Design And Implement A Reliable And Secure Communication Algorithm Based On Network Coding In Mobile AD Hoc Networks

Mobile Ad Hoc Network(MANET)is a self-forming,self-healing,infrastructureless network consisting of a series of mobile nodes.A self-forming,self-healing,infrastructure-less network consisting of mobile nodes is a key technology enabler in military communication,tactical networking applications,sensor network as well as personal communications in general.Additionally,it has attracted more and more attention from academia and industrial circles.Network coding theory uses network nodes to deal with mathematical coding of data organically to get transmission gain.It may significantly increase network throughput and transmission reliability.It has been indispensable in modern network communication.Although network coding may bring a lot of benefits to network performance,it brings more complex security problems at the same time.In network coding system,the intermediate nodes make mixture operation on upstream nodes so that the errors in networks have the characteristic of propagation.Wireless network may be essentially different from wired network for it's broadcast nature.There is mutual interference between wireless network channels as well.These characters may result in low handling capacity,high bit-error-rates,high transmission delay and so on.Reliable data transmission method for wireless network has become one decisive factor affecting the transmission performance of wireless network.Reliability and security are basic requirements for MANET.This thesis designs and implements a secure and reliable communication algorithm based on network coding in MANET and mainly does the following work:1.Host nodes in MANET system based on network coding may be unable to decode data correctly when there exist hostile attack in network.Information leakage may also exist in this situation.Additionally,the existing secure network coding algorithm may have a series of problems such as low practicability,high bandwidth overhead and high complexity.To solve this problem,this thesis designs and complements secure network coding algorithm based on secret keys generated from channels.This algorithm generates secret keys by gathering channel parameters in time domain.Secret keys are connected to link state and this make secret keys unique and confidential.In addition,the intermediate nodes verify data packet received from upstream nodes.Contaminated information could be discarded to avoid bigger mistake.This significantly increase network handling capacity as well.Network coding theory is used in secret key exchange process as well,increasing key transmission rate and eradicating the possibility of key leakage.Experiment shows that secure network coding algorithm based on secret keys generated from channels performs better than traditional secure network coding algorithm in network convergence time and bit error rate.2.Wireless network could have high packet loss probability and error rate and the existing retransmission algorithm for MANET may have a series of problems.The retransmission gain is low and the complexity of algorithm is high.These problems make network reliability is seriously affected.To increase network reliability,this thesis designs and complements one cooperative retransmission algorithm based on instantly decodable network coding.This algorithm combines cooperative communication,link status and state feedback information to search the optimal cooperative node.The optimum node may have the best link quality with terminal nodes losing packets and have the best link with relay nodes.This method realizes dynamical packet retransmission and optimized retransmission encoding packet selection scheme to maximize transmission gain.By simplifying operations and rational control,the algorithm may possess lower complexity.The cooperative retransmission algorithm based on instantly decodable network coding not only increases transmission gain,it also reduces completion time.Additionally,network should have better reliability.Experiment shows that this algorithm obtains better performance in packet loss probability and network convergence time than traditional packet loss retransmission algorithm.