Calculation method in time-frequency synchronization process

Abstract

The invention discloses a calculation method in a time-frequency synchronization process. The method comprises the following steps of: performing down-sampling processing on received sampling data, performing autocorrelation operation at different orthogonal frequency division multiple access symbol intervals in a time domain, performing wireless inter-frame combination and combination of different symbol intervals on an obtained autocorrelation value, judging whether an NPSS exists or not according to the signal-to-noise ratio and the autocorrelation value after merging processing, preliminarily calculating time offset and fractional frequency offset according to the autocorrelation value after merging processing, and judging whether coarse cross-correlation calculation and fine cross-correlation calculation are carried out or not according to a judgment result. Through the method, the operand of calculating the time offset and the frequency offset in the synchronization process can be reduced, and meanwhile, the correct judgment rate for judging whether the NPSS exists or not is improved.

Description

technical field [0001] The invention relates to the field of synchronous signal processing, in particular to a calculation method in the process of time-frequency synchronization. Background technique [0002] The first step for starting up the UE of the narrowband Internet of Things NB-IoT (Narrow Band Internet of Things) system is to perform frequency point synchronization on the frequency band it supports, find the center frequency point where NB-IoT cells may reside, and then pass a large number of The autocorrelation and cross-correlation operation of the cell is used to obtain the time and frequency synchronization of the cell. In this synchronization process, a large number of blind correlation operations are performed in the time domain and frequency domain based on the NB-IoT primary / secondary synchronization signal. Since the primary synchronization signal NPSS The 11 Orthogonal Frequency Division Multiplexing OFDMA symbols have correlation, so it is necessary to p...

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Problems solved by technology

[0002] The first step for starting up the UE of the narrowband Internet of Things NB-IoT (Narrow Band Internet of Things) system is to perform frequency synchronization on the frequency band it supports, find the center frequency point where NB-IoT cells may reside, and then pass a large number of The autocorrelation and cross-correlation operation of the cell is used to obtain the time and frequency synchronization of the cell. In this synchronization process, a large number of blind correlation operations are performed in the time domain and frequency domain based on the NB-IoT primary / secondary synchronization signal. Since the primary synchronization signal NPSS The 11 Orthogonal Frequency Division Multiplexing OFDMA symbols have correlation, so it is necessary to perform autocorrelation calculations between symbols on the received signals first, and then perform cross-correlation calculations at possible frequency points according to the correlation results, so the entire process calculation Relatively large amount

[0003] Aiming at the problem of large amount of calculation, this paper proposes a combination of GNSS global navigation system to obtain the time point of 1 ms of the air interface, so that the starting point of the data from the RF front end is the starting point of the air wireless interface 1 ms, and use DCXO to shift the possible frequency Limit within ±7.5KHz, thereby reducing the window range of blind search in the time domain and frequency domain to reduce the amount of calculation

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