Simple switch-based relay selection for amplify-and-forward cooperative diversity on rayleigh fading channels

Amplify-and-forward cooperative diversity with simple switch-based relay (SSR) selection is addressed. With the SSR selection, dual-hop relaying is not always used for transmissions. Only when the signal-to-noise ratio (SNR) of the source-to-destination (SD) channel is lower than a preset threshold, the relays are tested one-by-one by comparing their SNR with the threshold. If the SD signal is not satisfied, with the SSR selection scheme, the first relay whose SNR is larger than the threshold is selected and its signal is combined with the SD signal by using maximal-ratio combining (MRC). The SSR selection scheme can save the total processing resource compared to the best-relay selection scheme. For performance evaluation, the bit error probability (BEP) of BPSK on independent and identically distributed (i.i.d.) flat Rayleigh fading channels is derived, and the average number of active relays (ANR) is also obtained. Numerical results are presented for performance illustrations and comparisons.