Frequency Offset Estimation Method, Device, Equipment and Medium for Uplink Channel in MU-MIMO Mode

Abstract

The present application discloses a frequency offset estimation method, apparatus, device and medium for an uplink channel in MU-MIMO mode, which relates to the field of wireless communication technology and is applied to the base station side. The method includes: obtaining the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and using a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station; determining the weighting coefficients of different antennas in the antenna array based on the angle information, and using the weighting coefficients to perform weighted summation on the received signals to obtain the cumulative signal of the terminal corresponding to the angle information; using a preset channel estimation algorithm to determine the channel estimation values corresponding to each of the multiple terminals, and using the channel estimation values to determine the respective frequency offset information of the multiple terminals relative to the base station. Through the technical solution of the present application, it is possible to effectively reduce the interference between terminals, so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with multi-symbol pilot resource reuse.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly relates to a method, apparatus, device and medium for estimating frequency offset of an uplink channel in a MU-MIMO mode. Background Art

[0002] In a 5G (5th Generation) wireless communication system, the prerequisite for a terminal and a base station to establish a communication link is time and frequency synchronization. In terms of frequency synchronization, usually the base station sends a synchronization sequence, and the terminal receiver estimates the frequency deviation through the received sequence, that is, Carrier Frequency Offset (CFO) estimation, and then compensates the frequency offset of both the transmitted and received signals of the terminal simultaneously to make the terminal and the base station have the same frequency. Usually, the remaining frequency deviation after compensation is very small, and when the system requirements are not high, the impact is not significant; however, for a high-order modulation system, especially an Orthogonal Frequency Division Multiplexing (OFDM) system, it has strict requirements on the orthogonality between subcarriers. Frequency offset will destroy the orthogonality between subcarriers and affect the correct demodulation at the receiving end. A small frequency offset can also have a great impact on the demodulated signal, resulting in demodulation failure and thus serious degradation of the system performance. Therefore, when the base station receives the uplink signal from the terminal, it is necessary to estimate the remaining frequency offset of the terminal relative to the base station, and then perform operations such as data demodulation after compensation, which can greatly reduce the bit error rate of the uplink channel data and thus improve the performance of the communication system.

[0003] In frequency offset estimation, the frequency offset can be estimated according to the phase deviation on different symbols of multi-symbol dm-rs (demodulation reference signal). However, in the MU-MIMO (Multi-User Multiple-Input Multiple-Output) mode, if the dm-rs of different terminals are multiplexed on the same time-frequency resource, due to the existence of inter-terminal interference, it cannot be simply and directly estimated at the base station receiving side. If the multiplexed dm-rs is to be used to estimate the frequency offset, the interference between different terminals needs to be eliminated first, and then the frequency offset estimation is performed on different terminals respectively. Existing frequency offset estimation methods are mainly divided into non-data-aided frequency offset estimation methods and data-aided frequency offset estimation methods. The non-data-aided frequency offset estimation method does not require additional resources, but the estimation accuracy and range are limited, such as the technology of using the cyclic prefix (CP) for frequency offset estimation in the time domain. In the data-aided frequency offset estimation scheme, some use pilots for frequency offset estimation. For example, in LTE, the phase difference between two columns of pilots in a subframe of the physical uplink shared channel (PUSCH) is used for frequency offset estimation; some use the synchronization signal (SSS, PSS) or the phase tracking reference signal (PT-RS) for frequency offset estimation; there are also methods that jointly estimate using multiple reference signals.

[0004] For these above-mentioned schemes, there is an important application scenario that they cannot be applied to: that is, when the reference signal or the cyclic prefix is the multiplexed superposition of signals of multiple terminals (such as in the MU-MIMO mode), due to the mutual interference between multiple terminals in the signal received by the base station, these frequency offset estimation methods will no longer be effective, resulting in frequency compensation failure and reducing the system performance. In the case of the uplink channel in the MU-MIMO mode, if the dm-rs of different terminals' PUSCH are multiplexed on the same time-frequency resource through different ports, then there is inter-terminal interference, and the base station receiving side cannot directly calculate the frequency offset of different terminals relative to the base station through the dm-rs. If the common frequency offset estimation method is to be used, it is necessary to allocate the dm-rs of different terminals to different time-frequency resources, thus reducing the resource utilization rate of the OFDM symbol.

[0005] It can be seen that how to effectively reduce the inter-terminal interference so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with the multiplexing of multi-symbol pilot resources is a problem to be solved currently. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a frequency offset estimation method, device, equipment and medium for the uplink channel in the MU-MIMO mode, which can effectively reduce the interference between terminals, so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with multi-symbol pilot resource reuse. The specific scheme is as follows:

[0007] In a first aspect, the present application discloses a frequency offset estimation method for the uplink channel in the MU-MIMO mode, which is applied to the base station side and includes:

[0008] Obtain the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and use a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station;

[0009] Determine the weighting coefficients of different antennas in the antenna array based on the angle information, and use the weighting coefficients to perform weighted summation on the received signals to obtain the cumulative signal of the terminal corresponding to the angle information;

[0010] Use a preset channel estimation algorithm to determine the channel estimation values corresponding to each of the multiple terminals for the cumulative signal, and use the channel estimation values to determine the respective frequency offset information of the multiple terminals relative to the base station.

[0011] Optionally, the obtaining the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station includes:

[0012] Obtain the received signal Y m (l, k) superimposed by multiple terminals on multiple symbols and multiple subcarriers in the shared channel in the MU-MIMO mode of the orthogonal frequency division multiplexing system on the same time-frequency resource through the antenna array of the base station;

[0013] Where m is the m-th antenna of the base station, m = [0, 1, 2... M - 1]; l is the l-th time-domain symbol occupied by the received signal, l = [l0, l0 + 1], and the starting symbol is l0; k is the k-th subcarrier, k = [0, 1, 2... K - 1]; X n (l, k) is the transmission signal of the n-th terminal, the l-th time-domain symbol, and the k-th subcarrier, n = [0, 1, 2... N - 1], l = [l0, l0 + 1],

[0014] k = [0, 1, 2... K - 1]; is the transmission channel from the n-th terminal to the m-th antenna, the l-th time-domain symbol, and the k-th subcarrier; w m (l, k) is the receiver noise of the m-th antenna of the base station, the 1st time-domain symbol, and the k-th subcarrier.

[0015] Optionally, obtaining the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and using a preset angle estimation algorithm to determine the respective angle information of the multiple terminals relative to the base station, includes:

[0016] Obtaining the received signals superimposed by multiple terminals corresponding to any one of the multiple subcarriers and any one of the multiple symbols on the same time-frequency resource through the antenna array of the base station, so as to obtain the received vector of the received signals;

[0017] Based on the received vector, using a preset angle estimation algorithm to determine the respective angle information of the multiple terminals relative to the base station.

[0018] Optionally, determining the weighting coefficients of different antennas in the antenna array based on the angle information, includes:

[0019] Based on the angle information, using weight n (m) = exp(-j·π·m·sin(θ n )) to determine the weighting coefficients of different antennas in the antenna array; where, the θ n represents the angle of the nth terminal; m is the mth antenna of the base station, m ∈ [0, 1, 2…M - 1]; j is the imaginary unit.

[0020] Optionally, weighted summing the received signals using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information, includes:

[0021] Using to obtain the cumulative signal of the terminal corresponding to the angle information; where, weight n (m) is the weighting coefficient; Y m (l, k) is the received signal of the mth antenna, the lth symbol, and the kth subcarrier of the base station, m = [0, 1, 2…M - 1], l = [l0, l0 + 1], k = [0, 1, 2…K - 1]

[0022] Optionally, using a preset channel estimation algorithm for the cumulative signal to determine the respective channel estimation values of the multiple terminals, includes:

[0023] Using the least squares channel estimation algorithm for the cumulative signal, through to determine the respective channel estimation values of the multiple terminals; where, X n (l, k) is the transmitted signal on the nth terminal, the lth time-domain symbol, and the kth subcarrier; the superscript H represents conjugate transpose; Y′ n(l, k) is the signal of terminal n after weighted accumulation.

[0024] Optionally, the step of determining the respective frequency offset information of the multiple terminals relative to the base station by using the channel estimation value includes:

[0025] When there is a frequency offset in the system, there is a phase difference in the estimated channel in the time domain; the phase difference satisfies where, -2π·Δf n ·T ofdm_symb is the phase difference;

[0026] Using to determine the respective frequency offset information of the multiple terminals relative to the base station; where, Δf n represents the frequency offset between terminal n and the base station; T ofdm_symb is the duration of the time domain symbol in the orthogonal frequency division multiplexing system; angle(·) represents the operation of finding the angle of a complex number.

[0027] In a second aspect, the present application discloses a frequency offset estimation device for an uplink channel in a MU-MIMO mode, which is applied to the base station side and includes:

[0028] A received signal acquisition module, configured to acquire the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station;

[0029] An angle information determination module, configured to determine the respective angle information of the multiple terminals relative to the base station by using a preset angle estimation algorithm;

[0030] A weighting coefficient determination module, configured to determine the weighting coefficients of different antennas in the antenna array based on the angle information;

[0031] An accumulated signal determination module, configured to perform weighted summation on the received signals by using the weighting coefficients to obtain the accumulated signals of the terminals corresponding to the angle information;

[0032] A frequency offset information determination module, configured to use a preset channel estimation algorithm to determine the respective channel estimation values of the multiple terminals for the accumulated signals, and use the channel estimation values to determine the respective frequency offset information of the multiple terminals relative to the base station.

[0033] In a third aspect, the present application discloses an electronic device, which includes a processor and a memory; wherein, the memory is used to store a computer program, and the computer program is loaded and executed by the processor to implement the frequency offset estimation method for the uplink channel in the MU-MIMO mode as described above.

[0034] Fourthly, the present application discloses a computer-readable storage medium for storing a computer program; wherein when the computer program is executed by a processor, the frequency offset estimation method for the uplink channel in the MU-MIMO mode as described above is implemented.

[0035] In the present application, applied to the base station side, first, the received signals superimposed by multiple terminals on the same time-frequency resource are obtained through the antenna array of the base station, and the angle information corresponding to each of the multiple terminals relative to the base station is determined by using a preset angle estimation algorithm; then, based on the angle information, the weighting coefficients of different antennas in the antenna array are determined, and the received signals are weighted and summed by using the weighting coefficients to obtain the cumulative signals of the terminals corresponding to the angle information; finally, the channel estimation values corresponding to each of the multiple terminals are determined by using a preset channel estimation algorithm for the cumulative signals, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values. It can be seen that for the uplink signals received by the base station from the terminals, in the case where different terminals multiplex the same time-frequency resource, by using the angle information of different terminals, the weighting coefficients of different antennas in the antenna array on the base station side are designed, so that a virtual beam with gain can be formed for the terminals, while the terminals at other angles have no gain. In this way, the signals from the terminals at other angles can be filtered out, and the signals of the terminals at the required angles can be obtained to acquire the diversity gain. In addition, weighting and summing the received signals by using the weighting coefficients can eliminate the data interference between the terminals and enhance the signal strength of the required terminals at the same time, which is a prerequisite for accurate frequency offset estimation of the terminals. Further, the channel estimation values corresponding to each of the multiple terminals are determined by using a preset channel estimation algorithm for the cumulative signals, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values, so as to realize the frequency offset estimation of different terminals relative to the base station under the condition that multiple-symbol pilot resources are multiplexed on the same time-frequency resource. Through the technical solution of the present application, the interference between terminals can be effectively reduced, and when the signal multiplexing of multiple terminals on the same time-frequency resource is supported, the resource utilization rate can be improved. And through the antenna weighting and accumulation technology, the signal-to-noise ratio of the received signals is increased, and the frequency offset estimation accuracy is improved. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0037] Figure 1 It is a flowchart of a frequency offset estimation method for the uplink channel in the MU-MIMO mode disclosed in the present application;

[0038] Figure 2 Schematic diagram of a MU-MIMO communication disclosed in this application;

[0039] Figure 3 Schematic diagram of dm-rs in a PUSCH channel disclosed in this application;

[0040] Figure 4 Schematic diagram of the phase difference when a terminal reaches a linear array disclosed in this application;

[0041] Figure 5 Flowchart of a method for frequency offset estimation of an uplink channel in a specific MU-MIMO mode disclosed in this application;

[0042] Figure 6 Flowchart of a terminal frequency offset estimation disclosed in this application;

[0043] Figure 7 Schematic diagram of the structure of a device for frequency offset estimation of an uplink channel in a MU-MIMO mode disclosed in this application;

[0044] Figure 8 Schematic diagram of the structure of an electronic device disclosed in this application. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Currently, when the reference signal or the cyclic prefix is the multiplexing and superposition of multiple terminal signals, due to the mutual interference between multiple terminals in the signal received by the base station, if the common frequency offset estimation method is to be used, it is necessary to allocate the signals of different terminals to different time-frequency resources, thus reducing the resource utilization rate of OFDM symbols.

[0047] For this reason, this application discloses a frequency offset estimation scheme for an uplink channel in a MU-MIMO mode, which can effectively reduce the interference between terminals, so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with multi-symbol pilot resource multiplexing.

[0048] The embodiments of the present invention disclose a method for frequency offset estimation of an uplink channel in a MU-MIMO mode. Refer to Figure 1 as shown, the method includes:

[0049] Step S11: Obtain the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and use a preset angle estimation algorithm to determine the respective angle information of the multiple terminals relative to the base station.

[0050] In the embodiments of the present application, when the reference signal or the cyclic prefix is the multiplexing and superposition of multiple terminal signals, for better understanding of the solution of the present application by those skilled in the art, the multi-symbol dm-rs in the MU-MIMO mode is taken as an example for illustration, and will not be elaborated hereinafter. As Figure 2 shown is a schematic diagram of a typical MU-MIMO communication. Assume that the terminal (UE) is a single antenna, there are a total of N terminals, and the number of antennas of the base station (GNB) is M. In the case of the uplink channel in the MU-MIMO mode, taking the 5G system as an example (OFDM modulation), the dm-rs of different terminals' PUSCH are multiplexed through different ports on the same time-frequency resource. The dm-rs in the PUSCH channel occupies two time-domain symbols, and the starting symbol is l0. There are a total of K subcarriers in the frequency domain. The dm-rs of multiple terminals are multiplexed through multiple ports on the same time-frequency resource. As Figure 3 shown is a schematic diagram of the time-frequency resource distribution at the receiving side of the terminal and the base station in a certain time slot.

[0051] In the embodiments of the present application, through the antenna array of the base station, the received signal Y of multiple symbols and multiple subcarriers in the shared channel superimposed by multiple terminals on the same time-frequency resource in the orthogonal frequency division multiplexing system in the MU-MIMO mode is obtained m (l, k).

[0052] It should be noted that in Figure 3 , the dm-rs signal transmitted on the nth UE, the lth symbol, and the kth subcarrier is X n (l, k), n = [0, 1, 2... N - 1], l = [l0, l0 + 1], k = [0, 1, 2... K - 1]; the receiver noise at the base station side is w m (l, k); then the dm-rs received signal of the mth antenna, the lth symbol, and the kth subcarrier at the base station side is Y m (l, k), m = [0, 1, 2... M - 1], l = [l0, l0 + 1], k = [0, 1, 2... K - 1]; where is the transmission channel from the nth terminal to the mth receiving antenna, the lth symbol, and the kth subcarrier.

[0053] In the embodiments of the present application, when the base station side obtains the dm-rs signal Y m (l, k) of multiple terminals superimposed by multiple antennas, multiple symbols, and multiple subcarriers, after arbitrarily selecting a certain subcarrier k' and a certain symbol l', the received data vector Y = [Y0 (l′, k′), Y 1 (l′, k′), …, Y (M-1) (l′, k′)] T , and then use a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station. For example, it can be obtained through an angle estimation algorithm such as a beamforming algorithm or a MUSIC (Multiple Signal Classification) algorithm. During the actual operation process, different subcarriers and symbols can be selected multiple times for terminal angle estimation, and then the average value of multiple calculations is used as the estimated value of the terminal angle.

[0054] Specifically, the received signal superimposed by multiple terminals corresponding to any one of the multiple subcarriers and any one of the multiple symbols on the same time-frequency resource is obtained through the antenna array of the base station to obtain the received vector of the received signal; based on the received vector, the angle information corresponding to each of the multiple terminals relative to the base station is determined by using a beamforming method or a MUSIC multiple signal classification algorithm.

[0055] Step S12: Determine the weighting coefficients of different antennas in the antenna array based on the angle information, and perform weighted summation on the received signal by using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information.

[0056] In the embodiment of the present application, since there is interference between terminals, it is necessary to filter out the terminal signals from other angles to eliminate the interference between terminals. As Figure 4 shown, when a uniformly distributed linear array is used, with the normal direction of the array as the reference, when terminals arrive at the receiving antenna array on the base station side from different angles, due to the different distances between different antennas and the terminals, there is a certain phase difference between the antennas. Under far-field conditions, this phase difference is the same between every two adjacent antennas, that is, 2π·d·sin(θ n ), θ n represents the angle of the nth terminal, λ is the wavelength, and usually d = λ / 2. Taking the phase of the 0th antenna as the reference, then the phase of the mth antenna is π·m·sin(θ n ). Therefore, the weighting coefficient weight n (m) = exp(-j·π·m·sin(θ n )) can be designed for different antennas in the array antenna, so that a virtual beam with gain can be formed for terminal n, while there is no gain for terminals at other angles, and the signal of the terminal at the required angle can be obtained to obtain the diversity gain. Thus, the terminal signals from other angles are filtered out to eliminate the interference between terminals. Among them, θ nIndicates the angle of the nth terminal, m is the mth antenna of the base station, m = [0, 1, 2…M - 1], and j is the imaginary unit.

[0057] In the embodiments of the present application, the weighted coefficient weight n (m) is used to perform weighted summation on the signals received by the antenna array to obtain the signal after multi-antenna accumulation from the terminal at angle θ n , which is expressed as The weighted summation of data between antennas can eliminate data interference between terminals and enhance the signal strength of the required terminal at the same time. It is the premise for the accurate estimation of the terminal frequency offset below and also the key step in the embodiments of the present application. Among them, weight n (m) is the weighted coefficient; Y m (l, k) is the received signal of the mth antenna, the lth symbol, and the kth subcarrier of the base station, m = [0, 1, 2…M - 1], l = [l0, l0 + 1] k = [0, 1, 2…K - 1].

[0058] Step S13: Use a preset channel estimation algorithm for the accumulated signal to determine the respective channel estimation values of the multi-terminals, and use the channel estimation values to determine the respective frequency offset information of the multi-terminals relative to the base station.

[0059] In the embodiments of the present application, for the signal Y′ n (l, k) of the weighted-accumulated terminal n, the LS (Least Square) channel estimation method is adopted, and the formula is used for channel estimation to obtain the channel estimation value of the corresponding reference signal; in the formula, is the channel estimation value of the lth symbol and the kth subcarrier after multi-antenna weighted accumulation of the nth terminal; the superscript H indicates conjugate transpose.

[0060] It should be noted that when there is a frequency offset in the system, the estimated channel has a certain phase difference -2π·Δf n ·T ofdm_symb in the time domain, satisfying where Δf n represents the frequency offset between terminal n and the base station, and T ofdm_symb is the duration of the OFDM symbol.

[0061] Therefore, the frequency offset of terminal n relative to the base station can be estimated by the following formula: where angle(·) represents the operation of finding the angle of a complex number.

[0062] In this application, when applied to the base station side, first, the receiving signals superimposed by multiple terminals on the same time-frequency resource are obtained through the antenna array of the base station, and the angle information corresponding to each of the multiple terminals relative to the base station is determined by using a preset angle estimation algorithm; then, based on the angle information, the weighting coefficients of different antennas in the antenna array are determined, and the receiving signals are weighted and summed by using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information; finally, the channel estimation values corresponding to each of the multiple terminals are determined by using a preset channel estimation algorithm for the cumulative signal, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values. It can be seen that for the uplink signal received by the base station from the terminal, in the case where different terminals multiplex the same time-frequency resource, by using the angle information of different terminals, the weighting coefficients of different antennas in the antenna array on the base station side are designed, so that a virtual beam with gain can be formed for the terminal, while there is no gain for the terminals at other angles. In this way, the signals from the terminals at other angles can be filtered out, and the signals of the terminals at the required angles can be obtained to acquire the diversity gain. Weighting and summing the receiving signals by using the weighting coefficients can eliminate the data interference between terminals and enhance the signal strength of the required terminal at the same time, which is a prerequisite for accurate estimation of the terminal frequency offset. Further, the channel estimation values corresponding to each of the multiple terminals are determined by using a preset channel estimation algorithm for the cumulative signal, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values, so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with multi-symbol pilot resource multiplexing. Through the technical solution of this application, the interference between terminals can be effectively reduced, the signal multiplexing of multiple terminals on the same time-frequency resource can be supported, and the resource utilization rate can be improved. And through the antenna weighting and accumulation technology, the signal-to-noise ratio of the receiving signal is increased, and the frequency offset estimation accuracy is improved.

[0063] The embodiment of this application discloses a specific method for estimating the frequency offset of the uplink channel in the MU-MIMO mode. Refer to Figure 5 as shown, this method includes:

[0064] Step S21: Obtain the receiving signal Y m (l, k) superimposed by multiple terminals on the same time-frequency resource of multiple symbols and multiple subcarriers in the shared channel in the MU-MIMO mode through the antenna array of the base station, and determine the angle information corresponding to each of the multiple terminals relative to the base station by using a preset angle estimation algorithm.

[0065] In the embodiment of this application, when estimating the frequency offset of the uplink channel in the MU-MIMO mode, the base station side obtains the dm-rs signal Y m (l, k) superimposed by multiple terminals of multiple antennas, multiple symbols, and multiple subcarriers, where The m-th antenna of the base station is denoted as m, where m = [0, 1, 2... M - 1]; l is the l-th time-domain symbol occupied by the signal, l = [l0, l0 + 1], and the starting symbol is l0; k is the k-th sub-carrier, k = [0, 1, 2... K - 1]; X n The transmitted signal X(l, k) on the k-th sub-carrier of the l-th time-domain symbol for the n-th terminal, where n = [0, 1, 2... N - 1], l = [l0, l0 + 1], and k = [0, 1, 2... K - 1]; h(l, k) is the transmission channel from the n-th terminal to the m-th antenna on the l-th time-domain symbol and the k-th sub-carrier; w m The receiver noise n(l, k) of the m-th antenna of the base station on the l-th time-domain symbol and the k-th sub-carrier.

[0066] In the embodiment of the present application, any sub-carrier k' and symbol l' are randomly selected to obtain the received data vector Y = [Y 0 (l', k'), Y 1 (l', k'), …, Y (M-1) (l', k')] of all antennas T , and the angle information θ of the terminal n is obtained through beamforming methods or angle estimation algorithms such as MUSIC n ; In the actual operation process, different sub-carriers and symbols can be selected multiple times for terminal angle estimation, and then the average value of multiple calculations is used as the estimated value of the angle of the terminal n.

[0067] Step S22: Based on the angle information, use weight n (m) = exp(-j·π·m·sin(θ n )) to determine the weighting coefficients of different antennas in the antenna array, and use to obtain the cumulative signal of the terminal corresponding to the angle information.

[0068] In the embodiment of the present application, according to the angle information θ of the terminal n n , the weighting coefficient weight of the antenna array on the base station side for the terminal n is calculated n (m) = exp(-j·π·m·sin(θ n ))), where j is the imaginary unit; using the weighting coefficient weight n (m), the received signals of the antenna array are weighted and summed to obtain the multi-antenna cumulative signal of the terminal n from the angle θ n

[0069] Step S23: Use the least squares channel estimation algorithm for the cumulative signal, through ​Determine the channel estimation values corresponding to each of the multiple terminals.

[0070] Step S24: Use to determine the respective frequency offset information of each of the multiple terminals relative to the base station.

[0071] In the embodiments of the present application, an LS channel estimation method is adopted to obtain the channel estimation results of multiple symbols and multiple subcarriers of terminal n, that is, when there is a frequency offset in the system, the estimated channel has a certain phase difference -2π·Δf n ·T ofdm_symb in the time domain, and the phase difference satisfies Therefore, the frequency offset of terminal n relative to the base station is estimated by for estimation.

[0072] It can be understood that after determining the frequency offset information of the current terminal relative to the base station, the step of using the preset angle estimation algorithm to determine the respective angle information of the multiple terminals relative to the base station is repeatedly executed until the frequency offset information of all terminals is estimated.

[0073] Such as Figure 6 shown in the overall flowchart of terminal frequency offset estimation. The dm-rs signals of the terminals are received by multiple antennas on the base station side. Taking the 0th antenna as a reference, the dm-rs data of multiple antennas for a certain subcarrier and symbol are selected to estimate the angle of the current terminal n to obtain angle information, and the weighting coefficient weight n (m) of the current terminal n relative to different antennas on the base station side is calculated using the angle information. The received signals of the antenna array on the base station side are weighted and summed using the weighting coefficient weight n (m) to obtain the cumulative signal Y′ n (l, k) of terminal n, that is, the cumulative signal of multiple terminals obtained by the mth antenna. Then, using the LS algorithm, the channel estimation result of terminal n is obtained, and the frequency offset of terminal n relative to the base station is estimated according to the channel estimation result. After calculating the frequency offset of the current terminal relative to the base station, continue to calculate the frequency offsets of other terminals to obtain the frequency offset information of all terminals.

[0074] Through the embodiments of the present application, in the case where the dm-rs of different terminals multiplex the same time-frequency resource, the interference between terminals can be effectively reduced, so as to realize the frequency offset estimation of different terminals relative to the base station under the dm-rs resource multiplexing. It should be noted that when performing frequency offset estimation, the dm-rs sequences for estimating the frequency offset may not be orthogonal, but for channel equalization, the pilot sequences still need to be orthogonal, which increases the flexibility of the pilot sequences.

[0075] In this application, when applied to the base station side, first, the receiving signals superimposed by multiple terminals on the same time-frequency resource are obtained through the antenna array of the base station, and the angle information corresponding to each of the multiple terminals relative to the base station is determined by using a preset angle estimation algorithm; then, based on the angle information, the weighting coefficients of different antennas in the antenna array are determined, and the receiving signals are weighted and summed by using the weighting coefficients to obtain the cumulative signals of the terminals corresponding to the angle information; finally, the channel estimation values corresponding to each of the multiple terminals are determined from the cumulative signals by using a preset channel estimation algorithm, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values. It can be seen that for the uplink signals received by the base station from the terminals, when different terminals multiplex the same time-frequency resource, by using the angle information of different terminals, the weighting coefficients of different antennas in the antenna array on the base station side are designed, so that a virtual beam with gain can be formed for the terminals, and there is no gain for the terminals at other angles. In this way, the signals from the terminals at other angles can be filtered out, and the signals of the terminals at the desired angles can be obtained to acquire the diversity gain. Weighting and summing the receiving signals by using the weighting coefficients can eliminate the data interference between the terminals and enhance the signal strength of the desired terminals at the same time, which is a prerequisite for accurate estimation of the terminal frequency offset. Further, the channel estimation values corresponding to each of the multiple terminals are determined from the cumulative signals by using a preset channel estimation algorithm, and the frequency offset information of each of the multiple terminals relative to the base station is determined by using the channel estimation values, so as to realize the frequency offset estimation of different terminals relative to the base station under the condition of multiplexing multiple-symbol pilot resources on the same time-frequency resource. Through the technical solution of this application, the interference between terminals can be effectively reduced, the signal multiplexing of multiple terminals on the same time-frequency resource can be supported, and the resource utilization rate can be improved. And through the antenna weighting and accumulation technology, the signal-to-noise ratio of the receiving signals is increased, and the frequency offset estimation accuracy is improved.

[0076] Correspondingly, an embodiment of this application also discloses a frequency offset estimation device for the uplink channel in the MU-MIMO mode. Refer to Figure 7 As shown, when applied to the base station side, the device includes:

[0077] A receiving signal acquisition module 11, configured to obtain the receiving signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station;

[0078] An angle information determination module 12, configured to determine the angle information corresponding to each of the multiple terminals relative to the base station by using a preset angle estimation algorithm;

[0079] A weighting coefficient determination module 13, configured to determine the weighting coefficients of different antennas in the antenna array based on the angle information;

[0080] The cumulative signal determination module 14 is configured to perform weighted summation on the received signal by using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information;

[0081] The frequency offset information determination module 15 is configured to use a preset channel estimation algorithm to determine the respective channel estimation values of the multiple terminals for the cumulative signal, and use the channel estimation values to determine the respective frequency offset information of the multiple terminals relative to the base station.

[0082] Wherein, for the more specific working processes of the above-mentioned respective modules, reference can be made to the corresponding content disclosed in the foregoing embodiments, and details will not be elaborated herein.

[0083] Thus, through the above solution of this embodiment, when applied to the base station side, first, the base station's antenna array is used to obtain the received signals superimposed by multiple terminals on the same time-frequency resource, and a preset angle estimation algorithm is used to determine the respective angle information of the multiple terminals relative to the base station; then, based on the angle information, the weighting coefficients of different antennas in the antenna array are determined, and the received signal is weighted and summed by using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information; finally, a preset channel estimation algorithm is used to determine the respective channel estimation values of the multiple terminals for the cumulative signal, and the channel estimation values are used to determine the respective frequency offset information of the multiple terminals relative to the base station. It can be seen that for the uplink signal received by the base station from the terminal, when different terminals multiplex the same time-frequency resource, by using the angle information of different terminals, the weighting coefficients of different antennas in the base station side's antenna array are designed, so that a virtual beam with gain can be formed for the terminal, while there is no gain for the terminals at other angles. In this way, the signals from the terminals at other angles can be filtered out, and the signals of the terminals at the required angles can be obtained to acquire the diversity gain. Performing weighted summation on the received signal by using the weighting coefficients can eliminate the data interference between terminals and enhance the signal strength of the required terminal at the same time, which is a prerequisite for accurate estimation of the terminal frequency offset. Further, a preset channel estimation algorithm is used to determine the respective channel estimation values of the multiple terminals for the cumulative signal, and the channel estimation values are used to determine the respective frequency offset information of the multiple terminals relative to the base station, so as to realize the frequency offset estimation of different terminals relative to the base station under the same time-frequency resource with multi-symbol pilot resource multiplexing. Through the technical solution of this application, the interference between terminals can be effectively reduced, the signal multiplexing of multiple terminals on the same time-frequency resource can be supported, and the resource utilization rate can be improved. And through the antenna weighted accumulation technology, the signal-to-noise ratio of the received signal is increased, and the frequency offset estimation accuracy is improved.

[0084] Furthermore, the embodiment of this application also discloses an electronic device, Figure 8It is a structural diagram of an electronic device 20 shown according to an exemplary embodiment. The content in the figure should not be regarded as any limitation on the scope of use of this application.

[0085] Figure 8 This is a schematic structural diagram of an electronic device 20 provided by an embodiment of this application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. Among them, the memory 22 is used to store a computer program, and the computer program is loaded and executed by the processor 21 to implement the relevant steps in the frequency offset estimation method for the uplink channel in the MU-MIMO mode disclosed in any of the foregoing embodiments.

[0086] In this embodiment, the power supply 23 is used to provide operating voltages for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and specific limitations are not imposed here; the input / output interface 25 is used to obtain external input data or output data to the outside, and its specific interface type can be selected according to specific application requirements, and no specific limitations are made here.

[0087] In addition, as a carrier for resource storage, the memory 22 can be a read-only memory, a random access memory, a magnetic disk, or an optical disc, etc. The resources stored thereon may include an operating system 221, a computer program 222, and data 223, etc. The data 223 can include various types of data. The storage method can be short-term storage or permanent storage.

[0088] Among them, the operating system 221 is used to manage and control each hardware device and the computer program 222 on the electronic device 20, and it can be Windows Server, Netware, Unix, Linux, etc. In addition to the computer program that can be used to complete the frequency offset estimation method for the uplink channel in the MU-MIMO mode executed by the electronic device 20 disclosed in any of the foregoing embodiments, the computer program 222 can further include computer programs that can be used to complete other specific tasks.

[0089] Further, the embodiments of the present application also disclose a computer-readable storage medium, where the computer-readable storage medium includes a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a magnetic disk, or an optical disk, or any other form of storage medium known in the technical field. Among them, when the computer program is executed by a processor, it implements the foregoing frequency offset estimation method for the uplink channel in the MU-MIMO mode. For the specific steps of this method, reference can be made to the corresponding content disclosed in the foregoing embodiments, and details will not be repeated here.

[0090] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and reference can be made to the description in the method part for related parts.

[0091] The steps of the frequency offset estimation or algorithm for the uplink channel in the MU-MIMO mode described in combination with the embodiments disclosed in this article can be implemented directly by hardware, software modules executed by a processor, or a combination of both. The software modules can be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the technical field.

[0092] Finally, it should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0093] The above has introduced in detail a frequency offset estimation method, apparatus, device, and medium for an uplink channel in the MU-MIMO mode provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A frequency offset estimation method for the uplink channel in MU-MIMO mode, characterized in that Applied to the base station side, including: Obtain the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and use a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station; Determine the weighting coefficients of different antennas in the antenna array based on the angle information, and perform weighted summation on the received signals using the weighting coefficients to obtain the cumulative signal of the terminal corresponding to the angle information; wherein, based on the angle information, use weight n (m) = exp(-j·π·m·sin(θ n )) to determine the weighting coefficients of different antennas in the antenna array; wherein, the θ n represents the angle of the nth terminal, n = [0, 1, 2... N-1]; m is the mth antenna of the base station, m = [0, 1, 2... M-1]; j is the imaginary unit; use to obtain the cumulative signal of the terminal corresponding to the angle information; wherein, weight n (m) is the weighting coefficient; Y m (l, k) is the received signal of the mth antenna, the lth time-domain symbol, and the kth subcarrier of the base station, m = [0, 1, 2... M-1], l = [l0, l0 + 1], k = [0, 1, 2... K-1]; l is the lth time-domain symbol occupied by the received signal, and the starting time-domain symbol is l0; Use a preset channel estimation algorithm to determine the channel estimation values corresponding to each of the multiple terminals for the accumulated signals, and use the channel estimation values to determine the frequency offset information of each of the multiple terminals relative to the base station.

2. The frequency offset estimation method for the uplink channel in the MU-MIMO mode according to claim 1, characterized in that, The obtaining the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station includes: Obtain the received signal Y of multi-terminal superposition on the same time-frequency resource of multi-time-domain symbols and multi-subcarriers in the shared channel in the MU-MIMO mode of the orthogonal frequency division multiplexing system through the antenna array of the base station m (l,k); Among them, m is the m-th antenna of the base station, m = [0, 1, 2... M - 1]; l is the l-th time-domain symbol occupied by the received signal, l = [l0, l0 + 1], and the starting time-domain symbol is l0; k is the k-th subcarrier, k = [0, 1, 2... K - 1]; X n (l, k) is the transmission signal of the n-th terminal, the l-th time-domain symbol, and the k-th subcarrier, n = [0, 1, 2... N - 1]; is the transmission channel from the n-th terminal to the m-th antenna, the l-th time-domain symbol, and the k-th subcarrier; w m (l, k) is the receiver noise of the m-th antenna of the base station, the l-th time-domain symbol, and the k-th subcarrier.

3. The frequency offset estimation method for the uplink channel in the MU-MIMO mode according to claim 2, wherein The obtaining the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station, and using a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station, includes: Obtain the received signals superimposed by multiple terminals corresponding to any one of the multiple subcarriers and any one of the multiple time-domain symbols on the same time-frequency resource through the antenna array of the base station to obtain the received vector of the received signals; Based on the received vector, use a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station.

4. The frequency offset estimation method for the uplink channel in the MU-MIMO mode according to claim 1, characterized in that The using a preset channel estimation algorithm to determine the channel estimation values corresponding to each of the multiple terminals for the accumulated signals includes: Using the least - squares channel estimation algorithm for the cumulative signal, through determine the channel estimation values corresponding to each of the multi - terminals; where X n (l,k) is the transmission signal of the nth terminal, n = [0,1,2...N - 1], the lth time - domain symbol, l = [l0,l0 + 1], and the kth sub - carrier, k = [0,1,2...K - 1]; the superscript H represents conjugate transpose; Y′ n (l,k) is the signal of terminal n after weighted accumulation.

5. The frequency offset estimation method for the uplink channel in the MU-MIMO mode according to claim 4, characterized in that The using the channel estimation values to determine the frequency offset information of each of the multiple terminals relative to the base station includes: When there is a frequency offset in the system, there is a phase difference in the time domain for the estimated channel; the phase difference satisfies where -2π·Δf n ·T ofdm_symb is the phase difference; Utilize to determine respective frequency offset information Δf of the multiple terminals relative to the base station n ; where Δf n represents the frequency offset between terminal n and the base station; T ofdm_symb is the duration of a time-domain symbol in an orthogonal frequency division multiplexing system; angle(·) represents the operation of finding the angle of a complex number.

6. A frequency offset estimation device for an uplink channel in MU-MIMO mode, characterized in that, Applied to the base station side, including: A received signal acquisition module, configured to obtain the received signals superimposed by multiple terminals on the same time-frequency resource through the antenna array of the base station; An angle information determination module, configured to use a preset angle estimation algorithm to determine the angle information corresponding to each of the multiple terminals relative to the base station; The weighting coefficient determination module is used to determine the weighting coefficients of different antennas in the antenna array based on the angle information; wherein, based on the angle information, use weight n (m)=exp(-j·π·m·sin(θ n )) to determine the weighting coefficients of different antennas in the antenna array; wherein, the θ n represents the angle of the nth terminal, n = [0, 1, 2... N - 1]; m is the mth antenna of the base station, m = [0, 1, 2... M - 1]; j is the imaginary unit; The cumulative signal determination module is configured to perform weighted summation on the received signal by using the weighting coefficient to obtain the cumulative signal of the terminal corresponding to the angle information; wherein, by using obtain the cumulative signal of the terminal corresponding to the angle information; wherein, weight n (m) is the weighting coefficient; Y m (l, k) is the received signal of the m-th antenna, the l-th time domain symbol, and the k-th subcarrier of the base station, m = [0, 1, 2... M-1], l = [l0, l0+1], k = [0, 1, 2... K-1]; l is the l-th time domain symbol occupied by the received signal, and the starting time domain symbol is l0; A frequency offset information determination module, configured to use a preset channel estimation algorithm to determine the channel estimation values corresponding to each of the multiple terminals for the accumulated signals, and use the channel estimation values to determine the frequency offset information of each of the multiple terminals relative to the base station.

7. An electronic device, characterized in that, The electronic device includes a processor and a memory; wherein, the memory is used to store a computer program, and the computer program is loaded and executed by the processor to implement the frequency offset estimation method for the uplink channel in the MU-MIMO mode according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, For storing a computer program; wherein the computer program, when executed by a processor, implements the frequency offset estimation method for the uplink channel in the MU-MIMO mode according to any one of claims 1 to 5.

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