Energy-efficient techniques allowing intra-link errors for block-fading multiple access relaying

Two energy and computationally efficient strategies are proposed for Multiple Access Relay Channel (MARC), where all links are suffering from block fading. By exploiting the error probabilities of the intra links, defined as the links between sources and relay, relay can still utilize the received frames, even though they may contain errors, and forward them rather than discard them. This makes efficient utilization of the information of those erroneous frames and thereby reduces the frame error rate (FER). Moreover, by applying differential encoding at sources following the recursive convolutional encoding, differential detection can be used at relay for recovering the received signals from the sources; with the use of differential detection, signals can be recovered without requiring heavy computational burden for channel estimation, and hence, as a whole the necessity of the use of very powerful limit-achieving codes can also be avoided. This leads to energy efficient relay strategies.