CSMA/CN: Carrier sense multiple access with collision notification

Souvik Sen, Romit Roy Choudhury, Srihari Nelakuditi

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


A wireless transmitter learns of a packet loss, infers collision, only after completing the entire transmission. If the transmitter could detect the collision early (such as with CSMA/CD in wired networks), it could immediately abort its transmission, freeing the channel for useful communication. There are two main hurdles to realize CSMA/CD in wireless networks. First, a wireless transmitter cannot simultaneously transmit and listen for a collision. Second, any channel activity around the transmitter may not be an indicator of collision at the receiver. This paper attempts to approximate CSMA/CD in wireless networks with a scheme called CSMA/CN (collision notification). Under CSMA/CN, the receiver uses PHY layer information to detect a collision and immediately notifies the transmitter. The collision notification consists of a unique signature, sent on the same channel as the data. The transmitter employs a listener antenna and performs signature correlation to discern this notification. Once discerned, the transmitter immediately aborts transmission. We show that the notification signature can be reliably detected at the listener antenna, even in the presence of a strong self- interference from the transmit antenna. A prototype testbed of 10 USRP/GNURadios demonstrates the feasibility and effectiveness of CSMA/CN.

Original languageEnglish (US)
Title of host publicationMobiCom'10 and MobiHoc'10 - Proceedings of the 16th Annual International Conference on Mobile Computing and Networking and 11th ACM International Symposium on Mobile Ad Hoc Networking and Computing
PublisherAssociation for Computing Machinery
Number of pages12
ISBN (Print)9781450301817
StatePublished - 2010
Externally publishedYes
Event16th Annual Conference on Mobile Computing and Networking, MobiCom 2010 - Chicago, IL, United States
Duration: Sep 20 2010Sep 24 2010

Publication series

NameProceedings of the Annual International Conference on Mobile Computing and Networking, MOBICOM


Other16th Annual Conference on Mobile Computing and Networking, MobiCom 2010
Country/TerritoryUnited States
CityChicago, IL


  • Collision detection
  • Cross-layer
  • Wireless

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture
  • Computer Networks and Communications


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