Physical Layer based LTE and WiMax signal Auto-Detection using Correlation based Parameter Estimation Muhammad Salman Khan, Sana Siddiqui Department of Electronic Engineering, NED University of Engineering & Technology, Karachi Pakistan Abstract – In this paper, we propose a baseband, correlation based blind estimation method for the identification of LTE and WiMAX signals in the uplink communication scheme. LTE and WiMax standards are centerd around orthogonality using the FFT and IFFT techniques. The time parameter estimation based algorithms sequentially estimate the symbol duration and the cyclic prefix whereby useful timeslots can be calculated through these estimates. The proposed technique works over LTE and WiMax standard with a limited sample of data without any prior information like SNR level and symbol rate. The Matlab simulations display fast and accurate performance for both AWGN channel and Rayleigh fading channel. The proposed algorithm can also be used for identifying various radio access systems and hence a single terminal can be used for the reception of multiple air interfaces. Keywords: LTE, WiMax, Blind Estimation, ODFMA, SCFDMA, Parameter Estimation 1 Introduction Cognitive Radios or Software Defined Radios are the most viable solutions to handle spectrum scarcity problem which arises due to the ever increasing augmentation in number of users and applications that require very high data rates. These software defined reconfigurable radio terminals can recognize different wireless networks and are capable of estimating the basic parameters of various air interfaces. Orthogonal Frequency Division Multiple Access (OFDMA) is one of such promising techniques that enables high spectrum efficiency as well as robustness and is very effective for RF dispersive environments. OFDM is already employed as the modulation scheme for wireless communication systems like Wireless Local Area Network (WLAN) IEEE 802.11 and Wireless Metropolitan Area Network (WMAN) based on IEEE 802.16. Single Carrier - Frequency Division Multiple Access (SC-FDMA) is another derivative of OFDMA that utilizes single carrier modulation. It has an additional benefit of low peak-to-average power ratio (PAPR) compared to OFDMA. SC-FDMA is currently adopted as the uplink multiple access scheme for 3GPP LTE. Some of the most promising spectrum sensing algorithms exploits the cyclostationarity property of communication signals. Cyclostationarity based spectrum sensing algorithms have been proposed in various papers. These algorithms do not require any explicit assumptions on the data or noise distributions. [10] 2 Background The paper [1] exploits the cyclostationarity of OFDM signals and estimates the symbol duration by maximizing a sum of modulus squares of cyclic correlation estimates in the cyclic domain. In paper [2], under the assumption of low signal-to-noise ratio, the joint maximum-likelihood (ML) phase offset and Symbol Timing estimator for additive white Gaussian noise (AWGN) channel is proposed. The estimate depends on both the non-conjugate and the conjugate correlation function of the transmitted OFDM/OQAM signal and exploits the cyclostationarity of the OFDM/OQAM signal. Paper [3] discusses the blind time parameter estimation of OFDM signals in multipath fading channels based on correlation algorithm. Correlations of the trial source with alterable correlation length are calculated and a peak is acquired when the correlation length equals useful symbol duration. The site of correlation peak equals the length of useful symbol. Symbol duration is estimated by finding the distance between the peaks at the correlation and the guard time can be worked out. Paper [4]-[5] is also based on the blind time parameter estimation for OFDM signals using correlation and exploits the cyclostationarity property of these signals. Most systems are based on OFDM modulations but differ from their inter carrier spacing used in OFDM modulation. In Paper [6]-[8], efficient algorithms