CN117544271A

CN117544271A - Cell searching method and device and terminal equipment

Info

Publication number: CN117544271A
Application number: CN202311704976.2A
Authority: CN
Inventors: 吴伟; 朱晓意; 杨殷; 张凯
Original assignee: Beijing Ziguang Zhanrui Communication Technology Co Ltd
Current assignee: Beijing Ziguang Zhanrui Communication Technology Co Ltd
Priority date: 2023-12-12
Filing date: 2023-12-12
Publication date: 2024-02-09

Abstract

The application discloses a cell searching method and device and terminal equipment, wherein the method comprises the following steps: receiving a time domain signal; acquiring PSS frequency domain sequences of different cell identifications according to the received time domain signals; performing multi-scale frequency offset pre-compensation on the PSS frequency domain sequence to obtain a plurality of different frequency offset compensation sequences; and performing time domain sliding correlation on a plurality of different frequency offset compensation sequences of different cell identifications and the received time domain signals so as to perform PSS detection. According to the method and the device for detecting the frequency offset, frequency offset with different ranges and different precision can be processed, the frequency offset tolerance of PSS detection is improved, and the robustness of cell search is improved.

Description

Cell searching method and device and terminal equipment

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a cell search method and apparatus, and a terminal device.

Background

Cell search is the first step of a User Equipment (UE) obtaining a New Radio (NR) service, and the UE can search for and find a suitable cell through cell search, and then access the cell. The UE not only needs to perform cell search when it is powered on, but also can search neighbor cells continuously to obtain synchronization and estimate the receiving quality of cell signals so as to determine whether to perform cell switching or reselection.

Cell search is a process in which a User Equipment (UE) performs downlink time and frequency synchronization using a Cell synchronization signal and obtains a Physical Cell ID (PCI).

Estimation of time offset and frequency offset is a core problem to be solved by cell search. On the one hand, when the initial access is performed, the granularity of the Synchronization grid (Synchronization SymbolRaster, SS master) reaches 1.2/1.44/17.28MHz, and the deviation of one SSRaster during the sweep frequency treatment can lead to the frequency error of tens of times of SCS (Subcarrier Spacing ) number facing the cell search. In addition, there is also a frequency mismatch of local oscillators of the UE and the base station (gndeb, gNB), doppler shift caused by high-speed motion of the UE, and further expansion of frequency error is caused. Therefore, when the primary synchronization signal (Primary Synchronization Signal, PSS) is detected, a frequency deviation of several tens to hundreds times the number of SCS may be faced. On the other hand, when the secondary synchronization signal (Secondary Synchronization Signal, SSS) is detected, the residual time is too large, possibly resulting in cell group number identificationAnd detecting errors, and causing network searching failure of the UE.

The core performance index of cell search is the time delay of detecting the cell by the UE, and is mainly determined by PSS detection and SSS detection time. The cell search algorithm is not standardized, and the current cell search algorithm is mainly divided into a cross correlation method, an autocorrelation method and a difference method. Wherein:

the cross-correlation method is that UE carries out cross-correlation operation with a received signal through a local PSS or SSS sequence, and the synchronization of frequency offset and the detection of PCI are completed through incoherent detection. The spreading gains of the PSS and SSS sequences are mainly used here, where the spreading factor of PSS and SSS is 127, and the corresponding system gain is 21.03dB, so that the system can operate in an environment with very low Signal-to-Noise Ratio (SNR).

The autocorrelation method mainly considers the periodicity of the synchronous signal block (Synchronization Signal Block, SSB) signals and the autocorrelation operation of the PSS and SSS sequences, and has stronger time-frequency offset tolerance compared with the cross-correlation operation. The specific method is that firstly, PSS or SSS signals in different periods are utilized to calculate the autocorrelation, the time frequency offset is estimated, and then, PCI detection is carried out on the basis.

The difference method is that UE carries out conjugate multiplication on a local PSS sequence and a received PSS sequence, and carries out cross correlation on the multiplication and integration into a front section and a rear section, calculates phase accumulation, estimates frequency offset according to sampling time, and then completes synchronization of the frequency offset when residual and detection of PCI on the basis.

These existing algorithms described above all have certain drawbacks: the traditional cross-correlation method has poor tolerance to time offset and frequency offset, and is easy to generate false detection; the autocorrelation method needs long-period signal reception, and has harsh conditions; the frequency offset estimation accuracy of the difference method is very high, but the maximum range can only be within 1 subcarrier interval range, and certain requirements are met on SNR conditions. Therefore, the existing cell search method cannot cope with the serious time-frequency offset problem, and the time-frequency offset or the frequency offset is too serious, which can cause the degradation of the cell detection performance and the UE network residence.

Disclosure of Invention

The embodiment of the application provides a cell searching method and device and terminal equipment, which can process frequency offsets with different ranges and different precision so as to improve the frequency offset tolerance of PSS detection and improve the robustness of cell searching.

In order to solve the technical problems, the embodiment of the application provides the following technical scheme:

in one aspect, an embodiment of the present application provides a cell search method, where the method includes:

receiving a time domain signal;

acquiring PSS frequency domain sequences of different cell identifications according to the received time domain signals;

performing multi-scale frequency offset pre-compensation on the PSS frequency domain sequence to obtain a plurality of different frequency offset compensation sequences;

and performing time domain sliding correlation on a plurality of different frequency offset compensation sequences of different cell identifications and the received time domain signals so as to perform PSS detection.

Optionally, the time domain signal is a non-ideal signal with a time offset and a frequency offset.

Optionally, the range of the multi-scale frequency offset precompensation is determined from a total carrier frequency offset.

Optionally, the performing multi-scale frequency offset pre-compensation on the PSS frequency domain sequence includes:

performing multi-scale frequency offset precompensation on the PSS frequency domain sequence in a time domain by adopting a phase rotation mode; and/or

And performing multi-scale frequency offset precompensation on the PSS frequency domain sequence in a frequency domain by adopting a cyclic shift mode.

Optionally, the PSS frequency-domain sequence is a 127-bit original PSS frequency-domain sequence;

the performing multi-scale frequency offset precompensation on the PSS frequency domain sequence in the frequency domain by adopting a cyclic shift mode comprises the following steps:

generating a first PSS frequency domain sequence with set digits according to the original PSS frequency domain sequence;

and performing cyclic shift on the first PSS frequency domain sequence.

Optionally, the generating the first PSS frequency-domain sequence with the set number of bits according to the original PSS frequency-domain sequence includes:

zero padding the original PSS frequency domain sequence toPerforming IFFT processing on the bits to obtain a first time domain SSB signal;

performing conjugate reverse order zero padding to the first time domain SSB signalBits are processed by FFT to obtain a first frequency domain signal;

n-ary of the first frequency domain signal _OSR Double oversampling to obtainA first PSS frequency domain sequence of bits;

wherein,number of FFT processing points for SSB signal in first time domain,/-for>For FFT processing point number for PSS detection, N _OSR Is a multiple of the oversampling.

Optionally, the method further comprises:

performing frequency offset compensation processing on the received time domain signals, and converting the time domain signals into frequency domain received signals;

and respectively carrying out frequency domain linear correlation on the frequency domain received signal and the segmented data of the local SSS sequence, and carrying out SSS detection according to the average result of multiple segmented correlation combination.

Optionally, the method further comprises: in the case of multi-segment SSS detection, if the total sequence length required by the segments exceeds the length of the frequency domain received signal, the length of the frequency domain received signal is made to reach the total sequence length by supplementing 0.

On the other hand, the embodiment of the application also provides a cell searching device, which comprises:

a receiving module for receiving the time domain signal;

the PSS frequency domain sequence acquisition module is used for acquiring PSS frequency domain sequences of different cell identifications according to the received time domain signals;

the pre-compensation module is used for carrying out multi-scale frequency offset pre-compensation on the PSS frequency domain sequence to obtain a plurality of different frequency offset compensation sequences;

and the PSS detection module is used for performing time domain sliding correlation on a plurality of different frequency offset compensation sequences of different cell identifications and the received time domain signals so as to perform PSS detection.

Optionally, the apparatus further comprises:

the compensation processing module is used for performing frequency offset compensation processing on the received time domain signals and converting the received time domain signals into frequency domain received signals;

and the SSS detection module is used for carrying out multi-segment combined frequency domain linear correlation on the frequency domain received signals so as to carry out SSS detection.

On the other hand, the embodiment of the application also provides a terminal device, and the cell searching device is the terminal device.

In another aspect, embodiments of the present application also provide a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the cell search method described above.

In another aspect, an embodiment of the present application further provides a terminal device, including a memory and a processor, where the memory stores a computer program that can be executed on the processor, and the method is characterized in that the processor executes the steps of the cell search method described above when executing the computer program.

According to the cell searching method, the cell searching device and the terminal equipment, frequency offset precompensation is achieved through multi-scale cyclic shift, frequency offsets with different ranges and different precision can be processed, and therefore frequency offset tolerance of PSS detection is effectively improved. And the PSS frequency offset pre-compensation is realized through multi-scale cyclic shift, and the realization complexity is low. In addition, the maximum range and minimum precision of frequency offset precompensation during PSS detection and the searching step length and step number can be freely configured, so that the flexibility of the scheme is improved.

Further, time bias offset is realized through multi-segment merging processing, so that the time bias tolerance of SSS detection is improved. Furthermore, the number of segments processed by the segmentation process of the SSS detection can be freely configured, and can be flexibly configured according to the requirement.

Drawings

FIG. 1 is a schematic diagram of SSB time-frequency resources;

fig. 2 is a flowchart of a cell search method provided in an embodiment of the present application;

FIG. 3 is a schematic diagram of a detection result of a time domain sliding related PSS in an embodiment of the present application;

FIG. 4 is a schematic diagram of the results of the frequency-dependent SSS detection in the embodiment of the present application;

FIG. 5 is a schematic diagram of SSS detection probability at different segmentation numbers in an embodiment of the present application;

fig. 6 is a schematic structural diagram of a cell search apparatus according to an embodiment of the present application;

fig. 7 is another schematic structural diagram of a cell search apparatus provided in an embodiment of the present application;

fig. 8 is a schematic hardware structure of a terminal device according to an embodiment of the present application.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below.

In order to support cell search, NR defines 1008 different PCIs in total, corresponding toAs shown in formula (1). The set of all PCI's is divided into 336 groups, corresponding to +.>The value range is 0-335; each group contains 3 cell identities corresponding to +.>The value range is 0-2.

The types of cell search are classified into initial cell search (Initial Cell Search, ICS) and neighbor cell search (NeighboringCell Search, NCS).

Wherein, ICS is used for searching the system when the terminal is started, NR considers SS Raster with basic granularity of 1.2/1.44/17.28MHz and a synchronization signal Block (Synchronization Signal Block, SSB) with fixed bandwidth of 20 Resource Blocks (RB). Wherein, the SS Raster is a frequency point used for a series of sending SSB, each frequency point corresponds to a specific global synchronization number (Global Synchronization Channel Number, GSCN); SSB is composed of PSS, SSS and physical broadcast channel (Physical Broadcast Channel, PBCH). As shown in fig. 1, SSB occupies 4 orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) symbols in the time domain, wherein PSS and SSS each occupy 1 OFDM symbol, and PBCH occupies 2 symbols. The frequency domain occupies 20 RBs (240 RE), the PSS and SSS occupy 127 resource units (ResourceElement, RE), and the frequency domain duty cycle of the PBCH demodulation reference signal (Demodulation Reference Signal, DMRS) is 3RE/1RB.

The NCS is configured to periodically search and detect candidate neighboring cells to support mobility of the UE, where the candidate neighboring cells are any combination of co-channel, inter-channel, or inter-radio access technology (Radio Access Technology, RAT) cells, and the UE is always in a connected state.

The PSS of the 5G-NR is a physical layer specific signal that helps the UE to acquire a radio frame boundary. It is an m-sequence, a special type of linear feedback shift register (linear feedback shift register, LFSR) sequence, providing the longest non-repeating sequence.

NR-PSS has the following characteristics:

1) PSS is a Maximum-Length Sequence (m-Sequence) consisting of 127 values;

2) PSS maps to 127 active sub-carriers around the low end of the system bandwidth;

3) The PSS is used by the UE for downlink frame synchronization and provides the radio frame boundary, i.e. the position of the first symbol in the radio frame;

4) PSS is determining physical layer cell identityProvides +.>Value of->Carried by PSS.

The NR frequency domain PSS sequence is obtained by modulating m sequence with length of 127 through binary phase shift keying (Binary Phase Shift Keying, BPSK), namely:

wherein x is an m sequence with length of 127, m is more than or equal to 0 and less than or equal to 126, and u epsilon {0,1,2} represents a cell identifier

SSS of 5G-NR is a physical layer specific signal that helps UE to obtain subframe boundaries. It is similar to PSS, also an m-sequence.

NR-SSS has the following characteristics:

1) SSS is an m-sequence consisting of 127 values;

2) SSS maps to 127 active subcarriers around the low end of the system bandwidth;

3) SSS is used by the UE for downlink frame synchronization and provides a subframe boundary, i.e., the position of the first symbol in the subframe;

4) SSS is a determination of physical layer cell group number identificationKey factors of (2) and provide +.>Value of->Carried by SSS.

The NR frequency domain SSS sequence is obtained by BPSK modulation of a Gold sequence of length 127 (Gold sequence is formed by adding two m sequences of equal code length and same code clock rate, preferably by modulo 2), namely:

wherein x is ₀ And x ₁ Is two m sequences with length of 127, and m is more than or equal to 0 and less than or equal to 126,cell identity after detection for PSS>V e [0,335)]Identify +.>

Aiming at the problem that the existing cell searching method cannot cope with serious time-frequency offset, the embodiment of the application provides a cell searching method, a cell searching device and terminal equipment, frequency offset precompensation is realized through multi-scale cyclic shift, and the frequency offset tolerance of PSS detection is improved. Further, time bias offset is realized through multi-segment merging processing, and the time bias tolerance of SSS detection is improved.

As shown in fig. 2, a flowchart of a cell search method provided in an embodiment of the present application includes the following steps:

in step 201, a time domain signal is received.

The time domain signal is a non-ideal signal with time offset and frequency offsetCan be expressed as follows:

wherein p is an antenna port index, and u is a cell identifierr _u,p (m) is the ideal received signal in the time domain, t _TO Is time offset, f _FO Is frequency offset, f _s Is the sampling rate.

Step 202, obtaining PSS frequency domain sequences of different cell identifiers according to the received time domain signals.

For sampling rate f _s Let the subcarrier spacing size of SSB be f _SCS Converted into the frequency domainThe number of required fast fourier transforms (fast Fourier transform, FFT) isThen there are: />

For a sampling period T _s The default network searching duration is 20ms when ICS, considering that different SSB transmission patterns do not start from the 1 st orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) symbol, in case of no accurate timing, to ensure that the received data contains SSB, the duration of 2 to 4 OFDM symbols needs to be increased. The NCS time sampling period duration is determined by a window configured by SSB-based measurement timing configuration (SSB based Measurement Timing Configuration, SMTC), and may be 1ms, 2ms, 3ms, 4ms, 5ms, etc.

As shown in Table 1, table 1 shows the Frequency ranges of Frequency range 1 (Frequency range 1, FR 1) and Frequency range 2 (Frequency range 2, FR 2) in the embodiment of the present application, when the FFT points are counted256, sample rate and sample period instances for different SSB subcarrier configurations.

TABLE 1

Wherein, the subcarrier interval of the FR1 frequency band is 15KHz, 30KHz and 15/30KHz; the FR2 frequency band subcarrier spacing is 120KHz, 240KHz and 120/240KHz. Wherein: 15/30KHz represents a case where SSB subcarrier uncertainty, both 15KHz and 30KHz parameter sets are possible; 120/240KHz indicates that SSB subcarrier uncertainty, both 120KHz and 240KHz parameter sets may exist.

Corresponding subcarrier spacing f _SCS Sample rate f for 15KHz, 30KHz, 120KHz and 240KHz _s 3.84MHz, 7.68MHz, 30.72MHz and 61.44MHz, respectively. ICS and method for producing ICSThe sampling period at NCS is 20.067ms and 5ms, respectively. For the case that the SSB subcarrier size is uncertain, the configuration is carried out according to the highest sampling rate, namely 15/30KHz or 120/240KHz.

Step 203, performing multi-scale frequency offset pre-compensation on the PSS frequency domain sequence to obtain a plurality of different frequency offset compensation sequences.

Large carrier frequency offset (Carrier Frequency Offset, CFO) may result in degraded PSS detection performance, and for this reason, embodiments of the present application provide a multi-scale frequency offset precompensated PSS detection design, where the precompensated range is determined by the total CFO, including sweep error, voltage controlled oscillator (Voltage Controlled Oscillator, VCO) accuracy, doppler shift, and the like. Specifically, in a frequency band with a center frequency of 6GHz, the SSB subcarrier spacing is 15KHz, the frequency offset precision of a digital control crystal oscillator (Digital Controlled Crystal Oscillator, DCXO) can reach 20PPM in consideration of errors of 2 SS raders (granularity is 1.44 MHz), a high-speed railway scene has Doppler offset of up to 2KHz, the three can generate frequency offset of 3.002MHz by accumulation, which is equivalent to 200 SSB subcarrier spacing, and the frequency offset precompensation range is determined.

The frequency offset compensation modes in the time domain and the frequency domain can adopt a phase rotation mode and a cyclic shift mode respectively.

In order to reduce the implementation complexity of frequency offset precompensation, for example, frequency offset compensation can be performed in a frequency domain in a cyclic shift mode. Specifically, a first PSS frequency domain sequence with set bit number is generated according to the original PSS frequency domain sequenceThen +.>And performing cyclic shift to realize frequency offset precompensation.

Wherein the first PSS frequency domain sequenceThe construction method of (2) is as follows:

first, 127 bits of originalInitial PSS frequency domain sequenceZero filling to->Bits are processed by inverse fast fourier transform (Inverse Fast Fourier Transform, IFFT) to obtain a first time domain SSB signal;

then, the first time domain SSB signal is subjected to conjugate reverse order zero padding to obtain a first time domain SSB signalBits are processed by FFT to obtain a first frequency domain signal;

finally, N is carried out on the first frequency domain signal _OSR Double oversampling to obtainFirst PSS frequency domain sequence of bits +.>The formula is as follows:

wherein OSR represents over-sampling processing, FFT represents FFT operation, IFFT represents IFFT operation, N _OSR Is a multiple of the sampling rate,number of FFT processing points for SSB signal in first time domain,/-for>For FFT processing points used for PSS detection, conj is conjugate and flip is reverse order.

Maximum range F of frequency offset precompensation at this time ^Comp And minimum accuracy Δf are respectively as follows:

table 2 below shows that the FR1 and FR2 bands in the examples of the present application are at different N _OSR 、And f _SCS Under the condition of the maximum range F of frequency offset precompensation ^Comp And a minimum precision Δf instance, where F ^Comp In MHz and Δf in KHz.

TABLE 2

In Table 2, N _OSR Is 1,2 and 4,256, 512 and 1024->The value range is->Up to 4096.

When N is _OSR Is the number of the water-soluble polymer in the water solution of 4,256->In 4096, f _SCS At 15KHz, 30KHz, 120KHz and 240KHz, the corresponding precompensation maximum range F ^Comp 3.84MHz, 7.68MHz, 30.72MHz and 61.44MHz respectively, and the minimum accuracy Δf is 0.234375KHz, 0.46875KHz, 1.875KHz and 3.75KHz respectively.

Frequency offset compensation correspondence for minimum accuracy ΔfThe cyclic shift is 1 bit, and positive values are right shift and negative values are left shift.

In the embodiment of the application, the frequency offset precompensation is realized by adopting multistage and multi-scale cyclic shift, and if the required stage number is L, the frequency offset precision delta F of the first stage precompensation treatment is the same as that of the first stage precompensation treatment ^(l) And the number of cyclic shift points θ required ^(l) And a search step k ^(l) Can be expressed as:

specifically, the FR1 and FR2 bands of the present invention are in N _OSR Is 2,256 and +.>In 4096, the frequency offset precision DeltaF of each stage ^(l) And the number of cyclic shift points θ required ^(l) Search step k ^(l) Examples are shown in tables 3 and 4, respectively.

TABLE 3 Table 3

For the example in Table 3, frequency offset precompensation requires 4 stages of processing for SSB subcarrier sizes of 15KHz or 30 KHz. Wherein, the frequency offset precision DeltaF is at the 1 st level ^(l) The number of corresponding cyclic shift points theta is 240KHz or 480KHz ^(l) At 512, search step k ^(l) In the interval [ -16,16]The method comprises the steps of carrying out a first treatment on the surface of the Level 2, frequency offset accuracy ΔF ^(l) The number of corresponding cyclic shift points theta is 7.5KHz or 15KHz ^(l) For 16, search step k ^(l) In the interval [ -32,32]The method comprises the steps of carrying out a first treatment on the surface of the Level 3, frequency offset accuracy ΔF ^(l) 1.875KHz or 3.75KHzCorresponding cyclic shift point number theta ^(l) At 4, search step k ^(l) In interval [ -4,4]The method comprises the steps of carrying out a first treatment on the surface of the Level 4, frequency offset accuracy ΔF ^(l) The corresponding number of the cyclic shift points theta is 0.46875KHz or 0.9375KHz ^(l) At 4, search step k ^(l) In interval [ -4,4]。

TABLE 4 Table 4

For the example in Table 4, frequency offset precompensation requires 5 stages of processing for SSB subcarrier sizes of 120KHz or 240KHz. Wherein, the frequency offset precision DeltaF is at the 1 st level ^(l) The number of corresponding cyclic shift points theta is 7680KHz or 15360KHz ^(l) For 2048, search step k ^(l) In interval [ -4,4]The method comprises the steps of carrying out a first treatment on the surface of the Level 2, frequency offset accuracy ΔF ^(l) The corresponding cyclic shift point number theta is 960KHz or 1920KHz ^(l) 256, search step k ^(l) In the interval [ -8,8]The method comprises the steps of carrying out a first treatment on the surface of the Level 3, frequency offset accuracy ΔF ^(l) The number of corresponding cyclic shift points theta is 120KHz or 240KHz ^(l) For 32, search step k ^(l) In the interval [ -8,8]The method comprises the steps of carrying out a first treatment on the surface of the Level 4, frequency offset accuracy ΔF ^(l) The number of corresponding cyclic shift points theta is 15KHz or 30KHz ^(l) At 4, search step k ^(l) In the interval [ -8,8]The method comprises the steps of carrying out a first treatment on the surface of the Level 5, frequency offset accuracy ΔF ^(l) Is 3.75KHz or 7.5KHz, and corresponds to the number of the cyclic shift points theta ^(l) 1, search step k ^(l) In interval [ -4,4]。

Step 204, performing time domain sliding correlation on the received time domain signals and a plurality of different frequency offset compensation sequences of different cell identifications to perform PSS detection.

The PSS sequences of the invention for different cyclic shifts and different cell identificationsAnd receive signal->Making time domain sliding correlation, and marking as:

wherein,for frequency offset f _FO Estimate of->For cell identity +.>Estimate of->At t _TO N _Rx Port number for UE receive antenna, +.>Representing>And the shift point number is theta, for the frequency domain sequenceIn (2), θ represents positive shift right, θ represents negative shift left, and +.>Representing the time domain received signal converted to the frequency domain by FFT.

Due toIs a very long sequence, the sampling period is 20.067ms and the sampling rate is 7.68MHz, the data length reaches 153600 samples, so that the overlap preservation method can be adopted to process, namely, the original input sequence with a certain bit number at the front end of the segmented signal is preserved to prolong the signal sequence, and after the convolution is completed, the signal sequence is further processedThe error sequence of the bit number is discarded and added by the bit so as to lead the circumferential convolution result to be the same as the linear convolution result.

For example, when the SSB subcarrier spacing is 15KHz, the Signal-to-Noise Ratio (SNR) is-10 dB, and the TDL-A (Tapped Delay Line-A, tap delay line model A) is used for the channel, the PSS detection is carried out based on a time domain sliding correlation method of multi-scale frequency offset precompensation, N _OSR Is 1,256 and +.>4096, the correlation value distribution is shown in fig. 3. Wherein the frequency offset precompensation precision is 3.75KHz (corresponding to 4-point shift) and the step range is within the interval [ -32,32]I.e. frequency offset estimation->64 attempts were made; cell identity +.>The value range is {0,1,2}, i.e. the cell identity estimate +.>3 attempts were made, which corresponds to the "NID2 xFOE" axis in the figure, where NID2 corresponds to the cell identity +.>The FOE represents the precompensated frequency offset setting. The maximum range of the time-domain correlation Lag Lag is +.>I.e. 4096-256=3840 points, immediate bias estimation +.>3840 attempts were made, corresponding to the "Lag" axis in the graph. It can be seen that the peak passing through can be in the range of "NID2 XFOE XLagValue search, can confirm the joint estimation of frequency offset, time offset and cell identification +.>

According to the cell searching method, frequency offset precompensation is achieved through multi-scale cyclic shift, frequency offsets with different ranges and different precision can be processed, and therefore frequency offset tolerance of PSS detection is effectively improved. And the PSS frequency offset pre-compensation is realized through multi-scale cyclic shift, and the realization complexity is low. In addition, the maximum range and minimum precision of frequency offset precompensation during PSS detection and the searching step length and step number can be freely configured, so that the flexibility of the scheme is improved.

Further, in another non-limiting embodiment of the cell search of the present application, SSS detection may also be performed by frequency domain linear correlation based on multi-segment combining. The method specifically comprises the following steps:

1) Frequency domain data compensation processing

For time domain received signalsFrequency offset compensation processing is carried out, and the frequency offset compensation processing is converted into a frequency domain receiving signal y _p (m) noted as:

where p denotes an antenna port index of the UE,frequency offset estimation for PSS detection, f _s Is the sampling rate.

The frequency offset compensation process is an operation of compensation process based on the frequency offset estimation result, and specifically, the prior art can be adopted.

2) Multi-segment combined frequency domain linear correlation

Taking into account residual time bias affects cell group identityThe embodiment of the application provides an SSS detection design based on frequency domain linear correlation of multi-segment merging processing, and reduces the influence of residual time bias on SSS detection. Specifically, frequency domain linear correlation is respectively carried out on the frequency domain received signal and the segmented data of the local SSS sequence, and SSS detection is carried out according to the average result of multiple segmented correlation combination. In addition, in performing SSS detection of multiple segments, if the total sequence length required for the segments exceeds the length of the frequency domain received signal, the length of the frequency domain received signal may be made to reach the total sequence length by supplementing 0.

Specifically, the frequency domain linear correlation computation of the multi-segment data can be written as:

in the method, in the process of the invention,identify +.>N _Rx For the number of UE antenna ports, N _Sec For the number of segments, L _Sec Is the length of the segment and has +.>

Due to L _Sec The computation of (1) has an operation of taking the integer, resulting in L _Sec N _Sec 127. Gtoreq., therefore, sequenceAnd y _p (m+lL _Sec ) Samples with lengths exceeding 127 can be achieved by zero padding.

In addition, the number of segments N is increased _Sec The sensitivity of residual time bias in SSS detection can be reduced.

As shown in FIG. 4, a diagram4 is the cell group identification when SSB subcarrier spacing is 15KHz, SNR is-5 dB, TDL-A channelFor 147, frequency domain linear correlation SSS detection by multi-segment combining process, different cell group identity +.>And different number of segments N _Sec Is a graph of correlation values.

The "NID1" axis in fig. 4 corresponds to different cell group identifications

As can be seen from fig. 4, the correlation value at NID1 is 147, which is significantly higher than the correlation value on both sides. In addition, it can be found that N _Sec When smaller, such as 1 or 2, the correlation peak is not at NID1 at 147, false detection may occur.

As shown in FIG. 5, FIG. 5 shows that the SSB subcarrier spacing is 15KHz and the SNR range is [ -15,0]dB, TDL-A channel, different segmentation numbers N _Sec The following SSS detection probability diagram.

In fig. 5 the horizontal axis represents the signal-to-noise ratio SNR and the vertical axis represents the Prob function, i.e. the function of the corresponding probability that the value falls within the specified interval.

As can be seen from fig. 5, N _Sec At 6, SSS detection performance is best. At a detection probability of 90%, the required SNR is-6 dB.

According to the cell searching method provided by the embodiment of the application, the time bias offset is realized through multi-segment merging processing, and the time bias tolerance of SSS detection is improved. Furthermore, the number of segments processed by the segmentation process of the SSS detection can be freely configured, and can be flexibly configured according to the requirement.

Correspondingly, the embodiment of the application also provides a cell searching device, as shown in fig. 6, which is a schematic structural diagram of the device.

The cell search apparatus 600 includes the following modules:

a receiving module 601, configured to receive a time domain signal;

the PSS frequency domain sequence acquiring module 602 is configured to acquire PSS frequency domain sequences of different cell identifiers according to the received time domain signal;

the pre-compensation module 603 is configured to perform multi-scale frequency offset pre-compensation on the PSS frequency domain sequence, so as to obtain a plurality of different frequency offset compensation sequences;

the PSS detection module 604 is configured to perform time domain sliding correlation on the received time domain signal and a plurality of different frequency offset compensation sequences of different cell identities, so as to perform PSS detection.

Fig. 7 is a schematic diagram of another structure of the cell search apparatus according to the present application.

The difference from the embodiment shown in fig. 6 is that in this embodiment, the cell search apparatus 700 further includes:

the compensation processing module 701 is configured to perform frequency offset compensation processing on the received time domain signal, and convert the received time domain signal into a frequency domain received signal;

the SSS detection module 702 is configured to perform multi-segment combining on the frequency domain received signal to perform SSS detection.

Other relevant descriptions about the cell search apparatus 600 may refer to those in the foregoing embodiments, and are not repeated here.

Correspondingly, the embodiment of the application also provides terminal equipment, which comprises the cell searching device. The terminal device may be, but is not limited to: the mobile phone, the tablet personal computer, the POS machine, the intelligent watch and the like can better meet the design requirements of the terminal products on low power consumption.

With respect to each of the apparatuses and each of the modules/units included in the products described in the above embodiments, it may be a software module/unit, a hardware module/unit, or a software module/unit, and a hardware module/unit. For example, for each device or product applied to or integrated on a chip, each module/unit included in the device or product may be implemented in hardware such as a circuit, or at least part of the modules/units may be implemented in software program, where the software program runs on a processor integrated inside the chip, and the rest (if any) of the modules/units may be implemented in hardware such as a circuit; for each device and product applied to or integrated in the chip module, each module/unit contained in the device and product can be realized in a hardware manner such as a circuit, different modules/units can be located in the same component (such as a chip, a circuit module and the like) or different components of the chip module, or at least part of the modules/units can be realized in a software program, the software program runs on a processor integrated in the chip module, and the rest (if any) of the modules/units can be realized in a hardware manner such as a circuit; for each device, product, or application to or integrated with the terminal, each module/unit included in the device, product, or application may be implemented by using hardware such as a circuit, different modules/units may be located in the same component (for example, a chip, a circuit module, or the like) or different components in the terminal, or at least part of the modules/units may be implemented by using a software program, where the software program runs on a processor integrated inside the terminal, and the remaining (if any) part of the modules/units may be implemented by using hardware such as a circuit.

The embodiment of the application also discloses a storage medium, which is a computer readable storage medium, and a computer program is stored on the storage medium, and the computer program can execute the steps of the method shown in fig. 2 when running. The storage medium may include Read-Only Memory (ROM), random access Memory (Random Access Memory, RAM), magnetic or optical disks, and the like. The storage medium may also include non-volatile memory (non-volatile) or non-transitory memory (non-transitory) or the like.

Referring to fig. 8, the embodiment of the application further provides a hardware structure schematic diagram of the terminal device. The apparatus includes a processor 801, a memory 802, and a transceiver 803.

The processor 801 may be a general purpose central processing unit (central processing unit, CPU), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of programs in accordance with aspects of the present application. The processor 801 may also include multiple CPUs, and the processor 801 may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, or processing cores for processing data (e.g., computer program instructions).

The memory 802 may be a ROM or other type of static storage device, a RAM or other type of dynamic storage device that can store static information and instructions, or that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disk read-only memory (CD-ROM) or other optical disk storage, optical disk storage (including compact disk, laser disk, optical disk, digital versatile disk, blu-ray disk, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, as described herein. The memory 802 may exist alone (in which case the memory 802 may be located outside or within the device) or may be integrated with the processor 801. Wherein the memory 802 may contain computer program code. The processor 801 is configured to execute computer program code stored in the memory 802, thereby implementing the methods provided in the embodiments of the present application.

The processor 801, the memory 802, and the transceiver 803 are connected by a bus. The transceiver 803 is used to communicate with other devices or communication networks. Alternatively, the transceiver 803 may include a transmitter and a receiver. The means for implementing the receiving function in the transceiver 803 may be regarded as a receiver for performing the steps of receiving in the embodiments of the present application. The means for implementing the transmitting function in the transceiver 803 may be regarded as a transmitter for performing the steps of transmitting in the embodiments of the present application.

While the schematic structural diagram shown in fig. 8 is used to illustrate the structure of the terminal device according to the above embodiment, the processor 801 is configured to control and manage the actions of the terminal device, for example, the processor 801 is configured to support the terminal device to perform the steps of the foregoing method, and/or the actions performed by the terminal device in other processes described in the embodiments of the present application. The processor 801 may communicate with other network entities through the transceiver 803. The memory 802 is used to store program codes and data for the terminal device.

It should be understood that the term "and/or" is merely an association relationship describing the associated object, and means that three relationships may exist, for example, a and/or B may mean: a exists alone, A and B exist together, and B exists alone. In this context, the character "/" indicates that the front and rear associated objects are an "or" relationship.

The term "plurality" as used in the embodiments herein refers to two or more.

The first, second, etc. descriptions in the embodiments of the present application are only used for illustrating and distinguishing the description objects, and no order division is used, nor does it indicate that the number of the devices in the embodiments of the present application is particularly limited, and no limitation on the embodiments of the present application should be construed.

The "connection" in the embodiments of the present application refers to various connection manners such as direct connection or indirect connection, so as to implement communication between devices, which is not limited in any way in the embodiments of the present application.

The above embodiments may be implemented in whole or in part by software, hardware, firmware, or any other combination. When implemented in software, the above-described embodiments may be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, the processes or functions described in accordance with the embodiments of the present application are all or partially produced. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center by wired or wireless means.

It should be understood that, in various embodiments of the present application, the sequence numbers of the foregoing processes do not mean the order of execution, and the order of execution of the processes should be determined by the functions and internal logic thereof, and should not constitute any limitation on the implementation process of the embodiments of the present application.

In the several embodiments provided in the present application, it should be understood that the disclosed method, apparatus, and system may be implemented in other manners. For example, the device embodiments described above are merely illustrative; for example, the division of the units is only one logic function division, and other division modes can be adopted in actual implementation; for example, multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may be physically included separately, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in hardware plus software functional units.

The integrated units implemented in the form of software functional units described above may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium, and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform part of the steps of the methods described in the embodiments of the present application.

Although the present application is disclosed above, the present application is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention shall be defined by the appended claims.

Claims

1. A method of cell search, the method comprising:

receiving a time domain signal;

2. The method of claim 1, wherein the time domain signal is a non-ideal signal with a time offset and a frequency offset.

3. The method of claim 1, wherein the range of the multi-scale frequency offset precompensation is determined based on a total carrier frequency offset.

4. The method of claim 1, wherein the multi-scale frequency offset precompensation of the PSS frequency domain sequence comprises:

5. The method of claim 4, wherein the PSS frequency-domain sequence is a 127-bit original PSS frequency-domain sequence;

and performing cyclic shift on the first PSS frequency domain sequence.

6. The method of claim 5, wherein generating the first PSS frequency-domain sequence of a set number of bits from the original PSS frequency-domain sequence comprises:

7. The method according to any one of claims 1 to 6, further comprising:

8. The method of claim 7, wherein the method further comprises:

in the case of multi-segment SSS detection, if the total sequence length required by the segments exceeds the length of the frequency domain received signal, the length of the frequency domain received signal is made to reach the total sequence length by supplementing 0.

9. A cell search apparatus, the apparatus comprising:

a receiving module for receiving the time domain signal;

10. The apparatus of claim 9, wherein the apparatus further comprises:

11. A terminal device, characterized in that the terminal device comprises a cell search apparatus according to claim 9 or 10.

12. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, performs the steps of the cell search method of any of claims 1 to 8.

13. A terminal device comprising a memory and a processor, the memory having stored thereon a computer program executable on the processor, characterized in that the processor executes the steps of the cell search method according to any of claims 1 to 8 when the computer program is executed by the processor.