The Time of Entering into Synchronism During Synchronization According to the Cyclic Prefix OFDM Symbols Formed by the Sum of Information and Multiphase Sequences

In this paper, studies have been conducted to improve the synchronization efficiency by the peaks of the cyclic autocorrelation function of the cyclic prefix (CP) OFDM symbols of the LTE technology frame sent by the base station to the mobile user at the first synchronization stage. Three options for filling the CP and an equal number of elements of the end of the symbols of the frame are considered: the basic variant, when the CP is formed by transferring modulated elements of pseudorandom sequences (PRS) from the end of the symbol; the CP is formed from multiphase CAZAC (Constant amplitude zero autocorrelation waveform) sequences with the end of the symbols filled with the same sequences in the case of transmission by the station of "empty" symbols in the central part of the frequency range of the frame; the CP is formed from the sum of modulated PRS and multiphase sequences with the end of the symbols filled with the same sum of sequences in the case when the station does not transmit "empty" symbols in the central part of the frequency range of the frame. On the receiving side, the information of the end of OFDM symbols is restored in the devices of mobile users to whom the resources of the central frequency range of the LTE DL frame are distributed. The Zadoff–Chu (ZC) and Frank (Fr) sequences were used as multiphase CAZAC sequences; the PRS modulation types are QPSK or 64QAM. This study was carried out by simulation modeling in MATLAB for the Rayleigh communication channel model with delay profiles for the dense urban development (ETU) variant and with the addition of additive white Gaussian noise (AWGN); options for choosing the signal ratio/ noise SNR=0dB, 10dB, 50dB. The criterion for evaluating the effectiveness of one or another variant of filling the CP OFDM symbols are the results of calculations of the mathematical expectation of the search time and entering into synchronism and its variance.