SCALABLE COMMUNICATION SYSTEM USING OVERLAID SIGNALS AND MULTI-CARRIER FREQUENCY COMMUNICATION

摘要

A multi-user OFDM or DMT communication system has nodes which are allowed to transmit continuously on one or just a few of the system's frequency sub-channels, while the other nodes avoid putting any signal into those sub-channels. Simple low data rate nodes are allowed to use a small number of sub-channels while more complicated nodes use the remainder, and preferably functionality is provided to ensure that adjacent sub-channels are reliably spaced apart in frequency so that they do not bleed over into one another; to ensure that signals from all nodes arrive at the base station with well-aligned symbol transitions (symbol synchronization); and to ensure that signals from the various nodes arrive at the base station with similar power levels (power control). Frequency assignment strategies at a base station range from one fixed sub-channel per node to a hopped group of sub-channels per node.