Reciprocity calibration method for multi-base station cooperation

Abstract

The invention discloses a reciprocity calibration method for multi-base-station cooperation, which relates to the technical field of mobile communication, and comprises the following steps: setting one base station in a distributed multi-base-station cooperative transmission system as a master base station and the other base stations as slave base stations, coordinately allocating subcarrier resources to the master base station, and respectively allocating a pilot frequency subcarrier set to any slave base station, any slave base station pilot frequency subcarrier set sends an orthogonal frequency division multiplexing pilot frequency signal to the master base station at the same time, the master base station generates a synchronization signal and broadcasts the synchronization signal to all slave base stations, the slave base stations average all antenna receiving results through the received synchronization signal to obtain an average receiving signal, and the average receiving signal is sent to the master base station. And the slave base station carries out frequency domain transformation on the average received signal and extracts a frequency domain response from the pilot frequency subcarrier set after the frequency domain transformation so as to obtain a phase deviation between the slave base station and the master base station, and the slave base station carries out phase compensation on the sent signal according to the phase deviation in downlink data transmission so as to obtain the slave base station and the master base station of which the phases are aligned.

Description

Technical Field

[0001] This invention relates to the field of mobile communication technology, and in particular to a reciprocal calibration method for multi-base station cooperation. Background Technology

[0002] In distributed multi-base station cooperative transmission systems, especially in large-scale multiple-input multiple-output (MIMO) network architectures based on time-division duplex (TDD), utilizing channel reciprocity to achieve downlink beamforming has become a key technical path for improving spectral efficiency and system capacity. Theoretically, TDD systems share the same frequency band for uplink and downlink, and their channel response is reciprocal under ideal RF link conditions, allowing base stations to estimate the downlink channel using uplink pilots. However, in actual deployments, the independent RF front-ends of each base station exhibit non-ideal amplitude and phase response differences, leading to the disruption of inter-base station channel reciprocity, manifested as non-negligible inter-base station phase deviation.

[0003] Existing reciprocal calibration schemes generally suffer from technical bottlenecks, such as relying on channel state information or user feedback, making them unsuitable for pure air interface self-calibration scenarios. They also have high computational complexity, often involving multi-dimensional parameter joint optimization or one-dimensional phase search. As the number of base stations or the size of antennas increases, the computational load grows non-linearly, making it difficult to meet the requirements of low latency and high energy efficiency in 5G-Advanced and 6G systems. Furthermore, they have high synchronization signal overhead, and most methods require allocating independent time-frequency resources for each slave base station to send dedicated pilot signals, leading to pilot pollution or resource waste. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a reciprocal calibration method for multi-base station cooperation to address the problem that relying on channel state information or user feedback is difficult to apply to pure air interface self-calibration scenarios. It has high computational complexity, often involving multi-dimensional parameter joint optimization or one-dimensional phase search. When the number of base stations or the size of antennas increases, the computational load increases non-linearly, making it difficult to meet the requirements of low latency and high energy efficiency in 5G-Advanced and 6G systems. The synchronization signal overhead is large, and most methods require allocating independent time-frequency resources for each slave base station to send dedicated pilots, leading to pilot pollution or resource waste.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a reciprocal calibration method for multi-base station cooperation, comprising: In a distributed multi-base station cooperative transmission system, one base station is designated as the master base station, and the other base stations are designated as slave base stations. The primary base station coordinates and allocates subcarrier resources, and configures a set of non-overlapping pilot subcarriers for each slave base station. Simultaneously transmit orthogonal frequency division multiplexing pilot signals to the main base station on any set of pilot subcarriers corresponding to the base station; Each master base station generates a synchronization signal based on the received concurrent pilot signals from each slave base station, and broadcasts the synchronization signal to all slave base stations; Each base station averages the reception results of all its antennas using the received synchronization signal to obtain the average received signal. Each slave base station performs frequency domain transformation on the average received signal and extracts the frequency domain response from the set of pilot subcarriers after frequency domain transformation, thereby obtaining the phase deviation between the slave base station and the master base station; During downlink data transmission, the base station performs phase compensation on the transmitted signal based on the phase deviation, so that the phase of any slave base station is aligned with that of the master base station.

[0007] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, wherein: in the distributed multi-base station cooperative transmission system, one base station is designated as the master base station, and the remaining base stations are designated as slave base stations, the specific steps are as follows: During the system initialization phase, one base station is designated as the master base station from among the multiple base stations of the users participating in the collaborative service, and the remaining base stations are defined as slave base stations. The main base station undertakes coordination functions, including pilot subcarrier resource allocation, synchronization signal generation and broadcasting; It can arbitrarily perform uplink pilot transmission, downlink synchronization signal reception, phase deviation estimation, and downlink data phase compensation operations from the base station; The master base station and slave base station complete all calibration interactions through the air interface, without relying on wired backhaul links or external reference clock sources.

[0008] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, the steps of coordinating and allocating subcarrier resources for the master base station and configuring non-overlapping pilot subcarrier sets for each slave base station are as follows: The main base station obtains the total number of subcarriers in the orthogonal frequency division multiplexing system. The total number of subcarriers is determined by both the system bandwidth and the subcarrier spacing; The main base station will set the subcarrier indexes Divide into several disjoint subsets; Assume the system has a total of The slave base station reserves some subcarriers for regular data or control signaling transmission for the master base station, which is the second slave base station. Each base station is allocated a dedicated set of pilot subcarriers, denoted as . ; During allocation, it is ensured that there are no common subcarriers between any two sets of pilot subcarriers from the base station, i.e., the following condition is met. For all Established.

[0009] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, wherein: each slave base station simultaneously transmits orthogonal frequency division multiplexing pilot signals to the master base station on its corresponding pilot subcarrier set, the specific steps of which are as follows: For the From the base station, let the first... Each base station equipped with The first antenna, The RF transmit link gain of the antenna is complex. The receive link gain is a complex number. ; Due to differences in manufacturing and aging of each antenna radio frequency link, non-reciprocity also exists within the same base station. To eliminate this internal bias, the first Each base station first performs internal self-calibration on all antennas within the base station, using the first antenna as a reference. The The calibration factor that the antenna needs to be multiplied by is: ; in, and From base station The transmit gain and receive gain of the RF link for the first antenna are both complex numbers. and From base station The The transmit and receive gains of the RF link of the root antenna are also complex numbers; The calibration coefficient aligns the equivalent transmit and receive responses of all antennas relative to the first antenna. After completing the internal calibration, the first The base station constructs a pilot signal in the frequency domain, so that the first... A set of pilot subcarriers allocated by the base station Each subcarrier in Set a unit amplitude pilot symbol on the upper subcarrier and set the rest of the subcarriers to zero; Perform an inverse discrete Fourier transform on the frequency domain pilot signal to generate time-domain OFDM symbols, and then pass them through all... Both antennas simultaneously transmit to the main base station.

[0010] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, the master base station generates a synchronization signal based on the received concurrent pilot signals from each slave base station, and broadcasts the synchronization signal to all slave base stations. The specific steps are as follows: Main base station equipped The root receiving antenna receives the time-domain superimposed signal from all slave base stations, denoted as _____. The main base station Perform a discrete Fourier transform on each receiving antenna branch to obtain the frequency domain received signal vector. ; main base station Taking the complex conjugate, we get And then Perform a normalized discrete inverse Fourier transform to generate a time-domain synchronization signal. The expression is: ; Among them, superscript This indicates the conjugate transpose. The complex conjugate function of the frequency domain received signal vector of the main base station. For the normalized discrete Fourier transform matrix, The Middle The expression for each element is: ; Synchronization signal It implicitly contains the conjugate phase information of each base station pilot, and the synchronization signal structure is compatible with OFDM frames; The main base station transmits data via the downlink control channel in a dedicated time slot. Broadcast to all base stations.

[0011] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, wherein: each slave base station averages the reception results of all its antennas using the received synchronization signal to obtain an average received signal, the specific steps of which are as follows: No. The first from the base station The antenna received the synchronization signal broadcast by the main base station. Due to the effects of wireless channel fading and noise, the reception results of each antenna differ. Let the [missing information] be the [missing information]. The time-domain signal received by the antenna is ,in For time-domain sampling point index; No. Each base station performs an arithmetic average of all its received signals at each time-domain sampling point to obtain the single-channel average received signal. The formula is: ; in, To the base station The received signal after averaging To the base station The total number of antennas, To the base station The The synchronization signal received by the antenna from the main base station, Represents the index of the time-domain sampling point, and when When large enough, the average operation makes It approaches a deterministic value.

[0012] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, wherein: each slave base station performs frequency domain transformation on the average received signal, and extracts the frequency domain response from the pilot subcarrier set after frequency domain transformation, thereby obtaining the phase deviation between the slave base station and the master base station, the specific steps are as follows: No. The base station performs a discrete Fourier transform on the average received signal sequence to obtain the frequency domain received response; Extract the set of its own pilot subcarriers from the frequency domain response. The corresponding set of subcarrier values ; All corresponding By summing the results and taking the complex argument, a closed-form estimate of the phase deviation can be directly obtained. The formula is: ; in, To represent the angle taking the complex number, To the base station In the The frequency domain signal value received on each pilot subcarrier.

[0013] As a preferred embodiment of the reciprocal calibration method for multi-base station cooperation described in this invention, wherein: during downlink data transmission, each slave base station performs phase compensation on the transmitted signal based on the phase deviation to align the phase of the slave base station with that of the master base station. The specific steps are as follows: No. During the downlink coordinated transmission phase, each base station has data symbols to be transmitted. Multiplied by the phase deviation estimate The complex exponential compensation factor is used to obtain the compensated transmitted signal. The expression is: ; in, To the base station The compensated downlink transmission signal, Based on the estimated phase deviation The complex exponential compensation factor constitutes This is the original downlink data signal; Each from the base station Multiply by a complex exponential compensation factor during downlink data transmission. ,in, For the estimated base station Phase deviation from the main base station; Multiply by a coefficient when base station i transmits data downlink. Phase compensation is performed to make the phase difference between each slave base station and the master base station zero; All from base stations The parallel repetitive reception and processing steps calculate the phase deviation between the base station and the master base station. And compensation.

[0014] In a second aspect, the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, wherein the computer program, when executed by the processor, implements any step of the reciprocal calibration method for multi-base station cooperation as described in the first aspect of the present invention.

[0015] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the reciprocal calibration method for multi-base station cooperation as described in the first aspect of the present invention.

[0016] The beneficial effects of this invention are as follows: By constructing a master-slave base station collaborative architecture, using non-overlapping subcarriers to achieve concurrent pilot transmission of multiple slave base stations, and combining the conjugate synchronization signal generated by the master base station with the multi-antenna spatial averaging processing at the slave base station, an air self-calibration mechanism that does not require user participation, does not depend on channel state information, and does not require an external reference source is realized. Furthermore, a closed-form estimate of the phase deviation is obtained by summing the frequency domain pilot response and taking the angle, and downlink phase alignment is completed by applying complex exponential compensation, which reduces pilot overhead and computational complexity, supports parallel calibration of slave base stations of any scale, and effectively solves the technical bottlenecks in existing reciprocal calibration methods such as large synchronization signal overhead, high algorithm complexity, and dependence on CSI joint estimation or user feedback, thereby improving the coherence gain, system capacity, and engineering deployability of the distributed multi-base station collaborative system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the reciprocal calibration method for multi-base station cooperation in Example 1.

[0019] Figure 2 This is a comparison chart of the mean square error performance of the phase deviation estimation method of the present invention and the serial estimation method based on maximum likelihood in the six-base station cooperative transmission scenario in Example 1.

[0020] Figure 3 This is a comparison chart of the running time of the method of the present invention and the serial estimation method based on maximum likelihood in the six-base station cooperative transmission scenario in Example 1.

[0021] Figure 4 This is a comparison chart of downlink speed and rate in a distributed MIMO system where six base stations coordinate to serve eight users, as shown in Example 1. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Example 1, referring to Figures 1-4 This embodiment of the invention provides a reciprocal calibration method for multi-base station cooperation, comprising the following steps: S1. In a distributed multi-base station cooperative transmission system, one base station is designated as the master base station, and the other base stations are designated as slave base stations.

[0026] Furthermore, during the system initialization phase, one base station is designated as the master base station from among the multiple base stations of the users participating in the collaborative service, and the remaining base stations are defined as slave base stations. The main base station undertakes coordination functions, including pilot subcarrier resource allocation, synchronization signal generation and broadcasting; It can arbitrarily perform uplink pilot transmission, downlink synchronization signal reception, phase deviation estimation, and downlink data phase compensation operations from the base station; The master base station and slave base station complete all calibration interactions through the air interface, without relying on wired backhaul links or external reference clock sources.

[0027] It should be noted that by designating one of the multiple base stations participating in the collaborative service as the master base station during the system initialization phase, and defining the rest as slave base stations, a lightweight calibration architecture for master-slave collaboration is constructed. The master base station is centrally responsible for pilot resource allocation and synchronization signal broadcasting, while each slave base station independently completes local calibration operations. The entire process only interacts through the air interface, without relying on wired backhaul links or external high-precision clock sources, which reduces deployment complexity and hardware costs, while ensuring that the calibration process has good autonomy and scalability.

[0028] S2. Coordinate and allocate subcarrier resources to the master base station, and configure non-overlapping pilot subcarrier sets for each slave base station.

[0029] Furthermore, the main base station obtains the total number of subcarriers in the orthogonal frequency division multiplexing system. The total number of subcarriers is determined by both the system bandwidth and the subcarrier spacing; The main base station will set the subcarrier indexes Divide into several disjoint subsets; Assume the system has a total of The slave base station reserves some subcarriers for regular data or control signaling transmission for the master base station, which is the second slave base station. Each base station is allocated a dedicated set of pilot subcarriers, denoted as . ; During allocation, it is ensured that there are no common subcarriers between any two sets of pilot subcarriers from the base station, i.e., the following condition is met. For all Established.

[0030] It should be noted that the master base station determines the total number of subcarriers based on the system bandwidth and subcarrier spacing, and divides the subcarrier index set into non-overlapping subsets. Each slave base station is assigned a dedicated and non-overlapping set of pilot subcarriers, and multiple slave base stations are allowed to transmit orthogonal pilot signals concurrently within the same OFDM symbol. This avoids the increased latency caused by traditional time division multiplexing and the resource waste caused by frequency division multiplexing, greatly improves pilot efficiency, effectively supports parallel calibration of large-scale base station networks, and reduces overall signaling overhead.

[0031] S3. Simultaneously send orthogonal frequency division multiplexing pilot signals to the main base station on any set of pilot subcarriers corresponding to the base station.

[0032] Furthermore, regarding the first From the base station, let the first... Each base station equipped with The first antenna, The RF transmit link gain of the antenna is complex. The receive link gain is a complex number. ; Due to differences in manufacturing and aging of each antenna radio frequency link, non-reciprocity also exists within the same base station. To eliminate this internal bias, the first Each base station first performs internal self-calibration on all antennas within the base station, using the first antenna as a reference. The The calibration factor that the antenna needs to be multiplied by The expression is: ; in, and From base station The transmit gain and receive gain of the RF link for the first antenna are both complex numbers. and From base station The The transmit and receive gains of the RF link of the root antenna are also complex numbers; In practical signal processing, this calibration coefficient is applied to the transmit link of the antenna, when the first... When the antenna is ready to transmit pilot or data signals, its baseband output signal Before entering the RF front end, multiply by a calibration factor. The calibrated transmission signal is obtained: ; in, To the base station The The baseband output signal of the antenna. For calibration coefficients; After amplification via the radio frequency link, the actual radiated signal is: ; in, For the calibrated transmission signal, To the base station The The baseband output signal of the antenna. For calibration coefficients, and From base station The The transmit and receive gain of the RF link of the root antenna; During reception, reciprocity is used for uplink channel estimation, and the received signal... ,in For wireless channels, It is a signal sent by the user equipment in the uplink; The received signal is usually divided by the receive gain. In order to recover the equivalent baseband signal, after the above-mentioned transmitter calibration, the equivalent response of the entire transceiver link is aligned with the first antenna. After completing the internal calibration, the first The base station constructs a pilot signal in the frequency domain, so that the first... A set of pilot subcarriers allocated by the base station Each subcarrier in Set a unit amplitude pilot symbol on the upper subcarrier and set the rest of the subcarriers to zero; Perform an inverse discrete Fourier transform on the frequency domain pilot signal to generate time-domain OFDM symbols, and then pass them through all... Both antennas simultaneously transmit to the main base station.

[0033] It should be noted that, in response to the non-reciprocity of the transmit and receive links within the same base station due to differences in radio frequency devices, a calibration coefficient with the first antenna as a reference is applied to each antenna to align the equivalent transmit and receive responses of all antennas in a relative sense. Internal self-calibration ensures that the pilot signals transmitted from the base station only reflect the phase deviation between base stations, rather than internal link mismatch, thereby improving the accuracy of subsequent phase estimation and providing a reliable prerequisite for achieving high-precision full-network calibration.

[0034] S4. The master base station generates a synchronization signal based on the received pilot signals from each slave base station and broadcasts the synchronization signal to all slave base stations.

[0035] Furthermore, the main base station is equipped with The root receiving antenna receives the time-domain superimposed signal from all slave base stations, denoted as _____. The main base station Perform a discrete Fourier transform to obtain the frequency domain received signal. ; main base station Taking the complex conjugate, we get And then Perform a normalized discrete inverse Fourier transform to generate a time-domain synchronization signal. The expression is: ; Among them, superscript This indicates the conjugate transpose. The complex conjugate function of the frequency domain received signal vector of the main base station. For the normalized discrete Fourier transform matrix, The Middle The expression for each element is: ; Synchronization signal It implicitly contains conjugate phase information from any base station pilot, and the synchronization signal structure is compatible with OFDM frames; The main base station transmits data via the downlink control channel in a dedicated time slot. Broadcast to all base stations.

[0036] It should be noted that the master base station performs frequency domain transformation on the received concurrent pilot signals, takes the conjugate, and then generates a synchronization signal through normalized inverse Fourier transform. This signal is naturally compatible with the OFDM frame structure and implicitly contains the conjugate phase information of the pilots of each slave base station. The global phase reference can be transmitted to all slave base stations through a single broadcast, avoiding the high overhead of sending synchronization sequences station by station, simplifying the design of air signaling, and providing a consistent and efficient basis for phase extraction for slave base stations.

[0037] S5. Each base station averages the reception results of all its antennas using the received synchronization signal to obtain the average received signal.

[0038] Furthermore, the first The first from the base station The antenna received the synchronization signal broadcast by the main base station. Due to the effects of wireless channel fading and noise, the reception results of each antenna differ. Let the [missing information] be the [missing information]. The time-domain signal received by the antenna is ,in For time-domain sampling point index; No. Each base station performs an arithmetic average of all its received signals at each time-domain sampling point to obtain the single-channel average received signal. The formula is: ; in, To the base station The received signal after averaging To the base station The total number of antennas, To the base station The The synchronization signal received by the antenna from the main base station, Represents the index of the time-domain sampling point, and when When large enough, the average operation makes It approaches a deterministic value.

[0039] It should be noted that each base station performs an arithmetic average of the synchronization signals received by its multiple antennas at each time-domain sampling point. This fully utilizes the spatial averaging effect of the large-scale antenna array. When the number of antennas is large enough, this operation can suppress the small-scale fading and additive noise effects of the wireless channel, making the average received signal approach a deterministic value, improving the signal-to-noise ratio and stability of subsequent frequency domain processing, and laying a solid foundation for high-precision phase deviation estimation.

[0040] S6. Each slave base station performs frequency domain transformation on the average received signal and extracts the frequency domain response from the set of pilot subcarriers after frequency domain transformation, thereby obtaining the phase deviation between the slave base station and the master base station.

[0041] Furthermore, the first The base station performs a discrete Fourier transform on the average received signal sequence to obtain the frequency domain received response; Extract the set of its own pilot subcarriers from the frequency domain response. The corresponding set of subcarrier values ; All corresponding By summing the results and taking the complex argument, a closed-form estimate of the phase deviation can be directly obtained. The formula is: ; in, To represent the angle taking the complex number, To the base station In the The frequency domain signal value received on each pilot subcarrier.

[0042] It should be noted that after the base station performs frequency domain transformation on the average signal, the response value is extracted from the base station's dedicated pilot subcarrier, and the complex argument is summed to directly obtain the closed-form estimate of the phase deviation with the main base station. This method requires no channel state information, no user feedback, no iteration or search, has extremely low computational complexity and high estimation accuracy, and can quickly and accurately quantify the cross-site phase offset, providing reliable parameters for downlink compensation.

[0043] S7. During downlink data transmission, each slave base station performs phase compensation on the transmitted signal based on the phase deviation, so that the phase of any slave base station is aligned with that of the master base station.

[0044] Furthermore, the first During the downlink coordinated transmission phase, each base station has data symbols to be transmitted. Multiplied by the phase deviation estimate The complex exponential compensation factor is used to obtain the compensated transmitted signal. The expression is: ; in, To the base station The compensated downlink transmission signal, Based on the estimated phase deviation The complex exponential compensation factor constitutes This is the original downlink data signal; Each from the base station Multiply by a complex exponential compensation factor during downlink data transmission. ,in, For the estimated base station Phase deviation from the main base station; Multiply by a coefficient when base station i transmits data downlink. Phase compensation is performed to make the phase difference between each slave base station and the master base station zero; Arbitrary from base station The parallel repetitive reception and processing steps calculate the phase deviation between the base station and the master base station. And compensation.

[0045] It should be noted that during downlink transmission, each slave base station multiplies the data to be transmitted by a complex exponential factor constructed based on the estimated phase deviation for phase compensation. This ensures that the transmitted signal remains in phase with the main base station signal when it propagates to the user end. After this compensation, the downlink signal of any slave base station is strictly aligned with the main base station signal when it propagates to the user end, achieving coherent superposition of signals from multiple base stations across the network. The entire distributed system completes the full reciprocity calibration process. The final calibration result is that all slave base stations achieve phase consistency with the main base station at the radio frequency link level, the system restores ideal TDD reciprocity, and can fully utilize the cooperative beamforming gain to improve the user's received signal-to-interference-plus-noise ratio and system capacity.

[0046] This embodiment also provides a computer device applicable to a reciprocal calibration method for multi-base station cooperation, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the reciprocal calibration method for multi-base station cooperation as proposed in the above embodiment.

[0047] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0048] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the reciprocal calibration method for multi-base station cooperation as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0049] In summary, this invention constructs a master-slave base station collaborative architecture, utilizes non-overlapping subcarriers to achieve concurrent pilot transmission from multiple slave base stations, and combines the conjugate synchronization signal generated by the master base station with the spatial averaging of multiple antennas at the slave base station. This achieves an air self-calibration mechanism that requires no user participation, does not rely on channel state information, and does not require an external reference source. The closed-form estimate of phase deviation is obtained by summing the frequency domain pilot response and taking the angle, and downlink phase alignment is completed by applying complex exponential compensation. This reduces pilot overhead and computational complexity, supports parallel calibration of slave base stations of any scale, and effectively solves the technical bottlenecks of existing reciprocal calibration methods, such as large synchronization signal overhead, high algorithm complexity, and reliance on CSI joint estimation or user feedback. This improves the coherence gain, system capacity, and engineering deployability of the distributed multi-base station collaborative system.

[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A reciprocal calibration method for multi-base station cooperation, characterized in that: include: In a distributed multi-base station cooperative transmission system, one base station is designated as the master base station, and the other base stations are designated as slave base stations. The primary base station coordinates and allocates subcarrier resources, and configures a set of non-overlapping pilot subcarriers for each slave base station. Simultaneously transmit orthogonal frequency division multiplexing pilot signals to the main base station on any set of pilot subcarriers corresponding to the base station; The master base station generates a synchronization signal based on the received concurrent pilot signals from each slave base station, and broadcasts the synchronization signal to all slave base stations; Each base station averages the reception results of all its antennas using the received synchronization signal to obtain the average received signal. Each slave base station performs frequency domain transformation on the average received signal and extracts the frequency domain response from the set of pilot subcarriers after frequency domain transformation, thereby obtaining the phase deviation between the slave base station and the master base station; During downlink data transmission, each slave base station performs phase compensation on the transmitted signal based on the phase deviation, so that the phase of any slave base station is aligned with that of the master base station.

2. The reciprocal calibration method for multi-base station cooperation as described in claim 1, characterized in that: The specific steps for setting one base station as the master base station and the other base stations as slave base stations in the distributed multi-base station cooperative transmission system are as follows: During the system initialization phase, one base station is designated as the master base station from among the multiple base stations of the users participating in the collaborative service, and the remaining base stations are defined as slave base stations. The main base station undertakes coordination functions, including pilot subcarrier resource allocation, synchronization signal generation and broadcasting; It can arbitrarily perform uplink pilot transmission, downlink synchronization signal reception, phase deviation estimation, and downlink data phase compensation operations from the base station; The master base station and slave base station complete all calibration interactions through the air interface, without relying on wired backhaul links or external reference clock sources.

3. The reciprocal calibration method for multi-base station cooperation as described in claim 2, characterized in that: The steps for coordinating and allocating subcarrier resources for the primary base station and configuring non-overlapping pilot subcarrier sets for each slave base station are as follows: The main base station obtains the total number of subcarriers in the orthogonal frequency division multiplexing system. The total number of subcarriers is determined by both the system bandwidth and the subcarrier spacing. The main base station will set the subcarrier indexes Divide into several disjoint subsets; Assume the system has a total of The slave base station reserves some subcarriers for regular data or control signaling transmission for the master base station, which is the second slave base station. Each base station is allocated a dedicated set of pilot subcarriers, denoted as . ; During allocation, it is ensured that there are no common subcarriers between any two sets of pilot subcarriers from the base station, i.e., the following condition is met. For all Established.

4. The reciprocity calibration method for multi-base station cooperation as described in claim 3, characterized in that: Each slave base station simultaneously transmits orthogonal frequency division multiplexing pilot signals to the master base station on its corresponding pilot subcarrier set. The specific steps are as follows: For the From the base station, let the first... Each base station equipped with The first antenna, The RF transmit link gain of the antenna is complex. The receive link gain is a complex number. ; Due to differences in manufacturing and aging of each antenna radio frequency link, non-reciprocity also exists within the same base station. To eliminate this internal bias, the first Each base station first performs internal self-calibration on all antennas within the base station, using the first antenna as a reference. The The calibration factor that the antenna needs to be multiplied by is: ; in, and From base station The transmit gain and receive gain of the RF link for the first antenna are both complex numbers. and From base station The The transmit and receive gains of the RF link of the root antenna are also complex numbers; The calibration coefficient aligns the equivalent transmit and receive responses of all antennas relative to the first antenna. After completing the internal calibration, the first The base station constructs a pilot signal in the frequency domain, so that the first... A set of pilot subcarriers allocated by the base station Each subcarrier in Set a unit amplitude pilot symbol on the upper subcarrier and set the rest of the subcarriers to zero; Perform an inverse discrete Fourier transform on the frequency domain pilot signal to generate time-domain OFDM symbols, and then pass them through all... Both antennas simultaneously transmit to the main base station.

5. The reciprocity calibration method for multi-base station cooperation as described in claim 4, characterized in that: The master base station generates a synchronization signal based on the received concurrent pilot signals from each slave base station, and broadcasts the synchronization signal to all slave base stations. The specific steps are as follows: Main base station equipped The root receiving antenna receives the time-domain superimposed signal from all slave base stations, denoted as _____. The main base station Perform a discrete Fourier transform on each receiving antenna branch to obtain the frequency domain received signal vector. ; main base station Taking the complex conjugate, we get And then Perform a normalized discrete inverse Fourier transform to generate a time-domain synchronization signal. The expression is: ; Among them, superscript This indicates the conjugate transpose. The complex conjugate function of the frequency domain received signal vector of the main base station. For the normalized discrete Fourier transform matrix, The Middle The expression for each element is: ; Synchronization signal It implicitly contains the conjugate phase information of each base station pilot, and the synchronization signal structure is compatible with OFDM frames; The main base station transmits data via the downlink control channel in a dedicated time slot. Broadcast to all base stations.

6. The reciprocal calibration method for multi-base station cooperation as described in claim 5, characterized in that: Each base station averages the reception results of all its antennas using the received synchronization signal to obtain an average received signal. The specific steps are as follows: No. The first from the base station The antenna received the synchronization signal broadcast by the main base station. Due to the effects of wireless channel fading and noise, the reception results of each antenna differ. Let the [missing information] be the [missing information]. The time-domain signal received by the antenna is ,in For time-domain sampling point index; No. Each base station performs an arithmetic average of all its received signals at each time-domain sampling point to obtain the single-channel average received signal. The formula is: ; in, To the base station The received signal after averaging To the base station The total number of antennas, To the base station The The synchronization signal received by the antenna from the main base station, Represents the index of the time-domain sampling point, and when When large enough, the average operation makes It approaches a deterministic value.

7. The reciprocal calibration method for multi-base station cooperation as described in claim 6, characterized in that: Each slave base station performs frequency domain transformation on the average received signal and extracts the frequency domain response from the transformed pilot subcarrier set to obtain the phase deviation between the slave base station and the master base station. The specific steps are as follows: No. The base station performs a discrete Fourier transform on the average received signal sequence to obtain the frequency domain received response; Extract the set of its own pilot subcarriers from the frequency domain response. The corresponding set of subcarrier values ; All corresponding By summing the results and taking the complex argument, a closed-form estimate of the phase deviation can be directly obtained. The formula is: ; in, To represent the angle taking the complex number, To the base station In the The frequency domain signal value received on each pilot subcarrier.

8. The reciprocal calibration method for multi-base station cooperation as described in claim 7, characterized in that: During downlink data transmission, each slave base station performs phase compensation on the transmitted signal based on the phase deviation to align the phase of the slave base station with that of the master base station. The specific steps are as follows: No. During the downlink coordinated transmission phase, each base station has data symbols to be transmitted. Multiplied by the phase deviation estimate The complex exponential compensation factor is used to obtain the compensated transmitted signal. The expression is: ; in, To the base station The compensated downlink transmission signal, Based on the estimated phase deviation The complex exponential compensation factor constitutes This is the original downlink data signal; Each from the base station Multiply by a complex exponential compensation factor during downlink data transmission. ,in, For the estimated base station Phase deviation from the main base station; Multiply by a coefficient when base station i transmits data downlink. Phase compensation is performed to make the phase difference between each slave base station and the master base station zero; Each from base station The parallel repetitive reception and processing steps calculate the phase deviation between the base station and the master base station. And compensation.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the reciprocal calibration method for multi-base station cooperation as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the reciprocal calibration method for multi-base station cooperation as described in any one of claims 1 to 8.

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