Adaptive Channelization For High Data Rate Wireless Networks

High data rate wireless networks (1 Gbps and up) are in the horizon and several standards are in the works. However, the task of designing multiple access protocols for such networks is fraught with new challenges as the bandwidth independent overheads dominate. We show that even when such overheads are kept at a minimum, the performance of multiple access protocols can be very poor. However, perfor mance can be improved significantly by splitting the given bandwidth into multiple channels and running the multiple access protocol independently on these channels. Taking an 802.11-like CSMA/CA (DCF) protocol as an example we show via a modeling exercise how such channelization can improve performance and why it needs to be adaptive to traffic demand. We develop an Adaptive Multichannel (AMC) protocol and study its performance via simulations. In addition, we also investigate a single-channel ExtendedReservationprotocol in a high speed setting. Here, a sender, upon winning the contention, reserves the channel for multi ple packet transmissions. We show that the Extended-Reservati on protocol performs better than the single channel 802.11-li ke DCF protocol and is comparable to adaptive multichannel protocol (AMC), but it suffers from an inherent unfairness issue due to which many nodes starve for channel access. The multichannel protocol, on the other hand, is devoid of any fairness problems. Finally, we develop a ‘scaled down’ prototype implementation using the USRP/GNURadio platform to demonstrate that adaptive channelization can be practical using appropriat e programmable radio hardware and has tremendous performance potential. Taking our modeling, simulation and experiment al results together, our work shows that a throughput gain of a factor of 2 is not unrealistic.