An adaptive multicarrier wireless access system

Broadband wireless technology appears to be one of the competitive solutions for the last mile problem. Wireless access systems enable one to incrementally roll out infrastructure and rapidly turn up new services such as high-speed Internet access and video distribution. In this paper, implementation challenges toward an adaptive orthogonal frequency division multiplexing (OFDM) point-to-multipoint outdoor broadband wireless access system are examined. The frequency band tackled is located at 10.5 GHz but the results can be applied to other areas of the spectrum as well. The targeted bit rates go up to 34 Mbps, for varying channel conditions. Dynamic time division multiple access/time division duplex (DTDMA/TDD) is selected for the medium access scheme, since TDD requires only a single unpaired frequency band (thus reducing the cost for purchasing licensed spectrum), while TDMA distributes the number of slots per uplink or downlink direction according to the traffic that each direction has to transmit. In addition, OFDM techniques provide a robust behavior in the presence of multipath fading. This paper focuses on the wireless data link control (W-DLC) layer, addressing the system protocol stack and all W-DLC sublayers, entities and functions, and providing a framework that will be beneficial for a licensed outdoor wireless system.