CN112511471B - Channel estimation method, device, equipment and medium based on space-frequency block code - Google Patents

Channel estimation method, device, equipment and medium based on space-frequency block code Download PDF

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CN112511471B
CN112511471B CN202110135229.6A CN202110135229A CN112511471B CN 112511471 B CN112511471 B CN 112511471B CN 202110135229 A CN202110135229 A CN 202110135229A CN 112511471 B CN112511471 B CN 112511471B
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channel estimation
subcarriers
subcarrier
antenna
symbol timing
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CN112511471A (en
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辜方林
曹阔
熊俊
范艺馨
侯茂斌
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National University of Defense Technology
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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
    • H04L25/0204—Channel estimation of multiple channels
    • 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
    • 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
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    • H04L27/2657—Carrier synchronisation

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Abstract

The invention discloses a channel estimation method based on space-frequency block codes, which comprises the following steps: determining an initial channel estimation value by using receiving signals and transmitting signals of two adjacent subcarriers; determining a target symbol timing deviation through the receiving signals and the sending signals of each group of subcarriers; and carrying out phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value. Therefore, when the channel estimation is carried out based on the space-frequency block code, the target symbol timing deviation needs to be calculated, and the initial channel estimation value is subjected to phase correction through the target symbol timing deviation, so that the problem of decoding failure caused by symbol timing deviation introduced by symbol timing can be avoided, and the reliability of decoding is ensured; the invention also discloses a channel estimation device, equipment and a medium based on the space frequency block code, and the technical effects can be realized.

Description

Channel estimation method, device, equipment and medium based on space-frequency block code
Technical Field
The present invention relates to the field of mobile communication system technology, and more particularly, to a channel estimation method, apparatus, device and medium based on space-frequency block codes.
Background
The MIMO (multiple-input multiple-output) -OFDM (orthogonal frequency division multiplexing) system is a multiple-input multiple-output system MIMO formed by simultaneously arranging a plurality of antennas at a receiving end and a transmitting end of OFDM of an orthogonal frequency division multiplexing system, and due to the combination of the characteristics of high diversity gain and large system capacity of the MIMO system, frequency selective fading resistance and high frequency spectrum utilization rate of the OFDM system, the MIMO system receives more and more attention under the drive of the requirements of new-generation mobile communication on high capacity and low cost.
In the MIMO technology, from the perspective of improving spatial diversity, space-time block coding (STBC) requires only linear complexity for maximum likelihood decoding due to its orthogonality design, and thus the research is the most widely. Space-frequency block coding (SFBC) is formed by combining space-time block codes with OFDM. In this case, the requirement of the space-time block code for the channel time domain characteristic also becomes a requirement for the channel frequency domain characteristic. Such as: the corresponding space-frequency code of the Alamouti space-time code requires that the frequency domain channel in which the same code block is located is slowly varying.
Referring to fig. 1, which is a schematic diagram of a conventional SFBC-based MIMO-OFDM system framework in the prior art, as can be seen from fig. 1, fig. 1 shows a data receiving and transmitting process of a MIMO-OFDM system, including: and the information bits of the transmitting terminal are modulated by a complex constellation to obtain information symbols, the information symbols are encoded by SFBC, then are shunted and subjected to OFDM modulation, and then are sent to each transmitting antenna. The receiving end firstly carries out OFDM demodulation on signals received by each antenna, then carries out channel estimation by using demodulated frequency domain data, sends the obtained frequency domain channel information and frequency domain receiving data to an SFBC decoder for decoding, and obtains information bits after demodulation and recovery. Time-frequency synchronization and channel estimation in an OFDM system both belong to key technologies. Note that the OFDM system (in particular, CP (cyclic-prefix) -OFDM) has a relatively low accuracy for symbol timing synchronization due to the guard interval effect exerted by the CP. In principle, the error of symbol timing synchronization only needs to be smaller than 1/2CP length, and at this time, the effect of symbol timing can be eliminated by only reasonably utilizing CP guard interval.
However, if the Alamouti space-time code scheme is combined with the OFDM system to form a MIMO-OFDM system, the timing offset introduced by the symbol timing will cause an additional linear phase shift to the frequency domain equivalent channel of the received data, so that the requirement of the Alamouti code for slow channel change in the same coding block cannot be met, and the decoding fails.
Therefore, how to avoid decoding failure caused by timing deviation introduced by symbol timing is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a channel estimation method, a device, equipment and a medium based on space-frequency block codes, so as to avoid decoding failure caused by timing deviation introduced by symbol timing.
In order to achieve the above object, the present invention provides a channel estimation method based on space-frequency block codes, which includes:
determining an initial channel estimation value by using receiving signals and transmitting signals of two adjacent subcarriers;
determining a target symbol timing deviation through the receiving signals and the sending signals of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
and carrying out phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value.
Wherein, the determining the initial channel estimation value by using the received signals and the transmitted signals of two adjacent subcarriers comprises:
determining each group of subcarriers, wherein each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, the serial numbers of the subcarriers of which are sequentially increased;
taking a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers;
determining a first channel estimation function according to receiving signals acquired by a first receiving antenna and a second receiving antenna on a first subcarrier and a second subcarrier and sending signals sent by a first sending antenna and a second sending antenna on the first subcarrier and the second subcarrier;
and determining an initial channel estimation value according to the first channel estimation function.
Wherein the initial channel estimation value comprises:
a first initial channel estimation value between the first transmitting antenna and the first receiving antenna, a second initial channel estimation value between the second transmitting antenna and the first receiving antenna, a third initial channel estimation value between the first transmitting antenna and the second receiving antenna, and a fourth initial channel estimation value between the second transmitting antenna and the second receiving antenna.
Wherein, the determining the target symbol timing offset through the received signal and the transmitted signal of each group of subcarriers includes:
determining a second channel estimation function according to the received signals acquired by the first receiving antenna and the second receiving antenna on the third subcarrier and the fourth subcarrier and the sending signals sent by the first transmitting antenna and the second transmitting antenna on the third subcarrier and the fourth subcarrier;
calculating initial symbol timing deviation corresponding to each group of subcarriers according to the first channel estimation function and the second channel estimation function of each group of subcarriers;
and determining the target symbol timing deviation by using the initial symbol timing deviation corresponding to each group of subcarriers.
Wherein the determining the symbol timing offset by using the initial symbol timing offset corresponding to each group of subcarriers comprises: and calculating the average value of the initial symbol timing deviation of each group of subcarriers, and taking the average value as the target symbol timing deviation.
Wherein, the phase correcting the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value includes:
using the target symbol timing offset
Figure 500149DEST_PATH_IMAGE001
An estimated value determining rule, which is used for carrying out phase correction on the initial channel estimated value to obtain a final target channel estimated value;
wherein the evaluation value determination rule is:
Figure 525612DEST_PATH_IMAGE002
Figure 852819DEST_PATH_IMAGE003
wherein,
Figure 636578DEST_PATH_IMAGE004
is the first between the first transmitting antenna and the first receiving antennaA target channel estimation value is obtained by estimating a channel estimation value,
Figure 60737DEST_PATH_IMAGE005
e is a natural constant, N is the total number of subcarriers, k is the serial number of the subcarriers,
Figure 850576DEST_PATH_IMAGE006
for a first initial channel estimate between the first transmit antenna and the first receive antenna,
Figure 727397DEST_PATH_IMAGE007
for a second initial channel estimate between the second transmit antenna and the first receive antenna,
Figure 303128DEST_PATH_IMAGE008
for a third target channel estimate between the first transmit antenna and the second receive antenna,
Figure 378531DEST_PATH_IMAGE009
for a first target channel estimate between the second transmit antenna and the second receive antenna,
Figure 152321DEST_PATH_IMAGE010
for a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure 313175DEST_PATH_IMAGE011
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
In order to achieve the above object, the present invention further provides a channel estimation device based on space frequency block code, including:
a first estimated value determining module, configured to determine an initial channel estimated value by using received signals and transmitted signals of two adjacent subcarriers;
a symbol timing deviation determining module, configured to determine a target symbol timing deviation according to the received signal and the transmitted signal of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
and the second estimation value determining module is used for carrying out phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value.
Wherein the first estimated value determining module comprises:
the first determining unit is used for determining each group of subcarriers, and each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, wherein the subcarrier numbers of the subcarriers are sequentially increased;
an adjacent subcarrier determining unit, configured to use a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers;
a second determining unit, configured to determine a first channel estimation function according to received signals obtained by the first receiving antenna and the second receiving antenna at the first subcarrier and the second subcarrier and transmission signals sent by the first transmitting antenna and the second transmitting antenna at the first subcarrier and the second subcarrier;
a third determining unit, configured to determine an initial channel estimation value according to the first channel estimation function.
To achieve the above object, the present invention further provides an electronic device comprising:
a memory for storing a computer program;
a processor for implementing the steps of the space frequency block code based channel estimation method as described above when executing the computer program.
To achieve the above object, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when being executed by a processor, implements the steps of the channel estimation method based on space frequency block codes as described above.
As can be seen from the above solutions, a channel estimation method based on space-frequency block codes provided in the embodiments of the present invention includes: determining an initial channel estimation value by using receiving signals and transmitting signals of two adjacent subcarriers; determining a target symbol timing deviation through the receiving signals and the sending signals of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers; and carrying out phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value.
Therefore, when the channel estimation is carried out based on the space-frequency block code, the target symbol timing deviation needs to be calculated, and the initial channel estimation value is subjected to phase correction through the target symbol timing deviation, so that the problem of decoding failure caused by symbol timing deviation introduced by symbol timing can be avoided, and the reliability of decoding is ensured; the invention also discloses a channel estimation device, equipment and a medium based on the space frequency block code, and the technical effects can be realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a SFBC-based MIMO-OFDM classical system framework in the prior art;
fig. 2 is a schematic flow chart of a channel estimation method based on space-frequency block codes according to an embodiment of the present invention;
FIG. 3a is a diagram illustrating the channel estimation value when STO is 0 according to an embodiment of the present invention;
FIG. 3b is a diagram of another channel estimation value with STO of 0 according to the embodiment of the present invention;
FIG. 3c is a diagram of another channel estimate with STO of 0 according to the disclosure of the present invention;
FIG. 3d is a diagram illustrating another channel estimation value when STO is 0 according to an embodiment of the present invention;
FIG. 4a is a diagram illustrating the channel estimation with STO of 32 according to an embodiment of the present invention;
FIG. 4b is a diagram illustrating another channel estimate with STO of 32 according to an embodiment of the present invention;
FIG. 4c is a diagram of another channel estimate with STO of 32 according to the disclosure of the present invention;
FIG. 4d is a diagram illustrating another channel estimate with STO of 32 according to an embodiment of the present invention;
FIG. 5a is a schematic diagram of the signal estimation value when STO is 0 according to the embodiment of the present invention;
FIG. 5b is a diagram illustrating the signal estimation when STO is 32 according to the embodiment of the present invention;
FIG. 6a is a schematic diagram of the STO compensated channel estimation values disclosed in the embodiments of the present invention;
FIG. 6b is a diagram illustrating another channel estimation value after STO compensation according to an embodiment of the present invention;
FIG. 6c is a diagram illustrating another channel estimation value after STO compensation according to an embodiment of the present invention;
FIG. 6d is a diagram illustrating another channel estimation value after STO compensation according to an embodiment of the present invention;
FIG. 7 is a block diagram of a channel estimation implementation based on phase correction according to an embodiment of the present disclosure;
fig. 8 is a schematic structural diagram of a channel estimation device based on space-frequency block codes according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the disclosure.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a channel estimation method, a device, equipment and a medium based on space-frequency block codes, which are used for avoiding decoding failure caused by timing deviation introduced by symbol timing.
Referring to fig. 2, a schematic flow chart of a channel estimation method based on space-frequency block codes according to an embodiment of the present invention includes:
s101, determining an initial channel estimation value by using receiving signals and sending signals of two adjacent subcarriers;
the process of determining the initial channel estimation value by using the received signals and the transmitted signals of the two adjacent subcarriers specifically comprises the following steps:
determining each group of subcarriers, wherein each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, the serial numbers of the subcarriers of which are sequentially increased; taking a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers; determining a first channel estimation function according to receiving signals acquired by a first receiving antenna and a second receiving antenna on a first subcarrier and a second subcarrier and sending signals sent by a first sending antenna and a second sending antenna on the first subcarrier and the second subcarrier; and determining an initial channel estimation value according to the first channel estimation function.
It should be noted that, in the present scheme, when performing channel estimation, all subcarriers need to be grouped first, for example: if the total number of subcarriers is 64 and the number of subcarriers in each group is set to 4, then 64 subcarriers may be divided into 16 groups of subcarriers, in this scheme, the 4 subcarriers are named according to the subcarrier sequence number of each group of subcarriers, that is, each group of subcarriers includes: the carrier comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier. In addition, when the initial channel estimation value is determined, the initial channel estimation value is determined by two adjacent subcarriers, namely the first subcarrier and the second subcarrier.
Specifically, for convenience of analysis, the present embodiment is described by taking single-input single-output (SISO) OFDM as an example, and assuming that Symbol Timing Offset (STO) is d, the frequency domain expression of the received signal is:
Figure 581345DEST_PATH_IMAGE012
（1）
wherein,
Figure 12720DEST_PATH_IMAGE013
is as follows
Figure 458876DEST_PATH_IMAGE014
The received signal on the sub-carrier(s),
Figure 605561DEST_PATH_IMAGE015
is shown as
Figure 756051DEST_PATH_IMAGE014
The channel frequency domain response at the sub-carriers,
Figure 196260DEST_PATH_IMAGE016
is as follows
Figure 439416DEST_PATH_IMAGE014
The transmitted signal on a number of sub-carriers,
Figure 43703DEST_PATH_IMAGE017
indicating the number of subcarriers.
On this basis, consider the case where SFBC is employed in a 2 × 2 MIMO-OFDM system. And applying the Alamouti space-time code to a frequency domain to obtain the SFBC coding scheme. The same SFBC coding block occupies two adjacent frequency points in the frequency domain OFDM symbol blocks of two transmitting antennas, and the transmitting antenna 1 sequentially bears information symbols on the two frequency points
Figure 637365DEST_PATH_IMAGE018
And
Figure 807446DEST_PATH_IMAGE019
(ii) a The transmitting antenna 2 carries information symbols on the two frequency points in turn
Figure 944205DEST_PATH_IMAGE020
And
Figure 426002DEST_PATH_IMAGE021
。
the system frequency domain model of the receiving antenna 1 is represented by equation (2):
Figure 823354DEST_PATH_IMAGE022
（2）
wherein,
Figure 723308DEST_PATH_IMAGE023
representing the first signal in the packet received by receive antenna 1 on the 1 st subcarrier,
Figure 668786DEST_PATH_IMAGE024
it indicates that the second signal in the packet was received by receive antenna 1 on the 2 nd subcarrier.
Figure 483552DEST_PATH_IMAGE025
For transmitting the first signal transmitted by the antenna 1 at the first moment,
Figure 45114DEST_PATH_IMAGE026
for transmitting the first signal transmitted by the antenna 2 at the first moment,
Figure 48842DEST_PATH_IMAGE027
for transmitting the second signal transmitted by the antenna 1 at the second moment,
Figure 67352DEST_PATH_IMAGE028
for transmitting the second signal transmitted by the antenna 2 at the second moment,
Figure 274473DEST_PATH_IMAGE029
for transmitting in the 1 st sub-carrierInitial channel estimates between transmit antenna 1 and receive antenna 1,
Figure 418489DEST_PATH_IMAGE030
for the initial channel estimate between transmit antenna 2 and receive antenna 1 in the 1 st subcarrier,
Figure 11145DEST_PATH_IMAGE031
for an initial channel estimation value between the transmit antenna 1 and the receive antenna 1 in the 2 nd subcarrier,
Figure 702020DEST_PATH_IMAGE032
is an initial channel estimation value between the transmitting antenna 2 and the receiving antenna 1 in the 2 nd sub-carrier.
Figure 894973DEST_PATH_IMAGE033
For the noise of the data received in the first subcarrier by the receive antenna 1,
Figure 250868DEST_PATH_IMAGE034
the noise of the data is received in the second subcarrier for the receiving antenna 1.
Correspondingly, the system frequency domain model of the receiving antenna 2 is represented by (3):
Figure 838975DEST_PATH_IMAGE035
（3）
wherein,
Figure 812004DEST_PATH_IMAGE036
representing the first signal in the packet received by the receive antenna 2 on the 1 st subcarrier,
Figure 118352DEST_PATH_IMAGE024
indicating the second signal in the packet received by receive antenna 2 on the 2 nd subcarrier.
Figure 215621DEST_PATH_IMAGE037
For receiving antenna 2 connected in the first sub-carrierThe noise of the received data is reduced,
Figure 422349DEST_PATH_IMAGE038
the noise of the data is received in the second subcarrier for the receiving antenna 1.
In the present embodiment, assuming that the channel frequency domain responses of two adjacent subcarriers are equal (approximately equal), equation (2) may be converted into equation (4), and equation (3) may be converted into equation (5):
Figure 64814DEST_PATH_IMAGE039
（4）
Figure 359922DEST_PATH_IMAGE040
（5）
the initial channel estimate values that can be determined from equations (4) and (5) above are:
Figure 995303DEST_PATH_IMAGE041
（6）
Figure 292423DEST_PATH_IMAGE042
（7）
the initial channel estimation value can be determined by the formula (6) and the formula (7)
Figure 869904DEST_PATH_IMAGE006
、
Figure 885264DEST_PATH_IMAGE007
、
Figure 589915DEST_PATH_IMAGE010
、
Figure 508586DEST_PATH_IMAGE011
Wherein
Figure 758433DEST_PATH_IMAGE006
is a first initial channel estimate between a first transmit antenna and a first receive antenna,
Figure 759625DEST_PATH_IMAGE007
for a second initial channel estimate between a second transmit antenna and the first receive antenna,
Figure 2387DEST_PATH_IMAGE010
is a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure 274100DEST_PATH_IMAGE011
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
Due to the above
Figure 184594DEST_PATH_IMAGE006
、
Figure 174547DEST_PATH_IMAGE007
、
Figure 955421DEST_PATH_IMAGE010
、
Figure 517858DEST_PATH_IMAGE011
Has an influence of timing deviation, and therefore, the estimation of the channel cannot be realized by using the above equations (6) and (7), and STO causes uncertainty of the channel estimation. Referring to fig. 3a, fig. 3b, fig. 3c, fig. 3d, fig. 4a, fig. 4b, fig. 4c, and fig. 4d, which are schematic diagrams illustrating an influence of an STO on channel estimation when SFBC is adopted in a MIMO-OFDM system according to an embodiment of the present invention, wherein fig. 3a, fig. 3b, fig. 3c, and fig. 3d are schematic diagrams illustrating different channel estimation values when symbol timing offset is 0 according to an embodiment of the present invention, and fig. 4a, fig. 4b, fig. 4c, and fig. 4d are schematic diagrams illustrating different channel estimation values when symbol timing offset is 32 according to an embodiment of the present invention, and accordingly, the influence of the STO on channel estimation is reflected to subsequent SFBC diversity, and formula (6) and fig. 4d are utilized(7) The obtained channel estimation value, the SFBC diversity processing, and the LS estimation, can obtain a signal estimation value as follows:
Figure 234141DEST_PATH_IMAGE043
（8）
referring to fig. 5a and 5b, the effect of STO on the signal estimation value obtained by SFBC diversity reception in the MIMO-OFDM system disclosed in this embodiment is shown, where fig. 5a is the 2 × 2MIMO signal estimation value when the symbol timing offset is 0, and fig. 5b is the 2 × 2MIMO signal estimation value when the symbol timing offset is 32; therefore, in the scheme, when the MIMO-OFDM system adopts space-frequency coding, the influence of the symbol timing deviation needs to be overcome to realize accurate estimation of the channel, and correct diversity reception of the final signal can be realized.
S102, determining a target symbol timing deviation through the receiving signals and the sending signals of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
the process of determining the timing deviation of the target symbol through the receiving signal and the sending signal of each group of subcarriers specifically comprises the following steps: determining a second channel estimation function according to the received signals acquired by the first receiving antenna and the second receiving antenna on the third subcarrier and the fourth subcarrier and the sending signals sent by the first transmitting antenna and the second transmitting antenna on the third subcarrier and the fourth subcarrier; calculating initial symbol timing deviation corresponding to each group of subcarriers according to the first channel estimation function and the second channel estimation function of each group of subcarriers; and determining the target symbol timing deviation by using the initial symbol timing deviation corresponding to each group of subcarriers.
In this embodiment, in order to overcome the influence of the symbol timing offset on the channel estimation value, it is reasonable to assume that the channel frequency domain responses of the adjacent four subcarriers are equal (approximately equal), and a first channel estimation function for calculating channel estimation functions corresponding to the first subcarrier and the second subcarrier can be determined by the above formula (4) and formula (5), and this time, a second channel estimation function for calculating channel estimation functions corresponding to the third subcarrier and the fourth subcarrier is determined as:
Figure 836024DEST_PATH_IMAGE044
（9）
Figure 610470DEST_PATH_IMAGE045
（10）
wherein,
Figure 981408DEST_PATH_IMAGE046
representing the third signal in the packet received by receive antenna 1 on the 3 rd subcarrier,
Figure 367128DEST_PATH_IMAGE047
it means that the fourth signal in the packet is received by the receive antenna 1 on the 4 th subcarrier,
Figure 941460DEST_PATH_IMAGE048
for transmitting the third signal transmitted by antenna 1 at the third moment,
Figure 706547DEST_PATH_IMAGE049
for transmitting the third signal transmitted by the antenna 2 at the third moment,
Figure 931992DEST_PATH_IMAGE050
a fourth signal transmitted by the transmit antenna 1 at a fourth time,
Figure 990078DEST_PATH_IMAGE051
a fourth signal transmitted by the transmit antenna 2 at a fourth time,
Figure 815820DEST_PATH_IMAGE052
for the noise of the data received in the third subcarrier by the receive antenna 1,
Figure 617554DEST_PATH_IMAGE053
the noise of the data is received in the fourth subcarrier for the receive antenna 1.
Figure 697505DEST_PATH_IMAGE054
For the noise of the data received in the third subcarrier by the receive antenna 2,
Figure 693537DEST_PATH_IMAGE055
the noise of the data is received in the fourth subcarrier for the receive antenna 2.
In the present embodiment, the influence of noise is ignored for the convenience of analysis. Using the properties of the diagonal matrix, processing equation (4) in the first channel estimation function and equation (9) in the second channel estimation function may further result in equation (11) and equation (12):
Figure 242461DEST_PATH_IMAGE056
（11）
Figure 549683DEST_PATH_IMAGE057
（12）
wherein,
Figure 625086DEST_PATH_IMAGE058
representing a conjugate transpose. Equation (13) can be obtained by performing conjugate point multiplication on equation (11) and equation (12) and using the assumption that the channel frequency domain responses of the adjacent four subcarriers are equal (approximately equal):
Figure 288342DEST_PATH_IMAGE059
(13)
the initial symbol timing offset corresponding to the group of subcarriers can be calculated by formula (13), and similarly, formula (4) and formula (10) can obtain formula (14) by the above process:
Figure 714775DEST_PATH_IMAGE060
(14)
after the initial symbol timing offset corresponding to each group of subcarriers is obtained by calculating another initial symbol timing offset corresponding to the group of subcarriers according to the formula (14), the average value of the initial symbol timing offsets of each group of subcarriers can be calculated and used as the final target symbol timing offset
Figure 982945DEST_PATH_IMAGE001
Thereby improving the accuracy of the STO estimation.
S103, phase correction is carried out on the initial channel estimation value by utilizing the target symbol timing deviation, and a final target channel estimation value is obtained.
The method for performing phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain the final target channel estimation value comprises the following steps:
using target symbol timing offset
Figure 614653DEST_PATH_IMAGE001
An estimated value determining rule, which is used for carrying out phase correction on the initial channel estimated value to obtain a final target channel estimated value; the estimation value determination rule is:
Figure 123125DEST_PATH_IMAGE002
Figure 7161DEST_PATH_IMAGE003
wherein,
Figure 157651DEST_PATH_IMAGE004
estimating a first target channel estimation value between the first transmitting antenna and the first receiving antenna, and estimating a second target channel estimation value between the second transmitting antenna and the first receiving antennaThe value, e is a natural constant, N is the total number of subcarriers, k is the number of subcarriers,
Figure 332280DEST_PATH_IMAGE006
for a first initial channel estimate between the first transmit antenna and the first receive antenna,
Figure 244610DEST_PATH_IMAGE007
for a second initial channel estimate between the second transmit antenna and the first receive antenna,
Figure 380057DEST_PATH_IMAGE008
for a third target channel estimate between the first transmit antenna and the second receive antenna,
Figure 990030DEST_PATH_IMAGE009
for a first target channel estimate between the second transmit antenna and the second receive antenna,
Figure 395997DEST_PATH_IMAGE010
for a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure 511851DEST_PATH_IMAGE011
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
In the present embodiment, if the formula (4) is extended to the general case:
Figure 508495DEST_PATH_IMAGE061
（15）
the exact target channel estimation value obtained by combining equation (15) is:
Figure 797525DEST_PATH_IMAGE062
（16）
Figure 681167DEST_PATH_IMAGE063
（17）
referring to fig. 6a, fig. 6b, fig. 6c, and fig. 6d, which are schematic diagrams illustrating channel estimation effects under the condition of using SFBC in the MIMO-OFDM system after STO compensation disclosed in this embodiment, wherein fig. 6a, fig. 6b, fig. 6c, and fig. 6d respectively show different channel estimation values when symbol timing deviation is 32, and it can be seen that accurate channel estimation values can be completely obtained through phase correction.
In summary, the present disclosure provides a channel estimation method with "phase correction" suitable for MIMO-OFDM under SFBC condition, where the method performs "phase correction" on frequency domain channel response data at a receiving end, so that the corrected equivalent frequency domain channel satisfies the requirement of the Alamouti scheme again, thereby ensuring the reliability of decoding. Referring to fig. 7, in this scheme, frequency domain data received based on two antennas is a received signal, pilot frequency data is a transmitted signal, and channel estimation is implemented through the received signal, the transmitted information, and the above formula (6) and formula (7), so as to obtain an initial channel estimation value:
Figure 531705DEST_PATH_IMAGE006
、
Figure 251530DEST_PATH_IMAGE007
、
Figure 577207DEST_PATH_IMAGE010
、
Figure 580935DEST_PATH_IMAGE011
on the basis, combining the formula (13) and the formula (14) to realize accurate estimation of STO in the frequency domain, and finally realizing phase correction by using the formula (16) and the formula (17) to obtain a final target channel estimation value
Figure 835330DEST_PATH_IMAGE004
、
Figure 532198DEST_PATH_IMAGE005
、
Figure 163031DEST_PATH_IMAGE008
、
Figure 129587DEST_PATH_IMAGE009
。
The following describes a channel estimation device, a device, and a medium according to embodiments of the present invention, and the channel estimation device described below and the channel estimation device, the device, and the medium described above may be referred to each other.
Referring to fig. 8, a schematic structural diagram of a channel estimation device based on space-frequency block codes according to an embodiment of the present invention includes:
a first estimation value determining module 100, configured to determine an initial channel estimation value by using received signals and transmitted signals of two adjacent subcarriers;
a symbol timing deviation determining module 200, configured to determine a target symbol timing deviation according to the received signal and the transmitted signal of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
a second estimation value determining module 300, configured to perform phase correction on the initial channel estimation value by using the target symbol timing offset, so as to obtain a final target channel estimation value.
Wherein the first estimated value determining module comprises:
the first determining unit is used for determining each group of subcarriers, and each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, wherein the subcarrier numbers of the subcarriers are sequentially increased;
an adjacent subcarrier determining unit, configured to use a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers;
a second determining unit, configured to determine a first channel estimation function according to received signals obtained by the first receiving antenna and the second receiving antenna at the first subcarrier and the second subcarrier and transmission signals sent by the first transmitting antenna and the second transmitting antenna at the first subcarrier and the second subcarrier;
a third determining unit, configured to determine an initial channel estimation value according to the first channel estimation function.
Wherein the initial channel estimation value comprises:
a first initial channel estimation value between the first transmitting antenna and the first receiving antenna, a second initial channel estimation value between the second transmitting antenna and the first receiving antenna, a third initial channel estimation value between the first transmitting antenna and the second receiving antenna, and a fourth initial channel estimation value between the second transmitting antenna and the second receiving antenna.
Wherein the symbol timing offset determination module comprises:
a fourth determining unit, configured to determine a second channel estimation function according to received signals obtained by the first receiving antenna and the second receiving antenna at the third subcarrier and the fourth subcarrier and transmission signals sent by the first transmitting antenna and the second transmitting antenna at the third subcarrier and the fourth subcarrier;
a calculating unit, configured to calculate an initial symbol timing offset corresponding to each group of subcarriers according to the first channel estimation function and the second channel estimation function of each group of subcarriers;
a fifth determining unit, configured to determine the target symbol timing offset by using the initial symbol timing offset corresponding to each group of subcarriers.
Wherein the fifth determining unit is specifically configured to: and calculating the average value of the initial symbol timing deviation of each group of subcarriers, and taking the average value as the target symbol timing deviation.
Wherein the second estimated value determining module is specifically configured to: using the target symbol timing offset
Figure 945097DEST_PATH_IMAGE001
And estimation value determination ruleCarrying out phase correction on the initial channel estimation value to obtain a final target channel estimation value; wherein the evaluation value determination rule is:
Figure 764148DEST_PATH_IMAGE002
Figure 309923DEST_PATH_IMAGE003
wherein,
Figure 898031DEST_PATH_IMAGE004
for a first target channel estimate between the first transmit antenna and the first receive antenna,
Figure 884441DEST_PATH_IMAGE005
e is a natural constant, N is the total number of subcarriers, k is the serial number of the subcarriers,
Figure 892586DEST_PATH_IMAGE006
for a first initial channel estimate between the first transmit antenna and the first receive antenna,
Figure 865222DEST_PATH_IMAGE007
for a second initial channel estimate between the second transmit antenna and the first receive antenna,
Figure 684666DEST_PATH_IMAGE008
for a third target channel estimate between the first transmit antenna and the second receive antenna,
Figure 717344DEST_PATH_IMAGE009
for a first target channel estimate between the second transmit antenna and the second receive antenna,
Figure 635622DEST_PATH_IMAGE010
for a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure 644904DEST_PATH_IMAGE011
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
Referring to fig. 9, an embodiment of the present invention further discloses a structural schematic diagram of an electronic device, including:
a memory 11 for storing a computer program;
a processor 12, configured to implement the steps of the space frequency block code based channel estimation method according to any of the above method embodiments when executing the computer program.
In this embodiment, the device may be a PC (Personal Computer), or may be a terminal device such as a smart phone, a tablet Computer, a palmtop Computer, or a portable Computer.
The device may include a memory 11, a processor 12, and a bus 13.
The memory 11 includes at least one type of readable storage medium, which includes a flash memory, a hard disk, a multimedia card, a card type memory (e.g., SD or DX memory, etc.), a magnetic memory, a magnetic disk, an optical disk, and the like. The memory 11 may in some embodiments be an internal storage unit of the device, for example a hard disk of the device. The memory 11 may also be an external storage device of the device in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), etc. provided on the device. Further, the memory 11 may also include both an internal storage unit of the device and an external storage device. The memory 11 may be used not only to store application software installed in the device and various types of data such as program codes for performing a channel estimation method, etc., but also to temporarily store data that has been output or is to be output.
Processor 12, which in some embodiments may be a Central Processing Unit (CPU), controller, microcontroller, microprocessor or other data Processing chip, executes program code stored in memory 11 or processes data, such as program code for performing a channel estimation method.
The bus 13 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 9, but this does not indicate only one bus or one type of bus.
Further, the device may further include a network interface 14, and the network interface 14 may optionally include a wired interface and/or a wireless interface (e.g., WI-FI interface, bluetooth interface, etc.), which are generally used to establish a communication connection between the device and other electronic devices.
Optionally, the device may further comprise a user interface 15, the user interface 15 may comprise a Display (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 15 may further comprise a standard wired interface, a wireless interface. Alternatively, in some embodiments, the display may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, an OLED (Organic Light-Emitting Diode) touch device, or the like. The display, which may also be referred to as a display screen or display unit, is suitable for displaying information processed in the device and for displaying a visualized user interface.
Fig. 9 shows only the device with the components 11-15, and it will be understood by those skilled in the art that the structure shown in fig. 9 does not constitute a limitation of the device, and may comprise fewer or more components than those shown, or some components may be combined, or a different arrangement of components.
The embodiment of the invention also discloses a computer readable storage medium, wherein a computer program is stored on the computer readable storage medium, and when the computer program is executed by a processor, the steps of the channel estimation method based on the space frequency block code are realized.
Wherein the storage medium may include: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (5)

1. A channel estimation method based on space-frequency block code is characterized by comprising the following steps:
determining an initial channel estimation value by using receiving signals and transmitting signals of two adjacent subcarriers;
determining a target symbol timing deviation through the receiving signals and the sending signals of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
carrying out phase correction on the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value;
wherein, the determining the initial channel estimation value by using the received signals and the transmitted signals of two adjacent subcarriers comprises:
determining each group of subcarriers, wherein each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, the serial numbers of the subcarriers of which are sequentially increased;
taking a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers;
determining a first channel estimation function according to receiving signals acquired by a first receiving antenna and a second receiving antenna on a first subcarrier and a second subcarrier and sending signals sent by a first sending antenna and a second sending antenna on the first subcarrier and the second subcarrier;
determining an initial channel estimation value according to the first channel estimation function;
wherein, the determining the target symbol timing offset through the received signal and the transmitted signal of each group of subcarriers includes:
determining a second channel estimation function according to the received signals acquired by the first receiving antenna and the second receiving antenna on the third subcarrier and the fourth subcarrier and the sending signals sent by the first transmitting antenna and the second transmitting antenna on the third subcarrier and the fourth subcarrier;
calculating initial symbol timing deviation corresponding to each group of subcarriers according to the first channel estimation function and the second channel estimation function of each group of subcarriers;
calculating the average value of the initial symbol timing deviation of each group of subcarriers, and taking the average value as the target symbol timing deviation;
wherein, the phase correcting the initial channel estimation value by using the target symbol timing deviation to obtain a final target channel estimation value includes:
using the target symbol timing offset
Figure FDA0002998924280000011
An estimated value determining rule, which is used for carrying out phase correction on the initial channel estimated value to obtain a final target channel estimated value;
wherein the evaluation value determination rule is:
Figure FDA0002998924280000021
Figure FDA0002998924280000022
wherein H11Is a first target channel estimate, H, between the first transmit antenna and the first receive antenna21E is a natural constant, N is the total number of subcarriers, k is the serial number of the subcarriers,
Figure FDA0002998924280000023
for a first initial channel estimate between the first transmit antenna and the first receive antenna,
Figure FDA0002998924280000024
is a second initial channel estimate, H, between the second transmit antenna and the first receive antenna12Is a third target channel estimate, H, between the first transmit antenna and the second receive antenna22For a first target channel estimate between the second transmit antenna and the second receive antenna,
Figure FDA0002998924280000025
for a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure FDA0002998924280000026
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
2. The channel estimation method of claim 1, wherein the initial channel estimation value comprises:
a first initial channel estimation value between the first transmitting antenna and the first receiving antenna, a second initial channel estimation value between the second transmitting antenna and the first receiving antenna, a third initial channel estimation value between the first transmitting antenna and the second receiving antenna, and a fourth initial channel estimation value between the second transmitting antenna and the second receiving antenna.
3. A channel estimation device based on space-frequency block codes, comprising:
a first estimated value determining module, configured to determine an initial channel estimated value by using received signals and transmitted signals of two adjacent subcarriers;
a symbol timing deviation determining module, configured to determine a target symbol timing deviation according to the received signal and the transmitted signal of each group of subcarriers; wherein each group of subcarriers comprises four adjacent subcarriers; the four adjacent subcarriers comprise the two adjacent subcarriers;
a second estimated value determining module, configured to perform phase correction on the initial channel estimated value by using the target symbol timing offset to obtain a final target channel estimated value;
wherein the first estimated value determining module comprises:
the device comprises a first determining unit, a second determining unit and a third determining unit, wherein the first determining unit is used for determining each group of subcarriers, and each group of subcarriers comprises a first subcarrier, a second subcarrier, a third subcarrier and a fourth subcarrier, the serial numbers of the subcarriers of which are sequentially increased;
an adjacent subcarrier determining unit, configured to use a first subcarrier and a second subcarrier in each group of subcarriers as two adjacent subcarriers;
a second determining unit, configured to determine a first channel estimation function according to received signals obtained by the first receiving antenna and the second receiving antenna at the first subcarrier and the second subcarrier and transmission signals sent by the first transmitting antenna and the second transmitting antenna at the first subcarrier and the second subcarrier;
a third determining unit, configured to determine an initial channel estimation value according to the first channel estimation function;
wherein the symbol timing offset determination module comprises:
a fourth determining unit, configured to determine a second channel estimation function according to received signals obtained by the first receiving antenna and the second receiving antenna at the third subcarrier and the fourth subcarrier and transmission signals sent by the first transmitting antenna and the second transmitting antenna at the third subcarrier and the fourth subcarrier;
a calculating unit, configured to calculate an initial symbol timing offset corresponding to each group of subcarriers according to the first channel estimation function and the second channel estimation function of each group of subcarriers;
a fifth determining unit, configured to calculate an average value of the initial symbol timing deviations of each group of subcarriers, and use the average value as the target symbol timing deviation;
wherein the second estimated value determining module is specifically configured to: using the target symbol timing offset
Figure FDA0002998924280000033
An estimated value determining rule, which is used for carrying out phase correction on the initial channel estimated value to obtain a final target channel estimated value; wherein the evaluation value determination rule is:
Figure FDA0002998924280000031
Figure FDA0002998924280000032
wherein H11Is a first target channel estimate, H, between the first transmit antenna and the first receive antenna21E is a natural constant, N is the total number of subcarriers, k is the serial number of the subcarriers,
Figure FDA0002998924280000041
for a first initial channel estimate between the first transmit antenna and the first receive antenna,
Figure FDA0002998924280000042
is a second initial channel estimate, H, between the second transmit antenna and the first receive antenna12Is a third target channel estimate, H, between the first transmit antenna and the second receive antenna22For a first target channel estimate between the second transmit antenna and the second receive antenna,
Figure FDA0002998924280000043
for a third initial channel estimate between the first transmit antenna and the second receive antenna,
Figure FDA0002998924280000044
is a fourth initial channel estimate between the second transmit antenna and the second receive antenna.
4. An electronic device, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the space frequency block code based channel estimation method according to claim 1 or 2 when executing said computer program.
5. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, carries out the steps of the space frequency block code based channel estimation method according to claim 1 or 2.
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