Feasibility study of sensing TV whitespace with local quiet zone

Unused TV spectrum, namely TV whitespace, is nearly ready for utilization by unlicensed TV band device (TVBD) given they provide sufficient protection to licensed TV devices, also called incumbents. A combination of a geo-location database and sensing is required to determine channel availability information. Sensing only device is also potentially allowed. From sensing perspective, TVBD should be able to detect incumbent signal as low as -114 dBm. To detect such low level incumbent signal, it is expected that a TVBD will quiet neighboring TVBDs during incumbent detection. Several mechanisms have been discussed in the literature to coordinate sensing. Among others, message based common inband wireless signaling, called quiet signaling, has been proposed to establish local quiet zone within which every TVBD suspends transmission to enable incumbent detection. However, there is little study on sensing performance in the presence of interference and the minimum size of local quiet zone required for detecting the weakest incumbent signals. Moreover, the sensing performance in a heterogeneous environment is not clear. In this paper, we intend to answer these questions. We analyze the impact of the incumbent signal strength, the interference power level, the transmission power of quiet signaling, and the minimum SIR tolerable to detect incumbent. We present discussion of homogeneous networks as well as heterogeneous networks where low power personal/portable TVBDs and high power fixed TVBDs may coexist. Although we focus on the detection of ATSC signal only in this paper, the methodology developed in this paper could be also applied to the detection of other primary signals.