Research On Spectrum Sharing Mechanism Of Cognitive Vehicular Network Considering Fairness

The emergence of intelligent transportation systems meets the demand for entertainment and security in today's society.However,the increasing use of intelligent communication devices has increased the pressure of communication,resulting in the scarcity of spectrum resources in the network.Using spectrum sharing mechanisms to optimize dynamic spectrum resources has become a key technology for improving resource utilization and network performance in cognitive vehicular network research.The ability to allocate spectrum resources fairly and effectively is an important criterion for checking the quality of the spectrum sharing mechanism.Due to the high-speed mobility of cognitive vehicular networks,the network topology changes drastically.Using existing spectrum sharing mechanisms based on cognitive radios has phenomena of high packet loss rate,small throughput and long delay,and does not adapt to the dynamic vehicular network environment.Therefore,under the complex vehicular network environment,improving the spectrum sharing mechanism to achieve fair and efficient resource optimization is an urgent problem to be solved at present.In view of the above problems,this paper proposes two spectrum sharing schemes and the main research work of the thesis is as follows:(1)A multi-objective cuckoo search spectrum allocation algorithm based on decomposition is studied.Aiming at the problem that traditional multi-objective optimization algorithms are easy to fall into the local optimal solution,a spectrum allocation model based on interference constraint to maximize the average throughput and efficiency fairness is established for cognitive vehicular network.A multi-objective cuckoo search spectrum allocation algorithm based on decomposition is proposed and the application of the algorithm in the discrete problem model is improved.The standard test functions are used to test the algorithm.At the same time,the multi-objective cuckoo search algorithm based on decomposition is used to solve the spectrum allocation problem of cognitive vehicular networks.(2)Research on spectrum access back-off algorithm based on relative remaining time.For the problem that the BEB back-off algorithm in the DCF mechanism cannot guarantee the fair access channel of vehicular users,an adaptive back-off algorithm based on the relative remaining time is proposed.The algorithm considers the dynamic network environment and uses the mobility parameters such as vehicle's speed and location to calculate the relative remaining time of data transmission.The threshold of packet collision probability is set to determine the load of the network,and different back-off strategies are proposed for low and high load networks.Besides,the throughput,fairness and packet loss rate are also analyzed.(3)The realization of the cognitive vehicular network system based on NS3.The vehicle model,highway model and mobile model are designed in the cognitive vehicular network scene module to simulate the movement and communication of vehicles on the highway.The network equipment,the MAC layer and the physical layer protocol of the vehicle model are configured and the dynamic NetAnim interface is designed to realize the visualization of the dynamic network communication.