Optimal Energy Allocation, Relay Selection and Ordering in Orthogonal Relay Networks

We consider the orthogonal multiple relay channel at the low SNR regime. The source transmits to the destination and all the possible relays in one channel and the relays transmit in different and orthogonal channels making use of the transmission received from the source and, in the more general case, also the other relay transmissions. This cooperative strategy achieves diversity gains at a high cost in bandwidth efficiency, due to the orthogonality of the transmissions. However, it has the desired benefit of allowing all the nodes in the network to behave as in a point to point channel. Based on the max-flow min-cut upper bound for relay networks, we explore the capacity limits of this kind of communication, obtaining the energy allocation, relay selection and ordering, when full channel state information (CSI) is available at every network node.