CN106603189A - Method for eliminating interference of cell search in LTE system - Google Patents
Method for eliminating interference of cell search in LTE system Download PDFInfo
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- CN106603189A CN106603189A CN201611078252.1A CN201611078252A CN106603189A CN 106603189 A CN106603189 A CN 106603189A CN 201611078252 A CN201611078252 A CN 201611078252A CN 106603189 A CN106603189 A CN 106603189A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0069—Cell search, i.e. determining cell identity [cell-ID]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0069—Cell search, i.e. determining cell identity [cell-ID]
- H04J11/0073—Acquisition of primary synchronisation channel, e.g. detection of cell-ID within cell-ID group
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
Abstract
The invention discloses a method for eliminating interference of cell search in a LTE system. The method comprises the following steps of performing correlation operation on three groups of local PSS sequences and a received signal to obtain three groups of PSS correlation values; and for each group of PSS correlation values, searching first PSS correlation peak values arranged in an ascending order in the PSS correlation values by using a first threshold, and saving the PSS correlation peak value positions and a cell ID inter-group identifier; from the maximum PSS correlation peak value position, performing SSS correlation detection on the received signal for each PSS correlation peak value position, and successively detecting the PSS correlation peak values according to a descending order by using a second threshold, and after each correlation detection, reconfiguring a SSS signal at the maximum SSS correlation peak value in order to subtract the SSS signal from the corresponding position received signal to achieve SSS interference cancellation. The method can search relatively strong and weak cells at the same time, improves the downlink synchronization performance and handoff performance of the UE, and improves the user experience.
Description
Technical field
The present invention relates to LTE (Long Term Evolution, Long Term Evolution project) systems technology field, more particularly to
Cell searching interference elimination method in a kind of LTE system.
Background technology
LTE is referred to as 3.9G by popular, and the data download capabilities with 100Mbps are considered the master from 3G to 4G evolution
Flow Technique.It improves and enhances the aerial access technology of 3G, using OFDM and MIMO as the unique of its wireless network evolution
Standard.If UE (equipment) in LTE system will be communicated by LTE cellular networks, need to carry out cell searching to detect
To the physical-layer cell identifier of cell.Due to each cell and a pair of master sync signals (PSS) and auxiliary synchronous signal (SSS) phase
It is mutually corresponding, therefore during cell searching, UE can detect that the physical-layer cell identifier of cell (i.e. by detecting PSS and SSS
Cell ID).Detection physical-layer cell identifier is related to obtain cell ID group mark from the SSS sequences by base station broadcastAnd obtain cell ID group mark from the PSS sequences by base station broadcastCell ID group
Interior markFrom PSS Sequence Detections to cell ID group in markAfterwards from SSS sequences
Detection cell ID group markDetecting cell ID group markWith mark in cell ID groupAfterwards, can make
WithRelation determining physical-layer cell identifier, wherein NIDIt is physical-layer cell identifier,
That is cell ID, because there are 168 unique Cell ID groups in each group identifyingWith mark in three unique Cell ID groupsSo there is 504 unique physical layer marks altogether in LTE cellular networks.
In complete cell search process, it usually needs successively determine multiple candidate cells, be first detected
Cell is typically the most strong cell of signal, if the signal in this group of mean people area is not eliminated, will produce shadow to the detection of subsequent cell
Ring, for this purpose, in actual application, often taking measures to carry out interference elimination, Ran Houzai after a cell is determined every time
Carry out the detection of next cell.
Generally the PSS of the searched cell for arriving is eliminated using Reconstruction Method in prior art, so as to realize cell searching mistake
Interference in journey is eliminated；Because LTE network has identical networking, therefore can there is the co-channel interference between neighbor cell.Due to
Whole network only has three PSS, therefore adjacent two cell may use same PSS, then in two using same PSS
When the downlink synchronous signal of cell reaches UE simultaneously substantially, carrying out interference elimination using Reconstruction Method can cause the PSS of two cells same
When be eliminated, so as to cause that relatively strong cell can only be searched, and relatively weak cell searched can not be arrived, therefore
PSS detection-phases carry out interference elimination using Reconstruction Method can cause the cell searched under some scenes incomplete.For relatively
Weak cell, carries out PSS interference and eliminates and can cause the PSS can not be by greatest extent because channel estimation value is forbidden using Reconstruction Method
Elimination, while can also introduce larger interference, cause weaker cell to be detected.
Because SSS has 504, neighbor cell can not possibly use same cell ID (mark), therefore neighbor cell to be used
SSS be different, along with adjacent two cell using same PSS, when SSS is generated, the scrambler that uses is identical, therefore phase
Interference between adjacent two cells can become strong, and carrying out that SSS interference eliminations are not enough to eliminate to greatest extent using zero setting method merely ought
Interference under front scene between two cells.
The content of the invention
It is an object of the invention to overcome the shortcoming and deficiency of prior art, there is provided cell searching is done in a kind of LTE system
The method for disturbing elimination, the method is reached simultaneously for the downlink synchronous signal of the homogeneous frequency adjacent area using same PSS signals
The situation of UE, both may search for the relatively strong cell of signal, it is also possible to searches the relatively weak cell of signal, overcomes little
The infull technical problem of area searching, it is possible to increase the performance of UE down-going synchronous and the performance of handover, so as to improve user's body
Test.
The purpose of the present invention is achieved through the following technical solutions：Cell searching interference elimination method in a kind of LTE system,
Step is as follows：
S1, acquisition receive signal；
S2, three groups of local PSS sequences are gone to into respectively time domain from frequency domain, then respectively with receive signal and carry out in step S1
Three groups of PSS correlations are obtained after related operation；
S3, for each group of PSS correlation, will be in PSS correlations by relation ranking from big to small by the first thresholding
Search out to come in former PSS correlation peaks, until search is arrived less than the PSS correlation peaks or current search for crossing the first thresholding
PSS correlation peaks reach certain number X, then terminate search, preserve each PSS relevant peaks searched above by the first thresholding
Mark in value position and cell ID group；
S4, each PSS correlation peak locations for getting in each group of PSS correlation in step S3, from maximum
PSS correlation peak locations start, and with PSS correlation peaks order from big to small, for each PSS correlation peak location, enter
The following operation of row：
S41, first according to current PSS correlation peak locations, docking is collected mail and number carries out SSS coherent detections, obtains SSS related
Value, then searched for the SSS correlation peaks of the second thresholding by the second thresholding, and therefrom got a SSS phase of maximum
Close peak value；Into step S42；
S42, SSS interference is eliminated：By the maximum corresponding SSS signal reconstructions of SSS correlation peaks out, then will reconstruct
The SSS signals for coming cut from the reception signal of correspondence position, obtain disturbing the signal after eliminating；Subsequently into step S43；
S43, according to current PSS correlation peak locations, for step S42 disturbs the reception signal after eliminating to carry out SSS again
Coherent detection, obtains SSS correlations, and the SSS correlation peaks of the second thresholding were then searched for by the second thresholding, determines whether
Cross the SSS correlation peaks of the second thresholding；
If so, a SSS correlation peak of maximum is then selected from the SSS correlation peaks for crossing the second thresholding；Then sentence
Whether the number of the maximum SSS correlation peaks that the thresholding of open close mistake second has been chosen altogether reaches certain number Y, if it is not,
Step S42 is then entered, step S44 is if so, then entered；
If it is not, then entering step S44；
Under S44, current PSS correlation peak locations, SSS interference eliminations are completed, for next PSS correlation peak locations,
Return to step S41.
Preferably, three groups of local PSS sequences go to respectively comprising the following steps that for time domain from frequency domain in step S2：
S21, according in the cell ID group of PSS sequences identifyValue 0,1 and 2, get three groups of local frequency domain PSS
Sequence, wherein the length of local frequency domain PSS sequences is 62；
S22, per group of local frequency domain PSS sequence is both mapped to before and after direct current subcarrier on each 31 subcarriers；
S23, every group of signal for getting in step S22, supplemented 33 before local frequency domain PSS sequence subcarriers
Zero, 32 zero are supplemented afterwards, removing after frequency is processed carries out 128 point, inverse fast Fourier transforms, finally gives three groups of local time domains
PSS sequences.
Preferably, each group PSS correlation is got by following steps in step S2：
S24, receive signal in get starting point P0, then start to take 256 sampled points from starting point P0, then to it
256 points of FFT is done, the first frequency-region signal is obtained；It is the letter wherein to receive first starting point P0 got in signal
Number the first sampled point.
S25,128 sampled points are taken from one group of local time domain PSS sequence, zero padding is to 256 sampled points and is 256 points of FFT
Conversion, obtains the second frequency-region signal；
S26, the first frequency-region signal and the second frequency-region signal conjugate multiplication are obtained into the 3rd signal, then enter the 3rd signal
The IFFT that 256 points of row obtains time-domain signal；
S27, front 128 sampled points for taking the time-domain signal that step S26 gets, as one group local time domain PSS sequence with
Receive the correlation after signal 128 related operations of slip；
S28, judge to receive and whether carry out related calculation and obtain correlation at signal ending, if so, then this group of related operation knot
Beam；If it is not, then adding starting point P0 return to step S24 after 128 sampled points.
Preferably, each group of PSS correlation is directed in step S3, by the first thresholding by PSS correlations according to from big
To little relation ranking former PSS correlation peaks with sequential search from big to small out, detailed process is as follows：
S31, for each group of PSS correlation, the first thresholding is set first；
S32, the PSS correlation peaks that the first thresholding was searched for by the first thresholding, determined whether the PSS of the first thresholding
Correlation peak；
If so, a PSS correlation peak of maximum is then selected from the PSS correlation peaks for crossing the first thresholding, is then sentenced
The number of the disconnected current maximum PSS correlation peaks chosen altogether by the first thresholding reaches certain number X, if so,
Then enter step S34；If it is not, then entering step S33；
If it is not, then entering step S34；
S33, by the maximum PSS correlation peak locations got in step S32 and its it is adjacent before and after each some positions
The correlation zero setting put；It is then return to step S32；
S34, the search by the first thresholding for PSS correlation peaks terminate.
Further, the threshold value of first thresholding is that 9000, X values are 5.
Preferably, the process of SSS coherent detections is carried out such as according to current PSS correlation peak locations in step S41 and S43
Under：
S411, using current PSS correlation peak locations as PSS timing positions, with reference to the various relative positions of PSS and SSS
Relation, determines each timing position of SSS；
S412,128 point SSS time-domain signals are taken respectively in each timing position of SSS, then by 128 point SSS time-domain signals
128 FFTs are carried out, 128 sampled point frequency-region signals are obtained；
The corresponding data of label 65 in S413,128 sampled point frequency domain sequences are direct current subcarrier, before direct current subcarrier
31 frequency domain sequences are respectively extracted afterwards, and the frequency domain sequence for constituting at 62 points is SSS frequency-region signals；
S414, according to the generating mode of SSS, progressively descramble and the correlation using m-sequence carry out related calculation, obtain SSS
Correlation peak, and therefrom get SSS maximum correlation peaks；
S415, according to SSS maximum correlation peaks, carry out duplex mode, CP types, cell ID group mark and field in front and back
Judgement, is so far obtained with cell ID and frame timing.
Further, the relative position relation of PSS and SSS includes four kinds, wherein TDD (time division duplex) and Normal
Under CP (general cyclic prefix) relative position relation, PSS and SSS relative positions are 412 sampled points；TDD and Extended CP
Under (extended cyclic prefix) relative position relation, PSS and SSS relative positions are 480 sampled points；FDD (FDD) and
Under Normal CP relative position relations, PSS and SSS relative positions are 137 sampled points；FDD and Extended CP are with respect to position
It is 160 under PSS and SSS relative position relations under putting relation.
Further, by the corresponding SSS signal reconstructions of SSS maximum correlation peaks out concrete in step S42
Process is as follows：
S421, according in step S415 determine cell ID and frame timing, generate SSS frequency-region signals；
S422, extract in signal the corresponding SSS signals of SSS maximum correlation peaks from receiving；
The SSS signals obtained in S423, SSS frequency-region signals and step S422 for generation in step S421 carry out minimum
Two take advantage of channel estimation, and carry out time domain noise reduction process to channel estimation value sequence；
Channel estimation value sequence after S444, the time domain noise reduction for getting step S423 process is multiplied by step S421
SSS frequency-region signals, the sequence for obtaining is and reconstructs the SSS frequency-region signals for coming；
S445, step S444 is reconstructed the SSS frequency-region signals for coming go in time domain, and plus prefix, that is, reconstructed
Whole SSS time-domain signals.
Preferably, the threshold value of the second thresholding is 200 in step S4；Y is 2.
Preferably, the signal that receives for obtaining in step S1 is filtering and the reception signal after down-sampled process.
The present invention has the following advantages and effect relative to prior art：
(1) the inventive method carries out related operation with reception signal respectively first by three groups of local PSS sequences, so as to obtain
Get three groups of PSS correlations, for each group of PSS correlation, and by the first thresholding search for PSS correlations in press from greatly to
Little relation ranking preserves mark in these PSS correlation peak locations and cell ID group in former PSS correlation peaks；Connect
Get off for these PSS correlation peak locations for preserving, from the beginning of the position of maximum PSS correlation peaks, for each PSS
Correlation peak location, collecting mail in corresponding with PSS correlation peak locations position docking number carries out SSS coherent detections, by the
The search of two thresholdings successively detects SSS correlation peaks according to order from big to small, and every time after SSS coherent detections,
By the SSS signal reconstructions at SSS correlation peaks out, reception signal of the next SSS signals from correspondence position will then be reconstructed
In cut, realize SSS interference eliminate.As can be seen here, it is little for the homogeneous frequency adjacent of the same PSS signals used in LTE system
The downlink synchronous signal in area reaches the situation of UE simultaneously, by the inventive method in cell searching, both may search for frequency
The strong cell of signal in neighbor cell, it is also possible to search the weak cell of signal in homogeneous frequency adjacent area, therefore the inventive method
Ensure that the complete of cell searching, effectively prevent Reconstruction Method used in prior art carry out PSS interference elimination cause to search
Rope is to the relatively strong cell of signal, and the phenomenon that the relatively weak cell of signal searched can not be arrived.Under greatly improving UE
The performance of the synchronous performance of row and handover, so as to improve Consumer's Experience.And Reconstruction Method is adopted in the inventive method by SSS
Eliminated, can to greatest extent be eliminated the interference used under current scene between adjacent two cells of same PSS.
(2) the inventive method by the first thresholding by PSS correlations by relation ranking from big to small in former PSS
Correlation peak is searched out when coming, and wherein these PSS correlation peaks are arrived so that order from big to small is searched successively, are being searched for every time
When, a PSS correlation peak maximum in the PSS correlation peaks of thresholding was chosen, and get the PSS correlation peaks position
Put, then the correlation of the PSS correlation peak locations and its adjacent each some positions in front and back is carried out into zero setting；Due to search every time
When, current maximum PSS correlation peaks are set to zero, therefore when searching for next time, the PSS correlation peaks for searching will be second to this
Maximum PSS correlation peaks, therefore the present invention effectively eliminates PSS strong correlations peak to the weak relevant peaks of PSS by way of zero setting
Interference, reach the purpose that interference is eliminated, can to greatest extent eliminate the interference of PSS, determine potential effectively relevant peaks
Mark in value position and cell ID group, effectively reduces the complexity that PSS interference is eliminated, and improves the efficiency that PSS interference is eliminated.
And the present invention is in zeroing process, before and after current maximum PSS correlation peaks the correlation of adjacent each some positions also by
Zero is set to, therefore the inventive method can simultaneously avoid the PSS correlation peak front and back position correlations of current maximum to next time
The interference that PSS correlation peaks are produced when searching for, eliminates to greatest extent interference of the PSS strong correlations peak to the weak relevant peaks of PSS.This
Inventive method effectively prevent in prior art for relatively weak cell, and carrying out that PSS interference eliminates using Reconstruction Method can be because
It is inaccurate for channel estimation value, cause PSS to be eliminated to greatest extent, while can also introduce larger interference, cause weaker
The technical problem that can not be detected of cell.
(3) signal is received in the inventive method to be first filtered and dropped before related operation is carried out with local PSS sequences
Sampling processing, wherein the signal beyond by filtering PSS and SSS bandwidth, improves the performance of cell searching, by down-sampled
The amount of calculation of related operation is reduced, cell searching efficiency is improved.
Description of the drawings
Fig. 1 is the inventive method flow chart.
Specific embodiment
With reference to embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited
In this.
Embodiment
Present embodiment discloses cell searching interference elimination method in a kind of LTE system, as shown in figure 1, step is as follows：
S1, acquisition receive signal；The signal that receives obtained in the present embodiment is filtering and the letter of the reception after down-sampled process
Number, wherein docking is collected mail, a number sample rate for the wave filter for being filtered process is 30.72MHz, and pass band width is 472.5KHz, resistance
Band initial frequency is 547.5KHz, and attenuation outside a channel is 20dB, and passband fluctuation is 0.1dB；Adopt during down-sampled process in step S1
Be 16 times.
S2, three groups of local PSS sequences are gone to into respectively time domain from frequency domain, then respectively with receive signal and carry out in step S1
Three groups of PSS correlations are obtained after related operation.
Three groups of local PSS sequences go to respectively comprising the following steps that for time domain from frequency domain in this step S2：
S21, according in the cell ID group of PSS sequences identifyValue 0,1 and 2, get three groups of local frequency domain PSS
Sequence, wherein the length of local frequency domain PSS sequences is 62；
S22, per group of local frequency domain PSS sequence is both mapped to before and after direct current subcarrier on each 31 subcarriers；
S23, every group of signal for getting in step S22, supplemented 33 before local frequency domain PSS sequence subcarriers
Zero, 32 zero are supplemented afterwards, removing after frequency is processed carries out 128 point IFFT conversion (fast fourier inverse transformation), finally gives three
The local time domain PSS sequence of group.
Each group PSS correlation is got by following steps in this step：
S24, receive signal in get starting point P0, then start to take 256 sampled points from starting point P0, then to it
256 points of FFT (FFT) is done, the first frequency-region signal S1 is obtained；Wherein receive the got in signal
One starting point P0 is the first sampled point of the signal.
S25,128 sampled points are taken from one group of local time domain PSS sequence, zero padding is to 256 sampled points and is 256 points of FFT
Conversion, obtains the second frequency-region signal S2；
S26, the first frequency-region signal S1 and the second frequency-region signal S2 conjugate multiplications are obtained into the 3rd signal S3, then by the 3rd
Signal S3 carries out 256 points of IFFT and obtains time-domain signal S4；
S27, front 128 sampled point for taking time-domain signal S4, as one group local time domain PSS sequence is slided with signal is received
Correlation after 128 related operations；
S28, judge to receive and whether carry out related calculation and obtain correlation at signal ending, if so, then this group of related operation knot
Beam；If it is not, then adding starting point P0 return to step S24 after 128 sampled points.
S3, for each group of PSS correlation, will be in PSS correlations by relation ranking from big to small by the first thresholding
Search out to come in former PSS correlation peaks, until search is arrived less than the PSS correlation peaks or current search for crossing the first thresholding
PSS correlation peaks reach certain number X, then terminate search, preserve each PSS relevant peaks searched above by the first thresholding
Mark in value position and cell ID group；The threshold value of the first thresholding is that 9000, X values are 5 in the present embodiment.
In step S3 be directed to each group of PSS correlation, by the first thresholding by PSS correlations according to pass from big to small
Be ranking former PSS correlation peaks with sequential search from big to small out, detailed process is as follows：
S31, for each group of PSS correlation, the first thresholding is set first；
S32, the PSS correlation peaks that the first thresholding was searched for by the first thresholding, determined whether the PSS of the first thresholding
Correlation peak；
If so, a PSS correlation peak of maximum is then selected from the PSS correlation peaks for crossing the first thresholding, is then sentenced
The number of the disconnected current maximum PSS correlation peaks chosen altogether by the first thresholding reaches certain number X, if so,
Then enter step S34；If it is not, then entering step S33；
If it is not, then entering step S34；
S33, by the maximum PSS correlation peak locations got in step S32 and its it is adjacent before and after each some positions
The correlation zero setting put；It is then return to step S32；To get most in step S32 in this step wherein in the present embodiment
The correlation zero setting of a big PSS correlation peak location and its adjacent each position in front and back；
S34, the search by the first thresholding for PSS correlation peaks terminate.
By above-mentioned steps can by PSS correlations according to relation ranking from big to small in former PSS relevant peaks
It is worth with sequential search from big to small out, so as to get correspondence PSS correlation peak locations.
S4, each PSS correlation peak locations for getting in each group of PSS correlation in step S3, from maximum
PSS correlation peak locations start, and for each PSS correlation peak location, proceed as follows：
S41, first according to current PSS correlation peak locations, docking is collected mail and number carries out SSS coherent detections, obtains SSS related
Value, then searched for the SSS correlation peaks of the second thresholding by the second thresholding, and therefrom got a SSS phase of maximum
Close peak value；Into step S42；The threshold value of the second thresholding is 200 in the present embodiment.
S42, SSS interference is eliminated：By the maximum corresponding SSS signal reconstructions of SSS correlation peaks out, then will reconstruct
The SSS signals for coming cut from the reception signal of correspondence position, obtain disturbing the signal after eliminating；Subsequently into step S43；
S43, according to current PSS correlation peak locations, for step S42 disturbs the reception signal after eliminating to carry out SSS again
Coherent detection, obtains SSS correlations, and the SSS correlation peaks of the second thresholding were then searched for by the second thresholding, determines whether
Cross the SSS correlation peaks of the second thresholding；
If so, a SSS correlation peak of maximum is then selected from the SSS correlation peaks for crossing the second thresholding；Then sentence
Whether the number of the maximum SSS correlation peaks that the thresholding of open close mistake second has been chosen altogether reaches certain number Y, if it is not,
Step S42 is then entered, step S44 is if so, then entered；
If it is not, then entering step S44；
Under S44, current PSS correlation peak locations, SSS interference eliminations are completed, for next PSS correlation peak locations,
Return to step S41.
In the present embodiment, according to current PSS correlation peak locations in step S41 and S43, the mistake of SSS coherent detections is carried out
Journey is as follows：
S411, using current PSS correlation peak locations as PSS timing positions, with reference to the various relative positions of PSS and SSS
Relation, determines each timing position of SSS；The relative position relation of wherein PSS and SSS includes four kinds, wherein TDD (time-divisions
Duplex) and Normal CP (general cyclic prefix) relative position relation under, PSS and SSS relative positions be 412 sampled points；
Under TDD and Extended CP (extended cyclic prefix) relative position relation, PSS and SSS relative positions are 480 sampled points；
Under FDD (FDD) and Normal CP relative position relations, PSS and SSS relative positions are 137 sampled points；FDD and
It is 160 under PSS and SSS relative position relations under Extended CP relative position relations.
S412,128 point SSS time-domain signals are taken respectively in each timing position of SSS, then by 128 point SSS time-domain signals
128 FFTs are carried out, 128 frequency-region signals are obtained；
The corresponding data of label 65 in S413,128 sampled point frequency domain sequences are direct current subcarrier, before direct current subcarrier
31 frequency domain sequences are respectively extracted afterwards, and the frequency domain sequence for constituting at 62 points is SSS frequency-region signals；
S414, according to the generating mode of SSS, progressively descramble and the correlation using m-sequence carry out related calculation, obtain SSS
Correlation peak, and therefrom get SSS maximum correlation peaks；
S415, according to SSS maximum correlation peaks, carry out duplex mode, CP types, cell ID group mark and field in front and back
Judgement, is so far obtained with cell ID and frame timing.
In the present embodiment step S42 by the corresponding SSS signal reconstructions of SSS maximum correlation peaks detailed process out such as
Under：
S421, according in step S415 determine cell ID and frame timing, generate SSS frequency-region signals；
S422, extract in signal the corresponding SSS signals of SSS maximum correlation peaks from receiving；
The SSS signals obtained in S423, SSS frequency-region signals and step S422 for generation in step S421 carry out minimum
Two take advantage of channel estimation, and carry out time domain noise reduction process to channel estimation value sequence；
Channel estimation value sequence after S444, the time domain noise reduction for getting step S423 process is multiplied by step S421
SSS frequency-region signals, the sequence for obtaining is and reconstructs the SSS frequency-region signals for coming；
S445, step S444 is reconstructed the SSS frequency-region signals for coming go in time domain, and plus prefix, that is, reconstructed
Whole SSS time-domain signals.
The present embodiment said method carries out related operation with reception signal respectively by three groups of local PSS sequences, so as to obtain
Three groups of PSS correlations are got, for each group of PSS correlation, is obtained in PSS correlations by relation ranking from big to small front
Several PSS correlation peaks, that is, get several PSS correlation peaks maximum in PSS correlation peaks；Then from maximum PSS phases
The position for closing peak value starts, and for each PSS correlation peak location, carries out one or many SSS coherent detections such that it is able to
When the downlink synchronous signal of the homogeneous frequency adjacent area using same PSS signals reaches UE simultaneously, can be relatively strong by signal
Cell and the relatively weak cell of signal search, effectively prevent Reconstruction Method used in prior art and carry out PSS interference and disappear
Except causing to search the relatively strong cell of signal, and the phenomenon that the relatively weak cell of signal searched can not be arrived.Greatly
The performance and the performance of handover of big raising UE down-going synchronous, so as to improve Consumer's Experience.And adopt in the inventive method
SSS is eliminated with reconstruct side, can eliminate to greatest extent used between adjacent two cells of same PSS under current scene
Interference.
In the present embodiment by repeating above-mentioned steps S32 and S33 after can by PSS correlations according to from big to small
Relation ranking it is searched out with order from big to small in former PSS correlation peaks.In search every time, selection is moved into one's husband's household upon marriage
A maximum PSS correlation peak in the PSS correlation peaks of limit, and the PSS correlation peak locations are got, then should
The correlation of PSS correlation peak locations and its adjacent each some positions in front and back carries out zero setting；It is current maximum during due to searching for every time
PSS correlation peaks be set to zero, therefore when searching for next time, the PSS correlation peaks for searching will be second to this maximum PSS phase
Close peak value.
Therefore the present invention effectively eliminates interference of the PSS strong correlations peak to the weak relevant peaks of PSS by way of zero setting, reaches
The purpose that interference is eliminated, can to greatest extent eliminate the interference of PSS, determine potential effectively correlation peak location and cell
Mark in ID groups, effectively reduces the complexity that PSS interference is eliminated, and improves the efficiency that PSS interference is eliminated.And the present invention exists
In zeroing process, the correlation of adjacent each some positions is also set to zero, therefore this before and after current maximum PSS correlation peaks
Inventive method can simultaneously avoid the PSS correlation peak front and back position correlations of current maximum from searching PSS correlation peaks next time
The interference produced during rope, eliminates to greatest extent interference of the PSS strong correlations peak to the weak relevant peaks of PSS.The inventive method is effective
Avoid in prior art for relatively weak cell, the PSS interference meetings of elimination are carried out because channel estimation value using Reconstruction Method
It is inaccurate, cause PSS to be eliminated to greatest extent, while can also introduce larger interference, cause the weaker cell can not be by
The technical problem for detecting.
Above-described embodiment is the present invention preferably embodiment, but embodiments of the present invention not by above-described embodiment
Limit, other any Spirit Essences without departing from the present invention and the change, modification, replacement made under principle, combine, simplification,
Equivalent substitute mode is should be, is included within protection scope of the present invention.
Claims (10)
1. cell searching interference elimination method in a kind of LTE system, it is characterised in that step is as follows：
S1, acquisition receive signal；
S2, three groups of local PSS sequences are gone to into respectively time domain from frequency domain, then respectively to receive in step S1 signal carry out it is related
Three groups of PSS correlations are obtained after computing；
S3, for each group of PSS correlation, by the first thresholding by PSS correlations by relation ranking from big to small front
Several PSS correlation peaks search out come, until search less than cross the first thresholding PSS correlation peaks or current search to PSS phases
Close peak value and reach certain number X, then terminate search, preserve each PSS correlation peaks position searched above by the first thresholding
Put and the interior mark of cell ID group；
S4, each PSS correlation peak locations for getting in each group of PSS correlation in step S3, from maximum PSS phases
Close peak to start, with PSS correlation peaks order from big to small, for each PSS correlation peak location, carry out as follows
Operation：
S41, first according to current PSS correlation peak locations, docking is collected mail and number carries out SSS coherent detections, obtains SSS correlations,
Then the SSS correlation peaks of the second thresholding were searched for by the second thresholding, and therefrom got a SSS relevant peaks of maximum
Value；Into step S42；
S42, SSS interference is eliminated：By the maximum corresponding SSS signal reconstructions of SSS correlation peaks out, then will reconstruct what is come
SSS signals cut from the reception signal of correspondence position, obtain disturbing the signal after eliminating；Subsequently into step S43；
S43, according to current PSS correlation peak locations, for step S42, to disturb the reception signal after eliminating to carry out SSS again related
Detection, obtains SSS correlations, and the SSS correlation peaks of the second thresholding were then searched for by the second thresholding, determines whether the
The SSS correlation peaks of two thresholdings；
If so, a SSS correlation peak of maximum is then selected from the SSS correlation peaks for crossing the second thresholding；Then judge logical
Whether the number for crossing the maximum SSS correlation peaks that the second thresholding has been chosen altogether reaches certain number Y, if it is not, then entering
Enter step S42, if so, then enter step S44；
If it is not, then entering step S44；
Under S44, current PSS correlation peak locations, SSS interference eliminations are completed, and for next PSS correlation peak locations, are returned
To step S41.
2. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that the step
Three groups of local PSS sequences go to respectively comprising the following steps that for time domain from frequency domain in S2：
S21, according in the cell ID group of PSS sequences identifyValue 0,1 and 2, get three groups of local frequency domain PSS sequences
Row, wherein the length of local frequency domain PSS sequences is 62；
S22, per group of local frequency domain PSS sequence is both mapped to before and after direct current subcarrier on each 31 subcarriers；
S23, every group of signal for getting in step S22, supplemented 33 zero before local frequency domain PSS sequence subcarriers,
32 zero are supplemented afterwards, and removing after frequency is processed carries out 128 point, inverse fast Fourier transforms, finally gives three groups of local time domains PSS
Sequence.
3. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that the step
Each group PSS correlation is got by following steps in S2：
S24, receive signal in get starting point P0, then start to take 256 sampled points from starting point P0, then it is done
256 points of FFT, obtains the first frequency-region signal；It is the signal wherein to receive first starting point P0 got in signal
The first sampled point；
S25,128 sampled points are taken from one group of local time domain PSS sequence, zero padding is to 256 sampled points and does 256 points of FFT,
Obtain the second frequency-region signal；
S26, the first frequency-region signal and the second frequency-region signal conjugate multiplication are obtained into the 3rd signal, then carry out the 3rd signal
256 points of IFFT obtains time-domain signal；
S27, front 128 sampled points for taking the time-domain signal that step S26 gets, as one group local time domain PSS sequence and reception
Correlation after signal 128 related operations of slip；
S28, judge to receive and whether carry out related calculation and obtain correlation at signal ending, if so, then this group of related operation terminates；If
It is no, then starting point P0 is added and return to step S24 after 128 sampled points.
4. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that in step S3
For each group of PSS correlation, by the first thresholding by PSS correlations according to relation ranking from big to small former
With sequential search from big to small out, detailed process is as follows for PSS correlation peaks：
S31, for each group of PSS correlation, the first thresholding is set first；
S32, the PSS correlation peaks that the first thresholding was searched for by the first thresholding, determined whether that the PSS of the first thresholding was related
Peak value；
If so, a PSS correlation peak of maximum is then selected from the PSS correlation peaks for crossing the first thresholding, then judges to work as
The front number for passing through the maximum PSS correlation peaks that the first thresholding has been chosen altogether reaches certain number X, if so, then enters
Enter step S34；If it is not, then entering step S33；
If it is not, then entering step S34；
S33, by the maximum PSS correlation peak locations got in step S32 and its it is adjacent before and after each some positions
Correlation zero setting；It is then return to step S32；
S34, the search by the first thresholding for PSS correlation peaks terminate.
5. cell searching interference elimination method in LTE system according to claim 4, it is characterised in that described first
It is 5 that the threshold value of thresholding is 9000, X values.
6. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that step S41 and
According to current PSS correlation peak locations in S43, the process for carrying out SSS coherent detections is as follows：
S411, using current PSS correlation peak locations as PSS timing positions, with reference to the various relative position relations of PSS and SSS,
Determine each timing position of SSS；
S412,128 point SSS time-domain signals are taken respectively in each timing position of SSS, then carry out 128 point SSS time-domain signals
128 FFTs, obtain 128 sampled point frequency-region signals；
The corresponding data of label 65 in S413,128 sampled point frequency domain sequences are direct current subcarrier, each before and after direct current subcarrier
31 frequency domain sequences are extracted, the frequency domain sequence for constituting at 62 points is SSS frequency-region signals；
S414, according to the generating mode of SSS, progressively descramble and the correlation using m-sequence carry out related calculation, obtain SSS related
Peak value, and therefrom get SSS maximum correlation peaks；
S415, according to SSS maximum correlation peaks, carry out duplex mode, CP types, cell ID group mark and in front and back field sentenced
Certainly, cell ID and frame timing are so far obtained with.
7. cell searching interference elimination method in LTE system according to claim 6, it is characterised in that PSS and SSS
Relative position relation include four kinds, wherein TDD (time division duplex) and Normal CP (general cyclic prefix) relative position relation
Under, PSS and SSS relative positions are 412 sampled points；TDD and Extended CP (extended cyclic prefix) relative position relation
Under, PSS and SSS relative positions are 480 sampled points；Under FDD (FDD) and Normal CP relative position relations, PSS and
SSS relative positions are 137 sampled points；Under FDD and Extended CP relative position relations, PSS and SSS relative position relations
It is down 160.
8. cell searching interference elimination method in LTE system according to claim 6, it is characterised in that the step
Detailed process in S42 by the corresponding SSS signal reconstructions of SSS maximum correlation peaks out is as follows：
S421, according in step S415 determine cell ID and frame timing, generate SSS frequency-region signals；
S422, extract in signal the corresponding SSS signals of SSS maximum correlation peaks from receiving；
The SSS signals obtained in S423, SSS frequency-region signals and step S422 for generation in step S421 carry out least square
Channel estimation, and time domain noise reduction process is carried out to channel estimation value sequence；
The SSS that channel estimation value sequence after S444, the time domain noise reduction for getting step S423 process is multiplied by step S421
Frequency-region signal, the sequence for obtaining is and reconstructs the SSS frequency-region signals for coming；
S445, step S444 is reconstructed the SSS frequency-region signals for coming go in time domain, and plus prefix, that is, reconstruct complete
SSS time-domain signals.
9. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that the step
The threshold value of the second thresholding is 200 in S4；Y is 2.
10. cell searching interference elimination method in LTE system according to claim 1, it is characterised in that the step
The signal that receives obtained in S1 is filtering and the reception signal after down-sampled process.
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