Research On Blind Recognition Of LTE And Wi-Fi Signals In Heterogeneous Congintive Network

With the rapid development of wireless communication technology and the increasing popularity of intelligent terminals,wireless communication networks have evolved into heterogeneous networks with different standards,access methods and coverage.In order to reduce spectrum pressure in the licensed band and increase network capacity,LTE-U network rapidly develops and forms a typical heterogeneous network with Wi-Fi that also operates in the unlicensed band of 5GHz.At the same time,in order to improve the spectrum utilization,spectrum sharing in cognitive radio has been applied to heterogeneous networks.In the absence of any prior information,the cognitive user works in the same frequency band as the primary user at the same time through overlay spectrum sharing.In order to reduce the interference to the primary user communication,the cognitive user needs to adjust its own operating parameters according to the results provided by the blind recognition of the signal,and the operating parameters mainly include power,modulation and carrier frequency.Therefore,the study of the blind recognition of LTE and Wi-Fi signals is of great significance in LTE-U and Wi-Fi heterogeneous cognitive networks.The task of this paper is from the national major projects for science:"polarization resource sensing and utilization in Dense and heterogeneous wireless environment(61571062)".Aiming at the problem of blind recognition of LTE and Wi-Fi signals in 5GHz unlicensed band,this paper takes the signal processing technology as the theoretical basis and utilizes the characteristic that the high-order spectrum of LTE and Wi-Fi signals is different,then blind recognition algorithm of LTE and Wi-Fi single and the blind recognition algotithm of LTE and Wi-Fi aliasing signal are studied to solve the problem of the blind recognition of LTE and Wi-Fi signal in the heterogeneous cognitive network.And it will provide the reliable qnd adjustable operating parameters for the cognitive users which want to share the 5 GHz unlicensed bands with LTE-U users and Wi-Fi users by the way of spectrum underlay.At the same time,based on the research of signal blind recognition technology,the research content of this paper will provide theoretical support and solution for the blind recognition of signal problem in the increasingly complex and highly dynamic wireless environment,so as to achieve the purpose that is initiative and rapid blind recognition of signal.The main contents of this paper are as follows:(1)This paper analyzes and summarizes the current research status of blind recognition of signal in heterogeneous cognitive networks,including the research background and significance,the key technologies and the main challenges.In this paper,it is pointed out that,the extraction of effective characteristic parameters of LTE and Wi-Fi signals,the interference of additive white Gaussian noise and the blind source separation of signals are the key factors that affect the blind recognition of signal in the heterogeneous cognitive network.(2)For the situation that LTE and Wi-Fi signals use OFDM modulation technology,it leads to that LTE and Wi-Fi have a strong similarity in the signal structure and characteristics.According to 3GPP/LTE and 802.11/Wi-Fi standards,this paper proposes the blind recognition algotithm of LTE and Wi-Fi signal based on the estimation of parameter is proposed when the signal sensed by cognitive user is single.Without knowing any prior information,the number of FFT,the oversampling rate and the effective subcarrier parameters is estimated firstly,and then LTE and Wi-Fi is recognition based on the different of the effective subcarrier number.Finally,the theoretical analysis and simulation results show that the performance of the blind recognition algorithm of LTE and Wi-Fi signal based on the estimation of the characteristic parameters is improved by about 5dB compared with the blind recognition algorithm of OFDM signal based on the high order statistics.(3)In LTE-U and Wi-Fi heterogeneous cognitive networks,the signals are sensed by cognitive users are not only the LTE and Wi-Fi single signals,but also the the LTE and Wi-Fi aliasing signals.A blind recognition algorithm of LTE and Wi-Fi aliasing signal based on blind source separation is proposed.In the proposed algorithm,the joint diagonalization algorithm is improved according to the high-order spectral characteristics firstly,and then the sepatated signal is recognized according to the characteristic parameters of the signal.Finally,theoretical analysis and simulation verify that the performance of the proposed algorithm is improved by about 4dB compared with the blind recognition algorithm of the LTE and Wi-Fi aliasing signal based on the traditional joint diagonalization method.In this paper,the blind recognition technology of LTE and Wi-Fi signals in heterogeneous cognitive networks is studied.The problem that the performance of the blind recognition of signals is influenced by the Gaussian white noise is solved by using the high order spectrum technique of signal.And the study of this paper provides a new way to the blind recognition of signal.