JP6974663B2 - Video reception system - Google Patents

Description

The present invention relates to a video receiving system that receives video from a camera mounted on a moving body.

There is a video receiving system that receives a video signal transmitted from a camera mounted on a mobile body and outputs it to a display device to display a real-time video. This type of system can be utilized, for example, when displaying an image of a camera (on-board camera) mounted on each motor boat on a monitor or the like in a boat racetrack.

Conventionally, the following patent documents are available as prior arts related to this type of system. That is, Patent Document 1 is a live relay device of a public stadium, and after receiving a video signal taken by a camera mounted on each motor boat with a plurality of receiving antennas and converting it into an intermediate frequency signal by a low noise converter. Disclosed is a technique for selecting an intermediate frequency signal having the highest received electric field level for each transmitted radio wave and outputting it to a display device. Patent Document 2 is a route diversity control device, which is currently in use with respect to all of a multi-path digital line composed of a transmitter mounted on a mobile relay vehicle and receivers arranged at a plurality of receiving bases. Disclosed is a technique for automatically switching to a receiver in a good receiving state before the TS (Transport Stream) signal obtained from the receiver is defective. Patent Document 3 is a distributed wireless communication base station system, in which a wireless device equipped with a plurality of antennas and a signal processing device are connected by an optical fiber cable, and a wireless signal is transmitted between them by an analog RoF method. To disclose.

However, when a transmitting antenna for transmitting a video signal is attached to a moving body moving at high speed such as a motor boat, it is difficult to attach the transmitting antenna to a high position in order to reduce air resistance. Therefore, there is a concern that the transmitting antenna will be behind a shield and the receiving electric field level will decrease. In addition, the hull of the motorboat tilts when it changes direction, but at that time, the directivity of the transmitting antenna attached to the hull also tilts, so there is a concern that the received electric field level will also decrease. In addition, if the frequency band used for wireless transmission of video signals overlaps with the frequency band used in other wireless systems such as wireless LAN (Local Area Network), there is a concern that the code error rate will increase due to interference. There is also. No consideration is given to such issues in the literature disclosing the prior art.

In the case of a wireless LAN, data retransmission can be requested when the code error rate becomes large due to interference from another system or the like. However, if the data is retransmitted, a delay time will occur and the real-time property will be impaired. In general, in a wireless LAN, an omnidirectional receiving antenna is adopted for the purpose of receiving reflected waves and transmitted waves. On the other hand, in an environment such as a boat race track that is outdoors and has a relatively long wireless transmission distance, the received electric field level of the reflected wave cannot be expected. Therefore, use a directional antenna having a certain gain as the receiving antenna. I have no choice but to do it. Therefore, the wireless LAN technique cannot be adopted.

Japanese Unexamined Patent Publication No. 7-327224 Japanese Unexamined Patent Publication No. 2002-84215 JP-A-2015-220524

From the above viewpoint, in the conventional video receiving system that receives the video of the camera mounted on the moving body, the transmission quality of the video signal may deteriorate and it may not be possible to display the video in real time. And identify whether the cause is the transmitter mounted on the mobile body, the receiver placed around the moving area to receive the radio waves from the transmitter, or another factor. It's difficult to do.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video receiving system capable of easily identifying a factor of deterioration in transmission quality of a video signal.

In order to solve the above problems and achieve the object thereof, the first aspect of the present invention is to receive a plurality of video signals modulated by different frequencies and wirelessly transmitted from a plurality of moving objects moving in a moving area. Equipped with a receiver. Further, the movement is provided corresponding to each of the above-mentioned plurality of receivers, the video signal received by the corresponding receivers is distributed and demodulated for each frequency, and further, the movement is superimposed on the video signal wirelessly transmitted from the moving body. A video output signal is generated and output from a plurality of first signal processing units that detect at least one of body position information and vibration information, and the video signal of the same frequency demodulated by each of the plurality of first signal processing units. A second signal processing unit is provided. Further, a storage unit is provided, and this storage unit is at least one of information relating to a receiver that has received a video signal that has contributed to the generation of a video output signal output from the second signal processing unit , and position information and vibration information. It is designed to store information.

In the second aspect, when the first signal processing unit demodulates a video signal distributed for each frequency, at least one of the received electric field level and the code error rate of the video signal is detected. Then, the storage unit further stores the information detected by the first signal processing unit.

In the third aspect, the control unit determines the communication state of a plurality of receivers based on the information related to the receivers stored in the storage unit.

In the fourth aspect, the receiver sets an E / O circuit that converts a video signal into an optical signal, a detection circuit that detects the power level of the received video signal, and a power level detected by the detection circuit. As a result of comparison between the comparison circuit to be compared with the level and the comparison circuit, when the power level is less than the set level, the video signal is passed through the E / O circuit, and when the power level is higher than the set level, the E / O of the video signal is passed. It includes a switch that cuts off the output to the circuit.

According to the first aspect, from the information stored in the storage unit, it is possible to grasp the receiver whose reception condition is poor and does not contribute to the generation of the video output signal, and by extension, the cause of the deterioration of the transmission quality of the video signal is the transmission side. It has the effect of easily identifying whether it is on the receiving side or on the receiving side. Further, according to the first aspect, it is possible to grasp the transmission status of the video signal from the information stored in the storage unit by adding at least one of the position information and the vibration information of the moving body, and by extension, the video signal. It has the effect of easily identifying whether the cause of the deterioration of transmission quality is on the transmitting side or the receiving side.

According to the second aspect, it is possible to grasp the transmission quality of the video signal from the information stored in the storage unit by adding at least one of the received electric field level and the code error rate of the video signal, and by extension, the video signal. It has the effect of easily identifying whether the cause of transmission quality deterioration is on the transmitting side or the receiving side.

According to the third aspect, there is an effect that the communication state of the receiver can be automatically determined from the information stored in the storage unit.

According to the fourth aspect, there is an effect that the reliability of the video signal received by the receiver can be further improved.

An overall configuration diagram of a video receiving system according to an embodiment. A block diagram showing a circuit configuration of a main part of a wireless unit. The block diagram which shows the main part circuit composition of the E / O conversion part in a receiver. The block diagram which shows the main part circuit composition of a signal processing part. A flow chart showing the entire main control procedure of the control unit. A flow chart showing a part of the main control procedure of the control unit. Schematic diagram showing the data structure of the channel setting table.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In each drawing and the following description, the same elements are designated by the same reference numerals.

(composition)
FIG. 1 is an overall configuration diagram of a video receiving system 1 according to an embodiment. This embodiment is applied to a system in which an image of a camera mounted on each motor boat (hereinafter, simply referred to as a boat) is displayed on a display device in the racecourse in real time.

In FIG. 1, the area A shows the competition area (competition water surface) of the boat race track. When the race is started, the boats B1, B2, B3, B4, B5, B6 of a plurality of boats (six boats in the figure) run at high speed in the area A along a predetermined course. That is, the competition area A is defined as a moving area of the moving boats B1, B2, B3, B4, B5, B6.

Each boat B1, B2, B3, B4, B5, B6 is equipped with cameras C1, C2, C3, C4, C5, C6 and wireless units D1, D2, D3, D4, D5, D6. .. The wireless units D1, D2, D3, D4, D5, D6 have a first antenna E1, E2, E3, E4, E5, E6 for transmitting video signals and a second antenna F1, F2, F3 for receiving control signals. , F4, F5, F6 are connected. The first antennas E1, E2, E3, E4, E5, E6 and the second antennas F1, F2, F3, F4, F5, F6 are, for example, horizontal plane directional antennas, and each boat B1, B2, B3, B4, B5. , Attached to the hull of B6.

Here, in the following description, boats B1, B2, B3, B4, B5, B6, cameras C1, C2, C3, C4, C5, C6, radio units D1, D2, D3, D4, D5, D6, first. When the antennas E1, E2, E3, E4, E5, E6 and the second antennas F1, F2, F3, F4, F5, F6 are collectively referred to, the boat B, the camera C, the radio unit D, the first antenna E and It is called the second antenna F.

The camera C, which is an image pickup device, is a small on-board camera installed on the hull so as to capture the traveling direction of the boat B, for example. The camera C is connected to the wireless unit D.
The wireless unit D digitally modulates a video signal captured by the camera C at a predetermined frequency by an OFDM (Orthogonal Frequency Division Multiplexing) method to generate a digital video signal. Then, the wireless unit D amplifies the power of the digital video signal and supplies it to the first antenna E. The first antenna E radiates a digital video signal given by the wireless unit D as a radio wave.

As described above, the boat B travels at high speed in the competition area A. Then, the digital video signals of the video captured by the camera C during this traveling are wirelessly transmitted as radio waves from the first antenna E, respectively. Here, each wireless unit D1, D2, D3, D4, D5, D6 digitally modulates the video signal by the OFDM method using the frequencies of different frequency channels ch1, ch2, ch3, ch4, ch5, ch6. Therefore, radio waves of digital video signals digitally modulated at different frequencies are transmitted wirelessly from the first antennas E1, E2, E3, E4, E5, E6 of each boat B1, B2, B3, B4, B5, B6. Will be done. Therefore, the radio waves transmitted wirelessly from each of the first antennas E1, E2, E3, E4, E5, E6 do not interfere with each other.
It should be noted that the digital video signal of the video captured by the camera C is wirelessly transmitted from the first antenna E not only during traveling. Needless to say, digital video signals can be transmitted wirelessly even when stopped.

The video receiving system 1 has a plurality of receivers 11a, 11b, 11c, 11d distributed around the area A (four in the figure), and the same number of O's as the receivers 11a, 11b, 11c, 11d. A signal processing unit 14, a control unit 15, a storage unit 16, and a control radio that are common to the / E conversion units 12a, 12b, 12c, 12d and each O / E conversion unit 12a, 12b, 12c, 12d. Including machine 17.

The receivers 11a, 11b, 11c, 11d include receiving antennas 111a, 111b, 111c, 111d and E / O conversion units 112a, 112b, 112c, 112d. Then, the video receiving system 1 is located between the E / O conversion units 112a, 112b, 112c, 112d of the receivers 11a, 11b, 11c, 11d and the corresponding O / E conversion units 12a, 12b, 12c, 12d. Are connected by optical fiber cables 13a, 13b, 13c, and 13d, respectively.

Here, in the following description, receivers 11a, 11b, 11c, 11d, receiving antennas 111a, 111b, 111c, 111d, E / O conversion units 112a, 112b, 112c, 112d, O / E conversion units 12a, 12b, When the 12c, 12d and the optical fiber cables 13a, 13b, 13c, and 13d are collectively referred to, they are referred to as a receiver 11, a receiving antenna 111, an E / O conversion unit 112, an O / E conversion unit 12, and an optical fiber cable 13, respectively. ..

The receiving antenna 111 is a directional antenna and receives radio waves wirelessly transmitted from the first antennas E1, E2, E3, E4, E5, E6 of each boat B1, B2, B3, B4, B5, B6. , Arranged with directivity on the area A side. The E / O conversion unit 112 converts the electric signal of the radio wave received by the receiving antenna 111 into an optical signal. Then, the E / O conversion unit 112 outputs an optical signal to the optical fiber cable 13. The optical fiber cable 13 transmits the optical signal output from the E / O conversion unit 112 to the O / E conversion unit 12. The O / E conversion unit 12 converts an optical signal input via the optical fiber cable 13 into an electric signal and appropriately amplifies it. Then, the O / E conversion unit 12 outputs this electric signal to the signal processing unit 14.

Most of the electrical signals obtained by the optical / electrical conversion in the O / E conversion unit 12 are digital video signals that are wirelessly transmitted from the boat B and received by the receiver 11. Therefore, the signal processing unit 14 uses the frequency channels ch1 used in each of the wireless units D1, D2, D3, D4, D5, and D6 from the electric signals output from the O / E conversion units 12a, 12b, 12c, and 12d. , Ch2, ch3, ch4, ch5, ch6 signals are extracted, and OFDM demodulation is performed on the signals. Then, the signal processing unit 14 performs diversity synthesis or the like of the signal obtained by OFDM demodulation for each frequency channel ch1, ch2, ch3, ch4, ch5, ch6 to obtain a digital video signal, and further decodes the digital video signal. Then, a video output signal for each frequency channel ch1, ch2, ch3, ch4, ch5, ch6 is obtained. The signal processing unit 14 outputs the video output signal for each frequency channel ch1, ch2, ch3, ch4, ch5, ch6 to the display device 2. Thus, the images captured by the cameras C1, C2, C3, C4, C5, C6 mounted on the boats B1, B2, B3, B4, B5, B6 are displayed on the display device 2 in real time.

Incidentally, the display device 2 is typically a large display installed in the hall. However, the display device 2 is not particularly limited as long as it can project an image taken by the camera C. Further, instead of selectively switching and displaying the images of the cameras C1, C2, C3, C4, C5, and C6 on one display device 2, a plurality of display devices 2 may display the images at the same time.

The control unit 15 includes a processor such as a CPU (Central Processing Unit), and is responsible for overall control of the video receiving system 1. In the video receiving system 1, a signal processing unit 14, a storage unit 16, and a control radio 17 are connected to the control unit 15. Further, for example, various commands are input to the control unit 15 from a control panel installed in a control center or the like in the hall. The command may be input to the control unit 15 by connecting the control panel and the control unit 15 with a signal line, or the command may be wirelessly transmitted from the radio connected to the control panel to control the radio. It may be input to the control unit 15 via the machine 17.

The storage unit 16 includes a main memory of ROM (Read Only Memory) and RAM (Random Access Memory), and an EEPROM (Electric Erasable Programmable Read-Only Memory), HDD (Hard Disc Drive), SSD (Solid State Drive), or the like. Includes auxiliary storage devices. The ROM stores a program or the like executed by the processor constituting the control unit 15. Various data are written to the RAM and the auxiliary storage device according to the instruction of the control unit 15, and various data are read out.

The control radio 17 performs wireless communication with the radio unit D via the second antenna F attached to the boat B. The frequency band used for this wireless communication is different from the band of the frequency channel used in each wireless unit D1, D2, D3, D4, D5, D6.

FIG. 2 is a block diagram showing a main circuit configuration of the wireless unit D. The radio unit D includes a radio unit 31, a monitoring control unit 32, an encoder 33, a multiplexing unit 34, an OFDM modulation unit 35, and a power amplification unit 36. Then, the first antenna E is connected to the power amplification unit 36, and the second antenna F is connected to the radio 31.

The radio unit 31 performs wireless communication with the control radio unit 17 via the second antenna F. The radio unit 31 is connected to the monitoring control unit 32, and sends control information from the control unit 15 received via the second antenna F to the monitoring control unit 32. The monitoring control unit 32 controls the wireless unit D according to the above control information. For example, the monitoring control unit 32 is connected to the OFDM modulation unit 35, and sets the frequency channel used by the OFDM modulation unit 35 according to the control information.

A GPS receiver 3 and a vibration sensor 4 are connected to the monitoring control unit 32. Both the GPS receiver 3 and the vibration sensor 4 are mounted on the boat B. The monitoring control unit 32 captures the position information of the boat B positioned by the GPS receiver 3. Further, the monitoring control unit 32 captures the hull vibration information of the boat B detected by the vibration sensor 4. The monitoring control unit 32 is connected to the multiplexing unit 34, and sends out the position information of the boat B and the hull vibration information to the multiplexing unit 34. Further, an appropriate coding parameter may be given to the encoder 33 according to the hull vibration information.

The encoder 33 is connected between the camera C mounted on the boat B and the multiplexing unit 34. The encoder 33 encodes the video signal captured by the camera C by the H.265 method or the like and sends it to the multiplexing unit 34.

The multiplexing unit 34 multiplexes the digital video signal encoded by the encoder 33 and the position information and hull vibration information of the boat B given by the monitoring control unit 32. Then, the multiplexing unit 34 appropriately performs error correction coding processing on the TS signal generated by this multiplexing and sends it to the OFDM modulation unit 35.

The OFDM modulation unit 35 encodes the TS signal given from the multiplexing unit 34 as a transmission line code and OFDM-modulates it to generate an OFDM signal of a predetermined frequency channel, for example, a frequency channel in the 5 GHz band having an occupied bandwidth of 5 MHz. do. Then, the OFDM modulation unit 35 sends the OFDM signal to the power amplification unit 36. This OFDM signal is a digital signal in which the position information of the boat B and the hull vibration information are superimposed on the digital video signal.

The power amplification unit 36 amplifies the OFDM signal given by the OFDM modulation unit 35, and then sends the OFDM signal to the first antenna E. Thus, the radio wave of the digital signal in which the position information of the boat B and the vibration information of the hull are superimposed on the digital video signal is wirelessly transmitted from the first antenna E. The radio waves wirelessly transmitted from the first antenna E are received by the receiving antennas 111a, 111b, 111c, 111d of the receivers 11a, 11b, 11c, 11d arranged around the area A.

FIG. 3 is a block diagram showing a main circuit configuration of the E / O conversion unit 112 in the receiver 11. The E / O conversion unit 112 includes a bandpass filter 41, a high frequency switch 42, an E / O circuit 43, a detection circuit 44, and a comparison circuit 45. The bandpass filter 41 suppresses radio waves in an unnecessary band other than the band used in the system from the radio waves received by the receiving antenna 111. The band used in this example is 5650 to 5755 MHz. Then, the electric signal of the radio wave from which the radio wave of the unnecessary band is removed by the bandpass filter 41 is supplied to the E / O circuit 43 via the high frequency switch 42. The high frequency switch 42 is normally conducting.

The E / O circuit 43 is composed of a high frequency amplifier and a laser diode. The E / O circuit 43 amplifies a high-frequency electric signal input via the high-frequency switch 42 with a high-frequency amplifier. Then, the E / O circuit 43 modulates the intensity of the light emitted from the laser diode with the amplified high-frequency electric signal, converts the electric signal into an optical signal, and outputs the electric signal to the optical fiber cable 13.

The detection circuit 44 detects the power level of the electric signal passing through the bandpass filter 41. Then, the detection circuit 44 sends a detection output signal corresponding to the power level to the comparison circuit 45.

The comparison circuit 45 compares the power level of the detection output signal with the preset power level Lx. Then, when the power level of the detection output signal exceeds the first power level Lx, the comparison circuit 45 outputs the off signal to the high frequency switch 42. In response to this off signal, the high frequency switch 42 is opened. Further, after the cutoff signal S is output, the comparison circuit 45 compares the power level of the detection output signal with the preset second power level Ly. The second power level Ly is set to be smaller than the first power level Lx. Then, when the power level of the detection output signal becomes less than the second power level Ly, the comparison circuit 45 outputs the on signal to the high frequency switch 42. In response to this on signal, the high frequency switch 42 conducts again.

In this way, the E / O conversion unit 112 of the receiver 11 converts the electric signal obtained by excluding the radio wave in the unnecessary band from the radio wave received by the receiving antenna 111 into an optical signal. Then, this optical signal is sent to the O / E conversion unit 12 via the optical fiber cable 13. However, when an electric signal having an excessive power level is input to the E / O conversion unit 112, the high frequency switch 42 is opened to cut off the electric signal. Therefore, an electric signal having an excessive power level is not input to the E / O circuit 43. Therefore, the laser diode of the E / O conversion unit 112 does not clip due to the application of an electric signal having an excessive power level.

A low noise amplifier and an AGC gain controller may be connected to the output of the bandpass filter 41 to adjust the power level of the electric signal so that the E / O circuit 43 is not saturated. Further, in order to perform optical power supply, a spectroscopic filter or the like is provided between the E / O circuit 43 and the optical fiber cable 13, and the light supplied from the O / E conversion unit side is converted into electric power to convert the light into electric power. It may be configured to be used for driving the 43 or the like.

FIG. 4 is a block diagram showing a main circuit configuration of the signal processing unit 14. The signal processing unit 14 includes a plurality of conversion and distribution units 51a, 51b, 51c, 51d, OFDM demodulation units 52a, 52b, 52c, 52d, diversity processing circuits 53a, 53b, 53c, 53d, 53e, 53f, 53g and a decoder 54a, respectively. , 54b, 54c, 54d, 54e, 54f. The conversion distribution units 51a, 51b, 51c, and 51d are provided corresponding to the O / E conversion units 12a, 12b, 12c, and 12d, respectively. The OFDM demodulation units 52a, 52b, 52c, 52d are provided corresponding to the conversion distribution units 51a, 51b, 51c, 51d, respectively. The diversity processing circuits 53a, 53b, 53c, 53d, 53e, 53f, 53g are provided as many as the number of frequency channels distributed by the conversion distribution units 51a, 51b, 51c, 51d. The decoders 54a, 54b, 54c, 54d, 54e, 54f are used in the respective radio units D1, D2, D3, D4, D5, D6 among the frequency channels distributed by the conversion distribution units 51a, 51b, 51c, 51d. As many frequency channels as ch1, ch2, ch3, ch4, ch5, and ch6 are provided.

Here, in the following description, the conversion and distribution units 51a, 51b, 51c, 51d, the OFDM demodulation units 52a, 52b, 52c, 52d, the diversity processing circuits 53a, 53b, 53c, 53d, 53e, 53f, 53g and the decoder 54a, When 54b, 54c, 54d, 54e, and 54f are collectively referred to, they are referred to as a conversion distribution unit 51, an OFDM demodulation unit 52, a diversity processing circuit 53, and a decoder 54, respectively.

The conversion distribution unit 51 includes a local oscillator 511, a mixer (mixer) 512, and a plurality of frequency filters 513a, 513b, 513c, 513d, 513e, 513f, 513g. Regarding the frequency filters 513a to 513g, only the generic reference numeral 513 is attached in FIG. Reference numerals 513a, 513b, 513c, 513d, 513e, 513f, and 513g are assumed to be attached to the frequency filter 513 in order from the top of the figure.

The local oscillator 511 generates a high frequency signal for frequency conversion of the frequency band used in the video receiving system 1. The high frequency signal is input to the mixer 512. An electric signal is also input to the mixer 512 from the O / E conversion unit 12. The mixer 512 mixes or orthogonally detects the electric signal and the high frequency signal to obtain a desired intermediate frequency signal. This intermediate frequency signal is appropriately subjected to image suppression filter processing and A / D conversion, and distributed to each frequency filter 513a to 513g.

Of the frequency filters 513a to 513g, the frequency filter 513a is a polyphase filter or the like, and the passing frequency band is set so that the intermediate frequency signal of the frequency channel ch1 used in the radio unit D1 mounted on the boat B1 passes through. Has been done. Similarly, the frequency filters 513b, 513c, 513d, 513e and 513f pass the intermediate frequency signals of the frequency channels ch2, ch3, ch4, ch5, ch6 used in the radio units D2, D3, D4, D5 and D6, respectively. The passing frequency band is set as such. On the other hand, in the frequency filter 513g, the passing frequency band is set so that the intermediate frequency signal of the frequency band (hereinafter referred to as an empty channel) other than the passing frequency band set in the other frequency filters 513a to 513f passes through. There is. Here, the free channel is a frequency band of a signal that can be an interfering wave with respect to the frequency signals of the frequency channels ch2, ch3, ch4, ch5, and ch6 used in the radio units D1 to D6.

The OFDM demodulation unit 52 OFDM demodulates the frequency channels ch1 to ch6 extracted by passing through the frequency filters 513a to 513g of the corresponding conversion distribution unit 51 and the intermediate frequency signal (OFDM signal) for each free channel. It is not necessary to perform demodulation on an empty channel. In the process of this OFDM demodulation, the OFDM demodulation unit 52 may separate the digital video signal and the position information of the boat B and the hull vibration information superimposed on the digital video signal from the intermediate frequency signal. Then, the OFDM demodulation unit 52 sends the digital video signals that have been OFDM demodulated and equalized for each of the frequency channels ch1 to ch6 and the free channels to the diversity processing circuit 53 in the subsequent stage, and transmits the position information of the boat B and the hull vibration information. It is sent to the control unit 15.

Further, in the process of OFDM demodulation, the OFDM demodulation unit 52 detects the received electric field level of the OFDM signal for each OFDM signal. Further, the OFDM demodulation unit 52 detects the CN (Carrier to Noise) ratio at the time of demodulating the OFDM signal for each OFDM signal. Then, the OFDM demodulation unit 52 outputs the received electric field level and CN ratio detected for each OFDM signal to the control unit 15. For the detection of the received electric field level and the CN ratio, for example, a well-known method disclosed in Japanese Patent No. 4354004 may be used.

The diversity processing circuit 53a corresponding to the frequency channel ch1 used in the wireless unit D1 inputs the digital video signal of the frequency channel ch1 that has been OFDM demodulated in each OFDM demodulation unit 52a, 52b, 52c, 52d. Then, the diversity processing circuit 53a generates a high-quality digital video output signal with less noise by performing diversity processing on each digital video signal by the maximum ratio synthesis method, and sends it to the corresponding decoder 54a. Further, the diversity processing circuit 53a outputs data indicating the ratio of the digital video signals that contributed to the generation of the digital video output signal to the control unit 15 as diversity information.

Similarly, the diversity processing circuits 53b to 53f corresponding to the frequency channels ch2 to ch6 used in the wireless units D2 to D6 are the frequency channels ch2 to ch6 that have been OFDM demodulated in the OFDM demodulation units 52a, 52b, 52c, 52d. Input a digital video signal. Then, the diversity processing circuits 53b to 53f perform diversity processing on each digital video signal by the maximum ratio synthesis method, perform demapping, generate a digital video output signal, and send it to the corresponding decoders 43b to 43f. Further, the diversity processing circuits 53b to 53f output data indicating the ratio of the digital video signals that contributed to the generation of the digital video output signal to the control unit 15 as diversity information. The diversity processing is not limited to the maximum ratio synthesis method. For example, the highest quality digital video signal may be selected as the digital video output signal from each digital video signal. In this case, as the diversity information, the ratio of the selected digital video signal is 100%, and the ratio of the other digital video signals not selected is 0%.

On the other hand, the diversity processing circuit 53g corresponding to the vacant channel not used in the wireless units D2 to D6 performs the diversity processing on the digital signal of the vacant channel.

Unlike the other diversity processing circuits 53a to 53f, the diversity processing circuit 53g is a radio signal from another system, and therefore the purpose is mainly to detect the reception level as the interference level. The diversity process includes, for example, a process of energizing and summing the signals of free channels from each receiver 11.

The decoder 54 decodes the digital video output signal output from the corresponding diversity processing circuit 53. Then, the decoder 54 outputs the video output signal obtained by the decoding to the display device 2.

As described above, the conversion distribution unit 51 and the OFDM demodulation unit 52 are provided corresponding to the receivers 11a, 11b, 11c, and 11d, respectively. Then, the video signal (OFDM modulated signal) received by the conversion distribution unit 51 and the corresponding receivers 11a, 11b, 11c, 11d is used in the frequency channels D1, D2, D3, D4, D5, D6 of each wireless unit. It is distributed to each of ch1, ch2, ch3, ch4, ch5, and ch6. The OFDM demodulation unit 52 demodulates the video signal distributed by the conversion distribution unit 51 by the OFDM method. Here, the conversion distribution unit 51 and the OFDM demodulation unit 52 form a first signal processing unit.

On the other hand, the diversity processing circuit 53 performs diversity processing on the video signals of the same frequency channel from the video signals of each frequency channel demodulated by the plurality of first signal processing units, so that the quality of the video signals is high for each frequency channel. Generates a digital video output signal. Then, the decoder 54 decodes each of the digital video signals generated for each frequency channel by the corresponding diversity processing circuit 53, and outputs the digital video signal to the display device 2. Here, the diversity processing circuit 53 and the decoder 54 form a second signal processing unit.

The first signal processing unit is not limited to the one composed of the conversion distribution unit 51 and the OFDM demodulation unit 52. The first signal processing unit may be configured by including other components. Similarly, the second signal processing unit is not limited to that composed of the diversity processing circuit 53 and the decoder 54. The second signal processing unit may be configured by including other components.

5 and 6 are flow charts showing the main control procedures of the control unit 15. Therefore, next, the operation of the control unit 15 will be described with reference to FIGS. 5 and 6. In order to explain this operation, the video receiving system 1 forms the channel setting table 60 of the data structure shown in FIG. 7 in the storage unit 16. Therefore, first, the channel setting table 60 will be described.

As shown in FIG. 7, the channel setting table 60 has an area 61 for storing the channel number in association with the boat ID. The boat ID is a unique ID (moving body ID) assigned in advance to individually identify the moving boats B1, B2, B3, B4, B5, B6. In the channel setting table 60, the channel number of the frequency channel used in the boat B specified by the boat ID is set in the area 61. For example, in the video receiving system 1, assuming that the number of channels in the frequency band used for wireless transmission of video signals is 21, and channel numbers from "1" to "21" are assigned to each, the channel setting table A channel number from "1" to "21" is set in the area 61 of 60. Then, the control unit 15 controls the passing frequency band of each frequency filter 513a to 513g of the conversion distribution unit 51 so that the frequency of the channel number set in the channel setting table 60 passes.

(motion)
Now, the control unit 15 is waiting for a command to establish an initial line as step S1 in FIG. The command for establishing the initial line is given from the control panel described above.
Upon receiving the command for establishing the initial line (YES in step S1), the control unit 15 controls the transmission output off command to be wirelessly transmitted from the control radio 17 as step S2. By this control, the transmission output off command is wirelessly transmitted from the control radio 17. This command is received by the radio unit 31 of the radio unit D mounted on the boat B in the area A. In the wireless unit D that has received the transmission output off command, the wireless transmission output from the first antenna E is stopped by the control of the monitoring control unit 32.

After outputting the transmission output off command, the control unit 15 searches for the frequency channel used by the radio units D1 to D6 of the boats B1 to B6 in step S3. Then, the control unit 15 selects as many frequency channels as the number of wireless units D1 to D6 that are not adjacent to each other between the wireless units D1 to D6.

After completing the search for the frequency channel, the control unit 15 sets the channel number of the frequency channel obtained by the search as step S4 in the area 61 of the channel setting table 60. For example, if the frequency channels of the channel numbers “2”, “5”, “8”, “11”, “14”, and “17” are selected, the control unit 15 sets the channel in the area 61 of the channel setting table 60. The numbers "2", "5", "8", "11", "14", and "17" are set in order.

In step S5, the control unit 15 controls so that the data in the channel setting table 60 is wirelessly transmitted from the control radio 17. By this control, the data in the channel setting table 60 is wirelessly transmitted from the control radio 17. This data is received by the radio unit 31 of the radio unit D mounted on the boat B in the area A. The monitoring control unit 32 detects the channel number associated with the boat ID of the boat B on which the own radio unit D is mounted from the data in the channel setting table 60. Then, the monitoring control unit 32 controls the frequency channel of the channel number to be used by the OFDM modulation unit 35.

As step S6, the control unit 15 controls so that the transmission output ON command is wirelessly transmitted from the control radio 17. By this control, a command to turn on the transmission output is wirelessly transmitted from the control radio 17. This command is received by the radio unit 31 of the radio unit D mounted on the boat B in the area A. In the wireless unit D that has received the transmission output on command, the wireless transmission output from the first antenna E is restarted under the control of the monitoring control unit 32. As a result, from the first antenna E, a signal obtained by OFDM-modulating the video signal captured by the camera C on the frequency channel determined by the control unit 15 is radiated as a radio wave.

This radio wave is received by the receiving antennas 111a, 111b, 111c, 111d of the receivers 11a, 11b, 11c, 11d arranged around the area A, and is converted into an optical signal by the E / O conversion unit 112. The optical fiber cable 13 is transmitted. Then, it is reconverted into an electric signal by the O / E conversion unit 12 and sent to the signal processing unit 14.

The signal processing unit 14 extracts OFDM signals of frequency channels of, for example, channel numbers “2”, “5”, “8”, “11”, “14”, and “17” from the electric signal. Then, OFDM demodulation is performed for each OFDM signal. In the process of this OFDM demodulation, the received electric field level and the CN ratio detected for each frequency channel are given to the control unit 15.

The control unit 15 confirms the received electric field level and CN ratio for each frequency channel detected by the signal processing unit 14 in step S7. Then, the control unit 15 determines whether or not it is necessary to redo the determination of the channel to be used as step S8. For example, if there is a frequency channel whose received electric field level is lower than the specified value, or when there is a frequency channel whose CN ratio is worse than the specified value, the control unit 15 determines to redo (YES in step S8). Then, the control unit 15 returns to the process of step S3. That is, the control unit 15 re-searches for the frequency channel used by the radio units D1 to D6 of the boats B1 to B6.

If the received electric field level is lower than the specified value or the CN ratio is worse than the specified value, it is presumed that the transmission quality is deteriorated due to interference with the radio waves used in other wireless systems. NS. Therefore, during re-exploration, frequency channels whose received electric field level is lower than the specified value and frequency channels adjacent to it are excluded. Similarly, frequency channels having a CN ratio lower than the specified value and adjacent frequency channels are also excluded. After that, the control unit 15 repeats the same processing as described above.

On the other hand, if it is determined not to redo (NO in step S8), the control unit 15 waits for the control start command as step S9. The control start command is also given from the control panel in the same way as the initial line establishment command.

Upon receiving the control start command (YES in step S9), the control unit 15 starts the monitoring timer as step S10. The monitoring timer is built in the control unit 15. The control unit 15 waits for the monitoring timer to time out as step S11. When the monitoring timer times out (YES in step S11), the control unit 15 executes the communication state memory process of the procedure shown in steps P1 to P5 of FIG. 6 as step S12.

First, the control unit 15 acquires the time measured by the clock unit as step P1. The clock unit is built in the control unit 15.
Next, the control unit 15 acquires the received electric field level and the CN ratio from each OFDM demodulation unit 52 as step P2. That is, from the OFDM demodulation unit 52a, the received electric field level and the CN ratio received by the receiver 11a and detected for each digital signal distributed for each frequency channel are acquired. Similarly, from the OFDM demodulation units 52b, 52c, 52d, the received electric field level and the CN ratio received by the receivers 11b, 11c, 11d and detected for each digital signal distributed for each frequency channel are acquired.

Next, the control unit 15 acquires position information and vibration information from each OFDM demodulation unit 52 as step P3. That is, from the OFDM demodulation unit 52a, the position information and the vibration information received by the receiver 11a and superimposed on the digital signals distributed for each frequency channel are acquired. Similarly, from the OFDM demodulation units 52b, 52c, 52d, the position information and the vibration information received by the receivers 11b, 11c, 11d and superimposed on the digital signals distributed for each frequency channel are acquired. It should be noted that the position information and the vibration information do not necessarily have to be acquired from all the OFDM demodulation units 52a to 52d. It may be acquired from at least one OFDM demodulation unit 52a to 52d.

Next, the control unit 15 acquires diversity information from each diversity processing circuit 53 as step P4. That is, from the diversity processing circuit 53a, the digital video signal of the frequency channel ch1 demodulated by each OFDM demodulation unit 52a to 52d is subjected to diversity processing by the maximum ratio synthesis method, and as a result, the digital video signal that contributes to the generation of the digital video output signal is generated. Get data showing the ratio. Similarly, from the diversity processing circuits 53b, 53c, 53d, 53e, 53f, the maximum ratio synthesis method is used for the digital video signals of the frequency channels ch2, ch3, ch4, ch5, ck6 demodulated by the OFDM demodulation units 52a to 52d. As a result of diversity processing, data showing the ratio of digital video signals that contributed to the generation of digital video output signals is acquired. Further, from the diversity processing circuit 53g, the data of the result of the diversity processing of the digital video signal of the free channel by the maximum ratio synthesis method is acquired.

Finally, as step P5, the control unit 15 creates a data file that stores the received electric field level, CN ratio, position information, vibration information, and diversity information in association with the time based on the information acquired in steps P1 to P4. , Stored in the storage unit 16 in chronological order.

When the communication state memory process is completed, the control unit 15 evaluates the communication state based on the data files stored in the storage unit 16 in time series as step S13. Then, the control unit 15 determines whether or not the communication state is stable in step S14.
For example, when the received electric field level is lower than the specified value for a predetermined time or longer, or the CN ratio is worse than the specified value for a predetermined time or longer, the control unit 15 is in a communication state. Judge that it is not stable.

When the communication state is stable (YES in step S14), the control unit 15 determines whether or not the control end command has been received as step S15. If the control end command has not been received (NO in step S15), the control unit 15 returns to the process of step S10. Then, the control unit 15 repeats the processes after step S10 in the same manner as described above.

On the other hand, if the communication state is not stable (NO in step S14), the control unit 15 returns to the process of step S2. Then, the control unit 15 repeats the processes after step S2 in the same manner as described above.

The control end command is also given from the control panel in the same way as the control start command and the like. That is, when the control end command is received (YES in step S15) in the situation where the communication state is stable, the control unit 15 executes the communication end process as step S16. For example, the control unit 15 stops the operation of the signal processing unit 14. With the above, the control unit 15 ends the control process after receiving the command for establishing the initial line.

The content of the control process described with reference to FIGS. 5 and 6 is based on the program stored in the storage unit 16. This content is an example, and the processing procedure and processing content are not particularly limited as long as similar results can be obtained.

(Action effect)
As described above, in the present embodiment, the video signal captured by the camera C mounted on the boat B traveling in the area A is digitally measured at the frequency of the frequency channel set for the wireless unit D of the boat B. It is modulated and wirelessly transmitted from the first antenna E. This video signal is received by a plurality of receivers 11a, 11b, 11c, 11d arranged around the area A. The video signals received by the receivers 11a, 11b, 11c, and 11d are subjected to diversity processing by the maximum ratio synthesis method for each video signal of the same frequency channel in the diversity processing circuit 53 of the signal processing unit 14. A high-quality video output signal is generated and output to the display device 2. At this time, diversity information indicating the ratio of the video signals that contributed to the generation of the video output signal is transmitted from the signal processing unit 14 to the control unit 15 and stored in the storage unit 16.

Therefore, by analyzing the diversity information stored in the storage unit 16 with a computer terminal installed in, for example, a control center in the field, a video signal having a high rate of contributing to the generation of the video output signal is received. It is possible to distinguish between the receiver 11 that is receiving and the receiver 11 that is not receiving. Regarding the latter receiver 11, for example, the installation position of the receiving antenna 111 and the direction of directivity will be reviewed. By doing so, when the transmission quality of the video signal is improved and the video signal having a high contribution rate can be received, it can be identified that the cause of the deterioration of the transmission quality of the video signal is on the receiver 11 side. .. On the contrary, if the situation does not change even if the installation position of the receiving antenna 111 and the direction of the directivity are reviewed and the video signal having a high contribution rate cannot be received, the radio unit D mounted on the transmitter side, that is, the boat B is used. I can guess that there is a problem.

Further, in the present embodiment, when the video signal distributed for each frequency by the conversion distribution unit 51 of the signal processing unit 14 is demodulated by the OFDM demodulation unit 52, the received electric field level and the code error rate of the video signal are detected. Will be done. Then, the information on the received electric field level and the code error rate is sent to the control unit 15 and stored in the storage unit 16.

Therefore, for example, by analyzing the information on the received electric field level and the code error rate together with the diversity information on the computer terminal, it becomes possible to identify the cause of the deterioration of the transmission quality in consideration of the reception status of each receiver 11. As a result, the factors can be identified with high reliability.

Further, in the present embodiment, the data of the GPS receiver 3 and the vibration sensor 4 mounted on the boat B, that is, the position information of the boat B and the hull vibration information are superimposed on the video signal of the camera C and transmitted. Then, in the video receiving system 1, when the video signal is demodulated by the OFDM demodulation unit 52 of the signal processing unit 14, the position information of the boat B and the hull vibration information superimposed on the video signal are detected. Then, the position information of the boat B and the hull vibration information are transmitted to the control unit 15 and stored in the storage unit 16.

Therefore, for example, by analyzing the information on the received electric field level and the code error rate together with the diversity information on the computer terminal, it becomes possible to identify the cause of the deterioration of the transmission quality in consideration of the movement state of the boat B. As a result, it becomes possible to easily infer whether the cause of the deterioration of the transmission quality of the video signal is the vibration of the hull or the corresponding positional relationship between the boat B and the receiver 11.

Further, in the present embodiment, the signal processing unit 14 also performs diversity processing on the signal of the frequency channel not used by the wireless unit D, and stores the result in the storage unit 16. Therefore, since the frequency channel that can be a disturbing wave can be specified with respect to the signal of the frequency channel used in the radio unit D, it can be useful for determining the frequency channel used in the radio units D1 to D6 of the boats B1 to B6.

Further, in the present embodiment, the E / O conversion unit 112 of the receiver 11 provided with the E / O circuit 43 is provided with a switching function so that an electric signal having an excessive power level is not applied to the E / O circuit 43. Therefore, since the laser diode of the E / O conversion unit 112 can be prevented from clipping, the quality of the optical signal transmitted through the optical fiber cable 13 can be improved, and the quality of the camera image output can be improved.

(Modification example)
In the above embodiment, when the video signal distributed for each frequency channel is demodulated, both the received electric field level and the code error rate of the video signal are detected and stored in the storage unit 16. Regarding this point, either the received electric field level or the code error rate may be stored in the storage unit 16. By storing either the received electric field level or the code error rate, it is possible to identify the cause of the deterioration of transmission quality.

Further, in the above embodiment, the boat B is equipped with a GPS receiver 3 and a vibration sensor 4, and the position information of the boat B and the hull vibration information are measured and stored in the storage unit 16. Regarding this point, either the GPS receiver 3 or the vibration sensor 4 may be equipped on the boat B, and either the position information or the hull vibration information may be stored in the storage unit 16.

Further, in the above embodiment, the case where it is applied to the system of the boat racetrack has been exemplified, but the present invention is not limited thereto. For example, it can be applied to a video reception system for public stadiums such as auto races, bicycle races, and horse races, and other motor race fields.

The present invention is not limited to the above embodiment, and can be variously modified at the implementation stage without departing from the gist thereof. In addition, each embodiment may be carried out in combination as appropriate, in which case the combined effect can be obtained. Further, the above-described embodiment includes various inventions, and various inventions can be extracted by a combination selected from a plurality of disclosed constituent requirements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, if the problem can be solved and the effect is obtained, the configuration in which the constituent elements are deleted can be extracted as an invention.

B (B1 to B6) ... boat, C (C1 to C6) ... camera, D (D1 to D6) ... wireless unit, E (E1 to E6) ... first antenna, F (F1 to F6) ... second antenna, 1 ... Video receiving system, 2 ... Display device, 3 ... GPS receiver, 4 ... Vibration sensor, 11 (11a to 11d) ... Receiver, 12 (12a to 12d) ... O / E converter, 13 (13a to 13d) ) ... Optical fiber cable, 14 ... Signal processing unit, 15 ... Control unit, 16 ... Storage unit, 17 ... Control radio, 31 ... Radio, 32 ... Monitoring control unit, 33 ... Encoder, 34 ... Multiplying unit, 35 ... OFDM modulation section, 36 ... Power amplification section, 41 ... Band path filter, 42 ... High frequency switch, 43 ... E / O circuit, 44 ... Detection circuit, 45 ... Comparison circuit, 51 (51a to 51d) ... Conversion distribution section , 52 (52a to 52d) ... OFDM demodulation unit, 53 (53a to 53g) ... diversity processing circuit, 54 (54a to 54f) ... decoder, 60 ... channel setting table, 112 ... E / O conversion unit.

Claims (4)

Multiple receivers that receive video signals that are modulated and wirelessly transmitted at different frequencies from multiple moving objects that move within the moving area.
The video signal provided corresponding to each of the plurality of receivers and received by the corresponding receiver is distributed and demodulated for each frequency, and further superimposed on the video signal wirelessly transmitted from the mobile body. A plurality of first signal processing units for detecting at least one of the position information and the vibration information of the moving body,
A second signal processing unit that generates and outputs a video output signal from the video signals of the same frequency demodulated by the plurality of first signal processing units, respectively.
A storage unit that stores information related to the receiver that has received the video signal that contributed to the generation of the video output signal output from the second signal processing unit, and at least one of the position information and the vibration information. ,
A video receiving system equipped with. The first signal processing unit detects at least one of the received electric field level and the code error rate of the video signal when demodulating the video signal distributed for each frequency.
The video receiving system according to claim 1, wherein the storage unit further stores information detected by the first signal processing unit. A control unit that determines the communication status of the plurality of receivers based on the information related to the receiver stored in the storage unit.
The video receiving system according to claim 1 or 2, further comprising. The receiver is
An E / O circuit that converts video signals into optical signals,
A detection circuit that detects the power level of the received video signal,
A comparison circuit that compares the power level detected by the detection circuit with the set level,
As a result of comparison by the comparison circuit, when the power level is less than the set level, the video signal is passed through the E / O circuit, and when the power level becomes equal to or higher than the set level, the E / O of the video signal is passed. A switch that cuts off the output to the circuit,
The video receiving system according to any one of claims 1 to 3.

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