Undesirable energy suppression system in the return path of a bidirectional cable network having dynamically allocated time slots

• US 5,815,794 A
• Filed: 09/01/1995
• Issued: 09/29/1998
• Est. Priority Date: 09/01/1995
• Status: Expired due to Fees

• Current Assignee: Cable Television Laboratories Incorporated
• Original Assignee: Cable Television Laboratories Incorporated
• Inventors: Williams, Thomas H.
• Primary Examiner(s): Grant, Christopher C.
• Application Number:
  US08/522,630
• Time in Patent Office: 1,124 Days
• Field of Search: 348/12, 348/13, 348/6, 348/7, 348/8, 348/9, 348/10, 348/11, 348/14, 348/15, 348/16, 348/17, 348/18, 455/5.1, 455/6.1, 455/6.2, 455/6.3, 455/4.2
• US Class Current: 725/125
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/44 Star or tree networks
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A bidirectional cable network having a signal distribution system that prevents undesirable energy in the bidirectional cable network'"'"'s return path from adversely effecting the entire network. The signal distribution system a first signal transmitted in a forward path direction over the bidirectional communication path from a headend to a plurality of remote points. Signals transmitted in a return path direction are time division multiplexed on a series of cyclically reoccurring time slots where at least one of the cyclically reoccurring time slots is assigned to each of the plurality of remote points. At least one primary return gate is effective during each occurrence of the cyclically reoccurring time slots for isolating all of the plurality of remote points from accessing the network to transmit a signal in second direction except for the one of the plurality of remote points which is assigned the cyclically reoccurring time slot that is presently providing a path to transmit in the second direction from the remote point to the headend. In one embodiment each return gate services a plurality of remote points within the return gate'"'"'s distribution branch. In a second embodiment each remote point has a dedicated return gate.

Claims

1. A bidirectional cable network system for enabling bidirectional signal exchanges in a network having a bidirectional communication path between a headend signal source and a plurality of remote points, said system comprising:

first means for enabling said plurality of remote points to receive a first signal transmitted in a first direction over said bidirectional communication path from said headend to said plurality of remote points;

means for defining a series of cyclically reoccurring time slots for use on said bidirectional communication path between said headend and said plurality of remote points;

at least one return gate located in a second direction of said bidirectional communication path to connect and disconnect said second direction of said bidirectional communication path in concert with any one of said series of cyclically reoccurring time slots on behalf of any of said plurality of remote points that are downstream from said at least one return gate;

means for requesting an assignment of at least one of said series of cyclically reoccurring time slots at will by any of said plurality of remote points;

means for dynamically assigning at least one of said series of cyclically reoccurring time slots in real time to said requesting one of said plurality of remote points;

second means for enabling said requesting one of said plurality of remote points to transmit in said second direction to said headend during an occurrence of each of said at least one of said series of cyclically reoccurring time slots to which said requesting one of said plurality of remote points is assigned; and

means for engaging each of said at least one return gate independent of said headend to disconnect said second direction of said bidirectional communication path by way of each of said at least one return gate at all times except to connect said second direction of said bidirectional communication path by each of said at least one return gate that is in an upstream path from said requesting one of said plurality of remote points during an occurrence of each of said series of cyclically reoccurring time slots to which said requesting one of said plurality of remote points is assigned.

2. A signal distribution system according to claim 1 including:

third means for enabling said plurality of remote points and said at least one return gate to concurrently and continuously receive said first signal transmitted in said first direction.

3. A signal distribution system according to claim 1 wherein said means for defining said series of cyclically reoccurring time slots includes:

means for defining a series of frames comprising;

at least one polling frame containing a plurality of polling time slots individually corresponding to each of said plurality of remote points for transmitting a service initiation request from said plurality of remote points to said headend and for transmitting a service termination signal from said headend to any one of said plurality of remote points;

a plurality of data frames each containing a plurality of data time slots for transmitting said return signal in said second direction from any one of said plurality of remote points to said headend; and

means for defining a guard interval between each of said plurality of polling time slots and said plurality of data time slots.

4. A signal distribution system according to claim 3 wherein said means for defining said series of cyclically reoccurring time slots includes:

at least one network monitoring frame containing a plurality of path monitoring time slots individually corresponding to each of said plurality of remote points for monitoring each of said plurality of remote points for undesirable energy on said bidirectional communication path.

5. A signal distribution system according to claim 3 wherein said at least one polling frame includes:

said service initiation request accompanied with data for said service initiation request embedded therein.

6. A signal distribution system according to claim 1 wherein said means for assigning includes:

means for assigning said series of cyclically reoccurring time slots in real time where time slot assignment data is extracted from said first signal being transmitted in said first direction.

7. A signal distribution system according to claim 1 wherein said means for engaging includes:

at least one primary return gate with no other return gate between itself and at least one of said plurality of remote points on a distribution branch of said bidirectional communication path and at least one secondary return gate in series with said primary return gate between said primary return gate and said headend; and

means for synchronizing said at least one primary return gate and said at least one secondary return gate with said headend and each of said plurality of remote points based on said first signal transmitted in said first direction as a timing reference.

8. A signal distribution system according to claim 7 wherein:

an individual one of said at least one primary return gate serves at least two of said plurality of remote points on said distribution branch.

9. A signal distribution system according to claim 7 wherein said at lest one primary return gate includes:

only one of said at least one primary return gate being dedicated to a corresponding one of said plurality of remote points on said distribution branch.

10. A signal distribution system according to claim 1 including:

means for disconnecting an individual one of said plurality of remote points from said first direction of said bidirectional communication path; and

means for reconnecting said individual one of said plurality of remote points to said first direction of said bidirectional communication path.

11. A signal distribution system according to claim 1 further including:

means for testing isolation of said return gate on said second direction of said bidirectional communication path.

12. A method for use in a bidirectional cable network system for enabling bidirectional signal exchanges in a network having a bidirectional communication path between a headend signal source and a plurality of remote points, said method comprising the steps of:

first step of enabling said plurality of remote points to receive a first signal transmitted in a first direction over said bidirectional communication path from said headend to said plurality of remote points;

defining a series of cyclically reoccurring time slots for use on said bidirectional communication path between said headend and said plurality of remote points;

locating at least one return gate located in a second direction of said communication path to connect and disconnect said second direction of said bidirectional communication path in concert with any one of said series of cyclically reoccurring time slots on behalf of any of said plurality of remote points that are downstream from said at least one return gate;

requesting an assignment of at least one of said series of cyclically reoccurring time slots at will by any of said plurality of remote points;

dynamically assigning at least one of said series of cyclically reoccurring time slots in real time to said requesting one of said plurality of remote points;

second step of enabling said requesting one of said plurality of remote points to transmit in said second direction to said headend during an occurrence of each of said at least one of said series of cyclically reoccurring time slots to which said requesting one of said plurality of remote points is assigned; and

engaging each of said at least one return gate independent of said headend to disconnect said second direction of said bidirectional communication path by way of each of said at least one return gate at all times except to connect said second direction of said bidirectional communication path by each of said at least one return gate that is in an upstream path from said requesting one of said plurality of remote points during an occurrence of each of said series of cyclically reoccurring time slots to which said requesting one of said plurality of remote points is assigned.

13. A method according to claim 12 including:

third step of enabling said plurality of remote points and said at least one return gate to concurrently and continuously receive said first signal transmitted in said first direction.

14. A method according to claim 12 wherein said step of defining said series of cyclically reoccurring time slots includes:

defining a series of frames comprising;

at least one polling frame containing a plurality of polling time slots individually corresponding to each of said plurality of remote points for transmitting a service initiation request from said plurality of remote points to said headend and for transmitting a service termination signal from said headend to any one of said plurality of remote points;

a plurality of data frames each containing a plurality of data time slots for transmitting said return signal in said second direction from any one of said plurality of remote points to said headend; and

defining a guard interval between each of said plurality of polling time slots and said plurality of data time slots.

15. A method according to claim 14 wherein said step of defining said series of cyclically reoccurring time slots includes:

at least one network monitoring frame containing a plurality of path monitoring time slots individually corresponding to each of said plurality of remote points for monitoring each of said plurality of remote points for undesirable energy on said bidirectional communication path.

16. A method according to claim 14 wherein said at least one polling frame includes:

said service initiation request accompanied with data for said service initiation request embedded therein.

17. A method according to claim 12 wherein said step of assigning includes:

assigning said series of cyclically reoccurring time slots in real time wherein time slot assignment data is extracted from said first signal being transmitted in said first direction.

18. A method according to claim 12 wherein said step of engaging includes:

operating at least one primary return gate with no other return gate between itself and at least one of said plurality of remote points on a distribution branch of said bidirectional communication path and at least one secondary return gate in series with said primary return gate between said primary return gate and said headend; and

synchronizing said at least one primary return gate and said at least one secondary return gate with said headend and each of said plurality of remote points based on said first signal being transmitted in said first direction as a timing reference.

19. A method according to claim 18 wherein said step of operating said at least one primary return gate includes:

serving a plurality of said plurality of remote points with an individual one of said at least one primary return gate on said distribution branch.

20. A method according to claim 18 wherein said step of operating said at least one primary return gate includes:

serving each one of said plurality of remote points with a corresponding dedicated one of said at least one primary return gate on said distribution branch.

21. A method according to claim 12 including:

disconnecting an individual one of said plurality of remote points from said first direction of said bidirectional communication path; and

reconnecting said individual one of said plurality of remote points to said first direction of said bidirectional communication path.

22. A method according to claim 12 further including:

testing isolation of said return gate on said second direction of said bidirectional communication path.

23. A system to protect a bidirectional cable network from having undesirable energy uncontrollably propagate along a return path between a plurality of remote points and a headend in said bidirectional cable network, said bidirectional cable network having a bidirectional communication path and tree type trunk and branch configuration, said system comprising:

means for defining a series of cyclically reoccurring time slots for use on said bidirectional communication path between said headend and said plurality of remote points;

means for requesting an assignment of at least one of said series of cyclically reoccurring time slots at will by any of said plurality of remote points;

means for dynamically assigning at least one of said series of cyclically reoccurring time slots in real time to said requesting one of said plurality of remote points;

a plurality of intelligent return gates to connect and disconnect said return path of said plurality of remote points on a distribution branch of said bidirectional cable network in concert with dynamically assigned ones of said series of cyclically reoccurring time slot; and

means for disconnecting said return path independent of any time slot assignments by way of any one of said plurality of return gates of said distribution branch to isolate a specific downstream section of said distribution branch and specific downstream ones of said plurality of remote points from access to a clean part of said bidirectional cable network.

24. A system according to claim 23 wherein at least one of said plurality of return gates serves at least two of said plurality of remote points on said distribution branch of said bidirectional communication path.

25. A system according to claim 23 wherein each one of said plurality of remote points has a primary return gate dedicated thereto.