Wireless communication systems, wireless communication methods, programs, base stations

Abstract

This technology provides sensing capabilities while maintaining communication quality. [Solution] Base station 100 transmits a sensing reference signal. Base station 100 receives feedback information from each of the first mobile stations 200a to the Nth mobile station 200n and calculates the appropriateness based on a value indicating the reception status. If the appropriateness is greater than the maximum value, base station 100 reduces the number of antenna ports that transmit the sensing reference signal, and if the appropriateness is less than the minimum value, base station 100 increases the number of antenna ports that transmit the sensing reference signal.

Description

[Technical Field]

[0001] The present invention relates to wireless communication technology, and in particular to a wireless communication system that transmits reference signals, a wireless communication method, a program, and a base station. [Background Art]

[0002] One example of a wireless communication system is LTE (Long Term Evolution). An LTE base station has an array antenna provided with a plurality of antenna elements. Further, in LTE, a plurality of antenna elements are grouped and used as antenna ports, whereby an optimal antenna port configuration is realized (see, for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2015-33097 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] The 3GPP (3rd Generation Partnership Project) (registered trademark) is conducting technical studies on Beyond 5G / 6G. One of the technologies being considered by the 3GPP (registered trademark) is ISAC (Integrated Sensing and Communication). Even before 5G, mobile station location estimation was performed. ISAC aims to integrate communication and sensing functions by adding a new function to sense objects such as people, cars, and bicycles that do not have mobile stations using radio waves, in response to the increasing frequency of mobile communications. Furthermore, 5G base stations employ Massive MIMO (Multiple-Input and Multiple-Output) with tens to hundreds of antennas. For Beyond 5G / 6G (hereinafter referred to as "6G") base stations, Extreme MIMO with thousands of antennas is being considered. 6G base stations are expected to have thousands of antennas, and efficient use of antennas will be necessary in integrating communication and sensing.

[0005] This invention was made in view of these circumstances, and its purpose is to provide a technology that performs sensing while maintaining communication quality. [Means for solving the problem]

[0006] To solve the above problems, a wireless communication system according to one aspect of the present invention comprises a base station having a plurality of antenna ports and a plurality of mobile stations communicating with the base station. The base station transmits a sensing reference signal to the plurality of mobile stations, each of the plurality of mobile stations receives the sensing reference signal, calculates a value indicating the reception status of the sensing reference signal, and transmits feedback information including the value indicating the reception status to the base station, the base station receives the feedback information from each of the plurality of mobile stations and calculates an appropriateness score based on the values ​​indicating the reception status of each of the plurality of mobile stations, the base station decreases the number of antenna ports transmitting the sensing reference signal when the appropriateness score is greater than the maximum value, and the base station increases the number of antenna ports transmitting the sensing reference signal when the appropriateness score is less than the minimum value.

[0007] Another aspect of the present invention is a wireless communication method. This method is a wireless communication method in a wireless communication system comprising a base station having a plurality of antenna ports and a plurality of mobile stations communicating with the base station, wherein the base station transmits a sensing reference signal to the plurality of mobile stations, each of the plurality of mobile stations receives the sensing reference signal, calculates a value indicating the reception status of the sensing reference signal, and transmits feedback information including the value indicating the reception status to the base station, the base station receives the feedback information from each of the plurality of mobile stations and calculates an appropriateness based on the values ​​indicating the reception status of each of the plurality of mobile stations, the base station decreases the number of antenna ports transmitting the sensing reference signal when the appropriateness is greater than the maximum value, and the base station increases the number of antenna ports transmitting the sensing reference signal when the appropriateness is less than the minimum value.

[0008] A further aspect of the present invention is a base station. This base station has a plurality of antenna ports that transmit a sensing reference signal to a mobile station and receive feedback information, wherein feedback information containing a value indicating the reception status of the sensing reference signal is transmitted from the mobile station, and upon receiving the feedback information, the appropriateness is calculated based on the value indicating the reception status of the mobile station, and if the appropriateness is greater than the maximum value, the number of antenna ports that transmit the sensing reference signal is reduced, and if the appropriateness is less than the minimum value, the number of antenna ports that transmit the sensing reference signal is increased.

[0009] A further aspect of the present invention is a wireless communication method. This method is a wireless communication method at a base station having multiple antenna ports that transmit a sensing reference signal to a mobile station and receive feedback information, wherein the feedback information transmitted from the mobile station includes a value indicating the reception status of the sensing reference signal, and upon receiving the feedback information, a degree of appropriateness is calculated based on the value indicating the reception status of the mobile station, and if the degree of appropriateness is greater than the maximum value, the number of antenna ports that transmit the sensing reference signal is reduced, and if the degree of appropriateness is less than the minimum value, the number of antenna ports that transmit the sensing reference signal is increased.

[0010] Furthermore, any combination of the above components, as well as conversions of the expression of the present invention between methods, apparatus, systems, recording media, computer programs, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0011] According to the present invention, sensing can be performed while maintaining communication quality. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram showing the configuration of the wireless communication system in Example 1. [Figure 2] This diagram shows the configuration of the base station shown in Figure 1. [Figure 3] This diagram shows the configuration of the antenna section in Figure 2. [Figure 4] It is a diagram showing the configuration of the mobile station in FIG. 1. [Figure 5] It is a flowchart showing a communication procedure by the wireless communication system in FIG. 1. [Figure 6] FIGS. 6(a)-(d) are diagrams showing antenna port configuration candidates in FIG. 5. [Figure 7] It is a flowchart showing a procedure for determining an antenna port configuration in FIG. 5. [Figure 8] It is a flowchart showing a procedure for determining an antenna port configuration in FIG. 7. [Figure 9] It is a flowchart showing another procedure for determining an antenna port configuration in FIG. 7. [Figure 10] It is a flowchart showing another communication procedure by the wireless communication system in FIG. 1. [Figure 11] It is a flowchart showing an update procedure for the number of antenna ports by the wireless communication system according to Embodiment 2. [Figure 12] FIGS. 12(a)-(c) are diagrams showing an example of antenna port allocation according to Embodiment 2. [Figure 13] FIGS. 13(a)-(c) are diagrams showing an example of antenna port allocation after change according to Embodiment 2. [Figure 14] FIGS. 14(a)-(b) are diagrams showing another example of antenna port allocation after change according to Embodiment 2. MODE FOR CARRYING OUT THE INVENTION

[0013] (Embodiment 1) FIG. 1 shows a configuration of a wireless communication system 1000. The wireless communication system 1000 includes a base station 100, a first mobile station 200a, a second mobile station 200b, and an N-th mobile station 200n, which are collectively referred to as a plurality of mobile stations 200. The base station 100 communicates with each of the plurality of mobile stations 200 and performs sensing.

[0014] FIG. 2 shows a configuration of a base station 100. The base station 100 includes a channel coding unit 110, a modulation unit 112, a layer mapping unit 114, an antenna mapping unit 116, a resource element mapping unit 118, a digital beamforming unit 120, a transmission signal processing unit 122, a duplexer unit 124, an antenna unit 130, an antenna control unit 132, a reception signal processing unit 140, a signal separation unit 142, a channel state information acquisition unit 144, and an antenna port configuration determination unit 150.

[0015] As communication processing, the base station 100 executes downlink processing from the base station 100 to a mobile station 200 and uplink processing from the mobile station 200 to the base station 100. The base station 100 also executes sensing processing for sensing the position of an object. In the downlink processing, transmission data for communication (hereinafter referred to as a "communication data signal") is coded by the channel coding unit 110, modulated by the modulation unit 112, mapped to layers by the layer mapping unit 114, and mapped to antenna ports by the antenna mapping unit 116. A reference signal for communication (hereinafter referred to as a "communication reference signal") is also mapped to antenna ports by the antenna mapping unit 116.

[0016] The signal mapped to the antenna ports is mapped to resource elements by the resource element mapping unit 118, beamformed by the digital beamforming unit 120, subjected to processing such as inverse Fourier transform, addition of a cyclic prefix, and frequency conversion by the transmission signal processing unit 122, and transmitted from the antenna unit 130 via the duplexer unit 124.

[0017] As part of the uplink processing, signals from each mobile station 200 are received by the antenna unit 130, and via the duplexer unit 124, the received signal processing unit 140 performs processing such as frequency conversion to baseband, removal of cyclic prefix, and fast Fourier transform, and the signal separation unit 142 separates them into a reference signal, a control signal, and a user signal. In addition, the channel status information acquisition unit 144 performs channel estimation based on the separated reference signal and control signal, demodulates and decodes the feedback information from the mobile station 200 that received the communication reference signal (hereinafter referred to as "communication feedback information"), and outputs the communication feedback information to the antenna port configuration determination unit 150.

[0018] For the sensing process, the transmission data for sensing (hereinafter referred to as "sensing data signal") is processed in the same way as the communication data signal, and the reference signal for sensing (hereinafter referred to as "sensing reference signal") is processed in the same way as the communication reference signal. Furthermore, the feedback information from the mobile station 200 that receives the sensing reference signal (hereinafter referred to as "sensing feedback information") is processed in the same way as the communication feedback information. In addition, sensing is performed based on the received sensing data signal that has been reflected by the object after transmission. Since known sensing techniques can be used, a detailed explanation is omitted here.

[0019] In the above configuration, the antenna section 130 is a MIMO antenna composed of multiple antenna ports. Figure 3 shows the configuration of the antenna section 130. The MIMO antenna includes multiple antenna ports 160, and each antenna port 160 includes multiple antenna elements 162. Here, there are 16 antenna ports 160, and each antenna port 160 contains 16 antenna elements 162. There can be one or more antenna ports 160, and each antenna port 160 can contain one or more antenna elements 162. The number of antenna elements 162 included in one antenna port 160 may be variable. Also, there may be unused antenna elements 162. Each antenna port 160 is assigned an antenna port index. Here, antenna port indices from "0" to "15" are used in raster order from the top left.

[0020] The communication reference signal and the sensing reference signal are placed in different resource blocks, subframes, frames, and antenna ports 160. Furthermore, by transmitting the sensing reference signal and the communication reference signal at different times, the effects of fading or interference are reduced, allowing the mobile station 200 to distinguish between them. Additionally, by transmitting the sensing reference signal and the communication reference signal at different frequencies, spectral efficiency is improved while allowing the mobile station 200 to distinguish between them. Here, the communication reference signal and the sensing reference signal are assumed to be placed in different subframes and frames, but this is not limited to this. They may be placed in the same subframe and frame. Also, while it is assumed that the communication reference signal and the sensing reference signal are transmitted at different times and frequencies, this is not limited to this; they may be transmitted at the same time and frequency as long as either the time or frequency is different.

[0021] In Figure 2, the antenna port configuration determination unit 150 determines the configuration of the antenna port 160 for assigning sensing reference signals and communication reference signals. The antenna mapping unit 116 and the antenna control unit 132 then perform processing according to the configuration of the antenna port 160 determined by the antenna port configuration determination unit 150.

[0022] Figure 4 shows the configuration of the mobile station 200. The mobile station 200 includes a channel coding unit 210, a modulation unit 212, a layer mapping unit 214, an antenna mapping unit 216, a resource element mapping unit 218, a digital beamforming unit 220, a transmit signal processing unit 222, a duplexer unit 224, an antenna unit 230, a receive signal processing unit 240, a signal separation unit 242, a channel state information evaluation unit 244, an antenna port configuration selection unit 250, and a feedback information generation unit 252.

[0023] The mobile station 200 also performs communication processing, including downlink processing from the base station 100 to the mobile station 200 and uplink processing from the mobile station 200 to the base station 100. On the other hand, the mobile station 200 does not perform sensing processing, but it does perform response processing for sensing reference signals received from the base station 100.

[0024] As part of the downlink processing, the signal from the base station 100 is received by the antenna unit 230, and via the duplexer unit 224, the received signal processing unit 240 performs processing such as frequency conversion to baseband, removal of cyclic prefix, and fast Fourier transform, and the signal separation unit 242 separates it into a reference signal, a control signal, and a user signal. In addition, the channel state information evaluation unit 244 evaluates the channel state based on the communication reference signal, and the antenna port configuration selection unit 250 selects the antenna port configuration based on the result of the channel state evaluation. The feedback information generation unit 252 channels encode, modulates, and layers-maps the communication feedback information based on the selected antenna port configuration, and outputs the communication feedback information to the antenna mapping unit 216.

[0025] As part of the uplink processing, the transmission data for communication (hereinafter referred to as "communication data signal") is encoded by the channel coding unit 210, modulated by the modulation unit 212, mapped to layers by the layer mapping unit 214, and mapped to antenna ports by the antenna mapping unit 216. In addition, the reference signal and communication feedback information are mapped to antenna ports by the antenna mapping unit 216.

[0026] The signal mapped to the antenna port is mapped to a resource element in the resource element mapping unit 218, beamformed in the digital beamforming unit 220, and then processed in the transmission signal processing unit 222, including inverse Fourier transform, addition of cyclic prefix, and frequency conversion, before being transmitted from the antenna unit 230 via the duplexer unit 224.

[0027] As part of the response processing, the channel state information evaluation unit 244 evaluates the channel state based on the sensing reference signal, and the antenna port configuration selection unit 250 selects an antenna port configuration based on the results of the channel state evaluation. The feedback information generation unit 252 channels encode, modulates, and layers the communication feedback information based on the selected antenna port configuration, and outputs the sensing feedback information to the antenna mapping unit 216.

[0028] This configuration can be implemented in hardware terms using the CPU, memory, and other LSIs of any computer, and in software terms using programs loaded into memory, but here we are depicting the functional blocks that are realized through the cooperation of these components. Therefore, it will be understood by those skilled in the art that these functional blocks can be implemented in various ways using hardware alone, software alone, or a combination of both.

[0029] The following describes the process for assigning the communication reference signal and the sensing reference signal of the wireless communication system 1000 to the antenna port 160. Figure 5 is a flowchart showing the communication procedure by the wireless communication system 1000. The antenna port configuration determination unit 150 of the base station 100 determines a provisional antenna port ratio to be assigned to the communication reference signal and the sensing reference signal (S10). Here, the provisional antenna port ratio to be assigned to the communication reference signal and the sensing reference signal is set to "3:1", but it is not limited to this. Other ratios may be used, or multiple ratios may be selected.

[0030] The antenna port configuration determination unit 150 selects candidate antenna port configurations based on a provisional antenna port ratio (S11). Figures 6(a)-(d) show candidate antenna port configurations in the antenna unit 130. These are examples of antenna port configurations for a MIMO antenna when the antenna port ratio is "3:1". Antenna port configurations corresponding to each antenna port ratio are predefined. Antenna ports 160 to which sensing reference signals are assigned are indicated by diagonal lines, and communication reference signals are assigned to the other antenna ports 160.

[0031] In Figure 6(a), the antenna port indices of the antenna port 160 to which the sensing reference signal is assigned are "0", "3", "12", and "15", while the antenna port indices of the antenna port 160 to which the communication reference signal is assigned are "1", "2", ..., and "14". In other words, in Figure 6(a), the antenna port 160 to which the sensing reference signal is assigned is positioned so that the distance between the sensing reference signals is maximized. Therefore, the antenna port 160 to which the communication reference signal is assigned is positioned near the center.

[0032] In Figure 6(b), the antenna ports 160 assigned to the sensing reference signal are concentrated in the center, while the antenna ports 160 assigned to the communication reference signal are located around them. In Figure 6(c), the antenna ports 160 assigned to the sensing reference signal are located at a downward sloping right, while the antenna ports 160 assigned to the communication reference signal are located near the upper right and lower left. In Figure 6(d), the antenna ports 160 assigned to the sensing reference signal are arranged horizontally.

[0033] Here, as an example, four antenna port configurations are defined when the antenna port ratio is "3:1", but it is not limited to this. It is sufficient to define one or more antenna port configurations. The antenna port configuration determination unit 150 selects from these the antenna port configuration in Figure 6(a) (hereinafter also referred to as the "first pattern") and the antenna port configuration in Figure 6(b) (hereinafter also referred to as the "second pattern"). In other words, from among the multiple antenna ports 160, the first pattern and the second pattern, which are different from each other, are selected as combinations (antenna port configurations) of antenna port 160 to which communication reference signals are assigned and antenna port 160 to which sensing reference signals are assigned. Here, two candidate antenna port configurations are selected from the defined antenna port configurations, but it is not limited to this. One or three or more antenna port configurations may also be selected. Return to Figure 5.

[0034] The antenna port configuration determination unit 150 of the base station 100 communicates bidirectionally with multiple mobile stations 200 to determine the antenna port ratio and antenna port configuration (S12). To explain this process in detail, Figure 7 is also used here. Figure 7 is a flowchart of the procedure for determining the antenna port configuration. Based on the communication antenna port configuration selected by the antenna port configuration determination unit 150, the base station 100 transmits a communication reference signal from the communication antenna port 160 at a predetermined frequency and time interval for communication (S100). Also, based on the sensing antenna port configuration selected by the antenna port configuration determination unit 150, the base station 100 transmits a sensing reference signal from the sensing antenna port 160 at a predetermined frequency and time interval for sensing (S101). In other words, the base station 100 transmits the communication reference signal and sensing reference signal assigned to the antenna port 160 using the first pattern to multiple mobile stations 200. Specifically, sensing reference signals are assigned to and transmitted via antenna ports 0, 3, 12, and 15, while communication reference signals are assigned to and transmitted via antenna ports 1, 2, 4-11, 13, and 14.

[0035] Here, the predetermined frequency for sensing is the frequency of a predetermined number of consecutive subcarriers, but is not limited thereto. The predetermined time interval for sensing may be periodic or aperiodic. Furthermore, considering compatibility with the 3GPP® standard and simplicity without additional processing such as coding or modulation, the sensing reference signal is CSI-RS (Channel State Information Reference Signal), but is not limited thereto. However, the mobile station 200 shall be notified of discrimination information that can distinguish whether a signal is a sensing reference signal or a communication reference signal. For example, the base station 100 notifies the mobile station 200 of the transmission period, offset, time domain position, and frequency domain position of the sensing reference signal, for example, using the PDCCH (Physical Downlink Control Channel), so that the base station 100 and the mobile station 200 can share the arrangement of the sensing reference signal.

[0036] Each of the multiple mobile stations 200 receives a first pattern sensing reference signal from the base station 100 and calculates the signal-to-interference-plus-noise ratio (SINR) as a value indicating the reception status of the sensing reference signal. Each of the multiple mobile stations 200 also receives a first pattern communication reference signal from the base station 100 and calculates the rank indicator (RI), precoding matrix indicator (PMI), and channel quality indicator (CQI) as the reception quality of the communication reference signal. Here, if the reception quality of the communication reference signal for the first pattern is called the "first value," the value indicating the reception status of the sensing reference signal for the first pattern is called the "second value." In other words, each of the multiple mobile stations 200 receives the communication reference signal and the sensing reference signal assigned to the antenna port using the first pattern, calculates the first value based on the communication reference signal, and calculates the second value based on the sensing reference signal.

[0037] Next, the base station 100 uses the second pattern to transmit the communication reference signal and sensing reference signal assigned to antenna port 160 to multiple mobile stations 200. Specifically, the sensing reference signal is assigned to and transmitted to antenna ports 5, 6, 9, and 10, and the communication reference signal is assigned to and transmitted to antenna ports 0-4, 7, 8, and 11-15.

[0038] Each of the multiple mobile stations 200 receives a second pattern sensing reference signal from the base station 100 and calculates a value indicating the reception status of the sensing reference signal. Each of the mobile stations 200 also receives a second pattern communication reference signal from the base station 100 and calculates the reception quality of the communication reference signal. Here, if the reception quality of the communication reference signal for the second pattern is called the "third value," then the value indicating the reception status of the sensing reference signal for the second pattern is called the "fourth value." In other words, each of the multiple mobile stations 200 receives the communication reference signal and the sensing reference signal assigned to the antenna port using the second pattern, calculates the third value based on the communication reference signal, and calculates the fourth value based on the sensing reference signal. Here, it is assumed that the mobile stations 200 are equipped with MIMO antennas. For example, suppose the mobile station 200 has four antennas, two for communication transmission and reception, and the remaining two for sensing transmission and reception. The antenna configuration of the mobile station 200 only needs to have antennas for communication and sensing, and is not limited to the example of four antennas.

[0039] Each of the multiple mobile stations 200's feedback information generation units 252 selects an antenna port configuration with high reception quality and generates communication feedback information (S102). In other words, each of the multiple mobile stations 200 selects the higher of the reception quality in the first pattern and the reception quality in the second pattern, and includes information from either the selected first or second pattern as the first evaluation value in the communication feedback information. This can also be described as deriving the first evaluation value based on the first and third values, and generating communication feedback information that includes the first evaluation value. The mobile stations 200 also include the index, RI, PMI, and CQI of the selected antenna port configuration in the communication feedback information.

[0040] Each of the multiple mobile stations 200's feedback information generation units 252 selects the optimal antenna port configuration for sensing based on the SINR and generates sensing feedback information (S103). Here, the antenna port configuration that yields the highest SINR is selected as the optimal antenna port configuration. In other words, each of the multiple mobile stations 200 selects the higher of the value indicating the reception status in the first pattern and the value indicating the reception status in the second pattern, and includes information from either the selected first or second pattern as a second evaluation value in the sensing feedback information. This can also be described as deriving the second evaluation value based on the second and fourth values ​​and generating sensing feedback information that includes the second evaluation value. The mobile station 200 also includes the index and SINR information of the selected antenna port configuration in the sensing feedback information. By considering interference waves and noise in the selection of the antenna port configuration for sensing, the accuracy of sensing is improved.

[0041] Each of the feedback information generation units 252 of the multiple mobile stations 200 determines the optimal precoding matrix according to the selected antenna port configuration for sensing, and includes the PMI, which is the precoding matrix index, in the sensing feedback information (S104). Known techniques are used to determine the precoding matrix.

[0042] Each of the multiple mobile stations 200 transmits communication feedback information and sensing feedback information to the base station 100 (S105). Scheduling information for the sensing feedback information and communication feedback information is transmitted in advance from the base station 100 to each mobile station 200 via PDDCH. The scheduling information includes information on the timing and resource elements required to acquire the sensing feedback information and communication feedback information, respectively. In sensing, indicators such as RI, which indicates the number of layers used in communication, and CQI, which allows selection of the optimal coding rate and modulation method, are not of high importance. On the other hand, in sensing, the SINR indicator, which indicates the effects of interference waves and noise, is of higher importance. Here, the signal-to-interference noise ratio (SINR), which is related to improving the distance resolution and velocity resolution, which are performance characteristics of sensing, was used as an evaluation value for radio wave conditions, but it is not limited to SINR as long as it is an indicator that can evaluate the performance of sensing.

[0043] The base station 100 receives communication feedback information and sensing feedback information from each of the multiple mobile stations 200. The antenna port configuration determination unit 150 of the base station 100 evaluates the communication usage environment based on the communication feedback information from each mobile station (S106). For example, the number of data signal retransmission requests may be used as feedback information. Here, the antenna port configuration determination unit 150 uses, but is not limited to, the sum of the CQI received from each mobile station 200 as an evaluation value for evaluating the communication usage environment. The antenna port configuration determination unit 150 may also take the RI value into consideration. Instead of the sum, the antenna port configuration determination unit 150 may use the average value, weighted average value, median value, maximum value, minimum value, etc. Furthermore, the antenna port configuration determination unit 150 of the base station 100 evaluates the sensing usage environment based on the sensing feedback information from each mobile station 200 (S107). Here, the antenna port configuration determination unit 150 uses, but is not limited to, the sum of the SINRs received from each mobile station 200 as an evaluation value for evaluating the sensing environment.

[0044] The antenna port configuration determination unit 150 of the base station 100 determines the antenna port configuration for communication, the MIMO multiplexing count, and the precoding weights based on the evaluation results of the communication usage environment (S108). Furthermore, the antenna port configuration determination unit 150 of the base station 100 determines the antenna port configuration for sensing, the MIMO multiplexing count, and the precoding weights based on the sensing usage environment (feedback information for sensing from each mobile station 200) (S109). Figure 8 is also used here to illustrate this process.

[0045] Figure 8 is a flowchart showing the procedure for determining the antenna port configuration. The base station 100 is pre-configured to either prioritize sensing or communication. When sensing is prioritized (Y in S150), the antenna port configuration determination unit 150 determines the candidate antenna port configuration that has the highest number of selections as the optimal antenna port configuration for sensing (S152). This corresponds to determining the antenna port configuration as the larger of the number of selections of the first pattern and the number of selections of the second pattern in the first evaluation value from multiple mobile stations 200. On the other hand, when sensing is not prioritized (N in S150), the antenna port configuration determination unit 150 determines the candidate antenna port configuration that has the highest number of selections as the optimal antenna port configuration for communication (S154). This corresponds to determining the antenna port configuration as the larger of the number of selections of the first pattern and the number of selections of the second pattern in the second evaluation value from multiple mobile stations 200.

[0046] Alternatively, the antenna port configuration determination unit 150 may determine the candidate antenna port configuration where the sum of the number of antenna port configurations selected as optimal for sensing and the number of antenna port configurations selected as optimal for communication is the largest.

[0047] The process in Figure 9 may be executed instead of the process in Figure 8. Figure 9 is a flowchart showing an alternative procedure for determining the antenna port configuration. If sensing is prioritized (Y in S160), the antenna port configuration determination unit 150 determines the candidate antenna port configuration with the highest evaluation value for sensing (S162). This corresponds to determining the antenna port configuration so that the total value of SINR is maximized. If sensing is not prioritized (N in S160), the antenna port configuration determination unit 150 determines the candidate antenna port configuration with the highest evaluation value for communication (S164). This corresponds to determining the antenna port configuration so that the total value of RI, PMI, or CQI is maximized. The antenna port configuration determination unit 150 may also input sensing feedback information from each mobile station 200 into a pre-trained neural network and use the output of the neural network as the evaluation value for sensing. For example, by training the neural network so that the evaluation value for sensing increases as the detection rate of people and cars increases, the detection rate for sensing people and cars can be increased. In machine learning, increasing the number of base station antennas and mobile stations, and thus the resulting large-scale data, is effective in improving detection rates.

[0048] In other words, the antenna port configuration determination unit 150 determines the antenna port to be used for communication and the antenna port to be used for sensing based on the first evaluation value of each of the multiple mobile stations 200 and the second evaluation value of each of the multiple mobile stations 200. Return to Figure 5.

[0049] The base station 100 transmits and receives sensing and communication radio waves based on the determined antenna port configuration (S13). This allows the communication reference signal and the sensing reference signal to be assigned to the antenna port 160. In the above description, the sensing process is performed after the communication process, but the sensing process may be performed before the communication process, or the communication process and the sensing process may be executed in parallel. For example, in Figure 7, the base station may execute step S101 before step S100, or step S100 and step S101 may be executed in parallel.

[0050] Figure 10 is a flowchart of another communication procedure by the wireless communication system 1000. This is a modified version of the communication procedure in Figure 5, with the addition of step S14. If the evaluation values ​​such as SINR and CQI have not reached a predetermined level (N in S14), the antenna port configuration determination unit 150 returns to step S10 and repeats the process by selecting a candidate for a different antenna port ratio or antenna port configuration. If the evaluation values ​​such as SINR and CQI have reached a predetermined level (Y in S14), the antenna port configuration determination unit 150 proceeds to step S13 described above.

[0051] According to this embodiment, the antenna port ratio and antenna port configuration are adjusted based on the communication feedback information and sensing feedback information derived from the communication reference signal and sensing reference signal, so that sensing can be performed while maintaining or optimizing communication quality. Furthermore, communication can be performed while maintaining or optimizing sensing quality.

[0052] (Example 2) Embodiment 1 described a process for determining the antenna port configuration using a communication reference signal or a sensing reference signal. Embodiment 2 relates to a process for assigning a reference signal to an antenna port after the antenna port configuration has been determined. After the antenna port configuration has been determined, by transmitting a reference signal with an antenna port configuration different from the determined antenna port configuration, it becomes possible to monitor the temporal changes in the antenna port configuration that are optimal for communication and sensing. In other words, changes in the environment in which sensing or communication is performed are monitored by transmitting and receiving sensing reference signals and sensing feedback information between the base station 100 and the mobile station 200 regarding the antenna port ratio and antenna port configuration in which communication and sensing are being performed. As a result of the monitoring, the base station 100 and the mobile station 200 can change the antenna port ratio and antenna port configuration in response to changes in environmental conditions such as changes in pedestrian flow or obstacles such as weather, or interference with other communications. At least one of the antenna port ratio and antenna port configuration may be changed.

[0053] The wireless communication system 1000, base station 100, and mobile station 200 according to Example 2 are of the same type as those shown in Figures 1, 2, and 4. Here, as an example, we will describe a monitoring example where there are two antenna ports 160 for communication and two antenna ports 160 for sensing. These four antenna ports are shown as antenna ports AD.

[0054] After processing in Example 1, the base station 100 uses multiple antenna ports 160 for communication or sensing and transmits sensing reference signals assigned to the antenna ports 160 used for sensing to multiple mobile stations 200. Each of the multiple mobile stations 200 receives the sensing reference signal, calculates a value indicating the reception status of the sensing reference signal, such as SINR, and transmits sensing feedback information containing the value indicating the reception status to the base station 100.

[0055] Figure 11 is a flowchart illustrating the procedure for updating the number of antenna ports by the wireless communication system 1000. The antenna port configuration determination unit 150 receives sensing feedback information from each of the multiple mobile stations 200 and calculates the appropriateness level V1 based on the values ​​indicating the reception status of each of the multiple mobile stations 200 (S200). For example, the antenna port configuration determination unit 150 calculates the sum of the SINR values ​​of each of the multiple mobile stations 200 and uses the sum as the appropriateness level. The antenna port configuration determination unit 150 also predefines an appropriate range for comparison with the appropriateness level. The appropriate range is the range in which the current antenna port configuration is judged to be appropriate, and is the range between the minimum and maximum values.

[0056] If the appropriateness score V1 is not greater than the maximum value (N in S202) and is not less than the minimum value (N in S204), that is, if the appropriateness score V1 is within the range between the minimum and maximum values ​​of the appropriate range, the number of antenna ports 160 that transmit the sensing reference signal is maintained (S206). In other words, the antenna port configuration is maintained. This corresponds to the case where the appropriateness of the antenna port configuration is as expected. Figures 12(a)-(c) show an example of antenna port assignment in Embodiment 2. In Figure 12(a), the communication reference signal is assigned to antenna ports A and B, and the sensing reference signal is assigned to antenna ports C and D. The communication data signal is assigned to antenna ports A and B, and the sensing data signal is assigned to antenna ports C and D. Figures 12(b)-(c) will be described later, and we return to Figure 11.

[0057] If the suitability score V1 is greater than the maximum value (Y in S202), the antenna port configuration determination unit 150 reduces the number of antenna ports 160 that transmit the sensing reference signal (S208). This corresponds to the case where the suitability of the antenna port configuration is higher than expected. In Figure 12(b), the communication reference signal is assigned to antenna ports A and B, and the sensing reference signal is assigned to antenna port C. The communication data signal is assigned to antenna ports A and B, and the sensing data signal is assigned to antenna ports C and D. Figure 12(c) will be described later, and then we return to Figure 11.

[0058] If the suitability score V1 is less than the minimum value (Y in S204), the antenna port configuration determination unit 150 increases the number of antenna ports 160 that transmit sensing reference signals (S210). This corresponds to the case where the suitability score of the antenna port configuration is lower than expected. In Figure 12(c), the communication reference signal is assigned to antenna ports A and B, and the sensing reference signal is assigned to antenna ports B, C, and D. The communication data signal is assigned to antenna ports A and B, and the sensing data signal is assigned to antenna ports C and D. Here, the increased sensing reference signal is transmitted from the communication antenna port 160. For example, if there is an empty sensing antenna port 160 that is not transmitting a reference signal, the sensing reference signal may be transmitted from that sensing antenna port 160.

[0059] Here, an evaluation value is used to assess the appropriateness of the antenna port configuration by controlling the sensing reference signal to evaluate the sensing usage environment. However, an evaluation value may also be used to assess the communication usage environment by controlling the communication reference signal. Furthermore, while the sum of SINR is used here as the appropriateness of the antenna port configuration, another evaluation value used in Example 1 to assess the usage environment may also be used. Additionally, the antenna port configuration determination unit 150 may control both the sensing reference signal and the communication reference signal using both evaluation values ​​for the sensing usage environment and the communication usage environment. For example, if both the appropriateness of the sensing antenna port configuration and the communication antenna port configuration are low, the antenna port configuration determination unit 150 may increase the number of antenna ports 160 that transmit the sensing reference signal and the communication reference signal.

[0060] Furthermore, the antenna port configuration determination unit 150 may switch between using an evaluation value that evaluates the communication usage environment and an evaluation value that evaluates the sensing usage environment as the appropriateness of the antenna port configuration, based on the decision of whether to prioritize communication or sensing.

[0061] Here, we have described the case where there are two antenna ports 160, but Massive MIMO with multiple antenna ports 160 is also possible. When changing the antenna port configuration, the antenna port configuration determination unit 150 may select the antenna port 160 furthest from the current antenna port 160, or it may select the antenna port 160 furthest from the communication antenna port 160. The antenna port configuration determination unit 150 may also select the antenna port 160 using the information from when the antenna ports 160 were assigned.

[0062] Furthermore, the antenna port configuration determination unit 150 may calculate the appropriateness V2 after changing the number of antenna ports 160 that transmit sensing reference signals (S212), and compare the appropriateness V2 after changing the number of antenna ports 160 with the appropriateness V1 before changing the number of antenna ports 160 (S214). If the absolute difference between the appropriateness V2 after changing the number of antenna ports 160 and the appropriateness V1 before changing the number of antenna ports 160 is less than or equal to a predetermined value (Y in S214), the antenna port configuration determination unit 150 changes the number of antenna ports that transmit sensing data signals to match the number of antenna ports that transmit sensing reference signals (S216). In other words, if the number of antenna ports that transmit sensing reference signals is reduced, the number of antenna ports that transmit sensing data signals is also reduced. Also, if the number of antenna ports that transmit sensing reference signals is increased, the number of antenna ports that transmit sensing data signals is also increased. The antenna port configuration determination unit 150 then changes the number of antenna ports that transmit communication reference signal data signals to match the number of antenna ports that transmit sensing reference signals (S218). Furthermore, the antenna port configuration determination unit 150 changes the number of antenna ports that transmit communication data signals to match the number of antenna ports that transmit sensing reference signals (S220). The antenna port configuration determination unit 150 does not change the number of antenna ports if the absolute difference between the appropriateness V2 after changing the number of antenna ports 160 and the appropriateness V1 before changing the number of antenna ports 160 is not less than or equal to a predetermined value (N in S214). In other words, the antenna port configuration determination unit 150 changes the first configuration, which is the antenna port configuration that transmitted the sensing reference signal before changing the number of antenna ports, to the second configuration, which is the antenna port configuration that transmitted the sensing reference signal after changing the number of antenna ports, if the difference between the appropriateness after changing the number of antenna ports and the appropriateness before changing the number of antenna ports is less than or equal to a predetermined value. The antenna port configuration determination unit 150 may perform any one of steps S216, S218, or S220.

[0063] Figures 13(a) to (c) show examples of antenna port assignments after modification in Example 2. Figure 13(a) is a modified example corresponding to Figures 12(a) to (c), where the appropriateness V1 is not greater than the maximum value (N in S202) and is not less than the minimum value (N in S204), or where the absolute difference between the appropriateness V2 after changing the number of antenna ports 160 and the appropriateness V1 before changing the number of antenna ports 160 is not less than a predetermined value (N in S214). In this case, the antenna ports are not changed.

[0064] Figure 13(b) is a modified example corresponding to Figure 12(b), in which the suitability score V1 is greater than the maximum value (Y in S202), the antenna port configuration determination unit 150 reduces the number of antenna ports 160 that transmit sensing reference signals (S208), and in the case where the absolute difference between the suitability score V2 after reducing the number of antenna ports 160 and the suitability score V1 before reducing the number of antenna ports 160 is less than or equal to a predetermined value (Y in S214), the number of antenna ports that transmit sensing data signals is reduced to match the number of antenna ports that transmit sensing reference signals (S216), the number of antenna ports that transmit communication reference signal data signals is increased (S218), and the number of antenna ports that transmit communication data signals is increased (S220).

[0065] Figure 13(c) is a modified example corresponding to Figure 12(c), in which the suitability score V1 is smaller than the maximum value (Y in S204), the antenna port configuration determination unit 150 increases the number of antenna ports 160 that transmit sensing reference signals (S208), and in the case where the absolute difference between the suitability score V2 after increasing the number of antenna ports 160 and the suitability score V1 before increasing the number of antenna ports 160 is less than or equal to a predetermined value (Y in S214), the number of antenna ports that transmit sensing data signals is increased to match the number of antenna ports that transmit sensing reference signals (S216), the number of antenna ports that transmit communication reference signal data signals is decreased (S218), and the number of antenna ports that transmit communication data signals is decreased (S220).

[0066] Figures 14(a) and (b) show another example of the antenna port assignment after the modification in Embodiment 2. Figure 14(a) is a modified example corresponding to Figure 12(b), in which the suitability score V1 is greater than the maximum value (Y in S202), the antenna port configuration determination unit 150 reduces the number of antenna ports 160 that transmit sensing reference signals (S208), and in the case where the absolute difference between the suitability score V2 after reducing the number of antenna ports 160 and the suitability score V1 before reducing the number of antenna ports 160 is less than or equal to a predetermined value (Y in S214), the number of antenna ports that transmit sensing data signals is reduced to match the number of antenna ports that transmit sensing reference signals (S216). In this case, antenna port D becomes an empty port and can be used for another purpose.

[0067] Figure 14(b) is a modified example corresponding to Figure 12(c), where the suitability score V1 is smaller than the maximum value (Y in S204), the antenna port configuration determination unit 150 increases the number of antenna ports 160 that transmit sensing reference signals (S208), and when the absolute difference between the suitability score V2 after increasing the number of antenna ports 160 and the suitability score V1 before increasing the number of antenna ports 160 is less than or equal to a predetermined value (Y in S214), the number of antenna ports that transmit sensing data signals is increased to match the number of antenna ports that transmit sensing reference signals (S216). In this case, antenna port B becomes a shared port for communication and sensing, and may be shared by communication and sensing after processing such as time division or frequency division.

[0068] According to this embodiment, by changing and monitoring the number of antenna ports 160 that transmit sensing reference signals according to the appropriateness of the antenna port configuration, communication can be suitably performed while maintaining sensing quality. Furthermore, by changing and monitoring the number of antenna ports 160 that transmit communication reference signals according to the appropriateness of the antenna port configuration, sensing can be suitably performed while maintaining communication quality. In addition, if the absolute difference in appropriateness before and after changing the number of antenna ports 160 that transmit sensing or communication reference signals is less than or equal to a predetermined value, the appropriateness before the change can be maintained by changing the number of antenna ports 160 that transmit sensing data signals and communication data signals. Also, in step S214, the antenna port configuration determination unit 150 may check whether the absolute difference in appropriateness before and after changing the number of antenna ports 160 that transmit sensing or communication reference signals is less than or equal to a predetermined value and greater than or equal to a second predetermined value. In this way, the accumulation of minute changes in appropriateness can be suppressed and an appropriate appropriateness can be maintained.

[0069] The present invention has been described above based on examples. These examples are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications also fall within the scope of the present invention.

[0070] In Example 1, the CSI-RS, a downlink reference signal, is used as the sensing reference signal to determine the antenna port configuration, MIMO multiplexing count, and precoding weight. However, this is not limited to this; for example, the SRS (Sounding Reference Signal), an uplink reference signal, may be used as the sensing reference signal, or both CSI-RS and SRS may be used. This modification improves the flexibility of the configuration.

[0071] Examples 1 and 2 assume Beyond 5G / 6G as the wireless communication system 1000. However, it is not limited to this, and the wireless communication system 1000 may be 4G using MIMO, LTE (Long Term Evolution), Wi-Fi (registered trademark), etc. This modification expands the scope of application. [Explanation of symbols]

[0072] 100 Base station, 110 Channel coding unit, 112 Modulation unit, 114 Layer mapping unit, 116 Antenna mapping unit, 118 Resource element mapping unit, 120 Digital beamforming unit, 122 Transmit signal processing unit, 124 Duplexer unit, 130 Antenna unit, 132 Antenna control unit, 140 Receive signal processing unit, 142 Signal separation unit, 144 Channel status information acquisition unit, 150 Antenna port configuration determination unit, 160 Antenna port, 162 Antenna element, 200 Mobile station, 210 Channel coding unit, 212 Modulation unit, 214 Layer mapping unit, 216 Antenna mapping unit, 218 Resource element mapping unit, 220 Digital beamforming unit, 222 Transmit signal processing unit, 224 Duplexer unit, 230 Antenna section, 240 Received signal processing section, 242 Signal separation section, 244 Channel status information evaluation section, 250 Antenna port configuration selection section, 252 Feedback information generation section, 1000 Wireless communication system.

Claims

1. A base station equipped with multiple antenna ports, The system comprises multiple mobile stations that communicate with the aforementioned base station, The base station transmits a sensing reference signal to the plurality of mobile stations. Each of the aforementioned mobile stations receives a sensing reference signal, calculates a value indicating the reception status of the sensing reference signal, and transmits feedback information containing the value indicating the reception status to the base station. The base station receives feedback information from each of the multiple mobile stations and calculates the degree of appropriateness based on the values ​​indicating the reception status of each of the multiple mobile stations. The base station reduces the number of antenna ports that transmit the sensing reference signal when the suitability is greater than the maximum value. The base station increases the number of antenna ports that transmit the sensing reference signal when the suitability is less than the minimum value. Wireless communication system.

2. The base station calculates the appropriateness after changing the number of antenna ports that transmit the sensing reference signal, and if the difference between the appropriateness after changing the number of antenna ports and the appropriateness before changing the number of antenna ports is less than or equal to a predetermined value, it changes the first configuration of the antenna ports that transmitted the sensing reference signal before changing the number of antenna ports to the second configuration of the antenna ports that transmitted the sensing reference signal after changing the number of antenna ports. The wireless communication system according to claim 1.

3. The base station calculates the appropriateness after changing the number of antenna ports that transmit sensing reference signals, and if the difference between the appropriateness after changing the number of antenna ports and the appropriateness before changing the number of antenna ports is less than or equal to a predetermined value, it changes one of the following to match the number of antenna ports that transmit sensing data signals, the number of antenna ports that transmit communication reference signals, or the number of antenna ports that transmit communication data signals, in accordance with the number of antenna ports that transmit sensing reference signals. The wireless communication system according to claim 1 or 2.

4. A base station equipped with multiple antenna ports, A wireless communication method in a wireless communication system comprising a base station and a plurality of mobile stations communicating with the base station, The base station transmits a sensing reference signal to the plurality of mobile stations. Each of the aforementioned mobile stations receives a sensing reference signal, calculates a value indicating the reception status of the sensing reference signal, and transmits feedback information containing the value indicating the reception status to the base station. The base station receives feedback information from each of the multiple mobile stations and calculates the degree of appropriateness based on the values ​​indicating the reception status of each of the multiple mobile stations. The base station reduces the number of antenna ports that transmit the sensing reference signal when the suitability is greater than the maximum value. The base station increases the number of antenna ports that transmit the sensing reference signal when the suitability is less than the minimum value. Wireless communication method.

5. A program executed at a base station that performs the wireless communication method described in claim 4.

6. A base station equipped with multiple antenna ports that transmits a sensing reference signal to a mobile station and receives feedback information, Feedback information containing a value indicating the reception status of the sensing reference signal is transmitted from the mobile station. The system receives feedback information and calculates the degree of appropriateness based on the value indicating the reception status of the mobile station. If the suitability is greater than the maximum value, the number of antenna ports that transmit the sensing reference signal is reduced. If the suitability is less than the minimum value, increase the number of antenna ports that transmit the sensing reference signal. Base station.

7. A wireless communication method at a base station equipped with multiple antenna ports, which transmits a sensing reference signal to a mobile station and receives feedback information, Feedback information containing a value indicating the reception status of the sensing reference signal is transmitted from the mobile station. The system receives feedback information and calculates the degree of appropriateness based on the value indicating the reception status of the mobile station. If the suitability is greater than the maximum value, the number of antenna ports that transmit the sensing reference signal is reduced. If the suitability is less than the minimum value, increase the number of antenna ports that transmit the sensing reference signal. Wireless communication method.

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