Investigation of the TCP simultaneous-send problem in 802.11 wireless local area networks

Sumathi Gopal, Sanjoy Paul, Dipankar Raychaudhuri

Research output: Contribution to journalConference articlepeer-review

13 Scopus citations


This paper investigates the TCP simultaneous-send problem which arises in infrastructure mode 802.11 wireless local area networks. In particular it has been observed that for file transfer traffic, 802.11 wireless nodes have a sustained supply of packets to send and hence experience a relatively high rate of MAC contention. For TCP, this results in competition among data and ACK packets for channel access which causes the simultaneous-send problem that deteriorates flow throughput. This simultaneous-send problem can be alleviated by skipping TCP ACKs. Detailed simulation results are presented to demonstrate the usefulness of ACK skipping in various network scenarios such as with MAC retries and multiple TCP flows. The largest improvement is seen for the case of a single TCP flow, and moderate gains are also achieved in cases with multiple streams. For the single TCP stream case with 1 ACK skip and no MAC retries, TCP throughput improves 30% for short-lived and 98% for long-lived TCP transmissions. The paper concludes with potential cross-layer solutions that potentially provide further improvements, including the use of the point coordination function (PCF) to reduce contention between multiple TCP streams and returning ACK packets.

Original languageEnglish (US)
Article numberWN31-3
Pages (from-to)3594-3598
Number of pages5
JournalIEEE International Conference on Communications
StatePublished - 2005
Event2005 IEEE International Conference on Communications, ICC 2005 - Seoul, Korea, Republic of
Duration: May 16 2005May 20 2005

All Science Journal Classification (ASJC) codes

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


  • 802.11 MAC
  • DCF
  • Delayed ACKs
  • Simultaneous-send
  • Skipped ACKs
  • TCP

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