An Improved Technique to Mitigate Interference between Adjacent Bands in Cognitive Radio System

Abstract

Cognitive Radio can access licensed spectrum as well as unlicensed spectrum, but while accessing licensed spectrum, radiation or signals of cognitive users interfere and disturb the licensed user signal in adjacent bands. Orthogonal Frequency Division Multiplexing (OFDM) is the enabling modulation technique for Cognitive Radios because of its flexible nature. The use of OFDM in Cognitive Radio will reduce intersymbol interference, but Out Of Band (OOB) leakage will still exists which effect the performance of licensed users operating in adjacent bands. Spectral mask based on precoding matrix is an efficient technique for reducing OOB radiation across Cognitive Radio user. In this paper, a new method is proposed for efficient utilization of spectral mask with simple equalization technique by considering the presence of licensed users, their position and controlling Out Of Band radiation without using notch frequencies. The simulation results show that proposed technique effectively reduces the Out Of Band radiation without reducing BER with minimal interference is offered to adjacent licensed users and reduction in computational complexity.