CN113794658A

CN113794658A - Real-time calibration method and device for joint time-varying channel tracking and phase shifter network

Info

Publication number: CN113794658A
Application number: CN202110900489.8A
Authority: CN
Inventors: 周世东; 刘羽; 马赫
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-08-06
Filing date: 2021-08-06
Publication date: 2021-12-14

Abstract

The invention relates to a real-time calibration method and a real-time calibration device for a joint time-varying channel tracking and phase shifter network, and belongs to the technical field of millimeter wave mobile communication. The method comprises the following steps: in the detection stage of each detection communication period, detecting orthogonal pilot frequency sequences sent by each user equipment for multiple times by configuring a phase shifter network to obtain a current observation result; obtaining an estimated value of a channel matrix and an estimated value of a phase shift deviation matrix by using the current observation result and the historical observation result; and calibrating the phase shifter network according to the estimated value of the phase shift deviation matrix at the communication stage of each detection communication period, and realizing data transmission by adopting a preset hybrid precoding scheme based on the estimated value of the channel matrix. The method and the device can realize higher calibration precision and spectral efficiency on the premise of not introducing hardware overhead and detection overhead except channel estimation.

Description

Real-time calibration method and device for joint time-varying channel tracking and phase shifter network

Technical Field

The disclosure belongs to the technical field of millimeter wave mobile communication, and particularly relates to a method and a device for calibrating a joint time-varying channel tracking and phase shifter network in real time.

Background

By virtue of the huge bandwidth advantage, the millimeter wave has wide application scenes in high-speed mobile communication. To compensate for the large path loss during propagation, millimeter wave systems are often equipped with large-scale antennas to achieve relatively high array gain, which results in very narrow beams being formed, and slight misalignment can result in large performance losses. Under the quasi-static scene that the channel approximation remains unchanged, a large amount of detection overhead can be adopted to realize effective alignment by means of beam training. However, in a user high-mobility scenario such as a high-speed rail, a drone, etc., the rapid change of the channel makes it difficult to effectively apply the beam training mode with huge detection overhead. Therefore, performing accurate beam tracking in a high mobility scenario is an important issue in millimeter wave communication.

At present, a plurality of millimeter wave channel tracking algorithms in high-mobility scenes exist, and the algorithms can obtain good performance under certain conditions. However, the existing tracking algorithms are based on ideal phase shifters. In practical systems, the phase shifter network often introduces random amplitude and phase offsets due to factors such as design errors, integrated circuit characteristics, and antenna feed. In addition, the amplitude and phase deviation of the phase shifter may vary over time due to device aging or ambient temperature changes. The non-idealities of the phase shifters can cause significant impairment of the side lobes of the pattern, and if not effectively calibrated, the mutual interference between multiple users can be very severe, resulting in degraded communication performance.

For the problem of amplitude and phase deviation of a phase shifter network, some calibration algorithms exist at present, and typical methods include an algorithm based on unimodular quadratic programming and an algorithm for real-time calibration. Although the algorithm based on unimodular quadratic programming can obtain good performance under certain conditions, the algorithm is only designed for static channels and time-invariant phase-shifting deviation, and huge detection overhead is brought under the conditions of time-variant channels and time-variant phase-shifting deviation. The real-time calibration algorithm introduces additional hardware overhead such as a bandpass filter and occupies additional in-band resources.

Disclosure of Invention

The present disclosure is directed to overcoming the above-mentioned disadvantages of the prior art and providing a method and apparatus for calibrating a joint time-varying channel tracking and phase shifter network in real time. The method and the device can realize higher calibration precision and spectral efficiency on the premise of not introducing extra hardware overhead and detection overhead.

An embodiment of the first aspect of the present disclosure provides a method for calibrating a joint time-varying channel tracking and phase shifter network in real time, including:

in the detection stage of each detection communication period, detecting orthogonal pilot frequency sequences sent by each user equipment for multiple times by configuring a phase shifter network to obtain a current observation result;

obtaining an estimated value of a channel matrix and an estimated value of a phase shift deviation matrix by using the current observation result and the historical observation result;

and calibrating the phase shifter network according to the estimated value of the phase shift deviation matrix at the communication stage of each detection communication period, and realizing data transmission by adopting a preset hybrid precoding scheme based on the estimated value of the channel matrix.

In one embodiment of the present disclosure, the method further comprises: and respectively acquiring initial estimated values of the channel matrix and the phase shift deviation matrix before the beginning of the first detection communication period.

In an embodiment of the present disclosure, in the detection phase of each detection communication period, the detecting, by configuring the phase shifter network, the orthogonal pilot sequences sent by the user equipments for multiple times to obtain the current observation result includes:

and at each detection, configuring the phase shifter network to obtain a detection beam forming matrix to receive the orthogonal pilot frequency sequence sent by each user equipment, wherein the detection beam forming matrix is composed of a plurality of detection beam forming vectors.

In an embodiment of the disclosure, the obtaining an estimated value of a channel matrix and an estimated value of a phase shift deviation matrix by using the current observation result and the historical observation result includes:

updating the channel matrix estimated value by utilizing the current estimated value of the phase shift deviation matrix through iteration according to the current observed result and the historical observed result; and updating the estimated value of the phase shift deviation matrix by using the current estimated value of the channel matrix until reaching the upper limit of the set iteration times.

In an embodiment of the present disclosure, the preset hybrid precoding scheme employs a regularized channel diagonalization precoding method.

In an embodiment of the disclosure, the updating the channel matrix estimation value by using the current estimation value of the phase shift deviation matrix includes:

updating the estimated value of the beam direction of each user equipment by adopting a random Newton method;

obtaining an estimated value of the channel gain of each user equipment by using the estimated value of the beam direction of each user equipment;

and obtaining the estimated value of the channel vector of each user equipment according to the estimated value of the beam direction and the estimated value of the channel gain of each user equipment so as to update the estimated value of the channel matrix.

In an embodiment of the disclosure, the updating the estimated value of the phase shift deviation matrix by using the current estimated value of the channel matrix includes:

and obtaining the estimated values of the amplitude and the phase deviation of the phase shifter by adopting an extended Kalman filtering algorithm and utilizing the current estimated value of the channel matrix so as to update the estimated value of the phase-shifting deviation matrix.

An embodiment of a second aspect of the present disclosure provides a joint time-varying channel tracking and phase shifter network real-time calibration apparatus, including:

the detection module is used for detecting the orthogonal pilot frequency sequence sent by each user equipment for multiple times by configuring a phase shifter network to obtain a current observation result in the detection stage of each detection communication period;

the channel matrix and phase shift deviation matrix estimation module is used for obtaining an estimation value of the channel matrix and an estimation value of the phase shift deviation matrix by utilizing the current observation result and the historical observation result;

and the communication module is used for calibrating the phase shifter network according to the estimated value of the phase shift deviation matrix in the communication stage of each detection communication period, and realizing data transmission by adopting a preset hybrid precoding scheme based on the estimated value of the channel matrix.

An embodiment of a third aspect of the present disclosure provides an electronic device, including:

at least one processor; and a memory communicatively coupled to the at least one processor;

wherein the memory stores instructions executable by the at least one processor and configured to perform a joint time-varying channel tracking and phase shifter network real-time calibration method as described above.

A fourth aspect of the present disclosure is directed to a computer-readable storage medium storing computer instructions for causing a computer to perform a method for real-time calibration of a joint time-varying channel tracking and phase shifter network as described above.

The characteristics and the beneficial effects of the present disclosure are:

(1) the detection overhead required for channel tracking is only utilized to complete the real-time calibration of the joint channel tracking and phase shifter network, and no additional hardware overhead is introduced.

(2) By iteratively estimating the channel matrix and the phase shift deviation matrix, the method and the device can achieve higher calibration precision and spectral efficiency.

Drawings

Fig. 1 is a diagram of a fully-connected hybrid beamforming architecture based on a two-dimensional antenna array in an exemplary embodiment of the present disclosure.

Fig. 2 is a schematic diagram of a probe communication cycle in an embodiment of the present disclosure.

Fig. 3 is an overall flowchart of a method for real-time calibration of a joint time-varying channel tracking and phase shifter network according to an embodiment of the present disclosure.

Fig. 4 is a simulation plot of calibration accuracy as a function of signal-to-noise ratio in a specific embodiment of the present disclosure.

Fig. 5 is a graph of a simulation of spectral efficiency as a function of signal to noise ratio in a specific embodiment of the present disclosure.

Fig. 6 is a simulation plot of spectral efficiency as a function of the number of quantized bits in an exemplary embodiment of the present disclosure.

Detailed Description

Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of illustrating the present disclosure and should not be construed as limiting the same.

In a specific embodiment of the present disclosure, a Time Division Duplex (TDD) full-connection hybrid beamforming architecture as shown in fig. 1 is considered, where the number of base station side configuration arrays is N ═ N_x×N_zOf a two-dimensional planar antenna array, N_xNumber of elements in x-axis, N_yThe number of the arrays in the y axis and the spacing between the arrays in the x axis direction are d_xThe spacing of the arrays in the z-axis direction is d_zAt the base station, N is total_RF(N_RFLess than or equal to N) Radio Frequency (RF) links, NxN_RFAnd the phase shifters serve K single-antenna users. Data s to be sent to the respective users₁,…s_K(wherein s_kFor data sent to the kth user) are sequentially subjected to digital precoding (the corresponding digital precoding matrix is W)_BB) And analog precoding (corresponding analog precoding matrix is W)_RF) And finally, loading the data to the base station antenna end and transmitting the data to the corresponding K users.

The embodiment of the first aspect of the present disclosure provides a method for calibrating a joint time-varying channel tracking and phase shifter network in real time, which alternately works at different stages of a sounding communication period as shown in fig. 2. Before entering a sounding and communication cycle (ECC), initial estimates of the channel matrix and the phase shift bias matrix are first obtained using a large number of probes. After the initial estimation is completed, a mode of alternately performing detection and communication is entered. In this embodiment, the channel and phase shifter offsets are in one probeThe channel and phase shifter skew may be different between different ECCs, keeping the same during the communication period. In the detection phase of each ECC (including a detection phase and a communication phase), K users simultaneously transmit a known length L through an uplink channel_sOrthogonal pilot sequence of

Wherein, each user sends the corresponding orthogonal pilot frequency sequence q times s_p,kRepresents the orthogonal pilot sequence transmitted by the k-th user. The base station receives q times in total, and different detection beam forming matrixes are adopted to receive orthogonal pilot sequences sent by K users each time. And after the q-th detection is finished, the base station estimates an uplink channel matrix and a phase shift deviation matrix based on the received signal of the current ECC and the received signal of the historical ECC. In this embodiment, assuming that the reciprocity of the uplink and downlink channels of the TDD system is perfectly calibrated, the reciprocity can be used to obtain an estimate of the downlink channel. In each ECC communication stage, the base station calibrates based on the estimated phase shift deviation matrix, and designs a hybrid precoding scheme by using the estimated downlink channel matrix to realize efficient data transmission.

Furthermore, during each detection, the phase shifter connected to each radio frequency link may be configured, and after the phase shifter connected to each radio frequency link is configured once, a sounding beam forming vector may be obtained, and the sounding beam forming vectors may be in the form of a steering vector, and may be quantized.

It should be noted that the millimeter wave scattering effect is weak, and only one direct path and a small number of reflected paths exist in the channel. Since the angular spread is small, the mutual interference between multipaths is rather weak. Therefore, each of the multipaths can be tracked independently, and the present embodiment focuses on a tracking method for one path, and other multipaths can be tracked by the same method. At the mth ECC, the path of the kth user to be studied reaches the beam direction (θ)_m,k,φ_m,k) Wherein theta_m,kFor depression in the direction of the arriving beamElevation angle phi_m,kIs the azimuth of the direction of the arriving beam. The channel vector for this path can be expressed as follows:

h_m,k＝β_m,ka(x_m,k), (1)

wherein beta is_m,kThe complex channel gain for the k user for m ECCs,

is composed of (theta)_m,k,φ_m,k) Determined Direction Parameter Vector (DPV), a (x)_m,k) For the 2D steering vector:

wherein subscripts x and z represent an x-axis direction and a z-axis direction, respectively,

superscripts

1 and 2 represent two dimensions of the DPV, respectively,

is represented by N_tFor variable x of a parameter_tThe 1D steering vector of (1) is defined by:

λ is the wavelength of the millimeter wave,

representing the kronecker product.

In order to receive the pilot sequence transmitted through the millimeter wave channel, the base station needs to determine nxn_RFThe phase shift values to configure the phase shifter network. The r (r is more than or equal to 1 and less than or equal to N) of the base station configuration_RF) The gain of the nth (1. ltoreq. N. ltoreq.N) phase shifter connected to each RF link is recorded as

However, the non-idealities of the device lead toDeviation of, actual gain of the phase shifter

And

there is a certain difference, given by:

wherein

Represents the total phase shift deviation as a whole,

representing the amplitude deviation of the phase shifter,

representing the phase deviation of the phase shifter, the amplitude and phase deviations of the different phase shifters are modeled as independent and identically distributed, and independent of the phase shifting configuration, but varying with time.

According to the investigation results, there is currently no accurate time-varying model for the phase shifter network bias. Observing the actual measurement results, the amplitude deviation of the phase shifter can be found

And phase deviation

Are all continuously randomly varied over time. Since the first order gaussian-markov process also has the characteristic of continuously and randomly changing with time, the first order gaussian-markov process is adopted in the embodiment to characterize the time-varying deviations, and the first order gaussian-markov process is used as a preliminary attempt to solve the millimeter wave channel tracking problem in the presence of the time-varying phase shifter deviation. The phase shifter bias time-varying model is given by:

where ρ is_ι,ρ_ξTime-varying coefficients representing adjacent ECC amplitude and phase deviations respectively,

representing the variance of the amplitude deviation and the phase deviation, respectively, under steady state conditions. In the present embodiment, the time-varying characteristics of the amplitude and phase deviations are independent of each other.

In the sounding phase, each user employs orthogonal pilot sequences, i.e.

Wherein

Is a pilot matrix, J_nRepresents an n-dimensional unit array and is,

representing the energy of each pilot sequence. At the detection of the ith (i ═ 1, …, q) time of the mth ECC, the base station uses a passive analog beam forming matrix

(also referred to as a sounding beamforming matrix in this embodiment) receives a pilot sequence in which

The analog beamforming vector corresponding to the phase shifter connected for the r-th RF link (also referred to herein as the probe beamforming vector),

have the same amplitude

The mth ECC inner phase shift deviation matrix is noted as gamma_mWherein

Representing the phase shifted offset vector corresponding to the r-th RF chain. After analog beamforming, the sequence received at the RF link entrance is:

wherein

An independent identically distributed gaussian noise matrix introduced at the RF link entrance for the ith ECC sounding,

a channel matrix representing the mth ECC,

representing the hadamard product.

Using pilot sequences s_p,kTo the receiving matrix

Performing matched filtering, the observation vector received after the ith probe for the kth user is given by:

wherein

The additive gaussian noise vector introduced for the kth user at the ith detection of the mth ECC. Thus, after each probing, N is available for each user_RFAnd (4) obtaining a plurality of observed values.

After q probing times, let

And

representing the total probe beamforming matrix employed by the mth ECC, the total introduced phase shift bias matrix, the total observation vector for the kth user, and the total noise vector for the kth user, respectively, equation (7) may be rearranged as follows:

at present, many precise millimeter wave channel estimation algorithms and phase shift offset estimation algorithms exist, so that in the initial channel estimation stage in fig. 3, a more precise initial estimation value of the channel matrix can be obtained

Sum phase shift offset matrix estimation

The tracking process proceeds from these initial estimates to obtain more accurate time-varying channel estimates and phase-shifted offset estimates to serve calibration and multi-user communications.

Let Y_m＝[y_m,1,…,y_m,K]And Z_m＝[z_m,1,…,z_m,K]Respectively representing the observation matrix and the noise matrix of the mth ECC. In the probing phase of the mth ECC, the base station needs history-based observation Y₁,…,Y_m-1And corresponding probe beamforming matrix W₁,…,W_m-1Determining a new probe beamforming matrix W_mBy using the probe beam forming matrix, the method can obtainA new observation matrix Y_m. And then based on all currently available observations Y₁,…,Y_mAnd corresponding probe beamforming matrix W₁,…,W_mObtaining a channel matrix H_mEvaluation of

And a phase shift deviation matrix gamma_mEvaluation of

A specific embodiment of the present disclosure provides a joint time-varying channel tracking and phase shifter network real-time calibration algorithm, an overall flow is shown in fig. 3, and the method includes the following steps:

1) setting the total number M of the ECC of the detection communication periods and the upper limit N of the iteration number in each detection communication period_it；

2) Initial channel estimation, namely obtaining an initial estimation value of a channel matrix and an initial estimation value of a phase shift deviation matrix;

3) setting a detection communication cycle number m to be 1;

4) and (3) judging m: if M is less than or equal to M, making M equal to M +1, and then entering step 5);

if M is larger than M, finishing the calibration;

5) setting the number of iterations n in the mth ECC_itIs 1;

6) to n_itAnd (4) judging: if n is_it≤N_itEntering step 7); otherwise, obtaining the estimated results of the phase shift deviation matrix and the channel matrix of the mth ECC, and then entering step 11);

7) detecting in the detection phase of the mth ECC; the specific method comprises the following steps:

in order to ensure that the system supports as many user communications as possible, K ═ N is used here_RFDesigning the detection direction, and performing detection for q-3 times in each detection stage in the ECC.

The ith detection direction for the kth user is designed as follows:

wherein

Representing the mth ECC, for the ith detection offset of the kth user, by a fixed detection offset Δ_sRotate

Obtaining:

wherein Δ_s＝[0.52,0]^TRotation angle of the i-th detection offset in the m-th ECC

Is arranged as

The resulting probe beamforming matrix for the mth ECC is given by:

after the matched filtering, the observation vector of the kth user can be obtained by equation (8):

wherein,

represents the product of the Hadamard and the Hadamard,

represents eachThe energy of the individual pilot sequences is,

the total phase shift error matrix, γ introduced for the mth ECC_mFor the mth ECC inner phase shift deviation matrix, h_m,kFor the channel vector of the kth user in the mth ECC,

for the total noise vector of the kth user in the mth ECC,

for the additive Gaussian noise vector, W, introduced for the kth user at the ith detection of the mth ECC_mA probe beamforming matrix for the mth ECC.

When K is less than N_RFSince each ECC inner base station can detect qN_RFIn one direction, mqN of the first m ECCs in the m-th ECC_RFThe detection direction will be according to

In which

Is given by formula (9).

8) Tracking of time-varying channels

The embodiment of the present disclosure adopts a random newton method, and the update method of the beam direction estimation of the k-th user can be obtained as follows:

wherein b is_mIn order to track the step size,

the vector is updated for the direction. The update vector is an observation vector y_m,kAnd beam direction latest estimate

Is defined as follows:

wherein

For a matrix of snow information, mu_m,kFor the gradient function in the presence of dephasing offset, the two are calculated as follows:

wherein p is 1, 2; the number of s is 1,2,

gain beta for k user channel_m,kVariance of f_m,k,

And

given by:

wherein

Is the mth ECC to the total phase shift deviation matrix gamma_q,mThe latest estimate of (c).

Tracking-based DPV

An estimate of the channel gain for the kth user in the mth ECC can be obtained using a Minimum mean square error estimation (MMSE) algorithm

Wherein

The definition is as follows:

incorporating estimated DPV

Sum channel gain

The estimate of the channel vector for the kth user in the mth ECC can be obtained as follows:

9) tracking of phase-shift deviation matrices

Order to

Indicating the phase-shifted offset state vector corresponding to the r-th RF link at the m-th ECC. According to equation (5), the state update equation is given by:

wherein

The matrix is updated for the state of the device,

next consider the observation equation for the deviant state vector. According to formula (8) and definition Y_m＝[y_m,1,…,y_m,K],Z_m＝[z_m,1,…,z_m,K]The matrix Y can be found_mAnd Z_m(i-1) N_RFRow + r) shows the observed values and corresponding observed noise that can be obtained through the r-th RF link when the m-th ECC performs the i-th probing, respectively. Therefore, when the m-th ECC performs the i-th probing, the observation vector obtained through the r-th RF link is as follows:

wherein (·)^*It is meant a conjugate operation of the two,

is the received noise vector of the r-th RF chain at the i-th probe. Definition of

And

for the total observed vector and the total noise vector obtained by the mth ECC through the mth RF link, respectively, equation (21) may be rearranged as follows:

wherein

For the measurement matrix of the phase shift deviation state vector for the r-th RF link, the following is defined:

next, the observation equation is further characterized. For a general deviant state vector

The function b (ζ) is defined as follows:

wherein

In the form of a vector of magnitude deviations,

b (ζ) is the complex phase shift deviation vector generated by the magnitude deviation vector ι and the phase deviation vector ξ. According to the formula (24), a

At this time, equation (22) can be rearranged as:

the core goal here is to estimate the phase shift deviation vector from the linear state update equation in equation (20) and the non-linear observation equation in equation (25)

The extended kalman filter algorithm is an effective way to solve such problems, and the iterative process of the problem is given by the following formula:

wherein

Obtained in an initialization phase, T₀＝0，

The gradient function for the noiseless measurement equation is given by:

in the formulae (28) and (31)

The calculation of (2) requires a measurement matrix

According to equation (23), the measurement matrix is in turn dependent on the channel matrix H_m. During the actual tracking process, by using the latest channel matrix to estimate

Instead of H in the formula (23)_mEvaluation of the available measurement matrix

By using

Instead of in formula (31)

The calculation can be performed.

Obtaining an estimate of the deviation state vector by an extended Kalman filtering algorithm

Thereafter, it can be obtained according to the formula (24)

I.e. an estimate of the phase shift offset vector:

the latest estimation value of the mth ECC channel matrix needs to be obtained in the tracking process of the phase shift deviation matrix

While performing channel tracking, the calculation of equation (16) requires the use of the most recent estimate of the phase-shifted offset matrix. Therefore, at the mth ECC, time-varying channel tracking and phase shift deviation matrix tracking can be performed iteratively for a plurality of times to reduce the channel estimation error and the estimation error of the phase shift deviation matrix.

10) Updating n_it＝n_it+1, then return to step 6);

11) according to the estimated results of the phase shift deviation matrix and the channel matrix of the mth ECC, calibration can be performed based on the estimated value of the phase shift deviation matrix, then, the obtained estimated value of the channel matrix is reused, a designed hybrid precoding scheme (in some embodiments of the present disclosure, a regularized channel diagonalization precoding method is used) is adopted to realize data transmission in the mth ECC, then, m is made to be m +1, and the step 4 is returned again.

Simulation performance evaluation

In one embodiment of the present disclosure, in terms of channel tracking, all comparison algorithms use recursive beam tracking algorithm, and these comparison algorithms are different in terms of phase shifter network calibration, and there are three ways:

i) only channel tracking is performed and the phase shifter network is not calibrated.

ii) estimating the phase shift deviation matrix at the initial time by using MMSE algorithm.

iii) estimating the phase shift deviation matrix by adopting a unimodular quadratic programming algorithm at the initial moment.

The latter two comparison algorithms estimate the phase shift deviation only in the initialization stage, and the phase shift deviation is considered to remain unchanged in the subsequent tracking process, and no other algorithm for dynamically tracking the time-varying phase shift deviation exists in the existing documents.

Based on the channel model in this embodiment, the basic parameters are set as follows: number of antenna elements N_x＝N_z8, antenna element spacing

Number of RF links N_RF16, the number of users K16. Pilot sequence length L_sK, transmission signal-to-noise ratio

Varying from-10 dB to 30dB, step size is set to b_m＝0.7。

The correlation coefficient of the amplitude and phase deviation vector in equation (5) is set to ρ_ι＝ρ_ξρ is 0.99. As for the steady state variance of the amplitude and phase deviations of the phase shifters, the root mean square of the amplitude deviation is less than 0.1 and the root mean square of the phase deviation is less than 0.1rad in the prior art phase shifters. Therefore, δ is set here in the simulation_ι,DV＝0.1,δ_ξ,DV＝0.1rad。

Initial AoA (θ) of each user_0,k,φ_0,k) In that

φ_0,kIs uniformly and randomly selected within the range of epsilon [0, pi). AoA (θ)_m,k,φ_m,k) Is modeled as a random walk with foldback, i.e. with random walk

The angular velocity parameter is set to delta_θ,AV＝δ_φ,AV＝δ_AV＝0.01rad/ECC；

Indicating the direction of rotation, with a value ensuring theta_m,kIn that

φ_m,kIn [0, pi ]]Is changed. Channel gain β in equation (1)_m,kModeled as rice fading with rice factor k 15dB, and β for different users, different ECCs_m,kIndependently and equally distributed.

In the initial channel estimation phase shown in fig. 3, scanning is performed with N Orthogonal beams, first using Orthogonal Matching Pursuit (OMP) algorithm and MMSE algorithm. Obtaining initial DPV estimation of each user

And initial channel gain estimation

Then, based on the estimated initial channel, the MMSE algorithm or the unimodular quadratic programming algorithm is adopted to obtain the initial estimation value of the phase-shifting deviation matrix

In each ECC communication stage, initial estimation is performed by using a phase-shift deviation matrix

And calibrating, and then performing data transmission by adopting a regular channel diagonalization hybrid precoding scheme on the basis of the estimated channel matrix.

The tracking process lasts 1000 ECCs each time the system is implemented, and the final presented result is obtained after 100 averaging.

Firstly, determining the iteration number N required by the designed combined time-varying channel tracking and phase shifter network real-time calibration method_it. FIG. 4 shows the calibration error versus Signal-to-noise ratio (SNR) for different algorithms, where the two lowest lines represent the values of N _it1 and N _it2 is the calibration error achieved by the present invention. It can be seen that the two are close in height. Thus, the method of the present invention has converged by 1 iteration. Setting N in subsequent simulations_it＝1。

As shown in fig. 4, compared with the existing algorithm, the proposed combined channel tracking and phase shift offset real-time calibration algorithm can achieve higher calibration accuracy, which indicates the necessity and superiority of jointly tracking time-varying channel and time-varying phase shifter offset.

Fig. 5 shows the spectral efficiency of different algorithms as a function of SNR. It can be seen that in the presence of time varying phase shift deviations, there is a significant loss of spectral efficiency if not calibrated or calibrated only during the initialization phase. If the algorithm provided by the invention is adopted, the loss of most of frequency spectrum efficiency can be effectively compensated.

Next, the influence of quantization accuracy of the phase shifter is evaluated, and a Q-bit uniformly quantized phase shifter network is considered, and the phase shift value is selected from the following set:

order to

Representing unquantized phase shift values configured by the nth phase shifter connected on the r RF link at the m ECC, and then quantized phase shift values

Given by:

the phase shift values of all the configurations in the detection stage and the communication stage are quantized according to the formula so as to evaluate the performance of the algorithm under the quantization phase shifter. Fig. 6 shows the spectral efficiency of the proposed algorithm as a function of the number of quantization bits Q at a given SNR of 20 dB. It can be seen that when the quantization accuracy is not less than 4 bits, the spectral efficiency achieved by using the quantized phase shifter and the non-quantized phase shifter is already highly close. Therefore, in an actual system, the tracking and the efficient data transmission of a time-varying channel under the condition of time-varying phase-shifting deviation can be realized by adopting 4-bit phase shifter quantization.

In order to implement the foregoing embodiments, an embodiment of a second aspect of the present disclosure provides a joint time-varying channel tracking and phase shifter network real-time calibration apparatus, including:

To achieve the above embodiments, an embodiment of a third aspect of the present disclosure provides an electronic device, including:

To achieve the foregoing embodiments, a fourth aspect of the present disclosure provides a computer-readable storage medium storing computer instructions for causing a computer to execute the foregoing method for real-time calibration of a joint time-varying channel tracking and phase shifter network.

It should be noted that the computer readable medium in the present disclosure can be a computer readable signal medium or a computer readable storage medium or any combination of the two. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples of the computer readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present disclosure, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. In contrast, in the present disclosure, a computer readable signal medium may comprise a propagated data signal with computer readable program code embodied therein, either in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: electrical wires, optical cables, RF (radio frequency), etc., or any suitable combination of the foregoing.

The computer readable medium may be embodied in the electronic device; or may exist separately without being assembled into the electronic device. The computer readable medium carries one or more programs which, when executed by the electronic device, cause the electronic device to perform a method of joint time-varying channel tracking and phase shifter network real-time calibration of the above embodiments.

Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C + +, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).

In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., 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 application. 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 and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and the scope of the preferred embodiments of the present application includes other implementations in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.

The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.

It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, and the program may be stored in a computer readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a separate product, may also be stored in a computer readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc. Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.

Claims

1. A real-time calibration method for a joint time-varying channel tracking and phase shifter network is characterized by comprising the following steps:

2. The method of claim 1, further comprising: and respectively acquiring initial estimated values of the channel matrix and the phase shift deviation matrix before the beginning of the first detection communication period.

3. The method of claim 1, wherein the detecting the orthogonal pilot sequences transmitted by the user equipments multiple times by configuring the phase shifter network in the detection phase of each detection communication period to obtain the current observation comprises:

4. The method of claim 1, wherein using the current observations and historical observations to obtain an estimate of a channel matrix and an estimate of a phase shift bias matrix comprises:

5. The method of claim 1, wherein the preset hybrid precoding scheme employs a regularized channel diagonalization precoding method.

6. The method of claim 4, wherein said updating the channel matrix estimate using the current estimate of the phase shift bias matrix comprises:

7. The method of claim 4, wherein said updating the estimated value of the phase shift bias matrix using the current estimated value of the channel matrix comprises:

8. A joint time-varying channel tracking and phase shifter network real-time calibration apparatus, comprising:

9. An electronic device, comprising:

wherein the memory stores instructions executable by the at least one processor, the instructions being arranged to perform the method of any of the preceding claims 1-7.

10. A computer-readable storage medium storing computer instructions for causing a computer to perform the method of any one of claims 1-7.