CN102158933B - Method and device for frequency band searching in TDD-LTE (Time Division Duplex-Long Term Evolution) system - Google Patents

Abstract

The invention discloses a method for frequency band searching in a TDD-LTE (Time Division Duplex-Long Term Evolution) system and a device for frequency band searching of a terminal/user unit in the TDD-LTE system. The method comprises the steps of: obtaining signals; obtaining signals with respect to a base station on a searched frequency band; estimating strength: estimating strength of each signal with respect to the base station; comparing: comparing the strength of the signal with respect to the base station with a first threshold determined in advance; determining the frequency band: when the strength is more than the first threshold determined in advance, selecting a frequency band where the signals with the strength being more than the first threshold determined in advance, with respect to the base station, as the frequency band to be accessed; and switching the frequency band: when the strength is more than the first threshold determined in advance, switching the searched frequency band, and re-executing the steps for the switched frequency band.

Description

The method and apparatus of searching for for frequency band in TDD-LTE system

Technical field

Present invention relates in general to wireless communication system, more specifically, relate to a kind of method and apparatus of searching for for frequency band in TDD-LTE (time division duplex-Long Term Evolution) system.

Background technology

Along with developing rapidly of mobile communication technology, wireless communication system presents the trend of mobile, broadband and IPization, and the competition of Mobile Communications Market is also growing more intense.For reply is from WiMAX, the challenge of the tradition such as Wi-Fi and emerging WiMAX access technology, improve 3-G (Generation Three mobile communication system) (3G) in the competitiveness in broadband wireless access market, 3GPP carries out the research of universal mobile telecommunications system (UMTS) terrestrial wireless access (UTRA) Long Term Evolution (LTE) technology, to realize 3G technology seamlessly transitting to super 3 g mobile communication system (B3G) and the 4th Generation Mobile Communication System 4G.The improvement target of LTE is to realize higher data rate, shorter time delay, lower cost, higher power system capacity and improved coverage.

LTE system has defined Frequency Division Duplexing (FDD) (FDD) and two kinds of modes of time division duplex (TDD) simultaneously.Two kinds of frame structures of LTE TDD have been unified in 3GPP RAN1 meeting.The fusion of tdd frame structure makes LTE TDD technology be subject to paying attention to widely.

In wireless communication system, user equipment (UE) need to carry out frequency band search when start, to find community or the frequency band that is applicable to access, thereby You Gai community or frequency band carry out downlink data receiving and decode reliably.For Next-Generation Wireless Communication Systems, for example, for LTE system, owing to there being the frequency band of a plurality of work, therefore how correctly finding applicable frequency band is a crucial problem for accessing.

Summary of the invention

Provided hereinafter about brief overview of the present invention, to the basic comprehension about some aspect of the present invention is provided.Should be appreciated that this general introduction is not about exhaustive general introduction of the present invention.It is not that intention is determined key of the present invention or pith, and nor is it intended to limit the scope of the present invention.Its object is only that the form of simplifying provides some concept, usings this as the preorder in greater detail of discussing after a while.

According to an aspect of the present invention, provide a kind of method of searching for for frequency band in TDD-LTE system, having comprised: signal acquisition step: obtain the signal specific to base station on search frequency band; Intensity estimating step: estimate that each is specific to the intensity of the signal of base station; Comparison step: the intensity of the signal specific to base station and predetermined first threshold are compared; Frequency band determining step: when intensity is greater than predetermined first threshold, selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access; Frequency band switch step: when intensity is less than predetermined first threshold, switch search frequency band, and re-execute above-mentioned steps for the frequency band after switching.

According to another aspect of the present invention, provide a kind of frequency band searcher for TDD-LTE system terminal/subscriber unit, having comprised: signal acquisition device, it is arranged to the signal specific to base station obtaining on search frequency band; Intensity estimation unit, it is arranged to estimates each intensity specific to the signal of base station; Comparison means, it is arranged to the intensity of the signal specific to base station and predetermined first threshold is compared; Access frequency band determining device, it is arranged to when intensity is greater than predetermined first threshold, and selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access; Frequency band switching device shifter, it is arranged to when intensity is less than predetermined first threshold, switches search frequency band.

By according to the solution of the present invention, during the frequency band that can will access in user equipment searches, get rid of reliably the interference that near far effect causes, thereby obtain best net synchronization capability and link quality, improve communication quality.

By the detailed description to most preferred embodiment of the present invention below in conjunction with accompanying drawing, these and other advantage of the present invention will be more obvious.

Accompanying drawing explanation

The present invention can, by reference to hereinafter given description and being better understood by reference to the accompanying drawings, wherein use same or analogous Reference numeral to represent identical or similar parts in institute's drawings attached.Described accompanying drawing comprises in this manual and forms the part of this specification together with detailed description below, and is used for further illustrating the preferred embodiments of the present invention and explains principle and advantage of the present invention.In the accompanying drawings:

Fig. 1 shows a typical scene with near far effect (Near-remote Effect).

Fig. 2 shows the schematic diagram of power measurement of the prior art.

Fig. 3 shows the flow chart of the method for frequency band search according to an embodiment of the invention.

Fig. 4 shows the schematic diagram for the plot planning of the master sync signal of different i values.

Fig. 5 shows the flow chart of the method for frequency band search according to another embodiment of the invention.

Fig. 6 shows the schematic diagram of frequency band searcher according to an embodiment of the invention.

Fig. 7 shows the schematic diagram of frequency band searcher according to another embodiment of the invention.

Embodiment

In connection with accompanying drawing, one exemplary embodiment of the present invention is described hereinafter.All features of actual execution mode are not described for clarity and conciseness, in specification.Yet, should understand, in the process of any this practical embodiments of exploitation, must make a lot of decisions specific to execution mode, to realize developer's objectives, for example, meet those restrictive conditions with system and traffic aided, and these restrictive conditions may change to some extent along with the difference of execution mode.In addition,, although will also be appreciated that development is likely very complicated and time-consuming, concerning having benefited from those skilled in the art of present disclosure, this development is only routine task.

At this, also it should be noted is that, for fear of the details because of unnecessary fuzzy the present invention, only show in the accompanying drawings with according to the closely-related apparatus structure of the solution of the present invention and/or treatment step, and omitted other details little with relation of the present invention.

Inventor notices, in TDD-LTE system, frequency band search is comparatively complicated problem, because can there is so-called near far effect in TDD-LTE system.Fig. 1 is schematically illustrated in the typical scene that in TDD-LTE system, subscriber equipment may run into when carrying out frequency band search.

Figure 1 illustrates a typical scene with near far effect (Near-remote Effect).San Ge community Cell 1, Cell 2 and Cell 3 as can see from Figure 1, they work respectively on different frequency band Band 1, Band 2 and Band 3, and the centre frequency of these three frequency bands is different each other, as shown in the upper figure in Fig. 2.Wherein the base station of Cell 1 and user equipment (UE) 1 are the most approaching.In community Cell 2, there is another user equipment (UE) 2 nearby.In prior art, normally used frequency band searching method is to measure the signal power receiving in UE1 place, and using the frequency band that sends maximum signal power as the frequency band that will access.Yet may cause problem in the scene shown in Fig. 1.Normal, because the base station of UE1 distance C ell 1 is nearest, therefore the power of received Band1 also should be maximum.Yet owing to there being UE2, as shown in the figure below in Fig. 2, UE1 can be added the signal power of the base station from UE2 and Cell 2, this gross power of result is greater than the signal power from the base station of Cell 1, make UE1 access mistakenly Band 2, cause UE1 can not obtain best net synchronization capability and link quality, affect communication efficiency.

the first embodiment

Inventor notices, causes in the prior art the major reason that UE accesses to be mistakenly interference noise, and this noise may be from other subscriber equipmenies, also may be from other noise sources.Due to the signal distinguishing this interference noise and base station not being sent in the prior art, cause carrying out at subscriber equipment the power addition of the useful signal that frequency band when search send the power of interference noise and base station simply, thereby easily cause the false judgment of the frequency band to accessing.

Inventor notices, if the distinctive signal that can utilize base station to send when subscriber equipment carries out frequency band search, this distinctive signal is different from noise signal, during the frequency band that will access in judgement, can get rid of noise effect.

Therefore, according to one embodiment of present invention, a kind of method for frequency band search has been proposed.Fig. 3 shows the flow chart of the method.

As shown in Figure 3, the method comprises:

S310: obtain the signal specific to base station on search frequency band;

S330: estimate that each is specific to the intensity of the signal of base station;

S350: the intensity of the signal specific to base station and predetermined first threshold are compared;

S370: when intensity is greater than predetermined first threshold, selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access.

S390: when intensity is less than predetermined first threshold, change search frequency band, and re-execute step S310 for the frequency band after changing.

Due to the signal having used in said method specific to base station, and interference noise does not have sort signal, therefore according to this signal strength signal intensity, judge that the frequency band that will access got rid of the impact of interference noise, can realize access more accurately, improve the performance of system.

Applicant further studies discovery, in TDD-LTE system, always includes the signal specific to base station in the downstream signal that send base station, for example PSS (main synchronous) signal and SSS (subsynchronous) signal.The PSS signal of take below describes as example.It is pointed out that following content is equally applicable to SSS signal.

Below PSS signal is simply introduced.

In LTE system, one has three kinds of PSS signals, from frequency domain, is expressed as the Zadoff-Chu sequence that parameter is different.PSS signal can represent with following formula:

$\mathrm{PSS}(i,n)=\left\{\begin{array}{cc}{e}^{-j\frac{\mathrm{\πin}(n+1)}{63}}& n=\mathrm{0,1},...,30\\ e^{-j\frac{\mathrm{\πi}(n+1)(n+2)}{63}}& n=\mathrm{31,32},...,61\end{array}\right.---\left(1\right)$

Wherein parameter i can get 25,29 or 34.

This sequence (length is 62) can be mapped near 62 subcarriers centered carrier on frequency domain, and in both sides, respectively mends 5 zero, takies altogether 72 subcarriers.In TDD system, through IFFT conversion (invert fast fourier transformation), the OFDM symbol that comprises PSS can be put into subframe subframe#1, on the 3rd the OFDM symbol of subframe#6.Because the duration of subframe is 1ms, so the transmission cycle of PSS is 5ms.

More detailed description about PSS and SSS signal can, referring to 3GPP standard TS36.211v8.7.0, not further describe at this.

As schematically shown in Fig. 4, in actual applications, can be so that the PSS signal that adjacent base station is used has different i values by plot planning.When subscriber equipment determines that power from the PSS signal of the first base station is maximum, because interference noise does not have PSS signal, therefore can determine comparatively exactly that the frequency band of this first base station is good candidate band, and get rid of the impact of interference noise.

Hypothesis adopts PSS signal for being specifically described specific to the signal of base station in the method shown in Fig. 3 below.

Before implementing according to the method shown in Fig. 3, in subscriber equipment, stored the copy PSS (i, n) of PSS signal, wherein for LTE system, there is i=0,1,2; N=0,1,2 ..., 127.In addition, obtained initial center frequency in subscriber equipment, this initial center frequency can be inputted by outside, can be also the frequency pre-setting.

In step S310, subscriber equipment obtains the sample signal from base station, and wherein this sample signal comprises PSS signal.Owing to certainly existing the PSS signal corresponding to 128 sample points in every field in TDD LTE standard (corresponding to 9600 sample points).Preferably, the length of sample signal is not less than 9600+128 sample point.Particularly preferably, the length of sample signal is 9600+128 sample point, so that estimate the intensity of the PSS signal that comprises in this sample signal.The length of sample signal of take below describes as 9600+128.

In step S330, estimate the intensity of PSS signal in each sample signal.The copy PSS (i, n) of the PSS signal of storing in this can utilize subscriber equipment and the correlation of sample signal in time domain carry out sample estimates signal in the intensity of PSS signal.

Suppose that sample signal is r, can calculate by following formula the correlation C (i, m) of sample signal and PSS copy:

$C(i,m)={|\underset{n=0}{\overset{127}{\mathrm{\Σ}}}r{(n+m)}^{*}\·\mathrm{PSS}(i,n)|}^2---\left(2\right)$

Wherein C (i, m) represents that m sample point from sample signal starts 128 sample points afterwards and the correlation of PSS copy PSS (i, n), m=0, and 1,2 ..., 9599, r (n+m) ^*the conjugation that represents respective sample point in sample signal.Should be appreciated that the intensity estimation (being correlation) that can utilize other related operation to obtain PSS signal here.

Owing to must comprising PSS signal in each sample signal from different base station, therefore by (2) formula, for each sample signal, can find corresponding i and definite starting point m, in the situation that can obtain maximum correlation C corresponding to the copy PSS (i, n) of this i value with m _max(i, m).Those skilled in the art easily know, in the situation that obtain maximum correlation, the sample point at this m value place is exactly the starting point of the PSS signal in sample signal.Therefore obtained in this way the PSS signal in sample signal and be stored in the correlation between the PSS signal copy in subscriber equipment, also just having obtained the PSS signal strength signal intensity estimated value in corresponding sample signal.

In step S350, determine maximum PSS signal strength signal intensity estimated value, and this maximum PSS signal strength signal intensity estimated value and predetermined first threshold are compared.If this maximum PSS signal strength values is greater than first threshold, the signal strength signal intensity of frequency band that the PSS signal place of this intensity estimated value maximum is described can be accepted, therefore in step S370 using the frequency band at the PSS signal place of this intensity estimated value maximum as the frequency band that will access.If maximum PSS signal strength values is less than first threshold, illustrate this intensity level maximum PSS signal place frequency band signal strength signal intensity too a little less than, therefore perform step S390.

In step S390, switch the frequency of the oscillator in subscriber equipment, make to obtain sample signal on other frequency band.Subsequently, re-execute step S310.

Inventor notices, conventionally after all frequency bands having been carried out to said method by the oscillator frequency in switching subscriber equipment, by utilizing suitable first threshold can determine the frequency band that subscriber equipment will access.Yet under some extreme cases, the maximum PSS signal strength values that subscriber equipment is determined on all frequency bands may all be less than first threshold, now preferably Second Threshold can be set, if maximum PSS signal strength values is greater than Second Threshold, directly using the frequency band at maximum PSS signal strength values place as the frequency band that will access, if maximum PSS signal strength values is less than Second Threshold, point out user not have frequency band to access.

By the method that proposed according to the abovementioned embodiments of the present invention, advantageously only considered to access for frequency band from the signal of base station, and for example avoided to a great extent the interference noise impact from other subscriber equipmenies.

the second embodiment

Inventor notices, although can as in above-mentioned the second embodiment, directly utilize correlation to judge as the signal strength signal intensity of PSS signal, yet owing to may, with uplink interference signal, therefore may affecting judged result in the sample signal receiving.

According to a modification of the present invention scheme, can utilize normalized correlation to estimate the signal strength signal intensity of PSS signal.

Normalized correlation is designated as

, can obtain by following formula:

$\tilde{C}(i,m)=\frac{C(i,m)}{N\left(m\right)}---\left(3\right)$

Wherein: $N\left(m\right)=\underset{n=0}{\overset{127}{\mathrm{\Σ}}}{\left|r(n+m)\right|}^2---\left(4\right)$

Obtain normalized correlation

afterwards, be similar to that above-described method is like that same can be arranged corresponding threshold value and judge, this is not described further.

By utilizing normalized correlation to estimate the signal strength signal intensity of PSS signal, advantageously overcome the impact of uplink interference signal.

Preferably, for these obtained intensity, estimate

, determine that the maximum intensity in these intensity estimations is estimated

$\tilde{C}(i_0,m_0)=\underset{i,m}{\max }\left\{\tilde{C}(i,m)\right\}---\left(5\right)$

For maximum intensity, estimate

, calculate and use maximum intensity to estimate

the main synchronizing sequence PSS of correspondence (i ₀) intensity that obtains estimates

, m=0,1,2 ..., 9599 peak-to-average force ratio M.

For example, peak-to-average force ratio M can be that maximum intensity is estimated and in intensity estimation, estimates the ratio of the average of other intensity estimation that the identical PSS sequence of employing obtains with maximum intensity.Particularly,

$M=\frac{\tilde{C}(i_0,m_0)}{\frac{1}{9600-1}\underset{m=0,m\≠m_0}{\overset{9599}{\mathrm{\Σ}}}\tilde{C}(i_0,m)}---\left(6\right)$

As an alternative, peak-to-average force ratio M can be the ratio that maximum intensity is estimated the average of all intensity estimations that PSS sequence identical with employing obtains.Particularly,

$M=\frac{\tilde{C}(i_0,m_0)}{\frac{1}{9600}\underset{m=0}{\overset{9599}{\mathrm{\Σ}}}\tilde{C}(i_0,m)}---\left(7\right)$

Should be appreciated that peak-to-average force ratio M can define to calculate according to other.

After obtaining peak-to-average force ratio M, be similar to that above-described method is same like that can be arranged corresponding threshold value and judge, this is not described further.

By utilizing peak-to-average force ratio M to estimate the signal strength signal intensity of PSS signal, advantageously overcome the impact of uplink interference signal, and can further improve the accuracy of frequency band search.

the 3rd embodiment

In order further to improve the accuracy for the estimation of PSS signal, preferably, said method according to the present invention can be carried out repeatedly at each frequency band, and judges the frequency band that will access according to the result of repeatedly carrying out.

Fig. 5 shows according to an embodiment of the invention for utilizing PSS signal to carry out the flow chart of the method for search frequency band.

As can be seen from Figure 5, the method also comprises step S360 on the basis of the method shown in Fig. 3: whether the number of times that judgement is obtained all sample signals at current search frequency band is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, again perform step S310 to again obtain sample signal r from current search frequency band _kif, be greater than the 3rd threshold value, perform step S370 to switch search frequency band, to detect on other frequency bands.

After the sample signal obtaining step of repeatedly carrying out on same frequency band, can estimate in the following manner the signal strength signal intensity of PSS signal:

1), in the situation that directly utilize correlation to estimate the signal strength signal intensity of PSS signal, for the k time repetition, can calculate correlation:

$C_k(i,m)={|\underset{n=0}{\overset{127}{\mathrm{\Σ}}}{r}_k{(n+m)}^{*}\·\mathrm{PSS}(i,n)|}^2---\left(8\right)$

C _k(i, m) represents in i main synchronizing sequence and k sample sequence that wherein * represents conjugation from the correlated results of the initial subsequence of m sample, m=0, and 1,2 ..., 9599.

For PSS (i, n), can calculate respectively the maximum related value C for each i value (i=0,1,2) _{k, max}(i, m), and the mean value after this K time is repeated

intensity as corresponding PSS signal PSS (i, n) is estimated.Should be appreciated that also can utilize other related operation to obtain intensity estimates.

2) in the situation that utilize normalized correlation to estimate the signal strength signal intensity of PSS signal, for each C _k(i, m), estimates C according to intensity _kthe intensity of the corresponding sample signal of (i, m) and N _k(m) intensity is estimated to C _k(i, m) normalization, obtains normalized intensity and estimates

, wherein

$N_k\left(m\right)=\underset{n=0}{\overset{127}{\mathrm{\Σ}}}{\left|r_k(n+m)\right|}^2---\left(9\right)$

${\tilde{C}}_k(i,m)=\frac{C_k(i,m)}{N_k\left(m\right)}---\left(10\right)$

And the mean value that utilizes normalized intensity to estimate

$\tilde{C}(i,m)=\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\tilde{C}}_k(i,m)/K---\left(11\right)$

Estimate the intensity of corresponding PSS signal.

3), in the situation that utilize peak-to-average force ratio to estimate the signal strength signal intensity of PSS signal, can estimate according to these intensity of obtaining above

, determine that the maximum intensity in these intensity estimations is estimated (being normalized correlation) here

$\tilde{C}(i_0,m_0)=\underset{i,m}{\max }\left\{\tilde{C}(i,m)\right\}---\left(12\right)$

And estimate for maximum intensity

, calculate and use maximum intensity to estimate the main synchronizing sequence PSS of correspondence (i ₀) intensity that obtains estimates

, m=0,1,2 ..., 9599 peak-to-average force ratio M.

For example, peak-to-average force ratio M can be that maximum intensity is estimated and in intensity estimation, estimates the ratio of the average of other intensity estimation that the identical main synchronizing sequence of employing obtains with maximum intensity.Particularly,

$M=\frac{\tilde{C}(i_0,m_0)}{\frac{1}{9600-1}\underset{m=0,m\≠m_0}{\overset{5990}{\mathrm{\Σ}}}\tilde{C}(i_0,m)}---\left(13\right)$

For example, peak-to-average force ratio M can be the ratio that maximum intensity is estimated the average of all intensity estimations that main synchronizing sequence identical with employing obtains.Particularly,

$M=\frac{\tilde{C}(i_0,m_0)}{\frac{1}{9600}\underset{m=0}{\overset{9599}{\mathrm{\Σ}}}\tilde{C}(i_0,m)}---\left(14\right)$

Should be appreciated that peak-to-average force ratio M can define to calculate according to other.

Owing to having carried out repeatedly according to each frequency band of the method for the present embodiment, and judge the frequency band that will access according to the result of repeatedly carrying out, therefore further eliminated the impact of other Gaussian noises in communication system, improved the accuracy of judgement.

It should be noted that, according to the above-mentioned first to the 3rd embodiment, those skilled in the art can easily be applied to SSS signal by corresponding method.Because SSS signal has more morely than PSS signal, so computing cost is larger, yet its principle is identical with above-described method, and this is not described further.

the 4th embodiment

Therefore, according to one embodiment of present invention, a kind of frequency band searcher for TDD-LTE system terminal/subscriber unit has been proposed.Fig. 6 shows the schematic diagram of this frequency band searcher.

As shown in Figure 6, this frequency band searcher 600 comprises:

Signal acquisition device 610, its be arranged to obtain on search frequency band the signal specific to base station;

Intensity estimation unit 630, it is arranged to estimates each intensity specific to the signal of base station;

Comparison means 650, it is arranged to the intensity of the signal specific to base station and predetermined first threshold is compared;

Access frequency band determining device 670, it is arranged to when intensity is greater than predetermined first threshold, and selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access.And

Frequency band switching device shifter 690, it is arranged to when intensity is less than predetermined first threshold, changes search frequency band.

Because frequency band searcher 600 has used the signal specific to base station, and interference noise does not have sort signal, therefore according to this signal strength signal intensity, judge that the frequency band that will access got rid of the impact of interference noise, can realize access more accurately, improve the performance of system.

Applicant further studies discovery, in TDD-LTE system, always includes the signal specific to base station in the downstream signal that send base station, for example PSS (main synchronous) signal and SSS (subsynchronous) signal.Therefore frequency band searcher 600 can utilize PSS signal or SSS signal to carry out frequency band search as the signal specific to base station.

Hypothesis adopts PSS signal for being specifically described specific to the signal of base station in frequency band searcher 600 below.

Before frequency band searcher 600 carries out frequency band search, in subscriber equipment, stored the copy PSS (i, n) of PSS signal, wherein for LTE system, there is i=0,1,2; N=0,1,2 ..., 127.In addition, obtained initial center frequency in subscriber equipment, this initial center frequency can be inputted by outside, can be also the frequency pre-setting.

First, signal acquisition device 610 obtains the sample signal from base station, and wherein this sample signal comprises PSS signal.Owing to certainly existing the PSS signal corresponding to 128 sample points in every field in TDD LTE standard (corresponding to 9600 sample points).Preferably, the length of sample signal is not less than 9600+128 sample point.Particularly preferably, the length of sample signal is 9600+128 sample point, so that estimate the intensity of the PSS signal that comprises in this sample signal.The length of sample signal of take below describes as 9600+128.

Intensity estimation unit 630 is estimated the intensity of PSS signal in each sample signal subsequently.The copy PSS (i, n) of the PSS signal of storing in this can utilize subscriber equipment and the correlation of sample signal in time domain carry out sample estimates signal in the intensity of PSS signal.

Suppose that sample signal is r, can calculate by following formula the correlation C (i, m) of sample signal and PSS copy:

$C(i,m)={|\underset{n=0}{\overset{127}{\mathrm{\Σ}}}r{(n+m)}^{*}\·\mathrm{PSS}(i,n)|}^2---\left(2\right)$

Wherein C (i, m) represents that m sample point from sample signal starts 128 sample points afterwards and the correlation of PSS copy PSS (i, n), m=0, and 1,2 ..., 9599, r (n+m) ^*the conjugation that represents respective sample point in sample signal.Should be appreciated that the intensity estimation that can utilize other related operation to obtain PSS signal.

Owing to must comprising PSS signal in each sample signal from different base station, therefore by (2) formula, for each sample signal, can find corresponding i and definite starting point m, in the situation that can obtain maximum correlation C corresponding to the copy PSS (i, n) of this i value with m _max(i, m).Those skilled in the art easily know, in the situation that obtain maximum correlation, the sample point at this m value place is exactly the starting point of the PSS signal in sample signal.Therefore obtained in this way the PSS signal in sample signal and be stored in the correlation between the PSS signal copy in subscriber equipment, also just having obtained the PSS signal strength values in corresponding sample signal.

Comparison means 650 is determined maximum PSS signal strength signal intensity estimated value subsequently, and this maximum PSS signal strength signal intensity estimated value and predetermined first threshold are compared.If this maximum PSS signal strength signal intensity estimated value is greater than first threshold, the signal strength signal intensity of frequency band that the PSS signal place of this intensity estimated value maximum is described can be accepted, and therefore accesses frequency band determining device 670 using the frequency band at the PSS signal place of this intensity estimated value maximum as the frequency band that will access.If maximum PSS signal strength signal intensity estimated value is less than first threshold, illustrate this intensity estimated value maximum PSS signal place frequency band signal strength signal intensity too a little less than, therefore frequency band switching device shifter 690 switches the frequency of the oscillator in subscriber equipment, makes to obtain sample signal on other frequency band.Subsequently, re-execute frequency band search procedure.

Inventor notices, conventionally after all frequency bands having been carried out to said method by the oscillator frequency in switching subscriber equipment, by utilizing suitable first threshold can determine the frequency band that subscriber equipment will access.Yet under some extreme cases, the maximum PSS signal strength values that subscriber equipment is determined on all frequency bands may all be less than first threshold, now preferably Second Threshold can be set, if maximum PSS signal strength values is greater than Second Threshold, direct using the frequency band at maximum PSS signal strength values place as the frequency band that will access, otherwise prompting user does not have frequency band to access.

By the frequency band searcher 600 that proposed according to the abovementioned embodiments of the present invention, advantageously only considered to access for frequency band from the signal of base station, and for example avoided to a great extent the interference noise impact from other subscriber equipmenies.

Inventor notices, although can directly utilize correlation to judge as the signal strength signal intensity of PSS signal, yet owing to may, with uplink interference signal, therefore may affecting judged result in the sample signal receiving.

Therefore according to a modification of the present invention scheme, can utilize normalized correlation to estimate the signal strength signal intensity of PSS signal, also can utilize peak-to-average force ratio M to estimate the signal strength signal intensity of PSS signal.About utilizing the content of normalized correlation and peak-to-average force ratio, specifically, referring to the description of method part, repeat no more here.

By utilizing peak-to-average force ratio M to estimate the signal strength signal intensity of PSS signal, advantageously overcome the impact of uplink interference signal, and can further improve the accuracy of frequency band search.

the 5th embodiment

In order further to improve the accuracy for the estimation of PSS signal, preferably, frequency band searcher 600 according to the present invention can also comprise and obtain number of times judgment means 660, and it can be so that frequency band searcher 600 be carried out repeatedly frequency band search procedure at each frequency band.

Fig. 7 shows the schematic diagram of improved frequency band searcher 700 according to an embodiment of the invention.

As can be seen from Figure 7, this frequency band searcher 600 also comprises and obtains number of times judgment means 660 on the basis of the structure shown in Fig. 6, it is configured to the number of times that judgement obtains all sample signals at current search frequency band and whether is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, control signal acquisition device 610 is to again obtain sample signal rk from current search frequency band, if be greater than the 3rd threshold value, control frequency band switching device shifter 690 to switch search frequency band, to detect on other frequency bands.

After repeatedly carrying out the frequency band search procedure of same frequency band, can utilize average correlation, average normalized value or peak-to-average force ratio to determine the frequency band that will access.This can, referring to according to the content in the method described in the 3rd embodiment, be repeated no more here.

Owing to having carried out repeatedly according to each frequency band of the method for the present embodiment, and judge the frequency band that will access according to the result of repeatedly carrying out, therefore further eliminated the impact of other Gaussian noises in communication system, improved the accuracy of judgement.

It should be noted that, in frequency band searcher 600 according to the present invention, can use SSS signal equally.Because SSS signal has more morely than PSS signal, so computing cost is larger, yet its principle is identical with above-described method, and this is not described further.

By above description, be not difficult to find out, according to embodiments of the invention, provide following scheme:

1. 1 kinds of methods of searching for for frequency band in TDD-LTE system of remarks, comprising:

Signal acquisition step: obtain the signal specific to base station on search frequency band;

Intensity estimating step: estimate that each is specific to the intensity of the signal of base station;

Comparison step: the intensity of the signal specific to base station and predetermined first threshold are compared;

Frequency band determining step: when intensity is greater than predetermined first threshold, selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access;

Frequency band switch step: when intensity is less than predetermined first threshold, switch search frequency band, and re-execute above-mentioned steps for the frequency band after switching.

Remarks 2. is according to the method described in remarks 1, and wherein the signal specific to base station is master sync signal or subsynchronous signal.

Remarks 3. is according to the method described in remarks 1 or 2, also comprise and obtain number of times determining step: whether the number of times that judgement is obtained all signals specific to base station at current search frequency band is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, executive signal obtaining step again, to again obtain sample signal from current search frequency band, if be greater than the 3rd threshold value, carry out frequency band switch step to switch search frequency band.

Remarks 4. is according to the method described in any one in above-mentioned remarks, and the copy that wherein utilizes the signal specific to base station of storing in subscriber equipment and the correlation of the signal specific to base station obtaining in time domain are estimated the intensity of the obtained signal specific to base station.

Remarks 5. is according to the method described in any one in above-mentioned remarks, wherein utilize normalized correlation to estimate the intensity of the obtained signal specific to base station, described normalized correlation is that the copy of the signal specific to base station of storing in subscriber equipment is obtained after the correlation normalization in time domain with the signal specific to base station that obtains.

Remarks 6. is according to the method described in any one in above-mentioned remarks, wherein utilizes the peak-to-average force ratio of normalized correlation to estimate the intensity of the obtained signal specific to base station.

7. 1 kinds of frequency band searchers (600) for TDD-LTE system terminal/subscriber unit of remarks, comprising:

Signal acquisition device (610), it is arranged to the signal specific to base station obtaining on search frequency band;

Intensity estimation unit (630), it is arranged to estimates each intensity specific to the signal of base station;

Comparison means (650), it is arranged to the intensity of the signal specific to base station and predetermined first threshold is compared;

Access frequency band determining device (670), it is arranged to when intensity is greater than predetermined first threshold, and selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access;

Frequency band switching device shifter (690), it is arranged to when intensity is less than predetermined first threshold, switches search frequency band.

Remarks 8. is according to the frequency band searcher (600) described in remarks 7, and wherein the signal specific to base station is master sync signal or subsynchronous signal.

Remarks 9. is according to the frequency band searcher (600) described in remarks 7 or 8, also comprise and obtain number of times judgment means (660), it is arranged to the number of times that judgement obtains all signals specific to base station at current search frequency band and whether is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, executive signal obtaining step again, to again obtain sample signal from current search frequency band, if be greater than the 3rd threshold value, control frequency band switching device shifter and switch search frequency band.

Remarks 10. is according to the frequency band searcher (600) described in any one in remarks 7 to 9, and the copy that wherein intensity estimation unit (630) utilizes the signal specific to base station of storing in subscriber equipment and the correlation of the signal specific to base station obtaining in time domain are estimated the intensity of the obtained signal specific to base station.

Remarks 11. is according to the frequency band searcher (600) described in any one in remarks 7 to 9, wherein intensity estimation unit (630) utilizes normalized correlation to estimate the intensity of the obtained signal specific to base station, and described normalized correlation is that the copy of the signal specific to base station of storing in subscriber equipment is obtained after the correlation normalization in time domain with the signal specific to base station that obtains.

Remarks 12 is according to the frequency band searcher (600) described in any one in remarks 7 to 9, and wherein intensity estimation unit (630) utilizes the peak-to-average force ratio of normalized correlation to estimate the intensity of the obtained signal specific to base station.

Claims (8)

1. a method of searching for for frequency band in TDD-LTE system, comprising:

Signal acquisition step: obtain the signal specific to base station on search frequency band;

Intensity estimating step: estimate that each is specific to the intensity of the signal of base station;

Comparison step: the intensity of the signal specific to base station and predetermined first threshold are compared;

Frequency band determining step: when intensity is greater than predetermined first threshold, selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access;

Frequency band switch step: when intensity is less than predetermined first threshold, switch search frequency band, and re-execute above-mentioned steps for the frequency band after switching,

Wherein utilize normalized correlation to estimate the intensity of the obtained signal specific to base station, described normalized correlation is that the copy of the signal specific to base station of storing in subscriber equipment is obtained after the correlation normalization in time domain with the signal specific to base station that obtains.

2. method according to claim 1, wherein the signal specific to base station is master sync signal or subsynchronous signal.

3. method according to claim 1 and 2, also comprise and obtain number of times determining step: whether the number of times that judgement is obtained all signals specific to base station at current search frequency band is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, executive signal obtaining step again, to again obtain sample signal from current search frequency band, if be greater than the 3rd threshold value, carry out frequency band switch step to switch search frequency band.

4. method according to claim 1 and 2, wherein utilizes the peak-to-average force ratio of described normalized correlation to estimate the intensity of the obtained signal specific to base station.

5. the frequency band searcher (600) for TDD-LTE system terminal/subscriber unit, comprising:

Signal acquisition device (610), it is arranged to the signal specific to base station obtaining on search frequency band;

Intensity estimation unit (630), it is arranged to estimates each intensity specific to the signal of base station;

Comparison means (650), it is arranged to the intensity of the signal specific to base station and predetermined first threshold is compared;

Access frequency band determining device (670), it is arranged to when intensity is greater than predetermined first threshold, and selection intensity is greater than the frequency band at the signal place specific to base station of predetermined first threshold as the frequency band that will access;

Frequency band switching device shifter (690), it is arranged to when intensity is less than predetermined first threshold, switches search frequency band,

Wherein intensity estimation unit (630) utilizes normalized correlation to estimate the intensity of the obtained signal specific to base station, and described normalized correlation is that the copy of the signal specific to base station of storing in subscriber equipment is obtained after the correlation normalization in time domain with the signal specific to base station that obtains.

6. frequency band searcher according to claim 5 (600), wherein the signal specific to base station is master sync signal or subsynchronous signal.

7. according to the frequency band searcher (600) described in claim 5 or 6, also comprise and obtain number of times judgment means (660), it is arranged to the number of times that judgement obtains all signals specific to base station at current search frequency band and whether is greater than predetermined the 3rd threshold value, if be less than the 3rd threshold value, executive signal obtaining step again, to again obtain sample signal from current search frequency band, if be greater than the 3rd threshold value, control frequency band switching device shifter and switch search frequency band.

8. according to the frequency band searcher (600) described in claim 5 or 6, wherein intensity estimation unit (630) utilizes the peak-to-average force ratio of described normalized correlation to estimate the intensity of the obtained signal specific to base station.

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