WO2017036193A1 - 一种频偏估计方法及装置 - Google Patents

一种频偏估计方法及装置 Download PDF

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WO2017036193A1
WO2017036193A1 PCT/CN2016/083351 CN2016083351W WO2017036193A1 WO 2017036193 A1 WO2017036193 A1 WO 2017036193A1 CN 2016083351 W CN2016083351 W CN 2016083351W WO 2017036193 A1 WO2017036193 A1 WO 2017036193A1
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target user
estimation value
channel estimation
data
frequency domain
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PCT/CN2016/083351
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English (en)
French (fr)
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魏继东
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中兴通讯股份有限公司
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Priority to US15/756,587 priority Critical patent/US10148463B2/en
Publication of WO2017036193A1 publication Critical patent/WO2017036193A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H04L25/0218—Channel estimation of impulse response with detection of nulls
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/022—Channel estimation of frequency response
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2669—Details of algorithms characterised by the domain of operation
    • H04L27/2672—Frequency domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2675—Pilot or known symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2691—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/0035—Synchronisation arrangements detecting errors in frequency or phase
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/7103—Interference-related aspects the interference being multiple access interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
    • H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
    • H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
    • H04B2201/70728—Frequency aspects

Definitions

  • the present application relates to, but is not limited to, the field of communications, and in particular, to a frequency offset estimation method and apparatus.
  • a new generation of mobile communication systems requires high-speed, high-spectrum efficiency, and large-capacity multimedia data transmission capabilities.
  • High-speed data transmission in the wireless environment will cause severe frequency selective fading, and Orthogonal Frequency Division Multiplexing (OFDM) technology stands out because of its outstanding advantages.
  • OFDM Orthogonal Frequency Division Multiplexing
  • OFDM is a multi-carrier transmission technology in which subcarriers are orthogonal to each other. It divides a wide transmission bandwidth into multiple subcarriers that are orthogonal to each other for data transmission in parallel. It has the advantages of high spectrum utilization, anti-multipath fading, and simple multiple-input multiple-output (MIMO) technology. However, since OFDM technology requires the mutual orthogonality between subcarriers, it is very sensitive to frequency offset.
  • ISI Inter-Symbol Interference
  • the synchronization problem is one of the core problems of OFDM technology.
  • many communication engineers have proposed a variety of synchronous solutions. If the frequency offset estimation method of the continuous pilot symbols is used to perform frequency offset estimation on the grooming pilot symbols, the estimation accuracy loss is relatively large.
  • the non-continuously distributed pilot symbols such as the dressing distribution to perform frequency offset estimation and to ensure no loss with respect to the continuously distributed pilot symbols.
  • the purpose of the present application is to provide a frequency offset estimation method and apparatus, which can better solve the problem of frequency offset estimation using non-continuously distributed pilot symbols such as a dressing distribution.
  • a frequency offset estimation method includes:
  • the channel estimation value of the target user and the channel estimation value of the non-target user are reconstructed to obtain a reconstructed channel estimation value of the target user and a reconstructed channel estimation value of the non-target user.
  • the frequency domain data of the subcarrier occupied by the target user, the frequency domain data of the subcarriers occupied by the adjacent non-target users, the reconstructed channel estimation value of the target user, and the reconstructed channel estimation value of the non-target user are used to calculate the interference cancellation.
  • the target user's local pilot receives data in the frequency domain.
  • the frequency offset estimation value is determined by using the local pilot and frequency domain receiving data of the interference canceling target user.
  • the channel estimation value of the target user and the channel estimation value of the non-target user are reconstructed, and the reconstructed channel estimation value of the target user and the reconstructed channel estimation value of the non-target user are obtained:
  • a channel estimation value of a resource occupied by an adjacent non-target user determines a reconstructed channel estimation value of the target user.
  • the calculating the frequency domain receiving data of the local pilot of the target user that has cancelled the interference includes:
  • the target user's frequency domain data is conjugate-correlated with the target user's reconstructed channel estimation value to obtain The frequency domain receiving data of the local pilot of the target user that cancels the interference is cancelled.
  • the calculating the frequency domain receiving data of the local pilot of the target user that has cancelled the interference further includes:
  • the combo user's reconstructed channel estimation value is used to eliminate the combing user from being adjacent to the target user.
  • the interference data on the subcarriers obtains the frequency domain receiving data of the local pilot of the target user who has cancelled the interference; or
  • the minimum mean square error algorithm or the zero forcing algorithm is used to select the frequency domain data of the subcarriers occupied by the target user and the adjacent
  • the frequency domain data of the subcarrier occupied by the non-target user, the reconstructed channel estimation value of the target user, and the reconstructed channel estimation value of the non-target user are processed, and the frequency domain receiving data of the subcarrier occupied by the target user is obtained, and the target user is The frequency domain receiving data leaked on the subcarriers occupied by the adjacent non-target users.
  • the calculating the frequency domain receiving data of the local pilot of the target user that has cancelled the interference further includes:
  • the channel of the target user is orthogonal to the channel of the non-target user, and the interference of the non-target user's frequency domain data to the adjacent subcarrier of the target user during the transmission is eliminated.
  • the determining, by using the local pilot and the frequency domain receiving data of the interference canceling target user, determining the frequency offset estimation value includes:
  • the frequency offset measurement is performed by using the obtained time-domain received data of the local pilot and the time domain data sequence to obtain a frequency offset estimation value.
  • the determining, by using the local pilot and the frequency domain receiving data of the interference canceling target user, determining the frequency offset estimation value further includes:
  • the performing the frequency offset measurement by using the time domain receiving data and the time domain data sequence of the obtained local pilot, and obtaining the frequency offset estimation value further includes:
  • a frequency offset estimating apparatus includes:
  • the reconstruction module is configured to reconstruct the channel estimation value of the target user and the channel estimation value of the non-target user, to obtain a reconstructed channel estimation value of the target user and a reconstructed channel estimation value of the non-target user.
  • the interference cancellation module is configured to use frequency domain data of the subcarrier occupied by the target user, frequency domain data of the subcarriers occupied by the adjacent non-target users, reconstructed channel estimation values of the target user, and reconstructed channel estimation of the non-target user. Value, the frequency domain received data of the local pilot of the target user who has cancelled the interference.
  • the frequency offset estimation module is configured to determine the frequency offset estimation value by using the local pilot and the frequency domain receiving data of the target user that has cancelled the interference.
  • the reconstruction module includes:
  • a first reconstruction sub-module configured to calculate a channel estimation value of a resource occupied by an adjacent non-target user by using a channel estimation value of the target user in a resource block occupied by the target user, and using the A channel estimation value of the target user and a channel estimation value of the resource occupied by the adjacent non-target user determine a reconstructed channel estimation value of the target user.
  • a second reconstruction sub-module configured to calculate, by using a channel estimation value of the non-target user, a channel of resources occupied by other users adjacent to the non-target user in a resource block occupied by the non-target user Estimating a value, and determining a reconstructed channel estimation value of the non-target user by using a channel estimation value of the non-target user and a channel estimation value of the resource occupied by the other user.
  • the interference cancellation module calculates frequency domain receiving data of the local pilot of the target user that has cancelled the interference, including: when the channel of the target user is orthogonal or weakly related to the channel of the non-target user And performing conjugate correlation calculation on the frequency domain data of the target user and the reconstructed channel estimation value of the target user, to obtain frequency domain receiving data of the local pilot of the target user that has cancelled interference.
  • the interference cancellation module calculates the frequency domain receiving data of the local pilot of the target user that has cancelled the interference, and further includes: when the target user and the non-target user are combing users and the channel between the two is strong Correlation, using the reconstructed channel estimation value of the combing user, eliminating the interference data of the combing user on the adjacent subcarrier of the target user, and obtaining the frequency domain receiving of the local pilot of the target user who has cancelled the interference Data, or, when the target user and the non-target user are code division users and have strong correlation between the two channels, using a minimum mean square error algorithm or a zero-forcing algorithm, the frequency domain of the subcarrier occupied by the target user Data and frequency domain data of subcarriers occupied by adjacent non-target users, reconstructed channel estimation values of target users, and reconstructed channel estimation values of non-target users
  • the line processing obtains the frequency domain receiving data of the subcarrier occupied by the target user and the frequency domain receiving data leaked by the target user on the subcarrier occupied by the adjacent
  • the interference cancellation module calculates the frequency domain receiving data of the local pilot of the target user that has cancelled the interference, further comprising: using the reconstructed channel estimation value of the target user and the reconstructed channel estimation of the non-target user a value, calculating an orthogonalization factor, and orthogonalizing the channel of the non-target user by using the orthogonalization factor to orthogonalize a channel of the target user with a channel of the non-target user And canceling interference of the non-target user's frequency domain data to adjacent subcarriers of the target user during transmission.
  • the frequency offset estimation module uses the local pilot and the frequency domain receiving data of the interference canceling target user, and determining the frequency offset estimation value includes: reconstructing the local pilot of the target user, and obtaining a weight Constructing a local pilot sequence, and performing frequency-time transform on the local pilot and frequency domain received data of the target user with the interference cancellation and the reconstructed local pilot sequence respectively, to obtain time domain receiving data of the local pilot and
  • the time domain data sequence uses the time domain received data of the obtained local pilot and the time domain data sequence to perform frequency offset measurement to obtain a frequency offset estimation value.
  • the frequency offset estimation module uses the local pilot and the frequency domain receiving data of the interference canceling target user, and determining the frequency offset estimation value further includes: reconstructing a local mother code sequence of the target user, A reconstructed local mother code sequence is obtained, and the reconstructed local mother code sequence is subjected to frequency-time transform and cyclic shift operation to obtain a time-domain data sequence of the local pilot.
  • the frequency offset estimation module uses the local pilot and the frequency domain receiving data of the interference canceling target user, and determining the frequency offset estimation value further includes: receiving the time domain receiving data and the time domain of the local pilot The data sequence performs a conjugate correlation operation to obtain a phase sequence of the time domain, and uses the phase sequence of the time domain to determine the frequency offset estimation value.
  • a computer readable storage medium storing computer executable instructions that, when executed by a processor, implement the frequency offset estimation method.
  • the frequency offset measurement is performed by using non-continuously distributed pilot symbols such as a vane distribution, and the frequency domain data leaked from adjacent subcarriers is effectively used in the measurement process to perform frequency offset measurement, which ensures the guide well.
  • the frequency offset estimation performance in the case of discontinuous distribution of frequency symbols; and the frequency offset measurement accuracy of the target user is improved by eliminating or reducing interference between users.
  • FIG. 1 is a schematic block diagram of a frequency offset estimation method according to an embodiment of the present invention.
  • FIG. 2 is a block diagram of a frequency offset estimation apparatus according to an embodiment of the present invention.
  • FIG. 3 is a flowchart of frequency offset estimation processing of a frequency division user according to an embodiment of the present invention
  • FIG. 4 is a flowchart of a frequency offset estimation process for strong correlation between users according to an embodiment of the present invention
  • FIG. 5 is a first resource map of a combing user according to an embodiment of the present invention.
  • FIG. 6 is a second resource map of a frequency division user according to an embodiment of the present invention.
  • FIG. 1 is a schematic block diagram of a frequency offset estimation method according to an embodiment of the present invention.
  • the embodiment of the present invention mainly uses a single symbol pilot for frequency offset estimation in a non-continuous distribution such as a dressing distribution, and the method is not only applicable to the downlink frequency offset. Measurements are also applicable to upstream frequency offset measurements.
  • the embodiment of the present invention not only utilizes the frequency offset information on the target subcarrier, but also utilizes the frequency offset information leaked on the adjacent subcarriers to perform frequency offset estimation, which can greatly improve the dressing distribution or The accuracy of the frequency offset estimation of a single symbol in the case of discontinuous distribution.
  • the content of this embodiment includes steps S101-S105:
  • Step S101 extraction of pilot frequency domain data (hereinafter referred to as frequency domain data) of the target user.
  • the extracted frequency domain data of the target user is represented by Y.
  • the frequency domain data of the non-target users on the adjacent subcarriers needs to be extracted at the same time.
  • Step S102 Reconstruction of channel estimation values.
  • the reconstructed channel estimate is represented by H.
  • the non-continuously distributed pilot symbols such as the dressing distribution
  • LS Least Square
  • ZF Zero Forcing
  • the channel estimation value of the target subcarrier of the target user may be used to obtain the channel estimation value on the adjacent non-target user resource, for example,
  • the channel estimation value of the target non-target user resource is determined as the channel estimation value of the target user's target sub-carrier by the flat push; or the target user's two-two sub-carrier interpolation may be used to acquire the non-target user resource.
  • the channel estimation value for example, by interpolation, determines the channel estimation value on the adjacent non-target user resource as an arbitrary value between the two channel estimation values corresponding to the two subcarriers occupied by the target user.
  • the method for obtaining the channel estimation value on the non-target user resource data is not limited in the embodiment of the present invention.
  • the two-two subcarrier spacing is one subcarrier as shown in FIG. 5, for example, a sounding reference signal (Sounding Reference Signal) , SRS) resource distribution mode
  • the channel estimation value on the adjacent non-target user resources can be obtained by the push-pull method; when the interval is 2 sub-carriers as shown in FIG. 6, the corresponding channel estimation can pass the target user Data on adjacent subcarriers is pushed flat
  • the channel estimation values on the non-target user data bits can be obtained by interpolation through the data on the two subcarriers of the target user.
  • the code division user needs to at least ensure the guidance between the users.
  • the frequency is orthogonal so that accurate channel estimates are obtained.
  • Step S103 Perform the correlation operation between the two pairs by using the frequency domain data and the channel estimation value of the target user acquired in step S101 and step S102, and calculate the received local pilot data (that is, the frequency domain receiving data of the local pilot). .
  • the local guide of the target user is obtained.
  • the frequency domain frequency receiving data is calculated in a relatively simple manner, that is, the frequency domain data acquired in step S101 is directly used for correlation calculation with the channel estimation value reconstructed in step S102; if the target user occupies resources, there are other users such as code division users.
  • the orthogonality of the pilot codes between the code division users it is also necessary to ensure that the channels between the code division users are weakly correlated; if there are other comb users on the resource blocks occupied by the target users, the same is required.
  • this step is mainly processed in the following four cases:
  • the following processing is relatively simple, and it is not necessary to consider interference cancellation between users.
  • the frequency domain data Y of the target user includes data of L subcarriers of adjacent non-target users on each subcarrier,
  • the data includes the Internal Carrier Interference (ICI) energy and the noise interference energy leaked on the subcarrier occupied by the user, that is, because the pilot pilot symbols are discontinuously distributed in the frequency domain, and the interval is different.
  • the resource occupied by the target user where the resource occupied by the non-target user is L.
  • the conjugate correlation calculation is performed by using the channel estimation value H reconstructed as above and the extracted frequency domain data Y, thereby calculating the frequency domain reception data of the local pilot, that is,
  • the target user occupies only the combing user on the resource block, but there is no scheduling code to divide the user.
  • the processing is relatively simple, and the FB is directly correlated with the extracted frequency domain data of the target user and the channel estimation value of the reconstructed target user, because The channels of the two users are orthogonal or weakly correlated, which can weaken or eliminate the interference of the combing user to the target user; if the channel of the combing user cannot guarantee orthogonal or weak correlation, the pilot code of the two users is utilized. Orthogonality is used for interference cancellation.
  • the calculation method of the channel estimation can be performed by the time domain method or the frequency domain method, and will not be described in detail herein.
  • the calculated channel estimation for combing eliminates the user's interference to the target user, that is, performs interference cancellation on the data of the adjacent subcarriers of the target user.
  • frequency domain data after interference cancellation is obtained. That is, the leakage energy of the target user on the subcarrier.
  • the difference between the method for calculating the frequency offset of the conventional combing according to the embodiment of the present invention is that the frequency offset estimation is performed by using the data leaked on the non-target user subcarriers at the time of estimation, that is, the frequency of the adjacent non-target users.
  • the domain data participates in the frequency offset estimation process of the target user.
  • the frequency domain data after the interference cancellation and the channel estimation value are used for conjugate correlation operation, thereby acquiring the frequency domain receiving data of the local pilot.
  • MMSE Minimum Mean Square Error
  • ZF interference cancellation
  • the frequency domain data can effectively eliminate the interference of the user to the target user by the method, but the implementation complexity is relatively large, and the preferred solution is not implemented in this configuration.
  • the channel of the two users can be orthogonalized by using the Gram-Schmidt orthogonalization idea, and the channel of the originating user is positive. Intersection processing.
  • This idea is mainly used in the Time Division Duplex (TDD) system. It mainly considers that the uplink and downlink channels are symmetric in the TDD mode. The channel information obtained by the uplink is used to calculate the orthogonalized vector of the two user channels, that is, orthogonal.
  • TDD Time Division Duplex
  • the orthogonalization factor w is used to orthogonalize the channel of the combing user, that is, the channel of the user is orthogonalized and preprocessed by using the factor, that is, the left end is multiplied by the source in the frequency domain data. Interacting factor w.
  • the processing in this case if the channel between the code division users is orthogonal or weakly correlated, the processing in this case is relatively simple, and the frequency domain data of the target user of step S101 is directly used and the target of step S102 is directly used.
  • the channel estimation value of the user performs a conjugate correlation operation. Since the channels are orthogonal or weakly correlated, this operation can weaken or eliminate the interference of the code division user to the target user; if the channel between the code division users does not satisfy the orthogonality Or weakly correlated characteristics, in which case the above method will have an impact on the final estimated performance. In this case, the two methods can be used to solve the problem.
  • the influence of interference between users is ignored, and the frequency domain data of the previous step S101 and the channel estimation value of step S102 are directly used for frequency offset estimation. It is relatively simple. The disadvantage is that there is interference from the code-divided user to the target user, which affects the final measurement accuracy. Secondly, it is necessary to consider the interference elimination between the code-divided users.
  • the elimination method can use MMSE or ZF, etc., using the above-mentioned step S101.
  • the extracted frequency domain data and the channel estimation result of step S102 perform interference cancellation to acquire corresponding data.
  • the interference cancellation method can be used to calculate the frequency domain data on the corresponding subcarriers on the resources occupied by the target user and the data energy leaked by the target users on the adjacent non-target user subcarriers, which are respectively calculated by using ZF as an example.
  • the amount of energy leaked is related to the subcarrier spacing and the sampling offset. In the usual case, only the adjacent M subcarriers are considered for interference cancellation.
  • the solution of the present invention is to solve the problem that the channel between the two users is orthogonalized. For the processing method, refer to the second case, and details are not described herein.
  • the interference between users can also be weakened from the perspective of scheduling, thereby reducing the processing complexity of the lower layer, that is, the frequency offset of the two users who need to ensure the code division is in the same direction or two users during scheduling.
  • the difference in frequency offset is small.
  • the phase offset is transferred to the channel estimation value to calculate the reception frequency domain data of the local pilot of the target user, that is, This calculation method does not need to pay attention to the channel orthogonality between two users, as long as the difference between the frequency offset values of the two users of the code division is small, where ⁇ is the cyclic shift factor of the code division user relative to the target user. .
  • the processing in this case is relatively simple, and directly uses the frequency domain data of the target user in the previous step S101 (including the frequency domain data on the adjacent resources) to perform a conjugate correlation operation with the channel estimation value of the target user in step S102. Since the channels of the two users are orthogonal or weakly correlated, the code division or the interference of the user can be eliminated under the above operation; if the channel between the target user and the comb or code division user is orthogonal or weak Corresponding, and is strongly related to the channel of another user.
  • the processing method in this case refers to the processing of the second case or the third case; if the channel between the target user and the combing and code division users All of them are strongly related. For this situation, three ideas can be used to solve the problem.
  • the resources occupied by the target are directly utilized.
  • the frequency domain data and the corresponding channel estimation value are subjected to a conjugate correlation operation. It should be noted that the frequency domain data used is different from the method for extracting the frequency domain data described above, and only the frequency domain data on the resources occupied by the target user is extracted, and the data energy of the leakage is not considered, and the method measures The accuracy is low, and it will be interfered by the code division and the combing user.
  • the estimation accuracy will be affected by the interference between users.
  • the calculated combing user's channel estimation value and local pilot data are used to comb the user on the adjacent subcarrier of the target user. Data is eliminated to obtain the adjacent subcarriers of the target user and the code division user Combine the user's data leakage energy.
  • the processing manner of the third case can be referred to, and details are not described herein again.
  • the Gram-Schimdt orthogonalization method can be used first, so that the code division user and the comb user are orthogonal to the target user's channel, and then the conventional idea is utilized.
  • the frequency domain receiving data of the local pilot of the target user is obtained.
  • Step S104 Reconstruct the local pilot sequence of the target user.
  • the process is relatively simple.
  • the length of the reconstructed local pilot sequence or the local mother code sequence is the same as the length of the previously reconstructed frequency domain data, and the corresponding guide on the subcarrier occupied by the non-target user.
  • the frequency sequence or mother code sequence is zero.
  • Step S105 Perform frequency-frequency transform on the frequency domain received data of the previously calculated local pilot and the reconstructed local pilot sequence/local mother code sequence.
  • an Inverse Discrete Fourier Transform (IDFT) transform may be used, or an Inverse Fast Fourier Transform (IFFT) transform, or other time-frequency transform, may be used. No restrictions.
  • step S104 when the time domain is transformed, the time domain sequence corresponding to the pilot of the user is restored according to the cyclic shift corresponding to the user.
  • Step S106 Perform frequency offset measurement by using the time domain sequence corresponding to the local pilot sequence/local mother code sequence calculated in the foregoing and the time domain sequence corresponding to the frequency domain receiving data.
  • This step mainly uses the characteristics that the frequency offset will produce a linear phase in the time domain.
  • the phase difference between two points or the phase difference between the first half and the second half can be used. Or divide the phase sequence into small segments and then calculate the phase difference between the two segments. Finally, based on the phase difference described above, the final frequency offset estimate is obtained. Since this process does not belong to the main idea of the present invention, it will not be described in detail herein.
  • Step 1 Extraction of the frequency domain data of the target user.
  • the received data is time domain data
  • the pilot frequency domain needs to be first transformed.
  • the time-frequency variation is a common processing of Long Term Evolution (LTE), and will not be described in detail herein.
  • LTE Long Term Evolution
  • Step 2 Reconstruction of the channel estimate of the target user.
  • the channel estimation value of the target user needs to be calculated first, and the calculation method may be a time domain method or a frequency domain method, and the method is not limited by the method. If the channel estimation value of the target user is obtained, it is necessary to perform channel estimation reconstruction using the estimated channel estimation value.
  • the main idea of the reconfiguration is to estimate the channel estimation value of the resource occupied by the non-target user in the resource block occupied by the target user by using the channel estimation corresponding to the adjacent target user subcarrier, considering the channel frequency selection.
  • the transformation is not very fast. It is recommended to use the flat push method, but it is not limited to this method, and can be obtained by linear interpolation or nonlinear interpolation.
  • the estimated value is expressed as If the pilot symbol of the target user is a grooming distribution, the channel estimation value at the corresponding frequency domain resource location is the channel estimation value H k on the target subcarrier of the target user, which is adjacent to each subcarrier and is not assigned to The channel estimation value on the resource of the target user is the channel estimation value on the non-target user resource data, and for the reconstructed channel estimation value. Composed of the first two, namely Contains H k .
  • Step 3 Calculate the frequency domain receiving data of the local pilot.
  • the calculation of the process is to directly use the previously extracted frequency domain data and the reconstructed channel estimation value of the target user to perform conjugate multiplication, thereby eliminating the channel influence of the received data, that is, the calculated local pilot.
  • Frequency domain receiving data expressed as
  • the resource block occupied by the target user includes not only the resources of the target user but also the idle resources and even the resources of other users, so the reconstructed of the target user.
  • the number of channel estimation values is greater than the number of subcarriers actually occupied by the target user.
  • Step 4 Reconstruct the local pilot sequence of the target user.
  • the two methods can be used for processing.
  • the pilot sequence of the target user is directly reconstructed, and second, the mother code sequence corresponding to the target user is reconstructed.
  • the process is relatively simple, and the length of the reconstructed local pilot sequence or the mother code sequence is the same as the length of the previously reconstructed frequency domain data, wherein the pilot corresponding to the subcarrier occupied by the non-target user The sequence value or the mother code sequence value is 0.
  • the local pilot sequence of the target user is reconstructed as an example.
  • Step 5 Perform frequency-frequency transformation on the frequency domain received data of the locally calculated pilot and the reconstructed local pilot sequence.
  • an IDFT transform may be used, or an IFFT transform, or a frequency-time transform of other methods may be used.
  • the frequency-time transform is performed by using an IFFT method. Since the length of the previously reconstructed data is 288, but the length of the IFFT transform is 2 n , it is preferred to perform zero insertion processing on the tail of the previous local pilot sequence and the calculated local pilot frequency domain received data.
  • the length is 2 n , that is, 224 zeros are first inserted into the two frequency domain data, and then the interpolated frequency domain data is subjected to IFFT transformation, thereby acquiring the time domain sequence Tx n corresponding to the local pilot sequence (ie, local pilot)
  • Step 6 Perform frequency offset measurement by using the time domain data sequence Tx n and the time domain receiving data Rx n of the local pilot obtained in the foregoing calculation.
  • This step is mainly to calculate the frequency phase in the time domain to produce a linear phase.
  • the phase difference between the two points or the phase difference between the first half and the second half or the phase sequence can be divided into several. Small segment, then calculate the phase difference between the two segments.
  • the final frequency offset estimate is obtained based on the phase difference described above. The process is as follows, including sub-step 1 to sub-step 2:
  • Sub-step 2 frequency offset estimation is performed by using the phase generated by the frequency offset in a linear relationship in the time domain, and the frequency offset estimation may be performed by using two adjacent samples at the time of estimation, or may be equally or not spaced.
  • the frequency offset estimation is performed, and the method used in the present invention is not limited.
  • the phase sequence can be intercepted, that is, the phase sequence of the part can be used for frequency offset estimation, which is not limited herein.
  • the following description uses all phase sequences for frequency offset estimation. For example, the phase difference between the first half and the second half is used to perform frequency offset estimation.
  • ⁇ f is the size of the subcarrier spacing
  • the frequency offset value between the target user and the code division user is the same in the scheduling manner, and the difference of the cyclic shift of the pilot sequence between the two users is assumed to be ⁇ .
  • the implementation process is as follows, including step 1 to Step 6:
  • Step 1 Extraction of the frequency domain data of the target user.
  • the received data is time domain data
  • the pilot frequency domain needs to be first transformed.
  • the time-frequency variation is a common processing of LTE, and will not be described in detail herein.
  • the process of extracting the frequency domain data of the target user not only the data of the subcarriers occupied by the target user but also the subcarrier data occupied by the non-target users are extracted.
  • Step 2 Reconstruction of the channel estimate of the target user.
  • the channel estimation value of the target user needs to be calculated first, and the calculation method may be a time domain method or a frequency domain method, and the method is not limited by the method. If the channel estimation value of the target user is obtained, it is necessary to perform channel estimation reconstruction using the estimated channel estimation value.
  • the main idea of the reconfiguration is to estimate the channel estimation value of the resource occupied by the non-target user in the resource block occupied by the target user by using the channel estimation corresponding to the adjacent target user subcarrier, considering the channel frequency selection.
  • the transformation is not very fast. It is recommended to use the flat push method, but it is not limited to this method and can be obtained by linear interpolation or nonlinear interpolation.
  • the method is the same as the target user, and the time domain method or the frequency domain method may be adopted, and which method is used without limitation, and the channel estimation value of the code division user is assumed.
  • Step 3 Calculation of frequency domain data received by the local pilot (ie, frequency domain received data of the local pilot).
  • Step 4 Reconstruct the local pilot sequence of the target user.
  • the two methods can be used for processing.
  • the pilot sequence of the target user is directly reconstructed, and second, the mother code sequence corresponding to the target user is reconstructed.
  • the process is relatively simple, and the length of the reconstructed local pilot sequence or the mother code sequence is the same as the length of the previously reconstructed frequency domain data, wherein the pilot corresponding to the subcarrier occupied by the non-target user The sequence value or the mother code sequence value is 0.
  • the local pilot sequence of the target user is reconstructed as an example.
  • Step 5 Frequency domain received data and reconstructed local pilot of the previously calculated local pilot The sequence is frequency-time transformed.
  • an IDFT transform may be used, or an IFFT transform, or a frequency-time transform of other methods may be used.
  • the frequency-time transform is performed by using an IFFT method. Since the previously reconstructed data length is 288, but the length of the IFFT transform is 2 n , the frequency domain of the local pilot frequency domain (ie, the local pilot sequence) and the calculated local pilot are preferably used.
  • the tail of the received data is subjected to zero insertion processing, and the length is 2 n , that is, 224 zeros are first inserted into the two frequency domain data, and then the frequency domain data after the zero insertion is subjected to IFFT transformation, thereby acquiring the time domain of the local pilot.
  • Step 6 Perform frequency offset measurement by using the previously calculated local pilot time domain data sequence Tx n and time domain received data Rx n .
  • This step is mainly to calculate the frequency phase in the time domain to produce a linear phase.
  • the phase difference between the two points or the phase difference between the first half and the second half or the phase sequence can be divided into several. Small segment, then calculate the phase difference between the two segments.
  • the final frequency offset estimate is obtained based on the phase difference described above. The process is as follows, including sub-step 1 to sub-step 2:
  • Sub-step 1 using the previously calculated local pilot time domain data sequence Tx n and the local pilot time domain receiving data Rx n to perform a conjugate correlation operation, thereby obtaining a phase sequence WR due to the frequency offset, ie
  • Sub-step 2 frequency offset estimation is performed by using the phase generated by the frequency offset in a linear relationship in the time domain, and the frequency offset estimation may be performed by using two adjacent samples at the time of estimation, or may be equally or non-interval.
  • the frequency offset estimation is performed, and the method used in the present invention is not limited.
  • the phase sequence can be intercepted, that is, the phase offset of the phase sequence can be used to perform the frequency offset estimation, which is not limited herein.
  • the following description uses all phase sequences for frequency offset estimation, for example, using the phase difference between the first half and the second half for frequency offset estimation, ie Where ⁇ f is the size of the subcarrier spacing;
  • FIG. 2 is a block diagram of a frequency offset estimation apparatus according to an embodiment of the present invention. As shown in FIG. 2, the method includes: a reconstruction module 10, an interference cancellation module 20, and a frequency offset estimation module 30.
  • the reconstruction module 10 is configured to reconstruct the channel estimation value of the target user and the channel estimation value of the non-target user to obtain a reconstructed channel estimation value of the target user and a reconstructed channel estimation value of the non-target user.
  • the reconstruction module 10 includes a first reconstruction submodule and a second reconstruction submodule, where the first reconstruction submodule is configured to utilize a channel of the target user in a resource block occupied by the target user.
  • the second reconstruction sub-module is configured to calculate, in the resource block occupied by the non-target user, the channel estimation value of the non-target user, to calculate another neighboring party adjacent to the non-target user The channel estimation value of the resource occupied by the user, and determining the reconstructed channel estimation value of the non-target user by using the channel estimation value of the non-target user and the channel estimation value of the resource occupied by the other user.
  • the interference cancellation module 20 is configured to utilize frequency domain data of the subcarrier occupied by the target user, frequency domain data of the subcarriers occupied by the adjacent non-target users, reconstructed channel estimation values of the target user, and reconstructed channel estimation of the non-target user. Value, the frequency domain received data of the local pilot of the target user who has cancelled the interference.
  • Interference cancellation can be done in the following ways:
  • the interference cancellation module 20 performs the frequency domain data of the target user and the reconstructed channel estimation value of the target user.
  • the conjugate correlation operation obtains the frequency domain reception data of the local pilot of the target user who has cancelled the interference.
  • the interference cancellation module 20 uses the reconstructed channel estimation value of the combing user to eliminate the combing user.
  • the interference data on the adjacent subcarriers of the target user obtains the frequency domain reception data of the local pilot of the target user who has cancelled the interference.
  • the interference cancellation module 20 uses the least mean square error algorithm or the zero forcing algorithm to the subcarriers occupied by the target user.
  • the frequency domain data and the frequency domain data of the subcarriers occupied by the adjacent non-target users, the reconstructed channel estimation value of the target user, and the reconstructed channel estimation value of the non-target user are processed to obtain the frequency domain of the subcarrier occupied by the target user.
  • the received data and the frequency domain receive data leaked by the target user on the subcarriers occupied by the adjacent non-target users.
  • the interference cancellation module 20 may further calculate an orthogonalization factor by using the reconstructed channel estimation value of the target user and the reconstructed channel estimation value of the non-target user, and use the positive a cross-talking factor, orthogonalizing the channel of the non-target user to orthogonalize a channel of the target user with a channel of the non-target user, thereby eliminating frequency domain data of the non-target user Interference with adjacent subcarriers of the target user during transmission. That is, the interference cancellation module 20 first needs to extract the relevant frequency domain data according to step S101 of FIG. 1 and step 1 of the first embodiment and step 1 of the second embodiment, and then utilize the extracted frequency domain data and the reconstruction module. The calculated reconstructed channel estimation value is processed according to step S103 of FIG. 1 to obtain frequency domain received data of the local pilot of the target user that cancels the interference.
  • the frequency offset estimation module 30 is configured to utilize the local pilot of the target user that has cancelled the interference and The frequency domain receives the data and determines the frequency offset estimate.
  • the frequency offset estimation module 30 reconstructs the local pilot of the target user, obtains a reconstructed local pilot sequence, and receives local data and frequency domain received data and the reconstructed target user of the cancelled interference target user.
  • the local pilot sequences are respectively subjected to frequency-time transform to obtain time-domain received data and time-domain data sequences of the local pilot, and then the local pilot received time domain received data and the time-domain data sequence are subjected to conjugate correlation operations.
  • a phase sequence of the domain, and using the phase sequence of the time domain determines a frequency offset estimate.
  • the time domain data sequence of the local pilot may also be obtained by reconstructing a local mother code sequence of the target user, obtaining a reconstructed local mother code sequence, and performing the reconstructed local mother code sequence.
  • the time-frequency transform and the cyclic shift operation obtain a time-domain data sequence of the local pilot. That is, the frequency offset estimation module 30 sequentially performs step S104 to step S106 of FIG. 1 by using the local pilot and frequency domain received data of the target user for canceling interference, thereby determining the frequency offset estimation value.
  • FIG. 3 is a flowchart of frequency offset estimation processing of a frequency division user according to an embodiment of the present invention. As shown in FIG. 3, the method includes steps S201-S210:
  • Step S201 Extracting frequency domain data.
  • the extracted frequency domain data includes frequency domain data of subcarriers occupied by the target user and frequency domain data of subcarriers occupied by non-target users on adjacent subcarriers.
  • Step S202 Channel estimation.
  • the pilot symbol is first used to calculate the channel estimation value of the target user, and the calculation method may be a time domain method or a frequency domain method, and what method is adopted.
  • the embodiments of the invention are not limited.
  • channel estimation is also required, and channel estimation values of other users such as code division users are obtained.
  • Step S203 Reconstruction of the channel estimation value.
  • the number of reconstructed channel estimation values is greater than the number of subcarriers actually occupied by the target user.
  • Step S204 From step S201, the frequency domain data on the corresponding resource block is extracted for the calculation of step S205.
  • Step S205 The pilot receives the frequency domain data acquisition, that is, calculates the frequency domain received data of the local pilot, and may refer to the four cases given in step S103 in FIG. 1 according to different situations.
  • Step S206 The pilot receives the frequency-time transform of the frequency domain data, that is, converts the frequency domain received data into time domain received data.
  • Step S207 Reconstruct the local mother code sequence to obtain a reconstructed local mother code sequence.
  • Step S208 Perform frequency-time transform on the reconstructed local mother code sequence to obtain a corresponding data sequence for calculation in step S209.
  • Step S209 Calculating the phase sequence of the time domain by using the calculation results of step S206 and step S208.
  • Step S210 Calculate the frequency offset value by using the phase sequence of the time domain.
  • FIG. 4 is a flowchart of a frequency offset estimation process for strong correlation between users according to an embodiment of the present invention. As shown in FIG. 4, the method includes steps S301-S313:
  • Step S301 In a case where the channel between the two users does not satisfy the orthogonal or weak correlation (ie, the two users are strongly correlated), the channel orthogonalization factors of the two users are calculated by using the channel information acquired in the uplink.
  • Step S302 orthogonalizing channels of two users by using the channel orthogonalization factor Processing, that is, the originator is multiplied by the orthogonalization factor on the frequency domain data.
  • Step S303 The originator sends the frequency domain data after the orthogonalization process.
  • Step S304 Extract the frequency domain data.
  • the extracted frequency domain data includes frequency domain data of subcarriers occupied by the target user and frequency domain data of subcarriers occupied by non-target users on adjacent subcarriers.
  • Step S305 Channel estimation.
  • the channel estimation value of the target user needs to be calculated first, and the calculation method may be a time domain method or a frequency domain method, and the method is not used in the embodiment of the present invention. Make restrictions.
  • channel estimation is also required, and channel estimation values of other users such as code division users are obtained.
  • Step S306 Channel estimation value reconstruction.
  • the channel estimation value is reconstructed by using the channel estimation value of the target user, and the reconstructed channel estimation value of the target user is obtained.
  • Step S307 From step S304, the frequency domain data on the corresponding resource block is extracted for the calculation of step S308.
  • Step S308 The pilot receives the frequency domain data acquisition, that is, calculates the frequency domain received data of the local pilot, and may refer to the four cases given in step S103 in FIG. 1 according to different situations.
  • Step S309 The pilot receives the frequency-time transform of the frequency domain data, that is, converts the frequency domain received data into time domain received data.
  • Step S310 Reconstruct the local mother code sequence to obtain a reconstructed local mother code sequence.
  • Step S311 Perform frequency-time transform on the reconstructed local mother code sequence to obtain a corresponding data sequence for calculation in step S312.
  • Step S312 Calculate the phase sequence of the time domain by using the calculation results of step S309 and step S311.
  • Step S313 Calculate the frequency offset value by using the phase sequence of the time domain.
  • the embodiment of the invention provides a method and a device for frequency offset estimation using a single symbol for the synchronization problem of OFDM technology in the field of wireless communication, which is suitable for an OFDM system.
  • the embodiment of the present invention can effectively perform interference cancellation between users, thereby ensuring the frequency offset measurement accuracy of the users whose resources are discontinuously distributed.
  • any engineer having a background of knowledge such as signal processing, communication, etc.
  • can design a corresponding device according to the present invention and any modifications, equivalent replacements, improvements, etc., which are all included in the present invention.
  • the mind and scope can design a corresponding device according to the present invention, and any modifications, equivalent replacements, improvements, etc., which are all included in the present invention.
  • a computer readable storage medium storing computer executable instructions that, when executed by a processor, implement the frequency offset estimation method.
  • all or part of the steps of the above embodiments may also be implemented by using an integrated circuit. These steps may be separately fabricated into individual integrated circuit modules, or multiple modules or steps may be fabricated into a single integrated circuit module. achieve.
  • the devices/function modules/functional units in the above embodiments may be implemented by a general-purpose computing device, which may be centralized on a single computing device or distributed over a network of multiple computing devices.
  • the device/function module/functional unit in the above embodiment When the device/function module/functional unit in the above embodiment is implemented in the form of a software function module and sold or used as a stand-alone product, it can be stored in a computer readable storage medium.
  • the above mentioned computer readable storage medium may be a read only memory, a magnetic disk or an optical disk or the like.
  • the frequency offset measurement is performed by using non-continuously distributed pilot symbols such as a vane distribution, and the frequency domain data leaked from adjacent subcarriers is effectively used in the measurement process to perform frequency offset measurement, which ensures the guide well.
  • the frequency offset estimation performance in the case of discontinuous distribution of frequency symbols; and the frequency offset measurement accuracy of the target user is improved by eliminating or reducing interference between users.

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Abstract

本申请公开了一种频偏估计方法及装置，所述方法包括：对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到目标用户的重构信道估计值和非目标用户的重构信道估计值；利用目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据；利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值。

Description

一种频偏估计方法及装置 技术领域
本申请涉及但不限于通信领域，尤其涉及一种频偏估计方法及装置。
背景技术
新一代的移动通信系统要求具备高速率、高频谱效率、大容量的多媒体数据传输能力。在无线环境下高速数据传输会产生严重的频率选择性衰落，而正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术由于其突出的优点脱颖而出，成为瞩目的焦点。
OFDM是一种子载波相互正交的多载波传输技术，它将一个较宽的传输带宽分割成互相正交的多个子载波用于并行传输数据。其具有频谱利用率高、抗多径衰落、实现多入多出(Multiple-Input Multiple-Output，MIMO)技术简单等优点。然而，由于OFDM技术要求子载波之间相互正交的特性，对频偏非常敏感。
OFDM技术中，时偏的存在会造成符号间干扰(Inter-Symbol Interference，ISI)，从而对频偏估计的精度造成影响。虽然，由于OFDM引入了循环前缀的概念，在一定程度上抑制了时偏对它的影响，但是需要保证时偏不能过大，否则，数据也将受到严重的干扰，造成性能的损失。
可见，同步问题是OFDM技术核心问题之一，数十年来很多通信工程师提出了多种同步的解决方法。如果继续沿用连续导频符号的频偏估计方法对梳妆导频符号进行频偏估计，估计精度损失比较大。但对于如何利用梳妆分布等非连续分布的导频符号进行频偏估计，且保证相对于连续分布的导频符号没有损失，没有针对性的文献进行描述。
发明内容
以下是对本文详细描述的主题的概述。本概述并非是为了限制权利要 求的保护范围。
本申请的目的在于提供一种频偏估计方法及装置，能更好地解决利用梳妆分布等非连续分布导频符号进行频偏估计的问题。
一种频偏估计方法，包括：
对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到目标用户的重构信道估计值和非目标用户的重构信道估计值。
利用目标用户所占子载波的频域数据、相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据。
利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值。
可选地，所述对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到目标用户的重构信道估计值和非目标用户的重构信道估计值包括：
在所述目标用户所占用的资源块中，利用所述目标用户的信道估计值，计算相邻的非目标用户所占资源的信道估计值，并利用所述目标用户的信道估计值和所述相邻的非目标用户所占资源的信道估计值，确定所述目标用户的重构信道估计值。
在所述非目标用户所占用的资源块中，利用所述非目标用户的信道估计值，计算与所述非目标用户相邻的其他用户所占资源的信道估计值，并利用所述非目标用户的信道估计值和所述其他用户所占资源的信道估计值，确定所述非目标用户的重构信道估计值。
可选地，所述计算已消除干扰的目标用户的本地导频的频域接收数据包括：
当所述目标用户的信道与所述非目标用户的信道之间正交或弱相关时，将所述目标用户的频域数据与目标用户的重构信道估计值进行共轭相关运算，得到已消除干扰的目标用户的本地导频的频域接收数据。
可选地，所述计算已消除干扰的目标用户的本地导频的频域接收数据还包括：
当所述目标用户和所述非目标用户为梳分用户且两者信道之间强相关时，利用所述梳分用户的重构信道估计值，消除所述梳分用户在目标用户的相邻子载波上的干扰数据，得到已消除干扰的目标用户的本地导频的频域接收数据；或者，
当所述目标用户与所述非目标用户为码分用户且两者信道之间强相关时，利用最小均方误差算法或迫零算法，对目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值进行处理，得到目标用户所占子载波的频域接收数据和目标用户在相邻非目标用户所占子载波上泄露的频域接收数据。
可选地，所述计算已消除干扰的目标用户的本地导频的频域接收数据还包括：
利用所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值，计算正交化因子，并利用所述正交化因子，对所述非目标用户的信道进行正交化处理，使所述目标用户的信道与所述非目标用户的信道之间正交，消除所述非目标用户的频域数据在发送期间对目标用户的相邻子载波的干扰。
可选地，所述利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值包括：
对所述目标用户的本地导频进行重构，得到重构本地导频序列。
对所述已消除干扰的目标用户的本地导频及频域接收数据和所述重构本地导频序列分别进行频时变换，得到本地导频的时域接收数据和时域数据序列。
利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到频偏估计值。
可选地，所述利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包括：
对所述目标用户的本地母码序列进行重构，得到重构本地母码序列。
对所述重构本地母码序列进行频时变换和循环移位操作，得到本地导频的时域数据序列。
可选地，所述利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到频偏估计值还包括：
将所述本地导频的时域接收数据和时域数据序列进行共轭相关运算，得到域的相位序列，并利用所述时域的相位序列，确定频偏估计值。
一种频偏估计装置，包括：
重构模块，设置为对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到目标用户的重构信道估计值和非目标用户的重构信道估计值。
干扰消除模块，设置为利用目标用户所占子载波的频域数据、相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据。
频偏估计模块，设置为利用所述已消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值。
可选地，所述重构模块包括：
第一重构子模块，设置为在所述目标用户所占用的资源块中，利用所述目标用户的信道估计值，计算相邻的非目标用户所占资源的信道估计值，并利用所述目标用户的信道估计值和所述相邻的非目标用户所占资源的信道估计值，确定所述目标用户的重构信道估计值。
第二重构子模块，设置为在所述非目标用户所占用的资源块中，利用所述非目标用户的信道估计值，计算与所述非目标用户相邻的其他用户所占资源的信道估计值，并利用所述非目标用户的信道估计值和所述其他用户所占资源的信道估计值，确定所述非目标用户的重构信道估计值。
可选地，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据包括：当所述目标用户的信道与所述非目标用户的信道之间正交或弱相关时，将所述目标用户的频域数据与目标用户的重构信道估计值进行共轭相关运算，得到已消除干扰的目标用户的本地导频的频域接收数据。
可选地，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据还包括：当所述目标用户和所述非目标用户为梳分用户且两者信道之间强相关时，利用所述梳分用户的重构信道估计值，消除所述梳分用户在目标用户的相邻子载波上的干扰数据，得到已消除干扰的目标用户的本地导频的频域接收数据，或者，当所述目标用户与所述非目标用户为码分用户且两者信道之间强相关时，利用最小均方误差算法或迫零算法，对目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值进 行处理，得到目标用户所占子载波的频域接收数据和目标用户在相邻非目标用户所占子载波上泄露的频域接收数据。
可选地，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据还包括：利用所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值，计算正交化因子，并利用所述正交化因子，对所述非目标用户的信道进行正交化处理，使所述目标用户的信道与所述非目标用户的信道之间正交，消除所述非目标用户的频域数据在发送期间对目标用户的相邻子载波的干扰。
可选地，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值包括：对所述目标用户的本地导频进行重构，得到重构本地导频序列，并对所述已消除干扰的目标用户的本地导频及频域接收数据和所述重构本地导频序列分别进行频时变换，得到本地导频的时域接收数据和时域数据序列，利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到频偏估计值。
可选地，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包括：对所述目标用户的本地母码序列进行重构，得到重构本地母码序列，并对所述重构本地母码序列进行频时变换和循环移位操作，得到本地导频的时域数据序列。
可选地，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包括：将所述本地导频的时域接收数据和时域数据序列进行共轭相关运算，得到时域的相位序列，并利用所述时域的相位序列，确定频偏估计值。
一种计算机可读存储介质，存储有计算机可执行指令，所述计算机可执行指令被处理器执行时实现所述的频偏估计方法。
本发明实施例方案利用梳妆分布等非连续分布的导频符号进行频偏测量，在测量过程中有效的利用相邻子载波上泄漏过来的频域数据进行频偏测量，很好地保证了导频符号非连续分布情况下的频偏估计性能；并且通过消除或者消减用户间的干扰，提升了目标用户的频偏测量精度。
附图概述
图1是本发明实施例提供的频偏估计方法原理框图；
图2是本发明实施例提供的频偏估计装置框图；
图3是本发明实施例提供的频分用户的频偏估计处理流程图；
图4是本发明实施例提供的用户间强相关的频偏估计处理流程图；
图5是本发明实施例提供的梳分用户的第一资源映射图；
图6是本发明实施例提供的频分用户的第二资源映射图。
本发明的实施方式
下文中将结合附图对本发明的实施例进行详细说明。需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互任意组合。
图1是本发明实施例提供的频偏估计方法原理框图，本发明实施例主要针对梳妆分布等非连续分布情况下利用单符号导频进行频偏估计，该方法不仅仅适用于下行的频偏测量，同时也适用于上行的频偏测量。本发明实施例在进行频偏估计过程中，不仅仅利用目标子载波上的频偏信息，同时也利用了在相邻子载波上泄漏的频偏信息进行频偏估计，能够大大提升梳妆分布或者非连续分布情况下的单符号的频偏估计精度。如图1所示，本实施例内容包括步骤S101-S105：
步骤S101：目标用户的导频频域数据(以下简称频域数据)的提取。 用Y表示提取出来的该目标用户的频域数据。
在提取目标用户的频域数据的过程中，需要把相邻子载波上非目标用户的频域数据同时也提取出来。
在提取过程中，如果该目标用户的两两子载波间隔比较大，在实际提取过程中可以只提取该目标用户子载波相邻L个非目标用户的子载波数据，本发明实施例对此不做限制，考虑到实现复杂度L的最大取值为3。
步骤S102：信道估计值的重构。重构后的信道估计值用H表示。
利用梳妆分布等非连续分布导频符号，结合业内成熟的最小二乘算法(Least Square，LS)或迫零算法(Zero Forcing，ZF)等算法，获取目标用户所占子载波(即目标子载波)的信道估计值。
在频偏估计的过程中，除了需要利用目标子载波的相邻非目标用户子载波的数据，同时需要获取对应的信道估计值。
考虑到信道频选特性的变化相对比较连续或者比较缓慢，因此，在实际实现中可以利用该目标用户的目标子载波的信道估计值平推获取相邻非目标用户资源上的信道估计值，例如，通过平推，相邻非目标用户资源上的信道估计值确定为目标用户的目标子载波的信道估计值；或者可以采用该目标用户的两两子载波插值的方式获取非目标用户资源上的信道估计值，例如，通过插值，相邻非目标用户资源上的信道估计值确定为目标用户占用的两个子载波所对应的两个信道估计值之间的任意值。对此，采用什么方式获取非目标用户资源数据上的信道估计值，本发明实施例不作限制，优选两两子载波间隔为如图5所示的1个子载波，例如探测参考信号(Sounding Reference Signal，SRS)的资源分布方式，可以采用平推的方式获取相邻非目标用户资源上的信道估计值；当间隔为如图6所示的2个子载波时，对应的信道估计可以通过该目标用户相邻的子载波上的数据以平推 的方式获取；当间隔大于2个子载波时，可以通过该目标用户的两个子载波上的数据以插值的方式获取非目标用户数据位上的信道估计值。
需要说明的是，如果在实际应用过程中，数据上存在码分用户，或者相邻的频域数据上存在其他用户的数据，为了避免用户间的干扰，码分用户至少需要保证用户间的导频是正交的，这样才能保证获取准确的信道估计值。
步骤S103：利用步骤S101和步骤S102获取的该目标用户的频域数据和信道估计值，进行两两之间的相关运算计算接收到的本地导频数据(即本地导频的频域接收数据)。
需要说明的是，如果目标用户所占用的资源上没有码分用户，或者相邻的子载波上也没有分配给其他用户，或者没有发其他信道数据，这种情况下，获取目标用户的本地导频的频域接收数据的计算方式比较简单，即直接利用步骤S101获取的频域数据和步骤S102重构的信道估计值进行相关运算；如果目标用户所占的资源上有码分用户等其它用户的情况，除了要保证码分用户之间的导频码的正交性，同时需要保证码分用户之间的信道弱相关；如果目标用户所占的资源块上存在其他梳分用户，同样需要保证梳分用户之间的导频正交性和梳分用户之间的信道的弱相关，其中，所述梳分用户指导频符号满足梳妆分布的用户，所述梳妆分布的导频符号在频域方向等间隔映射，而非连续映射，如图5所示。为了便于对本发明实施例的思想的描述，本步骤主要分以下四种情况处理：
第一种情况，目标用户所占用资源块上没有其他码分用户和梳分用户。
在这种情况下，如下处理比较简单，不需要考虑用户间的干扰消除。假设步骤S102重构的信道估计值H和提取出来的目标用户的频域数据Y， 所述目标用户的频域数据Y包括每个子载波上相邻的非目标用户的L个子载波的数据，该数据包含本用户所占子载波上泄漏过来的内部载波干扰(Inter Carrier Interference，ICI)能量和噪声干扰能量，也就是说，由于用户导频符号频域上是非连续分布的，其中间隔的有非目标用户所占资源，这里非目标用户所占资源即为L。利用如上重构的信道估计值H和提取出来的频域数据Y进行共轭相关计算，从而计算得到本地导频的频域接收数据，即
Figure PCTCN2016083351-appb-000001
第二种情况，目标用户所占资源块上只有梳分用户，但是没有调度码分用户。
在这种情况下，需要考虑用户间的干扰消除。如果梳分用户的信道之间满足正交或弱相关，那么处理的时候相对比较简单，直接用提取出来的目标用户的频域数据和重构的目标用户的信道估计值进行共轭相关，由于两用户的信道是正交的或者弱相关，能够减弱或消除梳分用户对目标用户的干扰；如果梳分用户的信道之间不能保证正交或者弱相关，则利用两用户的导频码的正交性进行干扰消除，比如假设目标用户相邻子载波上的频域数据表示为Y1＝αH1X1+βH2X2，其中X1表示目标用户的本地导频频域数据，X2表示梳分用户的本地导频频域数据，α和β表示因为信道或者采样偏移等导致的功率衰减因子，Y1表示的是目标用户某一相邻子载波上的频域数据，该子载波为梳分用户所占的资源。因此，针对这种情况下，首先获取梳分用户的信道估计值
Figure PCTCN2016083351-appb-000002
信道估计的计算方法可以用时域方法，也可以用频域方法，在此不做详细说明。由于两用户之间的本地导频序列是正交的，在信道估计的过程中能够消除另外一个用户对目标用户的干扰。以上述描述过程中所提供的公式为例，利用计算得到的梳分用的信道估计消除该用户对目标用户的干扰，即对目标用户的相邻子载波上的数据进行 干扰消除
Figure PCTCN2016083351-appb-000003
利用如此操作消除目标用户相邻子载波上的干扰数据，得到消除干扰后的频域数据
Figure PCTCN2016083351-appb-000004
也就是目标用户在该子载波上的泄漏能量。本发明实施例相对于传统的梳分的频偏计算的方法所不同的地方就是在估计的时候利用泄漏在非目标用户子载波上的数据进行频偏估计，即将相邻的非目标用户的频域数据参与到目标用户的频偏估计过程中，本步骤利用干扰消除后的频域数据和信道估计值进行共轭相关运算，从而获取本地导频的频域接收数据。另外，对于这种情况，也可以采用最小均方误差算法(Minimum Mean Square Error，MMSE)或者ZF等干扰消除的方法，同时获取目标用户在本载波上的频域数据和泄漏到相邻子载波的频域数据，通过这种方法能够有效的消除梳分用户对目标用户的干扰，但是实现复杂度比较大，在本配置下不作优选方案。
另外，在两个用户之间的信道不满足正交或者弱相关的情况下，还可以采用Gram-Schmidt正交化的思路对两个用户的信道进行正交化，对发端用户的信道进行正交化处理。该思路主要用于时分双工(Time Division Duplex，TDD)制式，主要考虑TDD模式下上下行信道是对称的，利用上行获取的信道信息，计算两个用户信道正交化的向量，即正交化因子w，基于前面所构建的信道模型中对目标用户和梳妆用户的信道估计值分别定义为H1和H2，则
Figure PCTCN2016083351-appb-000005
其中，
Figure PCTCN2016083351-appb-000006
然后利用正交化因子w，对梳分用户的信道进行正交化处理，即利用该因子对该用户的信道在发端进行正交化预处理，即在发端在频域数据上左乘以正交化因子w。
第三种情况，在目标用户所占的资源块上，没有调度梳分用户，但存在码分用户。
针对这种情况下的处理，如果码分用户之间的信道是正交或者弱相关，在这种情况下的处理相对比较简单，直接利用步骤S101的目标用户的频域数据与步骤S102的目标用户的信道估计值进行共轭相关运算，由于信道之间是正交的或者是弱相关，此操作能够减弱或者消除码分用户对目标用户的干扰；如果码分用户间的信道不满足正交或者弱相关的特点，这种情况下，如果采用上述方法会对最终估计的性能有影响。针对这种情况下，可以采用两种思路进行解决，其一，忽略用户间干扰的影响，直接利用前面步骤S101的频域数据和骤S102的信道估计值进行频偏估计，该方法优点是处理比较简单，缺点就是存在码分用户对目标用户的干扰，影响最终的测量精度；其二，需要考虑码分用户间的干扰消除，消除方法可以采用MMSE或ZF等方法，用前面所述步骤S101提取出来的频域数据和步骤S102的信道估计结果进行干扰消除，从而获取对应的数据。假设两个码分用户的配置下，目标用户所占的子载波上的接收数据表示为
Figure PCTCN2016083351-appb-000007
相邻非目标用户所占资源上的接收数据
Figure PCTCN2016083351-appb-000008
这时可以利用干扰消除的方法计算得到目标用户所占资源上对应子载波上的频域数据和其相邻非目标用户子载波上目标用户泄漏的数据能量，以采用ZF为例分别计算得到
Figure PCTCN2016083351-appb-000009
和
Figure PCTCN2016083351-appb-000010
由于对于每个用户都包含相邻多个子载波的能量泄漏，泄漏的能量大小与子载波间隔和采样偏移有关，在通常的情况下只考虑相邻的M个子载波进行干扰消除。除此之外，本发明实施例提出了另外一种解决思路就是对码分两用户之间的信道进行正交化处理，处理方法参见第二种情况下，在此不再进行赘述。
对于码分用户，也可以从调度的角度来消弱用户间的干扰，从而降低低层的处理复杂度，即在调度的时候需要保证码分的两用户的频率偏移是 同方向的或者两用户的频偏偏移的差异很小。在计算的时候，由于码分用户之间的的导频数据存在一个固定的相位偏移，把该相位偏移转移到信道估计值中进行计算目标用户的本地导频的接收频域数据，即
Figure PCTCN2016083351-appb-000011
这种计算方式不需要关注两个用户之间的信道正交性，只要保证码分的两个用户的频率偏移值差异很小，其中α为码分用户相对于目标用户的循环移位因子。
第四种情况，在目标用户所占的资源块上，不仅有梳分用户，也存在码分用户。
针对这种情况，如果目标用户与梳分和码分用户之间的信道是正交的或者是弱相关。在这种情况下的处理相对比较简单，直接利用前面步骤S101的目标用户的频域数据(包括相邻资源上的频域数据)与步骤S102的目标用户的信道估计值进行共轭相关运算，由于两用户的信道是正交的或者是弱相关，在如上操作下能够消除码分或者梳分用户的干扰；如果目标用户与梳分或者码分用户之间的信道是正交的或者是弱相关的，而与另一用户的信道是较强相关，这种情况下的处理方法参考第二种情况或者第三种情况的处理方式；如果目标用户与梳分和码分用户之间的信道都是较强相关的，针对这种情况下，可以采用三种思路进行解决，其一，不考虑目标用户与梳分用户或者码分用户之间的干扰，直接利用目标所占的资源上的频域数据和对应的信道估计值进行共轭相关运算。需要说明的是所采用的频域数据与前面所述的频域数据的提取方法有所不同，只提取目标用户所占的资源上的频域数据，不考虑泄漏的数据能量，该方法测量的精度偏低，会受到码分和梳分用户的干扰，估计精度会受用户间干扰影响。其二，不考虑梳分用户对目标用户的影响，在实现过程中，利用计算得到的梳分用户的信道估计值和本地导频数据，对目标用户的相邻子载波上的梳分用户的数据进行消除，从而获取目标用户与码分用户的对相邻子载波的 梳分用户的数据泄露能量。对于码分用户的处理具体方法就可以参考第三种情况的处理方式，在此不再赘述。其三，考虑码分和梳分用户的干扰消除，对于该情况首先可以采用Gram-Schimdt正交化的方法，使得码分用户和梳分用户与目标用户的信道正交，然后利用常规的思路获取目标用户的本地导频的频域接收数据。
步骤S104：对目标用户的本地导频序列进行重构。
需要说明的是，可以采用两种思路进行处理。其一，直接对目标用户的本地导频序列进行重构，其二，对目标用户所对应的母码序列进行重构。
此过程相对比较简单，重构后的本地导频序列或者本地母码序列的长度与前面重构后的频域数据的长度是相同的，其中非目标用户所占的子载波上所对应的导频序列或者母码序列为0。
步骤S105：对前面计算得到的本地导频的频域接收数据和重构的本地导频序列/本地母码序列进行频时变换。
在变换的过程中可以采用离散傅里叶逆变换(Inverse Discrete Fourier Transform，IDFT)变换，也可以采用快速傅里叶逆变换(Inverse fast Fourier transform，IFFT)变换，或者其他频时变换，在此不做限制。
需要说明的是，如果步骤S104所采用的是本地母码序列，则变换到时域的时候，根据该用户对应的循环移位恢复成该用户的导频所对应的时域序列。
步骤S106：利用前面所计算得到的本地导频序列/本地母码序列对应的时域序列和频域接收数据对应的时域序列，进行频偏测量。
该步骤主要利用频偏在时域会产生线性相位的特点进行计算，在实现的过程中可以采用两两点之间的相位差或者前半部分和后半部分的相位差 或者把相位序列分成若干个小段，然后计算两两小段之间的相位差。最后，基于以上描述的相位差，获取最终的频偏估计值。由于此过程不属于本发明的主要思想点，在此不做详细描述。
以下两个实施例以SRS为例，对本发明实施例进行说明。
实施例一
本实施例中，只有频分用户，没有梳分用户和码分用户。由于SRS的资源分布是梳妆分布，且如图6所示，频分用户的两个子载波间隔L＝2,在如下过程中，以SRS的分配资源位24RB，其中有效资源为12RB，实现过程描述如下，包括步骤一至步骤六：
步骤一：目标用户的频域数据的提取。
需要说明的是，如果接收到的数据为时域数据，首先需要变换导频频域，对于时频变化是长期演进(Long Term Evolution,LTE)常见的处理，在此不做详细描述。在进行目标用户的频域数据的提取过程中，不仅仅要提取目标用户的所占的子载波的数据，同时也要提取出相邻子载波上(非目标用户所占用的子载波数据)的频域数据,提取出来的频域数据用Yk表示，其中k为子载波索引，k＝0,1,…,287。
步骤二：目标用户的信道估计的重构。
如果没有获取到该目标用户的信道估计值，则首先需要进行该目标用户的信道估计值的计算，计算方法可以采用时域方法，也可以采用频域方法，至于采用什么方法本发明不做限制；如果获取到该目标用户的信道估计值，则需要利用估计的信道估计值进行信道估计的重构。重构的主要思路是对目标用户所占的资源块中，非目标用户所占用的资源上的信道估计值通过相邻的目标用户子载波所对应的信道估计平推得到，考虑到信道频选变换不会很快，建议采用平推的方式，但不局限于此方式，可以采用线 性插值或者非线性插值而得到。本实施例以平推的方式来重构非目标用户所占资源上的信道估计值，假设目标用户的信道估计值Hk，其中k＝0,1,…,143，则重构后的信道估计值表示为
Figure PCTCN2016083351-appb-000012
如果目标用户的导频符号是梳妆分布，其对应的频域资源位置上的信道估计值就是目标用户的目标子载波上的信道估计值Hk，其每个子载波上相邻的且没有分配给目标用户的资源上的信道估计值就是非目标用户资源数据上的信道估计值，而对于重构后的信道估计值
Figure PCTCN2016083351-appb-000013
由前两者构成，即
Figure PCTCN2016083351-appb-000014
中包含Hk。
步骤三：本地导频的频域接收数据的计算。
此过程的计算，为直接利用前面提取的频域数据和重构好的该目标用户的信道估计值进行共轭相乘，从而消除所接收到的数据的信道影响，即计算得到的本地导频的频域接收数据，表示为
Figure PCTCN2016083351-appb-000015
需要说明的是，在导频非连续分布的情况下，目标用户所占的资源块上不仅仅包括目标用户的资源，还包括空闲资源，甚至其他用户的资源，因此目标用户的重构后的信道估计值的个数要大于目标用户实际占用的子载波个数。
步骤四：对目标用户的本地导频序列进行重构。
需要说明的是，可以采用两种思路进行处理，其一，直接对目标用户的导频序列进行重构，其二，对目标用户所对应的母码序列进行重构。此过程相对比较简单，重构后的本地导频序列或者母码序列的长度与前面重构后的频域数据的长度是相同的，其中非目标用户所占的子载波上所对应的导频序列值或者母码序列值为0。本实施例对目标用户的本地导频序列进行重构为例，本地导频序列用Xk表示，其中k＝0,1,…,143，则重构后的本地导频序列表示为
Figure PCTCN2016083351-appb-000016
即
Figure PCTCN2016083351-appb-000017
其中k＝0,1,…,143。
步骤五：对前面计算得到的本地导频的频域接收数据和重构的本地导频序列进行频时变换。
在变换的过程中可以采用IDFT变换，也可以采用IFFT变换，或者其他方法的频时变换，本实施例以采用IFFT方式进行频时变换。由于前面重构后的数据长度为288，但是IFFT变换的长度为2n，则首选需要对前面的本地导频序列和计算得到的本地导频的频域接收数据的尾部进行插零处理，满足长度为2n，即首先对两个频域数据插224个零，然后对插零后的频域数据进行IFFT变换，从而获取到本地导频序列对应的时域序列Txn(即本地导频的时域数据序列)，本地导频的频域接收数据对应的时域数据Rxn(即本地导频的时域接收数据)，其中n＝0,1,…,511。
步骤六，利用前面计算得到的本地导频的时域数据序列Txn和时域接收数据Rxn进行频偏测量。
该步骤主要是利用频偏在时域会产生线性相位的特点进行计算，在实现的过程中可以采用两两点之间的相位差或者前半部分和后半部分的相位差或者把相位序列分成若干个小段，然后计算两两小段之间的相位差。最后，基于以上描述的相位差从而获取最终的频偏估计值。过程如下，包括子步骤一至子步骤二：
子步骤一：利用前面计算得到的本地导频的时域数据序列Txn和本地导频的时域接收数据Rxn进行共轭相关运算，从而获取由于频偏导致的相位序列WR,即WRn＝Txn×(Rxn)* n＝0,1,…,511。
子步骤二：利用频偏产生的相位在时域是线性的关系进行频偏估计，在估计的时候可以采用两两相邻的样点进行频偏估计，也可以采用等间隔或者不间隔的方式进行频偏估计，采用哪种方法本发明实施例不做限制。另外，在计算频偏时，可以对相位序列进行截取操作，即可以利用其中部 分的相位序列进行频偏估计，在此不做限制。下面的描述采用全部相位序列进行频偏估计，实施例如下，采用前半部分和后半部分的相位差进行频偏估计，即
Figure PCTCN2016083351-appb-000018
其中，Δf为子载波间隔的大小；
Figure PCTCN2016083351-appb-000019
实施例二
本实施例中，存在码分用户，不存在频分用户。本实施例通过调度的方式保证目标用户和码分用户之间的频率偏移值相同，并假设两个用户之间导频序列的循环移位差异为π，实现过程描述如下，包括步骤1至步骤6：
步骤1：目标用户的频域数据的提取。
需要说明的是，如果接收到的数据为时域数据，首先需要变换导频频域，对于时频变化是LTE常见的处理，在此不做详细描述。在进行目标用户的频域数据的提取过程中，不仅仅要提取目标用户的所占的子载波的数据，同时也要提取出相邻子载波上(非目标用户所占用的子载波数据)的频域数据,提取出来的频域数据用Yk表示，其中k＝0,1,…,287。
步骤2：目标用户的信道估计的重构。
如果没有获取到该目标用户的信道估计值，则首先需要进行该目标用户的信道估计值的计算，计算方法可以采用时域方法，也可以采用频域方法，至于采用什么方法本发明不做限制；如果获取到该目标用户的信道估计值，则需要利用估计的信道估计值进行信道估计的重构。重构的主要思路是对目标用户所占的资源块中，非目标用户所占用的资源上的信道估计值通过相邻的目标用户子载波所对应的信道估计平推得到，考虑到信道频 选变换不会很快，建议采用平推的方式，但不局限于此方法，可以采用线性插值或者非线性插值而得到。本实施例以平推的方式来重构非目标用户所占资源上的信道估计值，假设目标用户的信道估计值
Figure PCTCN2016083351-appb-000020
其中k＝0,1,…,143，则重构后的信道估计值表示为
Figure PCTCN2016083351-appb-000021
同样，需要获取码分用户的信道估计值，采用方法同目标用户一样，可以采用时域方法，也可以采用频域方法，采用哪种方法在此不做限制，假设码分用户的信道估计值
Figure PCTCN2016083351-appb-000022
其中k＝0,1,…,143，则重构后的信道估计值表示为
Figure PCTCN2016083351-appb-000023
步骤3：本地导频接收的频域数据(即本地导频的频域接收数据)的计算。
此过程的计算，需要考虑码分用户之间的干扰消除，即计算得到的本地导频的频域接收数据表示为
Figure PCTCN2016083351-appb-000024
Figure PCTCN2016083351-appb-000025
其中，α是
Figure PCTCN2016083351-appb-000026
相对于
Figure PCTCN2016083351-appb-000027
的循环移位，也就是用户2相对于用户1的导频循环移位。
步骤4：对目标用户的本地导频序列进行重构。
需要说明的是，可以采用两种思路进行处理，其一，直接对目标用户的导频序列进行重构，其二，对目标用户所对应的母码序列进行重构。此过程相对比较简单，重构后的本地导频序列或者母码序列的长度与前面重构后的频域数据的长度是相同的，其中非目标用户所占的子载波上所对应的导频序列值或者母码序列值为0。本实施例以对目标用户的本地导频序列进行重构为例，本地导频序列用Xk表示，其中k＝0,1,…,143，则重构后本地导频序列表示为
Figure PCTCN2016083351-appb-000028
即
Figure PCTCN2016083351-appb-000029
其中k＝0,1,…,143。
步骤5：对前面计算得到的本地导频的频域接收数据和重构的本地导频 序列进行频时变换。
在变换的过程中可以采用IDFT变换，也可以采用IFFT变换，或者其他方法的频时变换，本实施例以采用IFFT方式进行频时变换。由于前面重构后的数据长度为288，但是IFFT变换的长度为2n，则首选需要对如上的本地导频的频域数据(即本地导频序列)和计算得到的本地导频的频域接收数据的尾部进行插零处理，满足长度为2n，即首先对两个频域数据插224个零，然后对插零后的频域数据进行IFFT变换，从而获取到本地导频的时域数据序列Txn，本地导频的时域接收数据Rxn，其中n＝0,1,…,511。
步骤6：利用前面计算得到的本地导频的时域数据序列Txn和时域接收数据Rxn进行频偏测量。
该步骤主要是利用频偏在时域会产生线性相位的特点进行计算，在实现的过程中可以采用两两点之间的相位差或者前半部分和后半部分的相位差或者把相位序列分成若干个小段，然后计算两两小段之间的相位差。最后，基于以上描述的相位差从而获取最终的频偏估计值。过程如下，包括子步骤1至子步骤2：：
子步骤1：利用前面计算得到的本地导频的时域数据序列Txn和本地导频的时域接收数据Rxn进行共轭相关运算，从而获取由于频偏导致的相位序列WR,即
Figure PCTCN2016083351-appb-000030
子步骤2：利用频偏产生的相位在时域是线性的关系进行频偏估计，在估计的时候可以采用两两相邻的样点进行频偏估计，也可以采用等间隔或者不间隔的方式进行频偏估计，采用哪种方法本发明实施例不做限制。另外，在计算频偏时，可以对相位序列进行截取操作，即可以利用其中部分的相位序列进行频偏估计，在此不做限制。下面的描述采用全部相位序列进行频偏估计，实施例如下，采用前半部分和后半部分的相位差进行频偏 估计，即
Figure PCTCN2016083351-appb-000031
其中，Δf为子载波间隔的大小；
Figure PCTCN2016083351-appb-000032
图2是本发明实施例提供的频偏估计装置框图，如图2所示，包括：重构模块10、干扰消除模块20和频偏估计模块30。
重构模块10设置为对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到目标用户的重构信道估计值和非目标用户的重构信道估计值。所述重构模块10包括第一重构子模块和第二重构子模块，其中，第一重构子模块设置为在所述目标用户所占用的资源块中，利用所述目标用户的信道估计值，计算相邻的非目标用户所占资源的信道估计值，并利用所述目标用户的信道估计值和所述相邻的非目标用户所占资源的信道估计值，确定所述目标用户的重构信道估计值；第二重构子模块设置为在所述非目标用户所占用的资源块中，利用所述非目标用户的信道估计值，计算与所述非目标用户相邻的其他用户所占资源的信道估计值，并利用所述非目标用户的信道估计值和所述其他用户所占资源的信道估计值，确定所述非目标用户的重构信道估计值。第一重构子模块和第二重构子模块的重构处理步骤可以参考图1的步骤S102即其实施例一的步骤二和实施例二的步骤2，在此不再赘述。
干扰消除模块20设置为利用目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据。
可以按照以下几种方式进行干扰消除：
1、如果所述目标用户的信道与所述非目标用户的信道之间正交或弱相关，则干扰消除模块20在将所述目标用户的频域数据与目标用户的重构信道估计值进行共轭相关运算，得到已消除干扰的目标用户的本地导频的频域接收数据。
2、如果所述目标用户和所述非目标用户为梳分用户且两者信道之间强相关，则干扰消除模块20利用所述梳分用户的重构信道估计值，消除所述梳分用户在目标用户的相邻子载波上的干扰数据，得到已消除干扰的目标用户的本地导频的频域接收数据。
3、如果所述目标用户与所述非目标用户为码分用户且两者信道之间强相关，则干扰消除模块20利用最小均方误差算法或迫零算法，对目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值进行处理，得到目标用户所占子载波的频域接收数据和目标用户在相邻非目标用户所占子载波上泄露的频域接收数据。
4、除上述几种情况外，干扰消除模块20还可以利用所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值，计算正交化因子，并利用所述正交化因子，对所述非目标用户的信道进行正交化处理，使所述目标用户的信道与所述非目标用户的信道之间正交，从而消除所述非目标用户的频域数据在发送期间对目标用户的相邻子载波的干扰。也就是说，干扰消除模块20首先需要按照图1的步骤S101即其实施例一的步骤一和实施例二的步骤1提取相关的频域数据，然后利用所提取的频域数据和重构模块10计算的重构信道估计值，按照图1的步骤S103处理，得到消除干扰的目标用户的本地导频的频域接收数据。
频偏估计模块30设置为利用所述已消除干扰的目标用户的本地导频及 频域接收数据，确定频偏估计值。频偏估计模块30对所述目标用户的本地导频进行重构，得到重构本地导频序列，并对所述已消除干扰的目标用户的本地导频及频域接收数据和所述重构本地导频序列分别进行频时变换，得到本地导频的时域接收数据和时域数据序列，然后将所述本地导频的时域接收数据和时域数据序列进行共轭相关运算，得到时域的相位序列，并利用所述时域的相位序列，确定频偏估计值。其中，本地导频的时域数据序列还可以通过以下方式获取：对所述目标用户的本地母码序列进行重构，得到重构本地母码序列，并对所述重构本地母码序列进行频时变换和循环移位操作，得到本地导频的时域数据序列。也就是说，频偏估计模块30利用所述消除干扰的目标用户的本地导频及频域接收数据依次执行图1的步骤S104至步骤S106，从而确定频偏估计值。
图3是本发明实施例提供的频分用户的频偏估计处理流程图，如图3所示，包括步骤S201-S210：
步骤S201：提取频域数据。
所提取的频域数据包括目标用户所占子载波的频域数据和相邻子载波上非目标用户所占子载波的频域数据。
步骤S202：信道估计。
如果没有获取到该目标用户的信道估计值，则首先需要利用导频符号进行该目标用户的信道估计值的计算，计算方法可以采用时域方法，也可以采用频域方法，至于采用什么方法本发明实施例不做限制。
同样地，如果有码分用户等其它用户，也需要进行信道估计，得到码分用户等其它用户的信道估计值。
步骤S203：信道估计值重构。
利用目标用户的信道估计值进行信道估计值重构，得到目标用户的重 构的信道估计值。
同样地，如果有码分用户等其它用户，也需要进行信道估计值重构，得到码分用户等其它用户的重构的信道估计值。
需要注意的是，由于导频符号非连续分布，因此重构的信道估计值的个数要大于目标用户实际占用的子载波个数。
步骤S204：从步骤S201中，提取相应资源块上的频域数据，以供步骤S205的计算。
步骤S205：导频接收频域数据获取，即计算本地导频的频域接收数据，根据情况不同，可以参考图1中步骤S103给出的四种情况处理。
步骤S206：导频接收频域数据的频时变换，即将频域接收数据变换为时域接收数据。
步骤S207：对本地母码序列进行重构，得到重构后的本地母码序列。
步骤S208：对重构后的本地母码序列进行频时变换，得到相应数据序列，以供步骤S209的计算。
步骤S209：利用步骤S206和步骤S208的计算结果，计算时域的相位序列。
步骤S210：利用所述时域的相位序列，对频偏值进行计算。
图4是本发明实施例提供的用户间强相关的频偏估计处理流程图，如图4所示，包括步骤S301-S313：
步骤S301：在两个用户之间的信道不满足正交或者弱相关的情况下(即两个用户强相关)，利用上行获取的信道信息，计算两个用户的信道正交化因子。
步骤S302：利用所述信道正交化因子，对两个用户的信道进行正交化 处理，即发端在频域数据上左乘以正交化因子。
步骤S303：发端发送所述正交化处理之后的频域数据。
步骤S304：提取频域数据。
所提取的频域数据包括目标用户所占子载波的频域数据和相邻子载波上非目标用户所占子载波的频域数据。
步骤S305：信道估计。
如果没有获取到该目标用户的信道估计值，则首先需要进行该目标用户的信道估计值的计算，计算方法可以采用时域方法，也可以采用频域方法，至于采用什么方法本发明实施例不做限制。
同样地，如果有码分用户等其它用户，也需要进行信道估计，得到码分用户等其它用户的信道估计值。
步骤S306：信道估计值重构。
利用目标用户的信道估计值进行信道估计值重构，得到目标用户的重构的信道估计值。
同样地，如果有码分用户等其它用户，也需要进行信道估计值重构，得到码分用户等其它用户的重构的信道估计值。
步骤S307：从步骤S304中，提取相应资源块上的频域数据，以供步骤S308的计算。
步骤S308：导频接收频域数据获取，即计算本地导频的频域接收数据，根据情况不同，可以参考图1中步骤S103给出的四种情况处理。
步骤S309：导频接收频域数据的频时变换，即将频域接收数据变换为时域接收数据。
步骤S310：对本地母码序列进行重构，得到重构后的本地母码序列。
步骤S311：对重构后的本地母码序列进行频时变换，得到相应数据序列，以供步骤S312的计算。
步骤S312：利用步骤S309和步骤S311的计算结果，计算时域的相位序列。
步骤S313：利用所述时域的相位序列，对频偏值进行计算。
本发明实施例针对无线通讯领域中OFDM技术的同步问题给出了采用单符号进行频偏估计的方法及装置，适用于OFDM系统。
本发明实施例在频偏估计过程中，能够有效进行用户间的干扰消除，从而保证资源是非连续分布的用户的频偏测量精度。
根据本发明实施例公开的技术方案，任何具有信号处理，通信等知识背景的工程师，都可以根据本发明设计相应的装置，所作的任何修改、等同替换、改进等，其均应包含在本发明的思想和范围内。
一种计算机可读存储介质，存储有计算机可执行指令，所述计算机可执行指令被处理器执行时实现所述的频偏估计方法。
本领域普通技术人员可以理解上述实施例的全部或部分步骤可以使用计算机程序流程来实现，所述计算机程序可以存储于一计算机可读存储介质中，所述计算机程序在相应的硬件平台上(如系统、设备、装置、器件等)执行，在执行时，包括方法实施例的步骤之一或其组合。
可选地，上述实施例的全部或部分步骤也可以使用集成电路来实现，这些步骤可以被分别制作成一个个集成电路模块，或者将它们中的多个模块或步骤制作成单个集成电路模块来实现。
上述实施例中的装置/功能模块/功能单元可以采用通用的计算装置来实现，它们可以集中在单个的计算装置上，也可以分布在多个计算装置所组成的网络上。
上述实施例中的装置/功能模块/功能单元以软件功能模块的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质 中。上述提到的计算机可读取存储介质可以是只读存储器，磁盘或光盘等。
工业实用性
本发明实施例方案利用梳妆分布等非连续分布的导频符号进行频偏测量，在测量过程中有效的利用相邻子载波上泄漏过来的频域数据进行频偏测量，很好地保证了导频符号非连续分布情况下的频偏估计性能；并且通过消除或者消减用户间的干扰，提升了目标用户的频偏测量精度。

Claims (17)

  1. 一种频偏估计方法，包括：
    对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值；
    利用所述目标用户所占子载波的频域数据、相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据；
    利用所述已消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值。
  2. 根据权利要求1所述的频偏估计方法，其中，所述对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值包括：
    在所述目标用户所占用的资源块中，利用所述目标用户的信道估计值，计算相邻的非目标用户所占资源的信道估计值，并利用所述目标用户的信道估计值和所述相邻的非目标用户所占资源的信道估计值，确定所述目标用户的重构信道估计值；
    在所述非目标用户所占用的资源块中，利用所述非目标用户的信道估计值，计算与所述非目标用户相邻的其他用户所占资源的信道估计值，并利用所述非目标用户的信道估计值和所述其他用户所占资源的信道估计值，确定所述非目标用户的重构信道估计值。
  3. 根据权利要求1所述的频偏估计方法，其中，所述计算已消除干扰的目标用户的本地导频的频域接收数据包括：
    当所述目标用户的信道与所述非目标用户的信道之间正交或弱相关时，将所述目标用户的频域数据与目标用户的重构信道估计值进行共轭相关运算，得到已消除干扰的目标用户的本地导频的频域接收数据。
  4. 根据权利要求3所述的频偏估计方法，所述计算已消除干扰的目标用户的本地导频的频域接收数据还包括：
    当所述目标用户和所述非目标用户为梳分用户且两者信道之间强相关 时，利用所述梳分用户的重构信道估计值，消除所述梳分用户在目标用户的相邻子载波上的干扰数据，得到已消除干扰的目标用户的本地导频的频域接收数据；或者，
    当所述目标用户与所述非目标用户为码分用户且两者信道之间强相关时，利用最小均方误差算法或迫零算法，对目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值进行处理，得到目标用户所占子载波的频域接收数据和目标用户在相邻非目标用户所占子载波上泄露的频域接收数据。
  5. 根据权利要求4所述的频偏估计方法，所述计算已消除干扰的目标用户的本地导频的频域接收数据还包括：
    利用所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值，计算正交化因子，并利用所述正交化因子，对所述非目标用户的信道进行正交化处理，使所述目标用户的信道与所述非目标用户的信道之间正交，消除所述非目标用户的频域数据在发送期间对目标用户的相邻子载波的干扰。
  6. 根据权利要求1所述的频偏估计方法，其中，所述利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值包括：
    对所述目标用户的本地导频进行重构，得到重构本地导频序列；
    对所述已消除干扰的目标用户的本地导频及频域接收数据和所述重构本地导频序列分别进行频时变换，得到本地导频的时域接收数据和时域数据序列；
    利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到所述频偏估计值。
  7. 根据权利要求6所述的频偏估计方法，所述利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包括：
    对所述目标用户的本地母码序列进行重构，得到重构本地母码序列；
    对所述重构本地母码序列进行频时变换和循环移位操作，得到本地导 频的时域数据序列。
  8. 根据权利要求6或7所述的频偏估计方法，所述利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到频偏估计值还包括：
    将所述本地导频的时域接收数据和时域数据序列进行共轭相关运算，得到时域的相位序列，并利用所述时域的相位序列，确定频偏估计值。
  9. 一种频偏估计装置，其特征在于，包括：
    重构模块，设置为对目标用户的信道估计值和非目标用户的信道估计值进行重构，得到所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值；
    干扰消除模块，设置为利用所述目标用户所占子载波的频域数据、相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值，计算已消除干扰的目标用户的本地导频的频域接收数据；
    频偏估计模块，设置为利用所述已消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值。
  10. 根据权利要求9所述的频偏估计装置，其中，所述重构模块包括：
    第一重构子模块，设置为在所述目标用户所占用的资源块中，利用所述目标用户的信道估计值，计算相邻的非目标用户所占资源的信道估计值，并利用所述目标用户的信道估计值和所述相邻的非目标用户所占资源的信道估计值，确定所述目标用户的重构信道估计值；
    第二重构子模块，设置为在所述非目标用户所占用的资源块中，利用所述非目标用户的信道估计值，计算与所述非目标用户相邻的其他用户所占资源的信道估计值，并利用所述非目标用户的信道估计值和所述其他用户所占资源的信道估计值，确定所述非目标用户的重构信道估计值。
  11. 根据权利要求9所述的频偏估计装置，其中，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据包括：当所述目标 用户的信道与所述非目标用户的信道之间正交或弱相关时，将所述目标用户的频域数据与目标用户的重构信道估计值进行共轭运算，得到已消除干扰的目标用户的本地导频的频域接收数据。
  12. 根据权利要求9所述的频偏估计装置，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据还包括：当所述目标用户和所述非目标用户为梳分用户且两者信道之间强相关时，利用所述梳分用户的重构信道估计值，消除所述梳分用户在目标用户的相邻子载波上的干扰数据，得到已消除干扰的目标用户的本地导频的频域接收数据，或者，当所述目标用户与所述非目标用户为码分用户且两者信道之间强相关时，利用最小均方误差算法或迫零算法，对目标用户所占子载波的频域数据及相邻的非目标用户所占子载波的频域数据、目标用户的重构信道估计值和非目标用户的重构信道估计值进行处理，得到目标用户所占子载波的频域接收数据和目标用户在相邻非目标用户所占子载波上泄露的频域接收数据。
  13. 根据权利要求12所述的频偏估计装置，所述干扰消除模块计算已消除干扰的目标用户的本地导频的频域接收数据还包括：利用所述目标用户的重构信道估计值和所述非目标用户的重构信道估计值，计算正交化因子，并利用所述正交化因子，对所述非目标用户的信道进行正交化处理，使所述目标用户的信道与所述非目标用户的信道之间正交，消除所述非目标用户的频域数据在发送期间对目标用户的相邻子载波的干扰。
  14. 根据权利要求9所述的频偏估计装置，其中，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值包括：对所述目标用户的本地导频进行重构，得到重构本地导频序列；对所述已消除干扰的目标用户的本地导频及频域接收数据和所述重构本地导频序列分别进行频时变换，得到本地导频的时域接收数据和时域数据序列；利用所得到的本地导频的时域接收数据和时域数据序列进行频偏测量，得到所述频偏估计值。
  15. 根据权利要求14所述的频偏估计装置，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包 括：对所述目标用户的本地母码序列进行重构，得到重构本地母码序列；对所述重构本地母码序列进行频时变换和循环移位操作，得到本地导频的时域数据序列。
  16. 根据权利要求14或15所述的频偏估计装置，所述频偏估计模块利用所述消除干扰的目标用户的本地导频及频域接收数据，确定频偏估计值还包括：将所述本地导频的时域接收数据和时域数据序列进行共轭相关运算，得到时域的相位序列，并利用所述时域的相位序列，确定频偏估计值。
  17. 一种计算机可读存储介质，存储有计算机可执行指令，所述计算机可执行指令被处理器执行时实现如权利要求1至8任意一项所述的频偏估计方法。
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