Cooperative spectrum sensing: From fundamental limits to practical designs

The first and foremost function in cognitive radio is spectrum sensing. To overcome the performance bottleneck created by fading and shadowing effects of the wireless channel, cooperation among sensing users is proposed as a promising solution. However, most designs of cooperative sensing strategies are developed in a rather ad hoc manner due to the lack of the fundamental knowledge on the cooperation gain. Hence, in this chapter, the cooperation gain in the context of cooperative spectrum sensing is rigorously quantified via diversity and error exponent analyses. The fundamental limits of the diversity and error exponent are derived as functions of key system parameters. After that, a couple of case studies are presented to illustrate how the concepts of diversity and error exponent can guide practical designs of cooperative spectrum sensing.