  This paper analyzes the impact of statistical delay constraints on the
achievable rate of a two-hop wireless communication link, in which the
communication between a source and a destination is accomplished via a
buffer-aided relay node. It is assumed that there is no direct link between the
source and the destination, and the buffer-aided relay forwards the information
to the destination by employing the decode-and-forward scheme. Given
statistical delay constraints specified via maximum delay and delay violation
probability, the tradeoff between the statistical delay constraints imposed on
any two concatenated queues is identified. With this characterization, the
maximum constant arrival rates that can be supported by this two-hop link are
obtained by determining the effective capacity of such links as a function of
the statistical delay constraints, signal-to-noise ratios (SNR) at the source
and relay, and the fading distributions of the links. It is shown that
asymmetric statistical delay constraints at the buffers of the source and relay
node can improve the achievable rate. Overall, the impact of the statistical
delay tradeoff on the achievable throughput is provided.
