Relay Selection Scheme For Cooperative Communication Systems

In the cooperative communication system,the use of cooperative relay technology can help the source to transmit data.Thus,the receiver can obtain additional diversity gain,greater system capacity and more efficient transmission performance.So it is widely studied by scholars in the field of cooperative communication.It is an important content of cooperative communication to select suitable relays from the candidate relay set and allocate power for each node according to the instantaneous Channel State Information(CSI)and at the premise of improving energy efficiency as well as received Signal-to-Noise Ratio(SNR).The paper studies relay selection schemes based on the cases of single-source and multi-source according to resource conditions and performance indexes of the cooperative communication system.Firstly,as the instantaneous CSI of source to relay and relay to destination affects the average Symbol Error Rate(SER)of the system,the paper proposes an adaptive relay selection scheme based on the instantaneous CSI.Only when the direct link is unable to provide reliable transmission,the scheme selects the best relay for the instantaneous CSI of two stages to carry out cooperative transmission.And in order to ensure further reliable transmission,the relay can select the strategy of decode and forward or decode amplify and forward adaptively.The average SER of the system is reduced correspondingly.Then,compared with other studies that deal with the exact SNR,a combined relay selection and power allocation scheme based on approximate high SNR is proposed to enhance the energy efficiency.In this scheme,the expressions of relay selection and power allocation are derived by using simple formula of approximate high SNR and the maximization criterion of energy efficiency.The compromise method between energy efficiency and spectrum efficiency in the two hop relay system is also designed.Finally,the multi-source relay selection scheme is studied.The proposed scheme based on the hybrid improved genetic algorithm is different from the current situation of assigning a suitable relay for each source.The system's model of multi-source relay selection is established with the criteria of maximizing the minimum received SNR of each link.According to the model,the hybrid improved genetic algorithm is proposed to assign a number of suitable relays for each source.The received SNR of the system is improved correspondingly.