Distributed power control in ad hoc networks.
Neil Robert. Pate · ResearchSpace (University of KwaZulu-Natal) · 2003
Wireless communication is currently enjoying unprecedented popularity, and the present trend indicates an exponential growth rate.Both GSM , the traditional and now mature ceUular architecture, and UMTS, the internat ional 3G standard, are hampered by their need for the installation of expensive and unsightly base-stations, which have to be hard-wired to a central switching station.A new network concept, the ad hoc network, does away with the need for these basestations, and all local communication is done on a multi-hop, peer-to-peer basis.This does of course present.a significant engineering problem, as the removal of the centralized controllers (base stations) necessitates that all decisions related to, for example: routing, MAC and power control need to be done at the node.This dissertation discusses the concept of an ad hoc network, and specifically focuses on power control in a system with a CDMA air interface.Power control is a technique whereby the transmission power of a node is constantly adjusted., normally with the aim of minimizing the interference to other nodes while still maintaining a signal level that will achieve successful communication.Benefits of this include increased network capacity and throughput, usually coupled.with an increase in battery lifetime.Due to the lack of any centralized radio network controller, a fully distributed scheme needs to be developed.,whereby each node adjusts its power based only on information locally available.ii Due to the relative infancy of t he topic, very little literat ure exi5ts on power control in ad hoc networks using a distributed non-clustering ba.t;ed upproa.ch,and new methods are presented based on a scheme developed for cellular networks.In order to conserve the limited available bandwidth, a single-bit adaptive signalling scheme is implemented whereby a node will attempt to control the pov,•er of a subset of its surrounding nodes.Methods for determining which nodes belong in this subset are introduced, and the entire system simulated in a custom designed environment.Techniques for determining the controlling connectivity for a node are also presented , and their effect on the system perfor mance are investigated.Some of the metrics used to classify the performance of the network include system outage and convergence speed, as well as overall network connectivity.A model for an ad hoc network with predefined connectivity is presented , and an optimum transmit power vector derived..A standard mterference junction power control algorithm is deduced, and tested in sample networks.It was shown that when the system is feasible , in the absence of shadow fading and mobility, the proposed power control algorithm is able to exactly converge to the calculated ideal power vector, and when mobility and slow fading are introduced the algorithm is able to track the channel changes.