Synchronization of distributed cable modem network components

1. A method for synchronizing operation of distributed cable modem termination system components, the method comprising:

operating a head end, a downstream transmitter hub, and an upstream receiver hub, each being components within the distributed cable modem termination system components, and also operating a plurality of cable modems for establishing frequency lock with a common frequency reference;

transmitting a plurality of time stamps from the head end to the plurality of cable modems via a packet data network, the downstream transmitter hub, and cable modem network plant;

operating each of the plurality of cable modems for performing smoothing operations on the plurality of time stamps to smooth jitter incurred within the plurality of time stamps during transmission via the packet data network and to establish phase lock with the head end; and

cooperatively performing ranging operations by the downstream transmitter hub, the upstream receiver hub, and the plurality of cable modems to establish phase lock among the plurality of cable modems and to synchronize clocks respectively included within each of the downstream transmitter hub the upstream receiver hub, wherein ranging operations as performed by the plurality of cable modems involving processing first ranging bursts received from the downstream transmitter hub and ranging operations as performed by the upstream receiver hub involving processing second ranging bursts received from the plurality of cable modems.

2. The method of claim 1 , wherein the ranging operations include adjusting counters of at least some of the plurality of cable modems.

3. The method of claim 1 , wherein:

the smoothing operations cause the plurality of cable modems to have phase offsets from one another; and

the ranging operations substantially remove the phase offsets among the plurality of cable modems.

4. The method of claim 1 , wherein the common frequency reference is a 10.24 MHz clock.

5. The method of claim 4 , wherein establishing frequency lock with the common frequency reference comprises locking Phase Locked Loops of the plurality of cable modems to the common frequency reference.

6. A distributed cable modem termination system, comprising:

a head end;

a downstream transmitter hub communicatively coupled to the head end by a packet data network; and

an upstream receiver hub communicatively coupled to the head end by the packet data network; and wherein:

a plurality of cable modems being communicatively coupled to the downstream transmitter hub and the upstream receiver hub by cable modem network plant;

the head end, the downstream transmitter hub, the upstream receiver hub, each being components within the distributed cable modem termination system components, and the plurality of cable modems operative to establish frequency lock with a common frequency reference;

the head end transmitting a plurality of time stamps to the plurality of cable modems via a packet data network, the downstream transmitter hub, and cable modem network plant;

each of the plurality of cable modems is operative to performing smoothing operations on the plurality of time stamps to smooth jitter incurred within the plurality of time stamps during transmission via the packet data network and to establish phase lock with the head end;

the plurality of cable modems, the upstream receiver hub, and the downstream transmitter hub are cooperatively operative to perform ranging operations to establish phase lock among the plurality of cable modems and to synchronize clocks respectively included within each of the downstream transmitter hub the upstream receiver hub; and

ranging operations as performed by the plurality of cable modems involve the plurality of cable modems processing first ranging bursts received from the downstream transmitter hub; and

ranging operations as performed by the upstream receiver hub involving processing second ranging bursts received from the plurality of cable modems.

7. The distributed cable modem termination system of claim 6 , wherein the ranging operations include adjusting counters of at least some of the plurality of cable modems.

8. The distributed cable modem termination system of claim 6 , wherein:

the smoothing operations cause the plurality of cable modems to have phase offsets from one another; and

the ranging operations substantially remove the phase offsets among the plurality of cable modems.

9. The distributed cable modem termination system of claim 6 , wherein the common frequency reference is a 10.24 MHz clock .

10. The distributed cable modem termination system of claim 6 , wherein each cable modem includes a Phase Locked Loop (PLL), and the cable modems are operative to frequency lock their PLLs with the common frequency reference.

11. A method for synchronizing operation of distributed cable modem termination system components, the method comprising:

operating a head end, a downstream transmitter hub, and an upstream receiver hub, each being components within the distributed cable modem termination system components, and also operating a plurality of cable modems for establishing frequency lock with a common frequency reference;

operating the head end, the downstream transmitter hub, the upstream receiver hub, and the plurality of cable modems for periodically extracting marker sequences from the common frequency reference;

upon receipt of a marker sequence, operating the head end, the downstream transmitter hub, and the plurality of cable modems for setting respective counters based upon contents of the marker sequence; and

cooperatively performing ranging operations by the downstream transmitter hub and the plurality of cable modems to establish phase lock among the plurality of cable modems and to synchronize clocks respectively included within each of the downstream transmitter hub the upstream receiver hub, wherein ranging operations as performed by the plurality of cable modems involving processing first ranging bursts received from the downstream transmitter hub and ranging operations as performed by the upstream receiver hub involving processing second ranging bursts received from the plurality of cable modems.

12. The method of claim 11 , wherein the ranging operations include adjusting counters of at least some of the plurality of cable modems.

13. The method of claim 11 , wherein the marker sequence comprises a Barker sequence.

14. The method of claim 11 , wherein the common frequency reference is a 10.24 MHz clock.

15. The method of claim 11 , wherein:

establishing frequency lock with the common frequency reference comprises locking Phase Locked Loops (PLLs) of the plurality of cable modems to the common frequency reference; and

the PLLs have a narrow bandwidth and do not lose frequency lock with the common frequency reference upon receipt of the marker sequence.

16. The method of claim 11 :

wherein establishing frequency lock with the common frequency reference comprises locking Phase Locked Loops (PLLs) of the plurality of cable modems to the common frequency reference; and

further comprising gating the PLLs during receipt of the marker sequences.

17. A distributed cable modem termination system comprising:

a head end;

a downstream transmitter hub communicatively coupled to the head end by a packet data network; and

an upstream receiver hub communicatively coupled to the head end by the packet data network; and wherein:

a plurality of cable modems being communicatively coupled to the downstream transmitter hub and the upstream receiver hub by cable modem network plant;

the head end, the downstream transmitter hub, the upstream receiver hub, each being components within the distributed cable modem termination system, and the plurality of cable modems operative to establish frequency lock with a common frequency reference;

the head end, the downstream transmitter hub, the upstream receiver hub, and the plurality of cable modems operative to periodically extract marker sequences from the common frequency reference and to set respective counters based upon contents of the marker sequence;

the plurality of cable modems, the upstream receiver hub, and the downstream transmitter hub are cooperatively operative to perform ranging operations to establish phase lock among the plurality of cable modems and to synchronize clocks respectively included within each of the downstream transmitter hub the upstream receiver hub; and

ranging operations as performed by the plurality of cable modems involve the plurality of cable modems processing first ranging bursts received from the downstream transmitter hub; and

ranging operations as performed by the upstream receiver hub involving processing second ranging bursts received from the plurality of cable modems.

18. The distributed cable modem termination system of claim 17 , wherein the ranging operations include adjusting counters of at least some of the plurality of cable modems.

19. The distributed cable modem termination system of claim 17 , wherein the marker sequence comprises a Barker sequence.

20. The distributed cable modem termination system of claim 17 , wherein the common frequency reference is a 10.24 MHz clock.

21. The distributed cable modem termination system of claim 17 , wherein:

establishing frequency lock with the common frequency reference comprises locking Phase Locked Loops (PLLs) of the plurality of cable modems to the common frequency reference; and

the PLLs have a narrow bandwidth and do not lose frequency lock with the common frequency reference upon receipt of the marker sequence.

22. The distributed cable modem termination system of claim 17 :

wherein establishing frequency lock with the common frequency reference comprises locking Phase Locked Loops (PLLs) of the plurality of cable modems to the common frequency reference; and

further comprising gating the PLLs during receipt of the marker sequences.