Technical Approach

Most existing approaches to spectrum sensing are based on binary hypothesis testing where the goal is to determine if the observed frequency band is occupied or not or test if a certain signal is present or not in the observed frequency band. This problem is solved using well known tools such as energy detectors, matched filters, cyclostationary detectors, etc  [1]  [2]. In our application we deal with multiple packet based radio transmitters where each transmitter produces a signal with non-persistent excitation. Thus, each signal is characterized with its spectra and an on/off activity sequence in time. Our approach is to develop algorithms for estimation of spectral and temporal parameters for each of the signals present. In other words, we wish to localize the packet based signals in time and frequency. Thus, our approach is significantly different from the existing spectrum sensing methods.  

Results To Date & Future Work Plan

Since each transmitted signal consists of on and off transmission periods the received signal at each sensing node consists of a certain number of statistically homogeneous segments. First important task in the analysis of the received signals is to localize statistically homogeneous segments in time. We have developed a segmentation algorithm for this problem [3]. Once the statistically homogeneous segments have been localized in time they can be analyzed using various statistical methods. We propose one such method based on fourth order spectrum [4]. Our ongoing work is developing extensions of these algorithms for multiple sensors.