Outage Analysis of Multiple-Antenna Cognitive Radios in TV White Space

In this paper, we analyze the outage performance of coded orthogonal frequency division multiplexing (OFDM) systems when operating as a cognitive radio in TV white space. TV white space refers to unused television channels that are now open for unlicensed operation with some constraints. A key aspect of such systems is that both the available bandwidth and band location are variable. We have considered scenarios where the number of unused (hence available) TV bands is small. Such channels fall under the category of block-fading channels. We have also considered scenarios where multiple antennas are employed at the receiver. Previous work on performance analysis of multiple receive-antenna systems have focussed on scenarios where full space-frequency diversity is achieved. In this paper, we consider scenarios where full space diversity is achieved, but full frequency diversity is not achieved. Further, existing analysis techniques in the literature only predict average performance, whereas, outage performance may be more relevant in such systems. We derive tight approximations and bounds to the average and outage performance of such systems in this paper. We also present simulation results supporting the analysis.