A.L. Gelgor - Ph. D. (Eng.), Associate Professor, St. Petersburg State Polytechnical University. E-mail: a_gelgor@mail.ru
I.I. Pavlenko - Post-graduate Student, St. Petersburg State Polytechnical University. E-mail: ipavlenko.mail@gmail.com
A.I. Gorlov -Assistant, Post-graduate Student, St. Petersburg State Polytechnical University. E-mail: anton.gorlov@yandex.ru
G.A. Fokin - Ph. D. (Eng.), Associate Professor, Bonch-Bruevich Saint - Petersburg State University of Telecommunications. E-mail: grihafokin@gmail.com
E.A. Popov - Ph. D. (Eng.), Associate Professor, St. Petersburg State Polytechnical University. E-mail: eugapop@gmail.com
V.A. Lavrukhin - Head of Research and Educational Center «Wireless Network Infotelecommunication», Bonch-Bruevich Saint - Petersburg State University of Telecommunications. E-mail: lavrukhin@sut.ru
M.A. Sivers - Dr. Sc. (Eng.), Professor, Bonch-Bruevich Saint - Petersburg State University of Telecommunications. E-mail: m.sivers@mail.ru

This article discusses the algorithm of initial synchronization with LTE base stations (BS). The algorithm consists of two steps. The first step is detection and differentiation of primary synchronization signals (PSS). The second step is differentiation of secondary synchronization signals (SSS). At the first step the number of detected PSS determines the first part of BS physical identifier value. The position of the detected PSS defines primary time synchronization. An important feature is possibility to separate several BS signals in the analyzed record. Thus, to provide PSS search algorithm termination the threshold value must be defined in algorithm. As implementation of the PSS search algorithm it is proposed to compute a set of three PSS normalized correlation functions (CF). Normalization allows defining the threshold value regardless of the analyzed signal level. In order to study the properties of the proposed PSS search algorithm and calculate the threshold value, PSS correlation properties and false alarm probability curves were obtained. It was shown that, firstly, the price for using decimated 16 times signal (i.e. recorded with a sampling frequency of 1.92 MHz) in PSS search algorithm is small energy losses of about 0.5 dB. Secondly, the proposed algorithm does not require additional frequency synchronization. Thirdly, the choice of the threshold value mainly influenced by PSS correlation properties. In other words, chosen because of PSS correlation properties threshold value provides false alarm probability much smaller than often values of 10−4. To SSS differentiation is proposed to compute SSS unnormalized CF. Normalization is not required since the position of SSS known in advance. Number of detected SSS defines the frame time synchronization and the second part of BS physical identifier value. Studies of the SSS correlation properties showed that, as in the case of PSS searching, decimated 16 times signal can be considered and additional frequency synchronization is not required. The proposed algorithm of initial synchronization with LTE BSs was tested on real signals. Analysis of the results showed that due to the different BS signals interference and multipath channel, it is necessary to use modified CF obtained by accumulation the initial CF on several periods.