Research And Implementation Of A Hybrid MAC Protocol In MANET

A Mobile Ad Hoc Network(MANET)is a wireless communication network with no need of fixed infrastructures,so it is capable of rapid deployment.The topology of a MANET can be arbitrarily changed,which makes it very suitable for battlefield,rescue and other special environment.Due to the distributed control features,the Multiple Access Control(MAC)protocols becomes the core technology that affects network performance.Of all the existing MAC protocols,those contention ones,such as ALOHA and CSMA,result in low network throughput,especially under heavy load.On the other hand,those allocation protocols,such as TDMA,introduce an extra random delay before a frame transmission.In some dynamic TDMA protocols,it also has to take some time to make slot reservation for the purpose of resource efficiency.Generally,TDMA is able support heavier service load,but frame delay increases under the condition of burst data.A number of hybrid protocols,which are almost based on contention access,were proposed,have more control overhead.To shorten the access delay of TDMA protocols,a hybrid MAC protocol based on Time Division Multiple Access,SDC-MAC,is proposed.In this protocol,the fixed time slots are used to guarantee the basic capability to access channel after the node enters the network.Under the condition of continuous heavy load,the nodes are able to dynamically reserve the time slots by a three-step handshake protocol.The contention access in SDC-MAC is adopted to quickly occupy idle time slots with burst data arrivals.This protocol effectively integrates fixed timeslot allocation,dynamic timeslot reservation and contention access.It can provide higher network performance in a variety of network environments.With the network throughput and average access delay as main performance targets,the SDC-MAC protocol is modeled and simulated on the OPNET platform.Comparing with the traditional USAP protocol and CSMA/CA protocol,the SDC-MAC protocol has higher throughput and lower packet access delay.At last,the SDC-MAC protocol is implemented on the hardware platform of MANET,which verifies its correctness and validity.