JP2021150870A - Electromagnetic wave detection device, electromagnetic wave detection method, and program - Google Patents

Abstract

To provide an electromagnetic wave detection device capable of improving detection accuracy while simplifying a calculation step in a propagation path loss estimation in a propagation path of an electromagnetic wave in order to detect a blank frequency resource, an electromagnetic wave detection method, and a program.SOLUTION: An electromagnetic wave detection device comprises: an acquisition part acquiring land form data in a propagation path between a transmission part transmitting an electromagnetic wave and a reception part receiving the electromagnetic wave at a position optionally set; a detection part detecting at least one of shields shielding the propagation path on the basis of land form data acquired by the acquisition part; and a calculation part calculating propagation loss of the electromagnetic wave in the propagation path on the basis of a diffraction loss generated by diffraction in each shield.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radio wave detection device, a radio wave detection method, and a program for improving frequency utilization efficiency.

In recent years, with the spread of smartphones and related applications, the traffic volume in the mobile communication field has been increasing year by year (see Non-Patent Documents 1 and 2). Therefore, from 2020, the operation of the 5th generation mobile communication system (5G) that enables high-speed communication, low latency, and multiple access is scheduled to start in sequence. However, 5G 26GHz band radio waves, which will be put into operation at an early stage, have already been assigned to fixed wireless access (FWA) in Japan (see Non-Patent Document 3). In order to improve frequency utilization efficiency, the introduction of a dynamic frequency sharing technology that can avoid radio wave interference between both systems is being studied (see Non-Patent Document 4).

In the dynamic frequency sharing technology, wireless communication systems are classified into Primary users (PUs) and Secondary users (SUs) according to the priority of using the frequency band (spectrum). FWAs are classified as Pus and 5G systems are classified as SUs. In order to protect the communication of FWA which is Pus, before starting the communication in the 5G system which is SU, the area where the radio wave of FWA which does not interfere with the communication of FWA does not reach is extracted, and the area where the radio wave of FWA does not reach is extracted and the area of the 5G system is used. You need to make sure that you can allocate a frequency band. In order to determine the commonable area between the FWA and the 5G system, for example, a propagation loss estimation model for estimating the loss in the propagation path of radio waves is being studied.

Known free space propagation models and statistical propagation models are known for propagation loss estimation. However, when a known free space propagation model or statistical propagation model is used in the propagation loss estimation, the difference between the measured value and the estimated value may become large (see Non-Patent Documents 5 and 6). In addition, in the propagation loss estimation by the free space propagation model or the statistical propagation model, the estimated operation area of PUs may be overestimated, the area where SUs can be used is underestimated, and SUs is a transmission opportunity. May lose.

As another method for estimating the propagation loss, the propagation loss estimation to which Kirchhoff approximation (KA) is applied is known (see Non-Patent Document 7). For the propagation loss estimation using KA, a method of calculating the propagation loss caused by the building is known on the assumption that the dominant incoming wave in the urban environment propagates over the roof of the building (Non-Patent Document 8). See 10).

Cisco, “Cisco Visual Networking Index: Forecastand Trends, 2017-2022” [Online] .Available: https://www.cisco.com/c/ja_jp/solutions/collateral/service-provider/visual-networking-index-vni /white-paper-c11-741490.html, Feb, 2019 Ericsson, “Ericsson mobility report”, Ericsson, Tech.Rep., November 2018 [Online]. Available: https://www.ericsson.com/res/docs/2016/ericsson-mobility-report-2018.pdf Ministry of Internal Affairs and Communications, “Fre-quency Allocation Table Table-3 (10GHz-275GHz)” In-ternet: https://www.tele.soumu.go.jp/e/adm/freq/search/share/ plan.htm, Feb, 2019 [Sep 4th, 2019] S. Haykin, “Cognitive radio: brain-empowered wireless com-munications,” IEEE J. Sel. Areas Commun, vol. 23, no. 2, pp. 201-220, Feb. 2005 C. Phillips et al., “Bounding the error of path loss models,” in Proc. DySPAN, Aachen, 2011, pp. 71-82. A. Achtzehn et al., “Improving accuracy for TVWS geolo-cation databases: Results from measurementdriven estima-tion approaches,” in Proc. DYSPAN 2014, VA, 2014, pp.392-403 M. Born and E. wolf, “Principles of Optics,” 2nd ed. NewYork: Pergamon, 1964, pp. 375-382. J. Walfisch and H.L. Bertoni, “A theoretical model of UHFpropagation in urban environments,” IEEE Trans. AP, vol.36, no. 12, pp. 1788-1796, Dec. 1988. Chung et al, “Range-dependent path-loss model in residen-tial areas for the VHF and UHF,” IEEE Trans. AP, vol.50, no. 1, pp. 1-11, Jan. 2002. Ying Xu, et al, “Fresnel-Kirchhoff integral for 2-D and 3-Dpath loss in outdoor urban environments,” IEEE Trans.AP, vol. 53, no. 11, pp. 3757-3766, Nov. 2005 Kriangsak, et.al, “Experimental Analysis and Site-Specific Modeling of Channel Parameters at Mobile Station in an Urban Macrocelluar Environment,” IEICE Trans. Com-mun., Vol.E91-B, No.4, pp.1132-1144, Apr . 2008 Kriangsak, et.al, “Full polarimetric 3-D double directional channel measurement in a NLOS macrocellular environ-ment,” IEICE Technical Report, vol. 105, no. 467, AP2005-117, pp. 7-12, Dec. 2005 A. Kuchar, et al., “Directional macro-cell channel charac-terization from urban measurements,” in IEEE Trans. AP, vol. 48, no. 2, pp. 137-146, Feb. 2000. Ghoraishi, et.al, “Analysis of the Propagation Meachanismsin Streets with Different Directions in Urban Mobile Ra-dio Channels,” IEICE Technical Report vol. 108, no. 429, AP2008-190, pp. 7-12, Feb. 2009. J. Medbo, et.al, “Directional channel characteristics in el-evation and azimuth at an urban macrocell base station,” 2012 6th EUCAP, Prague, 2012, pp. 428-432 N.Kita et.al, “Path Loss Prediction Model for the Over-Rooftop Propagation Environment of Microwave Band in Suburban Areas,” IEICE Trans. Commun (B), vol. J89-B, no. 2, pp. 115-125, Feb. 2006. (in Japanese) N.Kita et.al, “New method for evaluating height gain atsubscriber station for wireless access systems in microwaveband,” IEICE Trans. Commun (B), E90-B, pp.2903-2914, Oct. 2006. H. Zhao et al., “28 GHz millimeter wave cellular communi-cation measurements for reflection and penetration loss inand around buildings in New York city,” 2013 IEEE ICC, Budapest, 2013, pp. 5163-5167 S. Deng, et al., “Indoor and Outdoor 5G Diffraction Mea-surements and Models at 10, 20, and 26 GHz,” 2016 IEEE Global Communications Conference (GLOBECOM), Wash-ington, DC, 2016, pp. 1-7 .. H. Ling, et al., “Shooting and bouncing rays: calculating the RCS of an similarly shaped cavity,” in IEEE Trans-actions on Antennas and Propagation, vol. 37, no. 2, pp.194-205, Feb. 1989 .. G. Liang et al., “A new approach to 3-D ray tracing forpropagation prediction in cities,” in IEEE Transactions onAntennas and Propagation, vol. 46, no. 6, pp. 853-863, June199 REMCOM, “Wireless Insite,” https://www.remcom.com/wireless-insite-em-propagation-software

Generally, the evaluation of these models is performed by comparing the difference between the measured value and the estimated value. In the comparison in dynamic frequency sharing, the accuracy of detection accuracy for estimating whether or not the corresponding spectrum is free is the most important. However, the existing literature does not discuss the applicability of KA in the millimeter wave band and the spectrum detection accuracy when applied to dynamic frequency sharing.

Furthermore, the KA model considers only cross-roof propagation as the dominant incoming wave and does not consider the effects of other reflected waves at all. Since the incoming wave arrives via various propagation paths, it is necessary to calculate the propagation loss estimation in consideration of the propagation model that simplifies the propagation of the incoming wave. Therefore, in order to calculate the propagation loss estimation, it is necessary to grasp the change in the spectrum detection accuracy due to the simplification of the incoming wave.

The present invention provides a radio wave detection device, a radio wave detection method, and a program capable of improving the detection accuracy while simplifying the calculation process in the propagation loss estimation in the radio wave propagation path for detecting a free frequency resource. The purpose is to do.

The present invention includes an acquisition unit that acquires topographical data in a propagation path between a transmission unit that transmits radio waves and a reception unit that receives the radio waves at an arbitrarily set position, and the acquisition unit acquired by the acquisition unit. A detection unit that detects at least one obstruction that shields the propagation path based on topographical data, and a calculation unit that calculates the propagation loss of the radio wave in the propagation path based on the diffraction loss generated by diffraction in the obstruction. It is a radio wave detection device including.

In the present invention, a computer acquires terrain data between a transmitting unit that transmits radio waves and a receiving unit that receives the radio waves at an arbitrarily set position, and based on the terrain data, the transmitting unit and the transmitting unit A radio wave that detects at least one shield that blocks the propagation path of the radio wave with the receiving unit, and calculates the propagation loss of the radio wave in the propagation path based on the diffraction loss generated by diffraction in the shield. It is a detection method.

The present invention causes a computer to acquire terrain data between a transmitting unit that transmits radio waves and a receiving unit that receives the radio waves at an arbitrarily set position, and based on the terrain data, the transmitting unit and the transmitting unit A program that detects at least one shield that shields the radio wave propagation path with the receiving unit, and calculates the radio wave propagation loss in the propagation path based on the diffraction loss generated by diffraction in the shield. Is.

In the propagation loss estimation in the radio wave propagation path for detecting the free frequency resource, the detection accuracy can be improved while simplifying the calculation process.

It is a figure which shows the structure of the radio wave detection device which concerns on embodiment of this invention. It is a figure which shows the pattern of the arrival wave in an urban area. It is a figure explaining the existing propagation loss estimation model. It is a figure explaining the propagation loss estimation model which concerns on the proposed method. It is a figure which shows the measurement point in the measurement target area. It is a figure which shows the measurement specification used in an experiment. It is a figure which shows the received signal strength based on the measurement result. It is a figure which shows the detection result by the proposed model. It is a figure which shows the result of having compared the detection accuracy of the proposed method and the existing method. It is a figure which shows the verification target area for verifying the detection result. It is a figure which shows the arrival angle and delay characteristic in the area to be verified. It is a figure which shows the arrival angle and delay characteristic in the verification target area where the arrival wave and the reflected wave were observed. It is a figure which shows the verification target area where the incoming wave and the reflected wave were observed. It is a figure explaining the propagation loss estimation model which concerns on the proposed method considering the influence of a reflected wave.

Hereinafter, the radio wave detection device, the radio wave detection method, and the program according to the embodiment of the present invention will be described. The radio wave detection device is a simulation device that determines an area in which radio waves transmitted from a base station propagate. First, the configuration of the radio wave detection device will be described.

As shown in FIG. 1, the radio wave detection device 1 is connected to the network NW. For example, a server S that stores various types of information is connected to the network NW. The radio wave detection system may be configured by the radio wave detection device 1 and the server S connected via the network NW. The radio wave detection device 1 is an information processing terminal composed of, for example, a personal computer or the like. The server S stores 3D map data and provides the data via the network NW.

The radio wave detection device 1 includes an acquisition unit 2 that acquires topographical data, a detection unit 4 that detects a shield such as a building in a radio wave propagation path based on predetermined data, and a calculation unit that calculates a propagation loss in the propagation path. A storage unit 8 for storing various data, a display unit 10 for displaying calculation results, and a communication unit 12 connected to a network NW for transmitting and receiving data are provided.

The acquisition unit 2 acquires topographical data in a target area including a radio wave propagation path via, for example, a communication unit 12. The acquisition unit 2 acquires, for example, topographical data available from the network NW. The terrain data includes 3D data such as the shape of the ground surface and altitude included in the 3D map data, and 3D data such as the shape and height of the outer circumference of the building.

The acquisition unit 2 acquires, for example, data related to a transmission unit that transmits radio waves. The transmitter is, for example, a radio base station. The acquisition unit 2 acquires data such as the position of the transmission unit, the height of the antenna, and the communication function. As will be described later, the transmission unit is a communication facility that transmits radio waves in a target frequency band. Transmission units are provided for each predetermined communication range (cell) on the ground surface. In the present embodiment, the transmission unit is virtually set and does not have to exist in reality. Since the transmission unit is set at an arbitrary position, the acquisition unit 2 may automatically generate data regarding the transmission unit at an arbitrary position.

The acquisition unit 2 acquires, for example, data related to a receiving unit that receives radio waves. The acquisition unit 2 acquires data such as the position and height of the receiving unit, for example. As will be described later, the receiving unit is a radio base station that receives radio waves in the target frequency band. In the present embodiment, the receiving unit is virtually set and does not have to exist in reality. The receiving unit receives radio waves at an arbitrarily set position. The receiving unit may be a mobile terminal device. Since the receiving unit is set at an arbitrary position, the acquiring unit 2 may automatically generate data relating to the receiving unit at an arbitrary position. The data acquired by the acquisition unit 2 may be stored in the storage unit 8.

The acquisition unit 2 acquires topographical data in the target area of the simulation. The acquired terrain data is read by the detection unit 4.

When the transmitting unit and the receiving unit are determined, the detecting unit 4 extracts the terrain data between the transmitting unit and the receiving unit. The detection unit 4 defines a line-of-sight (LoS) wave traveling from the BS to each MS in a linear propagation path. The detection unit 4 extracts shape data including the height of the ground surface in a vertical cross section including a straight line connecting the transmission unit and the reception unit, and shape data including the height of the building.

The detection unit 4 calculates the elevations of the antennas of the transmission unit BS and the reception unit MS based on the terrain data and the data related to the transmission unit BS and the reception unit MS. The altitude of the antenna is calculated by adding the height of the antenna to the height of the ground surface (see FIG. 4). The detection unit 4 calculates the direction and distance of the propagation path D based on the elevations of the antennas of the transmission unit BS and the reception unit MS, with the straight line connecting the antennas of the transmission unit BS and the reception unit MS as the propagation path D ( (See FIG. 4).

The detection unit 4 refers to the terrain data and detects at least one shield that shields radio waves in the propagation path D. The shield is calculated by adding the height of the building to the height of the ground surface (see FIG. 4). The detection unit 4 uses the building ID included in the terrain data to extract the building height at the coordinates intersecting the propagation path D.

The detection unit 4 extracts a building that intersects the propagation path D as a shield. In the propagation path D, the detection unit 4 detects the first shield (edge 1) that first intersects from the transmission unit along the direction of the propagation path (see FIG. 4). The detection unit 4 refers to the elevation information (h _terrain ) of the ground surface closest to the intersection. The altitude information is the height of the ground surface in the area divided in a mesh shape on the map data.

The detection unit 4 refers to the building edge height (h _building ) at the intersection. The detection unit 4 calculates the edge height of the shield by using the altitude information of the nearest neighbor from the intersection as the altitude. The detection unit 4 calculates the edge height (H _edge ) of _{the shield by adding the elevation (h terrain} ) of the ground surface and the building edge height (h _building ) at the coordinates of the intersection.

The detection unit 4 calculates the distance d between the first shield and the second shield. The detection unit 4 detects the second shield (edge 2) that first intersects from the reception unit along the direction of the propagation path (see FIG. 4). Further, the detection unit 4 detects a reflector that reflects radio waves in the receiving unit in the direction opposite to the propagation path, that is, on the side opposite to the transmitting unit when viewed from the receiving unit. The detected shield and reflector data are read out by the calculation unit 6.

The calculation unit 6 calculates the propagation loss of radio waves in the propagation path based on the _{diffraction loss L shadowed} generated by diffraction in the shield. The calculation unit 6 calculates the free space propagation loss that is attenuated according to the distance in the propagation path based on the free space propagation loss model described later.

The calculation unit 6 calculates the diffraction loss generated by diffraction at the upper edge of the shield in the propagation path. The calculation unit 6 calculates the first diffraction loss generated in the first shield. The calculation unit 6 calculates the second diffraction loss generated in the second shield. The calculation unit 6 calculates the diffraction loss based on the first diffraction loss and the second diffraction loss.

The calculation unit 6 calculates the diffraction loss based on the Kirchhoff approximation, as will be described later. As will be described later, the calculation unit 6 calculates the propagation loss of radio waves in the propagation path based on the reflection effect generated by the reflected wave reflected from the reflector. _{The calculation unit 6 calculates the final propagation loss L total} of the radio wave in the propagation path based on the free space propagation loss L _fspl , the diffraction loss L _shadowed , and the reflection influence P _reflection .

The calculation unit 6 calculates the propagation loss of radio waves in the propagation path based on the free space propagation loss when the shield and the reflector are not present. The calculation unit 6 calculates the propagation loss of radio waves in the propagation path according to the presence of a shield and a reflector. When a shield is present, the calculation unit 6 calculates the final propagation loss based on the free space propagation loss and the diffraction loss. The calculation unit 6 calculates the final propagation loss based on the free space propagation loss, the diffraction loss, and the reflection effect when the shield and the reflector are present.

The calculation unit 6 calculates the received power value in the receiving unit based on the free space propagation loss and the diffraction loss and / or the reflection effect.

The calculation unit 6 compares the calculated received power value with a preset threshold value. The calculation unit 6 compares the calculated received power value with the threshold value, and if the received power value is less than the threshold value, determines that the radio wave band is vacant at the position of the receiving unit. When the received power value is equal to or greater than the threshold value, the calculation unit 6 determines that the radio wave band is not open.

The processing flow of the radio wave detection method executed by the radio wave detection device 1 is as follows. The acquisition unit 2 acquires terrain data between a transmission unit that transmits radio waves and a reception unit that receives radio waves at an arbitrarily set position. The detection unit 4 detects at least one shield that shields the propagation path of the radio wave between the transmission unit and the reception unit based on the terrain data. The calculation unit 6 calculates the propagation loss of radio waves in the propagation path based on the diffraction loss generated by diffraction in the shield.

Then, the program installed in the radio wave detection device 1 causes the radio wave detection device 1 to perform the following processing. The terrain data between the transmitting unit that transmits radio waves and the receiving unit that receives radio waves at an arbitrarily set position is acquired. Based on the terrain data, at least one shield that blocks the radio wave propagation path between the transmitting unit and the receiving unit is detected. The propagation loss of radio waves in the propagation path based on the diffraction loss generated by diffraction in the shield is calculated.

Each component of the acquisition unit 2, the detection unit 4, and the calculation unit 6 described above is realized by, for example, executing a program (software) by a hardware processor such as a CPU (Central Processing Unit). Some or all of these components are hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), GPU (Graphics Processing Unit) It may be realized by (including circuits), or it may be realized by the cooperation of software and hardware. The program may be stored in advance in a storage device such as an HDD (Hard Disk Drive) or a flash memory, or is stored in a removable storage medium such as a DVD or a CD-ROM, and the storage medium is stored in the drive device. It may be installed by being attached.

The storage unit 8 is a storage device such as an HDD (Hard Disk Drive) or a flash memory. The storage unit 8 stores data such as terrain data and threshold values acquired by the acquisition unit 2, as well as a program for executing the processing of the calculation unit 6. Data and programs may be stored in the server S connected to the network NW.

As the display unit 10, for example, a display device such as a liquid crystal display, an LED (Light Emitting Diode) display, an organic EL (Organic Electro-Luminescence) display, a digital mirror device (Digital Mirror Device), or a plasma display is used.

The communication unit 12 is an interface including a communication device for connecting to the network NW. The communication unit 12 has a communication device having a wireless LAN, a wired LAN, Bluetooth (registered trademark), etc., and is connected to the network NW.

Next, the mechanism by which radio waves propagate will be described.

It is assumed that the environment in which 5G and FWA, to which dynamic frequency sharing technology is applied, coexist is mainly in urban areas. Various studies have been conducted in the past on the measurement of radio wave propagation in urban environments (see Non-Patent Documents 11 to 14).

As shown in FIG. 2, Kriangsak et al. Show the incoming waves in the urban environment according to the positions of the base station (BS, transmitter) and mobile station (MS, receiver) below (1) to (4). It is classified into four types (see Non-Patent Document 11). (1) BS-direction: The main direction of arrival wave in a certain MS points to the direction of BS. It has multiple reflections due to buildings before and after MS. (2) Opposite BS-direction: The main direction of the incoming wave is the direction opposite to the BS. Like BS-direction, it has reflection caused by the building behind MS.

(3) Street direction: It arrives in the direction along the road. Multiple waves repeatedly reflect from the wall of the building along the road and arrive at the MS. (4) Rooftop-diffraction: It arrives over the roof of the building between BS and MS. Therefore, it is expected that the elevation angle is the largest. Above all, when the height of the base station is higher than the height of the surrounding buildings, (4) Rooftop diffraction is dominant (see Non-Patent Documents 16 and 17), and about 65% or more of the power goes through the roof. It has been clarified that it has arrived (see Non-Patent Document 13).

Furthermore, even if the MS is NLoS when viewed from the BS, it has been clarified that (2) Opposite BS-direction contributes when there is a relatively tall building far behind the MS (2). See Non-Patent Document 15).

Next, a propagation model when the radio wave exceeds the roof will be described.

Generally, the millimeter wave band has strong straightness. Therefore, once the dominant incoming wave is shielded by the building existing between BS and MS, it is expected that the received signal level will drop significantly. This is because radio waves in the millimeter wave band have a large transmission loss of the building and a large diffraction loss at the vertical edge of the building (see Non-Patent Documents 18 and 19).

From these facts, three-dimensional spatially such as shooting and bouncing rays (SBR) (see Non-Patent Document 20) and vertical plane launching (VPL) (see Non-Patent Document 21), which are deterministic propagation estimation methods. Rather than emitting rays and considering all rays equally, it may be possible to detect spectrum vacancy only by modeling the dominant incoming wave.

Walfisch et al. Calculated the propagation loss due to multiple buildings existing between BS and MS using Kirchhoff approximation (KA), keeping in mind that the dominant incoming wave in the urban environment is cross-roof propagation.

式（１）において、ｄは対象環境内の建物間隔（エッジ間隔）を表しており、ｋ及びλは入射波の波数及び波長を表している。式（１）に示した通り、（ｎ-１）番目の吸収壁上方に存在する散乱波は二次波源としてｎ番目の吸収壁上方における散乱波分布を決定するのに使用される。 As shown in FIG. 3, the urban environment is assumed to be uniform building height and spacing in this model. Buildings existing between BS and MS are considered as n consecutive absorption walls. Then, KA is sequentially used for each absorption wall to calculate the propagation loss. The scattered wave distribution Hn (y) at the point y existing on a certain absorption wall n is calculated by sequentially applying KA to each absorption wall as in the equation (1).

In the formula (1), d represents the building spacing (edge spacing) in the target environment, and k and λ represent the wave number and wavelength of the incident wave. As shown in the equation (1), the scattered wave existing above the (n-1) th absorption wall is used as a secondary wave source to determine the scattered wave distribution above the nth absorption wall.

Next, the minimum propagation loss estimation model developed from Kirchhoff approximation will be described.

In the model for the UHF band using KA proposed by Walfisch et al. (See Non-Patent Document 8), it is assumed that the plurality of buildings B existing in the area between BS and MS are uniform in height and spacing. It had been. However, in the millimeter wave band, radio waves are blocked by a single building and affect the propagation characteristics of radio waves.

Therefore, it is necessary to build a simulation environment after reflecting the actual environment. The inventors constructed a simulation environment in which the building height was estimated and the actual environment was reflected, using the building circumference data provided by the Geospatial Information Authority of Japan, topographical information, and map data acquired from Google Earth. The proposed method is an improved model using KA to estimate the minimum propagation loss.

y軸方向に積分を実行する際は窓関数を用いて積分を打ち切る。窓関数Ｗは、以下の式（３）により示される。 As shown in FIG. 4, according to the proposed method, a limited number of building edges existing between BS and MS are extracted. According to the proposed method, only the losses that occur at the extracted building edges are considered. In the proposed method, the urban environment and building edges used in the calculation are simplified. The proposed method avoids overestimating the propagation loss by calculating the diffraction loss due to diffraction at the upper ends of the two shields, rather than considering the losses due to all building edges. The diffraction loss is calculated based on the following window function W (see Non-Patent Document 4) and the equation (2) using KA. The scattered wave distribution at the point y on the building edge n is expressed as follows using the scattered wave distribution on the edge (n-1).

When performing the integration in the y-axis direction, the window function is used to terminate the integration. The window function W is expressed by the following equation (3).

According to the proposed method considering the diffraction loss by the above calculation, it is guaranteed that the loss is larger than that of the free space propagation model. According to the proposed method, the accuracy of extracting the free area of PUs is improved, and the transmission right can be appropriately granted by allocating the free area to SUs.

Next, the experimental results will be described.

As shown in FIG. 5, after setting one BS, the position of the MS was changed and the received radio wave was measured. The measurement was carried out around the Eda area in Aoba Ward, Yokohama City, Kanagawa Prefecture. The measurement area is a relatively sloping urban environment. In the area, in addition to general detached houses with a height of about 6 m, apartment houses and commercial facilities with a height of about 30 m coexist.

FIG. 6 shows the measurement specifications used in the experiment. An omnidirectional antenna was used for the transmission / reception antenna, and a continuous wave generated by the signal generator was used for the transmission signal. The BS was installed on the roof of a building 18m above the ground. The MS was installed on a pole with a height of 2 m provided on the cart. At the time of measurement, the cart on which the MS was placed was moved in sequence, and the received signal strength was recorded together with the latitude and longitude information using a spectrum analyzer.

Next, the measurement result will be described.

FIG. 7 shows the received signal strength based on the measurement result. The received signal strength is averaged every 5 m mesh. The received signal strength is attenuated in proportion to the distance between the BS and MS, and even when a building having a height of about 30 m exists between the BS and MS, the received signal strength is reduced to almost a noise level. Furthermore, even when the MS is located relatively close to the BS, the received signal level drops significantly when the propagation path is blocked by a plurality of buildings. As described above, the propagation characteristics of radio waves in the millimeter wave band are significantly affected by the shielding by buildings, and it is important to estimate the propagation loss in consideration of their position information.

Next, the comparison between the measurement result and the simulation result will be verified.

In order to verify the effectiveness of the proposed method, the frequency resource detection accuracy calculated by the proposed method and the existing method will be compared. The existing method, A Free Space Path Loss (FSPL) model, and the VPL method, which calculates the signal strength at each receiving point by emitting rays three-dimensionally, are used. The proposed method was performed in an environment built on Matlab, and the free space propagation model and VPL method were performed using Remcom's Wireless Institute (see Non-Patent Document 22). The accuracy of each model is verified by comparing the detection result predicted from each model with the measured data.

For example, if it is determined that both the estimated value calculated from a certain model and the measured value are equal to or less than the interference threshold value, True Positive (TP) is counted. Four patterns of True Positive (TP), True Negative (TN), Miss Detection (MD), and False Alarm (FA) are set for the comparison result between the estimated value calculated in the same manner and the measured value.

Of these, TP and TN mean that the models were successful in prediction, and MD indicates that each model overestimated the propagation loss. If it is determined to be MD, it means that it may interfere with PUs. When it is determined to be FA, it is determined to be the reverse pattern of MD, which means that SUs has lost the transmission opportunity.

FIG. 8 shows the detection result by the proposed model. In this evaluation, the interference tolerance threshold was set to -115 dBm. In the proposed method, the accuracy of spectrum detection is improved regardless of the distance from the BS. However, the proposed method also observes MD in the MS route extending radially from BS.

FIG. 9 shows the result of comparing the detection accuracy between the proposed method and the existing method. In the free space propagation model, which is a kind of the conventional statistical model, the FA is 38%, which is the lowest detection accuracy among the three models. This is because the free-space propagation loss model does not take into account phenomena such as shielding and reflection caused by buildings.

When the detection result of the proposed method and the detection result of VPL were compared, the ratio of successful prediction (TP + TN) of the proposed method was improved by about 7.5% as compared with VPL. This is a result of the proposed method considering only the limited building edges and preventing the propagation loss from being overestimated.

Next, error verification using ray tracing simulation will be described.

As described above, the proposed method has improved the detection accuracy by 7.5% as compared with the VPL method, which is one of the conventional ray tracing simulations. However, since the proposed method targets only cross-roof propagation, if the reflected waves are predominant at the receiving point, the result of Miss Detection may be obtained because their contributions are not taken into consideration.

Therefore, by referring to the delay and arrival angle characteristics of the predetermined route extracted from the routes used in the experiment, the influence of the reflected wave on the detection accuracy will be verified.

As shown in FIG. 10, Route 1 and Route 2 were selected as verification targets because there are a plurality of points having MD. Routes 1 and 2 are affected by reflected waves because the MS route extends radially from the BS and buildings with relatively high height and area are gathered along the route. Selected for verification.

Since a narrow band signal and an omnidirectional antenna were used in the measurement, the delay and arrival angle information at the time of actual measurement is unknown. The inventors constructed the same environment on the ray race simulator and confirmed the presence or absence of reflected waves by referring to the arrival angle and delay information at each MS point. In addition, in this simulation, up to 6 reflections and 2 diffractions were taken into consideration for verification.

Next, the error verification result will be described.

FIG. 11 shows the arrival angle (azimuth) and delay characteristics of each MS of Route 1. From the arrival angle characteristics, it can be seen that almost all the arrival waves arrive from around φ = 110,280 deg. These are presumed to be direct waves from the BS, over-roof waves, and reflected waves caused by a relatively tall building (building 2 in FIG. 13). Further confirming the delay characteristics, a wave arriving from the BS direction was observed with a delay of about 1.6 μsec with respect to LoS. It is presumed that this is a reflected wave from an apartment house (building 1 in FIG. 13) located behind the BS.

FIG. 12 shows an example of observing the reflected wave caused by a relatively large building in the area in addition to the wave arriving over the roof. Furthermore, if the rays are not significantly shielded in each section between BS and building and between building and MS, such as MS position # 7-21 on route 1 and MS position # 40-50 on route 2, this reflected wave The impact is significant. Since the conventional method using KA targets only the propagation over the roof, the reflected wave caused by the building existing behind and far from the MS is not considered. Therefore, it is presumed that the propagation loss is overestimated and the MD result is obtained as a result.

Next, it will be described that the influence of the reflected wave is added to the propagation loss estimation model.

As shown in FIG. 14, in order to estimate the propagation loss due to the influence of the reflected wave, the reflector R is set in addition to the first shield and the second shield in the propagation loss estimation model. When the propagation loss is estimated due to the influence of the reflected wave, the reception intensity is increased in the receiving unit and the propagation loss is reduced.

The reflector R is set in the receiving unit in the direction opposite to the propagation path D. _{The reflector R generates the reflection influence P reflection} of the backscattered wave in the receiving unit MS. The detection unit 4 extracts a reflector in the vicinity of the reception unit MS. The detection unit 4 calculates the intensity of the backscattered wave based on the physical optics approximation, and calculates the reflection effect. The detection unit 4 meshes the wall surface of the reflector R, and calculates the reflection effect P _{reflection of the power P i reflected by each mesh i on the receiving unit.} Detector 4 calculates the sum of the power P _i as a reflection effect P _reflection. In the absence of reflector R, the reflection effect is zero.

As described above, according to the radio wave detection device 1, the amount of calculation can be significantly reduced by limiting the number of obstacles in the radio wave propagation path to two and limiting the incoming wave arriving at the receiving unit to the line-of-sight wave. .. According to the radio wave detection device 1, by avoiding overestimation of the diffraction loss propagation loss, it is possible to reduce interference with other radio systems having different frequency bands when applied to the dynamic frequency sharing technology.

According to the radio wave detection device 1, it is guaranteed that the propagation loss is larger than that of the free space propagation model. According to the radio wave detection device 1, the accuracy of extracting an empty area of radio waves in a predetermined frequency band can be improved. According to the radio wave detection device 1, the reflector existing behind the receiver in the propagation path D is applied to the propagation loss estimation model to calculate the reflection effect on the receiver, thereby determining the reception intensity of the radio wave in the receiver. The accuracy of the estimated value can be improved.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof. For example, although the radio wave detection device is described as a simulation device, it may be applied to an existing base station and verified. The propagation loss estimation model exemplifies the extraction of two obstructions, but may be two or more.

1 Radio wave detection device 2 Acquisition unit 4 Detection unit 6 Calculation unit 8 Storage unit 10 Display unit 12 Communication unit B Building BS transmission unit D Propagation path edge1 1st shield edge2 2nd shield MS receiver NW network R Reflector S server

Claims (8)

An acquisition unit that acquires terrain data in the propagation path between a transmission unit that transmits radio waves and a reception unit that receives the radio waves at an arbitrarily set position.
Based on the topographical data acquired by the acquisition unit, a detection unit that detects at least one shield that shields the propagation path, and a detection unit.
A calculation unit for calculating the propagation loss of the radio wave in the propagation path based on the diffraction loss generated by diffraction in the shield is provided.
Radio wave detection device. The calculation unit calculates the propagation loss based on the free space propagation loss that is attenuated according to the distance in the propagation path and the diffraction loss generated by diffraction at the upper edge of the shield.
The radio wave detection device according to claim 1. In the propagation path, the detection unit first intersects the first shield from the transmission unit along the direction of the propagation path and the second shield that first intersects from the reception unit along the direction of the propagation path. Detects things and
The calculation unit calculates the diffraction loss based on the first diffraction loss generated in the first shield and the second diffraction loss generated in the second shield.
The radio wave detection device according to claim 1 or 2. The calculation unit calculates the received power value in the receiving unit based on the propagation loss, and if the received power value is less than the threshold value, determines that the radio wave band is free at the position of the receiving unit. If it is equal to or more than the threshold value, it is determined that the band of the radio wave is not available.
The radio wave detection device according to any one of claims 1 to 3. The calculation unit calculates the diffraction loss based on the Kirchhoff approximation.
The radio wave detection device according to any one of claims 1 to 4. The detection unit detects a reflector that reflects the radio wave in the direction opposite to the propagation path in the reception unit.
The calculation unit calculates the propagation loss of the radio wave in the propagation path based on the reflection effect generated by the reflected wave reflected from the reflector.
The radio wave detection device according to any one of claims 1 to 5. The computer
Acquires terrain data between a transmitting unit that transmits radio waves and a receiving unit that receives the radio waves at an arbitrarily set position.
Based on the terrain data, at least one shield that blocks the propagation path of the radio wave between the transmitting unit and the receiving unit is detected.
The propagation loss of the radio wave in the propagation path is calculated based on the diffraction loss generated by diffraction in the shield.
Radio wave detection method. On the computer
The terrain data between the transmitting unit that transmits radio waves and the receiving unit that receives the radio waves at an arbitrarily set position is acquired.
Based on the terrain data, at least one shield that blocks the propagation path of the radio wave between the transmitting unit and the receiving unit is detected.
The propagation loss of the radio wave in the propagation path is calculated based on the diffraction loss generated by diffraction in the shield.
program.

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