Research On VANET Relay Technology With Channel Feedback

VANET,known as Vehicle-to-Everything(V2X)currently,is an important component of the 5G.It finds broad applications in safe driving and intelligent transport system.Direct communication in Vehicle-to-Vehicle(V2V)shows disadvantages of short communication range,fast channel variation and low spectral efficiency.Hence,relay technology is used to extend the coverage of V2V communications.Moreover,adaptive modulation techniques are added to enhance spectral efficiency.This thesis mainly focuses on the application of relay technology and adaptive modulation into VANET.The main works of the thesis are as follows.Firstly,the research background and current status of VANET,relay and adaptive modulation technology are introduced.The combined system model of relay and adaptive modulation technology is proposed.The corresponding bit error rate(BER),spectral efficiency and outage probability are derived.Secondly,the performance of the joint relay adaptive modulation scheme is studied.System performances under different power allocation are analyzed.In addition,the probability that a modulation mode is correctly selected in condition of incomplete channel feedback is derived in theory.An improved power allocation method is proposed,which can increase selection correctness of a modulation mode.A improved method of channel feedback is adopted to ensure the quality of service of the joint relay adaptive modulation scheme.Thirdly,the performance of the independent relay adaptive modulation scheme is studied.System performances under different power allocation are analyzed.In addition,the method of modulation mode selection is improved.A new modulation selection method is proposed without loss of spectrum efficiency.System error rates decrease significantly after using this method.Finally,a suitable relay adaptive modulation scheme is applied to the V2V environment.Effects of channel feedback error and Doppler spread on error rate and spectrum efficiency are analyzed.Subsequently,solutions are proposed.Moreover,the simulation results prove that the proposed scheme in this thesis can effectively improve spectrum efficiency of V2V communication.