Efficient Two Stage Spectrum Sensing for Cognitive Radios

Abstract

The growth of wireless communication in recent years has resulted to spectrum scarcity and increase in the number mobile users. However, the major concern in wireless communication is spectrum scarcity on fixed spectrum. Technologies such as cognitive radios (CR) have emerged to address the issue of spectrum scarcity in wireless communication. The principle which CR is using to address spectrum scarcity is by utilizing opportunistic spectrum access method. In this method CR allows the secondary users (SU) to opportunistically utilize spectrum by sensing the absence or presence of the primary users (PU) on the spectrum that it will assign to the SU. Thus, before CR allows the SU to utilize the spectrum it must first carry out the process of spectrum sensing (SS). This process of SS can either be done by exerting single stage or two stage SS techniques. Nevertheless, this process is not an easy task, due to several factors such as noise, cochannel interferences and attenuation which have a negative effect on the accuracy, reliability and efficiency of CR. Thus, in this work literature review on single stage and two stage (dual stage) SS techniques was carried out to determine how the efficiency, accuracy and sensing time on SS can be improved.