JPH0763158B2 - Wireless relay system - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless relay system including wireless relay devices installed at a plurality of locations for relaying wireless stations including mobile wireless stations.

[Prior art]

The wireless relay device must be designed to have an output that covers a predetermined range depending on various conditions, so consider placing multiple wireless relay devices at appropriate locations to increase relay efficiency for wireless stations at various locations. Has been done. Various methods have been proposed as a wireless relay system including wireless relay devices installed at a plurality of locations. The first method is a method in which the transmission frequencies of the wireless relay devices are the same so that the frequency selection (channel switching) operation in each wireless station is not required. In this case, a mobile or fixed wireless station in an area where a plurality of wireless relay devices can be used receives a plurality of relay radio waves having frequency deviations from a plurality of wireless relay devices, and the frequency deviations cause the relay waves. Communication is difficult due to beat interference. This is because all the wireless relay devices are installed in different locations, so the effects of temperature, humidity, vibration, etc. on the oscillators of each wireless relay device are also different, and the oscillation frequency fluctuates and the transmission frequency fluctuates. Is. Therefore, in order to eliminate the beat interference, each wireless relay device requires a highly accurate and highly stable reference signal oscillator such as a crystal oscillator installed in a stable environment. Has the drawback of being very costly. For this reason, the following methods have been adopted from the past. That is, it is a method of eliminating the beat interference by configuring the transmission frequencies of the respective wireless relay devices to be different frequencies. Although beat interference can be eliminated by this, on the other hand, each wireless station must be provided with means for selecting each frequency, and the wireless station will move or try to use it. Each time the wireless relay device was changed, the frequency switching operation had to be performed. Further, as disclosed in Japanese Patent Laid-Open No. 59-21142, in a relay system configured to relay the transmission from the master station to the slave station by the relay station, the master station is routed through the relay station. In order to synchronize all local oscillators in the master station, relay station and slave station with reference to the main oscillation of the master station, for example,
There is also a wireless relay system that is configured to transmit to a relay station by frequency modulation that faithfully transmits with a synchronous frequency of 3 kHz as a reference frequency, modulate the frequency at the received relay station and transmit to the slave station.

[Problems to be Solved by the Invention]

As described above, when the transmission frequency of each wireless relay device is set to the same frequency, a highly accurate and highly stable oscillation device such as a crystal oscillator installed in a stable environment in order to prevent beat interference is used for each wireless relay device. Therefore, there is a problem that the wireless relay device becomes large and expensive. Conversely, if the transmission frequency of each wireless relay device is set to a different frequency, beat interference disappears, but on the other hand, the wireless station side requires the function and operation of switching the frequency according to the wireless relay device to be used. There is a new problem. In this case, further, it is necessary to allocate a large number of frequencies to the wireless relay device, which makes it impossible to effectively use the limited resources, which is another problem. Further, in the wireless relay system disclosed in JP-A-59-21142, there is a problem that a filter for extracting the reference frequency (for example, 3 kHz) is specially required and the circuit configuration becomes complicated, There is also a problem that the characteristics of the low frequency demodulated by the characteristics of the filter are greatly affected and the quality of demodulation is degraded. Furthermore, since the reference frequency is transmitted at the same frequency as the information to be transmitted, the relay frequency is always occupied to transmit the reference frequency even if there is no information to be transmitted. Therefore, even though it is convenient to transmit information from a specific one station (for example, a master station) to an unspecified large number of slave stations, in the communication between the unspecified large number of wireless stations as intended by the present application, If the frequency is occupied, there is a problem that it cannot be used.

[Technical means for solving problems]

According to the present invention, even if the transmission frequencies of the wireless relay devices are not absolutely stable, if they are relatively stable, beat interference does not occur even if the transmission frequencies of the wireless relay devices are the same. Focusing on the points, the following measures were taken in order to solve the above problems. One is a wireless relay system in which a main wireless relay device and a slave wireless relay device are installed at a plurality of locations for relaying between a plurality of wireless stations including a mobile wireless station, and the main wireless relay device includes: Is a relay receiving unit that receives a signal from a wireless station, a reference frequency generating unit that outputs a reference frequency, and a relay transmission frequency that is generated based on the reference frequency, and the wireless station that is received by the relay receiving unit. And a reference signal transmitting means for generating a reference frequency signal having a frequency different from the relay transmission frequency on the basis of the reference frequency and transmitting the signal to another slave radio relay device. The sub-radio relay device includes a reference frequency receiving unit that receives the reference frequency signal, a transmission frequency generating unit that generates a relay transmission frequency synchronized with the reference frequency, and a signal from a wireless station. A relay receiving unit signals to, in the relay transmission frequency, in which took measures that includes a relay transmitting unit for transmitting a signal from the radio station which has received the relay receiver. A PLL synthesizer system may be used for the transmission frequency generation unit. Further, a frequency multiplication method may be used for the transmission frequency generation unit.

[Action]

In each of the slave wireless relay devices according to claim (1), the reference frequency signal transmitted from the reference signal transmitting means of the main wireless relay device is received, and the relay transmission frequency synchronized with the reference frequency signal is received. To generate. On the other hand, in the main wireless relay device, the relay transmission frequency is generated based on the reference frequency. Therefore, the relay transmission frequency from the slave wireless relay device and the relay transmission frequency in the main wireless relay device are both
Since they are based on the same reference frequency, when the reference frequency fluctuates due to temperature, humidity, vibration, etc., they all fluctuate in the same manner, and no relative fluctuation occurs. That is, even if the relay transmission frequency of each wireless relay device varies, no mutual deviation occurs. In this way, beat interference due to frequency deviation does not occur at the wireless station. Since the frequency of the reference frequency signal is different from the relay transmission frequency, the reference frequency signal is used when the relay transmission frequency is in use to be transmitted from the wireless relay device to one of the wireless stations. Does not affect the relay transmission frequency. Further, in each of the wireless relay devices according to claim (2), since the relay synthesizer system is used to generate the relay transmission frequency in the transmission frequency generation unit, the relay of each wireless relay device is performed. Even if the transmission frequencies for use fluctuate, mutual deviation does not occur, so that beat interference due to frequency deviation does not occur at the wireless station. Further, in each of the wireless relay devices described in claim (3), the relay frequency is generated in the transmission frequency generation unit by using the frequency multiplication method. Even if the relay transmission frequency fluctuates, no mutual deviation occurs, so that beat interference due to frequency deviation does not occur at the wireless station.

【Example】

A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a wireless relay system according to the present invention, FIG. 2 is a block diagram of a master wireless relay device, and FIG. 3 is a block diagram of a slave wireless relay device. As shown in FIG. 1, FIG. 2, and FIG. 3, first, the main wireless relay device 1 installed in at least one place in a predetermined area is a radio wave from a wireless station.
A reception unit RX1 that receives F1 and a transmission unit TX1 that transmits the signal received by the reception unit RX1 to a wireless station as a relay radio wave F2.
And a reference frequency signal serving as a reference for the transmission frequency of all wireless relay devices is obtained from the reference frequency oscillator 4 of the transmitter TX1, and the radio wave F1 from the radio station and the relay radio wave F2 to the radio station are obtained.
And a reference frequency transmission unit TXR that transmits to each wireless relay device as a reference radio wave F3 having a different frequency. The transmission unit TX1 includes a reference frequency oscillator 4 that oscillates a reference frequency, a transmission frequency generation unit 11 that generates a relay transmission frequency that is synchronized with the reference frequency, and an amplifier 16. The slave wireless relay device 2 includes a receiver RX2 that receives a radio wave F1 from a wireless station, a transmitter TX2 that transmits the signal received by the receiver RX2 to the wireless station as a relay radio wave F2, and the main wireless relay device 1 And a reference frequency receiving unit RXR that receives the reference radio wave F3 from the reference frequency transmitting unit TXR. The transmitter TX2 is a transmission frequency generator that generates a relay transmission frequency synchronized with the reference frequency obtained by the reference frequency receiver RXR.
21 and an amplifier 26. The transmission frequency generators 11 and 21 include voltage-controlled oscillators 14 and 24, low-pass filters 13 and 23, phase comparators 12 and 22, and a frequency divider 1.
Configure a phase-locked loop with 5, 25 as the main components,
A PLL synthesizer configured to generate a transmission frequency determined by a frequency divider in synchronization with a frequency input to a phase comparator. In the main wireless relay device 1, the signal input to the phase comparator 12 is the output of the reference frequency oscillator 4, and in the slave wireless relay device 2, the phase comparator 22.
The signal input to is the output of the reference frequency receiver RXR. The function of each unit will be described below with reference to FIGS. 1, 2, and 3. First, the function of the main wireless relay device 1 will be described. The radio wave F1 from the radio station 3A is input to the transmission unit TX1 when received by the reception unit RX1 of the main radio relay device 1. In the transmitter TX1, the output of the reference frequency generator 4 is input to the phase comparator 12 of the transmission frequency generator 11. The relay transmission frequency generated by the transmission frequency generation unit 11 and synchronized with the reference frequency is
It is amplified by the amplifier 16 and transmitted as a relay radio wave F2 to the radio station 3B. Separately from this, the output of the reference frequency oscillator 4 is also input to the reference frequency transmitter TXR, and the radio wave F from the radio station 3A is received.
The reference radio wave F3 having a frequency different from the relay radio wave F2 to 1 and the radio station 3B is always transmitted to all slave radio relay devices 2. Next, the function of the slave relay device 2 will be described. Radio station 3A
The radio wave F1 from is received by the receiving unit RX2 of the secondary wireless relay device 2 and is input to the transmitting unit TX2. Further, the reference radio wave F3 from the reference frequency transmitter TXR of the main wireless relay device 1 is always received by the reference frequency receiver RXR of the slave wireless relay device 2, and the reference frequency output from the reference frequency receiver RXR is Input to the transmitter TX2. The reference frequency is the transmitter T
The relay transmission frequency input to the phase comparator 22 of the transmission frequency generation unit 21 of X2 and generated by the transmission frequency generation unit 21 and synchronized with the reference frequency is amplified by the amplifier 26 and wirelessly transmitted as the relay radio wave F2. Sent to station 3B. That is, in the transmission frequency generation unit 21, the reference frequency obtained by the reference frequency reception unit RXR is used in the same manner as the oscillation output of the reference oscillator in the normal PLL synthesizer. By setting the reference frequency to a sufficiently high frequency, the accuracy of the frequency can be improved and the C / N of the PLL synthesizer in the transmission frequency generation unit 21 can be improved. Further, as described in claim (2), a PLL synthesizer system may be used in the transmission frequency generation unit. Further, as described in claim (3), a frequency multiplication method may be used in the transmission frequency generation unit. Further, the portion for extracting the reference frequency signal input to the reference frequency transmission unit TXR of the main wireless relay device 1 from the transmission unit TX1 is
Transmission frequency generation section 11, intermediate section of transmission section TX1, or transmission section T
Any of the final part of X1 may be used. In this case, frequency multiplication processing on the side of the reference frequency transmission unit TXR becomes easy. It is also possible to configure the reference frequency with a plurality of frequencies and divide the wireless relay device into a plurality of groups. In this case, a large number of wireless stations can be divided into a plurality of groups to facilitate communication between wireless stations. Further, the reference frequency signal may be transmitted to each slave radio relay device by the telecommunication circuit equipment. In this case, the reference radio wave F3 is unnecessary, and more effective use of the frequency is possible.

【The invention's effect】

The present invention sends a radio wave having a reference frequency for controlling a relay transmission frequency transmitted from each wireless relay device to a wireless station from a main wireless relay device, which is one of the wireless relay devices installed at a plurality of locations. As a result, the deviation of the transmission frequency for relay from each wireless relay device to the wireless station can be made the same condition, and the occurrence of beat interference due to this can be prevented, while the wireless station attempts to use it. Since it is not necessary to have a function of switching the frequency according to the wireless relay device and the switching operation is not required, it is possible to easily receive in the best condition, and the device as a whole is simple and economical. There is an advantage. In addition, since the same frequency can be used for transmission from each wireless relay device to a predetermined wireless station, there is an advantage that frequencies used can be easily allocated to other wireless relay devices and wireless stations, and effective use of frequencies can be achieved. . Further, by setting the frequency of the reference frequency signal transmitted from the main wireless relay device to a frequency different from the relay transmission frequency transmitted from each wireless relay device to the wireless station,
Since the reference frequency signal can be transmitted even when the relay transmission frequency from any of the wireless relay devices to the wireless station is in use, the above effect can be stably obtained. Further, as in the present application, by transmitting the reference frequency at a frequency different from the relay transmission frequency, the reference frequency can be set to a high frequency, and the frequency management accuracy can be improved. Further, when the PLL synthesizer system is used for the transmission frequency generation unit, it is possible to obtain various relay transmission frequencies in a stable manner. Further, by using the frequency multiplication method in the transmission frequency generation unit, it is possible to obtain the effect that the relay transmission frequency can be obtained with a simple circuit.

[Brief description of drawings]

FIG. 1 is a system diagram of a wireless relay system according to the present invention, FIG. 2 is a block diagram of a master wireless relay device of the system, and FIG. 3 is a block diagram of a slave wireless relay device of the system. 1 ... Main wireless relay device, 2 ... Slave wireless relay device, 3A, 3B
...... Wireless station, 4 …… Reference frequency oscillator, 11,21 …… Transmission frequency generator, 12,22 …… Phase comparator, 13,23 …… Low pass filter, 14,24 …… Voltage controlled oscillator , 15, 25 …… Divider, 16, 26 …… Amplifier, RX1 …… Reception unit (main wireless relay device), TX1 …… Transmission unit (main wireless relay device), TXR …… Reference frequency transmission unit (main) Wireless relay device), RX2 ... Reception unit (slave wireless relay device), TX2 ... Transmission unit (slave wireless relay device), RXR ... Reference frequency receiving unit (slave wireless relay device), F
1 …… radio wave from radio station, F2 …… relay radio wave, F3 …… reference radio wave.

Claims (3)

[Claims] 1. A wireless relay system in which a main wireless relay device and a slave wireless relay device are installed at a plurality of locations for relaying between a plurality of wireless stations including a mobile wireless station, wherein the main wireless relay device. Includes a relay reception unit that receives a signal from a wireless station, a reference frequency generation unit that outputs a reference frequency, and a relay transmission frequency that is generated based on the reference frequency. A relay transmission unit that transmits a signal from the station, and a reference signal transmission unit that generates a reference frequency signal having a frequency different from the relay transmission frequency based on the reference frequency and transmits the reference frequency signal to another slave radio relay device. The sub-radio relay device includes a reference frequency receiving unit that receives the reference frequency signal, a transmission frequency generating unit that generates a relay transmission frequency synchronized with the reference frequency, and a wireless station. And a relay receiver that receives the signal from the wireless station, and a relay transmitter that transmits the signal from the wireless station received by the relay receiver at the relay transmission frequency. system. 2. The radio relay system according to claim 1, wherein the transmission frequency generation unit uses a PLL synthesizer system. 3. The wireless relay system according to claim 1, wherein the transmission frequency generation unit uses a frequency multiplication method.