UBC Theses and Dissertations
Performance of collaborative spectrum sensing in a cognitive radio system Wang, Geng
Cognitive radio (CR) is a novel approach to improving the spectral efficiency of licensed radio frequency bands by opportunistically accessing unused portions of the band without introducing undue interference to a licensed user. To reliably identify unused portions in a dynamic environment, a collaborative spectrum sensing (CSS) approach is known to be advantageous. In this thesis, we investigate two issues related to CSS. A weighted energy fusion scheme for secondary users (SUs) with different sensing channel conditions is shown to achieve good sensing performance. To analyze the performance, a numerical approach utilizing a result in the probability density function of the weighted sum of noncentral chi-square random variables is used. Simulation results confirm the viability of the proposed numerical approach. The performance degradation resulting from imperfect reporting channels and energy measurement quantization in a CSS system is investigated. Simulation results show that the sensing performance can be significantly degraded. To reduce the performance degradation, unequal error protection of transmitted symbols through unequal power allocation (UPA) is employed. Simulation results are provided to quantify the gain provided by UPA.
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