Transmission strategies and resource allocation for fading broadcast relay channels

In this paper the broadcast relay channel, where the source communicates with multiple destinations with the help of a single relay is studied. Five different transmission protocols, direct transmission, multihop (MH), multihop with link combination (MHLC), path selection (PS) and path selection with link combination (PSLC) are investigated. In MH and MHLC, the relay decodes the source message and assists both destinations. In PS and PSLC, the relay can perform partial decoding and has the option to help only one of the destinations. Under long-term power constraint, power allocation for delay-limited transmission is performed to minimize common outage probability and individual outage probability region. For comparison, lower bounds on both common and individual outage probabilities are found. Numerical results suggest that path selection significantly lowers outage probabilities, while enforcing the relay to help both destinations simultaneously is limiting the system performance.