Blind SNR Estimation of Time-Frequency Overlapped OFDM Signals for Underlay Cognitive Radio Networks
LIU Ming-qian1,2,3, GUO Fei1, LI Bing-bing1, CHEN Qian2, WU Yun3
1. State Key Laboratory of Integrated Service Networks, Xidian University, Xi'an, Shaanxi 710071, China;
2. School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China;
3. Xuzhou LEO Medical Equipments Co., Ltd., Xuzhou, Jiangsu 221116, China
摘要 针对underlay认知无线电中时频重叠正交频分复用（Orthogonal Frequency Division Multiplexing，OFDM）信号的信噪比（Signal to Noise Ratio，SNR）难以估计的问题，提出了一种基于循环自相关特性的时频重叠OFDM信噪比盲估计方法.该方法提取接收信号的循环自相关函数截面中的离散谱线估计出分量信号的总功率，并结合时延和循环频率均为零时的离散谱线估计出时频重叠OFDM信号的信噪比.仿真结果表明，在无需先验信息的情况下，当SNR大于-7dB时，所提方法估计的均方误差小于0.1，并且对分量信号的功率比和频谱重叠率具有稳健性.
Abstract：In this paper,we propose one cyclic autocorrelation function (CAF) based method to implement the blind signal-to-noise (SNR) estimation over the underlay cognitive radio networks.The orthogonal frequency division multiplexing (OFDM) is adopted here.This SNR estimator utilizes the discrete spectrum of the CAF for the received signals,whose time delay and cyclic frequency are zero.Numerical results show that the proposed method is robust to the power ratio and spectral overlapping of the composite signal without prior information.Moreover,when the SNR is greater than -7dB,the mean square error (MSE) for the SNR estimation is less than 0.1.
[1] Zhao G D,Shi W Y,Li L Y.Passive primary receiver detection for underlay spectrum sharing in cognitive radio[J].IEEE Signal Processing Letters,2014,21(5):564-568.
[2] Kryszkiewicz P,Bogucka H.Low complex,narrow band-interference robust synchronization for NC-OFDM cognitive radio[J].IEEE Transactions on Communications,2016,64(9):3644-3654.
[3] Sharma M,Sahoo A,Nayak K D.Channel modeling based on interference temperature in underlay cognitive wireless networks[A].2008 IEEE International Symposium on Wireless Communication Systems[C].Reykjavik:IEEE,2008.224-228.
[4] Wang J H,Li B B,Liu M-Q,et al.SNR estimation of time-frequency overlapped signals for underlay cognitive radio[J].IEEE Communications Letters,2015,19(11):1925-1928.
[5] Baumgartner S,Hirtz G,Baumgartner A.A modified maximum likelihood method for SNR estimation in OFDM based systems[A].2014 IEEE International Conference on Consumer Electronics[C].Shenzhen:IEEE,2014.155-158.
[6] Tang N J,Li B B,Liu M Q.A modified blind OFDM systems parameters estimation method[A].2010 IEEE 12th International Conference on Communication Technology[C].Nanjing:IEEE,2010.1279-1282.
[7] Socheleau F X,Aïssa-El-Bey A,Houcke S.Non data-aided SNR estimation of OFDM signals[J].IEEE Communications Letters,2008,12(11):813-815.
[8] Xu X,Jing Y,Yu X.Subspace-based noise variance and SNR estimation for OFDM systems[mobile radio applications] [A].2005 IEEE Wireless Communications and Networking Conference[C].Ernest N.Morial:IEEE,2005.1:23-26.
[9] Li D,Ellinger J,Liu Z,et al.Mixed signal detection and symbol rate estimation based on spectral coherent features[A].2015 IEEE Military Communications Conference,MILCOM[C].Tampa:IEEE,2015.263-268.
2018, Vol. 46 
