Wireless Ad Hoc and Sensor Networks

Distributed Power Control of Wireless Cellular and Peer-to-Peer Networks 179convergence of the power update scheme (Bambos et al. 2000, Wu 2000)and the process of admitting links are an issue in a highly dynamic wirelessenvironment as illustrated in this chapter. Therefore, it is demonstrated thatthe state space and optimal schemes (Jagannathan et al. 2002) can convergeand can admit significantly more links (Dontula and Jagannathan 2004)while guaranteeing that the links consume minimal power.In this chapter, a networking approach to the design of DPC schemesis discussed (Dontula and Jagannathan 2004), in which the issue of admissioncontrol is made central for the peer-to-peer scenario initially. Thestate space and an optimal power control schemes, which sustain the SIRof active links above a certain threshold referred to as active link-protection(ALP), are introduced when new links access the channel. Intuitively, thenew links gradually power up while the active ones are assured QoS witha protection margin. The DPC schemes can efficiently control the powerbeing used by the established links in a communication channel. Theseschemes can achieve the required SIR, which reflects a given level of QoS.Lower interference levels in the communication channel resulting fromthe use of this scheme can increase the channel efficiency, capacity, andreusability for the uplink scenario.It is proven that the DPC schemes converge and admit a greater numberof links when compared to the existing schemes (Bambos et al. 2000, Janttiand Kim 2000, Wu 2000). For the proposed schemes, it is analyticallyproven that a trade-off exists between convergence speed and powerconsumed by a mobile user. This trade-off is easily observed by using thefeedback gains. The power control scheme being highly distributive innature doesn’t require interlink communication, centralized computation,and reciprocity assumption as required in a centrally controlled wirelessenvironment. As the necessity of interlink communication is eliminated,network capacity increases and easy, controlled recovery from error eventsis possible. The DPC/ALP scheme can be used to work in a cellularnetwork environment. Instead of receiver–transmitter pairs as in the casewith peer-to-peer networks, users in a cell communicate with the basestation, which services the cell. To compare the DPC schemes discussedin the literature, users are assumed to request channel access at the sametime, at the beginning of the simulation. From the results, it is indicatedthat the proposed schemes provide lower outage probability, consumeless power, and converge in a reasonable amount of time.The DPC schemes have to be modified in the presence of fading channels.In fact, a novel channel estimator is introduced, which is embedded in theDPC (Jagannathan et al. 2006), so that the suitable power values can beselected in the presence of fading channels. Results indicate that the modifiedDPC with the embedded channel estimator provides a superior performance.First, the state-space-based controls design (SSCD) and optimal DPC schemesare presented; and subsequently, the modified DPC scheme is covered.