Synchronizing separated edge QAM devices located remotely from a CMTS

1. An edge quadrature amplitude modulator (edgeQAM) comprising:

a first counter driven by a temperature controlled oscillator;

a second counter driven by a voltage controlled oscillator;

at least one processor;

a local clock; and

the edgeQAM adapted to latch values of the first and second counters in response to receiving a time synchronization message from an external device, and to output the latched counter values to the at least one processor, and to compare a value of the second counter with the received time synchronization message to generate a phase error difference, and to adjust a frequency of the second counter according to the phase error difference, and applying the frequency of the second counter to the local clock.

2. A cable modem termination system (CMTS) comprising:

at least one processor; and

the CMTS adapted to operate the at least one processor to receive timing information from a plurality of cable modems each served by an edgeQAM; to average the collected timing information over a predetermined time interval; to estimate a clock error for the edgeQAM from the average timing information; and to communicate the estimated clock error to the edgeQAM.

3. The CMTS of claim 2 , further comprising:

a counter; and

the CMTS adapted to operate the at least one processor to latch a value of the counter in response to communicating a time synchronization message to the edgeQAM.

4. A cable modem termination system (CMTS) comprising:

at least one processor;

a canary clock corresponding to an edgeQAM;

a master clock; and

the CMTS adapted to operate the at least one processor to lock the canary clock to a downstream traffic stream of the corresponding edgeQAM; to estimate a phase error between the canary clock and the master clock; and to communicate the phase error to the edgeQAM.