Network device and determination method

Abstract

To improve the accuracy of determining a line-of-sight state.SOLUTION: A network device includes: a measurement control unit that causes a signal transmitted from a second communication device to a first communication device to be received by each of beams in a plurality of directions and a received power to be measured for each of the beams in the plurality of directions; and a determination unit that calculates a ratio of the received power of a central direction beam including a direction from the first communication device to the second communication device to a total received power of the received power of the beams in the plurality of directions and determines a line-of-sight state between the first communication device and the second communication device in accordance with the ratio.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a network device and a determination method. [Background technology]

[0002] In recent years, with the increase in the volume of data transmitted, communication using millimeter waves has been attracting attention. Millimeter wave communication enables large-volume communication using a wide band, but has the characteristic of large propagation loss and loss due to obstruction. In order to improve communication quality, a mobile relay communication system has been developed in which a relay communication terminal (RS: Relay Station) is mounted on a mobile device such as a UAV (unmanned aerial vehicle) and the RS is moved to an appropriate location. In a mobile relay communication system, the RS forms a beam and performs wireless communication with a terminal device.

[0003] In a mobile relay communication system, in order to determine the destination of an RS, for example, the propagation path state of the destination may be determined (predicted). The propagation path state to be determined may be, for example, a line-of-sight state. The line-of-sight state indicates the presence or absence of an obstacle that blocks radio waves in the propagation path, and an environment without obstacles is called a line-of-sight environment (LOS), and an environment with obstacles is called a non-line-of-sight environment (NLOS). For example, a line-of-sight environment is preferable as the destination of an RS.

[0004] Methods for determining visibility are described in, for example, the following documents: [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2009-545934 [Patent Document 2] JP 2010-187359 A [Patent Document 3] WO2020 / 202401 issue [Patent Document 4] JP 2022-162583 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, for example, in a method that estimates line-of-sight from the relationship between radio wave reception power and distance, the accuracy of line-of-sight determination decreases when the received power varies greatly due to effects such as shadowing. If the decrease in line-of-sight determination accuracy leads to an incorrect determination of whether the state is NLOS or LOS, it may not be possible to determine an appropriate destination for the RS, and communication quality may not be improved.

[0007] Therefore, one disclosure provides a network device and a determination method that improves the accuracy of determining the visibility state. [Means for solving the problem]

[0008] The communication device includes a measurement control unit that causes a signal transmitted from a second communication device to a first communication device to be received by each of multiple directional beams and measures the received power for each of the multiple directional beams, and a determination unit that calculates a ratio of the received power of a central directional beam including a direction from the first communication device to the second communication device to the total received power of the received power of the multiple directional beams, and determines the line of sight between the first communication device and the second communication device based on the ratio. Effect of the Invention

[0009] One aspect of the present invention is to improve the accuracy of prediction of visibility conditions. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 10. As shown in FIG. [Diagram 2] FIG. 2 is a diagram illustrating an example of a configuration of the relay communication device 200. As shown in FIG. [Diagram 3] FIG. 3 is a diagram showing an example of a graph showing the relationship between distance and received power in LOS / NLOS. [Figure 4] FIG. 4 is a diagram showing an example of beams in multiple directions in LOS / NLOS. [Diagram 5] FIG. 5 is a diagram showing an example of a beam to be measured in a multi-direction beam measurement process. [Figure 6] FIG. 6 is a diagram illustrating an example of a process flowchart of the visibility state determination process S100. [Figure 7] FIG. 7 is a diagram showing an example of formula 1 taking into consideration the relationship between the transmission and reception distance and the reception power. [Figure 8] FIG. 8 is a diagram illustrating an example of Equation 5 for calculating the parameters. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] A first embodiment will be described.

[0012] <About the wireless communication system 10> 1 is a diagram showing an example of the configuration of a wireless communication system 10. The wireless communication system 10 includes a base station device 300, a relay communication device 200, and terminal devices 100-1 and 2. The wireless communication system 10 is a mobile relay communication system that performs wireless communication with the terminal devices 100-1 and 2 by moving (placing) the relay communication device 200 to an appropriate position.

[0013] The base station device 300 is a device that performs wireless communication with terminal devices 100-1 and 100-2 (hereinafter, sometimes referred to as terminal device 100) via relay communication device 200, and is, for example, an eNodeB or a gNodeB. The base station device 300 may be configured as a single device or as a plurality of devices such as a CU (Central Unit) and a DU (Distributed Unit). The base station device 300 may be wirelessly connected to the terminal device 100 and perform wireless communication without going through relay communication device 200.

[0014] The relay communication device 200 is a device that relays communication between the terminal device 100 and the base station device 300, and is, for example, an RS. The relay communication device 200 is a network device that configures a wireless communication network with the terminal device 100, the base station device 300, and the like. The relay communication device 200 is mounted on, for example, a UAV such as a drone in order to enable movement to an appropriate position. The relay communication device 200 wirelessly connects to the base station device 300 and the terminal device 100 and performs wireless communication. The relay communication device 200 measures a signal transmitted from the terminal device 100 with beams in multiple directions and executes a visibility state determination process that determines the visibility state between the terminal device 100 and the relay communication device 200. The reason for measurement with beams in multiple directions is that the signal transmitted by the terminal device 100 reaches the relay communication device 200 from multiple directions due to diffusion, reflection, and the like. Hereinafter, measuring a signal transmitted from the terminal device 100 with beams in multiple directions may be called a multi-directional beam measurement.

[0015] The terminal device 100 is a communication device that is wirelessly connected to the base station device 300 and the relay communication device 200 and performs wireless communication, and is, for example, a wireless communication device such as a smartphone or a tablet terminal.

[0016] The relay communication device 200 determines, for example, the line-of-sight state between the relay communication device 200 and the terminal device 100-1. The line-of-sight state between the relay communication device 200 and the terminal device 100-1 is LOS because there is no obstruction 400. The relay communication device 200 performs multi-directional beam measurement of the terminal device 100-1 and determines the line-of-sight state as LOS.

[0017] On the other hand, the relay communication device 200 determines the line-of-sight state between the relay communication device 200 and the terminal device 100-2, for example. The line-of-sight state between the relay communication device 200 and the terminal device 100-2 is NLOS because of the presence of an obstruction 400. The relay communication device 200 performs multi-directional beam measurement of the terminal device 100-2 and determines that the line-of-sight state is NLOS.

[0018] <Configuration Example of Relay Communication Device 200> 2 is a diagram showing an example of a configuration of the relay communication device 200. The relay communication device 200 includes a CPU (Central Processing Unit) 210, a storage 220, a memory 230, and a wireless communication circuit 250.

[0019] The storage 220 is an auxiliary storage device that stores programs and data, such as a flash memory, a hard disk drive (HDD), a solid state drive (SSD), etc. The storage 220 stores a wireless communication control program 221 and a visibility state determination program 222.

[0020] The memory 230 is an area into which the programs stored in the storage 220 are loaded. The memory 230 may also be used as an area in which the programs store data.

[0021] The wireless communication circuit 250 is a device that performs wireless communication with the terminal device 100 and the base station device 300. The relay communication device 200 forms a beam, and transmits and receives signals (messages) to and from the terminal device 100 and the base station device 300 via the wireless communication circuit 250.

[0022] The CPU 210 is a processor that loads programs stored in the storage 220 into the memory 230, executes the loaded programs, configures each unit, and realizes each process.

[0023] The CPU 210 performs wireless communication control processing by executing the wireless communication control program 221. The wireless communication control processing is processing for establishing a wireless connection with the terminal device 100 and the base station device 300, and relaying wireless communication of the terminal device 100. In the wireless communication control processing, the relay communication device 200 transmits a signal received from the terminal device 100 to the base station device 300, and transmits a signal received from the base station device 300 and addressed to the terminal device 100, to the terminal device 100.

[0024] The CPU 210 executes the visibility state determination program 222 to construct a measurement unit and a determination unit, and performs visibility state determination processing. The visibility state determination processing is processing for determining the visibility state between the relay communication device 200 and the terminal device 100. In the visibility state determination processing, the relay communication device 200 performs multi-directional beam measurement and determines the visibility state between the relay communication device 200 and the terminal device 100.

[0025] <Accuracy of visibility assessment> The accuracy of determining the line-of-sight state will now be described. Fig. 3 is a diagram showing an example of a graph showing the relationship between distance and received power in LOS / NLOS. In the graph of Fig. 3, the vertical axis shows received power, and the horizontal axis shows distance. The distance is, for example, the distance between the terminal device 100 and the relay communication device 200. The graph of Fig. 3 also shows expected power in the case of LOS and expected power in the case of NLOS.

[0026] For example, sample data D1 and D2 are close to the graph of expected power for LOS and are located within a predetermined range, so it is clear that they are data on received power in LOS. Also, for example, samples D3 and D4 are close to the graph of expected power for NLOS and are located within a predetermined range, so it is clear that they are data on received power in NLOS.

[0027] However, for example, the data of sample data D5 is located near the middle between the graph of expected power for LOS and the graph of expected power for NLOS, making it difficult to determine whether the measurement environment is LOS or NLOS.

[0028] In this way, depending on the data, it may be difficult to determine visibility simply from the relationship between received power and distance, and accuracy may decrease.

[0029] <Characteristics of reception power depending on line of sight> The difference in received power due to line-of-sight conditions will be described below. Fig. 4 is a diagram showing an example of receiving signals in LOS / NLOS with beams in multiple directions. Note that the directions described below refer to directions relative to the front direction of the antenna of relay communication device 200.

[0030] FIG. 4(A) is a diagram showing an example of a signal in LOS. Among the signals transmitted from the terminal device 100, the one propagating along the path in the direction of the relay communication device 200 (hereinafter, sometimes referred to as the center direction) is called a signal (reference signal) R1. In addition to the signal R1 propagating along the path in the center direction, there are signals R2 and R3 that reach the relay communication device 200 along a path different from the signal R1 due to reflection or the like. At this time, the signal R1 in the center direction attenuates according to the distance, but has a significantly larger received power than the signals R2 and R3 that arrive due to diffusion or reflection. At this time, each signal is received by a beam in a direction that matches the angle of the signal that arrives at the relay communication device 200. The received power by the beam in a direction that matches the angle of the signal in the center direction is called the received power of the beam in the center direction. The received power by the beam in a direction that matches the angle of the signal R2 and the signal R3 is called the received power of the beam R2 and the received power of the beam R3, respectively. Hereinafter, the received power of beam R2 and the received power of beam R3 may be referred to as the received power of beams in other directions. FIG. 4B is a diagram showing an example of a signal in NLOS. Among the signals transmitted from the terminal device 100, the one propagating along the route toward the center is called signal R4. In addition to the signal R4 propagating along the route toward the center, there are signals R5 and R6 that reach the relay communication device 200 along a route different from the signal R4 due to reflection or the like. At this time, the signal R4 in the center direction is attenuated not only according to the distance, but also due to collision with the shield 400. Therefore, the received power of the signal R4 is smaller by the amount of attenuation due to the shield 400 compared to the signal R1 in the center direction in the LOS of FIG. 4A. On the other hand, when the signals R5 and R6 do not collide with the shield 400, the received power is about the same as that of the signals R2 and R3 in FIG. 4A. It is assumed that each signal is received by a beam in a direction that matches the angle of the signal that reaches the relay communication device 200. The received power by the beam in the direction that matches the angle of the central signal is called the received power of the central beam. The received power by the beam in the direction that matches the angles of signals R5 and R6 are called the received power of beam R5 and beam R6, respectively. Hereinafter, the received power of beam R5 and the received power of beam R6 may be called the received power of beams in other directions.

[0031] In this way, the received power of the central beam in NLOS is smaller than that of the central beam in LOS. On the other hand, the received power of the beams in other directions does not change significantly whether it is NLOS or LOS. In other words, it can be assumed that the ratio of the received power of the central beam to the received power of the beams in other directions in NLOS is smaller than the ratio of the received power of the central beam to the received power of the beams in other directions in LOS.

[0032] Therefore, in the line-of-sight condition determination process in the first embodiment, this assumption is utilized to calculate the ratio of the received power of the beam in the central direction to the total value of the received power of the beams in a specified direction, and the line-of-sight condition (whether it is LOS or NLOS) is determined using the calculated ratio.

[0033] <Multi-directional beam measurement processing> A multi-directional beam measurement process will now be described. Fig. 5 is a diagram showing an example of a signal to be measured in the multi-directional beam measurement process. Fig. 5 is a diagram showing, for example, relay communication device 200 and terminal device 100 as viewed from above. Measuring beams in multiple directions can be interpreted as, for example, receiving and measuring signals with multiple antennas facing different directions. Alternatively, measuring beams in multiple directions can be interpreted as receiving and measuring signals in multiple directions by electrically controlling each of multiple antennas to give beam directionality.

[0034] The relay communication device 200 measures the signal R10 in the central direction as the measurement target of the received power. Signals shifted from the central direction by a predetermined angle (θ) are also measured. For example, in FIG. 5, the signal R10 in the central direction and signals R11 and R12 shifted by a predetermined angle θ in the horizontal direction are measured. In addition, signals R13 and R14 shifted by a predetermined angle θ in the horizontal direction from signals R11 and R12 are also measured. Note that each signal is received by a beam in a direction that matches the angle of the signal arriving at the relay communication device 200. The received power by the beam in a direction that matches the angle of the signal in the central direction is called the received power of the beam in the central direction. The received power by the beam in a direction that matches the angle of signals R11, R12, R13, and R14 are called the received power of beam R11, the received power of beam R12, the received power of beam R13, and the received power of beam R14, respectively. Hereinafter, the received power of beam R11, beam R12, beam R13, and beam R14 may be referred to as the received power of beams in other directions. Also, the beam in the direction that matches the angle of the signal to be measured is referred to as the beam to be measured or the beam to be measured.

[0035] The number of beams to be measured and the specified angle θ are determined, for example, according to the receiving sensitivity and performance of the antenna, the measurement environment (including, for example, the presence or absence of reflectors, temperature, humidity, etc.), and the processing power of the processor of the relay communication device 200.

[0036] 5 shows an example in which the predetermined angle θ is the horizontal direction and all beams have the same vertical direction. However, the beam to be measured may be shifted in the horizontal direction α and the vertical direction β, for example, and the predetermined number may be determined by shifting the beam in the horizontal direction and the vertical direction.

[0037] In addition, in Fig. 5, the beam to be measured is determined by shifting it by a predetermined angle θ, but the shift angle does not have to be always the same. For example, the shift angle may be smaller the closer to the center. The shift angle may also be determined based on past measurement data.

[0038] <Visibility state determination process> The visibility state determination process S100 will be described below. Fig. 6 is a diagram showing an example of a process flowchart of the visibility state determination process S100. The relay communication device 200 executes the visibility state determination process S100 at a predetermined timing.

[0039] In the visibility state determination process S100, the relay communication device 200 calculates the direction (center direction) of the terminal device 100 from the position information of the terminal device 100 (S100-1).

[0040] The relay communication device 200 measures the received power of beams at a predetermined angle centered on the direction of the terminal device 100 (S100-2). For example, as shown in FIG 5, the relay communication device 200 measures a beam R10 in the central direction and beams R11 to R14 in the other four directions.

[0041] The relay communication device 200 calculates the ratio of the received power of the beam in the direction (center direction) of the terminal device 100 to the total received power of all beams (S100-3). When measuring the beams in FIG. 5, for example, the relay communication device 200 calculates the ratio of the received power of beam R10 to the total value of the received power of beams R10 to R14.

[0042] The relay communication device 200 compares the calculated ratio with a first threshold (S100-5). The first threshold is a threshold used to determine whether or not there is LOS. For example, when the ratio is larger than (or equal to or larger than) the first threshold, the relay communication device 200 determines that there is LOS.

[0043] The first threshold is determined, for example, from past measurement data and is stored in advance in a memory of the relay communication device 200. For example, the fewer the number of beams to be measured, the smaller the total value of the received power of all beams becomes, and therefore the ratio of the received power of the beam in the center direction becomes larger. Based on this assumption, the smaller the number of measured beams, the larger the first threshold is set.

[0044] Also, for example, the wider the beam to be measured, the more multipath components are contained in the beam in the center direction, and therefore the ratio of the received power of the beam in the center direction becomes large. Based on this assumption, the larger the width of the measurement beam, the larger the first threshold value is set.

[0045] If the ratio is equal to or greater than the first threshold (Yes in S100-5), the relay communication device 200 determines that the signal is LOS (S100-6) and ends the process.

[0046] On the other hand, if the ratio is not equal to or greater than the first threshold (No in S100-5), the relay communication device 200 determines that the signal is NLOS (S100-7) and ends the process.

[0047] In the first embodiment, by determining LOS or NLOS from the ratio of the received power of the beam in the central direction, it is possible to prevent a decrease in the determination accuracy even if the overall received power varies.

[0048] [Second embodiment] A second embodiment will be described below. In the second embodiment, the relay communication device 200 determines the line of sight state by taking into consideration the relationship between the transmission and reception distance and the reception power (for example, the graph in FIG. 3).

[0049] FIG. 7 is a diagram showing an example of formula 1 taking into consideration the relationship between the transmission and reception distance and the reception power.

[0050] z in Eq. nk (θ) indicates the probability that data sample n is LOS (or NLOS). k=1 is LOS, and k=2 is NLOS. The relay communication device 200 nk The k for which (θ) is maximized is determined as the visibility state of data sample n.

[0051] π k (u n ,w) is the beam power ratio u n The probability of LOS (or NLOS) corresponding to k = 1 is expressed by Equation 2, and the probability of k = 2 is expressed by Equation 3.

[0052] u n indicates the ratio of received power of the beam in the center direction of data sample n. w is a parameter, expressed as w = [w1, w0]. w1 is a weighting parameter for the ratio, and w0 is a bias parameter for the beam power ratio.

[0053] N nk D denotes the probability that the received power of data sample n is obtained in the case of LOS (or NLOS), and is expressed by Equation 4. n denotes the distance (logarithm) between the transmitter and receiver of data sample n. y n denotes the received power (logarithm) of data sample n. For example, N n1 denotes the probability of obtaining received power yn in the case of LOS.

[0054] θ denotes a parameter set (α1, β1, σ1, α2, β2, σ2, w0, w1). αk is a distance attenuation parameter of the received power. βk is an offset parameter of the received power. σk is a standard deviation parameter of the variation of the received power. The parameter set θ is calculated, for example, from past measured values, and is preset in the relay communication device 200.

[0055] In the second embodiment, the visibility can be determined by further taking into account the relationship between distance and received power.

[0056] [Third embodiment] A third embodiment will be described. In the third embodiment, data acquired at various positions is collectively managed and utilized, and thus no prior parameter setting is performed. The relay communication device 200 determines parameters based on the acquired data so that the likelihood of Equation 5 in FIG. 8 is maximized. M indicates the number of data samples.

[0057] The process after the parameters are calculated in Equation 5 is the same as that in the second embodiment.

[0058] [Other embodiments] The visibility state determination process S100 may be executed, for example, by the base station device 300 or a control device (not shown) connected to the base station device 300. When the visibility state determination process S100 is executed by the base station device 300 or the control device, the relay communication device 200 transmits the measurement result to a device that executes the visibility state determination process. Furthermore, the relay communication device 200 executes the multi-directional beam measurement process according to (in response to) an instruction from the control device or the base station device 300. The control device is, for example, a device that controls the base station device 300, and is a network device.

[0059] Also, the visibility state determination process S100 may be executed, for example, by the terminal device 100. When the visibility state determination process is executed by the terminal device 100, the terminal device 100 measures the signal transmitted from the relay communication device 200 with beams in multiple directions and determines the visibility state.

[0060] The result of the determination of the visibility is transmitted to, for example, the control device or the base station device 300 and is used to determine the destination of the relay communication device 200 in the wireless communication system 10.

[0061] To summarise, the following is an appendix.

[0062] (Appendix 1) a measurement unit that receives a signal transmitted from a second communication device as a plurality of signals in beams in different directions in the first communication device and measures a received power for each of the received beams; a determination unit that calculates a ratio of a reception power of a central direction beam including a direction from the first communication device to the second communication device to a total reception power of the reception powers of the plurality of beams, and determines a line-of-sight state between the first communication device and the second communication device according to the ratio. A first communication device.

[0063] (Appendix 2) a measurement control unit that causes a signal transmitted from the second communication device to the first communication device to be received by each of beams in a plurality of directions and measures a received power for each of the beams in the plurality of directions; a determination unit that calculates a ratio of a reception power of a central direction beam including a direction from the first communication device to the second communication device to a total reception power of the reception powers of the beams in the multiple directions, and determines a line of sight state between the first communication device and the second communication device in accordance with the ratio. Network device.

[0064] (Appendix 3) The determination unit determines that the visibility state is a line-of-sight environment when the ratio is greater than a first threshold value. 3. The network device of claim 2.

[0065] (Appendix 4) The first threshold value is set to a larger value as the number of beams measured in the first communication device is smaller. 4. The network device of claim 3.

[0066] (Appendix 5) The first threshold value is set to a larger value as the beam width of each beam becomes wider. 4. The network device of claim 3.

[0067] (Appendix 6) The determination unit calculates an inter-device distance between the first communication device and the second communication device, and determines the line-of-sight state according to the ratio and the inter-device distance. 3. The network device of claim 2.

[0068] (Appendix 7) receiving a signal transmitted from a second communication device to a first communication device as a plurality of signals in beams in different directions at the first communication device, and measuring a received power for each of the received beams; Calculating a ratio of a received power of a central direction beam including a direction from the second communication device to the first communication device to a total received power of the received powers of the plurality of beams, and determining a line-of-sight state between the first communication device and the second communication device according to the ratio. Judgment method.

[0069] (Appendix 8) A signal transmitted from a second communication device to a first communication device is received by each of beams in a plurality of directions, and a received power is measured for each of the beams in the plurality of directions; Calculating a ratio of a received power of a central direction beam including a direction from the first communication device to the second communication device to a total received power of the received powers of the beams in the multiple directions, and determining a line-of-sight state between the first communication device and the second communication device according to the ratio. Judgment method.

[0070] (Appendix 9) The first communication device is a relay communication device that relays wireless communication between a base station device and the second communication device. 2. The first communication device of claim 1. [Explanation of symbols]

[0071] 10: Wireless communication systems 100: Terminal device 200: Relay communication device 210: CPU 220: Storage 221: Wireless communication control program 222: Visibility assessment program 230: Memory 250: Wireless communication circuit 300:Base station equipment 400: Shield

Claims

1. a measurement control unit that causes a signal transmitted from the second communication device to the first communication device to be received by each of beams in a plurality of directions and measures a received power for each of the beams in the plurality of directions; a determination unit that calculates a ratio of a reception power of a central direction beam including a direction from the first communication device to the second communication device to a total reception power of the reception powers of the beams in the multiple directions, and determines a line-of-sight state between the first communication device and the second communication device in accordance with the ratio. Network device.

2. The determination unit determines that the visibility state is a line-of-sight environment when the ratio is greater than a first threshold value. The network device according to claim 1.

3. The first threshold value is set to a larger value as the number of beams measured in the first communication device is smaller.

3. The network device according to claim 2.

4. The first threshold value is set to a larger value as the beam width of each beam becomes wider.

3. The network device according to claim 2.

5. The determination unit calculates an inter-device distance between the first communication device and the second communication device, and determines the line-of-sight state according to the ratio and the inter-device distance. The network device according to claim 1.

6. A signal transmitted from the second communication device to the first communication device is received by each of beams in a plurality of directions, and a received power is measured for each of the beams in the plurality of directions; Calculating a ratio of a received power of a central direction beam including a direction from the first communication device to the second communication device to a total received power of the received powers of the beams in the multiple directions, and determining a line-of-sight state between the first communication device and the second communication device according to the ratio. Judgment method.

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