Upper Bound on Outage Capacity of 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. 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 an upper bound on the capacity when full channel state information (CSI) is available at every network node. This focus gives insight on the design of the transmitting strategy and define how feedback from relays and destination can be performed practically and optimally, giving ideas for higher layer protocols