The clocks of one or more edgeQAM devices are synchronized with a master clock at the remotely located CMTS. A master clock signal may be transmitted via a dedicated gigabit Ethernet link. Alternatively, master clock information contained in a time synchronization message may be transmitted for use in adjusting local oscillators that drive local clocks at respective edgeQAM devices.In another embodiment, the downstream sample rate to particular edgeQAM devices may be sampled and used to lock a local clock at respective canary modems dedicated to each edgeQAM device. A canary modem's clock is compared to the master clock, and a resulting phase error is communicated to the respective edgeQAM device for use in adjusting its local clock. Or, TDMA upstream ranging burst average trends are used to estimate edgeQAM clock error. Each respective edgeQAM uses this error to adjust its clock.