Improving TCP performance over wireless networks at the link layer

We present the transport unaware link improvement protocol (TULIP), which dramatically improves the performance of TCP over lossy wireless links, without competing with or modifying the transport- or network-layer protocols. TULIP is tailored for the hall-duplex radio links available with todayʹs commercial radios and provides a MAC acceleralion icalure applicable lo collision-avoidance MAC protocols (e.g., IEEE 802.11) to improve throughput. TULIPʹS timers rely on a maximum propagation delay over the link, rather than performing a round-trip time estimate of the channel delay. The protocol does not require a base station and keeps no TCP slate. TULIP is exceptionally robust when bit error rates are high; it maintains high goodput, i.e., only those packets which arc in fact dropped on the wireless link are retransmitted and then only when necessary. The performance of TULIP is compared against the performance of the Snoop protocol (a TCP-aware approach) and TCP without link-level retransmission support. The results of simulation experiments using the actual code of the Snoop protocol show that TULIP achieves higher throughput, lower packet delay, and smaller delay variance.