Multi-rate opportunistic spectrum access in 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 temporal aspect of 802.11-based OSA scenario. Firstly, we investigate the secondary users (SU) multi-rate transmission and number of hops effects to the SU performance when exploiting primary users (PU) idle duration. Numerical analysis and simulation results show that, during limited PU idle duration, higher data rate transmission is essential even though it results in more hops but as the SU source traffic is getting busier, the balance between the data rate and number of hops is required. 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 difference that ARI aims to increase the SU data rate whenever it detects PU interruption failure. 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 56% compared with the original ARF scheme.