CN115967595A - Semi-blind channel estimation method of MIMO-OTFS system - Google Patents
Semi-blind channel estimation method of MIMO-OTFS system Download PDFInfo
- Publication number
- CN115967595A CN115967595A CN202211520159.7A CN202211520159A CN115967595A CN 115967595 A CN115967595 A CN 115967595A CN 202211520159 A CN202211520159 A CN 202211520159A CN 115967595 A CN115967595 A CN 115967595A
- Authority
- CN
- China
- Prior art keywords
- transmitting
- antenna
- domain
- mimo
- ith
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000001914 filtration Methods 0.000 claims abstract description 27
- 239000011159 matrix material Substances 0.000 claims description 33
- 238000001514 detection method Methods 0.000 claims description 16
- 238000004422 calculation algorithm Methods 0.000 claims description 15
- 230000005540 biological transmission Effects 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 claims description 3
- 238000012216 screening Methods 0.000 claims 1
- 230000003595 spectral effect Effects 0.000 abstract description 6
- 238000004088 simulation Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000004378 air conditioning Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Landscapes
- Radio Transmission System (AREA)
Abstract
The invention discloses a MIMO-OTFS semi-blind channel estimation method, which comprises the following steps: superposing a pilot symbol and a data symbol of a DD (direct D) domain on the ith transmitting antenna to form a transmitting symbol; performing ISFFT on the transmitting symbols, and converting the transmitting signals of the time-frequency domain into time-domain transmitting signals; determining a baseband transmitting signal of the ith transmitting antenna according to the time domain transmitting signal and transmitting the baseband transmitting signal to the jth receiving antenna; converting a receiving signal of a jth receiving antenna into a DD domain, then carrying out two-dimensional matched filtering, and determining time delay and Doppler offset from the ith antenna to the jth receiving antenna; performing preliminary estimation on MIMO channel coefficients; eliminating interference of pilot frequency symbols to received signals, and calculating an estimation result of data symbols; and accurately estimating the MIMO channel coefficient according to the estimation result of the data symbol and the received signal after the interference of the pilot frequency symbol is eliminated. The invention has higher spectral efficiency and low peak-to-average ratio under the scene that the channel change between the OTFS frames is faster.
Description
Technical Field
The invention belongs to the technical field of channel estimation, and particularly relates to a semi-blind channel estimation method of a MIMO-OTFS system.
Background
In a high-speed Time-varying dual-selection wireless channel, OTFS (Orthogonal Time Frequency Space) has attracted extensive research and attention. Compared with the orthogonal frequency division multiplexing modulation technology, the orthogonal time-frequency air conditioning technology is a two-dimensional modulation technology designed in a time delay-doppler domain, has excellent performance under a fast time-varying channel, and is also applied to a MIMO (Multiple-input and Multiple-output) system, i.e., a MIMO-OTFS system, in order to improve the throughput of the system.
Currently, there is an embedded pilot-based channel estimation method in the prior art, which avoids interference between pilot and data symbols by adding a guard interval, while performing channel estimation at the receiver based on a threshold. However, in a low-delay application scenario, the spectrum efficiency of the above method is low, and the accuracy of channel estimation depends on the selection of a threshold; when the maximum delay and the doppler shift are high, the guard interval introduced in the channel estimation method also causes the problem of low frequency potential efficiency.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a semi-blind channel estimation method for a MIMO-OTFS system. The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a semi-blind channel estimation method of a MIMO-OTFS system, wherein the MIMO-OTFS system comprises a transmitting end and a receiving end, and the transmitting end comprises N t A transmitting antenna, the receiving end includes N r A root receiving antenna;
the semi-blind channel estimation method comprises the following steps:
the transmitting end enables the ith (i is more than or equal to 1 and less than or equal to N) t ) The pilot frequency symbol of a delay Doppler DD domain on a root transmitting antenna is superposed with a data symbol to form a transmitting symbol of the DD domain;
the transmitting terminal carries out inverse octave finite Fourier transform (ISFFT) on the transmitting symbol of the DD domain to obtain a transmitting signal of a time-frequency domain, and then converts the transmitting signal of the time-frequency domain into a time-domain transmitting signal;
the transmitting terminal determines the ith (i is more than or equal to 1 and less than or equal to N) according to the time domain transmitting signal t ) A base band transmitting signal of a transmitting antenna is transmitted to a jth receiving antenna;
after converting the received signal of the jth receiving antenna to the DD domain, the receiving terminal performs two-dimensional matched filtering on the received signal of the DD domain by using the pilot symbol, and determines the time delay and the Doppler offset from the ith antenna to the jth receiving antenna according to the matched filtering result;
the receiving end carries out preliminary estimation of the MIMO channel coefficient by utilizing the time delay and the Doppler shift;
the receiving end eliminates the interference of the pilot frequency symbol to the receiving signal according to the preliminary estimation result of the MIMO channel coefficient and calculates the estimation result of the data symbol;
accurately estimating the MIMO channel coefficient according to the estimation result of the data symbol and the received signal after eliminating the interference of the pilot frequency symbol;
when the preset iteration times are reached, taking the accurate estimation result of the MIMO channel coefficient as the semi-blind channel estimation result of the MIMO-OTFS system; otherwise, the receiving end eliminates the interference of the pilot frequency symbol to the received signal according to the accurate estimation result of the MIMO channel coefficient, and returns the estimation result of the calculation data symbol.
In an embodiment of the present invention, the step of, after the receiving end converts the received signal of the jth receiving antenna to the DD domain, performing two-dimensional matched filtering on the received signal of the DD domain by using the pilot symbol, and determining the delay and the doppler offset from the ith antenna to the jth receiving antenna according to a result of the matched filtering includes:
the receiving end converts the received signal of the jth receiving antenna into a DD domain to obtain a received signal of the DD domain;
with y j Using the pilot symbol of the ith transmitting antenna and the received signal of the jth receiving antenna in DD domain to perform two-dimensional matched filtering, y j For the received signal y j In the form of a matrix;
when the matched filtering result is larger than a preset threshold eta, the slave y j Determine the delay and doppler offset from the ith transmitting antenna to the jth receiving antenna at (l, k).
In an embodiment of the present invention, the receiving end performs two-dimensional matched filtering according to the following formula:
in the formula,
said pilot symbols representing the ith transmit antenna represent a conjugate operation, V ji And (l, k) represents a two-dimensional matched filtering result with the (l, k) as a reference coordinate, M and N respectively represent the maximum delay lattice number and the maximum Doppler lattice number of the delay Doppler domain, M and N are summation subscripts, M is greater than or equal to 0 and less than or equal to M, and N is greater than or equal to 0 and less than or equal to N.
In one embodiment of the present invention, the preset threshold is set
Wherein +>
Represents the variance of the pilot symbols, and K is a preset constant.
In an embodiment of the present invention, the step of performing preliminary estimation on the MIMO channel coefficient by the receiving end using the delay and the doppler shift includes:
the receiving end performs Minimum Mean Square Error (MMSE) estimation from the ith transmitting antenna to the jth receiving antenna by using the time delay and the Doppler shift according to the following formula to obtain a preliminary estimation result of the MIMO channel coefficient:
in the formula,
representing the P-th from the ith transmitting antenna to the jth receiving antenna ji The channel characteristic matrix of the path->
Is->
In the form of a matrix of->
A covariance matrix representing the channel coefficients, < > >>
Represents the p-th path channel coefficient from the ith transmitting antenna to the jth receiving antenna, and->
Represents the noise power of the jth receiving antenna in combination with the reference signal>
Means for selecting a channel coefficient for transmission from the i transmit antenna to the jth receive antenna based on the variance of the channel coefficients for the p path in the transmit antenna and the jth receive antenna, and means for determining the channel coefficient for the transmission based on the variance of the channel coefficients for the i transmit antenna and the jth receive antenna>
Representing the variance of said data symbols, I MN Denotes an M × N identity matrix, H denotes Hermite transpose, H j The initial estimation result of the MIMO channel coefficient of the jth receiving antenna is obtained.
In one embodiment of the present invention, after eliminating interference of pilot symbols to the received signal, the matrix form of the received signal is:
in the formula, H ji An equivalent channel matrix representing the delay-doppler domain from the ith transmit antenna to the jth receive antenna,
and the matrix form of the received signal after the jth receiving antenna eliminates the pilot symbol interference is shown.
In an embodiment of the present invention, after the estimation result of the data symbol is calculated by using the MIMO-OTFS message passing detection algorithm, the received signal is updated according to the following formula:
in the formula,
represents the data symbol of the ith transmit antenna, <' > greater or lesser>
Means for evaluating a data symbol of an ith transmit antenna calculated using a MIMO-OTFS message transfer detection algorithm, means for determining a value of a data symbol in a data symbol based on a correlation of the evaluation result and the data symbol in the ith transmit antenna, and means for determining whether the evaluation result is valid>
h ji Representing a vector of channel coefficients representing i transmit antennas to j receive antennas, w j The jth receive antenna's noise vector,
in an embodiment of the present invention, the step of accurately estimating MIMO channel coefficients according to the estimation result of the data symbols and the received signal without interference of pilot symbols includes:
based on the estimation result of the data symbol and the updated received signal, the MIMO channel coefficient is accurately estimated according to the following formula:
in the formula,
compared with the prior art, the invention has the beneficial effects that:
the invention provides a MIMO-OTFS semi-blind channel estimation method, which is characterized in that zadoff-chu sequences with different sequence root indexes are used as pilot symbols, data symbols on different transmitting antennas and a delay Doppler domain are superposed to form a transmitting symbol of a DD domain, and a transmitting signal is finally recovered at a receiving end through an algorithm of iterative channel estimation and signal detection. The method can obtain good channel estimation effect without adding a guard interval, so that the method has higher spectral efficiency and low peak-to-average ratio under the scene that the channel between the OTFS frames changes rapidly.
The present invention will be described in further detail with reference to the drawings and examples.
Drawings
Fig. 1 is a flowchart of a semi-blind channel estimation method of a MIMO-OTFS system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of bit error rate simulation results of different pilot power ratios according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating bit error rate comparison results provided by an embodiment of the present invention;
FIG. 4 is a graph comparing normalized error of channel estimation provided by embodiments of the present invention;
FIG. 5 is a graph illustrating the convergence of the bit error rate with the number of iterations for different SNR according to an embodiment of the present invention;
FIG. 6 is a graph showing the convergence of the normalized channel estimation error with the number of iterations for different SNR according to an embodiment of the present invention;
fig. 7 is a graph comparing the effective spectral efficiency provided by embodiments of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Fig. 1 is a flowchart of a semi-blind channel estimation method for a MIMO-OTFS system according to an embodiment of the present invention. As shown in fig. 1, an embodiment of the present invention provides a semi-blind channel estimation method for a MIMO-OTFS system, where the MIMO-OTFS system includes a transmitting end and a receiving end, and the transmitting end includes N t The receiving end comprises N r A root receiving antenna;
the semi-blind channel estimation method comprises the following steps:
s1, transmitting the ith (i is more than or equal to 1 and less than or equal to N) t ) Pilot symbols of a delay Doppler DD domain on a root transmitting antenna are superposed with data symbols to form transmitting symbols of the DD domain;
s2, the transmitting terminal performs Inverse Sine Finite Fourier Transform (ISFFT) on the transmitting symbol of the DD domain to obtain a transmitting signal of the time-frequency domain, and then converts the transmitting signal of the time-frequency domain into a time-domain transmitting signal;
s3, the transmitting terminal determines the ith (i is more than or equal to 1 and less than or equal to N) according to the time domain transmitting signal t ) The base band transmitting signal of the transmitting antenna is transmitted to the jth receiving antenna;
s4, after converting the received signal of the jth receiving antenna to a DD domain, the receiving end performs two-dimensional matched filtering on the received signal of the DD domain by using a pilot symbol, and determines the time delay and the Doppler offset from the ith antenna to the jth receiving antenna according to a matched filtering result;
s5, the receiving end performs preliminary estimation on the MIMO channel coefficient by using the time delay and the Doppler shift;
s6, the receiving end eliminates the interference of the pilot frequency symbol on the received signal according to the preliminary estimation result of the MIMO channel coefficient and calculates the estimation result of the data symbol;
s7, accurately estimating the MIMO channel coefficient according to the estimation result of the data symbol and the received signal after eliminating the interference of the pilot frequency symbol;
s9, when the preset iteration times are reached, taking the accurate estimation result of the MIMO channel coefficient as the semi-blind channel estimation result of the MIMO-OTFS system; otherwise, the receiving end eliminates the interference of the pilot frequency symbol to the received signal according to the accurate estimation result of the MIMO channel coefficient, and returns to the step of calculating the estimation result of the data symbol.
Specifically, at the transmitting end of the MIMO-OTFS system, i (i is more than or equal to 1 and less than or equal to N) t ) Pilot symbols in DD (Delay-Doppler) domain on root transmit antenna
And the data symbol->
Superposed to obtain the transmitted symbol x in DD domain i [l,k]：
Then, the process of the present invention is carried out,transmitting symbol x of DD domain is transformed by ISFFT (inverse symplectic finite Fourier transform) i [l,k]Transforming to a time-frequency domain to obtain a transmission signal of the time-frequency domain:
wherein, F M And F N Fourier transform matrices of dimensions M and N, respectively, H representing Hermite transpose, time-frequency domain transmission signal
Dimension of (d) is M × N.
Transmitting signals of time-frequency domain through Heisenberg transformation and pulse shaping
Conversion into a continuous time-domain transmission signal S i ：
In the formula I M Representing a unit array of dimensions M x M, F N Representing an N × N fourier transform matrix.
Further, the matrix form of the time domain transmitting signal is converted into the vector form, and then the baseband transmitting signal s of the ith transmitting antenna can be obtained i (t)：
The transmitting terminal of the MIMO-OTFS system carries out the inverse process opposite to the transmitting terminal on the received signal R, namely, the Virgener transformation and the SFFT transformation are sequentially carried out to obtain the time-frequency domain received signal Y TF And a reception signal y of the DD domain j Respectively, as follows:
similarly, the DD domain received signal y on the jth receiving antenna may also be used j Is converted into vector form:
based on the analysis, the input-output relationship from the ith transmitting antenna to the jth receiving antenna in the delay-doppler domain can be obtained:
wherein H ji Equivalent channel matrix, x, representing the delay-doppler domain i Is x i In vector form, i.e.
Combination formula>
The equivalent channel matrix for the delay-doppler domain can be expressed as:
wherein the transmit pre-processing matrix
Receiving and processing matrix->
Channel characteristic matrix->
The dimensionality of the 3 matrices is MN x MN, P ji Represents the number of channel paths from the ith transmitting antenna to the jth receiving antenna, and->
And &>
Respectively representing the channel gain, time delay and Doppler shift of the p-th path channel from the ith transmitting antenna to the jth receiving antenna.
Further, with H ji Representing the DD domain equivalent channel matrix from the ith transmitting antenna to the jth receiving antenna, the input-output relationship of the MIMO-OTFS system can be represented as:
the following is defined:
the input-output relationship of the MIMO-OTFS system can be written as:
y MIMO ＝H MIMO x MIMO +v MIMO 。
in the step S4, after the receiving end converts the received signal of the jth receiving antenna to the DD domain, the receiving end performs two-dimensional matched filtering on the received signal of the DD domain by using the pilot symbol, and determines the delay and the doppler offset from the ith antenna to the jth receiving antenna according to the matched filtering result, including:
s401, the receiving end converts the received signal of the jth receiving antenna to a DD domain to obtain a received signal of the DD domain;
s402, using y j Using the ith hair as the reference coordinateCarrying out two-dimensional matched filtering on a pilot frequency symbol of a transmitting antenna and a receiving signal of a jth receiving antenna in a DD (direct digital) domain;
s403, when the matched filtering result is larger than a preset threshold eta, receiving the signal y from the receiving terminal j And (l, k), determining the time delay and the Doppler shift from the ith transmitting antenna to the jth receiving antenna.
Specifically, with reference to the above equations (1) and (2), the received signal in the receiving end DD domain on which the pilot symbol is superimposed is represented as:
wherein, the matrix
A p-th path channel feature matrix, <' > that represents the ith transmit antenna to the jth receive antenna>
And &>
Respectively representing the time delay and the Doppler shift of the p-th path channel from the ith transmitting antenna to the jth receiving antenna.
Optionally, in this embodiment, different zadoff-chu sequences are used to perform two-dimensional matched filtering to obtain time delays from different transmitting antennas to different paths of the receiving end
And Doppler shift->
The formula of the two-dimensional matched filtering is estimated as follows: />
In the formula,
said pilot symbols representing the ith transmit antenna, representing a conjugate operation, V ji And (l, k) represents a two-dimensional matched filtering result with the (l, k) as a reference coordinate, M and N respectively represent the maximum delay lattice number and the maximum Doppler lattice number of the delay Doppler domain, M and N are summation subscripts, M is greater than or equal to 0 and less than or equal to M, and N is greater than or equal to 0 and less than or equal to N.
It should be understood that when V ji When (l, k) is greater than a predetermined threshold η, the delay and doppler shift from the ith antenna to the jth receiving antenna are considered as (l, k), and the predetermined threshold is exemplarily set
Wherein it is present>
Represents the variance of the pilot symbols, and K is a preset constant.
Obtaining the delay and the doppler shift from the ith antenna to the jth receiving antenna, equation (3) can be further expressed as:
in the above formula, the first and second carbon atoms are,
can be respectively based on the matrix->
And superimposed->
And &>
Comprises the following steps:
equation (4) can be further written as:
wherein,
the minimum mean square error estimate, MMSE, estimation of the transmit antenna to the jth receive antenna can thus be performed using equation (4):
in the formula,
indicates the ith transmission dayLine to jth receiving antenna P ji The channel characteristic matrix of the path->
Is->
In the form of a matrix of channel coefficients, a covariance matrix of channel coefficients>
Represents a desired operator, <' > or>
Covariance matrix of noise vector ≥>
Representing the noise power of the jth receiving antenna, I MN Expressing an M N identity matrix, a random matrix omega d Has a cooperative defense difference matrix of->
Representing the variance of the data symbols, the data is combined with noise and other pilot sequences on the transmit antennas as a covariance matrix of the interference part
Represents the p-th path channel coefficient from the ith transmitting antenna to the jth receiving antenna, and->
Represents the variance of the channel coefficients for the p path from the i transmit antenna to the j receive antenna,
h ji representing the channel coefficient vector, h, from the i transmit antenna to the jth receive antenna j The initial estimation result of the MIMO channel coefficient of the jth receiving antenna is obtained.
By calculating that j is more than or equal to 1 and less than or equal to N r To obtain N r And (3) the preliminary estimation result of the channel coefficient is grouped, so that the interference of pilot symbols to the received signal can be eliminated:
in the formula,
representing the residual part of the pilot symbol to data interference due to channel coefficient estimation errors, H ji An equivalent channel matrix representing the delay-doppler domain from the ith transmit antenna to the jth receive antenna, < '> or <' >>
And pilot symbols representing the delay-Doppler domain of the ith transmitting antenna.
Assuming that the sum of the transmit power of the pilot symbols and the data symbols on each transmit antenna is the same and the power allocation ratio is the same, the expectation and variance of interference are:
wherein,
representing the error due to the channel coefficient estimate, var represents the variance operator, and @>
Representing the variance of the pilot symbols.
Combining the preliminary estimation result of the MIMO channel coefficient and the received signal after removing the pilot frequency interference, and calculating by utilizing an MIMO-OTFS message transmission detection algorithm to obtain N t Estimation of data symbols for root transmit antennas
The mean and variance of the message passing detection algorithm are: />
Since the estimation result x of the data symbol is obtained d And a preliminary estimate h of the channel coefficient j Thus, a matrix can be obtained
And &>
Then the received signal may be further represented as:
where the data and pilot superposition matrix can be expressed as
Noise and interference directionQuantity can be expressed as>
Data symbol ≥ for the ith transmit antenna>
In the form of a vector of (a),
the estimation result of the data symbol of the ith transmitting antenna calculated by using the MIMO-OTFS message passing detection algorithm is shown,
h ji representing a vector of channel coefficients representing i transmit antennas to j receive antennas, w j The jth receive antenna's noise vector, device for selecting or keeping>
Then, the step of accurately estimating the MIMO channel coefficient according to the estimation result of the data symbol and the received signal from which the interference of the pilot symbol is eliminated includes:
based on the estimation result of the data symbol and the updated received signal, the MIMO channel coefficient is accurately estimated according to the following formula:
in the formula, xi w The covariance matrix of (a) can be expressed as:
at this time, if the preset iteration times are not reached, the data detection is carried out on the received signals according to the accurate estimation value of the MIMO channel coefficient and the following formula by combining the message transmission detection algorithm, and x is utilized in the next iteration process d The channel coefficients are again accurately estimated.
It should be noted that, when the message passing detection algorithm is used for detection here, the calculation of the mean and the variance can be performed according to the formulas (6) and (7), but the error term caused by channel coefficient estimation in the variance needs to be synchronously changed into:
the bit error rate simulation and comparison are carried out on the MIMO-OTFS semi-blind channel estimation scheme, the message transfer detection algorithm is used as the detection algorithm of the MIMO-OTFS, and the damping coefficient is 0.7. In the simulation, the time delay and Doppler frequency shift of a plurality of input antennas and a plurality of output antennas are consistent, the channel coefficient obeys complex Gaussian distribution, and only integer Doppler frequency shift is considered.
The MIMO-OTFS semi-blind channel estimation method provided by the present invention is further explained by simulation below.
Table 1 shows simulation parameters of MIMO-OTFS semi-blind channel estimation set in this embodiment:
TABLE 1
Fig. 2 is a schematic diagram of bit error rate simulation results of different pilot power ratios according to an embodiment of the present invention. As shown in fig. 2, in order to ensure correctness and fairness, for a 2 × 2MIMO-OTFS, the signal-to-noise ratio is 10dB, the total power of each delay-doppler block is guaranteed to be constant, and the sum of the pilot power and the data power is 1, that is, the sum is 1
As such, the signal-to-noise ratio SNR may be defined as ∑ or {>
As can be seen from FIG. 2, a pilot power ratio of 0.2 is an approximately optimal power allocation, and therefore the pilot power ratio is greater or less than in subsequent simulation results>
Data power duty ratio->
Fig. 3 is a schematic diagram of bit error rate comparison results provided by the embodiment of the present invention. Please refer to fig. 3, the perfect channel estimation and pilot power are still performed with 2 × 2mimo-OTFS
The semi-blind channel provided by the present invention is used as an example, the semi-blind signal estimation method and the embedded pilot method in the prior art are respectively used for channel estimation, the obtained error rate is compared with the error rate of perfect channel estimation, and in order to ensure fairness, the total transmission power in the present embodiment is constant, that is, the total power of the existing embedded pilot method is constant->
I.e., the pilot power is 18.9dB of the data power, the channel is estimated, illustratively, using a threshold selected to ÷ greater than the data power>
Wherein E s Is the single symbol energy of the delay-doppler domain.
As can be seen from FIG. 3, the bit error rate curve of the semi-blind channel estimation method and the perfect channel estimation provided by the invention has only about 2dB performance loss, and has more excellent bit error rate performance than the existing embedded pilot frequency method.
Furthermore, in order to compare the accuracy of the channel estimation performed by the semi-blind channel estimation method and the embedded pilot method provided by the present invention, the embodiment simulates the channel estimation error with the signal-to-noise ratio of 0dB to 10dB, and similarly, the channel estimation gate in the embedded pilot method is selected as
Fig. 4 is a graph comparing normalized error of channel estimation provided by the embodiment of the present invention, and as shown in fig. 4, the channel estimation error of the semi-blind channel estimation method provided by the present invention is lower than that of the existing threshold-based channel estimation method after 2 dB.
Fig. 5 and fig. 6 are graphs showing convergence curves of the error rate and the normalized channel estimation error with the number of iterations for different signal-to-noise ratios according to the embodiment of the present invention. Since the semi-blind channel estimation method provided by the present invention is an iterative estimation process of channel estimation and signal detection, the present embodiment further checks the convergence of the algorithm, and as can be seen from fig. 5 to 6, the iterative algorithm in the MIMO-OTFS semi-blind channel estimation method has the advantages of fast convergence speed and strong convergence stability.
Defining effective spectral efficiency
It should be understood that the existing MIMO-OTFS embedded pilot method relies on much delayThe pilot in the doppler domain estimates the channel, and therefore, enough guard interval is left in the delay-doppler domain, but the overhead of the guard interval is not a lot, especially when the delay and doppler spread of the channel are large. Fig. 7 is a graph comparing the effective spectral efficiency provided by embodiments of the present invention. Referring to fig. 7, the semi-blind channel estimation method provided by the present invention has a spectrum efficiency closer to that of the perfect channel estimation scheme under a higher signal-to-noise ratio, and an effective spectrum efficiency much higher than that of the embedded pilot method, and under a condition of a larger channel delay and doppler spread and a larger number of antennas, the effective spectrum efficiency of the embedded pilot method is further reduced; in addition, the performance of the existing embedded pilot frequency method excessively depends on the selection of the threshold, but the invention has low requirement on the selection of the threshold because the peak value of the matched filtering is larger.
The beneficial effects of the invention are that:
the invention provides a MIMO-OTFS semi-blind channel estimation method, which is characterized in that zadoff-chu sequences with different sequence root indexes are used as pilot symbols, data symbols on different transmitting antennas are superposed in a delay Doppler domain to form transmitting symbols in a DD domain, and finally, transmitting signals are recovered at a receiving end through an algorithm of iterative channel estimation and signal detection. The method can obtain good channel estimation effect without adding a guard interval, so that the method has higher spectral efficiency and low peak-to-average ratio under the scene that the channel between the OTFS frames changes rapidly.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.
While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, numerous simple deductions or substitutions may be made without departing from the spirit of the invention, which shall be deemed to belong to the scope of the invention.
Claims (8)
1. A semi-blind channel estimation method of a MIMO-OTFS system is characterized in that the MIMO-OTFS system comprises a transmitting end and a receiving end, wherein the transmitting end comprises N t A root transmitting antenna, the receiving end including N r A root receiving antenna;
the semi-blind channel estimation method comprises the following steps:
the transmitting end enables the ith (i is more than or equal to 1 and less than or equal to N) t ) Pilot symbols of a delay Doppler DD domain on a root transmitting antenna are superposed with data symbols to form transmitting symbols of the DD domain;
the transmitting terminal carries out inverse octave finite Fourier transform (ISFFT) on the transmitting symbol of the DD domain to obtain a transmitting signal of a time-frequency domain, and then converts the transmitting signal of the time-frequency domain into a time-domain transmitting signal;
the transmitting terminal determines the ith (i is more than or equal to 1 and less than or equal to N) according to the time domain transmitting signal t ) A baseband transmitting signal of a transmitting antenna is transmitted to a jth receiving antenna;
after the receiving end converts the received signal of the jth receiving antenna to a DD domain, the receiving end performs two-dimensional matched filtering on the received signal of the DD domain by using the pilot symbols, and determines the time delay and the Doppler shift from the ith antenna to the jth receiving antenna according to a matched filtering result;
the receiving end carries out preliminary estimation of the MIMO channel coefficient by utilizing the time delay and the Doppler shift;
the receiving end eliminates the interference of the pilot frequency symbol to the receiving signal according to the preliminary estimation result of the MIMO channel coefficient and calculates the estimation result of the data symbol;
accurately estimating the MIMO channel coefficient according to the estimation result of the data symbol and the received signal after eliminating the interference of the pilot frequency symbol;
when the preset iteration times are reached, taking the accurate estimation result of the MIMO channel coefficient as the semi-blind channel estimation result of the MIMO-OTFS system; otherwise, the receiving end eliminates the interference of the pilot frequency symbol to the receiving signal according to the accurate estimation result of the MIMO channel coefficient, and returns the estimation result of the calculation data symbol.
2. The method for estimating the semi-blind channel of the MIMO-OTFS system according to claim 1, wherein the step of performing two-dimensional matched filtering on the received signal in the DD domain by using the pilot symbol after the receiving end converts the received signal of the jth receiving antenna into the DD domain, and determining the delay and the doppler offset from the ith antenna to the jth receiving antenna according to a result of the matched filtering includes:
the receiving end converts the received signal of the jth receiving antenna into a DD domain to obtain a received signal of the DD domain;
with y j In (l, k) as referenceCoordinate, using the pilot symbol of the ith transmitting antenna and the receiving signal of the jth receiving antenna in DD domain to make two-dimensional matched filtering, y j For the received signal y j y j In the form of a matrix;
when the matched filtering result is greater than a preset threshold eta, the slave y j Determine the delay and doppler offset from the ith transmitting antenna to the jth receiving antenna at (l, k).
3. The method of estimating a semi-blind channel of a MIMO-OTFS system according to claim 2, wherein the receiving end performs two-dimensional matched filtering according to the following formula:
in the formula,
said pilot symbols representing the ith transmit antenna, representing a conjugate operation, V ji And (l, k) represents a two-dimensional matched filtering result with (l, k) as a reference coordinate, M and N respectively represent the maximum delay lattice number and the maximum Doppler lattice number of the delay Doppler domain, M and N are summation subscripts, M is greater than or equal to 0 and less than or equal to M, and N is greater than or equal to 0 and less than or equal to N.
4. The method of claim 3, wherein the preset threshold is set as a threshold
Wherein +>
Represents the variance of the pilot symbols, and K is a preset constant. />
5. The method for estimating a semi-blind channel of a MIMO-OTFS system according to claim 1, wherein the step of the receiving end performing the preliminary estimation of the MIMO channel coefficient by using the delay and the doppler shift comprises:
the receiving end performs Minimum Mean Square Error (MMSE) estimation from the ith transmitting antenna to the jth receiving antenna by using the time delay and the Doppler shift according to the following formula to obtain a preliminary estimation result of the MIMO channel coefficient:
in the formula,
representing the P-th from the ith transmitting antenna to the jth receiving antenna ji The channel characteristic matrix of the path->
Is->
In the form of a vector of (a),
a covariance matrix representing the channel coefficients, < > >>
Represents the p-th path channel coefficient from the ith transmitting antenna to the jth receiving antenna, and->
Represents the noise power of the jth receiving antenna, based on the signal strength of the signal>
Representing i transmission daysThe variance of the channel coefficients of the p-th path, taken from the line to the jth receiving antenna, <' > is greater than>
Representing the variance of said data symbols, I MN Denotes an M × N identity matrix, H denotes Hermite transpose, H j The initial estimation result of the MIMO channel coefficient of the jth receiving antenna is obtained.
6. The method of claim 5, wherein after the interference of pilot symbols to the received signal is eliminated, the received signal is:
in the formula, H ji An equivalent channel matrix representing the delay-doppler domain from the ith transmit antenna to the jth receive antenna,
indicating the received signal after the jth receiving antenna eliminates the pilot symbol interference.
7. The method of claim 6, wherein the received signal is updated according to the following formula after the estimation result of the data symbol is calculated by using the MIMO-OTFS message transfer detection algorithm:
in the formula,
a data symbol representing the ith transmit antenna, device for combining or screening>
Means for evaluating the data symbol of the ith transmit antenna calculated using a MIMO-OTFS message passing detection algorithm, and->
h ji Representing a vector of channel coefficients representing i transmit antennas to j receive antennas, w j Representing the noise vector of the jth receiving antenna,
/>
8. the method of claim 7, wherein the step of estimating the MIMO channel coefficients accurately according to the estimation result of the data symbols and the received signals after the interference of the pilot symbols is eliminated comprises:
based on the estimation result of the data symbol and the updated received signal, the MIMO channel coefficient is accurately estimated according to the following formula:
in the formula,
/>
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211520159.7A CN115967595A (en) | 2022-11-30 | 2022-11-30 | Semi-blind channel estimation method of MIMO-OTFS system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211520159.7A CN115967595A (en) | 2022-11-30 | 2022-11-30 | Semi-blind channel estimation method of MIMO-OTFS system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115967595A true CN115967595A (en) | 2023-04-14 |
Family
ID=87363654
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211520159.7A Pending CN115967595A (en) | 2022-11-30 | 2022-11-30 | Semi-blind channel estimation method of MIMO-OTFS system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115967595A (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018195548A1 (en) * | 2017-04-21 | 2018-10-25 | Cohere Technologies | Communication techniques using quasi-static properties of wireless channels |
| WO2021171707A1 (en) * | 2020-02-28 | 2021-09-02 | Kddi株式会社 | Transmission device, reception device, communication method, and baseband chip that use highly accurate channel estimation scheme in communication using otfs modulation |
| CN113395221A (en) * | 2021-04-25 | 2021-09-14 | 北京邮电大学 | Orthogonal time-frequency-space joint-based channel estimation and symbol detection method |
| CN114826836A (en) * | 2022-04-25 | 2022-07-29 | 广州海格通信集团股份有限公司 | Signal generation method, signal generation device, signal transmitting equipment and storage medium |
| CN115086114A (en) * | 2022-06-10 | 2022-09-20 | 西安电子科技大学 | Channel estimation method based on distributed placement of orthogonal time-frequency space OTFS pilot frequency |
-
2022
- 2022-11-30 CN CN202211520159.7A patent/CN115967595A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018195548A1 (en) * | 2017-04-21 | 2018-10-25 | Cohere Technologies | Communication techniques using quasi-static properties of wireless channels |
| WO2021171707A1 (en) * | 2020-02-28 | 2021-09-02 | Kddi株式会社 | Transmission device, reception device, communication method, and baseband chip that use highly accurate channel estimation scheme in communication using otfs modulation |
| CN113395221A (en) * | 2021-04-25 | 2021-09-14 | 北京邮电大学 | Orthogonal time-frequency-space joint-based channel estimation and symbol detection method |
| CN114826836A (en) * | 2022-04-25 | 2022-07-29 | 广州海格通信集团股份有限公司 | Signal generation method, signal generation device, signal transmitting equipment and storage medium |
| CN115086114A (en) * | 2022-06-10 | 2022-09-20 | 西安电子科技大学 | Channel estimation method based on distributed placement of orthogonal time-frequency space OTFS pilot frequency |
Non-Patent Citations (3)
| Title |
|---|
| HIMANSHU B. MISHRA: "Iterative Channel Estimation And Data Detection in OTFS Using Superimposed Pilots", 《2021 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS》, 31 December 2021 (2021-12-31) * |
| HIMANSHU B. MISHRA: "OTFS Channel Estimation and Data Detection Designs With Superimposed Pilots", 《IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS》, vol. 21, no. 4, 30 April 2022 (2022-04-30), pages 2258 - 2274 * |
| WEIJIE Y UAN: "Data-Aided Channel Estimation for OTFS Systems With a Superimposed Pilot and Data Transmission Scheme", 《IEEE WIRELESS COMMUNICA TIONS LETTERS》, vol. 10, no. 9, 30 September 2021 (2021-09-30), pages 1954 - 1958, XP011876027, DOI: 10.1109/LWC.2021.3088836 * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112202479A (en) | Low-complexity signal detection method for MIMO-orthogonal time-frequency space system | |
| CN106506415B (en) | A kind of method of multi-user MIMO-OFDM system channel estimation | |
| CN103428154B (en) | The transform domain multiplexing method of the dual-selection channel based on Vector OFDM | |
| CN101345727B (en) | Solving method and device of signal channel shortening equalization coefficient | |
| Safi et al. | Higher order cumulants for identification and equalization of multicarrier spreading spectrum systems | |
| CN101291311B (en) | Synchronization implementing method and device for multi-input multi-output orthogonal frequency division multiplexing system | |
| CN110212951B (en) | Large-scale MIMO channel estimation method based on Butler matrix | |
| CN114039821B (en) | Wideband mmWave MIMO-OFDM system wave beam space channel estimation method | |
| CN102255836B (en) | Blind signal to noise ratio estimation method based on multiple input multiple output (MIMO)-orthogonal frequency division multiplexing (OFDM) signal cyclostationarity | |
| Francis et al. | Delay-doppler channel estimation in OTFS systems using DoA estimation techniques | |
| CN103414678A (en) | Doubly selective channel transform domain equalization method based on Vector OFDM | |
| CN101523760A (en) | Intersymbol interference mitigation | |
| CN102413080B (en) | Method for estimating channel in high-speed moving TDD-LTE (time division duplex-long time evolution) uplink | |
| CN102113285A (en) | A simplified equalizationscheme for distributed resource allocation in multi-carrier systems | |
| CN103475603B (en) | Communication system blind channel estimation method based on S order parameter non-orthogonal transformation | |
| CN104218984B (en) | Using the both-end frequency domain beam search method of compressed sensing | |
| CN116405348A (en) | Communication perception integrated system array antenna and 5G new air interface angle estimation method | |
| CN102035787A (en) | Band sequencing Turbo enhancement method for multiple-input multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) wireless communication receiver | |
| CN115967595A (en) | Semi-blind channel estimation method of MIMO-OTFS system | |
| Mutlu et al. | Channel Estimation In Intelligent Reflecting Surfaces for 5G and Beyond | |
| CN100493052C (en) | Method for channel evaluating of weak energy parallel PN sequence | |
| Priya et al. | Particle filter based nonlinear data detection for frequency selective mm-Wave MIMO-OFDM systems | |
| CN109217954A (en) | Low complex degree OSDM block balance method based on double selection fading channels | |
| CN114978254B (en) | Machine learning auxiliary low-complexity robust precoding algorithm based on OFDM system | |
| CN112688889B (en) | Channel estimation method and device of unmanned aerial vehicle measurement and control system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |