Listen (on the frequency domain) before you talk

Souvik Sen, Romit Roy Choudhury, Srihari Nelakuditi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Conventional WiFi networks perform channel contention in time domain. This is known to be wasteful because the channel is forced to remain idle, while all contending nodes are backing off for multiple time slots. This paper proposes to break away from convention and recreate the backing off operation in the frequency domain. Our basic idea is to pretend that OFDM subcarriers are integer numbers, and thereby, view today's random backoff process as equivalent to transmitting on a randomly chosen subcarrier. By employing a second antenna to listen to all the subcarriers, each node can determine whether its chosen integer (or subcarrier) is the smallest among all others. In fact, each node can even determine the rank of its chosen integer, enabling the feasibility of a TDMA-like schedule from every round of contention. We develop these ideas into a Time to Frequency (T2F) protocol and prototype it on a small testbed of 8 USRPs. Experiments confirm its feasibility, along with promising throughput gains of more than 35% at high bit rates. A fuller design and thorough evaluation of T2F is a topic of ongoing work.

Original languageEnglish (US)
Title of host publicationProceedings of the 9th ACM Workshop on Hot Topics in Networks, Hotnets-9
StatePublished - Dec 1 2010
Externally publishedYes
Event9th ACM SIGCOMM Workshop on Hot Topics in Networks, HotNets-9 - Monterey, CA, United States
Duration: Oct 20 2010Oct 21 2010

Publication series

NameProceedings of the 9th ACM Workshop on Hot Topics in Networks, Hotnets-9


Other9th ACM SIGCOMM Workshop on Hot Topics in Networks, HotNets-9
Country/TerritoryUnited States
CityMonterey, CA


  • C.2.1 [Network Architecture and Design]: Wireless communication
  • Design
  • Experimentation
  • Performance

ASJC Scopus subject areas

  • Computer Networks and Communications


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