Scheduling is a critical and challenging resource allocation mechanism formultihop wireless networks. It is well known that scheduling schemes that favorlinks with larger queue length can achieve high throughput performance.However, these queue-length-based schemes could potentially suffer from large(even infinite) packet delays due to the well-known last packet problem,whereby packets belonging to some flows may be excessively delayed due to lackof subsequent packet arrivals. Delay-based schemes have the potential toresolve this last packet problem by scheduling the link based on the delay thepacket has encountered. However, characterizing throughput-optimality of thesedelay-based schemes has largely been an open problem in multihop wirelessnetworks (except in limited cases where the traffic is single-hop.) In thispaper, we investigate delay-based scheduling schemes for multihop trafficscenarios with fixed routes. We develop a scheduling scheme based on a newdelay metric, and show that the proposed scheme achieves optimal throughputperformance. Further, we conduct simulations to support our analytical results,and show that the delay-based scheduler successfully removes excessive packetdelays, while it achieves the same throughput region as the queue-length-basedscheme.
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