Medium Access Control Protocol In Ad Hoc Networks

There exist hidden terminal, exposed terminal and multi-network co-exist problems in wireless Ad hoc networks. Every medium access control protocol designed for ad hoc networks must have the ability to resolve such problems mentioned above. In this thesis, three type MAC protocols - which operate beyond the single channel, dual channel and multi-channel assumption individually - are researched, and some achievements are obtained:1. some improvements to IEEE 802.11 MAC protocol are proposed: adding Invite to Send mechanism, treating packet transmittion error event independently with the node contaction error event, strengthening cooperation relationship between MAC layer and network layer, and sensing channel state by inspecting the signals. Simulation results show that these proposals can improve the ability to resolve the hidden and exposed terminal problems markedly.2. a new protocol which can resolve the hidden and exposed terminal problems thoroughly - named DBTMAC, is proposed. In DBTMAC protocol, every node which may invoke the hidden and exposed terminal problems is restrained to access the channel for transmitting something, thus those problems could not be occur again. Simulation results prove the validity of the DBTMAC protocol.3. a cluster-based multi-channel MAC protocol - CMMA, is proposed. In CMMA protocol, different communication channels are distributed between different clusters in order to avoid hidden and exposed problems; channel distribution is performed by the co-channel interference detection algorithm and the no-collision requirement is also assured by the algorithm. CMMA protocol has low control cost and fast co-channel interference detection characteristic. Simulation results prove its validity in resolve the multi-network co-exist problem, show that it can work well in the scenario where exist some connectionless sub-networks.