Span: An energy-efficient coordination algorithm for topology maintenance in ad hoc wireless networks

Benjie Chen, Kyle Jamieson, Hari Balakrishnan, Robert Morris

Research output: Contribution to journalArticlepeer-review

1015 Scopus citations


This paper presents Span, a power saving technique for multi-hop ad hoc wireless networks that reduces energy consumption without significantly diminishing the capacity or connectivity of the network. Span builds on the observation that when a region of a shared-channel wireless network has a sufficient density of nodes, only a small number of them need be on at any time to forward traffic for active connections. Span is a distributed, randomized algorithm where nodes make local decisions on whether to sleep, or to join a forwarding backbone as a coordinator. Each node bases its decision on an estimate of how many of its neighbors will benefit from it being awake, and the amount of energy available to it. We give a randomized algorithm where coordinators rotate with time, demonstrating how localized node decisions lead to a connected, capacity-preserving global topology. Improvement in system lifetime due to Span increases as the ratio of idle-to-sleep energy consumption increases. Our simulations show that with a practical energy model, system lifetime of an 802.11 network in power saving mode with Span is a factor of two better than without. Additionally, Span also improves communication latency and capacity.

Original languageEnglish (US)
Article number5091295
Pages (from-to)481-494
Number of pages14
JournalWireless Networks
Issue number5
StatePublished - 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Information Systems
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


  • Energy
  • Routing
  • Topology-formation
  • Wireless


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