Study On Protocol Optimization Of MAC Layer Under Misbehavior Constraints

In recent years,wireless networks have developed rapidly,and wireless networks have spread throughout people's lives.But when wireless networks bring unlimited convenience to people's lives and work,they are also accompanied by danger.Network security problem is always the key point of the study,researchers mostly study the behavior of malicious attacks from stealing network behavior,but misbehavior is also a part of the network security problem.Misbehavior seriously affects the fairness of the network performance and communication,Therefore,selfish behavior is also a problem of network security that can not be ignored.The research on defense strategies for selfish behavior is of great significance.This thesis focuses on the misbehavior of the MAC layer and its defense strategy,and proposes MC-MAC optimization schemel for the misbehavior of modifying backoff value,then studies the software radio platform,realizes and tests the MC-MAC schemel on GNU Radio and USRP platform.The main work of this thesis is as follows:1.This thesis proposes MC-MAC optimization schemel,which is based on IEEE802.11 DCF,modifies the frame structure of RTS/CTS,adds reputation mechanism and penalizes backoff generating function.Then,Markov model is used to verify the effectiveness of the penalty mechanism of MC-MAC schemel.NS3 simulation shows that the performance of MC-MAC schemel is similar to IEEE802.11 protocol in the network without misbehavior nodes.And in the network with misbehavior nodes,MC-MAC schemel can maintain the throughput of the good nodes at the MP of 1%-80% and restrain the misbehavior nodes.2.The implementation of the MC-MAC schemel utilizes OSI.The physical layer and MAC layer are implemented by software on GNU Radio and USRP platforms,and TUN/TAP is used as the interface to connect the protocol layer of LINUX system.In the test phase,Because the delay of software radio platform will affect the performance of MAC protocol,this paper first tests the delay of the platform,then analyses the influence of the value of the delay correction parameter beta on the protocol.The results show that With the improvement of beta,although the packet loss rate of the protocol can be effectively reduced,but the throughput of the protocol is greatly reduced.Then the function of MC-MAC schemel is tested,For the detection mechanism of the protocol,the deviation value of the detection mechanism under different beta values is tested.The test results show that the larger the beta value is,the smaller the deviation value is.For the function of the reputation mechanism of the schemel.The test results show that the reputation mechanism of the schemel can restrain selfish nodes.