Adjustable multiple relay selection for cooperative communication

In this paper, an adjustable multiple relay selection (MRS) scheme for cooperative communication with amplify-and-forward (AF) relay under frequency selective channels is proposed. In the proposed scheme, the relays are ordered firstly by the end-to-end SNR, then the relays are sequentially selected out from N relays and the number of cooperating relays is adjusted dynamically according to the current channel state information. The aim of this work is to dynamically estimate the optimum number of cooperating relays. ‘Optimum’ means the minimum number of cooperating relays achieving the maximum level of combined SNR. Numerical results verify the analyses and show that the scheme can adaptively adjust the number of cooperating relays, and outperform conventional relay selection schemes. Hence, the proposed scheme provides better tradeoff between BER performance and spectral efficiency and to save more energy in cooperative wireless networks.