WO2012119403A1

WO2012119403A1 - Method and device of searching for frequency bands in communication system

Info

Publication number: WO2012119403A1
Application number: PCT/CN2011/078654
Authority: WO
Inventors: 魏璟鑫
Original assignee: 华为技术有限公司
Priority date: 2011-08-19
Filing date: 2011-08-19
Publication date: 2012-09-13
Also published as: CN102356671B; CN102356671A

Abstract

The present invention relates to the field of communication system, and disclosed are a method and a device of searching for frequency bands in a communication system, thereby reducing time for searching for frequency bands in a communication system. The method of searching for frequency bands in a communication system comprises: through normalization processing performed on a time domain sequence of a primary synchronization signal (PSS) and a time domain signal of a carrier frequency point, acquiring a signal normalization correlation value of the carrier frequency point; detecting whether the signal normalization correlation value of the carrier frequency point is greater than a preset normalization correlation threshold value; and when the signal normalization correlation value of the carrier frequency point is greater than the normalization correlation threshold value, performing initial searching on the carrier frequency point. The embodiments of the present invention are applied to frequency band searching of the communication system.

Description

Method and device for searching frequency band of communication system

The present invention relates to the field of communication systems, and more particularly to the field of communication system band search technology. BACKGROUND When a user equipment (UE, also referred to as a terminal) is configured in a known frequency band, it is required to detect which frequency points in the frequency band exist in the cell of the LTE system, and use the initial search to search for the cell, so as to try to stay in the station. Said cell. The LTE system uses PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal) to complete cell search. PSS is used to complete symbol timing synchronization. The PSS signal repetition period is 5ms, while the configurable frequency band of the 3GPP LTE system is generally wide, such as the widest frequency band is 100MHZ. If the UE directly searches for the frequency points in any frequency band one by one, the UE will face a problem that takes a long time, the power consumption of the UE becomes large, and the user's feeling is also poor.

In order to solve this problem, the prior art has respectively tried a method of frequency point power measurement and a frequency band search method based on fast Fourier transform (FFT) spectrum analysis to shorten the time for the UE to search for a cell existing in an LTE system.

The frequency power measurement method is a power measurement of signals at all frequency points in the frequency band, and the frequency of the frequency search is determined by the measured power level. However, in addition to the LTE system, the frequency band can also allow other communication systems to exist, such as GSM, WCDMA, and the like. In this way, since the signal transmission power of the different system tends to be larger than that of the LTE system, the carrier frequency of the different system will be ranked in front of the true frequency point, and the frequency band search time is too long.

Band search based on FFT spectrum analysis is based on the power spectral density (PSD) of different systems for system identification. However, since the LTE system has multiple transmission bandwidths, such PSD identification needs to try all possible transmission bandwidths for each frequency point, which will lead to an increase in the calculation amount and complexity of the system, and there is still a problem that the system search time is too long. .

Summary of the invention

Embodiments of the present invention provide a method and apparatus for frequency band search of a communication system, which can reduce a cell search time of a UE.

In order to achieve the above object, the embodiment of the present invention adopts the following technical solutions:

A method for searching a frequency band of a communication system, comprising: Obtaining a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the primary synchronization signal PSS and the time domain signal of the carrier frequency point;

Detecting whether a normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold;

When the signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold, an initial search is performed on the carrier frequency point.

A device for searching a frequency band of a communication system, comprising:

a normalized cross-correlation value obtaining unit, configured to obtain a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the PSS and the time domain signal of the carrier frequency point;

a detecting unit, configured to detect whether a normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold;

And an initial search unit, configured to perform an initial search on the carrier frequency point when a signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value.

The method and device for searching a frequency band of a communication system according to an embodiment of the present invention obtains a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the PSS and the time domain signal of the carrier frequency point. And performing an initial search on the carrier frequency point when a signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value. In this way, for the signals of the non-communication system, the normalized cross-correlation values can be compared directly, and the frequency points are directly excluded, and the initial search is not needed, thereby shortening the initial search time and the number of times of the UE.

BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the embodiments or the description of the prior art will be briefly described below, and obviously, in the following description The drawings are only some of the embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

1 is a schematic flow chart of a method for searching a frequency band of a communication system according to Embodiment 1 of the present invention;

2 is a block diagram of an apparatus for searching for a frequency band of an LTE system according to Embodiment 1 of the present invention; FIG. 3 is a schematic flowchart of a method for searching a frequency band of an LTE system according to Embodiment 2 of the present invention; Figure

4 is a schematic flow chart of a method for searching for a frequency band of an LTE system according to Embodiment 3 of the present invention;

5 is a block diagram of an apparatus for searching for a frequency band of an LTE system according to Embodiment 4 of the present invention; FIG. 6 is a block diagram of an apparatus for searching for a frequency band of an LTE system according to Embodiment 5 of the present invention; FIG. 7 is a schematic diagram of an LTE system according to Embodiment 5 of the present invention; Another block diagram of the device for band search.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention. Embodiment 1

A method for searching a frequency band of a communication system provided by an embodiment of the present invention, as shown in FIG. 1, includes the following steps:

S101. Acquire a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the primary synchronization signal PSS and the time domain signal of the carrier frequency point.

S102: Detect whether a normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold.

5103. Perform an initial search on the carrier frequency point when the signal normalized cross-correlation value is greater than the normalized cross-correlation threshold.

The UE needs to perform an initial search from the power-on search to camping on the appropriate cell. Taking the LTE system as an example, the initial search of the cell needs to complete the process of detecting the cell ID, orthogonal frequency division multiplexing (OFDM) symbol synchronization and frame synchronization, cyclic prefix (CP) type detection, frequency offset size estimation, etc., specific search process. I won't go into details here.

The embodiment of the present invention further provides a device for searching a frequency band of a communication system. As shown in FIG. 2, the device includes a normalized cross-correlation value acquisition unit 21, a detection unit 22, and an initial search unit 23. The normalized cross-correlation value obtaining unit 21 is configured to obtain a signal normalized cross-correlation value of the carrier frequency point by normalizing the time domain sequence of the PS S and the time domain signal of the carrier frequency point.

The detecting unit 22 is configured to detect whether the normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold.

The initial search unit 23 is configured to perform an initial search on the carrier frequency point when a signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value.

The detection unit 22 and the initial search unit 23 may be located in the same processor, and the normalized cross-correlation value acquisition unit 21 may be another processor. The apparatus may be located in one UE or in a baseband processor of the UE.

The method and device for searching a frequency band of a communication system according to an embodiment of the present invention perform normalization processing by using a time domain sequence of a PS S and a time domain signal of a carrier frequency point to obtain a normalized cross-correlation value of the carrier frequency point, And determining the carrier frequency of the non-communication system by judging the normalized cross-correlation value of the carrier frequency point and the preset normalized cross-correlation threshold value, and the carrier frequency point of the part is not required. An initial search is performed, thereby shortening the time and number of times the UE terminal band search is performed.

Embodiment 2

The embodiment of the present invention provides a method for searching a frequency band of a communication system. The specific embodiment of the present invention is specifically illustrated by the LTE system. As shown in FIG. 3, the method includes the following steps:

S301. Calculate a cross-correlation value j (d) of a time domain sequence of the PSS and a time domain signal of the carrier frequency point, and a power value (d) of the time domain signal of the carrier frequency point.

Where ( =

+ )| ² , ( For the time domain signal received by the ith receiver antenna of the UE through the baseband filter multiplexer, the sampling rate of this embodiment can be set to 1.92 Mbps, the sampling time is 5 ms, and the ( ) signal has a total of 9600 Sample point, d is the sample point number of the time domain signal of the carrier frequency point, and d is a value between 0 and 9599. Of course, the baseband filter receives Time domain signals can also be sampled from multiple 5ms for band search with lower signal to noise ratio. Wherein (^ ₍₂ »is determined to N _ID PSS

The time domain sequence, the time domain sequence is a complex form, and the complex number needs to be conjugated in the calculation process, that is, Λ3⁄4) is a parameter used to determine the cell identity in the physical layer of the LTE system, and the value is {0, 1, 2}, the time domain sequence of PSS is uniquely determined by Λ). Ν is the length of the time domain sequence of PSS, where Ν=128, and M*L=N, and M can take values of 2, 4, 8, and so on.

S302. Determine a normalized cross-correlation value PSSCorr of the carrier frequency signal, that is, PSSCorr=

Calculate the correlation value of each sample point corresponding to the time domain sequence of each PSS

Corr{d, ^ ) = ∑ ^Ad) lY,{d , the maximum value of the correlation values of each of the sampling points for the time domain sequence of each PSS is used as the signal of the carrier frequency a cross-correlation value, ie J^C r= max {Corr(d, N£ ^{ )}, where I is the receiving antenna of the UE

Λ3⁄4) =0,1,2 ¹

d = 0, the number of ..Di; D means (the number of sampling points of the signal, as in the previous step, the number of sampling points D is taken as 9600. The PSS can be one or more, when there is only one PSS, the UE can For this

The PSS calculates a correlation value ^^(^A) of each sample point, and normalizes the cross-correlation value to the signal whose maximum value is used as the carrier frequency point. If there are multiple PSSs, the UE can target each PSS Calculate the correlation value of each sample point C^r^A^), that is, each sample of each pss gets a correlation value ^^(), and the maximum of all these values is used as the carrier frequency. The signal of the point normalizes the cross-correlation value.

The physical layer of the LTE system has 504 cell ID identification numbers, which are divided into 168 different groups, and each group has 3 different cell ID identification numbers. The physical layer cell ID identification number is represented as Λ^ = 3Λ^ + Λ^, where the value is {0, 1, 2}, and the time domain sequence of the PSS is uniquely determined. Correspondingly, the signal of each carrier frequency point corresponds to the time domain sequence of three different PSSs, and the corresponding

Comparing the values of C d , ) determined by the time domain sequences of the three PSSs, taking the maximum value of the signal normalized cross-correlation value ^psscorr of the carrier frequency. In practical applications, those skilled in the art can adapt the solution, for example, the second largest value can be taken in all ^^(

The adjusted scheme can still be effectively detected compared with the prior art, and the time and number of times of the UE frequency band search are shortened.

S303: Detect whether a normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold. When the signal normalized cross-correlation value of the carrier frequency point is large, the process proceeds to step S304; when the signal normalized cross-correlation value of the carrier frequency point is small, the process proceeds to step S305.

The preset normalization threshold is a preset normalization threshold value in advance in accordance with the formulas in steps S301 and S302, in the case of estimating the channel signal-to-noise ratio and having a margin.

S304: Perform an initial search on the carrier frequency point when a signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value. Through the formulas in steps S301 and S302, the normalized cross-correlation value is the signal power of the carrier frequency, and the correlation between the received signal and the PSS is calculated. When the signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value, if the signal indicating the carrier frequency point has a greater correlation with the signal of the LTE system, the The carrier frequency is used for initial search.

S305: When the signal normalized cross-correlation value of the carrier frequency point is not greater than the normalized cross-correlation threshold, or the carrier frequency point does not search for an LTE cell, or the searched LTE cell cannot be performed. When camping, the time domain signal of another carrier frequency point is normalized with the time domain sequence of the PSS, and the signal normalized cross-correlation value of the other frequency point is obtained, and the detection process is continued.

For the above method of frequency band search, the details are as follows:

In the frequency band configured by the UE, the UE needs to perform an initial search camp on the LTE cell after being powered on. The UE receives a signal of a carrier frequency point in the frequency band, acquires a time domain signal through a 1.4 MHz baseband filter, and calculates a power value of the time domain signal of the carrier frequency point! ^.( , and the cross-correlation value XT of the time domain sequence of the PSS and the time domain signal of the carrier frequency point; calculating the correlation value of each sampling point corresponding to the time domain sequence of each PSS

, will needle

And a maximum value of the correlation value ^^^,^ of each of the sampling points of the time domain sequence of each PSS is used as a normalized mutual value of the signal of the carrier frequency point, that is, PSSCorr =

According to the calculated value of the carrier frequency point PSSCorr, compared with the preset normalization threshold value, if the PSSCorr value is large, the UE may perform an initial search. If the LTE cell is found to exist, the UE attempts to camp on the cell. If the cell cannot camp, the UE needs to switch to another of the band. A carrier frequency point is calculated, and the signal normalized cross-correlation value of the carrier frequency point is calculated, and the search is continued according to the method of the embodiment.

If the PSSCorr value is greater than the preset normalization threshold, and the UE does not search for the LTE cell after performing the initial search at the carrier frequency, the UE switches to the frequency band to obtain another carrier frequency, and calculates the carrier frequency. The signal of the point normalizes the cross-correlation value.

If the PSSCorr value is less than or equal to the preset normalization threshold, the UE directly switches to another carrier frequency, and calculates a signal normalized cross-correlation value of the carrier frequency.

Further, if the UE has successfully camped on the LTE cell in the frequency band, or the UE processes all the frequency points in the frequency band, and the signal normalization value of the frequency point carrier is not greater than the preset normalization gate. The UE, or the UE that did not search for LTE, or the searched LTE cell does not successfully camp, the UE band search ends.

The frequency band searching method of the communication system provided by the embodiment of the present invention performs normalization processing by using a time domain sequence of the PSS and a time domain signal of the carrier frequency point to obtain a normalized cross-correlation value of the carrier frequency point, by determining the The normalized cross-correlation value of the carrier frequency point and the preset normalized cross-correlation threshold value can filter out the carrier frequency point of the communication system, and does not need to perform an initial search on the carrier frequency point of the part. Thereby shortening the time and number of times of UE frequency band search.

Embodiment 3

The embodiment of the present invention further provides a method for searching a frequency band of a communication system. The embodiment of the present invention is still described by using an LTE system as an example. As shown in FIG. 4, the method includes:

S401: Perform normalization processing by using a time domain sequence of the PS S and a time domain signal of the carrier frequency to obtain a signal normalized cross-correlation value of the carrier frequency.

S402. Sort the signal normalized cross-correlation values of the plurality of carrier frequency points of the system frequency band according to the order of the largest to smallest, obtain the first frequency point order of the carrier frequency points, and perform the order detection according to the first frequency point. Whether the normalized cross-correlation value of the carrier frequency point is greater than a preset normalized cross-correlation value.

S403. Detect whether a normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold; when the signal normalized cross-correlation value of the carrier frequency is large, skip to Step S404; otherwise, the process goes to step S406.

S 404. When the normalized cross-correlation value of the signal is greater than the normalized cross-correlation threshold, perform an initial search on the carrier frequency. If an LTE cell is searched, go to step S405; otherwise, skip to Step S406.

S405: If the UE searches for an LTE cell, try to camp. If it cannot camp, skip to S406; otherwise, the UE search ends.

Step 5406: Switch to the next frequency point according to the order of sorting the first frequency points in step S402, and execute step S403.

Further, the LTE frequency band search method in the embodiment of the present invention may further be: performing normalization processing by using a time domain sequence of the PSS and a time domain signal of a carrier frequency point to obtain a normalized mutual signal of the carrier frequency point. Before detecting the correlation value, first detecting the power level of the carrier frequency point signal, sorting according to the detected power from large to small, obtaining the second frequency point order of the carrier frequency point, and detecting whether the normalized correlation value of the carrier frequency point is greater than a preset normalized cross-correlation threshold, corresponding to when the carrier frequency signal normalization value is not greater than a preset normalized cross-correlation threshold, or an LTE cell is not searched at the frequency, or If the LTE cell cannot be camped on, the signal is switched to the next frequency point according to the order of the second frequency points, and the signal normalized cross-correlation value of the next carrier frequency point is obtained, and the detection is continued. process. Of course, detecting the power level of the carrier frequency point signal and performing the ordering may also be performed after acquiring the signal normalized cross-correlation value of the carrier frequency.

The frequency band searching method of the communication system provided by the embodiment of the present invention sorts the numerical values of the normalized cross-correlation values of the carrier frequency points in the frequency band, and firstly detects that the normalized cross-correlation value of the highest-ranked carrier frequency points is large. Comparing with the preset normalized cross-correlation threshold value, if the normalized cross-correlation value of the carrier frequency point is large, an initial search is performed on the carrier frequency point, so that the detection of the normalized value can not only screen the communication The carrier frequency of the system can further shorten the initial search time of the UE.

Embodiment 4

An embodiment of the present invention further provides a device for searching a frequency band of a communication system, and this embodiment Taking the LTE system as an example, as shown in FIG. 5, the method includes: a normalized cross-correlation value acquiring unit 51, a detecting unit 52, and an initial searching unit 53. Each unit can be a processor, and each processor can be implemented by an integrated circuit. The apparatus may be located in one UE or in a baseband processor of the UE.

The normalized cross-correlation value obtaining unit 51 is configured to obtain a signal normalized cross-correlation value of the carrier frequency point by normalizing the time domain sequence of the PSS and the time domain signal of the carrier frequency point.

The normalized cross-correlation value obtaining unit 51 further includes:

a calculating subunit 51 1 , configured to calculate, according to the i th receiving antenna of the user equipment

The cross-correlation value of each time point of the time domain sequence of the PSS and the time domain signal of the carrier frequency point and the power value of each sample point ¹ ^ , d is the sampling point number of the time domain signal of the carrier frequency point . a normalized cross-correlation value determining sub-unit 512, configured to calculate a correlation of each of the sampling points

value

Where / is the number of receiving antennas that the UE has, and the maximum value of the correlation values C d, Nf of each of the sampling points is used as a signal normalized cross-correlation value of the carrier frequency point. The detecting unit 52 is configured to detect whether the signal normalized cross-correlation value of the carrier frequency point is greater than a preset normalized cross-correlation threshold value.

The initial search unit 53 is configured to perform an initial search on the carrier frequency point when the signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value.

Further, the calculation subunit may further be a time domain sequence for each PSS in the time domain sequence of the plurality of PSSs, and calculate a time domain sequence and a carrier frequency of the PSS corresponding to the i th receive antenna of the UE, respectively. The cross-correlation value of each sample point of the time domain signal of the point X person d, and The power value Y of each sampling point Y is d; d is the sampling point number of the time domain signal of the carrier frequency point; the normalized cross-correlation value determining subunit is used to calculate the time domain sequence for each PSS The correlation value of each of the sample points is ^^^, ^^ ^^^ / ^) , where / is

The UE has a number of receiving antennas, and the maximum value of the correlation values c dO of each of the sampling points of the time domain sequence of each PSS is used as a signal normalized cross-correlation value of the carrier frequency point. The communication system band search device provided by the embodiment of the present invention uses the calculation sub-unit 51 1 and the normalized cross-correlation value determination sub-unit 512 of the normalized cross-correlation value acquisition unit 51 to obtain the normalized cross-correlation of the carrier frequency points. The value is determined according to the normalized cross-correlation value of the carrier frequency point and the preset normalized cross-correlation threshold value, and the partial system signal is screened out, which reduces the time and number of times the UE performs the initial search.

Embodiment 5

The embodiment of the present invention further provides a device for searching a frequency band of a communication system. This embodiment uses an LTE system as an example. As shown in FIG. 6, the method includes a normalized cross-correlation value obtaining unit 61 and a first frequency point sorting unit. 65. Detection unit 62, initial search unit 63.

The normalized cross-correlation value obtaining unit 61 is configured to obtain a normalized mutual value of the signal of the carrier frequency point by normalizing the time domain sequence of the PSS and the time domain signal of the carrier frequency.

The first frequency point sorting unit 65 sorts the signal normalized cross-correlation values of the plurality of carrier frequency points of the system frequency band in descending order, and obtains the first frequency point order of the carrier frequency points.

The detecting unit 62 is configured to detect, according to the first frequency point order, whether the signal normalized cross-correlation value of the carrier frequency point is greater than a preset normalized cross-correlation threshold value.

An initial search unit 63, configured to: when the signal frequency of the carrier frequency is normalized, the cross-correlation value is greater than When the normalized cross-correlation threshold is normalized, an initial search is performed on the carrier frequency. Further, another device for searching the frequency band of the LTE system according to the embodiment of the present invention, as shown in FIG. 7, may further include: a power measuring unit 66, configured to measure power of all the carrier frequency signals in the frequency band; And the second frequency point sorting unit 67, sorting the signal powers of the plurality of carrier frequency points in descending order, and acquiring the second frequency point ordering of the plurality of carrier frequency points. Thus, when the signal normalized cross-correlation value of the carrier frequency point is not greater than the normalized cross-correlation threshold value, or the carrier frequency point does not search for the LTE cell, or the searched LTE cell cannot be camped on. During the stay, the detecting unit detects, according to the second frequency point order, whether the normalized cross-correlation value of the signal of the next carrier frequency is greater than a preset normalized cross-correlation threshold. Certainly, detecting the power level of the carrier frequency point signal and performing the sorting may also be performed after acquiring the signal normalized cross-correlation value of the carrier frequency point.

The frequency band searching device of the communication system provided by the embodiment of the present invention obtains a normalized cross-correlation value of a carrier frequency point, sorts the value of the signal normalized cross-correlation value of all carrier frequency points, and preferentially detects the normalized cross-correlation value. Large carrier frequency, which can further shorten the time and number of initial search of the UE.

The LTE frequency band search apparatus provided by the embodiment of the present invention may be located in an LTE wireless receiver, such as an LTE baseband processor. It can be understood that the method provided in this embodiment is applicable not only to the LTE system but also to other communication systems having a cell search function, such as a PLMN system.

Further, the LTE system band search method provided by the embodiment of the present invention can also be used for full-band search of PLMN (Public Land Mobile Network). When the normalized cross-correlation value of the carrier frequency point is not greater than a preset normalized cross-correlation threshold value, an initial search is not performed on the carrier frequency point. This will shorten the PLMN's full-band search time.

A person skilled in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by using hardware related to program instructions, and the foregoing program may be stored in a computer readable storage medium, and the program is executed when executed. The foregoing steps include the steps of the foregoing method embodiments; and the foregoing storage medium includes: a medium that can store program codes, such as a ROM, a RAM, a magnetic disk, or an optical disk. The above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the appended claims.

Claims

Claim

A method for searching a frequency band of a communication system, comprising:

Obtaining a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the primary synchronization signal PSS and the time domain signal of the carrier frequency point;

Detecting whether the normalized cross-correlation value of the signal of the carrier frequency is greater than a preset normalized cross-correlation threshold;

When the signal normalized cross-correlation value of the carrier frequency point is greater than the normalized cross-correlation threshold value, an initial search is performed on the carrier frequency point.

2. The method according to claim 1, wherein the signal of the carrier frequency is obtained by normalizing a time domain sequence of a primary synchronization signal PSS and a time domain signal of a carrier frequency point. The normalized cross-correlation values include:

Calculating a cross-correlation value ^{X d} of each time point of the time domain sequence of the PSS corresponding to the ith receiving antenna of the user equipment UE and a time domain signal of the carrier frequency point, and a power value ^Y 'W of each sampling point , d is a sampling point number of the time domain signal of the carrier frequency point;

1-1 calculating a correlation value of each sampling point ^^^, ^^ '^ , where is the number of receiving antennas that the UE has, and the correlation value of each sampling point is ^^(^ Α The maximum value in ^) is used as the signal normalized cross-correlation value of the carrier frequency point.

The method according to claim 1, wherein the signal of the carrier frequency is obtained by performing normalization processing on a time domain sequence of a primary synchronization signal PSS and a time domain signal of a carrier frequency point. The normalized cross-correlation value includes: calculating a time domain sequence of the PSS corresponding to the i th receiving antenna of the UE and a carrier frequency point respectively for a time domain sequence of each PSS in the time domain sequence of the plurality of PSSs Each of the domain signals The cross-correlation value X,.(c) of the sample point and the power value of each sample point

d is the sampling point number of the time domain signal of the carrier frequency point; calculating the correlation value of each of the sampling points for the time domain sequence of each PSS

€οττ(ά,Ν^) =∑Χ^) / Y^d) , where / is the number of receive antennas the UE has, and each of the sample points for the time domain sequence of each of the PSSs The maximum value in the correlation value CT^A^) is used as the signal normalized cross-correlation value of the carrier frequency point.

The method according to any one of claims 1 to 3, further comprising: when a signal normalized cross-correlation value of the carrier frequency point is not greater than the normalized cross-correlation threshold value Or acquiring an LTE cell at the carrier frequency point, or not camping on the searched LTE cell, acquiring a time domain signal of another carrier frequency point, and time domain of the other carrier frequency point The signal performs the method.

The method according to any one of claims 1 to 4, further comprising: sorting the signal normalized cross-correlation values of the plurality of carrier frequency points of the system frequency band in descending order Sorting the first frequency points of the carrier frequency points;

The detecting whether the normalized cross-correlation value of the carrier frequency is greater than a preset normalized cross-correlation threshold includes: detecting, according to the first frequency point, whether the normalized cross-correlation value of the carrier frequency is detected Greater than the preset normalized cross-correlation value.

The method according to any one of claims 1 to 4, further comprising: measuring signal power of a plurality of carrier frequency points of the system frequency band, and controlling signal power of the plurality of carrier frequencies according to a large to small Sorting the order of the second frequency points of the carrier frequency points; and determining whether the normalized cross-correlation value of the signal of the carrier frequency point is greater than a preset normalized cross-correlation threshold value includes: The two-frequency point sorting detects whether the normalized cross-correlation value of the carrier frequency point is greater than a preset normalized cross-correlation value.

7. A device for searching a frequency band of a communication system, comprising: a normalized cross-correlation value obtaining unit, configured to obtain a normalized cross-correlation value of the signal of the carrier frequency point by normalizing the time domain sequence of the primary synchronization signal PSS and the time domain signal of the carrier frequency point;

The apparatus according to claim 7, wherein the normalized cross-correlation value obtaining unit comprises: a calculating subunit and a normalized cross-correlation value determining subunit;

The calculating subunit, configured to calculate, according to the i th receiving antenna of the user equipment UE

a cross-correlation value ^x A ^d of each sample point of the time domain sequence of the PSS and the time domain signal of the carrier frequency point, and a power value of each of the sample points ( d is a time domain signal of the carrier frequency point a sampling point number; the normalized cross-correlation value determining subunit, configured to calculate a phase of each sampling point

K d, , ₌

Wherein / is the number of receiving antennas of the UE, and the maximum value of the correlation value ^^( ) of each sampling point is used as a normalized cross-correlation value of the signal of the carrier frequency point; a calculation subunit, configured to calculate a time domain sequence of the PSS corresponding to the i th receive antenna of the UE and a time domain of the carrier frequency point, respectively, for a time domain sequence of each PSS in the time domain sequence of the multiple PSSs a cross-correlation value XT of each sample point of the signal and a power value d of each of the sample points is a sample point number of a time domain signal of the carrier frequency point; the normalized cross-correlation value determining subunit, Said to calculate a time domain sequence for each PSS Correlation value Corr{d , Ν^^ Χ IY , {0, where / is the UE has

/=0 receiving the number of antennas, normalizing the maximum value of the correlation values C d'N^ of the each sampling point of the time domain sequence of each PSS as the signal of the carrier frequency point Relevant value.

The device according to claim 7 or 8, further comprising: a first frequency point sorting unit, wherein the signal normalized cross-correlation values of the plurality of carrier frequency points of the system frequency band are in accordance with a large to small Sorting sequentially to obtain a first frequency point ordering of the carrier frequency points; the detecting unit, configured to detect, according to the first frequency point order, whether a normalized cross-correlation value of the carrier frequency point is greater than a preset normalization Correlation value.

The device according to claim 7 or 8, further comprising: a power measuring unit, configured to measure power of all carrier frequency point signals in the frequency band; and a second frequency point sorting unit, for multiple carrier frequency points The signal powers are sorted in descending order, and the second frequency point order of the plurality of carrier frequency points is obtained;

The detecting unit is configured to detect, according to the second frequency point order, whether the normalized cross-correlation value of the carrier frequency point is greater than a preset normalized cross-correlation value.