Electronic device, system, control method, and program

Abstract

An electronic device according to the present invention, which is provided with a plurality of sub-arrays including a plurality of antenna elements and which performs multiuser MIMO communication with a plurality of other electronic devices, comprises a precoder that performs precoding in which spatial multiplexing between the plurality of other electronic devices is performed independently for each orthogonal polarization, and transmits, to the plurality of other electronic devices, a signal having been subjected to the precoding by the precoder.

Description

Electronic device, system, control method, and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2024-100816, filed on June 21, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to an electronic device, a system, a control method, and a program.

[0003] As a technology for improving the communication quality of wireless communication, MIMO (multiple-input and multiple-output), which uses multiple antennas at both the transmitter and the receiver, has been attracting attention. MIMO plays an important part in recent wireless communication standards such as IEEE 802.11n (Wi-Fi), 4G, 3GPP (registered trademark) Long Term Evolution, WiMAX, and HSPA+. Single-user MIMO (SU-MIMO) is known as MIMO transmission performed at the same time and frequency for a single user. Multi-user MIMO (MU-MIMO) is also known as MIMO transmission performed at the same time and frequency for multiple users. Furthermore, research is also underway into massive MIMO as a technology for stabilizing and / or speeding up communication paths by significantly increasing the number of transmitting and receiving antennas (for example, up to 128).

[0004] When performing spatial multiplexing, a transmitter used in a MU-MIMO system performs a process of multiplying weights by vectors that constitute a transmission weight matrix, that is, precoding (see, for example, Non-Patent Document 1).

[0005] Christian B. Peel and two others, "A Vector-Perturbation Technique for Near-Capacity Multi-Antenna Multi-User Communication - Part I: Channel Inversion and Regularization," [online], January 1, 2005, IEEE Transactions on Signal Processing, Vol. 53, No. 1, pp. 195-202. [Retrieved May 14, 2024], Internet <URL: https: / / www.researchgate.net / publication / 3161498_A_Vector-Perturbation_Technique_for_Near-Capacity_Multiantenna_Multiuser_Communication-Part_I_Channel_Inversion_and_Regularization>

[0006] An electronic device (first electronic device) according to one embodiment includes a plurality of subarrays each including a plurality of antenna elements, and performs multi-user MIMO communication with a plurality of other electronic devices (second electronic devices). The electronic device includes a precoder that performs precoding by independently performing spatial multiplexing between the plurality of other electronic devices (second electronic devices) for each of orthogonal polarizations, and transmits signals that have been precoded by the precoder to the plurality of other electronic devices (second electronic devices).

[0007] According to one embodiment, the system includes an electronic device (first electronic device) and a plurality of other electronic devices (second electronic devices). In the system, the electronic device (first electronic device) includes a plurality of subarrays each including a plurality of antenna elements, and performs multi-user MIMO communication with the plurality of other electronic devices (second electronic devices). The electronic device (first electronic device) includes a precoder that performs precoding by independently performing spatial multiplexing between the plurality of other electronic devices (second electronic devices) for each of orthogonal polarizations, and transmits signals that have been precoded by the precoder to the plurality of other electronic devices (second electronic devices).

[0008] A control method according to one embodiment is a control method for an electronic device (first electronic device) that has a plurality of subarrays, each including a plurality of antenna elements, and that performs multi-user MIMO communication with a plurality of other electronic devices (second electronic devices), and includes the steps of: performing precoding to perform spatial multiplexing between the plurality of other electronic devices (second electronic devices) independently for each of orthogonal polarizations; and transmitting the precoded signals to the plurality of other electronic devices (second electronic devices).

[0009] A program according to one embodiment causes an electronic device (first electronic device) that has a plurality of subarrays, each including a plurality of antenna elements, and that performs multi-user MIMO communication with a plurality of other electronic devices (second electronic devices), to perform precoding, which performs spatial multiplexing between the plurality of other electronic devices (second electronic devices) independently for each of orthogonal polarizations, and to transmit the precoded signals to the plurality of other electronic devices (second electronic devices).

[0010] FIG. 1 is a diagram illustrating an example of a system including a first electronic device and a second electronic device according to an embodiment; FIG. 2 is a block diagram illustrating a schematic functional configuration of a first electronic device according to an embodiment; FIG. 3 is a diagram illustrating an operation of a system according to an embodiment; FIG. 4 is a diagram illustrating an operation of a system according to an embodiment; FIG. 5 is a diagram illustrating an example of an environment in which radio waves propagate from a first electronic device to a second electronic device; FIG. 6 is a graph illustrating a result of simulating an operation by a first electronic device according to an embodiment; and FIG. 7 is a flowchart illustrating an example of an operation by a first electronic device according to an embodiment.

[0011] In the present disclosure, an "electronic device" may refer to a device driven by electricity. Furthermore, a "system" may refer to a device or devices including a device driven by electricity. Furthermore, a "user" may refer to a person (typically a human) who uses a system and / or electronic device according to an embodiment. By using a system and / or electronic device according to an embodiment, it is possible to reduce the processing load when performing precoding in MIMO.

[0012] <System including first electronic device 1 according to one embodiment> It is desirable to reduce the processing load (e.g., calculation cost) when performing precoding in MIMO as described above as much as possible. The present disclosure relates to an electronic device, a system, a control method, and a program that can reduce the processing load when performing precoding in MIMO. According to one embodiment, it is possible to provide an electronic device, a system, a control method, and a program that can reduce the processing load when performing precoding in MIMO. First, the overall system configuration of one embodiment will be described.

[0013] Fig. 1 is a diagram illustrating an example of a system including an electronic device according to an embodiment. Fig. 1 is a diagram illustrating the configuration of a system including an electronic device according to an embodiment, mainly from a functional perspective.

[0014] A system including an electronic device according to an embodiment may be configured based on at least a part of a concept similar to that of a general MIMO system. As shown in FIG. 1 , the system according to an embodiment may include a first electronic device 1 and a second electronic device 2.

[0015] The first electronic device 1 may be, for example, a base station (mobile communication base station) gNB (gNodeB) compatible with 5G wireless communication. The first electronic device 1 may include at least one subarray 10 (antenna array). The first electronic device 1 shown in FIG. 1 includes multiple subarrays 10, including subarray 10A, subarray 10B, ..., subarray 10N. Hereinafter, when subarrays such as subarray 10A, subarray 10B, ..., subarray 10N are not particularly distinguished from one another, they may be simply referred to as "subarrays 10." The first electronic device 1 according to an embodiment may include any multiple subarrays 10. The first electronic device 1 according to an embodiment may not include some of the functional units shown in FIG. 1, or may include functional units other than those shown in FIG. 1. A more detailed configuration of the first electronic device 1 will be described later.

[0016] Each subarray 10 may include a plurality of antenna elements (e.g., patches). Each subarray 10 shown in Figure 1 is shown schematically as having a large number of small antenna elements arranged in the up-down (vertical) and left-right (horizontal) directions.

[0017] The second electronic device 2 may be, for example, a terminal (mobile communication terminal) UE (User Equipment) compatible with 5G wireless communication. A system according to an embodiment may include at least one second electronic device 2. The system shown in FIG. 1 includes multiple second electronic devices 2, such as second electronic device 2A, second electronic device 2B, ..., second electronic device 2N. Hereinafter, when no particular distinction is made between second electronic devices such as second electronic device 2A, second electronic device 2B, ..., second electronic device 2N, they may be simply referred to as "second electronic device 2." A system according to an embodiment may include any multiple second electronic devices 2. The second electronic device 2 may be based on the same concept as a UE compatible with a MIMO system, and therefore further detailed description thereof will be omitted.

[0018] 1, the subarray 10A of the first electronic device 1 may be configured to realize a connection with the second electronic device 2A. The subarray 10B of the first electronic device 1 may be configured to realize a connection with the second electronic device 2B. The subarray 10C of the first electronic device 1 may be configured to realize a connection with the second electronic device 2C.

[0019] A signal transmitted from the first electronic device 1 to the second electronic device 2 may undergo signal processing as shown from top to bottom in the first electronic device 1 illustrated in FIG. 1 . That is, first, digital precoding of the signal to be transmitted is performed in the first electronic device 1. Here, digital precoding may correspond to spatial multiplexing in multi-user MIMO and single-user MIMO. Then, the digitally precoded signal may be supplied to each analog beam control function corresponding to each subarray 10, with each subarray 10 having m layers (m layers / subarray). Next, analog precoding is performed on the digitally precoded signal by the analog beam control function corresponding to each of the multiple subarrays 10. Then, the analog precoded signal may be transmitted from the multiple subarrays 10, each corresponding to a corresponding analog beam control function, toward each of the second electronic devices 2.

[0020] 1 , the single-user MIMO signals transmitted from the plurality of subarrays 10 included in the first electronic device 1 to the corresponding second electronic devices may each have two layers (polarized waves). As an example, these two layers may be horizontally polarized waves (H polarization) and vertically polarized waves (V polarization). However, they do not have to be horizontally polarized waves (H polarization) and vertically polarized waves (V polarization) as long as they are orthogonal to each other.

[0021] In fifth-generation mobile communication systems (5G), multi-user massive MIMO (multiple-input, multiple-output) systems, which use multiple antenna elements to spatially multiplex multiple UEs, are being widely studied to improve cell throughput. To achieve massive MIMO, multiple antenna elements must be connected to corresponding analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). Therefore, massive MIMO systems tend to increase power consumption and device costs. Therefore, in recent years, hybrid beamforming configurations have been studied, in which multiple antenna elements are divided into multiple subarrays 10, and each subarray 10 is connected to one second electronic device 2 (UE), as shown in FIG. 1 .

[0022] Hereinafter, a system according to an embodiment will be described as configuring hybrid beamforming as shown in Fig. 1. However, the system according to an embodiment is not limited to the hybrid type, and may also configure, for example, full digital beamforming.

[0023] In addition, in a system according to an embodiment described below, single-user MIMO may be polarization multiplexed. Furthermore, in a system according to an embodiment described below, time division duplex (TDD) may be adopted as the duplexing method. Here, when calculating weights for downlink precoding (first precoding method described below), channel information estimated using uplink SRS (Sounding Reference Signal) may be used.

[0024] Fig. 2 is a block diagram illustrating the functional configuration of the first electronic device 1 according to an embodiment, mainly illustrating the configuration of hardware and software of the first electronic device 1 according to an embodiment.

[0025] A 5G base station generally includes a radio unit (RU) that constitutes a radio section including the antenna of the base station, a distributed unit (DU) also called a slave station, and a central unit (CU) that is called a master station or aggregation station. The RU has the function of transmitting and receiving radio waves to and from a user equipment (UE), which is a terminal (mobile device) for communication, and communicating with the DU. The DU mainly has the function of modulating and demodulating signals and retransmitting lost signals. The CU mainly has the function of controlling multiple DUs and controlling the radio resource control (RRC), which is a communication protocol between the UE and the base station.

[0026] The first electronic device 1 according to one embodiment may be configured to include components based on standard specifications established by the Open Radio Access Network (O-RAN) Alliance. The O-RAN Alliance is an industry association established by agreement among multiple companies. For example, the first electronic device 1 according to one embodiment may implement the above-described RU, DU, and CU as components based on the O-RAN specifications. The first electronic device 1 shown in FIG. 2 implements components based on the O-RAN specifications as hardware and / or software.

[0027] For example, the first electronic device 1 according to one embodiment may include an O-RAN radio unit (O-RU) as a component of an O-RAN network that functions as a radio access node. The first electronic device 1 may also include an O-RAN distributed unit (O-DU) as a component that performs radio access functions such as data modulation, demodulation, and / or decoding / encoding. Furthermore, the first electronic device 1 may also include an O-RAN centralized unit (O-CU) that manages the interface between the core network and the RAN and coordinates the operations of various components such as the radio unit and the distributed unit.

[0028] 2 , the first electronic device 1 according to one embodiment may include an information processing device 20 in addition to the plurality of subarrays 10 (subarrays 10A to 10N) described above. The information processing device 20 may be configured as hardware, for example. For example, the information processing device 20 may be configured using a general-purpose server device or the like.

[0029] The information processing device 20 may include a control unit 22, an O-CU 24, and an O-DU 26. The O-DU 26 may also include a precoder 262. At least one of the control unit 22, the O-CU 24, the O-DU 26, and the precoder 262 may be configured to include at least one of software and hardware resources, for example. In one embodiment, at least one of the aforementioned functional units may be configured by specific means in which software and hardware resources work together.

[0030] 2, the first electronic device 1 according to an embodiment may include an O-RU 30 in addition to the plurality of subarrays 10 and the information processing device 20. The O-RU 30 may be configured as hardware, for example. The control unit 22 and the O-RU 30 may be configured to include at least one of software and hardware resources. In an embodiment, the O-RU 30 may be configured by specific means in which software and hardware resources work together. The first electronic device 1 according to an embodiment may not include some of the functional units shown in FIG. 2, or may include functional units other than those shown in FIG. 2.

[0031] The control unit 22 acquires predetermined determination information from the O-DU 26 and performs predetermined determination processing. The O-DU 26 (and the precoder 262) may perform predetermined operations based on control by the O-CU 24. The control unit 22 also outputs predetermined instructions to the O-DU 26 based on the results of the predetermined determination processing, etc. In particular, the precoder 262 may perform predetermined precoding based on instructions from the control unit 22. The processing performed by the control unit 22 and the O-DU 26 (particularly the precoder 262) will be described further below. The control unit 22 may, for example, perform predetermined control on the O-DU 26 (including the precoder 262), but may also perform predetermined control on functional units other than the O-DU 26. The signals precoded by the precoder 262 are output to the O-RU 30 as signals polarized as V polarization, H polarization, or the like for each layer.

[0032] Upon receiving a signal from the precoder 262 (O-DU 26), the O-RU 30 transmits a signal polarized as V polarization or H polarization for each layer from the corresponding subarray 10 to the second electronic device 2 (see FIG. 1). The O-RU 30 and each subarray 10 may be connected by a wireless transmission signal line. This wireless transmission signal line may be, for example, a line configured by hardware.

[0033] Next, the operation of the first electronic device 1 according to the embodiment will be described.

[0034] As described above, in multi-user MIMO, precoding is performed when spatial multiplexing is performed. Precoding here refers to the digital precoding described in FIG. 1. In this specification, such digital precoding is also simply referred to as "precoding." In addition, it is desirable to minimize the amount of calculation required to calculate the precoding weights in the above-described MIMO.

[0035] Furthermore, a line-of-site (LOS) environment (between two points in an unobstructed, direct line-of-sight location) may be assumed as a usage mode for base stations transmitting and receiving millimeter wave radio waves. In such a case, polarization multiplexing is effective for single-user MIMO transmission. Therefore, in the following description, dual polarization multiplexing is assumed for spatial multiplexing of single-user MIMO.

[0036] Hereinafter, the following two types of precoding will be described as processes executed by the precoder 262 shown in Fig. 2 in the first electronic device 1 according to one embodiment. For convenience, the two types of precoding described below will be referred to as "first type of precoding" and "second type of precoding."

[0037] <First Method of Precoding> In a first method of precoding according to one embodiment, spatial multiplexing and polarization multiplexing between users are simultaneously performed. That is, in the first method of precoding, multi-user multiplexing and polarization multiplexing are treated as a single channel matrix by regarding them as the same spatial multiplexing. The amount of calculation required for such precoding is O((2N)), where N is the number of UEs (second electronic devices 2). ３ ) = O(8N ３ ) The first method of precoding can be performed with a simple configuration and has relatively high performance. On the other hand, the first method of precoding tends to increase the calculation cost.

[0038] Fig. 3 is a diagram illustrating the operation of a system including a first electronic device 1 and a second electronic device 2 according to an embodiment. Fig. 3 shows an image of a precoding configuration of a first method.

[0039] 3 illustrates an example in which the first electronic device 1 includes four subarrays (subarray 10A, subarray 10B, subarray 10C, and subarray 10D). By using these four subarrays, the first electronic device 1 can communicate with four UEs, such as second electronic devices 2A, 2B, 2C, and 2D, via propagation path H. Meanwhile, in a system according to an embodiment, the first electronic device 1 may include any number of subarrays 10 and may be wirelessly connected to any number of second electronic devices 2.

[0040] In the first method of precoding, the number of spatial multiplexing operations to be performed is multi-user spatial multiplexing × polarization multiplexing. That is, in the case shown in FIG. 3, the number of layers is 4, which is the number of simultaneously connected UEs, and the number of polarization multiplexing operations is 2. Therefore, in the case shown in FIG. 3, the number of spatial multiplexing operations to be performed by the precoder 262 is 4 × 2 = 8. In this way, in the first method of precoding, multi-user multiplexing and polarization multiplexing are considered to be the same spatial multiplexing and are treated as one channel matrix. In the example shown in FIG. 3, the channel matrix to be calculated is an 8-row × 8-column matrix.

[0041] The algorithm for calculating the precoding weight in the first method may be ZF (Zero Forcing). For example, in the case of a channel matrix H representing a propagation path shown in FIG. 3, the precoding weight W is expressed by the following equation (1). －１ denotes the inverse matrix of H.

[0042] In the first method of precoding, the precoding of the first electronic device 1 (gNB) can also suppress inter-polarized interference. Therefore, in the first method of precoding, the postcoding of the second electronic device 2 (UE) is optional. In other words, in the first method of precoding, the postcoding of the second electronic device 2 (UE) may be performed, but even if it is not performed, it does not affect the communication performance in theory.

[0043] 3, polarization multiplexing using V (vertical) polarization and H (horizontal) polarization is used as an example. However, in one embodiment, polarization multiplexing using orthogonal polarizations other than V (vertical) polarization and H (horizontal) polarization may be used.

[0044] <Second Method Precoding> In a second method precoding according to one embodiment, only spatial multiplexing between users is performed. That is, in the second method precoding, suppression of polarization interference may be left to postcoding in the UE (second electronic device 2). The amount of calculation required for such precoding is O(2N ３ ) The amount of calculation required for precoding in the second method is 1 / 4 of that required for precoding in the first method, so the amount of calculation can be significantly reduced. On the other hand, in the case of precoding in the second method, polarization interference from different users may remain.

[0045] 4 is a diagram illustrating the operation of a system including a first electronic device 1 and a second electronic device 2 according to an embodiment. Fig. 4 illustrates a diagram illustrating the configuration of precoding according to a second method. In Fig. 4, descriptions similar to those in Fig. 3 may be appropriately simplified or omitted.

[0046] 4 also illustrates an example in which the first electronic device 1 includes four subarrays (subarray 10A, subarray 10B, subarray 10C, and subarray 10D), similar to FIG. 4 . By using these four subarrays, the first electronic device 1 can communicate with four UEs, such as second electronic devices 2A, 2B, 2C, and 2D, via propagation path H. Meanwhile, in a system according to an embodiment, the first electronic device 1 may include any number of subarrays 10 and may be wirelessly connected to any number of second electronic devices 2.

[0047] The second precoding method reduces the amount of computation required for signal processing by utilizing the feature of utilizing polarization multiplexing in single-user MIMO. In the second precoding method, the precoder 262 performs only spatial multiplexing between users. In this case, the precoder 262 does not need to perform inter-polarization signal processing. In the second precoding method, the precoder 262 may independently perform V-polarized multi-user multiplexing and H-polarized multi-user multiplexing. For example, as shown in FIG. 4 , the precoder 262V may perform V-polarized precoding. Meanwhile, the precoder 262H may perform H-polarized precoding. According to this processing, the size of the matrices handled by the precoder 262V (V-polarized precoding) and the precoder 262H (H-polarized precoding) is the number of subarrays 10 multiplied by the number of UEs (second electronic devices 2). In the case shown in FIG. 4, the number of subarrays 10×the number of UEs (second electronic devices 2) is 4×4.

[0048] The algorithm for calculating the precoding weights of the second method may be ZF (Zero Forcing). For example, consider decomposing the channel matrix H representing the propagation path shown in FIG. 4 as shown in the following equation (2). Here, H ＶＶ is the channel matrix for V-polarized wave transmission and V-polarized wave reception, and H ＶＨ is the channel matrix for H polarization transmission and V polarization reception, and H ＨＶ is the channel matrix for V polarization transmission and H polarization reception, and H ＨＨ is the channel matrix for H polarization transmission and H polarization reception.

[0049] In the case of the channel matrix H representing the propagation path shown in FIG. 4, the weight W of precoding for V polarization Ｖ is expressed as the following equation (3).

[0050] In addition, in the case of the channel matrix H representing the propagation path shown in FIG. 4, the weight W of the precoding for H polarization Ｈ is expressed as the following equation (4).

[0051] When performing precoding according to the second method, inter-polarized wave interference may be removed by postcoding in the second electronic device 2 (UE). The second electronic device 2 (UE) may employ minimum mean square error (MMSE) as an algorithm for removing inter-polarized wave interference. In general UEs, MMSE is often implemented as an algorithm for removing inter-polarized wave interference.

[0052] 4, polarization multiplexing using V (vertical) polarization and H (horizontal) polarization is used as an example. However, in one embodiment, polarization multiplexing using orthogonal polarizations other than V (vertical) polarization and H (horizontal) polarization may be used.

[0053] As described above, the first electronic device 1 (gNB) according to one embodiment may be a multi-user MIMO system that transmits single-user MIMO using polarization multiplexing. The first electronic device 1 according to one embodiment may include two types of precoding (algorithms) as a means for performing a downlink precoding function.

[0054] That is, as the first method of precoding, the first electronic device 1 may simultaneously perform spatial multiplexing and polarization multiplexing between users. In this case, the dimension of the matrix handled by the precoder 262 is the number of simultaneously connected UEs (second electronic device 2) multiplied by the number of polarization multiplexings. While the first method of precoding has relatively high performance, the calculation cost of the first method of precoding tends to be high.

[0055] Furthermore, as the precoding of the second method, only spatial multiplexing between users may be performed for each polarization. In this case, the dimension of the matrix handled by the precoder 262 is only the number of simultaneously connected UEs (second electronic devices 2). While the precoding of the second method has performance that depends on the scenario, the calculation cost of the precoding of the second method tends to be low.

[0056] In addition, in the first electronic device 1 according to one embodiment, the functions of the O-DU 26 including the precoder 262 may be implemented by software on general-purpose hardware.

[0057] The first electronic device 1 according to an embodiment may perform either the first scheme of precoding or the second scheme of precoding. Furthermore, the first electronic device 1 according to an embodiment may perform only the second scheme of precoding. Furthermore, the first electronic device 1 according to an embodiment may perform the first scheme of precoding or the second scheme by appropriately switching between them.

[0058] <Use of First and Second Precoding Methods> Next, conditions suitable for using the first and second precoding methods will be further described.

[0059] As described above, by using the second precoding method, it is possible to reduce the calculation cost and the processing load when performing precoding. On the other hand, there are conditions that are suitable for using the second precoding method. Therefore, in one embodiment, the first electronic device 1 may determine whether to use the first or second precoding method based on a cross-polarization power ratio (XPR), i.e., the ratio between the received power of the main polarization and the interference power of the other polarization.

[0060] FIG. 5 is a diagram showing an example of an environment in which radio waves propagate from a first electronic device to a second electronic device.

[0061] As shown in FIG. 5, it is assumed that there is a propagation path in a LOS environment and a propagation path in a NLOS (Non-LOS: between two points with no line of sight) environment between the first electronic device 1 (gNB) and the second electronic device 2 (UE). In the propagation path in the LOS environment shown in FIG. 5, the second electronic device 2 receives the radio waves transmitted from the first electronic device 1 as direct waves. In such a case, it is assumed that the XPR is affected by polarization rotation depending on the position of the second electronic device 2 (UE).

[0062] 5, the second electronic device 2 receives the radio wave transmitted from the first electronic device 1 as a reflected wave that is reflected and scattered by a reflecting object present in the propagation path. In such a case, it is assumed that the XPR is also affected by polarization rotation due to the reflection and scattering by the reflecting object.

[0063] The applicant simulated the operation of a multi-user MIMO system for downlink communications, assuming devices such as a first electronic device 1 (gNB) and a second electronic device 2 (UE). In this simulation, Rayleigh fading was assumed as the propagation path in the NLOS environment. In addition, the K factor (the ratio of the total power of the direct wave to the power of the reflected wave) was set to 22 dB. The gNB beamforming configuration was set to subarray hybrid beamforming. The number of subarrays provided by the gNB was set to 4, and the number of elements per subarray was set to 96 (4 vertically and 24 horizontally). The input SNR per element was set to -10 dB, and the maximum analog beamforming gain was set to approximately 39.65 dB. In other words, the desired SINR (Signal to Interference plus Noise Ratio) per layer was approximately 29.65 dB. Here, the desired SINR refers to the SINR when there is absolutely no interference from other UEs or other layers.

[0064] In addition, in this simulation, the number of multi-user connections was set to 4. Regarding the analog beamforming setting, the position of the UE connected to the subarray 10A was (Az, El) = (-13.3 °, 0.0 °), the position of the UE connected to the subarray 10B was (Az, El) = (-6.6 °, 0.0 °), the position of the UE connected to the subarray 10C was (Az, El) = (0.0 °, 0.0 °), and the position of the UE connected to the subarray 10D was (Az, El) = (6.6 °, 0.0 °). In addition, the number of candidate UEs per analog beam was set to 16. Here, Az is the azimuth angle (Azimuth), and El is the elevation angle (Elevation), and together they represent the direction as seen from the gNB.

[0065] Fig. 6 is a graph showing the results of the above-mentioned simulation. In Fig. 6, the horizontal axis represents SINR, and the vertical axis represents the probability (cumulative probability) of the existence of a UE and layer exhibiting an SINR equal to or less than the value on the horizontal axis. That is, in Fig. 6, the graph in which the value on the vertical axis (cumulative probability) increases sharply just before the horizontal axis reaches the desired SINR (29.65 dB in this example), the closer it is to the ideal case (a case in which there is absolutely no interference from other UEs and other layers).

[0066] In the case of XPR=10 shown in FIG. 6, the average SINR was 28.78, which is 0.87 smaller than the desired SINR (29.65 dB). In the case of XPR=20 shown in FIG. 6, the average SINR was 29.42, which is 0.23 smaller than the desired SINR (29.65 dB). In the case of XPR=+∞ shown in FIG. 6, the average SINR was 29.65, which is the same as the desired SINR (29.65 dB). In FIG. 6, the graph for XPR=+∞ and the graph for precoding using the first method almost overlap.

[0067] Therefore, in an environment where the XPR of the reflected wave is 10 dB or more, a high received SINR can be obtained, which is within 3 dB of the desired SINR on average. In such an environment, multi-user MIMO using precoding of the second method can be expected to improve throughput. Examples of such environments include squares and intersections of major streets.

[0068] On the other hand, when XPR = 0 as shown in Figure 6, the average SINR was 26.76. This is 2.90 smaller than the desired SINR (29.65 dB), a degradation of just under 3 dB. Also, when XPR = +∞ as shown in Figure 6, the average SINR was 24.75. This is 4.90 smaller than the desired SINR (29.65 dB).

[0069] Therefore, in an environment where the XPR of the reflected wave is generally less than 0 dB, a degradation of the received SINR of 3 dB or more from the desired SINR is observed on average. In an environment where such a degradation of 3 dB or more is observed, it is considered that an improvement in throughput cannot be expected without multi-user MIMO using the first precoding method. In other words, in such an environment, it is considered that an improvement in throughput can be expected with multi-user MIMO using the first precoding method. An example of such an environment is an environment where radio waves propagate between high-power buildings, such as a street in a busy downtown area. Note that the above "3 dB" is just one example of a threshold, and a different threshold may be used depending on the required quality.

[0070] From the above, the first electronic device 1 according to one embodiment can optimize the improvement of cell throughput and the reduction of power consumption by using the first precoding method and the second precoding method according to the desired environment. However, it should be noted that the above-mentioned XPR depends not only on the density of reflecting objects present in the environment but also on the material and / or shape of the reflecting objects.

[0071] <Selection of First or Second Precoding Scheme> Next, a further description will be given of an aspect in which the first electronic device 1 according to an embodiment selects either the first or second precoding scheme in accordance with a predetermined condition.

[0072] As described above, whether or not the use of the second method of precoding is appropriate can be determined by the XPR. However, it is expected that it is not necessarily easy to directly estimate the XPR in a practical system. Therefore, the first electronic device 1 (controller 22) according to one embodiment may indirectly determine whether or not the use of the second method of precoding is appropriate by using, for example, channel information estimated from the SRS.

[0073] When performing precoding using the second method, if a cross-polarized interference component from another second electronic device 2 (UE) is input to the second electronic device 2 (UE), the interference component may remain even after postcoding by the second electronic device 2 (UE). If the interference component remains even after postcoding by the second electronic device 2 (UE), this may cause a deterioration in SINR (i.e., a decrease in cell throughput). Therefore, the first electronic device 1 according to one embodiment may perform precoding utilizing channel reciprocity in a TDD system. In this case, the first electronic device 1 according to one embodiment may estimate the above-mentioned interference component from channel information estimated using an uplink SRS. Then, the first electronic device 1 according to one embodiment may select either the first method or the second method of precoding based on the magnitude of the estimated interference component.

[0074] 7 is a flowchart illustrating an example of an operation performed by the first electronic device 1 according to an embodiment. Hereinafter, an operation performed by the first electronic device 1 according to an embodiment to select whether to perform precoding according to the first scheme or precoding according to the second scheme will be described with reference to the flowchart illustrated in FIG.

[0075] 7 starts, the O-DU 26 of the first electronic device 1 acquires an SRS (step S11). Next, the O-DU 26 calculates channel information (channel matrix) based on the acquired SRS (step S12). Next, the O-DU 26 estimates the amount of interference components remaining after post-coding by the second electronic device 2 (UE) based on the calculated channel matrix (step S13). Information indicating the amount of interference components estimated by the O-DU 26 may be supplied to the control unit 22.

[0076] Then, the control unit 22 determines whether the amount of interference components estimated by the O-DU 26 is equal to or less than a predetermined value (or less than a predetermined value) (step S14). If the estimated amount of interference components is equal to or less than a predetermined value (or less than a predetermined value), the control unit 22 instructs the precoder 262 to perform precoding using a second method (step S15). On the other hand, if the estimated amount of interference components is not equal to or less than a predetermined value (or less than a predetermined value), the control unit 22 instructs the precoder 262 to perform precoding using a first method (step S16).

[0077] In the above-described operation, the operations from step S11 to step S13 have been described as being performed by the O-DU 26. However, the operations from step S11 to step S13 may also be performed by the control unit 22. In this case, the control unit 22 may acquire the SRS from the O-DU 26 in step S11. Furthermore, in step S14, the control unit 22 may determine, based on the amount of interference components estimated by the control unit 22, whether the amount of the interference components is equal to or less than a predetermined amount (or less than a predetermined amount).

[0078] 7, the first electronic device 1 according to an embodiment may operate as follows: First, as shown in the above formula (2), a channel matrix H representing a propagation path is defined. In the above formula (2), each component H ＶＶ , H ＶＨ , H ＨＶ , and H ＨＨ are as described above. Next, the following equation (5) or equation (6) is calculated.

[0079] H in the above formula (5) ＶＶ －１ and H in the above formula (6) ＨＨ －１corresponds to the precoding weight in the precoding of the second scheme. The first electronic device 1 (controller 22) according to an embodiment may multiply this weight by a matrix representing cross-polarization interference. Through such processing, the first electronic device 1 according to an embodiment can estimate the amount of interference remaining after postcoding of the second electronic device 2 (UE) when the precoding of the second scheme is used.

[0080] Specifically, the first electronic device 1 (controller 22 thereof) according to an embodiment may select the second precoding scheme if the following formula (7) is satisfied. On the other hand, if the above formula (7) is not satisfied, the first electronic device 1 (controller 22 thereof) according to an embodiment may select the first precoding scheme.

[0081] In the above equation (7), the symbols shown in the following equation (8) represent the i and j components of the matrix shown in the following equation (9).

[0082] In addition, in the above equation (7), α is a parameter determined by the desired SINR. Specifically, α may be a real number equal to or greater than 1. On the other hand, α may be changed depending on the situation, such as the communication environment.

[0083] The first electronic device 1 (controller 22 thereof) according to an embodiment may determine whether to perform precoding according to the first method or the second method by performing calculations for all i and k using the above formula (7). Also, the first electronic device 1 (controller 22 thereof) according to an embodiment may determine whether to perform precoding according to the first method or the second method by performing calculations for some i and k using the above formula (7).

[0084] As described above, the first electronic device 1 includes a plurality of subarrays each including a plurality of antenna elements, and performs multi-user MIMO communication with a plurality of second electronic devices 2. The first electronic device 1 may include a precoder 262 that performs precoding by independently performing spatial multiplexing for each of orthogonal polarizations among the plurality of second electronic devices 2. The first electronic device 1 may transmit signals that have been precoded by the precoder 262 to the plurality of second electronic devices 2.

[0085] In one embodiment, the precoder 262 performs spatial multiplexing among the plurality of second electronic devices 2 independently for each orthogonal polarization, but may perform precoding of a second scheme that does not perform polarization multiplexing of orthogonal polarizations. In this case, the first electronic device 1 may transmit signals that have been precoded according to the second scheme by the precoder 262 to the plurality of second electronic devices 2.

[0086] In addition, in one embodiment, the precoder 262 may perform precoding according to a second scheme or precoding according to a first scheme that is different from the precoding according to the second scheme. In this case, the first electronic device 1 may transmit, to a plurality of second electronic devices 2, signals that have been precoded according to the first scheme or the second scheme by the precoder 262.

[0087] In one embodiment, the precoder 262 may perform spatial multiplexing among the plurality of second electronic devices 2 and polarization multiplexing of the orthogonal polarizations as the first type of precoding.

[0088] In one embodiment, the first electronic device 1 may include a control unit 22 that controls the first electronic device 1 to switch between the first precoding method and the second precoding method.

[0089] The control unit 22 may also control switching between the first precoding method and the second precoding method based on predetermined conditions. Furthermore, the control unit 22 may control switching between the first precoding method and the second precoding method based on the communication environment between the first electronic device 1 and the second electronic device 2. Furthermore, the control unit 22 may control switching between the first precoding method and the second precoding method based on the magnitude of interference components remaining after postcoding by the second electronic device 2.

[0090] <Architecture of First Electronic Device 1> Next, an example of architecture for realizing the first electronic device 1 according to an embodiment will be further described.

[0091] The first electronic device 1 according to the embodiment described above is compatible with a virtual Radio Access Network (vRAN) system. According to the vRAN system, the DU function is implemented as a virtualized application running on a virtualized board, enabling optimization of radio resource management and / or automatic control of operation. For example, if the first electronic device 1 according to the embodiment described above were implemented on dedicated hardware such as an FPGA, two fixed circuits would be implemented, one for the first method precoding function and one for the second method precoding function. In contrast, with vRAN, the precoding function is treated like an application, i.e., it is possible to download only the method to be used. Therefore, adopting vRAN is expected to reduce the implementation cost of the device.

[0092] The first electronic device 1 according to an embodiment may, for example, in an RIC (RAN Intelligent Controller)-based architecture in an O-RAN, cause the RIC to execute a function of determining a means of executing precoding. In one embodiment, log collection for determination and instructions on the execution means may be performed between the O-DU having the precoding function and the RIC that determines the means of executing precoding. In this way, the first electronic device 1 according to an embodiment may at least partially include a functional unit configured based on the O-RAN architecture.

[0093] Furthermore, there are two types of RIC: Non-RT RIC (Non Realtime RIC), which performs control at a relatively long cycle of one second or more, and Near-RT RIC (Near Realtime RIC), which performs control at a relatively short cycle of less than one second. Therefore, in the first electronic device 1 according to one embodiment, the characteristics of each of these RICs may be utilized when determining and / or selecting whether to use the first precoding method or the second precoding method.

[0094] For example, the environment in which the first electronic device 1 is installed is considered to be one in which temporal fluctuations tend to be relatively low. When determining and / or selecting whether to use the first precoding method or the second precoding method based on such a situation in which fluctuations are relatively low, the first electronic device 1 according to one embodiment may perform control using Non-RT RIC. On the other hand, the movement of the second electronic device 2 (UE) is considered to be one in which temporal fluctuations tend to be relatively high. When determining and / or selecting whether to use the first precoding method or the second precoding method based on such a situation in which fluctuations are relatively high, the first electronic device 1 according to one embodiment may perform control using Near-RT RIC.

[0095] In one embodiment, the control unit 22 of the first electronic device 1 may switch between control using Non-RT RIC and control using Near-RT RIC based on predetermined determination information. In this case, the predetermined determination information may be, for example, determination information acquired by the control unit 22 shown in FIG. 2 from the O-DU 26. The predetermined determination information may be, for example, information used by the control unit 22 to determine whether the amount of interference components is equal to or less than a predetermined amount (less than a predetermined amount) in step S14 of FIG. 7, i.e., information indicating the amount of interference components estimated in step S13.

[0096] The above-described determination information may be referenced, for example, at regular intervals, and if the temporal variation in the determination result is found to be greater than or equal to a predetermined value, the first electronic device 1 according to an embodiment may execute control using Near-RT RIC. On the other hand, if the temporal variation in the determination result is less than or equal to a predetermined value (or less), the first electronic device 1 according to an embodiment may execute control using Non-RT RIC.

[0097] In this way, the control unit 22 of the first electronic device 1 may determine the control means (Near-RT RIC or Non-RT RIC) to be used when determining and / or selecting the precoding method, for example, by acquiring predetermined determination information from the O-DU 26. In this case, the control unit 22 of the first electronic device 1 may instruct the O-DU 26, for example, of the determined control means (Near-RT RIC or Non-RT RIC).

[0098] As described above, the first electronic device 1 according to an embodiment can determine and / or select a precoding method depending on the surrounding environment in which the device is installed and / or conditions such as radio wave propagation. Therefore, the first electronic device 1 according to an embodiment can optimize performance (cell throughput) and computational costs. That is, the first electronic device 1 according to an embodiment can reduce the processing load when performing precoding in MIMO. Furthermore, the first electronic device 1 according to an embodiment can be expected to optimize power consumption by optimizing performance (cell throughput) and computational costs.

[0099] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art would easily be able to make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are within the scope of the present disclosure. For example, functions included in each component or step can be rearranged so as not to cause logical inconsistencies, and multiple components or steps can be combined or divided into one. Although the embodiments of the present disclosure have been described primarily in terms of an apparatus, the embodiments of the present disclosure can also be realized as a method including steps executed by each component of the apparatus. The embodiments of the present disclosure can also be realized as a method, a program executed by a processor included in an electronic device, or a storage medium or recording medium on which a program is recorded. It should be understood that these are also encompassed within the scope of the present disclosure.

[0100] The first electronic device 1 according to an embodiment may be implemented with analog beamforming, hybrid beamforming, or digital beamforming.

[0101] As described above, the first electronic device 1 according to an embodiment may perform either the first scheme of precoding or the second scheme of precoding. Furthermore, the first electronic device 1 according to an embodiment may perform only the second scheme of precoding. Furthermore, the first electronic device 1 according to an embodiment may perform the first scheme of precoding or the second scheme by appropriately switching between them.

[0102] Furthermore, the first electronic device 1 according to an embodiment may be capable of performing precoding using a plurality of methods. In this case, the first electronic device 1 according to an embodiment may perform precoding using a plurality of methods by appropriately switching between the methods. For example, the first electronic device 1 according to an embodiment may perform precoding using a plurality of methods by switching between the methods based on a predetermined condition. Furthermore, the precoding using a plurality of methods may include at least one of a first method of precoding and a second method of precoding.

[0103] The above-described embodiments are not limited to implementation as the first electronic device 1. For example, the above-described embodiments may be implemented as a system including the first electronic device 1. Furthermore, the above-described embodiments may be implemented as a system including the first electronic device 1 and the second electronic device 2. Furthermore, the above-described embodiments may be implemented as, for example, a control method for the first electronic device 1 or a control method for a device such as a system including the first electronic device 1. Furthermore, the above-described embodiments may be implemented as, for example, a program executed by a device such as the first electronic device 1 or a system including the first electronic device 1, or an information processing device (e.g., a computer). Furthermore, in the technology disclosed herein, all of the components of the first electronic device 1 and / or the system including the first electronic device 1 do not need to be contained in a single housing. For example, the controllers and / or memory units of the components of the first electronic device 1 and / or the system including the first electronic device 1 may be connected to each other via a network that is wired, wireless, or a combination thereof.

[0104] The above has described an electronic device according to an embodiment, but the electronic device, system, control method, and / or program according to an embodiment may be implemented, for example, as follows, as long as there is no physical or logical contradiction. [Supplementary Note 1] An electronic device that includes a plurality of subarrays each including a plurality of antenna elements and performs multi-user MIMO communication with a plurality of other electronic devices, the electronic device further including a precoder that performs precoding by independently performing spatial multiplexing for each orthogonal polarization among the plurality of other electronic devices, and transmits signals precoded by the precoder to the plurality of other electronic devices. [Supplementary Note 2] The electronic device according to Supplementary Note 1, wherein the precoder performs spatial multiplexing for each orthogonal polarization among the plurality of other electronic devices independently, but performs precoding of a second scheme that does not perform polarization multiplexing of the orthogonal polarization, and transmits signals precoded by the precoder to the plurality of other electronic devices. [Supplementary Note 3] The electronic device according to Supplementary Note 2, wherein the precoder performs precoding according to the second scheme or precoding according to a first scheme different from the precoding according to the second scheme, and transmits a signal precoded according to the first scheme or the second scheme by the precoder to the plurality of other electronic devices. [Supplementary Note 4] The electronic device according to Supplementary Note 3, wherein the precoder performs spatial multiplexing among the plurality of other electronic devices and polarization multiplexing of the orthogonal polarizations as the precoding according to the first scheme. [Supplementary Note 5] The electronic device according to Supplementary Note 3 or 4, further comprising a control unit that controls to switch between the precoding according to the first scheme and the precoding according to the second scheme. [Supplementary Note 6] The electronic device according to Supplementary Note 5, wherein the control unit controls to switch between the precoding according to the first scheme and the precoding according to the second scheme based on a predetermined condition. [Supplementary Note 7] The electronic device according to Supplementary Note 6, wherein the control unit controls to switch between the precoding according to the first scheme and the precoding according to the second scheme based on a communication environment between the electronic device and the other electronic devices.[Supplementary Note 8] The electronic device according to Supplementary Note 6 or 7, wherein the control unit controls to switch between the first scheme of precoding and the second scheme of precoding based on the magnitude of an interference component remaining after postcoding by the other electronic device. [Supplementary Note 9] The electronic device according to any of Supplementary Notes 6 to 8, wherein the control unit determines whether to select the first scheme of precoding or the second scheme of precoding based on Non-RT RIC or Near-RT RIC in O-RAN architecture. [Supplementary Note 10] The electronic device according to Supplementary Note 9, wherein the control unit determines whether to use the Non-RT RIC or Near-RT RIC for the determination based on predetermined determination information. [Supplementary Note 11] A system including an electronic device and a plurality of other electronic devices, wherein the electronic device has a plurality of subarrays including a plurality of antenna elements, and performs multi-user MIMO communication with the plurality of other electronic devices, and a precoder that performs precoding by independently performing spatial multiplexing for each orthogonal polarization between the plurality of other electronic devices, and transmits signals precoded by the precoder to the plurality of other electronic devices. [Supplementary Note 12] A control method for an electronic device that has a plurality of subarrays including a plurality of antenna elements and performs multi-user MIMO communication with a plurality of other electronic devices, comprising: performing precoding by independently performing spatial multiplexing for each orthogonal polarization between the plurality of other electronic devices, and transmitting the precoded signals to the plurality of other electronic devices. [Supplementary Note 13] A program that causes an electronic device that has a plurality of subarrays including a plurality of antenna elements and performs multi-user MIMO communication with a plurality of other electronic devices to execute: performing precoding by independently performing spatial multiplexing for each orthogonal polarization between the plurality of other electronic devices, and transmitting the precoded signals to the plurality of other electronic devices.

[0105] 1 First electronic device (base station (gNB)) 10 Subarray (antenna array) 20 Information processing device (general-purpose server) 22 Control unit 24 O-CU (O-RAN Centralized Unit) 26 O-DU (O-RAN Distributed Unit) 262 Precoder 30 O-RU (O-RAN Radio Unit as defined by O-RAN) 2 Second electronic device (terminal (UE))

Claims

1. An electronic device that has multiple subarrays, each including multiple antenna elements, and that performs multi-user MIMO communication with multiple other electronic devices, further comprising a precoder that performs precoding by independently performing spatial multiplexing between the multiple other electronic devices for each of orthogonal polarizations, and transmits signals that have been precoded by the precoder to the multiple other electronic devices.

2. The electronic device according to claim 1, wherein the precoder performs spatial multiplexing between the plurality of other electronic devices independently for each orthogonal polarization, but performs precoding of a second method in which polarization multiplexing of the orthogonal polarization is not performed, and transmits the signal precoded by the precoder according to the second method to the plurality of other electronic devices.

3. The electronic device according to claim 2, wherein the precoder performs precoding according to the second method or precoding according to a first method different from the precoding according to the second method, and transmits a signal that has been precoded according to the first method or the second method by the precoder to the plurality of other electronic devices.

4. The electronic device according to claim 3, wherein the precoder performs spatial multiplexing among the plurality of other electronic devices and polarization multiplexing of the orthogonal polarizations as the first type of precoding.

5. The electronic device according to claim 3 or 4, further comprising a control unit that controls switching between the first precoding method and the second precoding method.

6. The electronic device according to claim 5, wherein the control unit controls the switching between the first precoding method and the second precoding method based on a predetermined condition.

7. The electronic device according to claim 6, wherein the control unit controls to switch between the first method of precoding and the second method of precoding based on the communication environment between the electronic device and the other electronic device.

8. The electronic device described in claim 6 or 7, wherein the control unit controls to switch between the first method of precoding and the second method of precoding based on the magnitude of the interference component remaining after postcoding by the other electronic device.

9. The electronic device according to any one of claims 6 to 8, wherein the control unit determines whether to select the first scheme of precoding or the second scheme of precoding based on a Non-RT RIC or a Near-RT RIC in an O-RAN architecture.

10. The electronic device according to claim 9, wherein the control unit determines whether to use the Non-RT RIC or the Near-RT RIC based on predetermined determination information.

11. A system including an electronic device and a plurality of other electronic devices, wherein the electronic device has a plurality of subarrays each including a plurality of antenna elements, and performs multi-user MIMO communication with the plurality of other electronic devices, and a precoder that performs precoding by independently performing spatial multiplexing between the plurality of other electronic devices for each of orthogonal polarizations, and transmits signals precoded by the precoder to the plurality of other electronic devices.

12. A control method for an electronic device that has a plurality of subarrays each including a plurality of antenna elements and that performs multi-user MIMO communication with a plurality of other electronic devices, the control method comprising: a step of performing precoding by independently performing spatial multiplexing between the plurality of other electronic devices for each of orthogonal polarizations; and a step of transmitting the precoded signals to the plurality of other electronic devices.

13. A program that causes an electronic device that has multiple subarrays each including multiple antenna elements and that performs multi-user MIMO communication with multiple other electronic devices to perform the following steps: performing precoding to perform spatial multiplexing between the multiple other electronic devices independently for each orthogonal polarization; and transmitting the precoded signals to the multiple other electronic devices.

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