Frequency-Domain Coexistence Beacon for the Coexistence of White Space Applications

For the protection of incumbent users such as digital television (DTV), white space applications running on locally unused TV spectrum should be able to detect incumbent users at a low signal-to-noise ratio (SNR). Recent studies show that at a low SNR under high noise uncertainty, pilot detection performs better than other spectrum sensing methods such as energy detection and feature detection. The motivation of this paper is to adopt a DTV pilot detection scheme to detect white space applications. We propose assigning a frequency-domain coexistence beacon (FCB) at the same location of the DTV pilot as the pilot of white space applications. Over the FCB, every white space application transmits its coexistence beacon frames, and other white space applications detect the frames using the DTV detector just as it does DTV signals. The narrow bandwidth of the FCB contributes to better SNR than that of energy detection. The analysis of the proposed method shows that the increase in the SNR contributes to improving the coexistence of white space applications by increasing the average probability of detection. Although the reduced bandwidth to transmit user traffic causes degradation in the data rate, the proposed method can achieve higher utilization of total white space channels with less interference and more accommodation of newly-joining white space applications. In addition, the proposed method enables us to simply adopt the DTV pilot detector for detecting white space applications, allowing implementation of the proposed method at a low cost with less hardware complexity.