CN102215202A - Device and method for estimating frequency deviation of LTE (long term evolution) system - Google Patents

Abstract

The invention discloses a device and method for estimating the frequency deviation of an LTE (long term evolution) system. The method comprises the following steps: acquiring the CP (cyclic prefix) frequency deviation estimation results of the existing subframe and the RS (reference signal) frequency deviation estimation results of the existing subframe by calculation; during the frequency deviation estimation process of the LTE system, switching between the CP frequency deviation estimation results and the RS frequency deviation estimation results of the existing subframe according to the existing status of the LTE; and selecting the frequency deviation estimation results satisfying the current frequency estimation conditions to conduct frequency deviation calibration. In the device and method disclosed in the invention, the selection of the frequency deviation results satisfying the conditions can ensure to obtain high-accuracy frequency deviation estimation while frequency deviation estimation is conducted on a large scale, and can also ensure to obtain a larger frequency deviation estimation scope while the high-accuracy frequency deviation estimation is acquired.

Description

The frequency deviation estimation device of LTE system and method

Technical field

The present invention relates to communication technical field, say so more specifically, relate to the frequency deviation estimation device and the method for a kind of LTE (Long Term Evolution system, long evolving system).

Background technology

The LTE system is thought accurate 4G wireless communication system widely, and it has the transmission rate of the up 50M of descending 100M.LTE is based on the wireless communication system of OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology.

Be illustrated in figure 1 as the frame structure of LTE, a radio frames length T _fBe 10ms (T _f=307200T _s=10ms), comprise 10 subframes; A subframe lengths T is 1ms, comprises 2 time slots.A slot length T _SlotBe 0.5ms (T _Slot=15360T _s=0.5ms), comprise 7 OFDM symbols.

The formation of an OFDM symbol as shown in Figure 2 comprises: data division (Data) 202 and Cyclic Prefix part (CP, cyclic prefix) 201.The length of data division is T _Data=2048T _s, the CP length of first OFDM symbol of each time slot is T _CP=160T _s, the CP length of other OFDM symbols is T _CP=144T _sThe time slot of a LTE is made of Resource Block (RB, resource block), a kind of typical resource block structures as shown in Figure 3, on the time t direction by 7 OFDM symbols and frequency direction

Individual resource particle (RE, resource element) constitutes,

Contain altogether in the middle of the time slot

Individual Resource Block,

By the system bandwidth decision, under the 20M system bandwidth, one

Individual subframe meta is called a Resource Block to (RB pair) in two adjacent Resource Block of two time slots.

In a Resource Block, have 7 * 12=84 subcarrier, mainly comprise the data subcarrier that is used for carrying data, and the reference signal (RS, reference signal) subcarrier or the reference signal that are used for carrying the known symbol sequence that uses for channel estimation process or synchronizing process.The reference signal configuration pattern of eNodeB end antenna port 0 as shown in Figure 4, wherein, R ₀The position is the reference signal position, and all the other positions are the data subcarrier position.Position distribution about reference signal RS and data subcarrier is not limited in this.

Structure based on frame structure, OFDM symbol, LTE time slot and the Resource Block of above-mentioned LTE, and the structure of the subcarrier in the LTE Resource Block, concerning based on the LTE wireless communication system of OFDM technology, the OFDM technology is to carrier wave frequency deviation (CFO, carrier frequency offset) very responsive, because CFO can cause inter-carrier interference, influence systematic function, therefore need carry out frequency offset estimating accurately it.

In the prior art, LTE system frequency deviation estimating method commonly used has two kinds usually, a kind of frequency deviation estimating method that is based on RS, and its estimated accuracy is higher, but it is but very little to carry out estimation range, has only+/-1KHz.Another kind is based on the frequency deviation estimating method of CP, though its estimation range is bigger, the precision of its estimation is lower, and is difficult to carry out frequency offset estimating accurately during less than 0dB in signal to noise ratio.

Therefore, current exigence is a kind of can be implemented in the big frequency offset estimation range, carries out the method and apparatus of high-precision frequency offset estimating.

Summary of the invention

In view of this, the invention provides the frequency deviation estimation device and the method for a kind of LTE system, can not satisfy the problem of in big frequency offset estimation range, carrying out high-precision frequency offset estimating in the prior art simultaneously to overcome.

For achieving the above object, the invention provides following technical scheme:

The frequency deviation estimation device of a kind of long evolving system LTE comprises:

The frequency deviation estimating modules of Cyclic Prefix part CP is used for obtaining the frequency offset estimation result of the CP of corresponding current subframe to carry out the frequency offset estimating based on CP through the digital signal of exporting after the analog-to-digital conversion;

Go the CP module, be used for obtaining the time-domain signal of orthogonal frequency division multiplex OFDM symbol going CP to handle through the digital signal of exporting after the analog-to-digital conversion;

Extract reference signal RS module, be used for extracting the RS symbol of the frequency-region signal of described time-domain signal after fast Fourier transform;

The frequency deviation estimating modules of RS is used to obtain the frequency offset estimation result of described RS;

The frequency deviation handover module is used for according to default frequency deviation switching condition, selects the frequency offset estimation result of described CP or the frequency offset estimation result of described RS to carry out the frequency deviation calibration.

Preferably, described frequency deviation handover module comprises:

First switch unit, be used for absolute value when the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP smaller or equal to second handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the RS of current subframe and the RS of last subframe switches to the frequency offset estimating of RS during smaller or equal to first handoff threshold;

Second switch unit, be used for absolute value when the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP more than or equal to the 4th handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the CP of current subframe and the CP of last subframe switches to the frequency offset estimating of CP during smaller or equal to the 3rd handoff threshold.

Preferably, the frequency deviation estimating modules of described CP comprises:

The CP correlation unit is used for the data of the OFDM symbol in each subframe of digital signal are done the CP relevant treatment, obtains the CP correlated results of OFDM symbol correspondence;

The unit that adds up, the CP correlated results of the OFDM symbol correspondence in the subframe that is used to add up obtains corresponding accumulated value;

CP frequency offset calculation unit is used for calculating according to the time interval of described accumulated value, CP, obtains the CP frequency offset estimating value of current subframe;

The first smothing filtering unit is used for the CP frequency offset estimating value of current subframe and the CP frequency offset estimation result of last subframe are carried out smoothing processing, obtains the CP frequency offset estimation result of current subframe.

Preferably, the frequency deviation estimating modules of described RS comprises:

Channel estimating unit is used for the frequency pilot sign that sends according to current base station, and the RS symbol of the current subframe obtained is carried out channel estimating;

The RS correlation unit is used for the RS symbol that carries out the current subframe after the channel estimating is carried out relevant treatment, obtains corresponding correlated results;

RS frequency offset calculation unit is used for calculating according to the time interval of described correlated results, RS, obtains the RS frequency offset estimating value of current subframe;

The second smothing filtering unit is used for the RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtains the RS frequency offset estimation result of current subframe.

The frequency deviation estimating method of a kind of long evolving system LTE comprises:

Obtain baseband signal, make described baseband signal, obtain corresponding digital signal through analog-to-digital conversion;

When described digital signal is carried out the frequency offset estimating of Cyclic Prefix part CP, obtain the frequency offset estimation result of corresponding CP;

To after analog-to-digital conversion, the described digital signal of obtaining goes CP to handle, and obtains the time-domain signal of orthogonal frequency division multiplex OFDM symbol;

Extract the reference signal RS in the frequency-region signal that described time-domain signal obtains after fast Fourier transform, carry out frequency offset estimating, obtain the frequency offset estimation result of RS;

According to default frequency deviation switching condition, select the frequency offset estimation result of described CP or the frequency offset estimation result of described RS to carry out the frequency deviation calibration.

Preferably, described foundation is preset the frequency deviation switching condition, and the detailed process of selecting the frequency offset estimation result of the frequency offset estimation result of described CP or described RS to carry out the frequency deviation calibration comprises:

When the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP smaller or equal to second handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the RS of current subframe and the RS of last subframe switches to the frequency offset estimating of RS during smaller or equal to first handoff threshold;

When the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP more than or equal to the 4th handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the CP of current subframe and the CP of last subframe switches to the frequency offset estimating of CP during smaller or equal to the 3rd handoff threshold.

Preferably, the detailed process of obtaining the frequency offset estimation result of corresponding CP comprises:

Data to the OFDM symbol in each subframe in the digital signal that receives are done the CP relevant treatment, obtain the CP correlated results of OFDM symbol correspondence;

The CP correlated results of the OFDM symbol correspondence in the subframe that adds up obtains corresponding accumulated value;

The time interval according to described accumulated value, CP calculates, and obtains the CP frequency offset estimating value of current subframe;

The CP frequency offset estimating value of current subframe and the CP frequency offset estimation result of last subframe are carried out smoothing processing, obtain the CP frequency offset estimation result of current subframe.

Preferably, the detailed process of the frequency offset estimation result of the described RS of obtaining comprises:

The frequency pilot sign that sends according to current base station carries out channel estimating to the RS symbol of the current subframe obtained;

RS symbol to the current subframe after the channel estimating carries out relevant treatment, obtains corresponding correlated results;

The time interval according to described correlated results, RS calculates, and obtains the RS frequency offset estimating value of current subframe;

The RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtain the RS frequency offset estimation result of current subframe.

Via above-mentioned technical scheme as can be known, compared with prior art, the invention discloses the frequency deviation estimation device and the method for a kind of LTE system, obtain the frequency offset estimation result of the CP of current subframe by calculating, and the frequency offset estimation result of the RS of current subframe, carry out in the LTE system in the process of frequency offset estimating, the concrete condition current according to LTE switched the frequency offset estimation result of CP of current subframe and the frequency offset estimation result of RS and carried out the frequency deviation calibration.So that when being implemented in assurance and carrying out frequency offset estimating on a large scale, obtain the purpose of high-precision frequency offset estimating; Realization guarantees to obtain the purpose of bigger frequency offset estimation range when obtaining high-precision frequency offset estimating.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is embodiments of the invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other embodiment according to the accompanying drawing that provides.

Fig. 1 is radio frames schematic diagram that meets the LTE definition in the prior art;

Fig. 2 is time domain OFDM schematic symbol diagram that meets the LTE definition in the prior art;

Fig. 3 is frequency-domain OFDM schematic symbol diagram that meets the LTE definition in the prior art;

Fig. 4 is the reference signal configuration pattern diagram of eNodeB end antenna port 0;

Fig. 5 is the structural representation of the frequency deviation estimation device of the disclosed a kind of LTE of the embodiment of the invention;

Fig. 6 is the structural representation of the frequency offset estimating of the disclosed CP of the embodiment of the invention;

Fig. 7 is the structural representation of the frequency offset estimating of the disclosed RS of the embodiment of the invention;

Fig. 8 is the flow chart of the frequency deviation estimating method of the disclosed a kind of LTE of the embodiment of the invention;

Fig. 9 is the flow chart that the disclosed frequency deviation of the embodiment of the invention is switched.

Embodiment

For quote and know for the purpose of, the hereinafter explanation of the technical term of Shi Yonging, write a Chinese character in simplified form or abridge and be summarized as follows:

LTE:Long Term Evolution system, long evolving system;

OFDM:Orthogonal Frequency Division Multiplexing, OFDM;

FFT:Fast Fourier Transformation, fast Fourier transform;

CP:Cyclic Prefix, Cyclic Prefix;

RS:Reference Signal, reference signal;

CFO:Carrier Frequency Offset, carrier wave frequency deviation;

ADC:Analog-to-Digital Converter, A/D converter.

Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.

By background technology as can be known, LTE system frequency deviation estimating method commonly used in the prior art, if guarantee high frequency offset estimation accuracy, its scope of carrying out frequency offset estimating can be very little; If guarantee to carry out frequency offset estimating on a large scale, its precision of carrying out frequency offset estimating will reduce.

Therefore, the invention provides frequency deviation estimation device new among the LTE and the method for being applied to, obtain the frequency offset estimation result of the CP of current subframe by calculating, and the frequency offset estimation result of the RS of current subframe, in the LTE system, carry out in the process of frequency offset estimating, the concrete condition current according to LTE switched the frequency offset estimation result of CP of current subframe and the frequency offset estimation result of RS and carried out the frequency deviation calibration.So that when being implemented in assurance and carrying out frequency offset estimating on a large scale, obtain the purpose of high-precision frequency offset estimating.Detailed process describes by following examples.

Embodiment one

As shown in Figure 5, structural representation for the frequency deviation estimation device of the disclosed LTE of the embodiment of the invention, mainly comprise: receiver module 501,, ADC module 502, go the frequency deviation estimating modules 507 of CP module 503, FFT module 504, the frequency deviation estimating modules 506 of extracting RS module 505, CP, RS and frequency deviation to select module 508.

Receiver module 501 is used to receive data and handles, and obtains required baseband signal.These data can be based on the data that reception antenna receives, and at this moment, this receiver module 501 is a receiving front-end module.

ADC module 502 links to each other with receiver module 501, and the baseband signal that is used for receiver module 501 is got access to is carried out sample quantization and analog-to-digital conversion, the digital signal that output is corresponding.

Need to prove,, send to the frequency deviation estimating modules 506 of CP simultaneously and go CP module 503 through the digital signal of ADC module 502 back outputs.

The frequency deviation estimating modules 506 of CP is used to receive the digital signal that ADC module 502 is exported, and to carry out the frequency offset estimating based on CP through the digital signal of exporting after the analog-to-digital conversion, obtains the frequency offset estimation result Δ f of the CP of corresponding current subframe _CP

Go CP module 503, be used for obtaining the time-domain signal of orthogonal frequency division multiplex OFDM symbol going CP to handle through the digital signal of exporting after the analog-to-digital conversion.In the present embodiment, be mainly used in the processing of removing CP, obtain the time-domain signal of an OFDM symbol via the digital signal of ADC module 502 outputs.

FFT module 504 is used for the time-domain signal that removes the OFDM symbol that CP module 503 obtains is carried out fast Fourier transform, obtains corresponding frequency-region signal.

Extract RS module 505, be used for extracting RS symbol through the frequency-region signal that obtains after the FFT module 504.

The frequency deviation estimating modules 507 of RS is used to estimate extract the frequency deviation of the RS symbol of RS module 505 outputs, obtains the frequency offset estimation result Δ f of RS _RS

Frequency deviation is selected module 508, is used for according to default frequency deviation switching condition, from the frequency offset estimation result Δ f of the CP of frequency deviation estimating modules 506 outputs of CP _CP, and the frequency offset estimation result Δ f of the RS of frequency deviation estimating modules 507 outputs of RS _RSThe frequency deviation result that middle selection satisfies condition returns receiver module 501 places and carries out the frequency deviation calibration.

In the process of practical application, the signal flow between disclosed each module of the invention described above embodiment is to being: from the data that antenna 509 receives, processing obtains baseband signal through receiver module 501 (receiving front-end module); Again through exporting digital signal after ADC module 502 sample quantizations; This digital signal obtains the time-domain signal of an OFDM symbol after past CP module 503; Again through obtaining frequency-region signal after the FFT module 504; Then, obtain the RS symbol, then, through carrying out frequency offset estimating, finally obtain frequency offset estimation result Δ f again based on RS based on the frequency deviation estimating modules 507 of RS by extracting RS module 505 modules _RS

Simultaneously, when ADC module 502 output digital signals, also the digital signal that gets access to is sent to frequency deviation estimating modules 506, obtains frequency offset estimation result Δ f based on CP based on CP _CP

Finally, select module 508 according to the frequency deviation switching condition by frequency deviation, and current frequency offset estimation result, from Δ f _CPWith Δ f _RSChoose a suitable frequency deviation as a result Δ f deliver to receiver module 501, carry out relevant frequency deviation calibration.

Need to prove, as shown in Figure 6, comprise in the frequency deviation estimating modules 506 based on described CP: CP correlation unit 601, the unit 602 that adds up, CP frequency offset calculation unit 603 and the first smothing filtering unit 604.

Wherein, CP correlation unit 601 is used for the data of the OFDM symbol in each subframe of digital signal are done the CP relevant treatment, obtains the CP correlated results of OFDM symbol correspondence.

Be specially:

The data of i OFDM symbol in the subframe of the digital signal that obtains from the ADC module comprise: x (0) ...., x (N), (1) carries out the CP relevant treatment according to the following equation, obtains the cp_corr_result_symbol as a result (i) of CP relevant treatment.Wherein, to first OFDM symbol of each time slot, N=2048+160; To other OFDM symbols, N=2048+144

$\mathrm{cp}\_\mathrm{corr}\_\mathrm{result}\_\mathrm{symbol}\left(i\right)=\underset{j=0}{\overset{T_{\mathrm{CP}}}{\mathrm{\Σ}}}x\left(j\right)*x^{*}(T_{\mathrm{Data}}+j)---\left(1\right)$

The unit 602 that adds up, the CP correlated results of the OFDM symbol correspondence in the subframe that is used to add up obtains corresponding accumulated value cp_corr_result.

Be specially:

According to formula (2) the CP correlated results in the subframe of obtaining in the above-mentioned CP correlation unit 601 is added up, obtain cp_corr_result.

$\mathrm{cp}\_\mathrm{corr}\_\mathrm{result}=\underset{i=0}{\overset{14}{\mathrm{\Σ}}}\mathrm{cp}\_\mathrm{corr}\_\mathrm{result}\_\mathrm{symbol}\left(i\right)---\left(2\right)$

CP frequency offset calculation unit 603 is used for calculating according to the time interval of described accumulated value, CP, obtains the CP frequency offset estimating value Δ f of current subframe _{CP_Curr}

Be specially:

According to the CP frequency deviation of the current subframe of formula (3) calculating, obtain the frequency offset estimating value Δ f of current subframe _{CP_Curr}

$\mathrm{\Δ}{f}_{\mathrm{CP}\_\mathrm{Curr}}=\frac{\mathrm{angle}(\mathrm{cp}\_\mathrm{corr}\_\mathrm{result})}{2*\mathrm{\π}*\mathrm{\Δ}{t}_{\mathrm{CP}}}---\left(3\right)$

Wherein, angle () is the function that calculates angle, Δ t _CPBe the time interval of CP, Δ t generally speaking _CP=0.067ms.

The first smothing filtering unit 604 is used for the CP frequency offset estimating value Δ f to current subframe _{CP_Curr}Carry out smoothing processing with the CP frequency offset estimation result of last subframe, obtain the CP frequency offset estimation result Δ f of current subframe _CP

Be specially:

The Δ f that obtains based on CP frequency offset calculation unit 603 _{CP_Curr}, with the CP frequency offset estimation result of last subframe, carry out The disposal of gentle filter according to formula (4), finally obtain the CP frequency offset estimation result Δ f of current subframe _CP

Δf _CP(n)＝(1-α)*Δf _CP(n-1)+α*Δf _{CP_Curr} (4)

Wherein, α is a smoothing factor.

By the processing successively of above-mentioned CP correlation unit 601, the unit 602 that adds up, the 604 pairs of digital signals in the CP frequency offset calculation unit 603 and the first smothing filtering unit, finally can obtain the CP frequency offset estimation result Δ f of current subframe _CP

Need to prove, as shown in Figure 7, comprise in the frequency deviation estimating modules 507 based on described RS: channel estimating unit 701, RS correlation unit 702, RS frequency offset calculation unit 703 and the second smothing filtering unit 704.

Channel estimating unit 701 is used for the frequency pilot sign that sends according to current base station, and the RS symbol of the current subframe obtained is carried out channel estimating.

Be specially:

Obtain the RS symbol of current subframe from extracting the RS module, this RS symbolic representation be rs (i, j), (i=0,1,2,3 is the time-domain position of RS, Frequency domain position for RS); Do channel estimation process according to formula (5) then.

$h(i,j)=\frac{\mathrm{rs}(i,j)}{\mathrm{rs}\_\mathrm{seq}(i,j)}---\left(5\right)$

Wherein, (i j) is illustrated in (i, j) frequency pilot sign of base station, position transmission to rs_seq.

RS correlation unit 702 is used for the RS symbol that carries out the current subframe after the channel estimating is carried out relevant treatment, obtains corresponding correlated results rs_corr_result.

Be specially:

(i, j) by formula (6) do the RS relevant treatment to the signal results estimated h that RS correlation unit 702 obtains after for channel estimation unit 701, obtain rs_corr_result.

$\mathrm{rs}\_\mathrm{corr}\_\mathrm{result}=\underset{j=0}{\overset{2*N_{\mathrm{RB}}^{\mathrm{DL}}}{\mathrm{\Σ}}}j(0,j)*h^{*}(2,j)+\underset{j=0}{\overset{2*N_{\mathrm{RB}}^{\mathrm{DL}}}{\mathrm{\Σ}}}h(1,j)*h^{*}(3,j)---\left(6\right)$

RS frequency offset calculation unit 703 is used for calculating according to the time interval of described correlated results rs_corr_result, RS, obtains the RS frequency offset estimating value Δ f of current subframe _{RS_Curr}

Be specially:, obtain the frequency offset estimating value Δ f of current subframe according to the frequency deviation of formula (7) calculating RS _{RS_Curr}

$\mathrm{\Δ}{f}_{\mathrm{RS}\_\mathrm{Curr}}=\frac{\mathrm{angle}(\mathrm{rs}\_\mathrm{corr}\_\mathrm{result})}{2*\mathrm{\π}*{\mathrm{\Δt}}_{\mathrm{RS}}}---\left(7\right)$

Wherein, angle () is the function that calculates angle, Δ t _RSBe the time interval of RS, Δ t generally speaking _RS=0.5ms.

The second smothing filtering unit 704 is used for the RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtains the RS frequency offset estimation result Δ f of current subframe _RS

Be specially:

The Δ f that obtains based on RS frequency offset calculation unit 703 _{RS_Curr}, with the RS frequency offset estimation result of last subframe, carry out The disposal of gentle filter according to formula (8), finally obtain the RS frequency offset estimation result Δ f of current subframe _RS

Δf _RS(n)＝(1-β)*Δf _RS(n-1)+β*Δf _{RS_Curr} (8)

Wherein, β is a smoothing factor.

RS symbol by above-mentioned channel estimating unit 701, RS correlation unit 702, RS frequency offset calculation unit 703 and the 704 pairs of extractions in the second smothing filtering unit is handled, and finally can obtain the RS frequency offset estimation result Δ f of current subframe _RS

Need to prove, in the frequency deviation estimating modules 506 of above-mentioned CP, obtain the frequency offset estimation result Δ f of corresponding CP _CP, and the frequency offset estimation result Δ f that in the frequency deviation estimating modules 507 of RS, obtains corresponding RS _RSAfterwards, select module 508 from Δ f by frequency deviation _CPWith Δ f _RSChoose a suitable frequency offset estimation result Δ f and deliver to receiver module 501 execution frequency deviation calibrations, be specially:

Generally speaking, when portable terminal brought into operation, frequency deviation was general bigger, the fixing Δ f=Δ f that adopts _CPThen, after operation a period of time, satisfy the first frequency deviation switching condition or the second frequency deviation switching condition at Δ f=Δ f according to whether _CPWith Δ f=Δ f _RSBetween switch, promptly from Δ f _CPWith Δ f _RSChoose a suitable frequency offset estimation result Δ f and go to carry out the frequency deviation calibration.

The first frequency deviation switching condition specifically describe for example for: a continuous N subframe satisfies formula (9) and (10).

abs(Δf _RS(n)-Δf _RS(n-1))＜＝Threhold1 (9)

abs(Δf _RS(n)-Δf _CP(n))＜＝Threhold2 (10)

Wherein, abs () is a function of asking absolute value, and Threhold1 is first handoff threshold, and Threhold2 is second handoff threshold.More stable by the frequency offset estimation result that is based on RS that formula (9) and (10) are represented, and and the frequency offset estimation result of CP more approaching.Therefore, switch to the accuracy that can improve estimation based on the frequency offset estimation result of RS this moment.

The second frequency deviation switching condition specifically describe for example for: a N continuous subframe satisfies formula (11) and (12).

abs(Δf _CP(n)-Δf _CP(n-1))＜＝Threhold3 (11)

abs(Δf _RS(n)-Δf _CP(n))＞＝Threhold4 (12)

Wherein, abs () is a function of asking absolute value, and Threhold3 is the 3rd handoff threshold, and Threhold4 is the 4th handoff threshold.More stable by the frequency offset estimation result that is based on CP that formula (11) and formula (12) are represented, and and the estimated result of RS differs bigger, this moment, actual frequency deviation exceeded the estimation range based on the frequency offset estimating of RS, need switch to the frequency offset estimating based on CP.

That is to say, in described frequency deviation handover module 508, comprise: first switch unit and second switch unit (not marking in the diagram).

First switch unit is used for the frequency offset estimation result Δ f as the described RS of current subframe _RS(n) with the frequency offset estimation result difference DELTA f of CP _CP(n) absolute value is smaller or equal to second handoff threshold, and the frequency offset estimation result Δ f of the RS of current subframe _RS(n) with the frequency offset estimation result Δ f of the RS of last subframe _RSWhen (n-1) absolute value of difference is smaller or equal to first handoff threshold, switch to the frequency offset estimating of RS.Promptly utilize the frequency offset estimation result Δ f of RS _RSThe calibration of execution frequency deviation.

Second switch unit is used for the frequency offset estimation result Δ f as the described RS of current subframe _RS(n) with the frequency offset estimation result difference DELTA f of CP _CP(n) absolute value is more than or equal to the 4th handoff threshold, and the frequency offset estimation result Δ f of the CP of current subframe _CP(n) with the frequency offset estimation result Δ f of the CP of last subframe _CPWhen (n-1) absolute value of difference is smaller or equal to the 3rd handoff threshold, switch to the frequency offset estimating of CP.Promptly utilize the frequency offset estimation result Δ f of CP _CPThe calibration of execution frequency deviation.

By the result of the invention described above embodiment according to current frequency offset estimating, switch between based on the frequency offset estimation result of CP and frequency offset estimation result or select based on RS, by the process of selecting or switching, making current frequency offset estimation result of going to carry out the frequency deviation calibration is current more excellent selection.Promptly in conjunction with the disclosed device of the invention described above, by carrying out switching controls based on the frequency offset estimating of CP with based on the frequency offset estimating of RS, so that obtain bigger frequency offset estimation range and compare high estimation accuracy, when being implemented in assurance and carrying out frequency offset estimating on a large scale, obtain the purpose of high-precision frequency offset estimating; Realization guarantees to obtain the purpose of bigger frequency offset estimation range when obtaining high-precision frequency offset estimating.

Describe the frequency deviation estimation device of a kind of LTE system among the disclosed embodiment of the invention described above in detail, for device disclosed in this invention, the present invention is also corresponding to disclose the frequency deviation estimating method of a kind of LTE system, provides specific embodiment below and is elaborated.

As shown in Figure 8, the flow chart for the frequency deviation estimating method of the disclosed a kind of LTE of the embodiment of the invention mainly may further comprise the steps:

Step S101 obtains baseband signal, makes described baseband signal through analog-to-digital conversion, obtains corresponding digital signal.

Step S102 when described digital signal is carried out the frequency offset estimating of Cyclic Prefix part CP, obtains the frequency offset estimation result Δ f of corresponding CP _CP

Step S103, to after analog-to-digital conversion, the described digital signal of obtaining goes CP to handle, and obtains the time-domain signal of OFDM symbol.

Step S104 extracts the reference signal RS in the frequency-region signal that described time-domain signal obtains after fast Fourier transform, carry out frequency offset estimating, obtains the frequency offset estimation result Δ f of RS _RS

Step S105 according to default frequency deviation switching condition, selects the frequency offset estimation result of described CP or the frequency offset estimation result of described RS to carry out the frequency deviation calibration.

Need to prove, the disclosed device of the corresponding the invention described above embodiment of the disclosed method of the invention described above embodiment, the concrete principle of carrying out is close with content can carry out reference each other.

Obtain the frequency offset estimation result Δ f of CP at execution in step S102 _CP, there is the process of the frequency deviation estimating modules of corresponding above-mentioned CP equally:

At first, the data of the OFDM symbol in each subframe in the digital signal that receives are done the CP relevant treatment, obtain the CP correlated results cp_corr_result_symbol (i) of OFDM symbol correspondence.This process can be referring to formula (1).

Then, the CP correlated results of the OFDM symbol correspondence in the subframe that adds up obtains corresponding accumulated value cp_corr_result.This process can be referring to formula (2).

Calculate according to the time interval of described accumulated value, CP again, obtain the CP frequency offset estimating value Δ f of current subframe _{CP_Curr}This process can be referring to formula (3).

At last, to the CP frequency offset estimating value Δ f of current subframe _{CP_Curr}Carry out smoothing processing with the CP frequency offset estimation result of last subframe, obtain the CP frequency offset estimation result Δ f of current subframe _CPThis process can be referring to formula (4).

Same, obtain the frequency offset estimation result Δ f of CP at execution in step S104 _CP, also there is the process of the frequency deviation estimating modules of corresponding above-mentioned RS:

At first, the frequency pilot sign that sends according to current base station carries out channel estimating to the RS symbol of the current subframe obtained.This process can be referring to formula (5).

Then, the RS symbol of the current subframe after the channel estimating is carried out relevant treatment, obtain corresponding correlated results rs_corr_result.This process can be referring to formula (6).

Calculate according to the time interval of described correlated results, RS again, obtain the RS frequency offset estimating value Δ f of current subframe _{RS_Curr}This process can be referring to formula (7).

At last, the RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtain the RS frequency offset estimation result Δ f of current subframe _RSThis process can be referring to formula (8).

Same, when execution in step S105 carries out the frequency deviation switching, also there is the process of corresponding above-mentioned frequency deviation handover module, as shown in Figure 9:

Step S201 determines the current Δ f=Δ f that carries out the frequency deviation calibration _CP, promptly current frequency offset estimation result is the frequency offset estimation result Δ f of CP _CP

Step S202 judges that whether the frequency offset estimating of current LTE system satisfies the first frequency deviation switching condition, if, execution in step S203 then; If not, then continue execution in step S201.

Step S203 switches the current Δ f=Δ f that carries out the frequency deviation calibration _RS, promptly current frequency offset estimation result is the frequency offset estimation result Δ f of RS _RS

Wherein, the first frequency deviation switching condition can be specially referring to formula (9) and (10):

Frequency offset estimation result Δ f as the described RS of current subframe _RS(n) with the frequency offset estimation result difference DELTA f of CP _CP(n) absolute value is smaller or equal to second handoff threshold, and the frequency offset estimation result Δ f of the RS of current subframe _RS(n) with the frequency offset estimation result Δ f of the RS of last subframe _RSWhen (n-1) absolute value of difference is smaller or equal to first handoff threshold, switch to the frequency offset estimating of RS.Promptly utilize the frequency offset estimation result Δ f of RS _RSThe calibration of execution frequency deviation.

Step S204 continues to judge whether the frequency offset estimating of current LTE system satisfies the second frequency deviation switching condition, if then return execution in step S201; If not, then continue execution in step S203.

Wherein, the second frequency deviation switching condition can be specially referring to formula (11) and (12):

Frequency offset estimation result Δ f as the described RS of current subframe _RS(n) with the frequency offset estimation result difference DELTA f of CP _CP(n) absolute value is more than or equal to the 4th handoff threshold, and the frequency offset estimation result Δ f of the CP of current subframe _CP(n) with the frequency offset estimation result Δ f of the CP of last subframe _CPWhen (n-1) absolute value of difference is smaller or equal to the 3rd handoff threshold, switch to the frequency offset estimating of CP.Promptly utilize the frequency offset estimation result Δ f of CP _CPThe calibration of execution frequency deviation.

In sum:

Frequency deviation estimation device and method by the disclosed LTE of the invention described above embodiment system, obtain the frequency offset estimation result of the CP of current subframe by calculating, and the frequency offset estimation result of the RS of current subframe, in the LTE system, carry out in the process of frequency offset estimating, the concrete condition current according to LTE switched the frequency offset estimation result of CP of current subframe and the frequency offset estimation result of RS and carried out the frequency deviation calibration.So that when being implemented in assurance and carrying out frequency offset estimating on a large scale, obtain the purpose of high-precision frequency offset estimating; Realization guarantees to obtain the purpose of bigger frequency offset estimation range when obtaining high-precision frequency offset estimating.

Each embodiment adopts the mode of going forward one by one to describe in this specification, and what each embodiment stressed all is and the difference of other embodiment that identical similar part is mutually referring to getting final product between each embodiment.For the disclosed device of embodiment, because it is corresponding with the embodiment disclosed method, so description is fairly simple, relevant part partly illustrates referring to method and gets final product.

The method of describing in conjunction with embodiment disclosed herein or the step of algorithm can directly use the software module of hardware, processor execution, and perhaps the combination of the two is implemented.Software module can place the storage medium of any other form known in random asccess memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable ROM, register, hard disk, moveable magnetic disc, CD-ROM or the technical field.

To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the present invention.Multiple modification to these embodiment will be conspicuous concerning those skilled in the art, and defined herein General Principle can realize under the situation that does not break away from the spirit or scope of the present invention in other embodiments.Therefore, the present invention will can not be restricted to these embodiment shown in this article, but will meet and principle disclosed herein and features of novelty the wideest corresponding to scope.

Claims (8)

1. the frequency deviation estimation device of a long evolving system LTE is characterized in that, comprising:

The frequency deviation estimating modules of Cyclic Prefix part CP is used for obtaining the frequency offset estimation result of the CP of corresponding current subframe to carry out the frequency offset estimating based on CP through the digital signal of exporting after the analog-to-digital conversion;

Go the CP module, be used for obtaining the time-domain signal of orthogonal frequency division multiplex OFDM symbol going CP to handle through the digital signal of exporting after the analog-to-digital conversion;

Extract reference signal RS module, be used for extracting the RS symbol of the frequency-region signal of described time-domain signal after fast Fourier transform;

The frequency deviation estimating modules of RS is used to obtain the frequency offset estimation result of described RS;

The frequency deviation handover module is used for according to default frequency deviation switching condition, selects the frequency offset estimation result of described CP or the frequency offset estimation result of described RS to carry out the frequency deviation calibration.

2. device according to claim 1 is characterized in that, described frequency deviation handover module comprises:

First switch unit, be used for absolute value when the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP smaller or equal to second handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the RS of current subframe and the RS of last subframe switches to the frequency offset estimating of RS during smaller or equal to first handoff threshold;

Second switch unit, be used for absolute value when the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP more than or equal to the 4th handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the CP of current subframe and the CP of last subframe switches to the frequency offset estimating of CP during smaller or equal to the 3rd handoff threshold.

3. device according to claim 1 is characterized in that, the frequency deviation estimating modules of described CP comprises:

The CP correlation unit is used for the data of the OFDM symbol in each subframe of digital signal are done the CP relevant treatment, obtains the CP correlated results of OFDM symbol correspondence;

The unit that adds up, the CP correlated results of the OFDM symbol correspondence in the subframe that is used to add up obtains corresponding accumulated value;

CP frequency offset calculation unit is used for calculating according to the time interval of described accumulated value, CP, obtains the CP frequency offset estimating value of current subframe;

The first smothing filtering unit is used for the CP frequency offset estimating value of current subframe and the CP frequency offset estimation result of last subframe are carried out smoothing processing, obtains the CP frequency offset estimation result of current subframe.

4. device according to claim 1 is characterized in that, the frequency deviation estimating modules of described RS comprises:

Channel estimating unit is used for the frequency pilot sign that sends according to current base station, and the RS symbol of the current subframe obtained is carried out channel estimating;

The RS correlation unit is used for the RS symbol that carries out the current subframe after the channel estimating is carried out relevant treatment, obtains corresponding correlated results;

RS frequency offset calculation unit is used for calculating according to the time interval of described correlated results, RS, obtains the RS frequency offset estimating value of current subframe;

The second smothing filtering unit is used for the RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtains the RS frequency offset estimation result of current subframe.

5. the frequency deviation estimating method of a long evolving system LTE is characterized in that, comprising:

Obtain baseband signal, make described baseband signal, obtain corresponding digital signal through analog-to-digital conversion;

When described digital signal is carried out the frequency offset estimating of Cyclic Prefix part CP, obtain the frequency offset estimation result of corresponding CP;

To after analog-to-digital conversion, the described digital signal of obtaining goes CP to handle, and obtains the time-domain signal of orthogonal frequency division multiplex OFDM symbol;

Extract the reference signal RS in the frequency-region signal that described time-domain signal obtains after fast Fourier transform, carry out frequency offset estimating, obtain the frequency offset estimation result of RS;

According to default frequency deviation switching condition, select the frequency offset estimation result of described CP or the frequency offset estimation result of described RS to carry out the frequency deviation calibration.

6. method according to claim 5 is characterized in that, described foundation is preset the frequency deviation switching condition, and the detailed process of selecting the frequency offset estimation result of the frequency offset estimation result of described CP or described RS to carry out the frequency deviation calibration comprises:

When the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP smaller or equal to second handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the RS of current subframe and the RS of last subframe switches to the frequency offset estimating of RS during smaller or equal to first handoff threshold;

When the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the described RS of current subframe and CP more than or equal to the 4th handoff threshold, and the absolute value of the frequency offset estimation result difference of the frequency offset estimation result of the CP of current subframe and the CP of last subframe switches to the frequency offset estimating of CP during smaller or equal to the 3rd handoff threshold.

7. according to claim 5 or 6 described methods, it is characterized in that the detailed process of obtaining the frequency offset estimation result of corresponding CP comprises:

Data to the OFDM symbol in each subframe in the digital signal that receives are done the CP relevant treatment, obtain the CP correlated results of OFDM symbol correspondence;

The CP correlated results of the OFDM symbol correspondence in the subframe that adds up obtains corresponding accumulated value;

The time interval according to described accumulated value, CP calculates, and obtains the CP frequency offset estimating value of current subframe;

The CP frequency offset estimating value of current subframe and the CP frequency offset estimation result of last subframe are carried out smoothing processing, obtain the CP frequency offset estimation result of current subframe.

8. according to claim 5 or 6 described methods, it is characterized in that the detailed process of the frequency offset estimation result of the described RS of obtaining comprises:

The frequency pilot sign that sends according to current base station carries out channel estimating to the RS symbol of the current subframe obtained;

RS symbol to the current subframe after the channel estimating carries out relevant treatment, obtains corresponding correlated results;

The time interval according to described correlated results, RS calculates, and obtains the RS frequency offset estimating value of current subframe;

The RS frequency offset estimating value of current subframe and the RS frequency offset estimation result of last subframe are carried out smoothing processing, obtain the RS frequency offset estimation result of current subframe.

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