CN112152958B - Phase estimation method and device based on sparse scattered pilot frequency in OFDM system - Google Patents
Phase estimation method and device based on sparse scattered pilot frequency in OFDM system Download PDFInfo
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- H04L27/26—Systems using multi-frequency codes
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Abstract
The embodiment of the invention provides a phase estimation method and a phase estimation device based on sparse discrete pilot frequency in an OFDM system, belonging to the technical field of communication. The method comprises the following steps: pilot subcarriers on each OFDM symbol based on frequency domain insertion
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N; and performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved. The phase estimation method and the phase estimation device based on the sparse discrete pilot frequency in the OFDM system can achieve equal precision improvement on the front part and the rear part of the payload of the burst frame, and have good performance and wide applicability.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a phase estimation method and apparatus based on sparse scattered pilots in an OFDM system.
Background
For the burst OFDM system with sparse scattered pilots, the current prior art can use the average value of the phase estimated in the previous N times to improve the accuracy of the phase estimation, but the accuracy of the phase estimated in the previous N times is limited by the number of scattered pilots and the signal-to-noise ratio, and such estimation implicitly assumes that the phase change during N OFDM symbols is completely equal and is not suitable for the phase change caused by doppler spread due to motion.
The prior art may also use the demodulation and decoding result of the SIG field to inversely encode the modulated transmitted symbols as pilots to assist the existing scattered pilots to jointly improve the accuracy of phase estimation, but the SIG field usually appears only in the first small part of the payload of the burst frame, and there is no explicit scheme for phase estimation on the OFDM symbols in the last large part of the long payload data period.
In addition, in the prior art, data after demodulation data hard decision in a payload data period can be used for inverse modulation to be known symbols to be used as pilot frequency to carry out channel estimation and tracking, error propagation caused by hard decision misjudgment exists in the method, and the practicability cannot be guaranteed.
Disclosure of Invention
The phase estimation method and the phase estimation device based on the sparse discrete pilot frequency in the OFDM system can improve the equal precision at the front part and the rear part of the payload of a burst frame, and have better performance and wide applicability.
In order to achieve the above object, an embodiment of the present invention provides a phase estimation method based on sparse scattered pilots in an OFDM system, where the method includes: pilot subcarriers on each OFDM symbol based on frequency domain insertion
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N; and performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved.
Preferably, inN = M, andl=1,2, …, M time, pilot subcarriers on each OFDM symbol inserted based on frequency domain
Accumulating the P × N scattered pilots on the N adjacent OFDM symbols to improve the signal-to-noise ratio of the phase estimation, and obtaining statistics after improving the signal-to-noise ratio includes: obtaining statistics of improved signal-to-noise ratio by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
Preferably, at N =2MAnd is andlwhen the symbol is = -M ~ M, based on the pilot subcarrier on each OFDM symbol inserted in the frequency domain
Accumulating the P × N scattered pilots on the N adjacent OFDM symbols to improve the signal-to-noise ratio of the phase estimation, and obtaining statistics after improving the signal-to-noise ratio includes: obtaining statistics of improved signal-to-noise ratio by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
Preferably, at N = M, andlif =1,2, …, M, performing phase estimation based on the phase of the statistic of the improved snr includes: the phase estimation is performed by the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
Preferably, at N =2M, andlif = M-M, performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved includes: the phase estimation is performed by the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,anglefor taking phase operations。
Preferably, at N = M, andl=1,2, …, M, and when the position of the pilot subcarrier on the OFDM symbol is fixed or the pilot distribution on the front and back OFDM symbols is uniform, and the transmission pilot on the pilot subcarrier is a modulation symbol with normalized power, based on the pilot subcarrier inserted in the frequency domain on each OFDM symbol
Accumulating the P × N scattered pilots on the N adjacent OFDM symbols to improve the signal-to-noise ratio of the phase estimation, and obtaining statistics after improving the signal-to-noise ratio includes: obtaining statistics of improved signal-to-noise ratio by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
Preferably, at N =2M, andl= M-M, and when the position of the pilot subcarrier on the OFDM symbol is fixed or the pilot distribution on the front and back OFDM symbols is uniform, and the transmission pilot on the pilot subcarrier is a modulation symbol with normalized power, the pilot subcarrier on each OFDM symbol inserted based on the frequency domain
Accumulating the P × N scattered pilots on the N adjacent OFDM symbols to improve the signal-to-noise ratio of the phase estimation, and obtaining statistics after improving the signal-to-noise ratio includes: obtaining statistics of improved signal-to-noise ratio by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
Preferably, the method further comprises: completing OFDM symbol of initial channel response by the following formulal 0Phase tracking of the latter K OFDM symbols:
wherein K is more than or equal to 1 and less than or equal to M,
in order to be able to track the value of the phase,
is the phase estimate.
Preferably, the method further comprises: the number of OFDM symbols of the initial channel response of the next round of phase estimation and phase tracking is updated by the following formula:
wherein the content of the first and second substances,
the number of OFDM symbols of the initial channel response for the next round of phase estimation and phase tracking, floor is rounded down, L is the total number of OFDM symbols that need to be demodulated after LTF,ithe number of rounds of phase estimation and tracking is obtained; update the initial of the next round by the following formulaChannel frequency domain response phase:
wherein the content of the first and second substances,
for the next round of initial channel frequency domain response phase,ithe number of rounds of phase estimation and phase tracking.
The embodiment of the invention provides a phase estimation device based on sparse scattered pilot frequency in an OFDM system, which comprises: a statistic determination unit for pilot subcarriers on each OFDM symbol based on frequency domain insertion and a phase estimation unit
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N; the phase estimation unit is used for carrying out phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved.
By the technical scheme, the pilot frequency sub-carriers on each OFDM symbol are inserted based on the frequency domain
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N; and performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved. The invention can improve the estimation precision, and the same processing is used in both the front part and the rear part of the payload of the burst frame, so that the equal precision improvement can be obtained; nor error propagation degradation due to demodulation hard decisionsThe problem is that good performance can be obtained and the pilot scheme is applicable to both fixed and non-fixed pilot sets.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
fig. 1 is a flowchart of a sparse scattered pilot-based phase estimation method in an OFDM system according to an embodiment of the present invention;
fig. 2 is a block diagram illustrating a structure of a sparse scattered pilot-based phase estimation apparatus in an OFDM system according to an embodiment of the present invention.
Description of the reference numerals
1 statistic determination unit 2 phase estimation unit.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
In the burst OFDM system such as 802.11a and IEEE802.15.4g, a short and a long training sequence are arranged at the front part of a burst frame to complete synchronous acquisition, initial frequency offset estimation and channel estimation, and information such as SIG/PHR domain indicating the coding modulation of a physical layer and a PHYPpayload domain are arranged at the rear part of the burst frame.
The insertion of sparse scattered pilots in the frequency domain into the OFDM symbols of the SIG/PHR and PHYPayload domains is typically used for phase tracking. 802.11a inserts scattered pilots into four subcarriers of-21, -7, 7, and 21 (fixed pilot set, i.e. the position of the pilot set on each OFDM symbol is fixed) in 64 subcarriers of the frequency domain on each OFDM symbol; in the MR-OFDM system of ieee802.15.4g, 4 non-uniform (non-uniform spacing in the frequency domain) scattered pilots are inserted into 64 subcarriers in the frequency domain on each OFDM symbol in a 64-point FFT system, and the number set of the pilot subcarriers cyclically changes in a total number of 7 pilot sets (non-fixed pilot sets, i.e., the positions of the pilot sets on each OFDM symbol are changed).
Based on the frame design in the OFDM burst system, time and frequency synchronization is usually completed using the STF part of the synchronization header, and after time and frequency offset correction, the initial estimation of the channel frequency domain response can be completed because the LTF part at the tail of the synchronization header is a pilot frequency known in the full frequency domain.
The frequency domain subcarriers on each OFDM symbol of the SIG/PHR and Payload domains are composed of data subcarriers, pilot subcarriers, virtual subcarriers and direct current subcarriers, and no energy is transmitted on the virtual subcarriers and the direct current subcarriers. The signal model at the frequency domain receiving end of an OFDM system can be generally described as:
whereinlThe number is given for the OFDM symbols,kthe number is given to the sub-carriers,Y l （k）、H l （k) AndX l （k) Respectively a frequency domain symbol of a receiving end, a channel frequency domain response and a frequency domain symbol of a transmitting end,W l （k) White noise in the frequency domain. Considering that the doppler or residual carrier frequency offset is quasi-constant during several adjacent OFDM symbols, the signal model can be expressed as:
wherein
Is the sum of noise and inter-carrier interference caused by carrier frequency offset and channel doppler.
Fig. 1 is a flowchart of a sparse scattered pilot-based phase estimation method in an OFDM system according to an embodiment of the present invention. As shown in fig. 1, the method includes:
step S11, inserting pilot sub-carrier on each OFDM symbol based on frequency domain
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N;
for example, first, at N = M, andlwhen =1,2, …, M, the statistic of the signal-to-noise ratio improvement can be obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0the numbering of the OFDM symbols of the initial channel response is conjugate, it being understood that,
means an OFDM symboll+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The meaning of the above channel frequency domain response values is similar to that of other similar symbols, and is not described herein again.
I.e. using the channel response on the known initial frequency domain pilot subcarriers
And normalized pilot symbols
Multiplying the complex number after conjugation to the symbol on the pilot frequency sub-carrier of the received frequency domain to obtain the received symbol after phase compensation of the channel and the transmitted symbol, adding and summing the received symbols after phase compensation on all the pilot frequency sub-carriers in one OFDM symbol, and then responding the symbol with the initial channell 0After the continuationlThe sum of M OFDM symbols is summed again to obtain statistic with improved signal-to-noise ratio
。
When the position of the pilot frequency subcarrier on the OFDM symbol is fixed or the pilot frequency distribution on the front and rear OFDM symbols is uniform, and the transmission pilot frequency on the pilot frequency subcarrier is a modulation symbol with normalized power, the statistic after the signal-to-noise ratio is improved can be obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
In addition, secondly, the pilot OFDM symbol positions used in the reasonable phase estimation process of the present invention can be expanded to: in the initial channel response symbol
The first M OFDM symbols and the following M OFDM symbols, for a total of (2M) OFDM symbols, i.e. at N =2M, andlwhen the signal to noise ratio is not less than M, the statistic after the signal to noise ratio is improved can be obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
The statistics may also be calculated in a peer-to-peer fashion without changing the design essence:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
When the position of the pilot frequency subcarrier on the OFDM symbol is fixed or the pilot frequency distribution on the front and rear OFDM symbols is uniform, and the transmission pilot frequency on the pilot frequency subcarrier is a modulation symbol with normalized power, the statistic after the signal-to-noise ratio is improved can be obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
In this case, the above peer-to-peer form can be simplified as:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0numbering of OFDM symbols for initial channel responseIs a conjugate of the two or more of,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
Step S12, phase estimation is performed based on the phase of the statistic after the signal-to-noise ratio is improved.
For example, at N = M, andl=1,2, …, M, the phase estimation is performed by the following equation:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
At N =2M, andland when the signal is = M-M, performing phase estimation by the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
Accordingly, the phase estimation is performed based on the phase of the statistic obtained in the peer-to-peer manner after the snr is improved, which may be the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
Then, the embodiment of the present invention may also complete the OFDM symbol of the initial channel response by the following formulal 0Last K piecesPhase tracking of OFDM symbols:
wherein K is more than or equal to 1 and less than or equal to M,
in order to be able to track the value of the phase,
is the phase estimate.
This is achieved by
Can be used forl 0Coherent demodulation on data subcarriers over the next K OFDM symbols.
The number of OFDM symbols of the initial channel response for the next round of phase estimation and phase tracking is then updated by the following formula:
wherein the content of the first and second substances,
the number of OFDM symbols of the initial channel response for the next round of phase estimation and phase tracking, floor is rounded down, L is the total number of OFDM symbols that need to be demodulated after LTF,ithe number of rounds of phase estimation and tracking is obtained;
updating the initial channel frequency domain response phase of the next round by the following formula:
wherein the content of the first and second substances,
initial channel frequency domain response for next roundThe phase of the signal is determined,ithe number of rounds of phase estimation and phase tracking.
Hereinbefore, it is typical
Can be set as follows:
，
wherein floor is rounded down. In that
When the wheel is rotating, the value of M is
Wherein ceil is rounding up.
The invention combines the sparse pilot subcarriers on a plurality of OFDM symbols to carry out phase estimation, improves the signal-to-noise ratio of the statistic for phase estimation, thereby improving the precision of the phase estimation. In addition, in the phase tracking process, phase estimation can be performed once by a plurality of OFDM symbols, so that the calculation amount for obtaining the same precision is reduced. This application still has fine realization flexibility: the value of K in the phase tracking process can be flexibly selected within the range that K is more than or equal to 1 and less than or equal to M, and the compromise between the calculation complexity and the acquisition precision can be realized; this application also has fine adaptability: the method has good adaptability to the fixed or unfixed frequency domain position of the pilot frequency in the OFDM symbol.
Fig. 2 is a block diagram illustrating a structure of a sparse scattered pilot-based phase estimation apparatus in an OFDM system according to an embodiment of the present invention. As shown in fig. 2, the apparatus includes: a statistic determination unit 1 and a phase estimation unit 2, wherein the statistic determination unit 1 is used for pilot subcarriers on each OFDM symbol based on frequency domain insertion
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2,…, P, P is the number of sparse scattered pilots,lis a number of the OFDM symbol and,lthe number of (2) is N; the phase estimation unit 2 is configured to perform phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved.
The above-described embodiment of the phase estimation apparatus based on sparse scattered pilots in the OFDM system is similar to the above-described embodiment of the phase estimation method based on sparse scattered pilots in the OFDM system, and is not repeated here.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.
Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (9)
1. A method for phase estimation based on sparse scattered pilots in an OFDM system, the method comprising:
pilot subcarriers on each OFDM symbol based on frequency domain insertion
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lis N, at N = M, andlwhen =1,2, …, M, the statistic of the improved signal-to-noise ratio is obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0A channel frequency domain response value;
and performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved.
2. The sparse scattered pilot-based phase estimation method of claim 1, wherein N =2M, andland when the signal to noise ratio is not less than M, obtaining the statistic after the signal to noise ratio is improved by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
3. The sparse scattered pilot-based phase estimation method of claim 1, wherein N = M, andlif =1,2, …, M, performing phase estimation based on the phase of the statistic of the improved snr includes:
the phase estimation is performed by the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
4. The sparse scattered pilot-based phase estimation method of claim 2, wherein N =2M, andlif = M-M, performing phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved includes:
the phase estimation is performed by the following formula:
wherein the content of the first and second substances,
in order to be a phase estimation value,
for the statistics after the signal-to-noise ratio has improved,
the phase value for the statistic after the signal-to-noise ratio has been improved,angleis a phase-taking operation.
5. The sparse scattered pilot-based phase estimation method of claim 1, wherein N = M, andl=1,2, …, M, and when the position of the pilot subcarrier on the OFDM symbol is fixed or the pilot distribution on the front and back OFDM symbols is uniform, the transmission pilot on the pilot subcarrier is power normalizedWhen modulating the symbol, obtaining the statistic after improving the signal-to-noise ratio by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
6. The sparse scattered pilot-based phase estimation method of claim 1, wherein N =2M, andl= M-M, and when the position of the pilot subcarrier on the OFDM symbol is fixed or the pilot on the front and back OFDM symbolsThe distribution is uniform, when the transmitted pilot frequency on the pilot frequency subcarrier is a modulation symbol with normalized power, the statistic value after the signal-to-noise ratio is improved is obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0The channel frequency domain response value.
7. The method for sparse scattered pilot based phase estimation in an OFDM system according to claim 3 or 4, further comprising:
completing OFDM symbol of initial channel response by the following formulal 0Phase tracking of the latter K OFDM symbols:
wherein K is more than or equal to 1 and less than or equal to M,
in order to be able to track the value of the phase,
is the phase estimate.
8. The method for sparse scattered pilot based phase estimation in an OFDM system according to claim 7, further comprising:
the number of OFDM symbols of the initial channel response of the next round of phase estimation and phase tracking is updated by the following formula:
wherein the content of the first and second substances,
the number of OFDM symbols of the initial channel response for the next round of phase estimation and phase tracking, floor is rounded down, L is the total number of OFDM symbols that need to be demodulated after LTF,ithe number of rounds of phase estimation and tracking is obtained;
updating the initial channel frequency domain response phase of the next round by the following formula:
wherein the content of the first and second substances,
for the next round of initial channel frequency domain response phase,ithe number of rounds of phase estimation and phase tracking.
9. An apparatus for sparse scattered pilot based phase estimation in an OFDM system, the apparatus comprising:
a statistic determination unit and a phase estimation unit, wherein,
the statistic determination unit is used for inserting pilot subcarriers on each OFDM symbol based on frequency domain
Accumulating P multiplied by N scattered pilot frequencies on N adjacent OFDM symbols to improve the signal-to-noise ratio of phase estimation to obtain statistic after the signal-to-noise ratio is improved, whereinp=1,2, …, P, P being the number of sparse scattered pilots,lis a number of the OFDM symbol and,lis N, at N = M, andlwhen =1,2, …, M, the statistic of the improved signal-to-noise ratio is obtained by the following formula:
wherein the content of the first and second substances,
for the statistics after the signal-to-noise ratio has improved,l 0is the number of the OFDM symbol of the initial channel response, is the conjugate,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the receiving end of (1),
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll+l 0The frequency domain symbols of the transmitting end on,
for OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencyk，
For OFDM symbolsl+l 0TopNumber of sub-carrier of pilot frequencykOf the OFDM symboll 0A channel frequency domain response value;
the phase estimation unit is used for carrying out phase estimation based on the phase of the statistic after the signal-to-noise ratio is improved.
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| CN107395282A (en) * | 2017-07-20 | 2017-11-24 | 浙江工业大学 | A kind of big line width CO ofdm systems phase noise compensation method of time domain Unscented kalman filtering |
| CN110445738A (en) * | 2019-07-12 | 2019-11-12 | 四川安迪科技实业有限公司 | A kind of phase estimation method and device based on scattered pilot auxiliary |
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| CN107395282A (en) * | 2017-07-20 | 2017-11-24 | 浙江工业大学 | A kind of big line width CO ofdm systems phase noise compensation method of time domain Unscented kalman filtering |
| CN110445738A (en) * | 2019-07-12 | 2019-11-12 | 四川安迪科技实业有限公司 | A kind of phase estimation method and device based on scattered pilot auxiliary |
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