CN101552635B - Method and device for capturing frequency deviation - Google Patents

Abstract

The present invention discloses a method and a device for capturing frequency deviation. The method is applied for the 3rd generation partnership project 3GPP Long Term Evolution 3GPP LTE system and comprises the following steps: executing time synchronization to the received signal sequence for confirming the position of synchronizing signal; obtaining the master synchronizing signal and auxiliary synchronizing signal of synchronizing signal in frequency domain; respectively executing channel estimation with the master synchronizing signal and auxiliary synchronizing signal for respectively obtaining the estimated values of time domain channel response at the positions of master synchronizing signal and auxiliary synchronizing signal; and calculating the frequency deviation with the phasedifference between the estimated values of time domain channel response at the positions of master synchronizing signal and auxiliary synchronizing signal. The method and the device according to the invention can greatly increase the precision of prior frequency deviation capturing for satisfying the frequency deviation estimation range of frequency deviation tracking period thereby effectively increasing the demodulation performance of link circuit.

Description

A kind of method of capturing frequency deviation and device

Technical field

The present invention relates to communication technique field, (The 3 to refer in particular to a kind of 3GPP of being applied to LTE ^RdGeneration Partner Project Long term evolution, third generation gpp Long Term Evolution) method and apparatus of the capturing frequency deviation in the system.

Background technology

Along with the development and the development of technology of society, people improve constantly the requirement of mobile communication, hope that system can provide the data transport service of big capacity, two-forty, low delay.In order to satisfy this growing demand.The 3GPP tissue has proposed the Long Term Evolution plan (LTE) of 3G system.The LTE system adopts OFDM (Orthogonal Frequency Division Multiplexing; OFDM) transmission technology; Under the OFDM transmission technology, system adopts the carrier wave of mutually orthogonal, has improved spectrum efficiency and the system robustness to frequency-selective channel.Yet as cost, this system is relatively more responsive for the frequency shift (FS) between the transceiver for single-carrier system.

The technology of slightly searching of existing OFDM sub-district mainly is divided into two types: auto-correlation and cross-correlation.Autocorrelative a kind of typical technology is in transmitting, to insert some to be used for synchronous signal; Making transmits shows as the segment signal with repetition on time domain; WLAN (Wireless Local Area Network for example; Radio Access Network) and the long and short leading training sequence (preamble) in WIMAX (World Interoperability for Microwave Access, the World Interoperability for Microwave Access, WiMax) system, the coherent detection repetitive sequence position of sliding then; Perhaps can utilize the repetitive structure of the intrinsic cyclic prefix CP of ofdm system to detect, utilize the phase difference of rear and front end sequence to carry out frequency offset estimating then; And the typical technology of cross-correlation is a sequence of in transmitting, inserting one group of good relationship, and the relevant sequence position of detecting of slip at receiving terminal utilization reception signal and local signal utilizes the phase difference of sequence rear and front end to carry out frequency offset estimating then.

In addition; In existing LTE system, common frequency offset estimation procedure comprises capturing frequency deviation and two stages of frequency offset tracking, and at present typical capturing frequency deviation technology is to utilize the phase difference of two sections of master sync signal front and back to estimate; The frequency offset estimation range of capturing frequency deviation is usually in 1 carrier spacing; Therefore because the sampling number quantitative limitation, and frequency offset estimation range require limit, cause estimating to catch precision about about 20% carrier spacing.And for the frequency offset tracking process; Prior art is utilized reference signal (RS usually; ReferenceSignal) do Frequency Estimation, because the design of RS in the LTE system, the Frequency Estimation scope in this frequency offset tracking process is usually in the carrier spacing about 14%; Therefore make the capturing frequency deviation and the frequency offset estimation range in two stages of frequency offset tracking finely not to be connected, influence the demodulation performance of link then.

Summary of the invention

The purpose of technical scheme of the present invention provides a kind of method and apparatus of capturing frequency deviation; Adopt said method and apparatus can greatly improve the precision of existing capturing frequency deviation; Satisfying the frequency offset estimation range in frequency offset tracking stage, thereby effectively improve the demodulation performance of link.

For realizing the foregoing invention purpose; The present invention provides a kind of method of capturing frequency deviation; Be applied in the third generation gpp Long Term Evolution 3GPP LTE system, said method comprises the steps: that sequence is carried out time synchronized to received signal, confirms the position of synchronizing signal; According to the system parameters configuration, obtain master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain; Utilize said master sync signal and said auxiliary synchronous signals to carry out channel estimating respectively, obtain the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position respectively; Utilize the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position.

Preferably, above-mentioned described method utilizes the step of the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position specifically to comprise: according to formula $\widehat{\mathrm{\Φ}}=\∠\left[\widehat{H_{j,k}}{\widehat{H_{j+D,k}}}^{*}\right]$ Calculate the phase difference between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position

Wherein: j is the notation index of said master sync signal, and k is the index of subcarrier, and D is the distance between said master sync signal and the said auxiliary synchronous signals;

Domain channel response estimated value for the said master sync signal in j position;

Domain channel response estimated value for said auxiliary synchronous signals position, j position; According to ${\hat{f}}_{\mathrm{\Δ}}=-\frac{1}{2\mathrm{\π\; D}}\widehat{\mathrm{\Φ}}$ The calculated rate skew

Preferably; Above-mentioned described method; The mode that said reception burst is carried out time synchronized comprises: adopt reception burst and local temporal signatures sequence to make the relevant method of slip and carry out time synchronized; Perhaps employing reception burst and the relevant method of local temporal signatures sequence calculating segmented slip are carried out time synchronized, and the method that perhaps adopts the repetitive structure calculating slip of reception burst on time domain to be correlated with is carried out time synchronized.

Preferably, above-mentioned described method, said is to utilize the repeatability of Cyclic Prefix or utilize the repetitive structure that produces under the signal specific at the repetitive structure on the time domain.

Preferably, above-mentioned described method, said method of carrying out channel estimating is least-mean-square error algorithm or least-squares algorithm.

Preferably, above-mentioned described method, said system parameters comprises system pattern and/or sample rate, said system pattern is FDD or TDD pattern.

For realizing the foregoing invention purpose; The present invention also provides a kind of device of capturing frequency deviation on the other hand, is applied to comprise: the synchronizing signal processing unit in the third generation gpp Long Term Evolution 3GPP LTE system; Be used for said reception burst is carried out time synchronized, confirm the position of synchronizing signal; The synchronizing signal acquiring unit is used for obtaining master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain according to the system parameters configuration; Channel estimating unit is used to utilize said master sync signal and said auxiliary synchronous signals to carry out channel estimating respectively, obtains the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position; The Frequency offset estimation unit is used to utilize the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position.

Preferably, above-mentioned described device, said synchronizing signal acquiring unit comprises: the time synchronized subelement, be used to obtain said synchronizing signal processing unit the information of definite synchronizing signal position; Synchronizing signal intercepting subelement is used at said master sync signal of said synchronizing signal intercepting and said auxiliary synchronous signals; The time-domain and frequency-domain converting unit is used for the said master sync signal and the said auxiliary synchronous signals of the intercepting of said synchronizing signal intercepting subelement institute are converted to frequency domain.

Preferably, above-mentioned described device, said channel estimating unit adopts least-mean-square error algorithm or least-squares algorithm to carry out channel estimating.

Preferably; Above-mentioned described device, said synchronizing signal processing unit comprises the method that said reception burst carries out time synchronized: the method that method that the method that employing reception burst is relevant with the slip of local temporal signatures sequence do, employing reception burst are correlated with the slip of local temporal signatures sequence calculating segmented or the repetitive structure calculating slip of employing reception burst on time domain are correlated with.

In the technique scheme at least one has following beneficial effect: said apparatus and method utilize main and auxiliary synchronizing signal in these characteristics of same frequency resource; Respectively main and auxiliary synchronizing signal is carried out channel estimating; The method of only utilizing master sync signal to carry out capturing frequency deviation with respect to prior art has increased the sampled point number that capturing frequency deviation calculates; Therefore can greatly improve the frequency offset estimation accuracy of acquisition phase; Make the capturing frequency deviation and the frequency offset estimation range in two stages of frequency offset tracking realize well being connected, thereby effectively improve the demodulation performance of link.

Description of drawings

Fig. 1 is the sketch map of LTE system frame structure;

Fig. 2 is the synchronizing signal mapping graph of LTE system TDD mode;

Fig. 3 is the synchronizing signal mapping graph of LTE system fdd mode;

Fig. 4 is the flow chart of the said frequency bias capture method of the specific embodiment of the invention;

Fig. 5 is the structure chart of the said capturing frequency deviation device of the specific embodiment of the invention.

Embodiment

For making the object of the invention, technical scheme and advantage clearer, will combine accompanying drawing and specific embodiment to describe the present invention below.

The method of capturing frequency deviation according to the invention and device; Can be applied to TDD (the Time Division Duplexing in the 3GPP LTE system; Time division duplex) pattern and FDD (Frequency DivisionDuplexing; FDD) pattern, main utilization is positioned at the master sync signal at different OFDM character positions place and the channel estimation results of auxiliary synchronous signals carries out capturing frequency deviation, only utilizes master sync signal to carry out the method for capturing frequency deviation with respect to prior art; The present invention adopts the sampled point quantity of the OFDM symbol that is used for capturing frequency deviation calculating to increase, dwindle at interval, therefore can greatly improve the capturing frequency deviation precision.

Fig. 1 is the frame structure sketch map of tdd mode or fdd mode in the LTE system, and wherein the 1st, 6 subframes are used for special subframe under tdd mode.Fig. 2 and Fig. 3 are respectively the sketch map of the synchronizing signal position that is used for representing LTE system tdd mode and fdd mode, can find out in conjunction with Fig. 1, Fig. 2 and Fig. 3, and at tdd mode, 2 OFDM symbol lengths at interval between master sync signal and the auxiliary synchronous signals; At fdd mode, master sync signal and auxiliary synchronous signals are adjacent; In addition, for tdd mode and fdd mode, the cycle that master sync signal occurs all is the time of a field of 5ms.

According to the 3GPP agreement, master sync signal can be employed in the zadoff-chu sequence that time domain and frequency domain all possess extraordinary correlation properties and express, and this zadoff-chu sequence is expressed as formula (1) shown in, and auxiliary synchronous signals can adopt the expression of Gold sequence.

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

Wherein u comprises cell group information.

This zadoff-chu sequence expression formula and Gold sequence expression formula are those skilled in the art's known technology, are not described in detail in this.

Therefore, comprehensively the above, those skilled in the art combine Fig. 1 and Fig. 2, and promptly can in the process of capturing frequency deviation, calculate according to existing known technology and to obtain main and auxiliary synchronizing signal.

Below will be applied to the LTE tdd mode with the method for said capturing frequency deviation and device is example, and the method and the device of the said capturing frequency deviation of the specific embodiment of the invention is elaborated.

Fig. 4 is the schematic flow sheet of the said method of the specific embodiment of the invention, consults Fig. 4, and the method for capturing frequency deviation begins from step S401 in the said LTE system, comprising:

Step S402, sequence is carried out time synchronized to received signal, confirms the position of synchronizing signal;

It will be understood by those skilled in the art that sequence to received signal carries out the method for time synchronized and can have multiplely, receive burst and local temporal signatures sequence to do slip relevant that the time synchronized point is confirmed in the detection peak position afterwards as utilizing; The slip that perhaps utilizes reception burst and local temporal signatures sequence to calculate segmented is relevant, and the time synchronized point is confirmed in the detection peak position; Or utilize the repetitive structure of reception burst on time domain to calculate to slide and be correlated with; The detection peak position; Confirm the time synchronized point, wherein the repetitive structure on this time domain can be a repeatability of utilizing cyclic prefix CP, also can be to utilize the repetitive structure that produces under the signal specific.

Preferably, for fear of the influence of frequency deviation to peak value, the relevant method of slip that the method for the said capturing frequency deviation of the specific embodiment of the invention adopts reception burst and local temporal signatures sequence to calculate segmented is carried out time synchronized.

Step S403 according to the system parameters configuration, obtains master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain;

Before carrying out this step; Each OFDM symbol transition of the synchronizing signal of in advance step S402 being confirmed is to frequency domain, because the method for the said capturing frequency deviation of the specific embodiment of the invention describes with tdd mode, and the rule characteristic of the synchronizing signal position of the tdd mode of therefore representing according to Fig. 1 and Fig. 2; Utilize the system configuration of tdd mode; And, adopt the sample rate of 1.92MHz according to the position of synchronizing signal, obtain 128 synchronizing signals and carry out FFT; Obtain the main and auxiliary synchronizing signal of frequency domain; Begin intercepting Ts data second (this Ts is the length of an OFDM symbol in the LTE system) in the master sync signal position, master sync signal is taken out, two OFDM mark spaces take out corresponding auxiliary synchronous signals at interval simultaneously.

Step S404 utilizes said master sync signal and said auxiliary synchronous signals to carry out channel estimating respectively, obtains the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position respectively.

It will be appreciated by those skilled in the art that; The method of carrying out channel estimating includes least-mean-square error algorithm and least-squares algorithm etc.; The said method of present embodiment is utilized the weighing apparatus width of cloth characteristic of synchronizing signal, utilizes the method for least mean-square error to carry out channel estimating, and promptly formula (2) carries out channel estimating:

$\widehat{H_{n,k}}=R_{n,k}{S}_{n,k}^{*}---\left(2\right)$

Obtain the domain channel response estimated value of master sync signal Domain channel response estimated value with auxiliary synchronous signals Wherein: R _{N, k}Be the acknowledge(ment) signal on the k number of sub-carrier on n the OFDM symbol, S _{N, k} ^*Be transmitting on the k number of sub-carrier on n the OFDM symbol.

Step S405 utilizes the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position.

In the said method of the specific embodiment of the invention; After utilizing formula (2) to calculate acquisition

numerical result, according to the phase difference between the domain channel response estimated value of formula (3) said master sync signal of calculating and said auxiliary synchronous signals position

$\widehat{\mathrm{\Φ}}=\∠\left[\widehat{H_{j,k}}{\widehat{H_{j+D,k}}}^{*}\right]---\left(3\right)$

Wherein: j is the notation index of said master sync signal, and k is the index of subcarrier, and D is the distance between said master sync signal and the said auxiliary synchronous signals, is 3 OFDM symbol lengths in LTE TDD system;

is the domain channel response estimated value of j position master sync signal;

is the domain channel response estimated value of auxiliary synchronous signals position, j position.

After calculating the phase difference

that obtains between

and , according to formula (4) calculated rate skew

${\hat{f}}_{\mathrm{\Δ}}=-\frac{1}{2\mathrm{\πD}}\widehat{\mathrm{\Φ}}---\left(4\right)$

Wherein, D is the distance between said master sync signal and the said auxiliary synchronous signals, in LTE TDD system, also is 3 OFDM symbol lengths.

In addition; For LTE FDD system, those skilled in the art are according to Fig. 1 and Fig. 3, and the combination common practise; Can be informed in the rule characteristic of FDD system master sync signal and auxiliary synchronous signals; Therefore can in the process of capturing frequency deviation, calculate the main and auxiliary synchronizing signal of acquisition, identical under the application principle that in addition the said method of the specific embodiment of the invention is applied to LTE FDD system and the tdd mode, be not described in detail in this.

The specific embodiment of the invention also provides a kind of device of capturing frequency deviation on the other hand, is the structural representation of the said device of the specific embodiment of the invention like Fig. 5.Consult Fig. 5, said device comprises:

Synchronizing signal processing unit 51 is used for said reception burst is carried out time synchronized, confirms the position of synchronizing signal; This synchronizing signal processing unit 51 can adopt reception burst and local temporal signatures sequence to make the relevant method of slip or employing reception burst method or employing reception burst the repetitive structure calculating slip relevant method on time domain relevant with the slip of local temporal signatures sequence calculating segmented carried out time synchronized to said reception burst.

Synchronizing signal acquiring unit 52; Be used for disposing according to system parameters; Obtain master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain; Comprise time synchronized subelement 521, synchronizing signal intercepting subelement 522, time-domain and frequency-domain converting unit 523, wherein time synchronized subelement 521 is used to obtain the information of 51 definite synchronizing signal positions of synchronizing signal processing unit, and synchronizing signal intercepting subelement 522 is used for from the said main and auxiliary synchronizing signal of main and auxiliary synchronizing signal position intercepting; Time-domain and frequency-domain converting unit 523 is used for the main and auxiliary synchronizing signal of 522 interceptings of synchronizing signal intercepting subelement is converted to frequency domain.

The device of the said capturing frequency deviation of the specific embodiment of the invention describes with tdd mode; The rule characteristic of the synchronizing signal position of the tdd mode of therefore representing according to Fig. 1 and Fig. 2; Utilize the system configuration of tdd mode, and, adopt the sample rate of 1.92MHz according to the position of synchronizing signal; Obtain 128 synchronizing signals and carry out FFT, obtain the main and auxiliary synchronizing signal of frequency domain.

Channel estimating unit 53; The said master sync signal and the said auxiliary synchronous signals that are used to utilize the said time-domain and frequency-domain converting unit 523 of process to be converted to frequency domain carry out channel estimating respectively, obtain the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position;

This channel estimating unit 53 method of carrying out channel estimating can adopt least-mean-square error algorithm or least-squares algorithm particularly; The said device of the specific embodiment of the invention can utilize formula (2) to carry out channel estimating, with the domain channel response estimated value

of acquisition master sync signal and the domain channel response estimated value

of auxiliary synchronous signals

Frequency offset estimation unit 54 is used to utilize the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position;

In the said method of the specific embodiment of the invention; After utilizing formula (2) to calculate acquisition

numerical result; Calculate phase difference

between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position according to formula (3) after calculating the phase difference

that obtains between and , according to formula (4) calculated rate squints

Particularly, formula (2), (3), (4) are as implied above, are not described in detail in this.

Comprehensively above-mentioned; Through the said apparatus and method of the specific embodiment of the invention; Utilize main and auxiliary synchronizing signal in these characteristics of identical frequency domain resource, respectively main and auxiliary synchronizing signal is carried out channel estimating, utilize the result of channel estimating to do frequency offset estimating then; Increased the sampled point number that calculates; Therefore can greatly improve the frequency offset estimation accuracy of acquisition phase, can prove that through theory analysis and emulation the method for the invention and device can greatly improve the precision of capturing frequency deviation in addition, thereby can improve systematic function.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; Can also make some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.

Claims (10)

1. the method for a capturing frequency deviation is applied to it is characterized in that said method comprises step in the third generation gpp Long Term Evolution 3GPP LTE system:

Sequence is carried out time synchronized to received signal, confirms the position of synchronizing signal;

According to the system parameters configuration, obtain master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain;

Utilize said master sync signal and said auxiliary synchronous signals to carry out channel estimating respectively, obtain the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position respectively;

Utilize the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position.

2. the method for claim 1 is characterized in that, the step of the phase difference calculating frequency shift (FS) between the said domain channel response estimated value of utilizing said master sync signal and said auxiliary synchronous signals position specifically comprises:

According to formula $\widehat{\mathrm{\Φ}}=\∠\left[\widehat{H_{j,k}}{\widehat{H_{j+D,k}}}^{*}\right]$ Calculate the phase difference between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position

Wherein: j is the notation index of said master sync signal, and k is the index of subcarrier, and D is the distance between said master sync signal and the said auxiliary synchronous signals;

Domain channel response estimated value for the said master sync signal in j position;

Domain channel response estimated value for said auxiliary synchronous signals position, j position;

According to ${\hat{f}}_{\mathrm{\Δ}}=-\frac{1}{2\mathrm{\π\; D}}\widehat{\mathrm{\Φ}}$ The calculated rate skew

3. method as claimed in claim 2; It is characterized in that; The mode that said reception burst is carried out time synchronized comprises: adopt reception burst and local temporal signatures sequence to make the relevant method of slip and carry out time synchronized; Perhaps employing reception burst and the relevant method of local temporal signatures sequence calculating segmented slip are carried out time synchronized, and the method that perhaps adopts the repetitive structure calculating slip of reception burst on time domain to be correlated with is carried out time synchronized.

4. method as claimed in claim 3 is characterized in that, said is to utilize the repeatability of Cyclic Prefix or utilize the repetitive structure that produces under the signal specific at the repetitive structure on the time domain.

5. the method for claim 1 is characterized in that, said method of carrying out channel estimating is least-mean-square error algorithm or least-squares algorithm.

6. the method for claim 1 is characterized in that, said system parameters comprises system pattern and/or sample rate, and said system pattern is FDD pattern or TDD pattern.

7. the device of a capturing frequency deviation is applied to it is characterized in that in the third generation gpp Long Term Evolution 3GPP LTE system, comprising:

The synchronizing signal processing unit is used for said reception burst is carried out time synchronized, confirms the position of synchronizing signal;

The synchronizing signal acquiring unit is used for obtaining master sync signal and the auxiliary synchronous signals of said synchronizing signal at frequency domain according to the system parameters configuration;

Channel estimating unit is used to utilize said master sync signal and said auxiliary synchronous signals to carry out channel estimating respectively, obtains the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position;

The Frequency offset estimation unit is used to utilize the phase difference calculating frequency shift (FS) between the domain channel response estimated value of said master sync signal and said auxiliary synchronous signals position.

8. device as claimed in claim 7 is characterized in that, said synchronizing signal acquiring unit comprises:

The time synchronized subelement, be used to obtain said synchronizing signal processing unit the information of definite synchronizing signal position;

Synchronizing signal intercepting subelement is used at said master sync signal of said synchronizing signal intercepting and said auxiliary synchronous signals;

The time-domain and frequency-domain converting unit is used for the said master sync signal and the said auxiliary synchronous signals of the intercepting of said synchronizing signal intercepting subelement institute are converted to frequency domain.

9. device as claimed in claim 7 is characterized in that, said channel estimating unit adopts least-mean-square error algorithm or least-squares algorithm to carry out channel estimating.

10. device as claimed in claim 7; It is characterized in that said synchronizing signal processing unit comprises the method that said reception burst carries out time synchronized: the method that method that the method that employing reception burst is relevant with the slip of local temporal signatures sequence do, employing reception burst are correlated with the slip of local temporal signatures sequence calculating segmented or the repetitive structure calculating slip of employing reception burst on time domain are correlated with.

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