Power Allocation Algorithms For Vehicular Cooperative Communication System

Cooperative communication technology is a virtual antenna technology, which is the distillation of the concept of multiple-input multiple-output (MIMO) technology. This technology uses antennas of other users as relays in wireless networks to achieve space diversity and full diversity gain. As the technology of the vehicles continues to improve, vehicles equipped with wireless communication devices are poised to deliver vital services in the form of safety alerts, traffic congestion probing and on-road commercial applications. In vehicular communication system, a car is viewed as a mobile node which can not only communicate with base station but also help other nodes to communicate. This is the vehicular cooperative communication system.Power distribution is an important element in vehicular cooperative communication system, which directly affects the quality of the whole system performance. Its purpose is to reduce the energy loss and interference of the users. This paper focuses on the power allocation algorithms in amplify-and-forward cooperative communication system. Firstly, a mathematical derivation of the power allocation algorithms in vehicular communication is described theoretically. Then a large number of simulations prove the correctness of the mathematical derivation, reaching some important conclusions as well. The main contributions of this paper are as follows:1. Research on the basic principles of cooperative communication in vehicle communication system and analyzes the key techniques such as forwarding principle, partner selection principle, and receiver combing principle. A mathematical model of single relay system is also constructed for the derivation of power allocation algorithms. 2. First, it derives formulas of channel capacity and received signal-to-ratio (SNR) in single relay system based on instantaneous channel state information when the receiver adopts Maximum Ratio Combining, Equal Gain Combining, Fixed Ratio Combining and Enhanced SNR Combining respectively. With a limit power sum of transmitter and repeater, it presents optimal power allocation schemes based on maximum channel capacity principle and maximum SNR principle respectively. On the basis of theoretical research and mathematical derivation, a improved power allocation algorithm about vehicular communication system is given:set different priorities to two signals which are superimposed at the receiving part in order to adapt to different vehicle environments.3. On the basis of Manhattan mobility model and Gauss-Markov mobility model, vehicular mobility model is proposed which is capable of describing car movement in environment where city block places exist. On the basis of theoretical research and vehicular mobility, a lot of simulations have been done, and simulation results prove the correctness of the mathematical derivation of optimal power algorithm scheme.