| Two developments in recent years have revolutionized the way people work. Computer networking has enabled computer users to communicate and access information distributed throughout the world. Portable computing has enabled mobile users to work anytime, anywhere. Mobile computing seeks to realize the benefits of both portability and network connectivity. A major technological challenge in mobile computing is to provide mobile users with adequate wireless networking capability to communicate and access information world-wide. This work addresses the above challenge.; The wireless medium is a scarce shared resource in a mobile computing environment, and is usually the performance bottleneck. Thus wireless medium access is a critical activity in mobile computing/communications, Important issues in wireless medium access include low bandwidth, spatially dependent congestion, hidden and exposed stations, interference, capture, channel noise, colocated cells, etc. The desired goals in wireless networking protocols are efficiency, fairness, robustness, scalability and support for data/voice/video. This work proposes and analyzes a new generation of algorithms for wireless medium access which achieve the desired goals. The algorithms are generally applicable to a variety of wireless infrastructures. An implementation of the algorithms demonstrates their efficacy in a realistic mobile computing environment.; Four major algorithms have emerged as a consequence of this work. They are the following. (a) a dual-channel multi-access collision avoidance algorithm for efficient channel access, (b) a contention measurement and backoff propagation based collision resolution algorithm for fair channel access, (c) a multiple tokens algorithm for scalable and flexible channel access, and (d) an efficient security protocol for authenticated and secure channel access. The BAPU wireless medium access protocol implements the above algorithms in an indoor wireless LAN environment.; Experimental measurements, analysis and simulations have shown that BAPU achieves an order of magnitude performance improvement over the emerging IEEE 802.11 standard. This work presents the performance results and makes recommendations to improve the wireless medium access protocol standard. |
