Criterions of designing codebooks and a relay selection scheme for a relay network

Summary For a relay network system with amplify and forward protocol, in this paper, analysis of performance is conducted, and an upper bound of pairwise error probability is obtained. Moreover, a scheme of relay selection is analyzed under assumptions that (i) the relays amplify and forward received signals without any signal processing; (ii) the receiver only knows channel state information from the relays to the receiver; and (iii) the transmitter and the relays do not have any channel state information. Based on the upper bound, a criterion of designing codebook is proposed. Surprisingly, this bound shows that increasing the number of relays can hardly improve performance. Furthermore, the error probability is decreasing with a speed of P−1, no matter how large the relay number is, where P is the total energy. Also, for the relay selection, the optimal selecting way is to select only one relay with the largest channel gain, which is very different from existing schemes. These results are all confirmed by simulations. Copyright © 2015 John Wiley & Sons, Ltd.