Effects of link-level queueing and truncated ARQ on TCP throughput in multi-rate wireless networks

摘要

A complete queueing model for radio link layer performance analysis is developed assuming adaptive modulation and coding (AMC) at the physical layer and truncated automatic repeat request (ARQ)-based error control at the link layer. From the analysis the queue length distribution and the average queueing delay can be calculated. The average queueing delay is then used to estimate TCP (Transmission Control Protocol) throughput performance using a fixed point approach. The analytical model enables us to choose signal-to-noise ratio (SNR) thresholds of the different transmission modes for AMC at the physical layer for different persistence levels of ARQ at the link layer so that the TCP throughput is maximized. We observe that channel correlation negatively impacts the TCP throughput performance. Also, throughput enhancement of TCP NewReno over TCP Reno is non-negligible only if no ARQ-based error recovery is employed at the link layer of the protocol stack.