meters from the leaky transmission line. This restriction for-the 1240-1300 MHz band is defined by the FCC in Part l5, Subpart C -Intentional Radiators, section 15.209, as 500 ~V/m at 3 meters. Further, assuming the use of l-l/4 inch leaky feeder (e.g., Andrew Corporation RXL-6 Radiax~), a coaxial mode power of approximatel-y--l7 dBm will result in a field strength of 500 ~V/m at 3 meters. At 1250 MHz, .
the longitudinal attenuation of this leaky feeder is 6.0 dB
per lO0 meters, and the coupling_ioss at 20 feet (6.l meters) is 72 dB. For a radio unit~receiver sensitivity of --102 dBm, the following link budget for the repeater (amplifier) to radio unit path is derived assuming the worst càse conditions of being at the farthest point from an amplifier and a 5 dB null in the leaky feeder.
Line Amplifier Output Power - 17.0 dB~
RADIAX~ Attenuation for lO0 feet - l.8 dB
RADIAX~ Coupling Lo8s at 20 feet - 72.0 dB
Coupling Loss Yariation - 5.0 dB - `
Signal Power at Radio Unit - 95.8 d8m Receiver Sensitivity -102.0 dBm The difference between the signal power at the radio lO unit and the receiver sensitivity is 6.2 dB; this is the ~;
"link margin," which permits an overall variation from these calculations of up to 6.2 dB, while ensuring reception by the radio units at distances of not more than 20 feet from the leaky transmission line. `
In FIG. 2, another radio communication arrangement using leaky transmission line is illustrated in accordance with the present invention. This arrangement is similar to that shown in FIG. 1 and includes common elements. The control station 18 in FIG. 2 may be viewed as incorporating the repeaters 14 referred to in connection with FIG. l.
Two additional elements, not shown in FIG. 1, are a non- ;
leaky length of transmission line 22 and a conventional amplifier 20. ~The non-1eaky-length of transmission line 22 is useful for areas in which ~radio unit coverage is not necessary.
Each amplifier 20 is-uoed to boost the level of the signals traveling in the= ~aky transmission line 16 to provide maximum signal power levels without exceeding FCC
power restrictions. Due to the coupling and attenuation losses which are inherent to the leaky transmission line, WO 91/15068 PCT/~!S91/01779 ~ ~ J ~
these amplifiers 20 may be required depending on the lengths of each leaky transmission line 16.
Also included in FIG. 2 is a conventional power meter 24 for measuring the signal strength at a specified , 5 distance from the leaky transmission line 16. Such ;~
measurements may be used to implement the power levels in accordance with the FCC radiation emission limits (as listed above in Table 4), with each amplifier 20 being adjusted to meet the FCC guidelines.
- Alternatively, interpreting the FCC spread spectrum power restrictions as limiting the power delivered to the antenna to be the equivalent of that which will produce a given signa} field strength at a predetermined distance ; from the leaky transmission line 16, each amplifier 20 may ¦
be adjusted to amplify the signa}s such that it compensates for the losses in the leaky transmission line 16. Such an interpretation may be used to deli~er more than one Watt of signal power to the leaky transmiæsion line 16. This additional power allows for an increased distance between the amplifiers 20, and, therefore, makes the system more -~ practical for operation-in the 2400-2483.5 MHz ISM band.
The following example demonstrates the maximum distance between amplifiers 20 for a spread spectrum system ; using the 2400-2483.5 MHz ISM band for the first frequency ~ 25 band (communication to the radio units), and the 902-928 ; MHz ISM band for the second frequency band tcommunication from the radio units). The allowable signal level for spread spectrum operation in the 2400-2483.5 MHz ISM band 2~ `3~3 ~
WO 91/15068 PC'r/~lS91/01779 is defined in Part 15, Subpart C - Intentional Radiators, ;~
Section 15.247, as one Watt. As in the previous example, the maximum required longitudinal distance between line amplifiers, and the maximum required standoff distance from the leaky feeder for radio unit coverage are accounted for in the example itself.
In this example, a 1-1/4 inch leaky transmission line (e.g., Andrew Corporation RXL-6 Radiax~) is used for the répeater (amplifier) to radio unit communications path at ` ~
10 2400 MHz. At 2400 MHz, the longitudinal attenuation of ~.
this leaky feeder is 10.05 dB per loO meters and the t~ -coupling loss at 20 feet (6.1 meters) is 74 dB. For a receiver sensitivity of -102 dBm, the following repeater¦ !
(amplifier) to radio unit communications path link budget is derived.
~ ,.
Line Amplifier Output Power + 30.0 dBm - RADIAX~ Attenuation for 1230 feet - 37.7 dB
RADIAX~ Coupling Loss at 80 feet - 86.0 d8 ;~ Coupling Loss Variation - 5.0 dB
Signal Power at Radio Unit - 98.7 dBm Receiver Sensitivity -102.0 dBm In this example, the link margin is 3.3 dB with - reception by the radio units at distances from the leaky transmission line of 80 feet or less. Although this example includes introducin~ to the leaky transmission line a spread spectrum signal~having a power level of only one Watt, using additional power will allow for more distance~ -between the amplifiers and/or greater distance between the leaky transmission line and the radio units.
~'091/1~068 PC~S91/01779 2 ~ J -~ ; 20 Accordingly, the present invention realizes a ~ practical i~plementation of a communication system which uses and enjoys all the advantages associated with both leaky transmission line and spread spectrum communication.
,i"
Not only is this invention well suited for any leaky coaxial arrangement, reduced costs are realized in larger application using the additional power that is available in the previously discussed interpretation of the FCC
- restrictîons for spread spectrum communication.
While the invention has been particularly shown and described with reference to various embodiments, it will be ~' ~r recognized by those skilled in the art that other modifications and changes may be made to the present invention described above without departing from the spirit and scope thereof. As an example, other bands could be used in place of those discussed above in connection wi~h FIGS. l and 2. More specifically, the present invention contemplates using the 906-928 MHz ISM band for communication from the radio units, and using the 906-928 MHz ISM band for communication to the radio units.
- . ~
. - .
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A communication system, comprising:
a predetermined length of leaky transmission line for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area adjacent a selected section of said length; transceiver means, coupled to the leaky transmission line, for providing spread spectrum signals to the leaky transmission line in a first frequency band and at a first predetermined power level; and a plurality of radio units, situated within the prescribed coverage area, for receiving the spread spectrum signals transmitted from the leaky transmission line in the first frequency band and for transmitting spread spectrum signals to the transceiver means, via the leaky transmission line, in a second frequency band, wherein the first and second frequency bands are not adjacent; wherein the leaky transmission line is constructed such that its length and type decreases the first predetermined power level to a second preselected power level at said selected section, said second preselected power level being about one watt or less so as not to encroach power restrictions concerning transmission of spread spectrum signals.
a predetermined length of leaky transmission line for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area adjacent a selected section of said length; transceiver means, coupled to the leaky transmission line, for providing spread spectrum signals to the leaky transmission line in a first frequency band and at a first predetermined power level; and a plurality of radio units, situated within the prescribed coverage area, for receiving the spread spectrum signals transmitted from the leaky transmission line in the first frequency band and for transmitting spread spectrum signals to the transceiver means, via the leaky transmission line, in a second frequency band, wherein the first and second frequency bands are not adjacent; wherein the leaky transmission line is constructed such that its length and type decreases the first predetermined power level to a second preselected power level at said selected section, said second preselected power level being about one watt or less so as not to encroach power restrictions concerning transmission of spread spectrum signals.
2. A communication system, according to claim 1, wherein the leaky transmission line includes a coaxial cable perforated with slot-like apertures.
3. A communication system, according to claim 1, wherein the transceiver means includes an amplifier for amplifying the spread spectrum signals before they are transmitted to the radio units through the leaky transmission line.
4. A communication system, according to claim 1, wherein the radio units include mobile radios.
5. A communication system, according to claim 1, wherein the radio units include portable radios.
6. A communication system, according to claim 1, wherein the second frequency band is between 902 MHz and 928 MHz, and the first frequency band is a non-restricted band between 1240 MHz and 2200 MHz.
7. A communication system, according to claim 6, wherein the leaky transmission line is designed to propagate signals at frequencies less than about 2200 MHz.
8. A communication system, according to claim 6, wherein the second frequency band is between 902 MHz and 928 MHz and the first frequency band is between 2400 MH2 and 2483.5 MHz.
9. A communication system, according to claim 6, wherein the spread spectrum communication between the radio units and the transceiver means includes frequency hopping coding.
10. A method of communication between a radio unit and a transceiver, comprising the steps of:
providing a transmission line, including a leaky transmission line, for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area, said transmission line having coupling loss and attenuation loss factors associated therewith;
selecting a first predetermined power level as a maximum level-for signals transmitted from the leaky transmission line;
determining a second predetermined power level, as a function of the first predetermined power level and said coupling loss and attenuation loss factors, as a maximum level for signal transmission from the repeater;
coupling the transceiver to the leaky transmission line to provide spread spectrum signals to the leaky transmission line in a first frequency band and at the second predetermined power level; and situating the radio unit within the prescribed coverage area to receive the spread spectrum signals transmitted from the transceiver via the leaky transmission line and to transmit spread spectrum signals to the transceiver means via the leaky transmission line in a second frequency band.
providing a transmission line, including a leaky transmission line, for receiving, propagating and transmitting spread spectrum radio signals in a prescribed coverage area, said transmission line having coupling loss and attenuation loss factors associated therewith;
selecting a first predetermined power level as a maximum level-for signals transmitted from the leaky transmission line;
determining a second predetermined power level, as a function of the first predetermined power level and said coupling loss and attenuation loss factors, as a maximum level for signal transmission from the repeater;
coupling the transceiver to the leaky transmission line to provide spread spectrum signals to the leaky transmission line in a first frequency band and at the second predetermined power level; and situating the radio unit within the prescribed coverage area to receive the spread spectrum signals transmitted from the transceiver via the leaky transmission line and to transmit spread spectrum signals to the transceiver means via the leaky transmission line in a second frequency band.
11. A method of communication, according to claim 10, wherein the first and second frequency bands include different ratios of modulated signal bandwidth to the spread spectrum signal bandwidth.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/496,774 | 1990-03-21 | ||
| US07/496,774 US5018165A (en) | 1990-03-21 | 1990-03-21 | Communication system using spread spectrum and leaky transmission line |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2054198A1 CA2054198A1 (en) | 1991-09-16 |
| CA2054198C true CA2054198C (en) | 1994-03-15 |
Family
ID=23974078
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002054198A Expired - Fee Related CA2054198C (en) | 1990-03-21 | 1991-03-15 | Communications system using spread spectrum and leaky transmission line |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5018165A (en) |
| EP (1) | EP0473776A4 (en) |
| AU (1) | AU634384B2 (en) |
| CA (1) | CA2054198C (en) |
| WO (1) | WO1991015068A1 (en) |
Families Citing this family (75)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5499265A (en) * | 1989-08-07 | 1996-03-12 | Omnipoint Data Company, Incorporated | Spread spectrum correlator |
| US5016255A (en) * | 1989-08-07 | 1991-05-14 | Omnipoint Data Company, Incorporated | Asymmetric spread spectrum correlator |
| US5199044A (en) * | 1990-05-22 | 1993-03-30 | Tokimec Inc. | System for detecting position of object having data carrier |
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-
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-
1991
- 1991-03-15 WO PCT/US1991/001779 patent/WO1991015068A1/en not_active Application Discontinuation
- 1991-03-15 EP EP19910907997 patent/EP0473776A4/en not_active Withdrawn
- 1991-03-15 AU AU76905/91A patent/AU634384B2/en not_active Ceased
- 1991-03-15 CA CA002054198A patent/CA2054198C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0473776A1 (en) | 1992-03-11 |
| EP0473776A4 (en) | 1993-02-24 |
| AU634384B2 (en) | 1993-02-18 |
| CA2054198A1 (en) | 1991-09-16 |
| AU7690591A (en) | 1991-10-21 |
| WO1991015068A1 (en) | 1991-10-03 |
| US5018165A (en) | 1991-05-21 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20030317 |