The effective capacity of two-unicast network coding STBC under retransmission schemes.

Downlink multiuser network coding (NC) automatic repeat request (ARQ) systems can provide significant throughput improvements over basic ARQ systems. In this paper, we consider the case of two-unicast flows and analyze their performance in terms of the effective capacity (EC) under retransmission schemes. We extend the derived EC of NC-ARQ for asymmetric channels where users have different data rates. For NC-ARQ, two scenarios at the source are considered to handle the transmission. The EC expression for two-unicast flows using Alamouti space time block coding (STBC) is also derived. We also present a new scheme that combines both NC and STBC and, denoted by NC-STBC-ARQ. Our results show that the new NC-STBC-ARQ improves the EC over basic STBC in the low-to-moderate signal-to-noise ratio (SNR) regime. Besides, the new NC-STBC-ARQ improves the EC compared to basic NC-ARQ for a moderate-to-high SNR regime. [ABSTRACT FROM AUTHOR]