A 5G terminal discovery method based on spectrum energy detection

Abstract

The present invention provides a 5G terminal discovery method based on spectrum energy detection, which belongs to the field of radio signal positioning, including: using a wireless receiver to receive and collect data; frequency shifting and downsampling the data; calculating the frame synchronization position of the data; determining the time slot position of the uplink signal in the current frame; converting the time domain data into frequency domain data; performing median filtering after obtaining the frequency domain energy of each OFDM symbol; converting the RE level energy into the RB level energy; respectively accumulating the spectrum energy of all the first 7 and last 7 OFDM symbols in a time slot; and performing energy judgment. The receiver of the present invention can directly calculate the frame header position in the baseband synchronization without relying on GPS for synchronization calibration. Only a short amount of data is needed to complete the synchronization, and there is no need to merge and desynchronize multiple frames of data. After synchronization, the energy of the entire signal bandwidth can be calculated without complex decoding process or time-frequency domain correlation.

Description

Technical Field

[0001] The present invention belongs to the field of radio signal positioning, and in particular relates to a 5G terminal discovery method based on spectrum energy. Background Art

[0002] In the prior art, the technology for locating radio signals is mainly an uplink correlation measurement technology, which uses a local sequence and an uplink correlation peak value method to calculate the uplink energy and thus discover the existence of a terminal.

[0003] In order to capture the target, it is generally necessary to use active equipment to attract the target to the active base station first, and then initiate uplink resource scheduling for the target to obtain the uplink signal, and then correlate the received uplink signal with the local signal to calculate the energy peak. However, this method is too complicated and can be easily discovered by end users, and it is unstable. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a 5G terminal discovery method based on spectrum energy detection to solve the problem that limited technology relies solely on active device discovery and the measurement method is too complicated.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A 5G terminal discovery method based on spectrum energy detection comprises the following steps:

[0007] Step S1: using a wireless receiver to receive and collect data;

[0008] Step S2: frequency shift the collected data, move the SSB center frequency to zero intermediate frequency, and downsample the data;

[0009] Step S3: using a synchronization algorithm to calculate the frame synchronization position of the data with reduced sampling;

[0010] Step S4: After synchronization is completed, the SFN system frame number, slot number, and uplink and downlink time slot ratio are obtained, and the time slot position of the uplink signal in the current frame is determined according to the configured uplink and downlink ratio and uplink cycle;

[0011] Step S5: extract data according to the time slot position, and convert the time domain data into frequency domain data by OFDM demodulation;

[0012] Step S6: For each OFDM symbol, extract the frequency domain data within the transmission bandwidth from the entire frequency domain, calculate the frequency domain energy, and then perform median filtering;

[0013] Step S7: converting the RE level energy into the RB level energy;

[0014] Step S8: Accumulate the spectrum energy of all the first 7 and last 7 OFDM symbols in a time slot respectively;

[0015] Step S9: Perform energy judgment on the accumulated energy to determine the existence of the 5G terminal.

[0016] Furthermore, the frequency shifting in step S2 includes the following process:

[0017] Calculate SSB frequency GSCN and center frequency Frequency difference , and then perform frequency shift calculation based on the calculated frequency difference. The frequency shift formula is as follows:

[0018] ,

[0019] Where t is time and j is an imaginary unit.

[0020] Furthermore, the downsampling in step S2 is only performed for the TDD mode.

[0021] Furthermore, the step S3 includes the following sub-steps:

[0022] Step S301: after obtaining the data after frequency shifting and downsampling in step 2, perform PSS time domain correlation to determine the position exceeding the threshold value and determine NID2;

[0023] Step S302: Divide the local sequence and the received data into two parts to perform frequency offset estimation;

[0024] Step S303: Find the SSS symbol position by shifting the length of two OFDM symbols backward from the starting position of the PSS, perform frequency offset compensation, then perform frequency domain conversion on the SSS, calculate the correlation peak, find the position of the SSS that exceeds the threshold, and find the PCI;

[0025] Step S304: Determine the frequency domain position of the PBCH DMRS according to the result of PCI mode 4, perform channel estimation according to the DMRS, and estimate RSRP and SINR while performing DMRS;

[0026] Step S305: According to the channel estimation result of PBCH, decode the MIB message according to the PBCH decoding process to obtain the current SSB index and other cell information.

[0027] Furthermore, in step S4, the uplink and downlink time slot ratio is obtained in advance from SIB1.

[0028] Furthermore, the step S5 includes the following sub-steps:

[0029] Step S501: The uplink data is obtained in advance relative to the downlink data, and the length of time for the early data acquisition satisfies the following formula:

[0030] ,

[0031] in, , ,in , ;

[0032] Step S502: After obtaining the uplink data, the time domain data is converted to the frequency domain by OFDM demodulation. When performing OFDM demodulation, the FFT points are set to , input 4096 sampling frequencies as The output is 4096 frequency domain sample points with a sampling rate of 122.88 MHz.

[0033] Furthermore, step S6 includes the following sub-steps:

[0034] Step S601: After obtaining an OFDM symbol A collection of frequency domain sample points Then, take the center of the frequency domain sample points, denoted as , is the number of central sample points in the frequency domain, and the energy of these frequency domain sample points is calculated, which is recorded as :

[0035] ,

[0036] Step S602: Filter using median filtering For high-energy interference points existing in the neighborhood window, the median filter sets the value of each sample point to the median value of all sample points in the neighborhood window of the high-energy interference point.

[0037] Furthermore, in step S7, all SCS grid energies in the Resource Grid are ,according to The continuous SCSs are grouped and summed to obtain the RB level spectrum energy The definition is as follows:

[0038] ,

[0039] in, , .

[0040] Furthermore, the energy judgment process in S9 is as follows: the spectrum energies of all the first 7 and last 7 OFDM symbols in a time slot are sorted in ascending order to obtain a sorted frequency domain energy set, the first 5 values ​​of the sorted frequency domain energy are taken, and the average is calculated to obtain the estimated noise power in this OFDM symbol. , then according to the estimated noise power , set the threshold for distinguishing signal from noise , which is defined as:

[0041] ,

[0042] in, Threshold Specific noise power Large dB number;

[0043] The presence of the 5G terminal is determined based on the threshold and judgment rules.

[0044] Furthermore, the judgment rule is: a half frame exceeds the threshold at least once in a frame of data.

[0045] The beneficial effects of the present invention are:

[0046] The receiver of the present invention can be synchronized and calibrated without relying on GPS, and can directly synchronize and calculate the frame header position in the baseband, and can be applied to portable devices, which is convenient to use. In the present invention, only a short amount of data is needed to complete synchronization, and there is no need to merge and desynchronize multiple frames of data. Once synchronization is completed, the energy of the entire signal bandwidth can be calculated without complex decoding process or time-frequency domain correlation. Based on the method of the present invention, the distance trend of the target can be determined.

[0047] The present invention has advantages in radio signal positioning performance, small amount of calculation, low requirements on hardware performance, easy implementation of product equipment, and can improve the economic benefits of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic flow chart of a 5G terminal discovery method based on spectrum energy detection provided by the present invention.

[0049] Figure 2 Schematic diagram of frequency domain energy after median filtering.

[0050] Figure 3 Schematic diagram of transferring RE level energy to RB level energy.

[0051] Figure 4 Schematic diagram of energy threshold decision. DETAILED DESCRIPTION

[0052] The technical solution provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0053] The present invention provides a 5G terminal discovery method based on spectrum energy detection, the process of which is as follows: Figure 1 As shown, the following steps are included:

[0054] Step S1: Use a wireless receiver to receive and collect data; usually use a radio receiver to sample and save the signal according to the set time and sampling rate. The receiver uses 100M bandwidth and 122.88M sampling rate.

[0055] Step S2: frequency shifting and downsampling the collected data.

[0056] The frequency shifting method is to use the 100M center frequency point configured by the AD (Analog-to-Digital Converter). Since the 5G SSB (Synchronization Signal Block) frequency GSCN (Global Synchronization Channel Number) is not at the center of the bandwidth, it is necessary to calculate GSCN and f c Frequency difference , and then perform frequency shift calculation based on the calculated frequency difference. The frequency shift formula is as follows:

[0057] ,

[0058] Where t is time and j is an imaginary unit.

[0059] When downsampling, the original 122.88M sampling rate data is filtered and extracted, and the sampling is downgraded to 7.86M. This is only for TDD (Time-division Duplex) mode, and FDD (Frequency-division Duplex) mode does not need synchronization.

[0060] Step S3: Calculate the frame synchronization position of the data using a synchronization algorithm for the downsampled data; specifically, the steps include:

[0061] Step S301: After obtaining the frequency shifted and downsampled data, the PSS (Primary Synchronization Signal) time domain correlation is performed to determine the position exceeding the threshold value and determine the NID2.

[0062] Step S302: Frequency offset estimation The local sequence and the received data are divided into two parts, and frequency offset estimation is performed.

[0063] Step S303: Find the SSS (Secondary Synchronization Signal) symbol position two OFDM symbols backward from the starting position of the PSS, perform frequency offset compensation, then perform frequency domain conversion on the SSS, calculate the correlation peak, find the position of the SSS that exceeds the threshold, and find the PCI (Physical Cell Identifier).

[0064] Step S304: Determine the frequency domain position of the PBCH (Physical Broadcast Channel) DMRS (Demodulation Reference Signal) according to the result of PCI Mode 4, perform channel estimation based on DMRS, and estimate RSRP (Reference Signal Received Power) and SINR (Signal to Interference and Noise Ratio) while performing DMRS.

[0065] Step S305: According to the channel estimation result of PBCH, the MIB (Master Information Block) message is decoded according to the PBCH decoding process to obtain the current SSB index and other cell information.

[0066] Step S4: After synchronization is completed, the SFN (System Frame Number), slot number, and uplink and downlink time slot ratio will be obtained. The uplink and downlink time slot ratio can be obtained from SIB1 in advance without separate analysis. According to the configured uplink and downlink ratio and uplink period, the time slot position of the uplink signal in the current frame is determined.

[0067] Step S5: Acquire data according to the time slot position, and perform OFDM demodulation on the time domain data to convert it into frequency domain data; this step acquires data synchronously, and includes the following sub-steps:

[0068] Step S501: In NR, there are a set of uplink frames and a set of downlink frames on the same carrier. Before a downlink frame starts, the UE (user equipment) sends an uplink frame corresponding to the downlink frame some time in advance, so the uplink data must be obtained in advance relative to the downlink data.

[0069] The length of this period satisfies:

[0070] ,

[0071] in, The advance offset is given by n-TimingAdvanceOffset in the RRC (Radio Resource Control) signaling of SIB1 (System Information Block 1). The n41 band SIB1 input parameters are known. ,in , So at this time ,correspond Next appointment sample points. Then the index of the sample point in the header of the downlink frame is When , the index of the uplink frame header sample point for: ,

[0072] Step S502: After obtaining the uplink data, the time domain data is converted to the frequency domain by OFDM demodulation. When performing OFDM demodulation, the FFT points are set to , input 4096 sampling frequencies as The output is 4096 frequency domain sample points with a sampling rate of 122.88 MHz.

[0073] Step S6: For each OFDM symbol, extract the frequency domain data within the transmission bandwidth (273RB*12) from the entire frequency domain, calculate the frequency domain energy, and then perform median filtering; including the following sub-steps:

[0074] Step S601: After obtaining an OFDM symbol A collection of frequency domain sample points Then, take the center of the frequency domain sample points, denoted as . Calculate the energy of these frequency domain sample points and record it as :

[0075] ,

[0076] Step S602: Due to unknown reasons, There are some non-signal bursts of high-energy interference in the memory, which need to be filtered. At this time, use the median filter to filter this high-energy interference point. The median filter sets the value of each sample point to the median of all sample points in a certain neighborhood window of the point.

[0077] Step S7: Convert the RE (Resource Element) level energy to the RB (Resource Block) level energy. For the energy calculation within the RB, since the frequency domain resource allocation of 5G NR is based on RB, the grid energy of all SCS (Sub Carrier Spacing) grids in the Resource Grid is converted into the energy of the RB (Resource Block). ,according to The continuous SCSs are grouped and summed to obtain The definition is as follows:

[0078] ,

[0079] in, , .

[0080] Step S8: Accumulate the spectrum energy of all the first 7 and last 7 OFDM symbols in a time slot respectively; specifically:

[0081] definition The frequency domain energy set obtained by summing the frequency domain energies of all OFDM symbols with the same frequency domain position in a single half-time slot is:

[0082] .

[0083] Step S9: Then perform energy judgment on the accumulated energy to determine the existence of the 5G terminal. The energy threshold judgment process is as follows: Sort in ascending order to obtain the sorted frequency domain energy set ,Pick The first five values ​​of are averaged to obtain the estimated noise power in this OFDM symbol. , defined as:

[0084] ,

[0085] is the smallest i-th value in the sorted frequency domain energy set.

[0086] Next, according to the estimated noise power , set the threshold for distinguishing signal from noise , which is defined as:

[0087] ,

[0088] in, Threshold Specific noise power Large dB number, set here As long as at least one half-frame exceeds the threshold in a frame of data, such as Figure 4 As shown, the existence of the 5G terminal can be determined.

[0089] Embodiment 1: Data implementation based on a 5G terminal discovery method based on spectrum energy detection provided by the present invention:

[0090] Step S1, use a 5G signal source, select TDD n41 center frequency 2565MHz to send; access the receiver end through the feeder, use the computing system to control the signal source to send signals, and obtain the original IQ data. The computing system sends a sampling request to the receiver, starts sampling after 10 seconds, and samples and saves 3s of original IQ data. The receiver sampling rate center frequency is 2565MHz, the sampling rate is 122.88MHz, and the sampled data is stored in the machine memory. The receiver sampling center frequency range is between 0~6GH, and the sampling rate is It is 122.88MHZ.

[0091] Step S2: The receiver first extracts 2457600 points of 20ms length from the original IQ data in the memory according to the extraction parameters sent by the computing system, and then calculates the SSB and carrier center frequency deviations. Here, the n41 SSB center frequency is 2524.95MHz, and the carrier center frequency is 2565MHz, so the deviation between the two is 40.05MHz. The signal is frequency-shifted by the calculated frequency difference, and the SSB center frequency is moved to the zero intermediate frequency. After the frequency shift, the data is downsampled from 122.88MHz to 7.68MHz. A half-band filter can be used for downsampling. After each filtering, the data is extracted every two points. Here, 4 filterings and 16-fold downsampling are performed.

[0092] Step S3: Perform PSS correlation on the downsampled data. The frame header position can be found through the correlation peak. In addition to finding the peak through PSS correlation, SSS correlation calculation is also required to calculate PCI. Then the MIB code stream is decoded through the demodulation algorithm. There is SFN number in MIB. Obtaining the SFN number is equivalent to knowing the slot number in disguise.

[0093] Step S4: After the synchronization is completed, SFN and slot number will be obtained according to the configured uplink and downlink ratio and uplink period. The uplink and downlink ratio here is obtained in advance from SIB1. The uplink and downlink ratio of n41 is a 5ms single period, that is, DDDDDDDSUU. In the 10ms data, slots 0 to 6 are downlink time slot data, slot 7 is a special time slot, slots 8 to 9 are uplink time slots, and the next 10ms is also DDDDDDDSUU, so the uplink time slots in the n41 frequency band are slot8, slot9, slot18, and slot19.

[0094] Step S5: Acquire uplink data according to the frame header position and time slot ratio obtained through synchronization. Since there is an offset value between the uplink and downlink time slots, uplink data needs to be acquired in advance. The uplink data acquisition offset value can be calculated in advance. The TDD n41 offset value is 2496. After acquiring the uplink data, perform OFDM demodulation on the time domain data and convert it into the frequency domain.

[0095] Step S6: For each OFDM symbol, extract the frequency domain data within the transmission bandwidth (273RB*12) from the entire frequency domain, calculate the frequency domain energy, and then perform median filtering, such as Figure 2 shown.

[0096] Step S7: Convert the RE level energy into RB level energy, and sum up the 12 RE energies to get 1 RB energy, such as Figure 3 shown.

[0097] Step S9: Accumulate the spectrum energy of all the first 7 and last 7 OFDM symbols in a time slot respectively.

[0098] Step S10: Then perform energy judgment on the accumulated energy, which is equivalent to processing according to half a time slot. As long as at least one half-frame exceeds the threshold in a frame of data, Figure 4 As shown, the existence of the 5G terminal can be determined.

[0099] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A 5G terminal discovery method based on spectrum energy detection, characterized in that: The steps include: Step S1: using a wireless receiver to receive and collect data; Step S2: frequency shift the collected data, move the SSB center frequency to zero intermediate frequency, and downsample the data; Step S3: using a synchronization algorithm to calculate the frame synchronization position of the data with reduced sampling; Step S4: After synchronization is completed, the SFN system frame number, slot number, and uplink and downlink time slot ratio are obtained, and the time slot position of the uplink signal in the current frame is determined according to the configured uplink and downlink ratio and uplink cycle; Step S5: extract data according to the time slot position, and convert the time domain data into frequency domain data by OFDM demodulation; Step S6: For each OFDM symbol, extract the frequency domain data within the transmission bandwidth from the entire frequency domain, calculate the frequency domain energy, and then perform median filtering; Step S7: converting the RE level energy into the RB level energy; Step S8: Accumulate the spectrum energy of all the first 7 and last 7 OFDM symbols in a time slot respectively; Step S9: Perform energy judgment on the accumulated energy to determine the existence of the 5G terminal; the energy judgment process is: sort the spectrum energies of all the first 7 and last 7 OFDM symbols in a time slot in ascending order to obtain a sorted frequency domain energy set, take the first 5 values ​​of the sorted frequency domain energy, and average them to obtain the estimated noise power in this OFDM symbol. , then according to the estimated noise power , set the threshold for distinguishing signal from noise , which is defined as: ， in, Threshold Specific noise power Large dB number; The existence of the 5G terminal is determined according to the threshold and the judgment rule; the judgment rule is: at least one half-frame exceeds the threshold in a frame of data.

2. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: The frequency shift in step S2 includes the following process: Calculate SSB frequency GSCN and center frequency Frequency difference , and then perform frequency shift calculation based on the calculated frequency difference. The frequency shift formula is as follows: ， Where t is time and j is an imaginary unit.

3. The 5G terminal discovery method based on spectrum energy detection according to claim 1 or 2, characterized in that: The downsampling in step S2 is performed only for the TDD mode.

4. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: The step S3 includes the following sub-steps: Step S301: after obtaining the data after frequency shifting and downsampling in step 2, perform PSS time domain correlation to determine the position exceeding the threshold value and determine NID2; Step S302: Divide the local sequence and the received data into two parts to perform frequency offset estimation; Step S303: Find the SSS symbol position by shifting the length of two OFDM symbols backward from the starting position of the PSS, perform frequency offset compensation, then perform frequency domain conversion on the SSS, calculate the correlation peak, find the position of the SSS that exceeds the threshold, and find the PCI; Step S304: Determine the frequency domain position of the PBCH DMRS according to the result of PCI mode 4, perform channel estimation according to the DMRS, and estimate RSRP and SINR while performing DMRS; Step S305: According to the channel estimation result of PBCH, decode the MIB message according to the PBCH decoding process to obtain the current SSBindex and other cell information.

5. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: In the step S4, the uplink and downlink time slot ratio is obtained in advance from SIB1.

6. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: The step S5 includes the following sub-steps: Step S501: The uplink data is obtained in advance relative to the downlink data, and the length of time for the early data acquisition satisfies the following formula: ， in, , ,in , ; Step S502: After obtaining the uplink data, the time domain data is converted to the frequency domain by OFDM demodulation. When performing OFDM demodulation, the FFT points are set to , input 4096 sampling frequencies as The output is 4096 frequency domain sample points with a sampling rate of 122.88 MHz.

7. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: The step S6 comprises the following sub-steps: Step S601: After obtaining an OFDM symbol A collection of frequency domain sample points Then, take the center of the frequency domain sample points, denoted as , is the number of central sample points in the frequency domain, and the energy of these frequency domain sample points is calculated, which is recorded as : ， Step S602: Filter using median filtering For high-energy interference points existing in the neighborhood window, the median filter sets the value of each sample point to the median value of all sample points in the neighborhood window of the high-energy interference point.

8. The 5G terminal discovery method based on spectrum energy detection according to claim 1, characterized in that: In step S7, all SCS grid energies in the Resource Grid are ,according to The continuous SCSs are grouped and summed to obtain the RB level spectrum energy The definition is as follows: ， in, , .

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