Methods and apparatus for efficient IP multicasting in a content-based network

• US 20070153820A1
• Filed: 01/03/2006
• Published: 07/05/2007
• Est. Priority Date: 01/03/2006
• Status: Active Grant

• Current Assignee: Time Warner Cable Enterprises LLC (Charter Communications Incorporated)
• Original Assignee: Time Warner Cable Inc. (Charter Communications Incorporated)
• Inventors: Gould, Kenneth
• Granted Patent: US 7,693,171 B2
• Time in Patent Office: Days
• US Class Current: 370/432
• CPC Class Codes: H04J 3/245 in which the allocation protocols between more than two stations share the same transmission medium stations for satellite systems H04B7/185
• CPC Class Codes: H04L 12/1859 adapted to provide push services, e.g. data channels
• CPC Class Codes: H04L 12/1881 with schedule organisation, e.g. priority, sequence management
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 65/611 for multicast or broadcast systems for broadcast or conference H04L12/18; arrangements for broadcast or distribution combined with broadcast H04H20/00; arrangements for broadcast applications with a direct linkage to broadcast information or to broadcast space-time H04H60/00; selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS], H04W4/06

Abstract

Methods and apparatus for assigning physical channels in a content-based network. In an exemplary embodiment, the network comprises a cable television network having a plurality of cable modems, and the physical channels are assigned to the cable modems based at least in part on any multicast transmissions that may exist on the system. When two cable modems are receiving the same multicast transmission, the invention causes tuning of one or more of the cable modems to the same physical channel in order to limit the total number multicast transmissions on the network. Multicast transmissions typically comprise video or audio information, but other types of information may also be multicast according to the invention. In another embodiment, a multicast transmission list (containing a list of multicast transmissions and the corresponding physical channels) is sent to the set of cable modems. This list is used by the modems (or associated CPE) to manage channel allocation and tuning.

Claims

1. In a broadcast-switched architecture (BSA) cable network having at least one cable modem termination system (CMTS) and a plurality of cable modems in signal communication therewith, a method of providing a plurality of content channels to network subscribers via respective ones of said modems, the method comprising:

transmitting first packetized content over a first channel to at least a first of said modems;

transmitting second packetized content over a second channel to at least a second of said modems; and

selectively switching said second modem to said first channel so that said first and second modems receive said first and second packetized content in a substantially multicast fashion;

from the same physical channel

wherein said first and second channels comprise a portion of the plurality of content channels, at least a portion of said plurality of channels being switched for delivery to CPE located proximate to respective ones of said plurality of cable modems.

2. The method of claim 1, wherein said act of selectively switching further comprises selectively switching transmitting of third content to said first channel substantially contemporaneous with said act of switching said second modem, said third content being uniquely addressed to said second modem.

3. The method of claim 1, further comprising selectively switching at least one of said plurality of channels on or off based on the existence of one or more requests for delivery of the content carried by said at least one channel.

4. The method of claim 3, wherein said selective switching of said at least one channel on or off is conducted by the same entity that controls said selective switching of said second modem.

31. The method as set forth in claim 3C, wherein said physical channel associated with said first multicast transmission is also used by at least another one of said modems to receive said first multicast transmission.

5. A system for performing multicasting over a cable network, comprising:

a plurality of cable modems;

a cable modem termination system in data communication with said plurality of cable modems; and

a controller adapted to track the state of multicast transmissions to said plurality of cable modems, detect that a cable modem assigned to a first physical channel selects a combination of multicast transmissions available on a second physical channel, and cause said cable modem to switch from a first channel to said second channel.

6. The system as set forth in claim 5, wherein said first physical channel comprises one of a 6 MHz or 8 MHz radio frequency channel.

7. The system set forth in claim 5, wherein said cable modems are in signal communication with said cable modem termination system via at least a coaxial cable.

8. The system set forth in claim 5, wherein said controller is in data or signal communication with to said cable modem termination system.

9. The system set forth in claim 5, wherein said controller comprises software instructions running on a microprocessor.

10. The system set forth in claim 5, wherein said network comprises a broadcast switched architecture (BSA) network, and said multicast transmissions are delivered in tandem to subscribers along with one or more switched broadcast channels.

11. In a cable television network that comprises a plurality of cable modems, a modem termination system and a plurality of physical channels allowing communication between said plurality of cable modems and said cable modem termination system, a method of operating comprising:

monitoring a first cable modem receiving a first multicast transmission on a first physical channel;

detecting a second cable modem assigned to a second physical channel receiving said first multicast transmission; and

causing said second cable modem to switch to said first physical channel.

12. The method of claim 11, further comprising causing said cable modem termination system to transmit multicast packets to said second cable modem using said first physical channel.

13. The method of claim 11, wherein said first physical channel and said second physical channel comprise frequency divided radio frequency channels.

14. The method of claim 11, further comprising:

determining a first packet load on said first physical channel and a second packet load said second physical channel;

switching said first cable modem to said second physical channel if said first packet load meets at least one criterion with respect to said second packet load; and

switching said second cable modem to said first physical channel if said first packet load does not meet said at least one criterion with respect to said second packet load.

15. The method of claim 14, wherein said at least one criterion comprises said first packet load being greater than said second packet load.

16. The method of claim 11, wherein others of said plurality of physical channels carries video broadcast programming.

17. The method of claim 11, wherein said network comprises a broadcast switched network, and said switching is accomplished at least in part using a controller that also switches broadcast channels for delivery to subscriber premises.

18. A method for operating a cable modem in a cable network, the method comprising:

receiving IP packets on a first physical channel;

generating a request to receive a multicast transmission;

receiving information used as the basis of switching said cable modem to a second physical channel; and

switching said cable modem to said second physical channel.

19. The method as set forth in claim 18, wherein said first physical channel and said second physical channel comprise radio frequency channels carried on a coaxial cable.

20. The method as set forth in claim 18, wherein said act of generating is performed in response at least to a request to receive a multicast broadcast generated by another system in data communication with said cable modem.

21. The method as set forth in claim 18, wherein said act of receiving comprises the steps of:

receiving unicast IP packets on said first physical channel; and

receiving multicast IP packets on said first physical channel.

22. The method set forth in claim 21, further comprising demodulating a QAM modulated RF signal as part of said act of receiving.

23. Cable modem apparatus adapted to process network traffic comprising:

a digital signal processing unit capable of processing data from a first physical channel; and

a control unit configured to generate a request to receive a multicast transmission, to receive a message to switch from a first physical channel to a second physical channel in response to said request, and to configure said digital signal processing unit to process said second physical channel.

24. The cable modem apparatus as set forth in claim 23, wherein said control unit comprises software and a microprocessor for running said software.

25. The cable modem apparatus as set forth in claim 23, wherein said first physical channel comprises a radio frequency transmission centered at a first frequency and said second physical channel comprises a radio frequency transmission centered at a second frequency.

26. The cable modem apparatus as set forth in claim 24, wherein unicast IP packets and multicast IP packets are received on the same physical channel.

27. Apparatus adapted to control multicasting within a cable network, said cable network including a plurality of cable modems, comprising:

a cable modem termination system communicating with said plurality of cable modems; and

a controller adapted to track the state of multicast transmissions to said cable modems, said controller being able to detect that a cable modem assigned to a first physical channel of said network selects a multicast transmission available on a second physical channel, and instruct said cable modem to switch from said first channel to said second channel.

28. The apparatus of claim 27, wherein said apparatus is disposed substantially at the hub of a broadcast switched architecture network, and said controller is adapted to perform both said tracking, detecting and instructing, and control of the switching of other channels, said other channels carrying broadcast video content to a plurality of subscriber CPE.

29. In a cable network comprising a hub, a plurality of cable modems, and a set of physical channels providing communication between said hub to said cable modems, a method of operating said cable network to efficiently deliver multicast packetized transmissions, comprising:

transmitting a multicast transmission list message from said hub to at least a portion of said cable modems, said message listing a set of multicast transmissions and at least one corresponding physical channel on which each multicast transmission is being transmitted;

receiving a request to receive a first multicast transmission from said set of multicast transmissions; and

configuring at least one of said cable modems to process a physical channel associated with said first multicast transmission based at least in part on said multicast transmission list message.

30. The method as set forth in claim 29, wherein said request is received by said at least one cable modem from a client device in data communication with said at least one modem.

32. In a switched content-based network having a node and a plurality of subscriber devices adapted to receive packet service from said node, a method of conserving bandwidth during delivery of said packet service, comprising:

selectively switching one or more of a plurality of downstream packet channels only when they are required by one or more users being serviced by said node; and

selectively switching one or more of said subscriber devices to a packet service channels of said node so as to deliver a common multicast transmission to two or more of said devices using said packet service channel, said selective switching of said one or more devices obviating the need to replicate said multicast transmission on a second packet service channel.

33. Consumer premises equipment (CPE) adapted to selectively retune itself to at least one of a plurality of physical channels based at least in part on (i) a downstream communication received by said CPE that maps at least one multicast transmission to at least one physical channel, and (ii) a communication received from a client device in communication with said CPE requesting delivery of said at least one multicast transmission.