Joint Power Allocation and Strategy Selection for Half-Duplex Relay System

Decode and forward (DF) and compress and forward (CF) are two efficient cooperation strategies for relay networks. The combination of the DF and CF strategies is promising to improve the achievable rate of cooperative communication systems. To thoroughly aggregate the advantage of the DF and CF strategies, we put forward a joint power allocation and strategy selection (PASS) scheme for the half-duplex relay channel. The PASS scheme is shown to achieve a higher rate compared with a regular hybrid DF/CF scheme. The rate gain obtained in the static relay channel results from actively adjusting and optimizing the relay power, followed by selecting the better strategy between DF and CF. In particular, when the relay receives and transmits in sequential time slots, we characterize the positive rate improvement area of the PASS scheme analytically and give a near-optimal setting for approaching the best rate performance. The PASS scheme is extended to fading relay channels. We show that the rate increment obtained from the PASS scheme is further magnified by employing an advanced relay power allocation technique over channel states. The corresponding optimal power allocation is established based on the concavity of the rate achieved by the PASS scheme in static relay channel. Numerical results are presented to validate the analysis.