Multi-rate transmission in 802.11-based OSA multi-hop ad hoc networks

Opportunistic spectrum access (OSA) is a suitable approach to increase spectrum efficiency for the current spectrum management. This paper considers the secondary user (SU) multi-rate multi-hop impact under the temporal dynamic aspect of OSA. Firstly, we investigate the SU multi-rate transmission and number of hops impact under the temporal dynamic aspect of OSA. The observed metrics include both SU and PU performance. Numerical analysis and simulation results show the existence of multi-rate and multi-hop diversity. To obtain the optimal performance, the balance between high enough transmission rate and few enough number of hops is essential. Secondly, according to the multi-rate multi-hop investigation, we propose a rate adaption scheme with PU activity consideration, called Auto Rate Increase (ARI). ARI is based on the Auto Rate Fallback (ARF) scheme with the aims to select the best transmission rate under limited PU idle duration. ARI also adopts ARF simplicity, hence, there is no need for any prior nor additional knowledge of the networks environment. Simulation results show, under tight OSA environment, ARI scheme can increase the SU performance up to 37% compared with the original ARF scheme.