Performance Evaluation of Real-Time Transport with Link-Layer Retransmissions in Wired/Wireless Networks

Real-time transport over wired/wireless networks is challenging, since wireless links exhibit distinct characteristics, such as limited bandwidth and high error rates, due to fading or interference. We focus on the efficiency of mechanisms that bind operationally wired and wireless links. In this context, local error control is attractive, due to the remarkable feasibility of wireless link protocols in terms of wide range deployment. We investigate whether local retransmissions enable TCP to efficiently utilize wireless resources under the constraint of bounded end-to-end delay. Based on an analytical approach, as well as extensive simulations, we show that local recovery prevents wasteful end-to-end retransmissions and allows the transport protocol to utilize a higher fraction of the available bandwidth. However, we uncover undesirable effects of local error control which degrade the performance of real-time delivery in several occasions. Furthermore, we investigate whether local error control compares favorably with selected transport-layer mechanisms.