Throughput and Fairness in A Hybrid Channel Access Scheme for Ad Hoc Networks
CALIFORNIA UNIV SANTA CRUZ DEPT OF COMPUTER ENGINEERING
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A novel hybrid channel access scheme that combines sender-initiated and receiver-initiated collision-avoidance handshakes is proposed for multi-hop ad hoc networks. The scheme is based on the observation that a receiver-initiated scheme is more appropriate when receivers are more knowledgeable of the contention around themselves and can compete for the channel more effectively. By adaptively sharing the burden of initiating the collision-avoidance handshake between the nodes that experience different levels of contention, better fairness may be achieved with almost no degradation in throughput. An attractive feature of the new scheme is that it is a simple extension to the existing IEEE 802.11 MAC protocol, and it maintains compatibility with the standard. The new scheme involves adding very simple queue management and book-keeping work mechanisms. Simulation experiments of the IEEE 802.11 MAC protocol and the new scheme show that, although the proposed hybrid scheme does not solve the fairness problem conclusively, it does alleviate the fairness problem in some cases without sacrificing much throughput and simplicity. The difficulty of improving fairness for TCP-based flows is demonstrated. A promising topic for future work consists of combining the new hybrid scheme with some proposed mechanisms that try to approximate fair queueing for ad hoc networks to achieve some QoS assurances. Without explicit information exchange among nodes, the fairness problem cannot be solved conclusively.
- Computer Systems
- Computer Systems Management and Standards
- Radio Communications