Wireless multi-hop CSMA/CA with cross-optimised PHY/MAC

We investigate the impact of power control and choice of modulation index on the performance of a multi hop CSMA/CA system. We explicitly take into account the additional traffic generated due to multi-hop transmissions and the effect of frame error rates, the later being a function of the frame length, the modulation index, and the signal-to-noise ratio (SNR). An analytical model for the spectral throughput per user is presented with emphasis on the number of nodes dwelling in the area covered by a given transmission power and on the number of hops. Unlike other works, a closed form solution is derived for the spectral throughput performance of a multi hop CSMA/CA system as a function of the offered load, the nodes density, transmission power and frame error rate. This facilitates the PHY and MAC layers to be jointly optimised, e.g. the system designer may specify the optimum choice of modulation index for a given MAC configuration or, alternatively, the optimum persistency parameter for a given PHY.