Research On Directional MAC Protocol For Ad Hoc Networks

Due to its flexible,support mobility,easy to quickly expand,invulnerability ability and low cast,wireless ad hoc network has been widely used in vehicular network,emergency rescue and military tactical networks.However,with the expansion of the various applications,ad hoc network with omni-directional antenna cannot meet the demand for network capacity and transmission quality.Therefore,the advantage of directional antenna in antenna gain,transmission range and anti-jamming capability,can greatly improve the performance of mobile Ad hoc network.The use of directional antennas in wireless ad hoc nework has many advantages,at the same time,it introduces the deafness problem as well as the hidden-terminal problem due to asymmetry in gain.Therefore,in order to make the best use of the directional antenna advantages and minimize the above problems,the paper focuses on how to design efficient MAC protocol.First,we design a directional antenna model with adjustable beamwidth and number in NS-3.We simulate the DVCS protocol,which is a basic DMAC protocol.Some primary capabilities are added to the original WLAN model: switching antenna beam,caching the Angle of Arrival,beam locking and unlocking,and use of DNAVs.The simulation results indicate that the use of directional antennas improves the throughput of Ad hoc networks,reduces the interference between nodes,improves the packet delivery rate and shortens the packet average delay.Since the CRCM protocol do not need any information about each other's location,it sends circular directional RTS and CTS packets to deal with the deafness problem as well as the hidden-terminal problem due to asymmetry in gain.Second,we analyze the adaptability of the CRCM protocol,which is belong to the multi-directional sequential RTS.The simulation results indicate that the CRCM protocol effectively solves the problem of directional MAC,compared to the DVCS protocol and omnidirectional MAC protocol,the CRCM protocol improves the network throughput and is better able to adapt to the mobile scenarios.At last,Since the CRCM protocol has a low communication efficiency for a large number of continuous and stable packets business model,this paper proposes an improved CRCM protocol.In order to improve the transmission efficiency of the protocol,we reasonably reduce the number of circular RTS and CTS packets and modify the random backoff algorithm.We analyze the protocol the simulation results indicate that the proposed protocol reduces the overhead of control,improves the transmission efficiency,improves the network throughput as well as shortens the packet average delay.