Making retransmission delays in wireless links friendlier to TCP

Heterogeneous communication networks with their variety of application demands, uncertain time-varying traffic load, and mixture of wired and wireless links pose several challenging problem in modeling and control. In this paper we focus on the packet delay, which is an important variable for efficient end-to-end congestion control. In particular, we study the delay effects of radio links which use power control and link-layer retransmissions. Link-layer retransmissions induce delays which do not conform to the assumptions on which the transport protocol is based. This causes undesired TCP control actions which reduce throughput. A link-layer solution based on adding carefully selected delays to certain packets is proposed to counteract this problem. All information needed for this is available locally at the link.