A Review on Two Stage Spectrum Sensing for Cognitive Radio Networks

With the rapid development of wireless communication, the problem of bandwidth shortage has become more prominent. On the other hand, the studies made by FCC (Federal Communications Commission) showed that in the licensed spectrum band, most of the time large portion of the spectrum vacant and users only utilize their allocated resources partially. So, to solve this problem of spectrum under-utilization, FCC allowed unlicensed user i. e. secondary users to utilize the licensed band when it is not in use and named it as Cognitive Radio. In cognitive radio the most important part is to sense spectrum. In this paper we proposed a two-stage spectrum sensing scheme for cognitive radios where in the first stage energy detection is used and combination of maximum-minimum eigen (CMME) value based detection used in the second stage. The detection parameters in both the stages is used in such way so as to maximize Probability of detection on the given constraints on the probability of false alarm. Also advantages and disadvantages of detection techniques are analyzed and summarized. also research issues and challenges are given.