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Relays can be classified into digital and analog relays. Analog relays amplify and-forward (AF) the received signal without any decoding while digital relays fully decode and forward (DF) a regenerated version of the received signal. Here we are using digital relays as it is the focus of most of the next generation wireless networks standards such as IEEE 802.16j/m  and LTE-Advanced. The single-user single-relay network depicted in Fig. 1. In the first time slot, the BS transmits the signal to the RS and the signal is overheard by the UT, because of the broadcast nature of the electromagnetic waves. The RS fully decodes the signal and forwards it to the UT in the next time slot. In conventional relaying, the UT decodes the signal from the RS only. In cooperative relaying, the UT properly performs diversity combining of the signals it receives from the BS and RS. Since these signals experience uncorrelated fading, combining achieves diversity and thus reduces the effect of fading significantly.