Delay-constrained multi-hop CSMA networks

The mean packet delay (MPD) of multi-hop wireless ad-hoc networks (WANET) has a major impact on the networks performance and quality of service. In this paper we analyze the performance of slotted carrier sense multiple access (CSMA) WANET under a MPD constraint. The MPD is determined by the mean number of hops between sources and destination pairs, the back-off probability and the outage probability. Using stochastic geometry analysis we perform a cross-layer optimization and present a simple expression for the area spectral efficiency (ASE) of the network as function of the MPD and the fading channel properties. Our main result is that the ASE grows linearly with the allowed MPD, D̄. The linear scaling coefficient can also be evaluated from the ASE expression: For example, with mean source-destination distance of L̄, a network that operates over Rayleigh fading channels with a path loss factor of 4 can achieve a maximum of 0.04D̄/L ² source-bits per second per hertz per squaremeter. The accuracy of the presented results is demonstrated by numerical simulations.