TCP over multihop 802.11 networks: issues and performance enhancement

  • Authors:

  • Kitae Nahm;Ahmed Helmy;C.-C. Jay Kuo

  • Affiliations:

  • University of Southern California, Los Angeles, CA;University of Southern California, Los Angeles, CA;University of Southern California, Los Angeles, CA

  • Venue:
  • Proceedings of the 6th ACM international symposium on Mobile ad hoc networking and computing
  • Year:
  • 2005

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Abstract

Analyzing TCP operation over 802.11 multihop ad hoc networks involves a cross-layer study. In this work, we investigate the effect of congestion and MAC contention on the interaction between TCP and on-demand ad hoc routing protocol in the 802.11 ad hoc networks. Our study reveals several problems stemming from lack of coordination and sharing in such networks. It is observed that TCP induces the over-reaction of routing protocol and hurts the quality of end-to-end connection. So, one of the critical sources of lowering TCP throughput lies in the TCP window mechanism itself. To fix this problem, we propose a fractional window increment (FeW) scheme for TCP to prevent the over-reaction of the on-demand routing protocol by limiting TCP's aggressiveness. The proposed scheme is applicable to a wide range of transport protocols using the basic TCP mechanism, and the protocol behavior is analytically tractable. Our simulation results demonstrate that the proposed scheme can dramatically improve TCP performance and network stability in a variety of 802.11 multihop networks. For example, in some chain-like topologies, the proposed scheme outperforms basic TCP by over 90%, and recent related variants of TCP (ADTCP, LRED) by over 70%.