ETHERNET OVER MULTI-CARRIER FREQUENCY-DIVISION MULTIPLEXING (FDM)

摘要

An architecture for providing high-speed access over frequency-division multiplexed (FDM) channels allows transmission of ethernet frames and/or oth er data access a cable transmission network or other form of FDM transport. The architecture involves downstream and upstream FDM multiplexing techniques to allow contemporaneous, parallel communications across a plurality of frequen cy channels. Moreover, an automatic frequency control resolves some issues of a free-running clock (4708) in an upstream tuner of the central concentrator b y performing adjustments based on the average frequency error of a number of active upstream tones. In the preferred embodiments of the present invention , the automatic frequency control (AFC) utilizes a feedback loop for at least each active upstream tone (Fig. 47). Also, the average of the active upstrea m tones is determined and is utilized in providing feedback to adjust the automatic frequency control (AFC).