  We consider multi-antenna cooperative spectrum sensing in cognitive radio
networks, when there may be multiple primary users. A noise-uncertainty-free
detector that is optimal in the low signal to noise ratio regime is analyzed in
such a scenario. Specifically, we derive the exact moments of the test
statistics involved, which lead to simple and accurate analytical formulae for
the false alarm probability and the decision threshold. Simulations are
provided to examine the accuracy of the derived results, and to compare with
other detectors in realistic sensing scenarios.
