Efficient request access for OFDM systems

摘要

Systems and methods for efficient multiplexing of multiple access requests from disparate sources within a single OFDM burst. Each of multiple subscriber units employ non-overlapping groups of OFDM frequency domain symbols within a single burst for upstream transmission of their access requests. In one embodiment, the OFDM frequency domain symbols are differentially encoded to eliminate the need for transmission of upstream training information. In an alternative embodiment, the group of frequency domain symbols within the burst employed by any particular subscriber unit are contiguous to one another. Channel training for a give subscriber unit need only be performed over the subband occupied by its group of frequency domain symbols. This greatly reduces the number of training symbols required for reception. The reduction or elimination of training symbols increases the number of access requests that may be accommodated within a single burst and/or allows for greater redundancy in transmission of access request data.