Sensing criteria of TV white space devices

Abstract

Soon heterogeneous TV white space (TVWS) systems will operate in underutilized TV bands. Potential interference between TVWS systems and Digital TV (DTV) broadcast is a major concern. This paper determines the conditions necessary for harmonious coexistence between TVWS and DTV system. There are three types of white space devices (WSDs), i.e. fixed WSD (FWSD), personal/portable WSD (PWSD), and sensing WSD (SWSD). In this paper, we focus on the third type, SWSD. The operations of FWSD and PWSD are governed by a geo-location database (GDB) server, SWSD is not. Instead, SWSD relies only on sensing result to determine an incumbent's presence. Sensing accuracy is critical. This paper investigates the sensing criteria of SWSD. We first describe the process of sensing in an energy detector, one of the simplest forms of spectrum sensor. This is followed by the analysis of its sensing performance. Sensing accuracy is represented by the probability of detection. Sensing inaccuracy is represented by the probabilities of miss detection and false alarm. The sensing requirement is expressed in terms of (i) the smallest detectable signal power (P Ri ), and (ii) the minimum number of energy samples (N) to be collected. This work evaluates the requirements for these two parameters in three types of DTV services, i.e. the Integrated Services Digital Broadcasting — Terrestrial (ISDB-T), Advanced Television Systems Committee (ATSC), and Digital Video Broadcasting — Terrestrial (DVB-T). We make contribution in identifying the levels of sensitivity required for SWSD operations within the ISDB-T, ATSC, and DVB-T service areas. In a typical scenario, we find the minimum requirements to be P ri = −105 dBm and N = 1100.