Bandwidth efficient cable network modem

• US 7,486,722 B2
• Filed: 06/02/2003
• Issued: 02/03/2009
• Est. Priority Date: 04/18/2001
• Status: Active Grant

• Current Assignee: Collision Communications, Inc. (Concert Technology Corporation)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Russell, Edward D, Brommer, Karl D
• Primary Examiner(s): Fan, Chieh M
• Assistant Examiner(s): Ghulamali, Qutbuddin
• Application Number:
  US10/486,004
• Publication Number:
  US 20040244044A1
• Time in Patent Office: 2,073 Days
• Field of Search: 375/220, 375/221, 375/222, 375/224, 375/225, 375/219, 375/240, 375/324, 375/227, 725/111, 725/124, 725/126, 725/105, 725/110, 370/329, 370/342, 370/355, 370/431, 370/441, 370/347
• US Class Current: 375/222
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/71057 using maximum-likelihood sequence estimation [MLSE]
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04L 1/206 for modulated signals
• CPC Class Codes: H04L 5/1423 for simultaneous baseband signals

Abstract

A MUD enabled cable modem that provides efficient use of cable television network bandwidth in the presence of interference and noise is disclosed. The modem design provides for compatibility with existing network hardware and protocols so that bandwidth efficient modems configured in accordance with the principles of the present invention may be added to the network without removing installed hardware and software. A bandwidth efficient modem in the cable network head-end increases reverse link capacity from the terminals to the head end, while bandwidth efficient modems in cable network terminals increases forward link capacity from the head end to the terminals. Bidirectional bandwidth efficiency is thereby enabled.

Claims

1. A method for increasing bandwidth efficiency of a cable network including a head end Cable Modem Termination System (CMTS) communicatively coupled to a plurality of cable modems, the method comprising:

determining an attenuation profile associated with a propagation path of the network, so that each cable modem on that path has a known attenuation factor;

assigning each non-Multi User Detection (MUD) enabled cable modem that is associated with an attenuation factor below an established attenuation factor threshold to an unique time slot;

assigning two or more MUD enabled cable modems on the propagation path to a same time slot and on a same channel;

transmitting a channel assignment map that reflects the assignments for the cable modems;

simultaneously receiving in the same time slot and on the same channel requests from two or more cable modems responding to the transmitted channel assignment map; and

recovering each request using co-channel demodulation capabilities.

2. The method of claim 1 further comprising:

assigning each non-MUD enabled cable modem on the path to a unique time slot.

3. The method of claim 1 further comprising:

assigning each non-MUD enabled cable modem that is associated with an attenuation factor below an established attenuation factor threshold to a same time slot and on a same channel as one or more of the MUD enabled modems are assigned.

4. The method of claim 1 wherein the attenuation profile is determined by transmitting test signals of known power levels between the CMTS and each cable modem on the path, thereby allowing the attenuation factor associated with each modem relative to the CMTS to be identified.

5. The method of claim 1 wherein the attenuation profile is determined based on empirical data.

6. The method of claim 1 further includes broadcasting the attenuation profile to each cable modem on the path.

7. The method of claim 1 wherein the determining, assigning, and transmitting are carried out by a CMTS modem.

8. The method of claim 1 further comprising:

computing channel assignments based on each request; and

transmitting a second channel assignment map, wherein the second map includes a data grant for one or more modems that responded to the first channel assignment map.

9. The method of claim 8 further comprising:

providing data received from cable modems responding to the second map to corresponding destinations.

10. The method of claim 1 wherein the determining an attenuation profile enables the CMTS to exploit existing amplitude margin associated with reverse links of the cable network.

11. A method for enhancing forward link capacity of a cable network including a Cable modem Termination System (CMTS) that is communicatively coupled with a plurality of cable modems by a propagation path, the method comprising:

at a first cable modem

simultaneously receiving multiple signals transmitted in a same time slot and on a same channel, with each signal having a corresponding power level that is sufficiently high relative to a noise floor;

simultaneously recovering each signal using co-channel demodulation capabilities of the first cable modem;

removing recovered signals not intended for the first cable modem based on at least one of the header information and distinct power levels associated with each recovered signal;

at a second cable modem

simultaneously receiving the multiple signals, with the corresponding power levels of each signal attenuated based on an attenuation profile of the propagation path so that only one of the received signals has a power level that is sufficiently high relative to the noise floor; and

demodulating the one received signal having a power level that is sufficiently high relative to the noise floor using single channel modulation capabilities of the second cable modem, wherein the other attenuated signals are not detectable using single channel modulation capabilities.

12. The method of claim 11 wherein the second modem is physically located on or after a point in the propagation path associated with a known attenuation threshold, thereby ensuring non-detectability of the other attenuated signals by the second modem.

13. The method of claim 12 wherein the one received signal having a power level that is sufficiently high relative to the noise floor was transmitted at a first power level, and the other attenuated signals were transmitted at a second, lower power level.

14. A method of enhancing forward link capacity of a cable network including a Cable Modem Termination System (CMTS) that is communicatively coupled with a plurality of cable modems by a propagation path, the method comprising:

at a first cable modem

simultaneously receiving multiple signals transmitted in a same time slot and on a same channel, with each signal having a corresponding power level that is sufficiently high relative to a noise floor;

simultaneously recovering each signal using co-channel demodulation capabilities of the first cable modem;

removing recovered signals not intended for the first cable modem based on at least one of the header information and distinct power levels associated with each recovered signal;

at a second cable modem;

simultaneously receiving the multiple signals, with the corresponding power levels of each signal attenuated based on an attenuation profile of the propagation path so that each signal still has a power level that is sufficiently high relative to the noise floor;

simultaneously recovering each signal using co-channel demodulation capabilities of the second cable modem; and

removing recovered signals not intended for the second cable modem.

15. The method of claim 14 wherein each of the signals recovered using co-channel demodulation capabilities of the second cable modem were transmitted at substantially the same power level.

16. A cable modem which enables efficient use of bandwidth in a cable network including a plurality of cable modems, the cable modem comprising:

a multiuser detection module adapted to simultaneously demodulate and recover K interfering signals transmitted at the same time on the same channel using co-channel demodulation;

a data formatting module operatively coupled to the multiuser detection module, and adapted to produce network data packets for at least one of the K recovered interfering signals; and

a control processor operatively coupled to the data formatting module, and adapted to exploit existing amplitude margin associated with one or more propagation paths of the cable network by deliberately scheduling interfering transmissions based on known attenuation characteristics of the one or more propagation paths wherein the network includes a propagation path having both Multi User Detection (MUD) enabled and non-MUD enabled modems, and the control processor is further adapted to assign each non-Mud enabled cable modem that is associated with an attenuation factor below an established attenuation factor threshold to a unique time slot, thereby enabling a legacy protocol mode.

17. The modem of claim 16 wherein the control processor is further adapted to assign each non-MUD enabled cable modem that is associated with an attenuation factor equal to or above an established attenuation factor threshold to a same time slot and on a same channel as one or more of the MUD enabled modems are assigned.

18. The modem of claim 16 wherein the control processor includes:

a data format interface module configured for bidirectional communication, and adapted to interface the control processor with the data formatting module; and

a data format selector module configured to allow selection of one or more data format modes in which the data formatting module is capable of operating.

19. The modem of claim 18 wherein the data format interface module is further configured to remove recovered signals not intended for the cable modem.

20. The modem of claim 16 wherein the control processor includes:

a digital signal level detector module configured to detect the signal level of recovered signals; and

an attenuation profile module configured to compute and store attenuation factors associated with other modems of the network.

21. The modem of claim 20 wherein the attenuation profile module is further configured to compare received signal levels of actual user signals to known attenuation factors to determine which modem in the network sent the signal.

22. The modem of claim 16 wherein the cable modem includes a modulator, and the control processor further includes:

a channel assignment module configured to provide data and corresponding time slot and channel assignments based on the known attenuation characteristics to the modulator.