New Hybrid Channel Access Scheme for Ad Hoc Networks

摘要

Many contention-based channel access schemes have been proposed for multi-hop ad hoc networks in the recent past, and they can be divided into two categories, sender-initiated and receiver-initiated, according to the collision avoidance handshake in use. The sender-initiated scheme is adopted in the IEEE 802.11 Medium Access Control (MAC) protocol, which is by far the most popular and studied protocol. However, the IEEE 802.11 MAC protocol can experience serious fairness problems due to location-dependent contention and the binary exponential backoff it uses. On the other hand, a receiver-initiated collision avoidance handshake is more effective at the receiver's side. Hence, the authors propose a hybrid channel access scheme that combines both sender- initiated and receiver-initiated collision avoidance schemes. The new scheme involves only some additional queue management and book-keeping work while maintaining compatibility with the existing IEEE 802.11 protocol. Simulation experiments show that the new scheme is very effective, as it can achieve much better fairness than the original sender-initiated scheme with almost no degradation in throughput. The hybrid scheme also eliminates the need for a good traffic estimator, which is usually mandatory in pure receiver-initiated schemes.