Composite Hypothesis Testing for Cooperative Spectrum Sensing in Cognitive Radio

In this paper, we present a composite hypothesis testing approach for cooperative spectrum sensing. We derive the optimal likelihood ratio test (LRT) statistic based on the Neyman-Pearson (NP) criterion at the fusion center for both hard (one-bit) and quantized (multi-bit) local decisions. We show that the LRT statistic depends on the modulation type and second- and fourth- order statistics of the primary signal. However, such side information is not commonly available to the secondary network. Therefore, we propose to apply composite hypothesis testing methods, such as the Rao test, which do not require any prior knowledge about the primary signal, in a cooperative sensing scenario. We derive a modified Rao test statistic for decision making at the fusion center for both cases of hard and quantized local decisions. We also apply the locally most powerful (LMP) detector at the fusion center for weak primary signals and derive its corresponding test statistic. These methods are much simpler than the optimal NP-based method and do not require estimation of the primary signal statistics while having a very close performance to the optimal method.