Energy-efficient broadcasting in ad-hoc networks: combining MSTs with shortest-path trees

  • Authors:
  • Paolo Penna;Carmine Ventre

  • Affiliations:
  • Università di Salerno, Baronissi (SA), Italy;Università di Salerno, Baronissi (SA), Italy

  • Venue:
  • PE-WASUN '04 Proceedings of the 1st ACM international workshop on Performance evaluation of wireless ad hoc, sensor, and ubiquitous networks
  • Year:
  • 2004

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Abstract

We investigate the problem of constructing a multicast tree in ad-hoc networks. In particular, we address the issue of the power consumption, that is, the overall energy that the stations must spend to implement such a tree. We focus on two extreme cases of multicast: broadcast (one-to-all) and unicast (one-to-one). Minimum Spanning Trees (MSTs) and Shortest-Path Trees (SPTs) yield optimal solutions for broadcast and unicast, respectively. Unfortunately, they do not guarantee any optimality for the "counterpart", that is, MSTs are non-optimal for unicast, while SPTs are non-optimal for broadcast.In this work, we experimentally evaluate the performances of an algorithm combining MST solutions with SPT ones. Our approach is based on the construction of Light Approximate Shortest-path Trees (LASTs) of a given directed weighted graph, introduced by Khuller et al [1995]. LASTs approximate simultaneously the cost of the MST and the distances of the SPT rooted at a source node, thus yielding, also in the worst case, optimal solutions for both unicast and broadcast.Rather surprisingly, this "compromise" between MSTs and SPTs, has a very good performance w.r.t the broadcast tree obtained from a MST. Indeed, for randomly-generated instances, the broadcast tree obtained with LASTs is in some cases better (and never much worse) than the broadcast tree obtained from MSTs. This important fact shows that LASTs are not only interesting in theory, but they have practical relevant applications. Indeed, their use in our experiments also provides new insights on the approximation ratio of the MST broadcast algorithm for randomly-generated instances.