CA1209686A - Methode and system for upstream data packet time slot synchronization with downstream vbi in a two-way catv system - Google Patents

Methode and system for upstream data packet time slot synchronization with downstream vbi in a two-way catv system

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Publication number
CA1209686A
CA1209686A CA000469081A CA469081A CA1209686A CA 1209686 A CA1209686 A CA 1209686A CA 000469081 A CA000469081 A CA 000469081A CA 469081 A CA469081 A CA 469081A CA 1209686 A CA1209686 A CA 1209686A
Authority
CA
Canada
Prior art keywords
signal
headend
control code
time slots
subscriber terminal
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
Application number
CA000469081A
Other languages
French (fr)
Inventor
Richard W. Citta
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zenith Electronics LLC
Original Assignee
Zenith Electronics LLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Zenith Electronics LLC filed Critical Zenith Electronics LLC
Application granted granted Critical
Publication of CA1209686A publication Critical patent/CA1209686A/en
Expired legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/28Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/2801Broadband local area networks
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/16Analogue secrecy systems; Analogue subscription systems
    • H04N7/173Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/16Analogue secrecy systems; Analogue subscription systems
    • H04N7/173Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
    • H04N2007/17372Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal the upstream transmission being initiated or timed by a signal from upstream of the user terminal
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/16Analogue secrecy systems; Analogue subscription systems
    • H04N7/173Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
    • H04N2007/17381Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal the upstream transmission being initiated by the user terminal

Abstract

ABSTRACT OF THE DISCLOSURE
Synchronization of upstream data packet time slots with the vertical blanking interval (VBI) of a video signal transmitted downstream from the headend is provided in a two-way cable television (CATV) system. Coded data transmitted during a designated VBI line from the CATV headend is compared with system data stored in each subscriber terminal for generating a match signal. The match signal is used to interrupt a microcomputer which then divides the next video signal raster scan field into 8 equal time slots during any one of which an upstream data packet may be transmitted. Upstream data is thus accurately synchronized with a downstream vertical scan rate signal in reducing the likelihood of collisions between upstream data packets and increasing through-put in a two-way CATV system.

Description

~ac~ground of the Invention Thls invention relates generally to cable television (CATV~ systems and is particularly directed to a two-way C~TV
system in which upstream data transmission timing is provided ~y downstream headend generated signals.
CATV syste~s typically include a central master source of television programming information termed a headend which imparts programs, or groups of programs at different assigned fregu~encies, to a network of cable connections which, throuyh various distribution and selection network components, ultimately terminate in a branched out plurality of user terminals typically in resiaences or commercial establishments. CATV program signals are broaacast from the headend to individual subscribers in a "downstream" direction over different assigned carrier frequenc;es typically from about 50 to 450 MHz. The CATV headend Dot only $ransmits television programming information downstream, ~ut may also tran~mit subscriber address and authorization codes which allow for hea~end control of subscriber program decode authorization status.
In a two-way C~TV system each su~scr~ber is able to transmit signals back to the C~TV heade~d. These subscriber-originated signals may include program purchasing requests, ,,j~,;

~,~0 ~D ~

opinion poll responses, and CATV converter sta~us information.
These ~s~r~ signal~ ~ke use of o~ of band frequencies in the 5-3~.5 M~z ba~ h~ ~p~trea~ si~nal ~stribution network is in the form of a ~erging ~ree topolosly" in which the signals generated by ma~y sources, or ~u~sc~ibers, c~nverge and are transmitted ~ a single transmission line back to the CATV
headend. Such techniques as signal multiplexing and frequency diversity have been proposed and are utilized to accommodate large numb~rs of subscribers in a two-way CATV system.
In the upstream signal multiplexing approach the timing of subscriber upstream transmissions is, of course, critical particularly in CATV systems having large numbers of 5 ubscribers. Some prior art two-way CATV systems utilize a polling arrangement in which headend generated timing signals typically provided during the vertical blanking ~nterval (VBI~
are used to initiate the sequentially timed upstream transmissions of the system subscribers. U.S. Patent No.
3,769,579 to Harney discloses a CATV system in which each television receiver has a transponder. The transponders are 2Q all interrogated by a common start signal, following which a series of clock pulses are provided to the various,transponders for controlling their responses. The various periods of reply of the transponders are se~uential, with the periods being controlled by the clock signals so that predetermined groups of television receivers reply during predetermined time intervals. The replies from each of the interrogated transponders occur in the period between vertical blanking intervals. U.S. Pate~t ~o~ 3,882,392 also to Harney discloses another approach to synchronizing s~'bscriber upstream transmissions in a subscription television systern. In this approach the central station (headend) clock is derived frorn local power frequency and the clock signals at each receiver are derived from the power frequency at the local receiver.
Thus, in a hotel or motel situation where the subscription television sys~em o~erate~ fro~ a sln~le power source, the central sta~ion an~ ~11 the re~eivers will operate oEf of the in-phase local power and the clock signals at both the central station and each receiver will ~e synchronized. The former approach requires that a transponder be provided for each subscriber, while the latter approach is intencled for a television signal distribution system having a common power source which is impractical for most CATV systems which cover large geographic areas and encompass large numbers of subscribers.
A second approach taken in two-way CATV systems involves a contention arrangement in which simultaneous access of the shared media by two or more subscribers is resolved in a predetermined manner. For example, U.S. Patent No. ~,388,298 to Van Egmond et al discloses an arrangement in which the transmitting and receiving stages of each station are connected to the cable. The transmitter of a station reques~ing media access provides a signal of predetermined logic value on the connecting line by changing its output impedance, which logic signal automatically switches off the transmitter of each of the other staitons. Another data transmission packet contention system makes use of an approach generally termed "Aloha" which invovles the random transmission within a designated time period by those subscribers desiring shared media access. The simultaneous transmission of more than one subsc~1iber results in the collision and mutilation of data packets and unsuccess-ful headend comm~nications. This is typically followed by another random transmis3ion by the unsuccessful subscriber who may or ~L2~;
may not receive a response (acknowledgement) from the headend depending upon upstream data traffic density. In order to increase the rate of successful transmissions, the basic "Aloha" arrangement has been modified into a "slotted Aloha"
arrangement wherein the headend transmits a synchronizing signal indicating the beginning of a frame which is divided into a sequence of time slots of mutually equal lengths.
Each subscriber transmits a data packet to the headend within a given time slot which is randomly selected from the sequence of time slots. The "slotted Aloha" approach is generally twice as efficient as the basic "Aloha" arrangement in reducing the number of ups-tream data packet collisions.
One approach to a slotted "Aloha" arrangemen-t is disclosed in U.S. Patent No. 4,398,289 to Schoute wherein the main station, or headend, determines the number of time slots in the next frame based upon a determination of the number of unmutilated, emp~y and mutilated time slots in preceding frames. The number of time slots in a given frame is then transmitted as part of the synchronizing signal to each subscriber terminal.
The present invention is intended to overcome the aforementioned limitations of the prior art by providing a time-slotted "Aloha" two-way CATV system using contention techniques for upstream data communication in which upstream data transmission synchronization is based on downstream program VBI timing.
Specifically, the invention relates to a time slotted aloha two-way CATV system wherein video signals having a vertical rate signal component are transmitted downstream on a cable from a headend to a plurality of subscriber terminals and each subscriber terminal may in kh/~

~091~i turn transmit upstream data packets to the headend on the cable. The system comprises: signal detection means for detecting the vertical rate signal component and generating a timing reference signal in response thereto;
and signal processing means coupled to the signal detection means and responsive to the timing signal for dividing the next succeeding raster scan field into a plurality of equal time slots in predetermined time relations to -the timing signal in which the data packets may be inserted for upstream transmission.
In its method aspect, the invention relates to a method for providing data upstream in a two-way CATV
sys-tem from a subscriber terminal to a headend by means o;E ~ cable connec-ted -therehetween, wherein video program ~ign~ls inaludin~ ~ vertical rate sign~l and a ras-ter s~an ield a.re provided downstream from the headend to the subscriber terminal. The method comprises: detecting the vertic~l rate signal; dividing the next raster scan field into a plurality of equal time slots in times relation to the detected vertical rate signal; selectively generating a data packet synchronous with one of the time slo-ts;
and transmitting the data packet upstream to the headend in the next raster scan field within the one time slot.
Objects o~ the Invention Accordingly, it is an object of the present invention to provide improved data transmission in a two-way CATV system.
It is another object of the present invention to provide increased upstream data through-put in a two-way CATV system.

- 4a -kh/~c ~ et another object of the present invention is to accurately synchronize the upstle~m data transmissions of a plurali~y of CATV subscribers.
A further o~ject of the present invention is to control the timi~ of ~he ~pst~eam transmissions of a plurality of CATV
subscribers utilizing a regularly recurring component of the downstream program signal transmission.
Brief Description of the Drawings The appended claims set ~orth those novel features believed characteristic of the invention. However, the invention itsel~, as well as further objects and advantages thereof, will best be understood by reference to the following detailed de~cription of a preferred embodiment taken in conjunction with the accompanying drawings, in which:
` lS FIG. 1 shows partially in bl~ck diagram and partially in schematic diagram form a system for synchronizing upstream data packet time slots with downstream VBI data in a two-way CATV system in accordance with the present invention;
FIG. 2 shows the timing of vertical blanking intervals ~0 and address match latch signals genera~ed when a subscriber address match occurs;
FIG. 3 illustrates the time slot configuration for upstream d~ta packet transmissions for use in the system of FIG.
l; and FIG. 4 is a simplified flow chart showing the sequence of operations carried out by a microco~puter in ~ chronizing upstream data packet time slots with down~xeam VBI data for a two-way CAT~ system in accordance with the present invention.

~2~

Description of the Preferred Embodiment Referring to FIG. 1, there is shown in combined schematic ~n~ ~lock di~a~ ~orm a subscriber terminal 10 for a two-way C~TV system in acc~rdance with th~ present invention.
The system also includes a cable headend 12 coupled to each subscriber terminal 10 via a cable 15 and which typically includes a computer, multiple terminals, disc drives and a tape backup. These elements of the cable headend 12 are not shown in FIG. 1 as they do not form a part of the present invention.
Downstream television signals from the cable headend 12 to individual sub~cri~ers may be encoded to include such information as s~bscriber address, program authorization, and market codes a~ well as program identification data which is transmitted in tele~ision channels having frequencies between about 50 and 450 MHz. This data may be provided during the vertical blanking interval (VBI~ of the downstream video programming siynals, such as in lines 10 through 13 of the VBI as shown in Table I.
Although the present invention is described herein as making use of VBI lines 10-13 of the video programming signals for the downstream transmission of subscriber data, it is not limited to the use of these VBI lines and may utilize any portion of the vertical retrace signal including any combina~ion of VBI
lines, consecutive or nonconsecutive.
TABLE I

n-BIT
VBI Line 10 m-BIT ADDRESS CODE AUTHORIZATION CODE
n-BIT
VBI Line 11 m-BIT ADDRESS CODE AUTHORIZATION CODE
~-BIT
VBI Line 12 m-BIT ADDRESS CODE AUTHO~IZATION CVDE
VBI Line 13 x-BIT MARKET CODE y-BIT PROGRAM TAG
_ _ _ _ _ -The VBI occurs during vertical retrace of ~he raster scanned cathode ray tube (CRT) of the ~lbscriber's television receiver a~d comprises a~out 21 horizontal scanning lines.
Referrin~ ~o ~a~le I ~ er in ~ k~own on~w~y addressable CATV
system an m-bit su~scriber address code aDd ~ related n-bit program authoriz~ion cod~ are selectively transmitted during each of lines 10, 11 and 12 of ~he VBI. During line 13 of the VBI there is continuously transmitted an x-bit market code which defines those geographic area in which the system is operating i'l as well as a y-bit program identification code~ or tag, defining the a~companying television program. These downstrearn signals a~ rec~ived by each subscriber terminal 10 and coupled by a diplex filter 14 to a decoder 18 which includes a suitable tuner tuned to an encoded CATV channel. Each received m-bit address lS code is compared with a unique subscribar address code s~ored in a programmable read only memory ~PROM~ 3~ of decoder 18 in each subscriber terminal lQ. If the received subscriber address code matches the unique subscriber address code stored in the decoder's PROM 34, the program authorization code of the same VBI line is stored i~ a random access memory (RAM) 78 in decoder 18 which defines the program decode authorization status of the subscriber. A match between the received and stored address codes will also result in the generation of an address match latch (AML) pulse by decoder 18, which pulse is provided on an output line 36 of decoder 18.
The x-bit market code received during line 13 of each V~I is compared with a subscriber terminal market code also stored in the decoder's PROM 34. A match between the transmitted and stored ma~ket ~des wi~l enable t~te decoder 18 and also result in the generation of an address match latch (AML) pulse which is also provided on line 36. A match between the received y-bit program tag code and the stored program decode authorization status p~rm~ts the ~ecoder to desc~mble the received CATV vide~ progr~m~ing signal ~lich may then be viewed on the subscrlber's television recei~er ino~ sh~n). The absence of a match between the received program ~ag code a~d the stored program authorization status results in the video programming signal being passed on by the subscriber terminal 10 in a scrambled fDrm.
As previously mentioned, each match be~ween a received subscriher address co~e a~d the unique subscriber address code sto~ed in PROM 34 of decoder 18 result~ in an AML
pul~e on line 36 as does each match hetween a received market code and the stored market code. Since a market code initiated ~ML pulse is generated during horizontal line 13 of each VBI, a highly reliable vertical rate signal is produced on line 36.

According to the present invention, this vertical rate signal is used to synchronize the time slots used for upstream data transmission from all of the subscriber terminals 10 to the headend 12.
With further reference to FIG. 1~ the AML pulses developed on line 36 by decoder 18 are coupled to a binary counter 22 and to a one-shot monostable multivibrator 24.
Various other signals are also output by decoder 18. These signals include keystroke serial data provided via line 38 to a microcomputer 20. This keystroke serial data may include such information as channel number selection, cable selection, or program authorization rerquests as provided to decoder 18 via line 23 by a subscriber input device 21. The decoder 18 is coupled to ground potential via line 40. Finally, decoder 18 provides a ~V~C output to the various components of the CATV
subscriber terminal 1~ as required.

~2~

The ~ML pulses are provided by decoder 18 to counter 22 and monostable multivibrator 24 in the form of 8 microsecond pulses ~ith a~ int~xval of ~ F~C~n~ being provided between adjacent pu~ , as ~wn in FIG. 2. As disclos~d in the referent-copending a~plication, various combinations of the AML
pulses are fo~med during each VBI by selectively transmitting appropriate address codes for selectively commanding each terminal from the headend. For example, the pulse diagram of ~IG. 2 shows three AML pulses Pl, P2 and P3 occurring during lQ the VBI of a first 16.8 millisecond field. AML pulses Pland P2 represent subscriber address code matches during VBI 10 and 11 while ~ML pulse P3 represents a market code m~tch during V~I
line 13. It will be appreciated that the market code match AML
pulse P3 cannot be used to represent any data since it is transmitted during every VBI by the headend. During the VBI
of the subsequent field, an AML pulse P4 represents an address code match during VBI line 10 and an AML pulse ~5 represents a market code match during VBI line 13.
~ he ~M~ pulses produced on line 36 are provided to ~n the A input of an OR gate 26, which in combination with a retriggerable multivibrator circuit 28 forms onë-shot monostable multivibrator 24. The inverted B pin of OR gate 26 is coupled to a +Vl source. The output of monostable multivibrator 24 is provided, in turn, to a D-type flip-flop circuit 30 which provides a timed output to the INT input pin of microcompu.er 20 for initiating an interrupt therein. Following receipt from flip-flop 30 of an interrupt signal provided to its INT input pin, microcomputer 20, which in a preferred em~odiment is an 8048 microcomp~ter with h ~ aOM and a 64 byte RAM, finishes its current operation, or task, and executes a time slot generati~g subroutine as more fully describe~ hereinafter.
Each AML puls~ pro~ided to ~ ~3tæ 2~ ~riggers multivibrator 28 for in}tiatE~ a ~legative-goîng pulse at its g output which is coupled to the C~K inp~ of D-type flip-~op circuit 30.
The RC time const~nt o the circuit coupled to multivibrator 28 is selected such that the width of this negative-going pulse is about 250 microseconds in a preferred embodiment. D-type flip-flop 3Q is triygered by the positive going edge of the Q
1~ output of multivibra~or 28. It will be recalled that an AML
pulse is produced by decoder 18 during hori~ontal line 13 o~
ea~h ~ield in r~sponse to a market code match. ~he ~S0 micro~cond duration o~ the output of mono~table multivibrator 28 is of sufficient length to insure triggering or clocking of flip-1Op 30 only 250 microseconds after this market code induced horizontal line 13 ~ML pulse so as to provide a precise timing r~ference signal at its Q output. In particular, multivibrator 28 will be triggered or retriggered by the horizontal line 13 ~ML pulse regardless of the number of AML pulses preceding it in a given field and before producing a positive-going output transition such that the ~ output of flip-flop 30 will go low at a fixed time each field, i.e., 250 microseconds after the horizontal line 13 AML pulse.
Counter 22 is a binary counter, to the C~K input of which is provided the AML pulses. Counter 22 provides binary outputs via lines ~4, 46 and 48 to the P21, P~2, and P23 input pins of microcomputer 20. Counter 22 is reset by an output provided form the P24 output pin of microcomputer 20 to the RESET
input of counter 22. It is by means of the binary output signals from counter 22 that the number of ~ML pulses received by decoder 18 is provided to microcomputer 20 for decodiny headencl commands as explai~d i~ ~he reexe~t coperld~n~ application.
The Q output ~rom flip-flop circuit ~0 is provided to the INT (Interrupt) input pin of microcomputer 20 for initiating an interrupt in the operation thereof. Following receipt from flip-flop 30 of an interrupt signal provided to its INT input pin, ~icrocomputer 20, which in a preferred embodiment of the present invention is an 8048 microcomputer with a lK ROM and a 64 byte RAM, finishes its current operation, or task, and executes a subroutine shown in simplified flow chart form in FIG. 4 and described below. Following a predetermined time interval as established by the~operating pxogram in th~
microcomp~t~r's ROM 23, microcomputer 20 provides a reset pulse rom its P24 output pin to the RESET input of counter 22 and, via inverter 32 to the CLEAR (CD ) and ~ESET tR) inputs of multivibrator 24 and D-type flip-flop 30, respecitively. The reset output from microcomputer 20 prepares counter 22 and the combination of one-shot monostable multivibrator 24 and D-type flip-flop 30 for receipt of the AML pulses from decoder 18 during thc next VBI.
~9 With microcomputer 20 interrupted 250 microseconds after the market code induced horizontal line 13 AML pulses, an internal software timer in the microcomputer 20 divides the subsequent 16.8 millisecond raster scan field into 8 equal time slots as shown in FIG. 3. Thus, each raster scan field is divided into ~ slots of appr~imately 2 milliseconds. A data packet of ~p~oximately 1400 microseconds in length may then be positioned within a respective time slot by means of a "slotted aloha" data packet transmission approach well known to those skilled in the art. The dat~ packets are positioned within a packet time interval in a respective time slot, with a guard time positioned fore and aft of the packet time interval ~o~

within each slot, The guard time insures data packet positioning exactly within a respective slot and prevents the overlapped transmission of adjacent data packets. Each data packet is thus separated ~r~ ~n adjace~t ~a~a packet by a well-defined time interval ~n~ all ~a p~c~ts ar~ synchr~niz~d with respect to a vertical rate component o~- the ~ownstream signal; in particular, the market code inauced AML pulse on horizontal line 13 of each VBI. The information provided in the individual data packets may be the result of subscriber entries, such as program requests, on a conventional subscriber input device 21 coupled to ~icrocomputer 20, or headend-initiated subscriber interrogation~ The data packets are provided from the P output pin o~ microcomputer 20 via line 50 to transmitter 16 and thence to diplex filter 14 or transmission to the cable headend 12 via cable 15. Subscriber input device 21 may also be coupled to decoder 18 and thus is shown in dotten line form as such in FIG. 1. In this case, subscriber inputs entered in input device 21 would be provided via decoder 18 to microcomputer 20 as keystroke serial data.
~ Table I shows a preferred arrangement for the transmission of upstream data packets for use in the present invention. Upstream data may be transmitted on four separate channels designa~ea T7, T~, T9 and T10. The frequency bands in which these channels are transmitted are: 5-12 MHz, 12-18 MHz, 18-24 MHz, and 24 30 MHz, respectively. However, the present invention is not limited to this upstream data packet transmission arrangement as these details are provided only for disclosing a preferred arrangement of the present ;nvention.

~æosG~6 TABLE I

7 r _ _ . _ . _.___,__ __ . _ _ . _ __ .____ . _ _ , . _ . __ _ UPSTREAM
DATA
CHANNEL T7 T~ T9 T10 S FREQUENCY- -B~N~ 5-12 MHz 12-18 MHz 18-24 MHz 24-30 MHz Referring to FIG. 4, there is shown a simplified flow chart of the progra~ executed in microcomputer 20 in synchroni~ing the data packet time ~lots with the VBI signals recelved from the cable headend 12. Microcomputer 20 initially undergoes an ~ML external interrupt upon the receipt of a Q
output ~rom D-type ~lip~1Op circult ~0. This interrupt ~ollow9 VBI line 13 by 2S0 micro5econds in a preferred embodiment~ ~he program stored in the microcomputer's ~OM 23 then reads the AML
count as provided to microcomputer 20 from counter 22 via lines 44, 46 and 48. ~ reset pulse is then provided via the P24 output pin of microcomputer 20 to the RESET input of counter 22 and the CLEAR and RESET inputs of multivibrator 24 and D-type flip-flop circuit 30, respectively. A field c~unter within ~0 microcomputer 20 is then incremented by one. A COMMAND-READY
flag is then set in microcomputer 20 for the purpose of examining the contents of a random access memory (RAM) 25 within microcomputer 20 in order to determine what action is to be taken by the subscriber's unit upon command receipt. The program then resets a SLOT-IN-FIELD counter in the form of a ~oftware timer within microcomputer 20 in order to synchronize the slots in the raster scan field with the address match signal provided by decoder 18 t~ monostable mu~tivibra~or 24. The SLOT-IN-FIELD
counter continues to count i~ 2~Q microsecond increments by means of an internal timer interrupt generated in microcomputer 20 in order to properly clock out the slots in each of the raster ~2~)~6~;

scan fields. The program then exits the interrupt routine and returns to the main program in continuin~ to exercise system control.
There has thus been shown a synchronization system S for a two-way CATV system in which upstream data packets may be inserted in time ~lots synchronized with the downstream video signal VBI~ Upstream ~ata packets are transrnitted in VBI-synchronized time slots for reducing data transmission errors and increasing data through put to the CATV headend in a multi-subscriber slotted contention system.
While particular embodiments of the present invention h~ve been shown and described, it will be obvious to those ~killed in the art that changes and modifications may be made without departing from the invention in its broader aspects.
Therefore, the aim of the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the inventin. The matter set forth in the foregoing description and accompanying drawings is offered by way of ill~stration only and not as a limitation. The actual scope 2a o the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.

Claims (16)

What Is Claimed Is:
1. A time sloted aloha two-way CATV system wherein video signals having a vertical rate signal component are transmitted downstream on a cable from a headend to a plurality of subscriber terminals and each subscriber terminal may in turn transmit upstream data packets to said headend on said cable, said system comprising:
signal detection means for detecting said vertical rate signal component and generating a timing reference signal in response thereto; and signal processing means coupled to said signal detection means and responsive to said timing signal for dividing the next succeeding raster scan field into a plurality of equal time slots in predetermined time relation to said timing signal in which said data packets may be inserted for upstream transmission.
2. A system as in claim 1 wherein said vertical rate signal is transmitted during the vertical blanking interval of said video signals.
3. A system as in claim 2 wherein said vertical rate signal is transmitted during a designated line of the vertical blanking interval of said video signals.
4. A system as in claim 1 wherein said vertical rate signal component comprises a vertical rate coded control signal for controlling subscriber terminal response to said video signals.
5. A system as in claim 1 wherein said raster scan field is divided into eight time slots of equal duration.
6. In a time slotted aloha two-way CATV system including means for transmitting program video signals over a plurality of CATV channels from a headend to a plurality of CATV subscriber terminals by means of a cable, wherein said video signals include a control code transmitted in the vertical blanking interval thereof, each subscriber terminal comprising:
decoder means coupled to said headend by means of said cable for detecting each occurrence of said control code for generating a first timing signal in timed relation thereto;
signal processing means coupled to said decoder means for dividing the next succeeding raster scan field of said video signal into a plurality of equal time slots in predetermined time relation to said first timing signal and for generating a second timing signal synchronous with said plurality of time slots; and transmitter means coupled to said headend by means of said cable and to said signal processing means and responsive to said second timing signal for selectively transmitting a data packet during a respective one of said time slots to said CATV
headend.
7. A subscriber terminal as in claim 6 wherein said decoder means includes memory means wherein is stored system address information for comparison with said control code for the generation of a match signal representing said first timing signal when said system information and said control code match.
8. A subscriber terminal as in claim 7 wherein said signal processing means includes a microcomputer responsive to said first timing signal and including an interval timer for dividing the next succeeding raster scan field into a plurality of equal time slots.
9. A subscriber terminal as in claim 8 wherein said signal processing means selectively provides a data packet to said transmitter means within a respective time slot.
10. A subscriber terminal as in claim 8 wherein each raster scan field is divided into 8 equal time slots.
11. A subscriber terminal as in claim 10 wherein each time slot is 2 milliseconds and each data packet is 1400 microseconds in length.
12. In a two-way CATV system including means for transmitting program video signals downstream over a plurality of channels downstream by means of a cable from a headend to a plurality of individually authorizable CATV subscriber terminals and wherein data may be transmitted upstream from each CATV subscriber terminal to said headend by means of said cable and wherein said video signals include a raster scan field portion and a vertical blanking interval portion having a plurality of retrace lines in which a control code is transmitted downstream to each of said subscriber terminals, each of said subscriber terminals comprising:
decoder means coupled to said headend by means of said cable, said decoder means including memory means for storing system address information, for comparing said control code with said system address information and for selectively generating a match signal when said control code and said system address information match, wherein said match signal is in timed relation with the control code in the retrace lines of said vertical blanking interval;
signal processing means coupled to said decoder means and responsive to said match signal and including interval timing means for dividing the next succeeding raster scan field into a plurality of time slots of equal duration which are synchronized with said control code and for selectively generating a data packet synchronous with a time slot; and transmitter means coupled to said headend by means of said cable and further coupled to said signal processing means and responsive thereto for transmitting said data packet to said headend within a selected one of said time slots.
13. A method for providing data upstream in a two-way CATV
system from a subscriber terminal to a headend by means of a cable connected therebetween, wherein video program signals including a vertical rate signal and a raster scan field are provided downstream from said headend to said subscriber terminal, said method comprising:
detecting said vertical rate signal;
dividing the next raster scan field into a plurality of equal time slots in timed relation to the detected vertical rate signal;
selectively generating a data packet synchronous with one of said time slots; and transmitting said data packet upstream to said headend in the next raster scan field within said one time slot.
14. A method as in claim 13 further including the steps of:
transmitting a control code downstream during said vertical blanking interval for controlling subscriber terminal response to said video program signals; and detecting said control code in providing a timing reference signal relative to said next raster scan field.
15. A method as in claim 14 further including the steps of comparing said control code with a system address code stored in each subscriber terminal and generating a timing signal when said control code and said system address code match for dividing the next raster scan field following said control code into said plurality of equal time slots.
16. A method as in claim 15 further comprising the step of transmitting said control code during a designated retrace line of said vertical blanking interval.
CA000469081A 1983-12-09 1984-11-30 Methode and system for upstream data packet time slot synchronization with downstream vbi in a two-way catv system Expired CA1209686A (en)

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US56002883A 1983-12-09 1983-12-09
US560,028 1983-12-09
US06/648,569 US4553161A (en) 1983-12-09 1984-09-06 Upstream data packet time slot synchronization with downstream VBI for two-way CATV system
US648,569 1984-09-06

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Families Citing this family (82)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4789860A (en) * 1985-03-12 1988-12-06 U.S. Philips Corp. Interface between a receiver and a sub-system
CA1317667C (en) * 1987-11-02 1993-05-11 Michel Dufresne Catv subscriber terminal transmission control
US5235619A (en) * 1990-03-20 1993-08-10 Scientific-Atlanta, Inc. Cable television radio frequency subscriber data transmission apparatus and rf return method
US4939790A (en) * 1988-03-28 1990-07-03 Zenith Electronics Corporation PLL frequency stabilization in data packet receivers
US5150247A (en) * 1989-10-30 1992-09-22 Broadband Technologies, Inc. Fiber optic telecommunication system employing continuous downlink, burst uplink transmission format with preset uplink guard band
US5255086A (en) * 1990-03-20 1993-10-19 Scientific-Atlanta, Inc. Method and apparatus for RF data transfer in a CATV system
US5142690A (en) * 1990-03-20 1992-08-25 Scientific-Atlanta, Inc. Cable television radio frequency data processor
US5093718A (en) * 1990-09-28 1992-03-03 Inteletext Systems, Inc. Interactive home information system
US5421030A (en) * 1991-09-17 1995-05-30 Com21, Inc. Communications system and method for bi-directional communications between an upstream control facility and downstream user terminals
US5497187A (en) * 1991-11-29 1996-03-05 Scientific-Atlanta, Inc. In-band/out-of-band data transmission method and apparatus for a television system
US5534912A (en) * 1994-04-26 1996-07-09 Bell Atlantic Network Services, Inc. Extended range video on demand distribution system
JPH0818659A (en) * 1994-06-28 1996-01-19 Kokusai Denshin Denwa Co Ltd <Kdd> Communication system using bi-directional tree network
US5570347A (en) * 1994-11-14 1996-10-29 Zenith Electronics Corporation Upstream data transmission system with downloadable transmission parameters
US5546119A (en) * 1994-11-14 1996-08-13 Bestler; Caitlin B. Transmission modulator for cable television upstream data transmission
US5535206A (en) * 1994-11-14 1996-07-09 Zenith Electronics Corporation Upstream data transmission system for cable television
US5881362A (en) 1994-11-30 1999-03-09 General Instrument Corporation Of Delaware Method of ingress noise reduction in calbe return paths
US5515014A (en) * 1994-11-30 1996-05-07 At&T Corp. Interface between SAW filter and Gilbert cell mixer
JPH08336127A (en) * 1995-06-06 1996-12-17 Fujitsu Ltd Video-on-demand system
US6356555B1 (en) 1995-08-25 2002-03-12 Terayon Communications Systems, Inc. Apparatus and method for digital data transmission using orthogonal codes
US5805583A (en) * 1995-08-25 1998-09-08 Terayon Communication Systems Process for communicating multiple channels of digital data in distributed systems using synchronous code division multiple access
US5793759A (en) * 1995-08-25 1998-08-11 Terayon Corporation Apparatus and method for digital data transmission over video cable using orthogonal cyclic codes
US5745837A (en) * 1995-08-25 1998-04-28 Terayon Corporation Apparatus and method for digital data transmission over a CATV system using an ATM transport protocol and SCDMA
US6665308B1 (en) 1995-08-25 2003-12-16 Terayon Communication Systems, Inc. Apparatus and method for equalization in distributed digital data transmission systems
US5768269A (en) * 1995-08-25 1998-06-16 Terayon Corporation Apparatus and method for establishing frame synchronization in distributed digital data communication systems
US6307868B1 (en) 1995-08-25 2001-10-23 Terayon Communication Systems, Inc. Apparatus and method for SCDMA digital data transmission using orthogonal codes and a head end modem with no tracking loops
US5991308A (en) * 1995-08-25 1999-11-23 Terayon Communication Systems, Inc. Lower overhead method for data transmission using ATM and SCDMA over hybrid fiber coax cable plant
US5787483A (en) * 1995-09-22 1998-07-28 Hewlett-Packard Company High-speed data communications modem
US5784597A (en) * 1995-09-22 1998-07-21 Hewlett-Packard Company Communications network system including acknowledgement indicating successful receipt of request for reserved communication slots and start time for said reserved communication slots
US5790806A (en) * 1996-04-03 1998-08-04 Scientific-Atlanta, Inc. Cable data network architecture
US5818840A (en) * 1995-12-14 1998-10-06 Time Warner Entertainment Co. L.P. Asymmetric ATM switch
US6340987B1 (en) 1995-12-14 2002-01-22 Time Warner Entertainment Company L.P. Method and apparatus for masking latency in an interactive television network
US5995134A (en) * 1995-12-14 1999-11-30 Time Warner Cable Method and apparatus for enticing a passive television viewer by automatically playing promotional presentations of selectable options in response to the viewer's inactivity
US5805154A (en) * 1995-12-14 1998-09-08 Time Warner Entertainment Co. L.P. Integrated broadcast application with broadcast portion having option display for access to on demand portion
US5774458A (en) * 1995-12-14 1998-06-30 Time Warner Cable Multiplex amplifiers for two-way communications in a full-service network
US5822530A (en) * 1995-12-14 1998-10-13 Time Warner Entertainment Co. L.P. Method and apparatus for processing requests for video on demand versions of interactive applications
US5802448A (en) * 1995-12-14 1998-09-01 Time Warner Entertainment Co., L.P. Method and apparatus for processing requests for interactive applications based on system resources
US5771435A (en) * 1995-12-14 1998-06-23 Time Warner Entertainment Co. L.P. Method and apparatus for processing requests for video presentations of interactive applications in which VOD functionality is provided during NVOD presentations
US5671217A (en) * 1995-12-14 1997-09-23 Time Warner Entertainment Co. L.P. Scalable communications network employing shared logical nodes
US6044396A (en) * 1995-12-14 2000-03-28 Time Warner Cable, A Division Of Time Warner Entertainment Company, L.P. Method and apparatus for utilizing the available bit rate in a constrained variable bit rate channel
US5822676A (en) * 1995-12-14 1998-10-13 Time Warner Entertainment Co. L.P. Digital serialization of program events
US5819036A (en) * 1995-12-14 1998-10-06 Time Warner Cable Method for message addressing in a full service network
US5797010A (en) * 1995-12-22 1998-08-18 Time Warner Cable Multiple run-time execution environment support in a set-top processor
US6058430A (en) * 1996-04-19 2000-05-02 Kaplan; Kenneth B. Vertical blanking interval encoding of internet addresses for integrated television/internet devices
KR100483370B1 (en) 1996-09-17 2005-04-15 세드나 페이턴트 서비시즈, 엘엘씨 Set top terminal for an interactive information distribution system
US5870472A (en) * 1996-11-12 1999-02-09 General Instrument Corporation Dynamic relocation of the service data channel
US6078593A (en) 1997-02-04 2000-06-20 Next Level Communications Method and apparatus for reliable operation of universal voice grade cards
WO1998040863A1 (en) 1997-03-14 1998-09-17 Tv Interactive Data Corporation A method of detachably attaching an insert to a remote control base and the resulting remote control
US6049539A (en) * 1997-09-15 2000-04-11 Worldgate Communications, Inc. Access system and method for providing interactive access to an information source through a networked distribution system
JP2001526506A (en) * 1997-12-09 2001-12-18 アイシーティーブイ・インク Virtual LAN printing on interactive cable television system
US6260193B1 (en) 1998-02-09 2001-07-10 General Instrument Corporation Synchronization of decoders in a bi-directional CATV network
US6535480B1 (en) 1998-11-20 2003-03-18 At&T Corp. System and method to provide survivability for broadcast video and interactive IP-based services on cable access networks
EP1172003A1 (en) * 1999-04-14 2002-01-16 General Instrument Corporation Synchronization of decoders in a bi-directional catv network
IL131192A (en) 1999-08-01 2009-08-03 Xtend Networks Ltd Television multiplexing and transmission system
US6526070B1 (en) * 1999-10-09 2003-02-25 Conexant Systems, Inc. Method and apparatus for upstream burst transmissions synchronization in cable modems
US7568207B1 (en) * 2000-06-23 2009-07-28 Braun Warren L Cable drop monitor with upstream signalling
US7616890B2 (en) * 2000-10-16 2009-11-10 Xtend Networks Ltd. System, device and method of expanding the operational bandwidth of a communication infrastructure
US20050283816A1 (en) * 2004-06-16 2005-12-22 Xtend Networks, Ltd. Wideband node in a cable TV network
US20020174435A1 (en) * 2001-02-27 2002-11-21 Hillel Weinstein System, apparatus and method for expanding the operational bandwidth of a communication system
US20080040764A1 (en) * 2001-07-20 2008-02-14 Hillel Weinstein System, apparatus and method for expanding the operational bandwidth of a communication system
US7206321B1 (en) * 2001-09-27 2007-04-17 Conexant Systems, Inc. Method and apparatus for flexibly filtering scheduling messages in a communication system
US20050041679A1 (en) * 2001-10-10 2005-02-24 Hillel Weinstein Method and system for a true-video-on-demand service in a catv network
WO2003047251A1 (en) * 2001-11-26 2003-06-05 Xtend Networks Ltd. System and method for spectral node splitting in a hybrid fiber optic-coaxial cable network
US20070063790A1 (en) * 2005-05-19 2007-03-22 Yeshayahu Strull Wideband CATV signal splitter device
WO2003094347A1 (en) * 2002-05-02 2003-11-13 Xtend Networks Ltd. A wideband catv signal splitter device
FR2844600A1 (en) * 2002-09-13 2004-03-19 Thomson Licensing Sa Second subscription domestic e.g. television, apparatus checking relative position domestic network method having alternating electrical periods measured first/second apparatus and offset comparison verified/not verified
US7668099B2 (en) * 2003-06-13 2010-02-23 Apple Inc. Synthesis of vertical blanking signal
IL157285A0 (en) * 2003-08-06 2004-02-19 Xtend Networks Ltd A wideband catv tap device
US20050216947A1 (en) * 2004-03-29 2005-09-29 Corbin Scott A Upstream data bypass device for a video system
US8074248B2 (en) 2005-07-26 2011-12-06 Activevideo Networks, Inc. System and method for providing video content associated with a source image to a television in a communication network
KR100842248B1 (en) * 2006-03-21 2008-06-30 한국전자통신연구원 Optical Communication System and method using Manchester Encoded Signal Re-modulation
US9826197B2 (en) 2007-01-12 2017-11-21 Activevideo Networks, Inc. Providing television broadcasts over a managed network and interactive content over an unmanaged network to a client device
EP2106665B1 (en) 2007-01-12 2015-08-05 ActiveVideo Networks, Inc. Interactive encoded content system including object models for viewing on a remote device
US9021541B2 (en) 2010-10-14 2015-04-28 Activevideo Networks, Inc. Streaming digital video between video devices using a cable television system
WO2012138660A2 (en) 2011-04-07 2012-10-11 Activevideo Networks, Inc. Reduction of latency in video distribution networks using adaptive bit rates
EP2815582B1 (en) 2012-01-09 2019-09-04 ActiveVideo Networks, Inc. Rendering of an interactive lean-backward user interface on a television
US9800945B2 (en) 2012-04-03 2017-10-24 Activevideo Networks, Inc. Class-based intelligent multiplexing over unmanaged networks
US9123084B2 (en) 2012-04-12 2015-09-01 Activevideo Networks, Inc. Graphical application integration with MPEG objects
WO2014145921A1 (en) 2013-03-15 2014-09-18 Activevideo Networks, Inc. A multiple-mode system and method for providing user selectable video content
US9294785B2 (en) 2013-06-06 2016-03-22 Activevideo Networks, Inc. System and method for exploiting scene graph information in construction of an encoded video sequence
US9219922B2 (en) 2013-06-06 2015-12-22 Activevideo Networks, Inc. System and method for exploiting scene graph information in construction of an encoded video sequence
EP3005712A1 (en) 2013-06-06 2016-04-13 ActiveVideo Networks, Inc. Overlay rendering of user interface onto source video
US9788029B2 (en) 2014-04-25 2017-10-10 Activevideo Networks, Inc. Intelligent multiplexing using class-based, multi-dimensioned decision logic for managed networks

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1369463A (en) * 1971-11-23 1974-10-09 Process Peripherals Ltd Communications systems
US3769579A (en) * 1972-03-31 1973-10-30 Oak Electro Netics Corp Cable television monitoring system
US3882392A (en) * 1973-01-29 1975-05-06 Oak Industries Inc Hotel-motel pay TV system
US3997718A (en) * 1973-02-01 1976-12-14 The Magnavox Company Premium interactive communication system
US3919462A (en) * 1973-08-15 1975-11-11 System Dev Corp Method and apparatus for scrambling and unscrambling communication signals
US4019201A (en) * 1973-08-15 1977-04-19 System Development Corporation Method and apparatus for scrambling and unscrambling communication signals
US4250524A (en) * 1979-02-22 1981-02-10 Clarion Co., Ltd. Validation apparatus in a pay television system
NL189062C (en) * 1980-02-15 1992-12-16 Philips Nv METHOD AND SYSTEM FOR TRANSFER OF DATA PACKAGES.
CA1158738A (en) * 1980-04-30 1983-12-13 Manitoba Telephone System (The) Video and data distribution module with subscriber terminal
NL8005458A (en) * 1980-10-02 1982-05-03 Philips Nv COMMUNICATION SYSTEM AND STATION SUITABLE FOR THIS.
JPS5819087A (en) * 1981-07-24 1983-02-03 Pioneer Electronic Corp Data in catv system

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