Investigating interactions between ARQ mechanisms and TCP over wireless links
Francesco Vacirca, De Vendictis A, Andrea Baiocchi · 2004
Abstract: In this paper we investigate interactions between TCP and wireless ARQ mechanisms. The aim is to understand what is the best conguration of the wireless link protocol in order to guarantee TCP perfor-mance, seemingly a controversial issue. Interactions be-tween TCP and different link layer mechanisms are eval-uated by means of an analytic model, that reproduces a generic selective repeat ARQ protocol (widely used in the current wireless environments) and the TCP behavior in a wired-cum-wireless network scenario. A numerical inves-tigation is carried out in a specic case study (TCP over 3G radio access) by means of simulations collected with a very detailed UMTS-TDD simulator based on ns. Our main nding is that fully reliable ARQ protocols are the best choices from the TCP perspective; in fact, whereas a residual packet loss left over by not fully reliable ARQ pro-tocols may not degrade appreciably TCP throughput per-formance as long as it is a fraction of the overall end-to-end TCP packet loss, no apparent performance advantages (e.g. energy savings) come from limiting the number of retrans-mission attempts at the wireless link layer. 1