WO2015178340A1 - 受信状態表示方法および受信装置 - Google Patents
受信状態表示方法および受信装置 Download PDFInfo
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- WO2015178340A1 WO2015178340A1 PCT/JP2015/064172 JP2015064172W WO2015178340A1 WO 2015178340 A1 WO2015178340 A1 WO 2015178340A1 JP 2015064172 W JP2015064172 W JP 2015064172W WO 2015178340 A1 WO2015178340 A1 WO 2015178340A1
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- interference wave
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/20—Monitoring; Testing of receivers
- H04B17/23—Indication means, e.g. displays, alarms, audible means
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/10—Polarisation diversity; Directional diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/18—Network planning tools
Definitions
- the present invention relates to a reception state display method and a reception device.
- an FPU (Field Pickup Unit) device for transmitting video signals has been used as an information transmission system for transmitting information such as video signals for a marathon relay or a relay station relay.
- the transmission signal such as the video signal is transmitted from the relay vehicle equipped with the FPU to the base station installed at the top of the mountain, etc., using the radio wave modulated by the FPU device with the video signal captured by the camera.
- the broadcast video is broadcast live, video disturbances and freezes must be avoided as much as possible, and careful rehearsals are being made in advance. In the rehearsal, reception state information is recorded according to the position and moving direction of the relay vehicle, and the recorded information is used when making a transmission plan.
- Patent Document 1 a technique of a transmission state display method and apparatus capable of providing support for simplifying the operation work by recording information related to the operation of the information transmission system is disclosed (for example, see Patent Document 1.)
- An object of the present invention is to provide antenna direction adjustment information for directing a receiving antenna in an optimum direction from an interference wave and a delayed wave. It is another object of the present invention to analyze a combination of reception state information, antenna direction information, and interference wave information, and use it for transmission planning.
- the reception status display method of the present invention is a reception status display method in an information transmission system that wirelessly transmits information while a relay vehicle is moving and receives the transmitted information at a base station, and represents the position of the relay vehicle.
- Acquire at least one reception status information among position information, reception level related to received video signal, bit error rate, delay profile information, and at least one interference wave information among interference wave level and interference wave frequency.
- the reception assist information is generated from the reception state information and the interference wave information, the reception assist information is based on the current relay vehicle position information and the antenna direction information, and the reception assist information is based on the relay vehicle position information and the antenna direction information. It is characterized by being displayed on a display device as a two-dimensional map.
- the reception status display method of the present invention is the reception status display method described above, wherein the reception assist information map is scrolled along the relay vehicle position axis along with the progress of the relay vehicle on the basis of the current relay vehicle position.
- the reception assist information map is scrolled along the reception antenna direction axis based on the current direction of the reception antenna.
- the receiving device of the information transmission system of the present invention is an information transmission system in which a relay vehicle that wirelessly transmits information while moving and a base station that is a receiving device perform wireless communication, and the receiving device includes a receiving unit, An antenna, an electronic compass, a recording device, and a display device.
- the receiving device includes at least one of position information indicating the position of the relay vehicle, reception level related to the received video signal, bit error rate, and delay profile information.
- At least one interference wave information is acquired from the reception state information, interference wave level, and interference wave frequency
- reception assist information is generated from the reception state information and interference wave information
- the display device relays the reception assist information to the current relay.
- the reception assist information is displayed as a two-dimensional map with the relay vehicle position information and the antenna direction information as axes. It is characterized in.
- the present invention it is possible to provide antenna direction adjustment information for directing the receiving antenna in the optimum direction from the interference wave and the delayed wave.
- FIG. 1 is a layout diagram of an information transmission system according to an embodiment of the present invention.
- the schematic diagram which shows the structure of the information transmission system of this example.
- FIG. The figure for demonstrating the receiving state displayed on the display apparatus of the base station 3.
- FIG. The figure for demonstrating the reception state of each base station displayed on the display apparatus of the base station 3.
- FIG. The figure for demonstrating the delay profile information which concerns on one Example.
- FIG. 1 is a configuration diagram of an information transmission system according to an embodiment of the present invention.
- a relay car 2 runs along the marathon course 1.
- Base stations 3, 4 and 5 are installed along the marathon course 1 on the top of a mountain or on the roof of a building.
- FPU receivers 214-1 to 214-3 provided in each base station are reception antennas having strong directivities. Then, the radio signal from the relay vehicle 2 is received.
- the direction ⁇ of the receiving antenna can be freely changed.
- the direction ⁇ represents, for example, a horizontal angle (clockwise) with respect to the north. In this example, only the horizontal direction ⁇ is movable as the antenna direction, but it is easy to add a vertical direction.
- a base station located at the closest distance from the relay vehicle 2 or a base station that can see the relay vehicle 2 is responsible for reception, and the base station rotates the antenna direction ⁇ as the relay vehicle 2 moves, Point the receiving antenna in direction 2.
- the configurations of the base stations 3, 4 and 5 are basically the same.
- the video received by the base station 3 is finally transmitted to the head office of the television station by means such as FPU multistage relay, satellite link, optical fiber line or the like.
- the receiving antenna is directed toward the interference wave source 6, the interference wave is largely mixed and a code error or loss of synchronization may occur. As a result, the video may be disturbed and freeze. For this reason, rehearsal is performed before relaying a marathon or the like, and reception state information and interference wave information I ( ⁇ , f) are collected based on the antenna direction information ⁇ as information acquired during the rehearsal.
- f is an interference wave frequency. The frequency at which the interference wave is observed often varies depending on the location of the base station, and the interference wave information I is a function in a two-dimensional space of the antenna direction information ⁇ and the frequency f.
- ⁇ ⁇ Select a frequency that is not easily affected by interference waves by assigning channel frequencies during actual operation based on the information collected during the rehearsal. Further, reception assist information indicating the optimum antenna direction is displayed to the antenna direction operator.
- the channel frequency allocation is to determine a frequency to be used for relaying within a frequency range (for example, 1.2 / 2.3 GHz band) that can be used for a license in a production operation.
- rehearsal that collects various information and rehearsal exercises at the same time, analysis of acquired information, and production operation.
- the reception state information based on the position information l indicating the distance from the starting point of the relay car 2 on the marathon course 1 and the antenna direction information ⁇ of the receiving antenna, and the interference wave information based on the antenna direction information ⁇ .
- the purpose is to obtain I ( ⁇ , f).
- FIG. 2 is a schematic diagram showing the configuration of the information transmission system of this example.
- a distance meter 202 is mounted on the relay vehicle 2, and the acquired travel distance is output to the FPU transmission unit 204 as position information l.
- the travel distance is a kind of the position information l because the position can be known by matching the distance with the kilometer of the road.
- road information a numerical map (digital road map) can be used.
- the video signal obtained by the camera 203 mounted on the relay vehicle 2 is also output to the FPU transmission unit 204.
- the FPU transmitter 204 multiplexes the input video signal and position information l, performs modulation processing (OFDM, etc.), and outputs the modulated signal to the transmission antenna 205.
- the transmitting antenna 205 radiates the input signal to space.
- an omnidirectional antenna is often used in the horizontal direction.
- the base station 3 receives the signal 220 transmitted from the transmission antenna 205 of the relay vehicle 2 by the reception antenna 208 installed in the antenna directivity automatic rotation means 207, and outputs the RF signal 221 to the FPU reception unit 210.
- the antenna directivity automatic rotating means 207 has a function of rotating the directivity of the receiving antenna 208 in the horizontal direction.
- the system includes a mechanical system and an electronic system using an array antenna. Here, a mechanical system is used.
- the receiving antenna 208 does not need to be rotated in an obviously unnecessary direction, and may be scanned so as to reciprocate based on the direction in which the relay vehicle 2 exists (Line of Sight direction) in order to obtain high throughput. .
- the existing direction is determined based on the reception level or the position information l by a well-known tracking antenna technique.
- the reception antenna 208 is provided with an electronic compass 209, which can acquire the direction information ⁇ of the reception antenna 208 and outputs the acquired antenna direction information ⁇ to the storage device 211.
- the FPU / receiver 210 receives reception state information such as reception level S ( ⁇ , l), bit error rate B ( ⁇ , l), delay profile information D ( ⁇ , l, ⁇ ), and interference wave information I ( ⁇ , f) and position information 1 of the relay vehicle 2 is output to the storage device 211.
- reception state information such as reception level S ( ⁇ , l), bit error rate B ( ⁇ , l), delay profile information D ( ⁇ , l, ⁇ ), and interference wave information I ( ⁇ , f) and position information 1 of the relay vehicle 2 is output to the storage device 211.
- ⁇ indicates the delay time of the delayed wave, and detailed description of the delay profile information D ( ⁇ , l, ⁇ ) will be described later.
- the storage device 211 stores information input from the FPU receiving unit 210.
- the reception level S ( ⁇ , l) and the delay profile information D ( ⁇ , l, ⁇ ) are information relating to the transmission signal, they are functions of the relay vehicle position l and also depend on the antenna direction ⁇ . It is also a function.
- the interference wave information I ( ⁇ , f) is acquired by the above-described system configuration at the time of the rehearsal, if the frequency f of the interference wave exists in the band of the desired wave or in the vicinity thereof, the interference In some cases, the wave is buried in the desired wave and the detection accuracy is lowered, so that accurate interference wave information I ( ⁇ , f) cannot be acquired. Further, since the interference wave does not always exist, it is desirable to separately acquire only the interference wave information I ( ⁇ , f). The configuration at that time will be described below.
- the radio signal from the relay vehicle 2 is not transmitted, the interference direction ⁇ of the receiving antenna 208 installed in the base station 6 is moved, and the interference acquired by the FPU receiving unit 210 is obtained.
- the wave information I ( ⁇ , f) and the antenna direction information ⁇ acquired by the electronic compass 209 are output to the external storage device 211, and the storage device 211 receives the interference wave information I ( ⁇ , f, based on the input antenna direction information ⁇ . Save f).
- the FPU receiving unit 210 is equipped with a frequency analysis function capable of observing the characteristics of all frequencies that can be used under the license, so that the interference wave information I ( ⁇ , f) can be obtained at all usable frequencies. Can be collected.
- FIG. 3 is an internal block diagram of the FPU receiving unit 210.
- the FPU receiving unit 210 of this example is characterized by having a frequency analysis function (spectrum analyzer).
- the AGC amplifier 301 amplifies the reception signal input from the reception antenna 208 to an appropriate level.
- the received signal includes an OFDM modulated radio frequency signal.
- Logarithmic detector 302 detects the level of the signal amplified by AGC amplifier 301.
- the logarithmic detector 302 is not essential.
- the non-linear filter 303 is a loop filter constituting the AGC, and determines a gain to be set in the AGC amplifier 301 based on an output of a C / N optimization gain calculator 317 described later. In this example, in order to cope with a sudden interference wave, a non-linear characteristic filter that restricts the gain to a small value when the level of the logarithmic detector 302 is abnormally high (abrupt increase) is used.
- the frequency converter 304 converts a radio frequency reception signal into an intermediate frequency or baseband by mixing a predetermined local signal with the reception signal.
- the ADC 305 converts the frequency-converted signal into a digital signal. It should be noted that a complex signal composed of in-phase and quadrature components must be input when input to the subsequent FFT unit 306, and analog or digital quadrature detection is performed before or after the ADC 305.
- An FFT (Fast Fourier Transform) unit 306 converts the input signal into a frequency domain signal and outputs the signal to the equalizer 307.
- the equalizer 307 estimates the propagation path characteristic by referring to the pilot signal, corrects the amplitude and phase of the input signal, and outputs the corrected signal to the determiner 308.
- the determiner 308 makes a hard decision on the input signal (symbol), and outputs a set of the determination result and error correction likelihood to the erasure processing unit 309. The likelihood is calculated for each symbol from the magnitude of the difference between the input signal and the determination result (EVM: Error Vector Magnitude) or the like.
- the erasure processing unit 309 changes the error correction likelihood of the frequency at which interference has occurred based on the signal input from the interfered wave frequency determination unit 314, which will be described later, and outputs the error correction likelihood to the FEC unit 124. To do. For example, when the amplitude of the interference wave is large, the error correction likelihood of the signal affected by the interference wave is lowered by setting the error correction likelihood to a small value (for example, 0).
- the FEC unit 310 performs deinterleaving processing on the input signal, and performs error correction based on the error correction likelihood on the determination result.
- the BER measuring device 311 measures a bit error rate by counting correction errors in the FEC unit 310, for example.
- the preprocessing unit 312 performs processing such as rate conversion and windowing in order to effectively perform frequency analysis according to the purpose within a predetermined calculation amount range. Can convert to multiple rates.
- the FFT unit 313 is an FFT for performing frequency analysis. In this example, the FFT size is 8192, the frequency resolution is about 100 kHz in the 70 MHz band, the dynamic range is 60 dB or more, and about 33 ms, which is slower than the FFT unit 306. A spectrum is obtained at an update period of. The 70 MHz band is useful for knowing the usage status of adjacent (adjacent) channels.
- the spectrum automatic analysis unit 314 processes the spectrum input from the FFT unit 313 by performing power conversion, time smoothing, etc., and specifies the position of the desired wave from the shape of the spectrum, etc. ) Identify the frequency and power of the interference wave.
- the interfered frequency determination unit 315 detects and outputs all positions where harmful interference waves exist within the desired wave band.
- the signal / noise measuring device 316 is based on the spectrum input from the FFT unit 313 and the gain of the AGC amplifier 301, and a desired signal power and an undesired signal (noise and external interference) appearing at the output of the FFT 306 other than the desired signal. The total power of is calculated.
- the undesired signal can be obtained as the sum of the power of the narrowband interference wave in the band and the power of the guard band existing on both sides of the desired signal (data subcarrier).
- the C / N optimization gain correction unit 317 calculates the total power (including the desired wave and adjacent and adjacent neighbors) with a weight that becomes smaller as the distance from the frequency of the desired wave increases, and keeps it constant.
- a correct AGC gain is calculated and output to the non-linear filter 303.
- the delay profile calculation unit 320 calculates a delay profile obtained by performing IFFT on the propagation path characteristics obtained by the equalizer 307. Note that information such as the received power S and the delay profile D as obtained in the configuration of FIG. 3 is not associated with ⁇ .
- the recording device 211 needs to acquire ⁇ from the electronic compass at the same time and record it in association with it.
- FIG. 4 is a spectrum diagram showing the relationship between the FPU usage frequency and the interference wave frequency in this example.
- F1, F2, and F3 there are usable frequencies F1, F2, and F3, but it is assumed that an interference wave having a frequency f exists in the band of F1 at least near the base station 3.
- FIG. 5 is a schematic diagram for explaining a mode of reception by the base station 3, and shows details of the periphery of the base station 3 in FIG. It is assumed that reception state information regarding at least the frequency (referred to as F1) used for the rehearsal is obtained in the range of about ⁇ 90 ° ⁇ ⁇ 90 ° by the rehearsal in the mode of FIG.
- F1 reception state information regarding at least the frequency
- FIG. 6 is a diagram for explaining the display of the reception state obtained in the manner of FIG.
- S ( ⁇ , l) / [N + I ( ⁇ , f)] indicating the quality of the received signal is displayed on the display device 214 in two directions with the antenna direction ⁇ and the relay vehicle position l as axes. Displayed on a dimension.
- the display of FIG. 6 is called a reception assist information map.
- N is a noise level depending on the internal noise of the receiver, and is set in advance as a constant without depending on the antenna direction ⁇ , the relay vehicle position l, and the frequency f.
- S / (N + I) is shown in a color such that the higher the scalar quantity S / (N + I), the warmer or brighter the color, and the lower the color becomes darker or darker, and the intensity of the interference wave.
- a region 602 where is a certain value or more, a different color or fill pattern is used. Since the region 602 depends only on the direction of the interference source, it is simply drawn as a rectangle.
- the reception state information that is the source of S / (N + I) is not necessarily acquired uniformly in all the two-dimensional regions, and can be appropriately interpolated by interpolation.
- S / (N + I) of the portion that cannot be interpolated is displayed in another color or pattern (for example, dark) as no data.
- a reception assist information map is created from reception quality that takes into account both the desired wave from the signal source (transmission point) and the external interference wave from a different location (direction). By doing so, S ( ⁇ , l) / [N + I ( ⁇ , f)] for each antenna direction can be clearly expressed.
- FIG. 7 is a reception assist information map showing the reception state of each base station 3 in this example.
- the reception assist information map can be created for each base station and each frequency. It is ideal to obtain the reception state information of each frequency by repeating the course 1 movement for the number of frequencies, but for simplicity, I ( ⁇ , f) is collectively set for all frequencies. It is also possible to obtain S / (N + I) by obtaining and applying the reception level S ( ⁇ , l) at one frequency to other frequencies.
- the antenna direction ⁇ is always directed to the relay vehicle 2 from the 0 km point to the 30 km point without being affected by the deterioration due to the interference wave. It can be seen that a good reception state can be maintained.
- the area 701 surrounded by a dotted line in FIG. 7 corresponds to a deteriorated area caused by a delayed wave although it cannot be directly understood from the reception assist information map.
- the deterioration due to the delayed wave is usually determined by the delay profile at that time.
- FIG. 8 is a diagram for explaining the display of the delay profile information of this example.
- the delay profile information D ( ⁇ , l, ⁇ ) in this example is expressed by three axes of a reception level, a delay time ⁇ , and an antenna direction ⁇ at a given relay vehicle position l. From the delay profile information D, it is possible to search for the antenna direction ⁇ such that the delay wave exceeding the guard interval time is smaller and smaller, but it is difficult to read it instantaneously. For this reason, in this example, the reception assist information map is displayed in consideration of deterioration due to delay. In order to express it on the reception assist information map, it is necessary to delete the variable of the delay time ⁇ .
- N D ( ⁇ , l) F [D ( ⁇ , l, ⁇ )]. be able to.
- the function F adds up the power with a weight proportional to the excess time for a path having a delay time ⁇ exceeding the guard interval time. The proportionality is when the excess time is less than or equal to the effective symbol length.
- the equivalent noise amount N D ( ⁇ , l) is added to the reception assist information map. Specifically, color-coded display is performed using S / (N + N D + I).
- reception status information [reception level S ( ⁇ , l), delay profile information D ( ⁇ , l, ⁇ )] acquired through rehearsal and interference wave information I ( ⁇ ,
- a reception assist information map is created using f), and channel frequencies are allocated during actual operation.
- the bit error rate B ( ⁇ , l) is displayed as appropriate in order to confirm the final signal quality because the response to changes in the transmission environment ( ⁇ and l) is slow.
- the created reception assist information map is stored in the storage device 211 of each base station 3 and used during actual operation.
- the configuration of the system at the time of production is as shown in FIG.
- the automatic rotation function of the antenna directivity automatic rotating means 207 is not necessary, and it is used as a simple antenna rotating table (tripod with a pan head).
- an antenna that is not equipped with an automatic rotation function or is disabled is referred to as an antenna turntable 218.
- the operator keeps the reception antenna 208 mounted on the antenna turntable 213 in the direction in which the quality of the reception signal is the best.
- the FPU receiving unit 210 receives a signal from the receiving antenna 208 and outputs at least a video signal and a relay vehicle position l now .
- the video signal is separately connected to a transmission path to the head office.
- the current position information l now of the relay vehicle 2 input from the FPU receiving unit 210, the antenna direction information ⁇ now input from the electronic compass 209, and the FPU usage frequency assigned in advance are rehearsed in advance.
- a reception assist information map that is an analysis result of the acquired information is read out and displayed on the display device 214.
- the display device 214 displays the read reception assist information map to the operator in a manner necessary and easy to understand for the operation in the antenna direction.
- FIG. 9 is a reception assist information map displayed on the display device 214 during actual operation.
- the reception assistant information map created by analyzing the information obtained in rehearsal, in a display area 901 of the display device 214, the relative antenna direction theta O horizontally, vertically relative relay vehicle position l 0 Displayed after conversion processing.
- the current antenna direction is always displayed at the center of the display device 214 to make it easier for the antenna direction operator to visually recognize the direction to move.
- the display be performed with a sufficiently short update frequency so as to follow the antenna direction information ⁇ in real time and scroll left and right.
- the current relay station position is enclosed in a frame so that it can be easily understood.
- the reception assist information map is scrolled down 902 as the relay vehicle moves, and the past reception state and the future reception state are displayed in an easy-to-understand manner.
- the part which displays a future reception state rather than the past is taken widely.
- the relay vehicle positions l 1 and l 0 are multiplexed with the video signal to be transmitted and transmitted from one radio.
- the communication means for transmitting the relay vehicle position and the like For example, ARIB STD-B54 broadcasting radio for broadcasting business can be used.
- the reception state display method and the receiving apparatus assist the antenna direction operator so that the antenna can be directed in the optimum antenna direction. As a result, it is possible to prevent the direction of the antenna in operation from being directed in the wrong direction, to ensure better S / (I + N), and to perform stable video transmission.
- the reception state display method and apparatus can provide antenna direction adjustment information in order to direct the reception antenna in the optimum direction from the interference wave and the delayed wave.
- the antenna direction adjustment information is not limited to manually operating the antenna direction, but can be used for the purpose of verifying the validity of the control direction in advance in automatic direction control.
- the present invention can be used in various wireless systems that receive signals from moving objects such as vehicles and railways using directional antennas, and in particular, in communication systems that share frequencies with other systems or are expected to be disturbed. Is preferred.
- the mobile body is not necessarily limited to the one that moves along the predetermined route, and the present invention can be applied if a large number of mobile bodies can be expected to follow a predetermined route. is there. Therefore, it can be widely applied to remote control, remote sensing, mobile communication (Massive MIMO), etc.
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Abstract
Description
中継映像は生放送されるため映像の乱れやフリーズは極力避けなければならず、事前に入念なリハーサルが行われている。リハーサルでは中継車の位置や移動方向によって受信状態情報を記録しておき、その記録した情報は伝送計画をたてる際に用いられている。
本発明は、干渉波と遅延波から最適な方向へ受信アンテナを向けるためのアンテナ方向調整情報を提供することを目的とする。また、受信状態情報とアンテナ方向情報と干渉波情報を組み合わせて解析を行い、伝送計画に役立てることを目的とする。
図1は本発明の一実施例に係る情報伝送システムの構成図である。
マラソンコース1に沿って中継車2が走行する。
方向θは、例えば、北を基準とした場合の水平方向の角度(右回り)を表す。本例ではアンテナ方向として水平方向θのみ可動させるものとするが、垂直方向を追加することも容易である。
基地局3,4,5の構成は基本的に同じであり、以後基地局3に代表させて説明する。基地局3で受信した映像は、FPUの多段中継、衛星リンク、光ファイバー回線等の手段により、最終的にテレビ局の本社に伝送される。
そのため、マラソン等の中継をする前にリハーサルを行い、リハーサル時に取得する情報として、アンテナ方向情報θにもとづき、受信状態情報と、干渉波情報I(θ,f)を収集する。ここで、fは干渉波周波数である。干渉波の観測される周波数は基地局の場所により異なる場合が多く、干渉波情報Iはアンテナ方向情報θと周波数fの2次元空間上の関数となる。
リハーサルではマラソンコース1上の中継車2のスタート地点からの行程距離(道のり)を表す位置情報lと受信アンテナのアンテナ方向情報θに基づいた受信状態情報とアンテナ方向情報θに基づいた干渉波情報I(θ,f)を取得することを目的とする。
図2は本例の情報伝送システムの構成を示す模式図である。
図2において、中継車2には距離計202が搭載されており、取得される走行距離は位置情報lとしてFPU送信部204へ出力される。なお走行距離は、道路のキロ程と突き合わせれば位置を知ることができので、位置情報lの一種とする。道路の情報としては、数値地図(デジタル道路地図)などが利用できる。
また、中継車2に搭載されたカメラ203にて得られた映像信号も、同じくFPU送信部204へ出力される。
送信アンテナ205は入力された信号を空間へ放射する。送信アンテナ205としては、水平方向に無指向のアンテナを用いることが多い。
アンテナ指向性自動回転手段207は、受信アンテナ208の指向性を水平方向に回転する機能を持つ。その方式として機械式やアレイアンテナを用いた電子式などがあり、ここでは機械式とする。受信アンテナ208は、明らかに必要のない方向へ回転させる必要はなく、高いスループットを得るために、中継車2が存在する方向(Line of Sight方向)を基準に往復するように走査させてもよい。存在する方向は、周知の追尾アンテナ技術により受信レベル或いは位置情報lに基づいて判別される。
受信アンテナ208には電子コンパス209が備え付けられており、受信アンテナ208の方向情報θを取得することができ、取得したアンテナ方向情報θを記憶装置211へ出力する。
ここで、受信レベルS(θ,l)と遅延プロファイル情報D(θ、l、τ)は送信信号に関する情報であるため、中継車位置lの関数となり、アンテナ方向θにも依存するためθの関数でもある。
AGCアンプ301は、受信アンテナ208から入力された受信信号を、適切なレベルに増幅する。受信信号はOFDM変調された無線周波信号を含む。
対数検波器302は、AGCアンプ301で増幅後の信号のレベルを検出する。対数検波器302は必須ではない。
非線形フィルタ303は、AGCを構成するループフィルタであり、後述のC/N最適化ゲイン算出器317の出力に基づいて、AGCアンプ301に設定する利得を決定する。本例では、突然の干渉波に対応するため、対数検波器302のレベルが異常に高い(急増した)ときにゲインを小さく制限するような、非線形特性のフィルタを用いている。
ADC305は、周波数変換をされた信号を、デジタル信号に変換する。なお、後続のFFT部306に入力される時には同相及び直交成分からなる複素信号になっている必要があり、ADC305の前又は後でアナログ又はデジタル直交検波が行われるものとする。
等化器307は、パイロット信号を参照するなどして伝搬路特性を推定し、入力された信号の振幅と位相を補正して判定器308に出力する。
判定器308は、入力された信号(シンボル)を硬判定し、その判定結果と誤り訂正尤度の組を消失処理部309へ出力する。尤度は、シンボル毎に、入力信号と判定結果との差の大きさ(EVM:Error Vector Magnitude)等から算出される。
FEC部310は、入力された信号にデインターリーブ処理を行い、判定結果に対して誤り訂正尤度に基づいた誤り訂正を行う。
BER測定器311は、FEC部310での訂正エラーを計数するなどして、ビットエラーレートを計測する。
前処理部312は、所定の計算量の範囲で、目的に応じて効果的に周波数解析を行うための、レート変換やウィンドイング等の処理を行う。複数のレートに変換可能である。
FFT部313は、周波数解析を行うためのFFTであり、本例ではFFTサイズを8192とし、70MHzの帯域で100kHz程度の周波数分解能、60dB以上のダイナミックレンジを有し、FFT部306より遅い33ms程度の更新周期でスペクトルを得る。70MHzの帯域は、隣隣接(隣接の隣接)チャネルの使用状況を知るうえで役立つ。
被干渉周波数判定部315は、所望波の帯域内で有害な干渉波が存在している位置を全て検出して出力する。
信号・ノイズ測定器316は、FFT部313から入力されたスペクトルとAGCアンプ301のゲインを基に、所望波の電力や、所望信号以外でFFT306の出力に現われる非所望信号(ノイズや外部干渉)の全電力を算出する。非所望信号は、帯域中の狭帯域干渉波の電力や、所望信号(データサブキャリア)の両側に存在するガードバンドの電力の総和として得ることができる。
遅延プロファイル算出部320は、等化器307で得られた伝搬路特性をIFFTするなどして得た遅延プロファイルを算出する。
なお、図3の構成で得られたままの受信電力Sや遅延プロファイルD等の情報は、θとは関連付けられていない。記録装置211は、タイミングを合わせて電子コンパスからθを取得し、対応付けて記録する必要がある。
運用計画立案時にはリハーサルで取得した受信状態情報[受信レベルS(θ,l)、ビット・エラー・レートB(θ、l)、遅延プロファイル情報D(θ、l、τ)]、干渉波情報I(θ,f)を解析して、チャンネル周波数の割り当てを決定する。
図4は本例のFPU使用周波数と干渉波周波数の関係を示すスペクトル図である。
本例の情報伝送システムでは、F1、F2、F3の使用可能周波数があるが、少なくとも基地局3付近において周波数fの干渉波が、F1の帯域内に存在しているものとする。
図5は、基地局3による受信の様態を説明する模式図であり、図1における基地局3の周囲を詳細を示している。図5の様態のリハーサルにより、-90°<θ<90°程度の範囲で、少なくともリハーサルに用いた周波数(F1とする)に関する受信状態情報が得られているとする。
図6に示すように、表示装置214には、受信信号の品質を示すS(θ,l)/[N+I(θ,f)]が、アンテナ方向θと中継車位置lを各軸とした二次元上に表示される。本例では図6の表示を受信アシスト情報マップと呼ぶ。ここでNは受信機の内部雑音に依存する雑音レベルであり、アンテナ方向θや、中継車位置l、周波数fに依存せず、定数として予め設定される。
受信アシスト情報マップでは、スカラー量であるS/(N+I)が高いほど暖色又は明るい色で、低いほど寒色又は暗い色となるような色でS/(N+I)が示され、更に干渉波の強度が一定以上となる領域602では、別の色或いは塗りつぶしパターンが用いられる。領域602は干渉源の方向にのみ依存するため、単純に矩形として描画される。S/(N+I)の元となる受信状態情報は、必ずしも二次元上の全ての領域で一様に取得されているとは限らず、適宜内挿により補間され得る。補間できない部分のS/(N+I)は、データなしとして他の色或いはパターン(例えば暗黒)に表示される。
このように指向性アンテナによる受信において、信号源(送信点)からの所望波と、それとは異なる場所(方向)からの外来干渉波との双方が加味された受信品質から受信アシスト情報マップを作成することで、アンテナ方向ごとのS(θ,l)/[N+I(θ,f)]を明確に表現できる。
図7に示す通り、受信アシスト情報マップは基地局別、周波数別に作成することができる。周波数の数の分、コース1の移動を繰り返して各周波数の受信状態情報を取得しておくことが理想であるが、簡易的には、I(θ,f)を全周波数に対して一括に取得し、ある1つの周波数における受信レベルS(θ,l)を他の周波数にもあてはめてS/(N+I)を得ることもできる。
また、F1周波数帯を使わざる負えない場合は、中継車位置l=1~7km及び13~30kmの範囲においてアンテナ方向θに注意すれば使用可能であることがわかる。
本例の遅延プロファイル情報D(θ、l、τ)は、与えられた中継車位置lにおいて、受信レベル、遅延時間τ、アンテナ方向θの三つの軸で表現される。遅延プロファイル情報Dから、ガードインターバル時間を超える遅延波がより小さく、少なくなるようなアンテナ方向θを探すことは可能であるが、瞬時に読み取ることは困難である。
そのため本例では、受信アシスト情報マップで、遅延による劣化を加味した表示を行う。受信アシスト情報マップ上で、表現するためには遅延時間τの変数を削除する必要がある。時間τを削除する関数をFとした場合、遅延波による等価雑音量をND(θ、l)とすると、ND(θ、l)=F[D(θ、l、τ)]と表すことができる。関数Fは、ガードインターバル時間を超える遅延時間τのパスについて、超過時間に比例する重みで電力を合算する。なお比例するのは超過時間が有効シンボル長以下の時で、それを超えると一定となる。この等価雑音量ND(θ、l)を上記受信アシスト情報マップに加味する。具体的にはS/(N+ND+I)を用いて色分け表示する。
本番時のシステムの構成は、図2に示した通りである。ただし、本番では、操作者が手動で受信アンテナ208の方向を調整するので、アンテナ指向性自動回転手段207の自動回転機能は不要であり、単なるアンテナ回転台(雲台付き三脚)として用いる。以下、自動回転機能を備えないあるいは無能化されたそれを、アンテナ回転台218と呼ぶ。
基地局3では、中継車2の移動にあわせて、操作者が、アンテナ回転台213に搭載された受信アンテナ208を、受信信号の品質が最も良くなる方向に向け続ける。
リハーサルにて得られた情報を解析して作成した受信アシスト情報マップを、表示装置214の表示領域901の中で、水平方向に相対アンテナ方向θO、垂直方向に相対的中継車位置l0を表すよう変換処理を行って表示する。
相対的中継車位置lOは現在の中継車位置を基準とした相対的な中継車位置であり、リハーサル時に取得した中継車位置情報lと現在の中継車位置lnowの差(lO=l-lnow)で表わされる。
また、現在の中継車位置が分かりやすいように枠で囲う。さらに、垂直方向を相対的中継車位置l0にすることで、中継車の移動とともに受信アシスト情報マップを下へスクロール902し、過去の受信状態と未来の受信状態が分かりやすく表示される。なお過去よりも未来の受信状態を表示する部分を広くとってある。
202:距離計、 203:カメラ、 204:FPU送信機、 205:送信アンテナ、
207:アンテナ指向性自動回転手段、 208:受信アンテナ、 209:電子コンパス、 210:FPU受信機、 211:記憶装置、 213:アンテナ回転台、 214:表示装置、 901:表示領域。
Claims (6)
- 中継車が移動しながら被変調信号を無線送信し、該送信された被変調信号を基地局が指向性アンテナで受信する情報伝送システムにおける受信状態表示方法であって、
前記被変調信号に含まれる中継車の位置を表す位置情報と、受信された前記被変調信号に関わる受信レベル、ビット・エラー・レート、遅延プロファイル情報のうち少なくとも一つの受信状態情報と、干渉波レベル、干渉波周波数のうち少なくとも一つの干渉波情報を取得し、前記受信状態情報と前記干渉波情報から受信アシスト情報を生成し、現在の中継車位置情報とアンテナ方向情報に基づいて、該受信アシスト情報を、前記中継車位置情報とアンテナ方向情報を軸とする二次元マップとして表示装置に表示することを特徴とする受信状態表示方法。 - 前記受信状態情報と前記干渉波情報は、アンテナ方向を変えながら事前に取得し、前記受信状態情報は、前記中継車の方向を含む範囲で前記アンテナ方向を走査しながら、前記位置情報と前記アンテナ方向情報の2変数関数として取得するものであり、
前記受信アシスト情報マップは、中継車の進行とともに現在の中継車位置を基準に、中継車位置情報の軸に沿ってスクロールし、現在の受信アンテナの方向を基準に、前記受信アンテナ方向情報の軸に沿ってスクロールして前記表示装置に表示されることを特徴とする請求項1に記載の受信状態表示方法。 - 前記位置情報は、前記中継車が移動する道路の行程距離であり、
前記受信アシスト情報は、受信信号の品質を示すスカラー量であることを特徴とする請求項2に記載の受信状態表示方法。 - 前記干渉波情報は、前記情報伝送システムが利用することができる複数の周波数において、事前に取得され、 前記表示装置は、当該取得した干渉波情報に基づいて選択した1つの運用周波数について、前記受信アシスト情報マップを表示することを特徴とする請求項2に記載の受信状態表示方法。
- 前記スカラー量は、受信された前記被変調信号の信号対干渉雑音比であって、OFDM方式である前記被変調信号におけるガードインターバル時間を超える遅延波が、雑音に等価なものとして包含されていることを特徴とする請求項3に記載の受信状態表示方法。
- 移動体が予定されたルートを移動しながら無線送信した被変調信号を、複数の基地局で受信する情報伝送システムにおける受信装置であって、
前記受信装置は、無線受信部と、指向性アンテナと、電子コンパスと、記録装置と、表示装置とを有し、前記複数の基地局にそれぞれ設けられ、
前記被変調信号に含まれる前記移動体の位置を表す位置情報と、受信された前記被変調信号に関わる受信レベル、ビット・エラー・レート、遅延プロファイル情報のうち少なくとも一つの受信状態情報を、中継車の方向を含む範囲で前記アンテナ方向を走査しながら、前記位置情報と前記アンテナ方向情報の2変数関数として事前に取得するとともに、干渉波レベル、干渉波周波数のうち少なくとも一つの干渉波情報を、アンテナ方向を変えながら事前に取得して、該受信状態情報と該干渉波情報から受信アシスト情報を生成し、
前記表示装置は、現在の移動体位置情報とアンテナ方向情報に基づいて、前記受信アシスト情報を、前記移動体位置情報とアンテナ方向情報を軸とする二次元マップとして表示することを特徴とする受信装置。
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JP2020057848A (ja) * | 2018-09-28 | 2020-04-09 | Kddi株式会社 | 干渉調整装置、干渉調整方法及びプログラム |
JP6997059B2 (ja) | 2018-09-28 | 2022-01-17 | Kddi株式会社 | 干渉調整装置、干渉調整方法及びプログラム |
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