Disclosure of Invention
Aiming at the existing technical defects, the invention provides a perception parameter estimation method of a communication perception integrated system based on SS-OTFS, namely, an ISAC transmission framework based on space expansion orthogonal time-frequency space (SS-OTFS) modulation, and a perception parameter estimation method based on unitary approximate message transfer (UAMP) Sparse Bayesian Learning (SBL). Wherein, the signal transmitted to the User Equipment (UE) by the Base Station (BS) is reflected by the UE and scattered by surrounding scatterers, and then received by a radar receiver which is positioned at the same position as the transmitter to obtain an echo signal. The UAMP-SBL-based method of the receiver utilizes prior information and an iterative process to process echo signals for perceptual parameter estimation, including delay and Doppler shift estimation. The method can effectively reduce the computational complexity of the perception parameter estimation.
In order to achieve the above purpose, the specific technical scheme adopted by the invention is as follows:
a perception parameter estimation method of a communication perception integrated system based on SS-OTFS at least comprises the following steps:
step A: writing a radar echo signal vector received by a radar receiver into a form of multiplying a high-dimensional matrix by a sparse vector;
and (B) step (B): performing unitary transformation on the radar echo signal vector in the step A;
step C: b, initializing basic parameters for the unitary transformed signals in the step B, and performing iterative computation through a UAMP-SBL algorithm;
step D: c, taking the mean value and the variance of the sparse vector and other parameters obtained by calculation in the step C as return values, and repeating the process in the step C until the circulation is finished;
step E: and D, further processing the sparse vector estimated value obtained in the step D to obtain estimated perception parameters (delay and Doppler).
As a further improvement, one BS serves the scenario of K UEs, in the downlink, the BS broadcasts a common message to K UEs within the signal coverage area, and perceives the location information of the UEs based on the received echoes; provided with N BS There are P independent separable paths between the BS of the root antenna and each single antenna UE, then the radar return signal is expressed as:
wherein ,
is a radar echo signal in the time delay angle domain, a>
Is the fading coefficient of the radar channel, alpha is N for distributing power to the signal on each antenna
BS ×N
BS Dimensional matrix, precoding matrix P multiplexes signals onto each antenna, x
TD Is a transmitted symbol vector in the delay-doppler domain, < >>
Is an additive white gaussian noise column vector,/->
Is N for spatially expanding a signal
BS ×N
BS Is a matrix of the discrete fourier transform of (c),
is the steering vector of the antenna array, where θ
i,p Is the relative angle (.)
T and (·)
H The transpose and Hermite transpose are represented respectively.
MN x MN dimensional permutation matrices representing the relative delay effects, wherein,
a diagonal matrix of MN x MN representing the effect of relative doppler shift, wherein,
m and N are denoted as the number of subcarriers and the number of slots respectively,
and
The round trip delay index and the Doppler shift index related to the ith path of the ith UE;
wherein ,τi,p and vi,p The p-th path related relative delay and relative doppler shift for the i-th UE are respectively, Δf and T are the subcarrier spacing and the slot duration, Δf=1/T.
As a further refinement, the relative angle of the BS and UE is known or estimated available.
As a further improvement, in step a, the formula (1) is transformed and rewritten as:
wherein ,
corresponds to a set of delay and doppler shift indices; taking the set of values as a column in a high-dimensional matrix phi, and selecting the round trip delay index to be within the range +.>
The Doppler index selection range is +.>
For the sense matrix Φ, h has non-zero values +.>
Otherwise, zero is set, so that a sparse vector is formed; wherein Φ is MNN
BS The dimension matrix of the xLM (2N-1), L is the number of separable relative angles; let phi be +.>
A dimension matrix; the perceptual parameters are inferred by estimating the locations of non-zero values in the sparse vector h.
As a further improvement, in step B, Φ is subjected to SVD decomposition Φ=uΛv
H And unitary transforming equation (5), i.e
The method comprises the following steps:
r=Ψh+ω (25)
wherein ,
and
Omega is 0 as mean and beta as covariance matrix
-1 I is gaussian noise, β is the accuracy of the noise.
As a further improvement, in step C, the iterative process of information in the UAMP-SBL algorithm includes the following six steps:
step C1: initializing and setting basic parameters: let λ= ΛΛ
H 1,1 is a column vector with all elements 1,
(0) =0.01,
s=0, 0 is a column vector sum of all 0 elements and t=0;
step (a)C2: calculating τ p and p:
wherein·represents the dot product of two vectors;
step C3, calculating v
z ,
and
Where/represents two vector dot divisions;
step C4: calculating τ s and s:
s=τ s ·(r-p) (32)
step C5: calculating τ q and q:
step C6: calculating the mean of sparse vectors
Variance τ
h Parameter->
and ∈:
as a further improvement, in step D, the updated basic parameters, including the mean and variance of the estimated value of the sparse vector h, are returned to step C2 for the next iteration.
In step E, the estimated sparse vector h is identified to obtain a set of delay index and doppler shift index of the corresponding position, and then they are converted to the relative delay and the relative doppler shift by the formula (4), so as to obtain the required perception parameter.
The invention provides a perception parameter estimation method for an ISAC system based on SS-OTFS. After the radar receiver performs unitary transformation processing on the radar echo signals, the UAMP-SBL algorithm is utilized to iterate the echo signals. Compared with the SBL algorithm, the method can obtain lower calculation complexity and higher estimation accuracy.
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Referring to fig. 1, a flowchart of a method for estimating a perception parameter based on communication perception integration supporting SS-OTFS is provided in an embodiment of the present invention, where a UAMP-SBL algorithm is used at a radar receiver to process radar echo signals, and the method at least includes the following steps:
step A: writing a radar echo signal vector received by a radar receiver into a form of multiplying a high-dimensional matrix by a sparse vector;
and (B) step (B): performing unitary transformation on the radar echo signal vector in the step A;
step C: b, initializing basic parameters for the unitary transformed signals in the step B, and performing iterative computation through a UAMP-SBL algorithm;
step D: c, taking the mean value and the variance of the sparse vector and other parameters obtained by calculation in the step C as return values, and repeating the process in the step C until the circulation is finished;
step E: d, further processing the estimated value obtained in the step D to obtain estimated perception parameters, wherein the perception parameters at least comprise delay and Doppler;
we consider the scenario where one BS serves K UEs. In the downlinkAnd broadcasting public information to K UEs in the signal coverage range by the BS, and sensing the position information of the UEs based on the received echoes. Provided with N BS There are P independent separable paths between the BS of the root antenna and each single antenna UE, then the radar return signal can be expressed as:
wherein
Is a radar echo signal in the Time Delay Angle (TDA) domain, +>
Is N for spatially expanding a signal
BS ×N
BS Is a Discrete Fourier Transform (DFT) matrix of (a),
is the steering vector, θ, of the antenna array
i,p Is the relative angle (.)
T and (·)
H The transpose and Hermite transpose are represented respectively. Alpha is N for power distribution of signals on each antenna
BS ×N
BS A dimension matrix.
MN x MN dimensional permutation matrix representing relative delay effects, wherein
A diagonal matrix of MN x MN representing the effect of relative doppler shift, wherein,
m and N are denoted as the number of subcarriers and the number of slots respectively,
and
The p-th path related round trip delay index and doppler shift index of the i-th UE,
wherein τ
i,p and v
i,p The p-th path related relative delay and relative doppler shift for the i-th UE are respectively, Δf and T are the subcarrier spacing and the slot duration, Δf=1/T. The precoding matrix P multiplexes the signals onto each antenna. X is x
TD Is a transmitted symbol vector in the delay-doppler (DD) domain.
Is an Additive White Gaussian Noise (AWGN) column vector.
Assuming that the relative angle of the BS and UE is known or an estimate is available, the estimated parameters of the round trip delay index and the doppler shift index may be estimated using the following methods.
In step a, the transformation of equation (1) can be rewritten as:
wherein
Corresponding to a set of delay and doppler shift indices. We regard this set of values as a column in the high-dimensional matrix Φ, to ensure accuracy of the estimation, as much as possible to ensure that Φ contains all possible valuesDelay and doppler combinations can occur. The round trip delay index is selected to be +.>
The Doppler index selection range is +.>
For the perceptual matrix Φ, h has a non-zero value h in the corresponding row
i,p Otherwise, zero is set, so that a sparse vector is formed. Wherein Φ is MNN
BS And (3) a linear matrix of x LM (2N-1), wherein L is the number of separable relative angles. For convenience of presentation we let Φ be +.>
A dimension matrix. The perceptual parameters are then inferred by estimating the locations of non-zero values in the sparse vector h.
In step B, Φ is subjected to SVD decomposition Φ=uΛv
H And unitary transforming equation (5), i.e
Can obtain
wherein ,
and
Omega is 0 as mean and beta as covariance matrix
-1 I is gaussian noise, β is the accuracy of the noise.
In step C, the iterative process of information in the UAMP-SBL algorithm can be summarized as the following six steps:
step C1: initializing and setting basic parameters: let λ= ΛΛ
H 1 (1 is a column vector with one element all 1),
(0) =0.01,
s=0 (0 is a column vector with one element all being 0) and t=0.
Step C2: calculating τ p and p
Where·represents the dot product of two vectors.
Step C3, calculating v
z ,
and
Where/represents two vector dot divisions.
Step C4: calculating τ s and s
s=τ s ·(r-p) (51)
Step C5: calculating τ q and q
Step C6: calculating the mean of sparse vectors
Variance τ
h Parameter->
And
in step D, the updated basic parameters, including the mean and variance of the estimated value of the sparse vector h, are returned to step C2 for the next iteration.
In step E, the estimated sparse vector h is subjected to non-zero position identification to obtain a group of delay indexes and doppler shift indexes of the corresponding positions, and then the delay indexes and the doppler shift indexes are converted into relative delay and relative doppler shift through a formula (4), so as to obtain the required perception parameters.
Referring to fig. 2, a performance comparison graph of the method based on the present invention and the recovery of sparse vector h based on the SBL method is shown, wherein m=16, n=8, and the number of antennas N are set in the embodiment of the present invention
BS By adopting the QPSK modulation method, the method of the present invention has a large performance gain compared with the conventional SBL, and is always close to the performance lower bound, while the perceptual matrix ψ of the conventional SBL method is a correlation matrix, which causes iterative divergence to cause serious performance degradation. In terms of computational complexity, the complexity of the method of the present invention in each iteration is
Whereas the traditional SBL approach is +.>
Referring to fig. 3, a comparison of the estimated index of the perceptual parameter with the actual index is shown, from which it can be seen that the estimated index and the actual index are very matched, demonstrating the effectiveness of the method of the present invention.
In summary, in the ISAC wireless communication downlink based on SS-OTFS, the embodiments of the present invention can utilize echo signals to perform effective perceptual parameter estimation. Compared with the existing SBL algorithm, the method has higher estimation precision of the perception parameters and lower calculation complexity.
The last explanation is: the foregoing is merely a preferred embodiment of the present invention, and the present invention is not limited to the embodiments shown herein. Modifications, substitutions, etc. may be made by one skilled in the art in light of the foregoing description and such modifications and substitutions are intended to be included within the scope of the present invention.