On TCP over wireless multi-hop networks

TCP performance over wireless networks has been researched extensively. However, most of the related studies are limited to the cases with only one wireless link. The behaviors of TCP in the multi-hop wireless networks still have not been well understood. We investigate the performance of TCP in a multi-hop wireless network. After extensively comparing of the throughput of those existing TCP algorithms (including Tahoe, Reno, Sack and Vegas) by simulation, we found most TCP algorithms (except Vegas) exhibit serious instability never reported before. This can degrade the TCP throughput performance up to 13-20%. More importantly, with IEEE 802.11 MAC layer, the simultaneous TCP traffic are shown suffering from unacceptable severe unfairness. The unfairness problems we demonstrated in this paper are much more serious than that reported in previous studies. In our experiment, one TCP connection might be completely shut down even if it starts much earlier than the competing TCP traffic.