Dynamic multiple access efficiency of Aloha and UWB with and without detect and avoid

Both detect and avoid (DAA) and continuous transmission with no DAA (NDAA) are mechanism defined to allow an ultrawideband (UWB) terminal (UWBT) to coexist with other non UWB terminas (nUWBTs). This work studies the dynamic multiple access (DMAC) efficiency E of DAA and NDAA when the UWBT is coexisting with several nUWBTs that use Aloha as a medium access control (MAC). The E is studied in terms of the spectrum utilization factor F of the nUWBTs, and the signal-to-noise ratio (SNR) of both the nUWBTs and the UWBT. The nUWBTs and the UWBT share a wireless channel with fading effects due to multipath in which the nUWBTs experience non-correlated fading and the UWBT experiences correlated fading. We consider two scenarios: A DMAC scenario in which both nUWBTs and the UWBT coexist, and a pure MAC scenario in which only the nUWBT access the channel using Aloha. Results show that: 1) For low values of F, the increase in E in a DMAC scenario is by a factor of about 5 with respect to the E in a pure MAC scenario. However, as F gets larger we get a diminishing increase in E for DAA. 2) For low values of F, the E using DAA is about 80% the E using NDAA. Hence, the loss in E using DAA with respect to NDAA represents less than 1 dB for low values of F. 3) Furthermore, we found that for a pure MAC scenario E in AWGN is very close to the E in multipath, but for a DMAC scenario the E in AWGN is higher than the E in multipath.