CN101247383A - Method and device for carrier frequency migration estimation - Google Patents

Abstract

The invention discloses a compensating method and the device for carrier frequency offset. A base station gets R by carrying out the Fourier Transform to the received signal r, carrying out the Fourier Transform to the compensation rate of the phase pushing figure of the r to get a compensation vector C'<i>, getting the signal which gets the compensation of the carrier frequency offset and meets the set conditions after iterative process based on the gotten estimated value of the carrier frequency offset and the compensation vector C'<i>, it is not only carrying out the compensation of the carrier frequency offset based on the carrier frequency offset, but also removes the interference between users, which full considers the interference between users, the invention not only realizes the compensation of the carrier frequency offset, but also removes the interference between users, getting the more accurate estimated value of user's signal.

Description

A kind of method and device that carries out the carrier frequency shift compensation

Technical field

The present invention relates to moving communicating field, be meant a kind of carrier frequency shift (CarrierFrequency Offset, CFO) Bu Chang method and device of carrying out especially.

Background technology

OFDM (Orthogonal Frequency Division Multiplexing, OFDM) transmission technology not only has higher spectrum efficiency, and effectively contrary frequency selectivity decline, be suitable for wideband transmit, be widely used in the various Wireless Broadband Communication Systems.OFDM is a kind of special multi-carrier modulation, total be exactly its main thought in frequency domain with channel distribution become a plurality of subchannels, different subchannel uses different subcarriers to modulate, and overlaps each other between each subcarrier and keeps mutually orthogonal, the parallel transmission.Can effectively resist like this because the frequency selective fading that multidiameter delay causes.

Because each subcarrier of ofdm signal is mutually orthogonal, therefore, ofdm system can effectively utilize frequency spectrum resource, improves the performance and the speed of transfer of data greatly.But, in the practical application, because carrier frequency shift and Doppler effect, destroyed the orthogonality of ofdm signal, cause the phase mutual interference between the subcarrier, cause the performance of whole system seriously to descend, therefore, carrier frequency shift is estimated and then compensate according to the Carrier frequency offset estimation value to be very important.

OFDM inserts (Orthogonal Frequency Division Multiplexing Access, OFDMA) be a kind of multiple access technique based on OFDM, the OFDMA system has identical advantage with ofdm system, as high spectrum utilization, support high-speed transfer and good anti-multipath decline ability.The OFDMA system is identical with ofdm system, and very responsive to carrier frequency shift equally, frequency carrier frequency shift (FS) and Doppler effect are destroyed the orthogonality between the subcarrier, cause the degradation of OFDMA system,

In the up link of OFDMA system, the base station need be handled a plurality of users' upward signal simultaneously, can produce inter-user interference, makes performance further worsen, and therefore, it is exactly very important carrying out the carrier frequency shift compensation according to the Carrier frequency offset estimation value.A kind of processing mode is; each user's Carrier frequency offset estimation value directly be multiply by in the base station to the signal of receiving; carry out the carrier frequency shift compensation; but; can exist between multiple access like this and disturb; in order to reduce to disturb between multiple access; need between each user's subband, insert protection at interval; disturb to reduce; and this processing mode only is applicable to the situation of distributing continuous subcarrier for each user; make that the branch polarity of subcarrier is dumb, can't effectively utilize frequency diversity to improve the performance of OFDMA system.Because the equal factor of different user present position difference, translational speed makes that carrier frequency shift and the Doppler effect between different user and the base station has nothing in common with each other, this compensates carrier frequency shift and has higher requirement.Another kind of processing mode adopts the base station feedback method to carry out the carrier frequency shift compensation, be that the base station is carried out Carrier frequency offset estimation according to the signal of receiving to each user's up link, return the Carrier frequency offset estimation value to each user terminal then, user terminal is according to the Carrier frequency offset estimation value of receiving, the carrier frequency that transmits is adjusted, to realize the carrier frequency shift compensation, reduce the interference that causes owing to carrier frequency shift.Though present scheme can compensate carrier frequency shift, do not consider inter-user interference, make the carrier frequency shift compensation effect not good.

Summary of the invention

In view of this, the embodiment of the invention provides a kind of method and device that carries out the carrier frequency shift compensation, effectively eliminates inter-user interference.

The method that the embodiment of the invention provides carries out the carrier frequency shift compensation comprises: base station r is to received signal carried out Fourier transform and is obtained R; The compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾According to the Carrier frequency offset estimation value that obtains and described compensation vector C ' ⁽ⁱ⁾Be met the signal that imposes a condition through the carrier frequency shift compensation through iterative process.

The device that carries out the carrier frequency shift compensation that the embodiment of the invention provides comprises: compensating unit and interference cancellation unit, wherein, described compensating unit is used for to received signal r to carry out Fourier transform and obtains R, the compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾, according to described compensation vector C ' ⁽ⁱ⁾With the Carrier frequency offset estimation value that obtains each user's signal is carried out the carrier frequency shift compensation, and provide signal through the carrier frequency shift compensation to described interference cancellation unit; The signal through the carrier frequency shift compensation that described interference cancellation unit is used for receiving is met the signal that carried out the carrier frequency migration that imposes a condition through iterative process.

Among the embodiment provided by the invention, the carrier frequency shift compensation is not only carried out according to carrier frequency shift in the base station, also carry out the elimination of inter-user interference according to signal through frequency offset compensation, taken into full account inter-user interference, not only can realize the compensation of carrier frequency shift, can also eliminate inter-user interference, obtain subscriber signal estimated value more accurately.

Description of drawings

Fig. 1 is a CU sub-carrier frequency domain distribution schematic diagram in the embodiment of the invention;

Fig. 2 is an any CU subcarrier situation schematic diagram under the sub-carrier distribution manner in the embodiment of the invention;

Fig. 3 is a carrier frequency shift compensation flow chart in the embodiment of the invention;

Fig. 4 is a base station receiver structural representation in the embodiment of the invention;

Fig. 5 is a CFO compensating unit structural representation in the embodiment of the invention;

Fig. 6 is an interference cancellation unit structural representation in the embodiment of the invention.

Embodiment

Among the embodiment provided by the invention, base station r is to received signal carried out Fourier transform and is obtained R, the compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾, according to the Carrier frequency offset estimation value that obtains and described compensation vector C ' ⁽ⁱ⁾Be met the signal that imposes a condition through frequency offset compensation through iterative process.

Be described in detail below in conjunction with the specific implementation of accompanying drawing embodiment provided by the invention.

The subcarrier of CU can be continuous, for example, whole subcarrier is divided into several subbands, and the subcarrier of each subband is continuous, and different user takies different subbands when inserting; The subcarrier of CU also can be discontinuous.f _cBe centre carrier frequency, Δ F is a subcarrier spacing, K CU 2M data subcarrier, and 2M data subcarrier is divided into Q is not had the subchannel that occurs simultaneously, and can be designated as M _q, wherein, q=0,1 ..., Q-1.Each subchannel is the least unit for user's allocation of subcarriers.The set that division obtains is satisfied $M=\underset{q=0}{\overset{Q-1}{\&cup;}}{M}_q,$ And when q ≠ q ', M _q∩ M _{Q '}Be empty set, promptly 2M data subcarrier all is divided in the subchannel, and the subcarrier that comprises in each subchannel must not have repetition.Optimal allocation can be carried out according to the residing environment of each user in the quantity of the subcarrier that each user is shared and position.As shown in Figure 1, can be arbitrarily user's allocation of subcarriers, the subcarrier of distributing to the user can not be continuous, under 3 users' the situation, as long as guaranteeing the subcarrier of each CU does not overlap, the subcarrier of a CU need not to have improved the flexibility of subcarrier allocation greatly continuously, and then obtains more frequency diversity gain.Fig. 2 is 5 subcarrier allocation signals that insert the user, and wherein, solid line is a data subcarrier, and different arrowhead forms represents that respective sub is taken by different user, and dotted line is represented the virtual subnet carrier wave, and this subcarrier does not transmit.

K CU p ^(k)Individual subcarrier, the subcarrier sequence number that takies $C^{\left(k\right)}=\{C_0^{\left(k\right)},C_1^{\left(k\right)},\&CenterDot;\&CenterDot;\&CenterDot;,C_{p^{\left(k\right)}-1}^{\left(k\right)}\}.$ Each user's signal is extended to the frequency-region signal that N is ordered, X after the subcarrier mapping ^(k)(n) be that k user sends and through Quaternary Phase Shift Keying (Quaternary Phase Shift Keying, QPSK) or quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM) Tiao Zhi frequency-region signal, wherein n ∈ { 1,2 ..., N}.X ^(k)(n) only on the shared subcarrier of k user value is arranged, other positions are 0, specifically can be referring to Fig. 2.K user's carrier frequency allocation table is $A^{\left(k\right)}=[A_0^{\left(k\right)},A_1^{\left(k\right)},\&CenterDot;\&CenterDot;\&CenterDot;,A_{N-1}^{\left(k\right)}],$ Wherein

Among the embodiment provided by the invention, A ^(k)In value be that 1 position can be continuous, also can be discontinuous.X ^(k)(n) (Inverse Fast Fourier Transform IFFT) becomes x after the conversion through the N point, inverse fast Fourier transform ^(k)(n).Wireless channel is a multidiameter fading channel, can adopt the time domain impulse response to describe, like this, and the channel time domain impulse response h between k user and the base station ^(k)=[h ^(k)(0), h ^(k)(1) ..., h ^(k)(L ^(k))] ^T, this is the statement to wireless channel, wherein L ^(k)Be impulse response length, corresponding to carrier frequency allocation table A ^(k), the channel time domain impulse response exists the position of value on the optional position of subcarrier, can be continuous, and also can be discontinuous.

After obtaining the Carrier frequency offset estimation value, can carry out the carrier frequency shift compensation according to this Carrier frequency offset estimation value.

If do not consider The noise, k user's signal is through behind the channel, and the signal that receive the base station can be expressed as:

$y^{\left(k\right)}=x^{\left(k\right)}\&CircleTimes;h^{\left(k\right)}---\left(1\right)$

Wherein, x ^(k)=[x ^(k)(0), x ^(k)(1) ..., x ^(k)(N-1)], h ^(k)=[h ^(k)(0), h ^(k)(1) ..., h ^(k)(L ^(k))] ^T,

The expression circular convolution, 1≤k≤K.

When user terminal increased Cyclic Prefix before transmitting, after Cyclic Prefix was removed in the base station, the relation between received signal and the subscriber signal still as shown in Equation (1).

Because the signal of n the sampled point that receive the base station is signal and noise sum that K user sends, is expressed as: $r\left(n\right)=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\left\{e^{{\mathrm{jn\&omega;}}^{\left(k\right)}}\underset{l=0}{\overset{L^{\left(k\right)}}{\mathrm{\&Sigma;}}}{h}^{\left(k\right)}\left(l\right)x^{\left(k\right)}(n-l)\right\}+z\left(n\right),$ Like this, the conversion form of expression can be expressed as: $r\left(n\right)=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{y}^{\left(k\right)}\left(n\right)e^{{\mathrm{jn\&omega;}}^{\left(k\right)}}+z\left(n\right),$ Wherein, r (n) is signal and the noise sum that K user sends, and obtains through behind the Fourier transform:

$R=\mathrm{DFT}\left(r\right)=\mathrm{DFT}(\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{y}^{\left(k\right)}{c}^{\left(k\right)}+z)=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{Y}^{\left(k\right)}\&CircleTimes;C^{\left(k\right)}+Z---\left(2\right)$

Wherein, r=[r (0), r (1) ..., r (N-1)] ^T, $y^{\left(k\right)}={[y_0^{\left(k\right)},y_1^{\left(k\right)},\&CenterDot;\&CenterDot;\&CenterDot;,y_{N-1}^{\left(k\right)}]}^T,$ $c^{\left(k\right)}=[1,e^{j{\mathrm{\&omega;}}^{\left(k\right)}},\&CenterDot;\&CenterDot;\&CenterDot;,e^{{j(N-1)\mathrm{\&omega;}}^{\left(k\right)}}]$ Be phase pushing figure, i.e. the pairing phase pushing figure that produces by carrier frequency shift of the different sampling point positions of k user's signal, z=[z (0), z (1) ..., z (N-1)] ^T, Y ^(k)=DFT (y ^(k)), C ^(k)=DFT (c ^(k)), Z=DFT (z).

Formula (2) can further be expressed as:

$R=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{Y}^{\left(k\right)}\&CircleTimes;C^{\left(k\right)}+Z=Y^{\left(k\right)}\&CircleTimes;C^{\left(k\right)}+\underset{i\&NotEqual;k}{\overset{K}{\underset{i=1}{\mathrm{\&Sigma;}}}}{Y}^{\left(i\right)}\&CircleTimes;C^{\left(i\right)}+Z---\left(3\right)$

Formula (3) comprises three parts, is respectively: k user's signal

Inter-user interference

With additive white Gaussian noise Z, like this, k user's signal can be expressed as: $Y^{\&prime;\left(k\right)}=Y^{\left(k\right)}\&CircleTimes;C^{\left(k\right)},$ Then variation can get:

$Y^{\left(k\right)}=Y^{\&prime;\left(k\right)}\&CircleTimes;C^{\&prime;\left(k\right)}---\left(4\right)$

Wherein, C ' ^(k)=DFT (c ' ^(k)), $c^{\&prime;\left(k\right)}=[1,e^{-j{\mathrm{\&omega;}}^{\left(k\right)}},\&CenterDot;\&CenterDot;\&CenterDot;,e^{-{j(N-1)\mathrm{\&omega;}}^{\left(k\right)}}],$ Be phase pushing figure c ^(k)Compensation rate, by to c ^(k)Carrying out conjugation obtains.

Utilize the carrier frequency allocation table to be $A^{\left(k\right)}=[A_0^{\left(k\right)},A_1^{\left(k\right)},\&CenterDot;\&CenterDot;\&CenterDot;,A_{N-1}^{\left(k\right)}]$ And R, k user's signal Y ' ^(k)Can be expressed as:

Y′ ^(k)＝A ^(k)R (5)

Formula (5), the equal substitution formula (4) of formula (3) can be got: $Y^{\left(k\right)}=\left(A^{\left(k\right)}R\right)\&CircleTimes;C^{\&prime;\left(k\right)}=(A^{\left(k\right)}(Y^{\left(k\right)}\&CircleTimes;C^{\left(k\right)}+\underset{i\&NotEqual;k}{\overset{K}{\underset{i=1}{\mathrm{\&Sigma;}}}}{Y}^{\left(i\right)}\&CircleTimes;C^{\left(i\right)}+Z))\&CircleTimes;C^{\&prime;\left(k\right)},$ Obtain at last:

$Y^{\left(k\right)}=\left(A^{\left(k\right)}(Y^{\left(k\right)}\&CircleTimes;C^{\left(k\right)})\right)\&CircleTimes;C^{\&prime;\left(k\right)}+(A^{\left(k\right)}\underset{i\&NotEqual;k}{\overset{K}{\underset{i=1}{\mathrm{\&Sigma;}}}}{Y}^{\left(i\right)}\&CircleTimes;C^{\left(i\right)})\&CircleTimes;C^{\&prime;\left(k\right)}+\left(A^{\left(k\right)}Z\right)\&CircleTimes;C^{\&prime;\left(k\right)}---\left(6\right)$

In the formula (6), Be k user's signal,

Be inter-user interference,

It is additive noise.By formula (6) as seen, this formula can not eliminate multi-user interference (Multi-User Interference, MUI).Among the embodiment provided by the invention, utilize Multiuser Detection and interference eliminated theory, repeatedly circulate with further elimination inter-user interference, Y ^{(k), j}K user's frequency-region signal when representing the j time iteration, specifically handling process is as shown in Figure 3:

During step 301:j=0, $Y^{\left(i\right),0}=\left(A^{\left(i\right)}R\right)\&CircleTimes;C^{\&prime;\left(i\right)},$ Because C ' ⁽ⁱ⁾With C ⁽ⁱ⁾Therefore conjugation, passes through A ⁽ⁱ⁾R and compensation vector C ' ⁽ⁱ⁾Convolution can eliminate C ⁽ⁱ⁾The influence of middle carrier frequency shift realizes the carrier frequency shift compensation, wherein, i=1,2 ..., K, thus the signal of each user among K the user who receives is carried out the carrier frequency shift compensation.

Merely carried out after the carrier frequency shift compensation, inter-user interference still exists, and therefore, can further eliminate inter-user interference, and concrete processing procedure is seen following description.

Step 302: make j=j+1, according to the Y that obtains ^{(i), j-1}Eliminate inter-user interference, promptly for k user, can get according to formula (3) $Y^{\&prime;\left(k\right),j}=R-\underset{i\&NotEqual;k}{\overset{K}{\underset{i=1}{\mathrm{\&Sigma;}}}}{Y}^{\left(i\right),j-1}\&CircleTimes;C^{\left(i\right)},$ Y ^{(i), j-1}Be k user's receiving in j-1 the iterative process the signal that carried out the carrier frequency migration, Y ' ^{(k), j}For this, k user's promptly receiving in the j time iterative process signal without the carrier frequency shift compensation.

Step 303: according to the Y ' that obtains ^{(k), j}Reappraise k user's received signal, can get according to the first of formula (6) $Y^{\left(k\right),j}=\left(A^{\left(k\right)}{Y}^{\&prime;\left(k\right),j}\right)\&CircleTimes;C^{\&prime;\left(k\right)}.$

Step 304: judge Y ^{(k), j}Whether restrain, if then continue execution in step 305; Otherwise, return execution in step 302, carry out iteration again.Judge Y ^{(k), j}Whether convergence can adopt the mode of expectation minimization to obtain, i.e. E{ ‖ Y ^{(k), j}-Y ^{(k), j-1}‖ ²}＜Δ, wherein, Δ is a convergence precision, is the value of expectation such as 1e-5,1e-6,1e-7 as Δ, if when satisfying condition, E{ ‖ Y ^{(k), j}-Y ^{(k), j-1}‖ ²When }＜Δ is set up, then think Y ^{(k), j}Convergence no longer continues iterative process; Otherwise, proceed iteration, promptly return execution in step 302, until the Y of the condition of being met ^{(k), j}

Step 305: the signal to k user is exported.

Above process is to carry out at each user among K the user.

Usually, just can access the Y of convergence through 4 to 5 times iterative process ^{(k), j}In above-mentioned iterative process, introduce circular convolution, it is generally acknowledged that the complexity of circular convolution is higher than Fourier transform processing, increased the complexity of iterative process on the surface.But in step 302 and step 303, Y ^{(k), j}And A ^(k)Y ' ^{(k), j}In have only p at most ^(k)Individual nonzero element, and as normalization carrier frequency shift ε ^(k)Hour, as | ε ^(k)|＜0.5, C ^(k)With C ' ^(k)In most of elements all very little, can replace with zero.If C ' ^(k)=C ' ^(k)(0), C ' ^(k)(1) ..., C ' ^(k)(N-1) }, then $C^{\&prime;\left(k\right)}\left(m\right)=\frac{\sin \left\{\mathrm{\&pi;}(m+{\mathrm{\&epsiv;}}^{\left(k\right)})\right\}}{\sin \left\{\frac{\mathrm{\&pi;}(m+{\mathrm{\&epsiv;}}^{\left(k\right)}}{N}\right\}}\&CenterDot;e^{\frac{-\mathrm{j\&pi;}(N-1)(m+{\mathrm{\&epsiv;}}^{\left(k\right)})}{N}}.$ This shows, sequence C ' ^(k)In, C ' ^(k)(N/2) near the value of element all approaches 0, therefore, W be sequence C ' ^(k)The quantity of middle nonzero element when W is odd number, can adopt sequence ${\tilde{C}}^{\&prime;\left(k\right)}=\{C^{\&prime;\left(k\right)}\left(0\right),C^{\&prime;\left(k\right)}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\&prime;\left(k\right)}\left(\frac{W-1}{2}\right),0,\&CenterDot;\&CenterDot;\&CenterDot;,0,C^{\&prime;\left(k\right)}(N-\frac{W-1}{2}),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\&prime;\left(k\right)}(N-1)\}$ Substitute C ' ^(k), adopt sequence ${\tilde{C}}^{\left(k\right)}=\{C^{\left(k\right)}\left(0\right),C^{\left(k\right)}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\left(k\right)}\left(\frac{W-1}{2}\right),0,\&CenterDot;\&CenterDot;\&CenterDot;,0,C^{\left(k\right)}(N-\frac{W-1}{2}),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\left(k\right)}(N-1)\}$ Substitute C ^(k)When W is even number, can adopt sequence ${\tilde{C}}^{\&prime;\left(k\right)}=\{C^{\&prime;\left(k\right)}\left(0\right),C^{\&prime;\left(k\right)}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\&prime;\left(k\right)}\left(\frac{W}{2}\right),0,\&CenterDot;\&CenterDot;\&CenterDot;,0,C^{\&prime;\left(k\right)}(N-\frac{W}{2}),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\&prime;\left(k\right)}(N-1)\}$ Substitute C ' ^(k), adopt sequence ${\tilde{C}}^{\left(k\right)}=\{C^{\left(k\right)}\left(0\right),C^{\left(k\right)}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\left(k\right)}\left(\frac{W}{2}\right),0,\&CenterDot;\&CenterDot;\&CenterDot;,0,C^{\left(k\right)}(N-\frac{W}{2}),\&CenterDot;\&CenterDot;\&CenterDot;,C^{\left(k\right)}(N-1)\}$ Substitute C ^(k)Like this, greatly reduce the complexity of circular convolution.C ^(k)(m) value of non-zero has only W in, therefore, only need be W time multiplication in the step 302, again since k user at p ^(k)Individual subcarrier transmitting data, this user's data not on other subcarriers, therefore, the multiplication number of circular convolution approximately is Wp ^(k), when W was very little, operand was less.

In addition, if user terminal had increased Cyclic Prefix in order to reduce intersymbol interference before transmitting, after then signal is received in the base station, before carrying out the carrier frequency shift compensation, can remove Cyclic Prefix earlier.

Fig. 4 is a base station receiver structural representation in the embodiment of the invention, as shown in Figure 4, base station receiver comprises that reception antenna, down-converter unit, modulus (AD) converter unit, serial to parallel conversion unit, Fourier transformation unit, CFO estimation unit, CFO compensating unit, parallel serial conversion unit and constellation point separate map unit.Wherein, reception antenna is used to receive the radiofrequency signal of user terminal emission, and provides this radiofrequency signal to down-converter unit; Down-converter unit is used for that the radiofrequency signal of receiving is carried out down-conversion and obtains baseband signal, and provides this baseband signal to the AD converter unit; The AD converter unit is used for the baseband signal of receiving is carried out the A/D conversion, obtains the discrete digital signal, and provides this discrete digital signal to the serial to parallel conversion unit; The serial to parallel conversion unit is used for serial data is transformed to parallel data, is the sampled point signal, and provides the sampled point signal respectively to Fourier transformation unit and CFO estimation unit; Fourier transformation unit is used for that the sampled point signal of receiving is carried out Fourier transform and obtains frequency-region signal, and provide this frequency-region signal to the CFO compensating unit, Fourier transform can pass through discrete Fourier transform (DFT) (Discrete Fourier Transform, DFT) computing or fast fourier transform (Fast Fourier Transform, FFT) computing realization; The CFO estimation unit is used for according to the received signal of receiving carrier frequency shift being estimated, provides the Carrier frequency offset estimation value to the CFO compensating unit then; The CFO compensating unit is used for according to the Carrier frequency offset estimation value of receiving the frequency-region signal of receiving being carried out the carrier frequency shift compensation, restores the signal of user terminal emission, provides this recovering signal to the parallel serial conversion unit then; And the string change unit be used for the signal of receiving is carried out parallel serial conversion, obtain serial data, separate map unit to constellation point then this serial data be provided; Constellation point is separated map unit and is used for that the serial data of receiving is carried out constellation point and separates mapping.Can further comprise cyclic prefix removal unit between AD converter unit and the serial to parallel conversion unit, be used for the discrete digital signal of receiving is removed Cyclic Prefix, and provide the discrete digital signal of removing Cyclic Prefix to the serial to parallel conversion unit.

Fig. 5 is a CFO compensating unit structural representation in the embodiment of the invention, and as shown in Figure 5, the CFO unit is used for to received signal r to carry out Fourier transform and obtain R, the compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾, according to compensation vector C ' ⁽ⁱ⁾After with the Carrier frequency offset estimation value of receiving the frequency-region signal of receiving being carried out carrier frequency shift compensation, also can be further used for carrying out the elimination of inter-user interference according to signal through frequency offset compensation, like this, the CFO compensating unit comprises compensating unit and interference cancellation unit, wherein, compensating unit is used for to received signal r to carry out Fourier transform and obtains R, the compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾, according to compensation vector C ' ⁽ⁱ⁾With the Carrier frequency offset estimation value of receiving each user's signal is carried out the carrier frequency shift compensation, and provide signal through the carrier frequency shift compensation to interference cancellation unit; The signal through the carrier frequency shift compensation that interference cancellation unit is used for receiving is met the signal that carried out the carrier frequency migration that imposes a condition through iterative process.The signal that compensating unit is received is r.

When interference cancellation unit adopts iterative process shown in Figure 3 to eliminate inter-user interference, as shown in Figure 6, interference cancellation unit comprises eliminates unit, estimation unit and decision unit, wherein, eliminate the unit and be used for eliminating inter-user interference, and provide the signal of eliminating inter-user interference to estimation unit according to the subscriber signal of receiving; Estimation unit is used for reappraising subscriber signal according to the signal of receiving, and provides this subscriber signal to decision unit; Decision unit is used to determine that the subscriber signal of receiving satisfies when imposing a condition, and subscriber signal is exported, and determines that the subscriber signal of receiving does not satisfy when imposing a condition, and provides this subscriber signal to eliminating the unit.Eliminate the subscriber signal of receiving for the first time the unit and come from compensating unit, the follow-up subscriber signal of receiving then comes from decision unit.

Therefore, the carrier frequency shift compensation scheme that provides in the embodiment of the invention not only can be realized the compensation of carrier frequency shift, can also eliminate inter-user interference.

The scheme that more than provides is applicable to any multicarrier system, as ofdm system, OFDMA system etc.

Among the embodiment provided by the invention, the carrier frequency shift compensation is not only carried out according to carrier frequency shift in the base station, also carry out the elimination of inter-user interference according to signal through frequency offset compensation, taken into full account inter-user interference, not only can realize the compensation of carrier frequency shift, can also eliminate inter-user interference, obtain subscriber signal estimated value more accurately.

In eliminating the inter-user interference process, introduce parameter W, reduced the complexity of circular convolution, remedied the shortcoming that adopts the circular convolution relative complex, be easy to the realization of hardware.The carrier frequency shift compensation scheme that the embodiment of the invention provides is not only applicable to the situation that user's low speed moves, and equally is applicable to the situation of user's high-speed mobile yet.

In addition, embodiment provided by the invention is applicable to the carrier frequency shift compensation under the norator carrier allocation scheme, to the sub-carrier distribution manner no requirement (NR) between the user, needn't be necessary for the user and distribute continuous subcarrier, all suitable to the regular allocation and the non-regular allocation of subcarrier.Because embodiment provided by the invention supports the random method of salary distribution of subcarrier, therefore, system can subcarrier be a transmission channel for the user distributes preferably according to channel situation, to obtain more frequency diversity gain, further reduce the error rate, increase transmission rate.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (10)

1. one kind is carried out the method that carrier frequency shift compensates, and it is characterized in that this method comprises:

Base station r is to received signal carried out Fourier transform and is obtained R;

The compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾

According to the Carrier frequency offset estimation value that obtains and described compensation vector C ' ⁽ⁱ⁾Be met the signal that imposes a condition through the carrier frequency shift compensation through iterative process.

2. method according to claim 1 is characterized in that, described according to described Carrier frequency offset estimation value and compensation vector C ' ⁽ⁱ⁾Be met the signal that imposes a condition through iterative process, comprise through the carrier frequency shift compensation:

When a2, j=0, $Y^{\left(i\right),0}=Y^{\left(i\right)}=\left(A^{\left(i\right)}R\right)\text{\&CircleTimes;}{C}^{\&prime;\left(i\right)},$ Wherein, j is an iterations, i=1, and 2 ..., K;

When b2, j=j+1, for k user, k the user's who receives in the j time iterative process signal without the carrier frequency shift compensation $Y^{\&prime;\left(k\right),j}=R-\underset{\underset{i\&NotEqual;k}{i=1}}{\overset{K}{\mathrm{\&Sigma;}}}{Y}^{\left(i\right),j-1}\&CircleTimes;C^{\left(i\right)},$ Wherein, Y ^{(i), j-1}It is k user's receiving in the j-1 time iterative process the signal that carried out the carrier frequency migration;

C2, according to described Y ' ^{(k), j}Reappraise k user's of reception signal $Y^{\left(k\right),j}=\left(A^{\left(k\right)}{Y}^{\&prime;\left(k\right),j}\right)\&CircleTimes;C^{\&prime;\left(k\right)};$

D2, determine Y ^{(k), j}Satisfy when imposing a condition, k user's signal is exported, determine Y ^{(k), j}Do not satisfy when imposing a condition, return execution in step b2.

3. method according to claim 2 is characterized in that, described Y ^{(k), j}That satisfies imposes a condition, and is: E{||Y ^{(k), j}-Y ^{(k), j-1}|| ²}＜Δ.

4. according to claim 2 or 3 arbitrary described methods, it is characterized in that described C ⁽ⁱ⁾Or C ' ^(k)In comprise W nonzero element.

5. according to the arbitrary described method of claim 1 to 3, it is characterized in that the described carrier frequency shift that carries out compensates, further comprise: the base station is estimated carrier frequency shift before.

6. according to the arbitrary described method of claim 1 to 3, it is characterized in that,

Described base station received signal further comprises before: user terminal added Cyclic Prefix before transmitting;

Described base station is estimated carrier frequency shift, further comprises before: Cyclic Prefix is removed in the base station.

7. according to the arbitrary described method of claim 1 to 3, it is characterized in that, for the user corresponding to described signal distributes the norator carrier wave.

8. one kind is carried out the device that carrier frequency shift compensates, and it is characterized in that this device comprises: compensating unit and interference cancellation unit, wherein,

Described compensating unit is used for to received signal r to carry out Fourier transform and obtains R, the compensation rate of the phase pushing figure among the described r is carried out Fourier transform be compensated vectorial C ' ⁽ⁱ⁾, according to described compensation vector C ' ⁽ⁱ⁾With the Carrier frequency offset estimation value that obtains each user's signal is carried out the carrier frequency shift compensation, and provide signal through the carrier frequency shift compensation to described interference cancellation unit;

The signal through the carrier frequency shift compensation that described interference cancellation unit is used for receiving is met the signal that carried out the carrier frequency migration that imposes a condition through iterative process.

9. device according to claim 8 is characterized in that, described interference cancellation unit comprises: eliminate unit, estimation unit and decision unit, wherein,

Described elimination unit is used for eliminating inter-user interference according to the signal of receiving, and provides the signal of eliminating inter-user interference to estimation unit;

Described estimation unit is used for reappraising according to the signal of receiving the signal of user terminal, and provides this signal to decision unit;

Described decision unit is used to determine that the signal of receiving satisfies when imposing a condition, and the signal of user terminal is exported, and determines that the subscriber signal of receiving does not satisfy when imposing a condition, and provides this signal to eliminating the unit.

10. according to Claim 8 or 9 described devices, it is characterized in that this device further comprises the Carrier frequency offset estimation unit, be used for carrier frequency shift is estimated, and provide the Carrier frequency offset estimation value to described compensating unit.

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