Wireless communication system, state detection device, state detection method, and state detection program
The wireless communication system addresses the challenge of independent AP operation by aligning CSI timing and calculating phase differences to efficiently detect object states and movements using multiple base stations.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NT T INC
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-15
AI Technical Summary
Conventional methods face challenges in accurately and efficiently detecting the movement and state of an object using channel state information (CSI) in a multi-access point (multi-AP) system due to independent operation of each AP, which complicates the use of CSI for learning.
A wireless communication system and method that utilizes a collection unit to gather CSI from multiple transmitting devices, determines a reference device, calculates phase differences and frequency offsets, and estimates CSI to accurately detect the state and movement of objects by aligning timing across multiple APs.
Enables accurate and efficient detection of object presence, movement, and state by eliminating frequency offsets, thereby enhancing the utilization of CSI across multiple base stations.
Smart Images
Figure JP2024039916_15052026_PF_FP_ABST
Abstract
Description
Wireless communication system, state detection device, state detection method, and state detection program
[0001] The present invention relates to a wireless communication system, a state detection device, a state detection method, and a state detection program.
[0002] For example, in order for a radio base station serving as a transmission device to perform signal transmission to a radio terminal station serving as a reception device, based on propagation channel information, CSI (Channel State Information) representing the state of the radio channel through which the signal has passed is calculated. A technique is known.
[0003] The propagation channel information includes amplitude and phase information between transmission and reception antennas at a plurality of frequencies called subcarriers. For example, the propagation channel information is used for transmission beamforming in signal transmission.
[0004] Also, as a technique for detecting the motion / state of a person or an object by using a wireless interconnection technology such as Wi-Fi (registered trademark), there is a Wi-Fi sensing technology using CSI (see, for example, Non-Patent Document 1). Also, Wi-Fi sensing technology includes, for example, a technology for detecting the motion / state of an object by pre-learning the variation of CSI and the movement of the object.
[0005] And since the channel state information is much larger information than the conventional signal strength information, it is known that it leads to higher accuracy in estimating the state of the propagation path.
[0006] Also, in order to reduce interference in a high-density ultra-high throughput wireless LAN, a technique using a coordinated multi-point (JT-COMP) joint transmission approach of a cellular network is known (see, for example, Non-Patent Document 2).
[0007] W. Li et al., "A Taxonomy of WiFi Sensing: CSI vs Passive WiFi Radar", 2020 IEEE Globecom Workshops (GC Wkshps, Taipei, Taiwan, 2020, pp. 1-6, doi: 10.1109 / GCWkshps50303.2020.9367546.IL Cherif, L. Zitoune and V. Veque, "Performance evaluation of Joint Transmission Coordinated-Multipoint in dense Very High Throughput WLANs scenario", 2015 IEEE 40th Conference on Local Computer Networks (LCN), Clearwater Beach, FL, USA, 2015, pp. 426-429, doi: 10.1109 / LCN.2015.7366344
[0008] However, conventionally, when attempting to detect the movement and state of an object using CSI in a multi-access point (multi-AP) system, it was difficult to use each CSI accurately and efficiently because each AP operates independently.
[0009] For example, since each AP (Application Programming Device) has its own oscillator and uses it as a clock (reference frequency), when detecting the motion and state of an object using each CSI (Critical Scheme Indicator), the motion of the object and the fluctuation of the CSI were independent for each AP. In this case, it was difficult to use each CSI efficiently for learning.
[0010] The present invention has been made in view of the above-mentioned problems, and aims to provide a wireless communication system, a state detection device, a state detection method, and a state detection program that can accurately and efficiently detect the operation and state of an object based on channel state information used by multiple base stations, each acting as a transmitting or receiving device, to transmit packets.
[0011] A wireless communication system according to one embodiment of the present invention has a transmitting device and a receiving device, each equipped with a communication unit for transmitting and receiving packets, wherein a plurality of the transmitting devices transmit channel state information to one of the receiving devices, or one of the receiving devices transmits channel state information to a plurality of the transmitting devices, and the wireless communication system comprises: a collection unit that collects the channel state information transmitted by the plurality of transmitting devices to one of the receiving devices, or by one of the receiving devices transmitting packets to a plurality of the transmitting devices; a determination unit that determines one of the transmitting devices or the receiving device to be a reference device that transmits a reference packet for measuring channel state information; and a calculation of the difference in channel state information collected by the collection unit as a reference phase difference for each packet transmitted by the reference device determined by the determination unit at a first time and a second time. The system is characterized by comprising: a reference calculation unit; an individual calculation unit that calculates the difference in channel state information collected by the collection unit as an individual phase difference for each packet transmitted by the transmitting device or the receiving device that transmits packets for measuring channel state information at the first and second time points, excluding the reference device; an offset calculation unit that calculates the difference between the reference phase difference and each of the individual phase differences as their respective frequency offsets; an estimation unit that estimates channel state information between the transmitting device and the receiving device at the third time point, excluding the frequency offset at the third time point, based on the frequency offset calculated by the offset calculation unit and the channel state information collected by the collection unit at the third time point; and a state detection unit that detects the state between the transmitting device and the receiving device based on the channel state information estimated by the estimation unit.
[0012] Furthermore, the state detection device according to one embodiment of the present invention includes a collection unit that collects channel state information transmitted by a plurality of transmitting devices, each equipped with a communication unit for transmitting and receiving packets, to a single receiving device equipped with a communication unit for transmitting and receiving packets, or by a single receiving device to a plurality of transmitting devices in order to transmit packets; a determination unit that determines one of the transmitting devices or the receiving devices to be a reference device that transmits a reference packet for measuring channel state information; a reference calculation unit that calculates the difference in channel state information collected by the collection unit as a reference phase difference for each packet transmitted by the reference device determined by the determination unit at the first time and the second time; and a packet for measuring channel state information excluding the reference device. The device is characterized by comprising: an individual calculation unit that calculates the difference in channel state information collected by the collection unit as an individual phase difference for each packet transmitted by the transmitting device or the receiving device at a first time and a second time, respectively; an offset calculation unit that calculates the difference between the reference phase difference and each of the individual phase differences as their respective frequency offsets; an estimation unit that estimates channel state information between the transmitting device and the receiving device at a third time, excluding the frequency offset at the third time, based on the frequency offset calculated by the offset calculation unit and the channel state information collected by the collection unit at a third time; and a state detection unit that detects the state between the transmitting device and the receiving device based on the channel state information estimated by the estimation unit.
[0013] Furthermore, a state detection method according to one embodiment of the present invention is a state detection method for detecting the state between a wireless communication system having a transmitting device and a receiving device, each equipped with a communication unit for transmitting and receiving packets, wherein a plurality of the transmitting devices transmit channel state information to one of the receiving devices, or one of the receiving devices transmits channel state information to a plurality of the transmitting devices, in order to transmit packets, comprising: a collection step of collecting channel state information transmitted by a plurality of the transmitting devices to one of the receiving devices, or one of the receiving devices transmits channel state information to a plurality of the transmitting devices; a determination step of determining one of the transmitting devices or the receiving device to be a reference device that transmits a reference packet for measuring channel state information; and the difference of the channel state information collected by the collection step for each packet transmitted by the reference device determined by the determination step at a first time and a second time. The method is characterized by including: a reference calculation step of calculating minutes as a reference phase difference; an individual calculation step of calculating the difference in channel state information collected by the collection step as an individual phase difference for each packet transmitted by the transmitting device or the receiving device that transmits packets for measuring channel state information at the first and second time points, excluding the reference device; an offset calculation step of calculating the difference between the reference phase difference and each of the individual phase differences as their respective frequency offsets; an estimation step of estimating channel state information between the transmitting device and the receiving device, excluding the frequency offset at the third time point, based on the frequency offset calculated by the offset calculation step and the channel state information collected at the third time point by the collection step; and a state detection step of detecting the state between the transmitting device and the receiving device based on the channel state information estimated by the estimation step.
[0014] According to the present invention, the operation and state of an object can be detected accurately and efficiently based on channel state information used by multiple base stations, each acting as a transmitting or receiving device, to transmit packets.
[0015] This diagram illustrates an overview of technology for detecting the movement and state of people and objects using CSI. (a) is a diagram illustrating an overview of technology for wireless communication in which multiple APs do not cause mutual interference. (b) is a diagram illustrating an overview of technology for beamforming in which multiple APs create a null for terminals that are not the target. (c) is a diagram illustrating an overview of technology for a terminal to synthesize data transmitted from multiple APs. This diagram illustrates an overview of a wireless communication system according to one embodiment. This is a functional block diagram illustrating the functions of a state detection device according to one embodiment. This diagram illustrates an overview of other operations of a wireless communication system according to one embodiment. This is a diagram illustrating an example of hardware configuration of a state detection device according to one embodiment.
[0016] First, we will explain the overview of the technology that uses CSI to detect the movement and state of people and objects. Figure 1 is an example diagram illustrating the overview of the technology that uses CSI to detect the movement and state of people and objects. For example, the base station (AP) 10 and the terminal 20 transmit a packet (known signal) that serves as a reference for measuring (calculating) channel state information, and the other measures the channel state information. Channel state information can also be described as an impulse response.
[0017] AP10 and terminal 20 each have functions as a transmitter and a receiver, respectively, utilizing wireless interconnection technologies such as Wi-Fi®. For example, AP10 and terminal 20 each have a communication unit (not shown) that transmits and receives packets. In this case, the state detection device 30 collects CSIs representing the state of each wireless channel between AP10 and terminal 20, and detects the presence, movement, and state of people and objects between AP10 and terminal 20. The state detection device 30 also has a communication unit (see Figure 4) that transmits and receives packets, and has functions as both a transmitter and a receiver.
[0018] Hereafter, components having substantially the same function as the AP10, terminal 20, and state detection device 30 shown in Figure 1 will be denoted by the same reference numerals. In addition, multiple components such as multiple AP10s will be individually distinguished and shown as AP10-1, AP10-2, and so on.
[0019] Figure 2 is a conceptual diagram illustrating an overview of a technology in which multiple base stations (APs) 10 cooperate (coordinate) to perform wireless communication with a terminal 20. Figure 2(a) is a diagram illustrating an overview of a technology in which multiple APs 10 perform wireless communication in a manner that prevents mutual interference. Figure 2(b) is a diagram illustrating an overview of a technology in which multiple APs 10 perform beamforming that creates a null for terminals 20 that are not targeted. Figure 2(c) is a diagram illustrating an overview of a technology in which terminal 20 combines data transmitted from multiple APs 10.
[0020] As shown in Figure 2(a), for example, AP10-1 and AP10-2 cooperate to control the transmission power so as not to cause interference with each other. Also, as shown in Figure 2(b), for example, AP10-1 and AP10-2 each perform beamforming for the terminal 20 to which they are to transmit, and perform null beamforming for terminal 20 that are not to which they are to transmit. Furthermore, as shown in Figure 2(c), for example, AP10-1 and AP10-2 cooperate to transmit data so that terminal 20-1 can combine the data received from AP10-1 and AP10-2 respectively.
[0021] Furthermore, the wireless communication system according to one embodiment detects the presence, movement, and state of people and objects based on the CSI used by multiple AP10s utilizing the technology shown in Figures 1 and 2.
[0022] Figure 3 is a diagram illustrating an overview of a wireless communication system 1 according to one embodiment. The wireless communication system 1 is a multi-AP sensing system that has, for example, a plurality of APs 10 (AP10-1 to AP10-5) and a state detection device 30, and detects the presence, movement, and state of people and objects around the plurality of APs 10.
[0023] For example, wireless communication system 1 includes multiple APs 10, multiple terminals 20 (not shown), and a status detection device 30, and multiple transmitting devices transmit channel status information to one receiving device, or one receiving device transmits channel status information to multiple transmitting devices in order to transmit packets.
[0024] Note that in Figure 3, the terminals 20 that communicate wirelessly with each AP 10 are not shown. Here, APs 10-1 to 10-5 are assumed to be shared APs that communicate directly with the terminals 20. However, the wireless communication system 1 may also include a sharing AP that manages (controls) the shared APs. APs 10-1 to 10-5 each have their own oscillators that generate a clock signal.
[0025] Here, assuming that AP10-1 is determined to be the reference base station (reference AP) that serves as the standard for the CSI, the operation of the wireless communication system 1 will be described.
[0026] More specifically, when each of AP10-1 to AP10-5 acquires multiple CSI phase components, the wireless communication system 1 determines one of AP10-1 to AP10-5 (in this case, AP10-1) as the reference AP.
[0027] Then, for example, the state detection device 30 calculates the difference △CSI_p(A,B) between the CSI_p(A) of AP10-1 at time A and the CSI_p(B) of AP10-1 at time B.
[0028] Furthermore, for example, the state detection device 30 takes AP10-2 to AP10-5, which are not reference APs, as AP(i), and similarly calculates △CSI_p'(i,A,B)=CSI_p'(i,A)-CSI_p'(i,B) for each AP(i).
[0029] Here, when time elapses from time A to time B, the frequency offsets △△CSI_p(i,A,B) of the oscillators of AP10-2 to AP10-5 (each AP(i)) with respect to the frequency of the oscillator of AP10-1 become △CSI_p'(i,A,B)-△CSI_p(A,B).
[0030] Subsequently, for example, the state detection device 30 estimates the phase CSI_p' to (i,C) of each of AP10-2 to AP10-5 by subtracting △△CSI_p(i), which is proportional to the time difference between (BA) and (CA), from the phase CSI_p'(i,C) of each of AP10-2 to AP10-5 at time C, thereby eliminating the effect of frequency offset, and estimates the CSI of each of AP10-2 to AP10-5.
[0031] The state detection device 30 then performs the above-described processing on each of the subcarriers AP10-1 to 10-5 to detect the presence, movement, and state of people and objects around AP10-1 to 10-5. The state detection device 30 may also be configured to eliminate the frequency offset to the oscillator it uses to generate its own clock.
[0032] Next, a specific example of the configuration of the state detection device 30 will be described. Figure 4 is a functional block diagram illustrating the functions of a state detection device 30 according to one embodiment. As shown in Figure 4, the state detection device 30 includes, for example, a communication unit 31 and a processing unit 32.
[0033] The communication unit 31 transmits and receives packets with other devices and inputs and outputs packets with the processing unit 32. The processing unit 32 includes, for example, a collection unit 320, a determination unit 321, a reference calculation unit 322, an individual calculation unit 323, an offset calculation unit 324, an estimation unit 325, and a state detection unit 326.
[0034] The collection unit 320 collects channel status information transmitted by APs 10-1 to 10-5 (corresponding to multiple transmitting devices) to a single status detection device 30 (corresponding to a receiving device) in order to transmit packets, and outputs it to the determination unit 321, the reference calculation unit 322, the individual calculation unit 323, and the estimation unit 325.
[0035] The determination unit 321 determines one of AP10-1 to 10-5 (for example, AP10-1) to be the reference device that transmits a reference packet for measuring channel state information.
[0036] The reference calculation unit 322 calculates the difference in channel state information collected by the collection unit 320 as the reference phase difference for each packet transmitted by the reference device (in this case, AP10-1) determined by the determination unit 321 at the first time (time A) and the second time (time B), and outputs the calculated reference phase difference to the offset calculation unit 324.
[0037] The individual calculation unit 323 calculates the difference in channel state information collected by the collection unit 320 as an individual phase difference for each packet transmitted by AP10-2 to 10-5, which transmit packets for measuring channel state information, at the first and second time points, excluding the reference device (in this case, AP10-1), and outputs each of the calculated individual phase differences to the offset calculation unit 324.
[0038] The offset calculation unit 324 calculates the difference between the reference phase difference calculated by the reference calculation unit 322 and the individual phase differences calculated by the individual calculation unit 323 as the respective frequency offsets, and outputs each of the calculated frequency offsets to the estimation unit 325.
[0039] The estimation unit 325 estimates channel state information that excludes the frequency offset at the third time between AP10-1 to 10-5 (multiple transmitting devices) and the state detection device 30 (receiving device), based on the frequency offset calculated by the offset calculation unit 324 and the channel state information collected by the collection unit 320 at the third time (time C), and outputs each of the estimated channel state information to the state detection unit 326.
[0040] The state detection unit 326 detects the state between AP10-1 to 10-5 (multiple transmitting devices) and the state detection device 30 (receiving device) based on the channel state information estimated by the estimation unit 325.
[0041] Thus, in the wireless communication system 1, the estimation unit 325 estimates the channel state information with the frequency offset eliminated respectively, and based on each of the channel state information estimated by the estimation unit 325, the state detection unit 326 detects the state between the plurality of transmission devices and the reception devices. Therefore, based on the channel state information used by the plurality of base stations that respectively become the transmission devices (or reception devices) to transmit packets, the operation and state of the object can be accurately and efficiently detected.
[0042] FIG. 5 is a diagram illustrating an overview of another operation of the wireless communication system 1 according to an embodiment. As shown in FIG. 5, in the wireless communication system 1, when the collection unit 320 aligns the timings (times A, B, C) for collecting CSI at the same time in the APs 10-1 to 10-5, the state detection device 30 may collect the CSI for the packets transmitted by the terminal 20 at the same time (times A, B, C).
[0043] Further, in order to align the timings (times A, B, C) for the collection unit 320 to collect CSI at the same time in the APs 10-1 to 10-5, based on a specific trigger frame, the APs 10-1 to 10-5 may send packets for measuring CSI, and the state detection device 30 may collect each of the CSI.
[0044] That is, the collection unit 320 may collect the channel state information transmitted respectively for one terminal 20 (corresponding to a reception device) to transmit packets to the APs 10-1 to 10-5 (corresponding to a plurality of transmission devices).
[0045] Further, the determination unit 321 may determine the terminal 20 (corresponding to a reception device) as a reference device that transmits a reference packet for measuring channel state information.
[0046] Note that each function of the AP 10, the terminal 20, and the state detection device 30 may be partially or entirely configured by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.
[0047] For example, the state detection device 30 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided through a network.
[0048] FIG. 6 is a diagram showing an example of the hardware configuration of the state detection device 30 according to an embodiment. As shown in FIG. 6, for example, the state detection device 30 includes an input unit 50, an output unit 51, a communication unit 52, a CPU 53, a memory 54, and an HDD 55 connected via a bus 56, and has functions as a computer. Further, the state detection device 30 is configured to be able to input and output data to and from a computer-readable storage medium 57.
[0049] The input unit 50 is, for example, a keyboard and a mouse. The output unit 51 is, for example, a display device such as a display that outputs an image. The communication unit 52 is, for example, a wired and wireless network interface, and may have a function as an output unit that outputs data to the outside.
[0050] The CPU 53 controls each part constituting the state detection device 30 and performs predetermined processing and the like. The memory 54 and the HDD 55 are storage units that store data and the like.
[0051] The storage medium 57 is capable of storing a program and the like for executing the functions of the state detection device 30. Note that the architecture of the state detection device 30 is not limited to the example shown in FIG. 6.
[0052] The functions realized by the components described in this specification may be implemented in circuitry or processing circuitry including a general-purpose processor, a specific-purpose processor, an integrated circuit, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions.
[0053] A processor includes transistors and other circuits and is considered circuitry or processing circuitry. A processor may also be a programmed processor that executes programs stored in memory.
[0054] In this specification, circuitry, unit, and means are hardware programmed to perform or execute the functions described herein. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to perform or execute the functions described herein.
[0055] If the hardware is a processor that is considered to be a type of circuitry, then the circuitry, means, or unit is a combination of hardware and software used to constitute the hardware and / or processor.
[0056] 1... Wireless communication system, 10, 10-1 to 10-5... AP, 20, 20-1, 20-2... Terminal, 30... State detection device, 31... Communication unit, 32... Processing unit, 50... Input unit, 51... Output unit, 52... Communication unit, 53... CPU, 54... Memory, 55... HDD, 56... Bus, 57... Storage medium, 320... Collection unit, 321... Determination unit, 322... Reference calculation unit, 323... Individual calculation unit, 324... Offset calculation unit, 325... Estimation unit, 326... State detection unit
Claims
1. A wireless communication system having transmitting devices and receiving devices, each equipped with a communication unit for transmitting and receiving packets, wherein a plurality of transmitting devices transmit channel state information to one receiving device, or one receiving device transmits channel state information to a plurality of transmitting devices, the system comprises: a collection unit that collects channel state information transmitted by a plurality of transmitting devices to one receiving device, or one receiving device transmits channel state information to a plurality of transmitting devices; a determination unit that determines one of the transmitting devices or the receiving device to be a reference device that transmits a reference packet for measuring channel state information; a reference calculation unit that calculates the difference in channel state information collected by the collection unit as a reference phase difference for each packet transmitted by the reference device determined by the determination unit at a first time and a second time; and an individual calculation unit that calculates the difference in channel state information collected by the collection unit as an individual phase difference for each packet transmitted by the transmitting device or the receiving device that transmits a packet for measuring channel state information at a first time and a second time, excluding the reference device. A wireless communication system comprising: an offset calculation unit that calculates the difference between the reference phase difference and each of the individual phase differences as the respective frequency offsets; an estimation unit that estimates channel state information between the transmitting device and the receiving device, with the frequency offset at the third time removed, based on the frequency offset calculated by the offset calculation unit and the channel state information collected by the collection unit at the third time; and a state detection unit that detects the state between the transmitting device and the receiving device based on the respective channel state information estimated by the estimation unit.
2. A collection unit that collects channel state information transmitted by multiple transmitting devices, each equipped with a communication unit for transmitting and receiving packets, to one receiving device equipped with a communication unit for transmitting and receiving packets, or by one of the receiving devices to multiple transmitting devices for transmitting packets; a determination unit that determines one of the transmitting devices or the receiving device to be a reference device that transmits a reference packet for measuring channel state information; a reference calculation unit that calculates the difference in channel state information collected by the collection unit as a reference phase difference for each packet transmitted by the reference device determined by the determination unit at the first time and the second time; an individual calculation unit that calculates the difference in channel state information collected by the collection unit as an individual phase difference for each packet transmitted by the transmitting device or the receiving device that transmits a packet for measuring channel state information at the first time and the second time, excluding the reference device; and an offset calculation unit that calculates the difference between the reference phase difference and each of the individual phase differences as their respective frequency offsets. A state detection device comprising: an estimation unit that estimates channel state information between the transmitting device and the receiving device with the frequency offset at the third time removed, based on the frequency offset calculated by the offset calculation unit and the channel state information collected by the collection unit at the third time; and a state detection unit that detects the state between the transmitting device and the receiving device based on the respective channel state information estimated by the estimation unit.
3. A wireless communication system having transmitting devices and receiving devices, each equipped with a communication unit for transmitting and receiving packets, wherein a plurality of the transmitting devices transmit channel state information to one of the receiving devices, or one of the receiving devices transmits channel state information to a plurality of the transmitting devices, wherein the system detects the state between the transmitting devices and the receiving devices, comprising: a collection step of collecting channel state information transmitted by a plurality of the transmitting devices to one of the receiving devices, or one of the receiving devices transmits channel state information to a plurality of the transmitting devices; a determination step of determining one of the transmitting devices or the receiving devices to be a reference device that transmits a reference packet for measuring channel state information; a reference calculation step of calculating the difference in channel state information collected by the collection step as a reference phase difference for each packet transmitted by the reference device determined by the determination step at a first time and a second time; and an individual calculation step of calculating the difference in channel state information collected by the collection step as an individual phase difference for each packet transmitted by a transmitting device or the receiving device that transmits a packet for measuring channel state information at a first time and a second time, excluding the reference device, A state detection method characterized by comprising: an offset calculation step of calculating the difference between the reference phase difference and each of the individual phase differences as the respective frequency offsets; an estimation step of estimating channel state information between the transmitting device and the receiving device, with the frequency offset at the third time removed, based on the frequency offset calculated in the offset calculation step and the channel state information collected at the third time by the collection step; and a state detection step of detecting the state between the transmitting device and the receiving device based on the channel state information estimated in the estimation step.
4. A state detection program for causing a computer to function as one of the components of the state detection device described in claim 2.