Optimal transmission strategy for a secondary user in IEEE 802.11 based networks.

TDD/TDMA based secondary network with cognitive capability is considered here. Primary network is WiFi based where the secondary network operates. DCF protocol has been followed by the users of WiFi network. Exact operating mechanism of DCF protocol is complex. Given this complexity, it is difficult for a secondary user to fully exploit the spectrum hole unused by WiFi users. We propose a novel opportunistic channel access scheme for the overlay network. Based on some valid arguments, we have justified the optimal transmission strategy of secondary user. Analytical derivation has been given for both types of user when the later acts over the former. Through numerical results, we have justified that the proposed strategy achieves far better performance affecting the original users' performance slightly. [ABSTRACT FROM PUBLISHER]