Radio Frequency Spectrum Sensing for Multimple Transmitter Using Cognitive Radio

Abstract

The radio frequency spectrum is a scarce natural resource and its efficient use is one of the utmost importance. With the exponential increase in the use of high-powered wireless devices, there is a demand to utilize the spectrum efficiently, intelligently and optimally. Cognitive Radio is an attractive concept and solution, capable of addressing this issue. The spectrum bands are usually licensed to certain services, such as mobile fixed broadcast, and satellite, to avoid harmful interference between different networks. This scarcity of spectrum is the issue that wireless communication technology has to deal with. Primary user is the licensed user of the spectrum. When primary user is idle or not using the spectrum, secondary user can utilize the spectrum. This sharing of spectrum can be enabled by cognitive radio (CR) technology. The heart of enabling this technology is spectrum sensing. Spectrum sensing involves detection of primary signal at very low SNR (in the range of -20 dB), under noise and interference uncertainty. This requirement makes spectrum sensing, a hard nut to crack. Another major issue in detection is hidden node problem wherein the node in vicinity of primary transmitter also indicates absence of the primary signal since it is hidden behind the large object