Page 2 Lecture Notes in Computer Science 2865 Edited by G. Goos ...

On the Interaction of Bandwidth Constraintsand Energy Efficiency in All-Wireless NetworksTommy Chu and Ioanis NikolaidisComputing Science DepartmentUniversity of AlbertaEdmonton, Alberta T6G 2E8, Canada{tommy,yannis}@cs.ualberta.caAbstract. The minimization of expended energy for unicast and broadcastcommunication between nodes in a wireless network has been studiedmostly as a path optimization problem without particular regard forthe traffic load demands. In this paper, we consider the call admissionproblem whereby given a traffic load (described as source-destinationrate demands) the required expended energy is minimized. In addition,we explicitly model bandwidth capacity constraints. The capacity constraintsreflect the fact that, from the perspective of a single node, trafficincludes data that the nodes originate and forward, as well as trafficthey receive and is of no interest to them. This last class of traffic isunavoidable due to the transmission radius of nearby stations. Underthe assumption that the MAC protocol behaves in an ideal fashion, weconsider two centralized algorithms that attempt to admit the given loadand we remark on their relative performance, especially with respect totheir energy consumption and blocking (connection rejection) rate.1 IntroductionApart from eliminating the need for a pre-existing infrastructure, a serious motivationbehind the deployment of wireless networks is the ability to establishconnectivity among, hopefully, unrestricted number of wireless nodes. Naturally,the extent to which this is doable has to do with the volume of carried trafficand the extent to which the radio spectrum is wisely reused among all participatingnodes. While a sufficiently intense traffic load can render any networkinadequate, the idea of proper reuse of the radio spectrum in light of competingnodes is not at all solved. In fact, there have been studies, such as the one in [1]suggesting that wireless ad hoc networks are, in principle, not scalable. That is,the foreseen benefit of spatial reuse of the radio spectrum produces diminishingreturns. The rate at which bandwidth reuse increases with increasing numberof nodes cannot catch up with the increasing load demands that the additionalnodes place on the network.The broadcast wireless advantage, furthermore in [2], illustrates the propertyof manipulate the transmission range. Increasing the transmission powercan reach more neighbors while it decreases the spatial reuse and increase theS. Pierre, M. Barbeau, and E. Kranakis (Eds.): ADHOC-NOW 2003, LNCS 2865, pp. 211–222, 2003.c○ Springer-Verlag Berlin Heidelberg 2003