CN113162878A - PSS symbol synchronization method applied to negative signal-to-noise ratio 5GNR system - Google Patents

Abstract

A PSS symbol synchronization method applied to a negative signal-to-noise ratio (SNR) 5GNR system. The method comprises the steps of firstly acquiring data according to signal bandwidth by adopting a sampling rate matched with the signal bandwidth, finishing down-conversion to obtain a baseband signal, and then correlating the baseband signal with a locally produced data block beam8_ local _ PSS containing the PSS to finish PSS symbol synchronization. The received signal power processing is added in the correlation process, and the accuracy of signal detection under the negative signal-to-noise ratio is further improved.

Description

PSS symbol synchronization method applied to negative signal-to-noise ratio 5GNR system

Technical Field

The invention relates to the field of downlink signal identification of a 5GNR system, in particular to a PSS symbol synchronization method under a negative signal-to-noise ratio.

Background

The 5G, a fifth generation mobile communication technology, is an extension after 4G, and is a strong catalyst for leading the interconnection of everything, and 5G provides a peak speed at least ten times of 4G, a transmission delay in millisecond level and a connection capacity in billions level with a brand-new mobile communication system architecture.

At present, China 5G has entered into a pre-commercial stage, 5G network experiments are widely developed in multiple cities, and demodulation and analysis of downlink signals of 5G base stations become more important. The first step of demodulation of a downlink signal of a 5GNR base station is cell search, the first step of the cell search is primary synchronization PSS signal identification, and currently, PSS search mainly focuses on frequency offset resistance, and no design aiming at negative signal-to-noise ratio exists.

In a 5GNR practical base station, 8 beams are usually transmitted, each beam contains one SSB, and each SSB contains four OFDM symbols, i.e., PSS, SSS, and PBCH. The time domain resource allocation is related to the system setting Case, the time domain position is inconsistent between different cases and SSBs, and the following table lists part of the configuration.

Disclosure of Invention

The invention aims to solve the problem of high PSS searching difficulty under a negative signal-to-noise ratio and provides a PSS symbol synchronization method applied to a negative signal-to-noise ratio 5GNR system.

Technical scheme of the invention

A PSS symbol synchronization method applied to a negative signal-to-noise ratio (SNR) 5GNR system comprises the following steps:

step 1, acquiring 5GNR data by adopting a sampling rate matched with the signal bandwidth according to the signal bandwidth;

step 2, intercepting a 20ms baseband signal by down-conversion, wherein the length of the baseband signal is 5GNRdata _ SIZE;

step 3, searching primary synchronization PSS;

step 3.1, generating a local primary synchronization PSS signal;

step 3.2, the data block beam8_ local _ PSS containing the PSS is formed by splicing;

step 3.2.1, generating a time domain local signal PSS with the length of FFT _ size, copying the tail of the PSS to form a CP with the length of CP _ size, splicing the CP with the head of the PSS to form PSS _ OFDM of one beam locally, wherein the length of the PSS is FFT _ size + CP _ size; (ii) a

Step 3.2.2, according to different cases of receiving 5GNR signals, filling zeros with corresponding lengths among 8 PSS _ OFDM to form beam8_ local _ PSS;

step 3.3, cross-correlation including power processing;

step 3.3.1, intercepting a baseband signal with the length of beam8_ local _ PSS as window _ data, multiplying and adding the conjugate of the local beam8_ local _ PSS and the window data window _ data to obtainCOR _ sum 1;

step 3.3.2, multiplying and adding the conjugate of the data window _ data in the window and the data window _ data in the window to obtainCOR _ sum 2;

3.3.3, dividing COR _ sum1 by COR _ sum2 to obtain a correlation peak COR _ sum;

step 3.4, detecting the maximum peak to complete the primary synchronization PSS symbol synchronization

Step 3.4.1, traversing a baseband signal with the length of 20ms to obtain a correlation sequence COR _ sum (k), wherein k is 1, 2, … 5GNRdata _ SIZE;

and 3.4.2, taking the maximum value of COR _ sum (k), recording the maximum value position max _ index, and finishing the primary synchronization PSS search.

The invention has the advantages and beneficial effects that:

the invention completes PSS capturing identification under negative signal-to-noise ratio by constructing beam8_ local _ PSS in time domain to perform accumulation correlation with received signals and performing cross correlation of processing power. Through simulation and test, the method can improve the PSS identification performance of the 5GNR system under the negative signal-to-noise ratio.

Drawings

FIG. 1 is a flow chart of the PSS acquisition method of the present invention;

FIG. 2 is a diagram of beam8_ local _ PSS configuration according to the present invention;

FIG. 3 is a diagram of the correlation results of the PSS search in the embodiment.

Detailed Description

Example 1:

in the experimental environment of the embodiment, R & S FSW-K144 is used as a 5GNR signal source, and a German force E8900A 5GNR portable spectrometer is used as a signal receiving platform to collect data. The low noise was-110 dBm when data was collected by Deli E8900A. The 5GNR signal was set to 10M system bandwidth, conventional CP length, 30k subcarrier spacing, CaseC, transmit frequency 2524.95MHz, signal transmit power-130 dBm, 20dB lower than the low noise of the E8900A machine.

A PSS symbol synchronization method applied to a negative signal-to-noise ratio (SNR) 5GNR system is disclosed, and the specific flow is shown in figure 1, and the method comprises the following steps:

step (1) acquiring 5GNR data by adopting a 15.36MHz sampling rate;

step (2) down-conversion is carried out to intercept 20ms baseband signals, and the length is 5GNRdata _ SIZE;

and (3) carrying out primary synchronization PSS search, comprising the following steps:

(3.1) generating a local primary synchronization, PSS, signal;

(3.2) piecing together a data block beam8_ local _ PSS containing PSS, see fig. 2;

step 3.2.1, generating a time domain local signal PSS with the length of 512, copying the tail part of the time domain local signal PSS to form a CP with the length of 36, splicing the CP at the head part of the PSS to form a local PSS _ OFDM of beam with the length of 548;

step 3.2.2, according to the CaseC and the transmission frequency of the 5GNR signal being 2524.95MHz, the OFDM positions where 8 SSBs are located are 2, 8, 16, 22, 30, 36, 44 and 50, respectively, the lengths of zeros to be filled are (512+36) × (5, 7, 5, 7, 5) } {2740, 3836, 2740, 3836, 2740, 3836 and 2740}, zeros with corresponding lengths are filled between 8 PSS _ OFDM, so as to form beam8_ local _ PSS;

(3.3) cross-correlation including power processing, comprising the steps of:

(3.3.1) intercepting a baseband signal with the length of beam8_ local _ PSS as window _ data, multiplying and adding the conjugate of local beam8_ local _ PSS and window data window _ data to obtainCOR _ sum 1;

(3.3.2) multiplying and adding the conjugate of the data window _ data in the window and the data window _ data in the window to obtainCOR _ sum 2;

(3.3.3) COR _ sum1 divided by COR _ sum2 to obtain a correlation peak COR _ sum;

step (3.4) detecting the maximum peak to complete the primary synchronization PSS symbol synchronization, comprising the following steps:

step (3.4.1) of traversing the baseband signal with the length of 20ms to obtain a correlation sequence COR _ sum (k), where k is 1, 2, … 5, and 5GNRdata _ SIZE, where 5GNRdata _ SIZE in this embodiment is 90000;

(3.4.2) taking the maximum value of COR _ sum (k), recording the maximum value position max _ index, and completing the primary synchronization PSS search, wherein the primary synchronization PSS position is 87512 in the embodiment.

Fig. 3 is a correlation result diagram generated by using power-containing processing correlation in the embodiment, and it can be seen that under the condition of a negative signal-to-noise ratio of 20dB, an obvious correlation peak still exists, so that PSS symbol synchronization is accurately achieved, and a clear correlation peak cannot be obtained by using conventional single beam frequency domain PSS correlation accumulation.

Claims (4)

1. A PSS symbol synchronization method applied to a negative signal-to-noise ratio (SNR) 5GNR system is characterized by comprising the following steps of:

step 1, acquiring 5GNR data by adopting a sampling rate matched with the signal bandwidth according to the signal bandwidth;

step 2, intercepting a 20ms baseband signal by down-conversion, wherein the length of the baseband signal is 5GNRdata _ SIZE;

step 3, searching primary synchronization PSS;

step 3.1, generating a local primary synchronization PSS signal;

step 3.2, the data block beam8_ local _ PSS containing the PSS is formed by splicing;

step 3.3, cross-correlation including power processing;

and 3.4, detecting the maximum peak to finish the primary synchronization PSS symbol synchronization.

2. The PSS symbol synchronization method applied in a negative SNR 5GNR system as claimed in claim 1, wherein the piecing of step 3.2 into a data block beam8_ local _ PSS containing PSS comprises the following steps:

step 3.2.1, generating a time domain local signal PSS with the length of FFT _ size, copying the tail of the PSS to form a CP with the length of CP _ size, splicing the CP with the head of the PSS to form PSS _ OFDM of one beam locally, wherein the length of the PSS is FFT _ size + CP _ size;

and 3.2.2, filling zeros with corresponding lengths among 8 PSS _ OFDM according to different cases of receiving the 5GNR signals to form beam8_ local _ PSS.

3. The PSS symbol synchronization method as claimed in claim 1, wherein the cross-correlation including power processing in step 3.3 comprises the following steps:

step 3.3.1, intercepting a baseband signal with the length of beam8_ local _ PSS as window _ data, multiplying and adding the conjugate of the local beam8_ local _ PSS and the window data window _ data to obtain COR _ sum 1;

in step 3.3.2, the conjugate of the window data window _ data is multiplied and added with the window data window _ data to obtain COR _ sum 2.

In step 3.3.3, COR _ sum1 is divided by COR _ sum2 to obtain the correlation peak COR _ sum.

4. The PSS symbol synchronization method applied to a negative SNR 5GNR system as claimed in claim 1, wherein said detecting the maximum peak in step 3.4 to complete the PSS symbol synchronization of the primary synchronization comprises the steps of:

step 3.4.1, traversing a baseband signal with the length of 20ms to obtain a correlation sequence COR _ sum (k), wherein k is 1, 2, … 5GNRdata _ SIZE;

and 3.4.2, taking the maximum value of COR _ sum (k), recording the maximum value position max _ index, and finishing the primary synchronization PSS search.

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