Wireless Ad Hoc and Sensor Networks

7Distributed Fair Scheduling in WirelessAd Hoc and Sensor NetworksIn the previous chapter, the distributed adaptive power control scheme(DAPC) or simply DPC and a medium access control (MAC) protocolwere introduced for ad hoc wireless and sensor networks. DAPC isutilized to meet energy efficiency besides other quality of service (QoS)performance parameters such as throughput, end-to-end delay, and lossor drop rate. In many wireless networking applications, there are additionalQoS performance metrics such as fairness that need to be met.Under such circumstances, the DPAC alone is not sufficient to meet thetarget QoS. Because bandwidth is one of the main constraints in wirelessad hoc networks, the key to guarantee QoS in this type of networkswould be efficient bandwidth management through which fairness isguaranteed.7.1 Fair Scheduling and Quality of ServiceFairness is a critical issue (Goyal et al. 1997) when accessing a sharedwireless channel. A fair scheduling scheme must then be employed in adhoc wireless networks and wireless sensor networks (WSNs) to provideproper flow of information. In the literature, many algorithms and protocolsregarding QoS metrics are found; however, they do not addresshardware constraints.The notion of fairness must be guaranteed among a set of contendingflows. Moreover, the proposed scheme should be computationally distributedin its nature. Thus, any distributed solution to WSN fair schedulingmust coordinate local interactions to achieve global performance.This should be achieved within the constraints imposed by the hardware.Therefore, any fair scheduling algorithm proposed for a multihop303