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

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.

[1]  Char-Dir Chung.  Spectrally Precoded OFDM with Cyclic Prefix , 2007, 2007 IEEE International Conference on Communications.

[2]  Geoffrey Ye Li,et al.  Multiuser Spectral Precoding for OFDM-Based Cognitive Radio Systems , 2013, IEEE Journal on Selected Areas in Communications.

[3]  Michael Schnell,et al.  Reduction of out-of-band radiation in OFDM systems by insertion of cancellation carriers , 2006, IEEE Communications Letters.

[4]  Char-Dir Chung,et al.  Spectral precoding for rectangularly pulsed OFDM , 2008, IEEE Transactions on Communications.

[5]  Chahe Nerguizian,et al.  Interference Cancellation Technique for MIMO MB-OFDM UWB Cognitive Radio , 2010, 2010 6th International Conference on Wireless and Mobile Communications.

[6]  Geoffrey Ye Li,et al.  Low-complexity spectrum shaping for OFDM-based cognitive radios , 2011, 2011 IEEE Wireless Communications and Networking Conference.

[7]  Negin Sokhandan,et al.  Out-of-band radiation reduction in OFDM-based cognitive radio systems , 2010, 2010 18th European Signal Processing Conference.

[8]  Hüseyin Arslan,et al.  Sidelobe suppression in OFDM-based spectrum sharing systems using adaptive symbol transition , 2008, IEEE Communications Letters.

[9]  F.K. Jondral,et al.  Mutual interference in OFDM-based spectrum pooling systems , 2004, 2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514).

[10]  H. Yamaguchi,et al.  Active interference cancellation technique for MB-OFDM cognitive radio , 2004, 34th European Microwave Conference, 2004..

[11]  Ming Chen,et al.  A precoding scheme for DFT-based OFDM to suppress sidelobes , 2009, IEEE Communications Letters.

[12]  Geoffrey Ye Li,et al.  Low-Complexity Spectrum Shaping for OFDM-Based Cognitive Radio Systems , 2012, IEEE Signal Processing Letters.

[13]  S Srikanth,et al.  A low complexity active interference cancellation method for OFDM based cognitive radios , 2010, 2010 National Conference On Communications (NCC).

[14]  P. Poongodi,et al.  Out of Band Radiation Control in OFDM Based Cognitive Radio Systems , 2016 .

[15]  Ravinder Kumar,et al.  Weighted Least Squares Based Spectral Precoder for OFDM Cognitive Radio , 2015, IEEE Wireless Communications Letters.