Wireless Ad Hoc and Sensor Networks

5Distributed Power Control of WirelessCellular and Peer-to-Peer NetworksIn many cases, data from ad hoc wireless and sensor networks are routedthrough a cellular infrastructure or a wired network such as an Internet.To meet the quality of service (QoS), one has to ensure performanceguarantees not only from the wireless network side but also from thewired network. In the previous chapter, admission-controller design wascovered for wired networks so as to meet a desired level of QoS. In thischapter, we treat QoS performance for wireless cellular networks viatransmitter power, active link protection, and admission-controllerdesigns. For wireless networks, besides throughput, packet loss, and endto-enddelay guarantee, energy efficiency is another QoS performancemetric. Energy efficiency, to a certain extent, can be attained by controllingtransmitter power, which is the central theme of this chapter.The huge commercial success of wireless communications along withthe emerging popularity of IP-based multimedia applications are themajor driving forces behind the next generation (3G/4G) evolutionwherein data, voice, and video are brought into wireless networks thatrequire diverse QoS. In such modern wireless networks, distributedpower control (DPC) of transmitters allows interfering communicationssharing the same channel to achieve the required QoS levels. Moreoverunlike in wired networks, the channel condition affects the network capacityand QoS; therefore, any power control scheme for wireless networks mustincorporate the time-varying nature of the channel.Available power control schemes (Bambos 1998, Bambos et al. 2000,Zander 1992, Grandhi 1994, Foschini and Miljanic 1993), are efficient incombating disturbances such as path loss and user interferences that areof small magnitude, whereas they are ineffective during the process ofrejecting channel uncertainty (additive white Gaussian vs. Rayleigh fadingchannels) and combating large disturbances because they render poorbit error rate (BER) although consuming excessive power. Assuring QoSrequires novel schemes that use accurate channel state information, toreject uncertainties (Rayleigh fading channels), to combat disturbances(path loss, interference), to route data and control packets while optimizingthe transmitter powers, and trading power and delay during deep177