Research On Optimal Power Allocation Of Two-Way Channel Estimation In IOV

With the increasing number of vehicles,the corresponding traffic conflicts are more and more obvious,such as terrible traffic jams and frequent traffic accidents,so the IOV(internet of vehicles)has been widely studied as the core of intelligent traffic.With the help of wireless communication technology,IOV completes the information exchange among vehicles,people and infrastructures.However,due to the limited spectrum resources and restricted invehicle equipment power,new challenges are coming on the wireless communication technologies in IOV.To solve the problem mentioned above,spectrum sensing and cooperative relay communication are studied in this paper.The spectrum sensing,which detect spectrum holes to communicate,effectively relieves the spectrum tension problem and provides the signal synchronization information for cooperative relay system,too.With network coding and power allocation,cooperative relay system increases coverage area,the channel capacity and the spectral efficiency,as well as reduces the communication bit error rate.This paper firstly introduces the research background and development.It gives a detailed introduction about key technologies in channel estimation of IOV wireless communication system,which forms the ground work of the entire paper.These key technologies include spectrum sensing,two-way relay network analyzing,multi-relay space-time coding and typical channel estimation method.Secondly,we propose a new detection algorithm based on spectrum variance to detect modulated signal.This method divides the analyzed spectrum band into several blocks and then calculate the sum of their energy variances,by setting a proper threshold value,it can recognize whether a modulated signal is present or not.Numerical results indicate that about 5d B lower signal-to-noise ratio(SNR)is needed to detect modulated signal in provided algorithm compared with traditional method.Considering some car moves fast in IOV,this paper also introduces and analyzes the existing cyclostationary feature based quickest spectrum sensing and universal spectrum sensing schemes with advantages and disadvantages.Thirdly,considering the scenarios of one single relay for multiple users in IOV,a multiple users two-way relay network model is studied.We resort to linear minimum mean square error to achieve the individual channel estimation without ambiguity through two consecutive segments,from which the optimal power allocation strategy from the relay for different sources is obtained.Numerical results show that the proposed method outperforms the existing ones when relay power in low SNR region.Simultaneously,the system performance of different source numbers is presented,which provides a reference for choosing optimal number of communication users in relay when design a real system.Finally,considering the scenarios of multiple relays for two users in IOV,a two-way multirelay network model for two users is introduced.Based on the distributed space-time coding and linear minimum mean square error,we design the corresponding channel estimation strategy,and then investigate the optimal power allocation at each relays when every relay power is finite.Simulation results validate that the provided scheme outperforms existing ones.With the help of simulation results of system performance under different relay numbers and take tradeoffs between mean square error and bit error rate,we could give the hint for choosing the proper relay number in practical system.