Synchronization of decoders in a bi-directional CATV network

• US 6,260,193 B1
• Filed: 02/09/1998
• Issued: 07/10/2001
• Est. Priority Date: 02/09/1998
• Status: Expired due to Term

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Chodelka, David E., Reichgott, Sam, Schell, Charles E. III, Chang, Kevin T.
• Primary Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US09/021,006
• Time in Patent Office: 1,247 Days
• Field of Search: H04/N.716, H04/N.7173, 725/121, 725/116, 725/117, 725/114, 725/122, 725/123, 348/500, 348/510, 348/512, 348/513, 348/518, 348/478, 348/479, 348/461, 348/460, 348/464, 348/465, 348/467
• US Class Current: 725/121
• CPC Class Codes: H04N 21/2221 being a cable television head-end CATV in broadcast systems H04H20/78
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/4384 involving operations to reduce the access time, e.g. fast-tuning for reducing channel switching latency
• CPC Class Codes: H04N 21/44209 Monitoring of downstream path of the transmission network originating from a server, e.g. bandwidth variations of a wireless network arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6581 Reference data, e.g. a movie identifier for ordering a movie or a product identifier in a home shopping application
• CPC Class Codes: H04N 7/084 with signal insertion during the horizontal blanking interval only
• CPC Class Codes: H04N 7/088 the inserted signal being digital
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A system for synchronizing one or more decoders with a network sync signal at a headend of a television communication network. The system allows decoders to transmit upstream messages synchronously in time slots which are defined according to the network sync signal, thereby improving system throughput. Identifying data is provided in a blanking interval (VBI or HBI) of one or more television signals to designate a horizontal scan line of the respective television signal which follows a reference point in the network sync signal by a predetermined delay. At each decoder, the identifying data is recovered, and the onset of the designated scan line can be used to signal the start of a transmission for the decoder. Preferably, the identifying data is provided in each television signal so the user is not forced to tune to a particular television channel to transmit a message. Various channel access protocols may be used, such as a session oriented protocol, or a synchronized ALOHA protocol.

Claims

1. A method for synchronizing a decoder in a communication network to allow upstream transmission of a message from said decoder to a headend of said communication network in a time slot, wherein said decoder is adapted to receive a television signal via said communication network, comprising the steps of:

providing a network sync signal having a network sync reference point at said headend;

providing a delay value at said headend such that a start time of said time slot follows said network sync reference point by said delay value;

determining a first horizontal scan line of said television signal at said headend that corresponds to said network sync reference point;

using said delay value and said first horizontal scan line to determine a particular horizontal scan line of said television signal at said headend that corresponds to said start time;

encoding identifying data which identifies said particular horizontal scan line; and

inserting said identifying data into a blanking interval of said television signal.

2. The method of claim 1, comprising the further step of:

inserting said identifying data into a blanking interval of said television signal which is between said first horizontal scan line and said particular horizontal scan line.

3. The method of claim 1, wherein:

said blanking interval of said television signal is one of a vertical blanking interval and a horizontal blanking interval.

4. The method of claim 1, comprising the further steps of:

transmitting said television signal to said decoder via said communication network;

recovering said television signal from said communication network at said decoder;

extracting said identifying data of said recovered television signal; and

providing a start signal using said extracted identifying data to indicate said start time for said decoder to start transmitting said message upstream to said headend in said time slot.

5. The method of claim 4, comprising the further steps of:

monitoring horizontal scan lines of said television signal; and

providing said start signal when said particular horizontal scan line of said television signal is detected.

6. The method of claim 4, wherein:

said recovering of said television signal at said decoder is responsive to a user command to view said television signal.

7. The method of claim 1, wherein said method is adapted for use in synchronizing a plurality of decoders of said communication network with said network sync signal to allow upstream transmission of a message from each of said decoders to said headend in respective time slots, wherein each of said decoders is adapted to receive a plurality of asynchronous television signals via said communication network, comprising the further steps of:

determining a respective first horizontal scan line of each of said television signals at said headend that corresponds to a respective reference point of said network sync signal;

using said delay value and said respective first horizontal scan lines to determine respective particular horizontal scan lines of said television signals at said headend that corresponds to respective start times of said respective time slots;

encoding identifying data which identifies said particular horizontal scan lines; and

inserting said identifying data into respective blanking intervals of said television signals.

8. The method of claim 7, comprising the further steps of:

transmitting said television signals to said decoders via said communication network;

recovering said television signals from said communication network at said decoders;

wherein at least two of said decoders recover different ones of said television signals;

extracting said respective identifying data of said respective recovered television signals; and

for each of said decoders, providing a start signal using said extracted identifying data to indicate a start time to start transmitting said respective message upstream to said headend in the respective time slot.

9. The method of claim 1, wherein:

said delay value is greater than a field or frame period of said television signal when said blanking interval of said television signal is a vertical blanking interval.

10. An apparatus for synchronizing a decoder in a communication network to allow upstream transmission of a message from said decoder to a headend of said communication network in a time slot, wherein said decoder is adapted to receive a television signal via said communication network, comprising:

means for providing a network sync signal having a network sync reference point at said headend;

means for providing a delay value at said headend such that a start time of said time slot follows said network sync reference point by said delay value;

a line counter for determining a first horizontal scan line of said television signal at said headend that corresponds to said network sync reference point;

a delay calculator for using said delay value and said first horizontal scan line to determine a particular horizontal scan line of said television signal at said headend that corresponds to said start time;

an encoder for encoding identifying data which identifies said particular horizontal scan line; and

means for inserting said identifying data into a blanking interval of said television signal.

11. The apparatus of claim 10, wherein:

said means for inserting inserts said identifying data into a blanking interval of said television signal which is between said first horizontal scan line and said particular horizontal scan line.

12. The apparatus of claim 10, wherein:

said blanking interval of said television signal is one of a vertical blanking interval and a horizontal blanking interval.

13. The apparatus of claim 10, further comprising:

a transmitter for transmitting said television signal to said decoder via said communication network;

means associated with said decoder for recovering said television signal from said communication network at said decoder;

means associated with said decoder for extracting said identifying data of said recovered television signal; and

means associated with said decoder for providing a start signal using said extracted identifying data to indicate said start time for said decoder to start transmitting said message upstream to said headend in said time slot.

14. The apparatus of claim 13, further comprising:

a line counter associated with said decoder for monitoring horizontal scan lines of said television signal;

wherein;

said means associated with said decoder for providing said start signal provides said start signal when said particular horizontal scan line of said television signal is detected.

15. The apparatus of claim 13, wherein:

said recovering of said television signal at said decoder is responsive to a user command to view said television signal.

16. The apparatus of claim 10, wherein:

said apparatus is adapted for use in synchronizing a plurality of decoders of said communication network with said network sync signal to allow upstream transmission of a message from each of said decoders to said headend in respective time slots;

each of said decoders is adapted to receive a plurality of asynchronous television signals via said communication network;

said line counter at said headend determines a respective first horizontal scan line of each of said television signals at said headend that corresponds to a respective reference point of said network sync signal;

delay calculation means are provided for using said delay value and said respective first horizontal scan lines to determine respective particular horizontal scan lines of said television signals at said headend that correspond to respective start times of said respective time slots;

said encoder encodes identifying data which identifies said particular horizontal scan lines; and

said means for inserting inserts said identifying data into respective blanking intervals of said television signals.

17. The apparatus of claim 16, wherein said transmitter transmits said television signals to said decoders via said communication network, and each of said decoders further comprises:

means for recovering said television signals from said communication network;

wherein at least two of said decoders recover different ones of said television signals;

means for extracting said respective identifying data of said respective recovered television signals; and

means for providing a start signal using said extracted identifying data to indicate a start time to start transmitting said respective message upstream to said headend in the respective time slot.

18. The apparatus of claim 10, wherein:

said delay value is greater than a field or frame period of said television signal when said blanking interval of said television signal is a vertical blanking interval.

19. A method for synchronizing a decoder in a communication network with a network sync signal at a headend of said network to allow upstream transmission of a message from said decoder to said headend in a time slot, comprising the steps of:

recovering a television signal from said communication network;

said television signal comprising identifying data in a blanking interval which identifies a particular horizontal scan line of said television signal which corresponds to a start time of said time slot;

extracting said identifying data of said recovered television signal; and

providing a start signal using said extracted identifying data to indicate said start time for said decoder to start transmitting said message upstream to said headend.

20. The method of claim 19, wherein:

said start time follows a network sync reference point of said network sync signal by a delay value.

21. The method of claim 19, wherein:

said blanking interval of said television signal is one of a vertical blanking interval and a horizontal blanking interval.

22. The method of claim 19, comprising the further steps of:

monitoring horizontal scan lines of said television signal; and

providing said start signal when said particular horizontal scan line of said television signal is detected.

23. The method of claim 19, wherein:

said recovering of said television signal is responsive to a user command to view said television signal.

24. The method of claim 19, wherein:

said recovered television signal is recovered from among a plurality of available asynchronous television signals which are transmitted to said decoder via said communication network; and

each of said plurality of available television signals comprises identifying data in a blanking interval thereof which identifies a particular horizontal scan line thereof which corresponds to said start time of said time slot.

25. The method of claim 20, wherein:

said delay value is greater than a field or frame period of said television signal when said blanking interval of said television signal is a vertical blanking interval.

26. A decoder which is adapted to be synchronized with a network sync signal at a headend of a communication network to allow upstream transmission of a message from said decoder to said headend in a time slot, comprising:

means for recovering a television signal from said communication network;

said television signal comprising identifying data in a blanking interval which identifies a particular horizontal scan line of said television signal which corresponds to a start time of said time slot;

means for extracting said identifying data of said recovered television signal; and

means for providing a start signal using said extracted identifying data to indicate said start time for said decoder to start transmitting said message upstream to said headend.

27. The decoder of claim 26, wherein:

said start time follows a network sync reference point of said network sync signal by a delay value.

28. The decoder of claim 26, wherein:

said blanking interval of said television signal is one of a vertical blanking interval and a horizontal blanking interval.

29. The decoder of claim 26, further comprising:

means for monitoring horizontal scan lines of said television signal;

wherein;

said providing means provides said start signal when said particular horizontal scan line of said television signal is detected.

30. The decoder of claim 26, wherein:

said recovering of said television signal is responsive to a user command to view said television signal.

31. The decoder of claim 26, wherein:

said recovered television signal is recovered from among a plurality of available asynchronous television signals which are transmitted to said decoder via said communication network; and

each of said plurality of available television signals comprising identifying data in a blanking interval thereof which identifies a particular horizontal scan line thereof which corresponds to said start time of said time slot.

32. The decoder of claim 27, wherein:

said delay value is greater than a field or frame period of said television signal when said blanking interval of said television signal is a vertical blanking interval.