The Gateway Channel: Outage Analysis

The authors consider a relay that simultaneously assists multiple source-destination pairs that do not have a direct link, which they denote the gateway channel, and explore the sum capacity of this network in the presence of quasi-static fading. In the absence of transmitter-side Channel State Information (CSI), they study super-position as well as orthogonal channel access. In the presence of transmitter CSI, they consider opportunistic channel access with full CSI, as well as limited CSI via a 1- bit feedback (per user). In each case, the outage capacity and the diversity-multiplexing tradeoff are calculated. It is observed that orthogonal channel access is almost as good as superposition coding, and that opportunistic access provides significant gains.