Compressing backoff in CSMA networks

Mahanth Gowda, Nirupam Roy, Romit Roy Choudhury, Srihari Nelakuditi

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


Randomized backoff is a well-established approach for avoiding collisions in CSMA networks. Today's backoff operation, such as in WiFi, attempts to create a total ordering among all the nodes contending for the channel. Total ordering requires assigning a unique backoff to each node, which is achieved by having nodes choose their back-offs from a large range, ultimately leading to channel wastage. This paper observes that total ordering can be achieved more efficiently. We propose 'hierarchical backoff' in which nodes pick random numbers from a smaller range, resulting in groups of nodes picking the same number (i.e., partial order). Now, the group of nodes that picks the smallest number is advanced to a second round, where they again perform the same operation. This results in more efficient backoff because the time for partially ordering all nodes plus totally ordering each small groups is actually less than the time needed to totally order all nodes. Realizing the above intuition requires addressing new protocol challenges in group signaling, the feasibility of which is demonstrated on a USRP/GNUradio prototype. Large scale simulations also show consistent throughput gains by incorporating the proposed backoff approach into two CSMA protocols - WiFi and oCSMA. We also show that the proposed approach can be complementary to and even outperform existing backoff optimization schemes.

Original languageEnglish (US)
Title of host publication2016 IEEE 24th International Conference on Network Protocols, ICNP 2016
PublisherIEEE Computer Society
ISBN (Electronic)9781509032815
StatePublished - Dec 14 2016
Event24th IEEE International Conference on Network Protocols, ICNP 2016 - Singapore, Singapore
Duration: Nov 8 2016Nov 11 2016

Publication series

NameProceedings - International Conference on Network Protocols, ICNP
ISSN (Print)1092-1648


Other24th IEEE International Conference on Network Protocols, ICNP 2016

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Software


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