Adjacent Channel Operation of Portable Unlicensed Devices inside DTV Service Contours

The operation of unlicensed devices (UDs) on underutilized licensed frequency bands can significantly enhance spectrum utilization. The FCC regulations on UD operation on vacant TV channels focus on controlling the interference to the primary system, which is a critical operational requirement for UDs. Personal/portable UDs are allowed adjacent channel operation inside the TV service contour. However, the FCC analysis of this operation is based on interference effects of a single UD, while the accumulative interference from multiple UDs is not considered. In this paper we extend the FCC analysis and develop a realistic model for interference from multiple UDs operating in Wireless Local Area Network (WLAN) clusters. We develop analytical expressions for the probability of outage of a primary user (PU) interfered by single and multiple clusters. The effect of channel variability due to shadowing is included. Results present the increase in PU outage probability with increased PU-TV station distance. For a single cluster operating in close vicinity of a PU, we analyse the effects of UD transmit power control and radiation pattern on PU performance.