Networking In Wireless Ad Hoc Networks Using Directional Antennas

Wireless Ad Hoc network performance will make a remarkable progress with direcional antennas.The MAC protocol controls the access to the physical layer and plays an important role in communication.Most of the existing MAC protocols using directional antennas are based on the classical MAC protocol using omni directional antennas,such as Aloha protocol,CSMA/CA protocol and TDMA protocol.Among these protocols,the MAC protocol based on TDMA can avoid conflicts by specific frame structure and slot reservation.These protocols all have the problems including the complex control algorithms,the unavoidable conflicts and the low resource utilization.In order to solve these problem,we introduce the directional multibeam antennas into wireless Ad Hoc networks and take the Rotman lens antennas as an example.The processes of neighbour discovery is modelled and formulated for different types of antennas and scanning modes.The results show that the directional multibeam antennas have an advantage over the directional single beam antennas in wireless Ad Hoc networks.Therefore,we use the directional multibeam antennas when designing MAC protocls.In this paper,the SM-RMAC protocol is designed for the Rotman lens antennas with single transmission and multiple reception.Based on the existing researches,neighbour discovery is simplified with Rotman lens antennas.A new resource state table is further given so that the reservation can be arranged efficiently and conflict free.The reservation of slots can also be made according to different traffic priorities for achieving differentiated services.Simulation results show that RMAC can avoid conflicts and make full use of Rotman lens antennas,which yields a more stable and higher throughput compared with existing protocols.Based on the SM-RMAC protocol,MM-RMAC protocol is designed for the Rotman lens antennas with multiple transmission and multiple reception.Firstly,we reseach on power calculation and power constraints in multi-transmission-multi-reception mode.Secondly,slot reservation and resource status table is improved taking power control into consideration.Thirdly,the priority queue mechanism is proposed to support traffic priorities.Compared with the SM-RMAC protocol,the MM-RMAC protocol yeilds a stronger network capacity,a shorter average delay and a higher energy efficiency.