On the achievable throughput of buffer-aided diamond relay systems under delay constraints

In this paper, the achievable rate of buffer-aided diamond relay systems under delay constraints is studied. The effective capacity, characterizing the maximum constant arrival rate to the source while satisfying the end-to-end delay constraints, is obtained for fixed decode-and-forward (DF) relaying schemes and selective relaying protocols. A selection relaying policy that maximizes the delay exponent at the source is proposed, which is shown to be independent of delay constraints and select the relay with better channel conditions for reception. Through numerical results, it is demonstrated that the selection relaying strategy achieves superior performance than the fixed relaying schemes under a variety of delay constraints.