Statistical bandwidth scavenging for prioritized device coexistence

Dynamic Spectrum Access in a Wireless LAN can enable a set of secondary users´ devices to access unused spectrum, or whitespace, which is found between the transmissions of a set of primary users´ devices. The primary design objective for an efficient secondary user access strategy is to be able to “scavenge” spatio-temporally fragmented bandwidth while limiting the amount of interference caused to the primary users. In this paper, we propose a secondary user access strategy which is based on measurement and modeling of the whitespace as perceived by the secondary users in a WLAN. A secondary user monitors and models its surrounding whitespace, and then accesses the available spectrum so that the effective secondary throughput is maximized while the resulting interference to the primary users is limited to a pre-defined bound. We first develop analytical expressions for the secondary throughput and primary interference, and then perform ns2 based simulation experiments to validate the effectiveness of the proposed access strategy, and evaluate its performance numerically using the developed expressions. The results show that the proposed access strategies are able to consistently scavenge between 90% and 96% of the available whitespace bandwidth, while keeping the primary users disruption less than 5%.