A signal reconstruction-based LTE cell search method under co-channel interference

Abstract

The application provides a signal reconstruction-based LTE cell search method under co-frequency interference, and belongs to the technical field of electric communication. The application comprises PSS timing synchronization, SSS synchronization and channel estimation, CRS channel estimation, PBCH demodulation and decoding, reconstructed PSS, SSS and PBCH, and elimination of the reconstructed PBCH, PSS and SSS signals from original received signals. The application firstly performs PSS and SSS synchronization, sorts PBCH according to power in the case that the power of interference sources has little difference, accurately positions the reconstructed PBCH, and then eliminates the reconstructed signal from the received signal to obtain a new received signal through the reconstructed signal, so that the synchronization probability and the PBCH decoding probability under co-frequency interference can be obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of telecommunications technology, and relates to LTE physical layer analysis technology for wireless communication, specifically to an LTE cell search method based on signal reconstruction under co-channel interference. Background Technology

[0002] When a terminal (UE) powers on or undergoes handover, it needs to establish a connection with the base station. During signal search, it needs to scan legal frequency points across various frequency bands for synchronization. After synchronization, debroadcasting is required. Afterward, the UE obtains the Physical Broadcast Channel (PBCH) information (MIB) from the base station and can then decode the System Information Block (SIB) information based on the MIB information and the information obtained during synchronization. Co-channel interference is a common occurrence in LTE cell search, where signals from multiple cells on the same frequency point overlap and cause interference. This means that PBCH demodulation needs to be performed under co-channel interference.

[0003] A relatively new solution in the existing technology is to estimate the channel of the strongest interference source, demodulate its PBCH signal, reconstruct the interference waveform, remove it from the received signal, eliminate the interference, and then demodulate the target PBCH information, which can remove the dominant interference. However, in practice, this solution is not ideal. After careful analysis, the following problems exist:

[0004] 1. Since co-channel interference affects not only the PBCH, but also the synchronization information PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal), the target cell is not easily synchronized under strong signal interference. Without proper reconstruction of the synchronization signal, subsequent direct reconstruction of the PBCH is of little significance.

[0005] 2. In application scenarios, there are often multiple interference sources, and the power of these sources is not significantly different. Therefore, the first PBCH decoding may result in multiple PBCHs. Due to the lack of identification of the strongest interference signal, it is impossible to determine which PBCH is being reconstructed.

[0006] 3. Existing technologies are based on theoretical simulations and are not implemented based on actual co-channel interference data. Furthermore, they assume the location of the PBCH is known and do not incorporate timing synchronization into the simulation, making them overly idealistic. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes an LTE cell search method based on signal reconstruction under co-channel interference, which improves the probability of resolving LTE broadcast signals under co-channel interference.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for LTE cell search based on signal reconstruction under co-channel interference includes the following steps:

[0010] Step 1: PSS timing synchronization, obtain the PSS start position by sliding correlation between the time domain and the local PSS signal;

[0011] Step 2: Obtain the SSS start position based on the PSS start position, perform frequency domain correlation to obtain the Physical Cell Identity (PCI), and obtain the SSS channel estimation result through channel estimation. ;

[0012] Step 3: Based on the PCI and the corresponding location information, perform channel estimation on the CRS to obtain... Calculate the RSRP channel energy;

[0013] Step 4: Demodulate and decode the PBCH to obtain its frequency domain information;

[0014] Step 5: When more than one PBCH is correctly solved, sort the PBCHs according to the RSRP channel energy and generate a local signal for the PBCH with the strongest power.

[0015] Step 6: Reconstruct PSS and SSS based on the SSS channel estimation results and the PSS and SSS local sequences, and reconstruct PSS and SSS based on the CRS channel estimation results. And the most powerful PBCH local signal reconstruction PBCH;

[0016] Step 7: Remove the reconstructed PBCH, PSS, and SSS signals from the original received signal, and then repeat steps 1-6.

[0017] Furthermore, in step 1, the starting position of PSS is obtained through the following process: performing sliding correlation operation on the three local PSS sequences and half-frame length data to obtain three half-frame length correlation peaks, and taking the maximum value of each correlation peak to obtain the three maximum correlation peak positions, which are the three starting positions of PSS.

[0018] Furthermore, in step 2, the Physical Cell Identity (PCI) is obtained through the following process: The locations of the six SSSs under TDD and FDD are calculated based on the locations of the three PSSs respectively. Then, the SSS received data at the six locations are extracted and correlated with the corresponding 336 local SSS sequences in the frequency domain to obtain six sets of frequency domain correlation values ​​of length 336. The three locations of the PSS correspond to 2*336 correlation peaks respectively. The maximum correlation peak at each location of the PSS, its position in the 336 correlation peaks, and the multiplexing mode are taken. There are three maximum correlation peak positions and three multiplexing modes for the three locations. Then, three PCIs are calculated based on the three maximum correlation peak positions and three NID2 values.

[0019] Furthermore, in step 2, channel estimation is performed three times to obtain the channel estimation results of three SSSs. .

[0020] Furthermore, in step 4, the PBCH is demodulated and decoded three times.

[0021] Furthermore, step 6 specifically includes the following process:

[0022] In the frequency domain, PSS local sequences and SSS local sequences are generated respectively. The PSS local sequences and SSS local sequences are then multiplied by the SSS channel estimation result in the frequency domain. After being converted to the time domain, CP is added to reconstruct the PSS and SSS signals respectively; the PSS local sequence is generated by NID2, and the SSS local sequence is generated by NID1 and half-frame information.

[0023] The bit information after PBCH decoding is sent to the PBCH transmitter for bit-level encoding, scrambling, and QPSK modulation. Then, it is combined with the number of antenna ports and CRS mapping to form a resource grid. After being converted into the time domain, CP is added to complete PBCH reconstruction.

[0024] Furthermore, step 7, which involves removing the reconstructed PBCH, PSS, and SSS signals from the original received signal, specifically includes the following process:

[0025] Based on the position of the PSS, subtract the reconstructed PSS signal from the original received signal;

[0026] Based on the location of the SSS, subtract the reconstructed SSS signal from the original received signal;

[0027] Based on the position of the PBCH, the reconstructed PBCH signal is subtracted from the original received signal.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention proposes a search scheme under co-channel interference. First, PSS and SSS synchronization are performed. When the power of the interference sources is not significantly different, the PBCH is sorted according to the power to accurately locate the reconstructed PBCH. Then, the reconstructed signal is removed from the received signal to obtain a new received signal. This can significantly improve the synchronization probability and the PBCH resolution probability under co-channel interference. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the LTE cell search method based on signal reconstruction under co-channel interference provided by the present invention. Detailed Implementation

[0031] The technical solutions provided by the present invention will be described in detail below with reference to specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0032] The LTE cell search method based on signal reconstruction under co-channel interference provided by this invention has the following process: Figure 1 As shown, it includes the following steps:

[0033] Step 1: PSS timing synchronization. The starting position of the PSS is obtained by sliding correlation between the local PSS signal and the time domain. Since there are three NID2 (Physical Layer Identity in the Physical Layer Cell Identity Group) values ​​(0, 1, and 2), there will be three starting positions for the PSS. The specific process for obtaining the PSS starting position is as follows: For the PSS, a sliding correlation operation is performed on the three local PSS sequences and half-frame length data to obtain three half-frame length correlation peaks. The maximum value of each correlation peak is taken to obtain the positions of the three maximum correlation peaks.

[0034] Step 2: Obtain the starting position of the SSS based on the starting position of the PSS, and perform frequency domain correlation to obtain three Physical Cell IDs (PCIs). Then, perform channel estimation three times to obtain the channel estimation results for the three SSSs. The specific process for obtaining PCI includes: calculating six SSS positions under TDD (Time Division Duplexing) and FDD (Frequency Division Duplexing) based on the positions of the three PSSs; then extracting the SSS received data at these six positions and correlating it with the corresponding 336 local SSS sequences in the frequency domain to obtain six sets of frequency domain correlation values ​​of length 336. The three PSS positions correspond to 2*336 correlation peaks. The maximum correlation peak at each position, its position among the 336 correlation peaks, and the multiplexing mode are taken. There are three maximum correlation peak positions and three multiplexing modes for the three positions. Then, based on the three maximum correlation peak positions and the three NID2 values ​​mentioned above, three PCIs can be calculated.

[0035] Step 3: Based on the PCI and the corresponding location information, perform channel estimation on the CRS (Cell-specific reference signal) to obtain... Calculate the RSRP (Reference Signal Received Power) channel energy.

[0036] Step 4: Demodulate and decode the PBCH to obtain its frequency domain information. Since it will traverse 3 PCIs, the PBCH will be demodulated and decoded 3 times.

[0037] Step 5: If more than one PBCH is correctly solved, the PBCHs need to be sorted according to the RSRP channel energy, and the local signal is generated from the PBCH signal with the strongest power.

[0038] Step 6: Reconstruct PSS and SSS based on the SSS channel estimation results, PSS, and SSS local sequence; reconstruct PSS and SSS based on the CRS channel estimation results. And the PBCH is reconstructed from the signal generated locally by the PBCH with the highest power. Specifically, the process includes the following:

[0039] In the frequency domain, PSS local sequences (ZC (Zadoff-Chu) sequences generated from NID2) and SSS local sequences (0 and 1 sequences generated from NID1 (physical layer cell identity group) and half-frame information) are generated respectively, and then multiplied in the frequency domain by the SSS channel estimation result. Then, after converting to the time domain, a CP (Cyclic Prefix) is added to reconstruct the PSS and SSS signals respectively.

[0040] The bit information decoded from the PBCH is sent to the PBCH transmitter. Based on the bit stream decoded from the PBCH, bit-level encoding processing is performed (including adding CRC, masking, convolutional coding, and rate matching). After scrambling and QPSK (Quad-Phase Shift Keyed) modulation, the data is combined with the number of antenna ports and CRS mapping to form a resource grid. This grid is then multiplied in the frequency domain by... Then, it is converted to the time domain and CP is added to complete the PBCH reconstruction.

[0041] As a parallel optimization method, the PSS and SSS can also be reconstructed using PBCH pilots. The specific reconstruction process is as follows: Local frequency domain PSS and SSS are generated based on the PCI, and then the channels estimated using PBCH pilots are... After being converted to the time domain, the local PSS and SSS sequences are placed in their corresponding time domain positions according to their synchronized positions.

[0042] Step 7: Remove the reconstructed PBCH, PSS, and SSS signals from the original received signal, and then repeat steps 1-6. Specifically, this includes:

[0043] Based on the position of the PSS, the reconstructed PSS signal is subtracted from the original received signal.

[0044] Based on the location of the SSS, the reconstructed SSS signal is subtracted from the original received signal.

[0045] Based on the position of the PBCH, the reconstructed PBCH signal is subtracted from the original received signal.

[0046] Specifically, the following information needs to be stored during the synchronization and PBCH demodulation process before reconstruction: PCI physical cell identity, number of antenna ports, channel estimated by SSS, location information of PSS and SSS, half-frame information and frame start position, PBCH channel estimated and interpolated based on CRS channel, and bit information after PBCH decoding.

[0047] To address co-channel interference scenarios, we captured downlink broadcast data from LTE at frequencies 100, 1309, 1823, 1850, 2452, 3590, 36725, 38400, and 41134, encompassing both TDD and FDD multiplexing modes. The data was converted into .mat files, easily readable by Matlab. These data files were then compared between simulation platforms without PSS, SSS, and PBCH reconstruction elimination and those using the proposed solution. The results are shown in Table 1.

[0048] Table 1:

[0049] rx0_1307_11_iqData_20231212151416.mat 11, 11, rx0_1309_345_iqData_20231023152422.mat 35,345, 35,345, rx0_1309_345_iqData_20231023152440.mat 35,345, 345, rx0_1309_345_iqData_20231023154032.mat 35,345, 345, rx0_1309_345_iqData_20231023154521.mat 345, 345, rx0_1309_345_iqData_20231023160058.mat 345, 345, rx0_1309_345_iqData_20231023160159.mat 35,345, 35,345, rx0_1309_345_iqData_20231214152743.mat 35,345, 35, rx0_1309_345_iqData_20231214153523.mat 35,345, 345, rx0_1650_438_iqData_20231025163000.mat 438, 438, rx0_1650_438_iqData_20231025163833.mat 308, , rx0_1650_438_iqData_20231212160535.mat 3,291,308, , rx0_1650_439_iqData_20231208142156.mat 439, 439, rx0_1650_439_iqData_20231208142750.mat 439, 439, rx0_1650_440_iqData_20231016165413.mat 440, 440, rx0_1650_440_iqData_20231016165555.mat 440, 440, rx0_38400_172_iqData_20231007155458.mat 72,172, 172, rx0_38400_18_iqData_20231023161100.mat 18, 18, rx0_38400_18_iqData_20231023161140.mat 18,146, 18, rx0_40940_246_iqData_20231214143004.mat 246,250, 246, rx0_40940_246_iqData_20231214143108.mat 246,250, 246, rx0_40940_246_iqData_20231214144154.mat 246,250, 250,

[0050] As shown in the table above, the proposed solution can significantly improve the PCI scan rate and PBCH resolution rate under co-frequency interference. The optimized method improves the PBCH resolution rate by approximately 50% compared to the unoptimized method. The improvement rate is calculated by dividing the number of additional data sets resolved by the optimized method based on current data compared to the existing method by the total number of data sets. Table 1 shows only a representative portion of the data.

[0051] The solution of this invention can be applied to a frequency sweeper. The method is implemented through a software algorithm and is loaded into the physical layer algorithm part of the frequency sweeper.

[0052] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for LTE cell search based on signal reconstruction under co-channel interference, characterized in that, Includes the following steps: Step 1: PSS timing synchronization, obtain the PSS start position by sliding correlation between the time domain and the local PSS signal; Step 2: Obtain the SSS start position based on the PSS start position, perform frequency domain correlation to obtain the Physical Cell Identity (PCI), and obtain the SSS channel estimation result through channel estimation. ; Step 3: Based on the PCI and the corresponding location information, perform channel estimation on the CRS to obtain... Calculate the RSRP channel energy; Step 4: Demodulate and decode the PBCH to obtain its frequency domain information; Step 5: When more than one PBCH is correctly solved, sort the PBCHs according to the RSRP channel energy and generate a local signal for the PBCH with the strongest power. Step 6: Reconstruct PSS and SSS based on the SSS channel estimation results and the PSS and SSS local sequences, and reconstruct PSS and SSS based on the CRS channel estimation results. And the most powerful PBCH local signal reconstruction PBCH; specifically including the following processes: In the frequency domain, PSS local sequences and SSS local sequences are generated respectively. The PSS local sequences and SSS local sequences are then multiplied by the SSS channel estimation result in the frequency domain. After being converted to the time domain, CP is added to reconstruct the PSS and SSS signals respectively; the PSS local sequence is generated by NID2, and the SSS local sequence is generated by NID1 and half-frame information. The bit information after PBCH decoding is sent to the PBCH transmitter, where it undergoes bit-level encoding, scrambling, and QPSK modulation. Then, it is combined with the number of antenna ports and CRS mapping to form a resource grid. After being converted into the time domain, CP is added to complete PBCH reconstruction. Step 7: Remove the reconstructed PBCH, PSS, and SSS signals from the original received signal, and then repeat steps 1-6.

2. The LTE cell search method based on signal reconstruction under co-channel interference as described in claim 1, characterized in that, In step 1, the starting position of PSS is obtained through the following process: Perform sliding correlation operation on the three local PSS sequences and half-frame length data to obtain three half-frame length correlation peaks. Take the maximum value of each correlation peak to obtain the three maximum correlation peak positions, which are the three starting positions of PSS.

3. The LTE cell search method based on signal reconstruction under co-channel interference as described in claim 2, characterized in that, In step 2, the Physical Cell Identity (PCI) is obtained through the following process: The positions of the six SSSs under TDD and FDD are calculated based on the starting positions of the three PSSs. Then, the SSS received data at the six positions are extracted and correlated with the corresponding 336 local SSS sequences in the frequency domain to obtain six sets of frequency domain correlation values ​​of length 336. The three positions of the PSS correspond to 2*336 correlation peaks. The maximum correlation peak at each position of the PSS, its position among the 336 correlation peaks, and the multiplexing mode are taken. There are three maximum correlation peak positions and three multiplexing modes for the three positions. Then, three PCIs are calculated based on the three maximum correlation peak positions and three NID2 values.

4. The LTE cell search method based on signal reconstruction under co-channel interference as described in claim 3, characterized in that, In step 2, channel estimation is performed three times to obtain the channel estimation results of three SSSs. .

5. The LTE cell search method based on signal reconstruction under co-channel interference as described in claim 4, characterized in that, In step 4, the PBCH is demodulated and decoded three times.

6. The LTE cell search method based on signal reconstruction under co-channel interference as described in claim 1, characterized in that, Step 7, which involves removing the reconstructed PBCH, PSS, and SSS signals from the original received signal, specifically includes the following process: Based on the position of the PSS, subtract the reconstructed PSS signal from the original received signal; Based on the location of the SSS, subtract the reconstructed SSS signal from the original received signal; Based on the position of the PBCH, the reconstructed PBCH signal is subtracted from the original received signal.

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