JPH06253355A - Radio communication system - Google Patents

Abstract

PURPOSE:To provide a communication system capable of easily moving a service area and extending the system, etc., without lowering throughput and to provide the small-sized inexpensive communication system with improved reliability which cart utilize an allocated frequency at most and is strong againt noise by constituting the communication system without using wire transmission lines. CONSTITUTION:Repeater stations (a) and (b) distributed and installed in places visible from a central station 10 are provided with a function for transmitting and receiving optical signals with the central station 10. Also, the repeater station (a) is provided with the function for performing radio communication with mobile terminal stations A and B inside the service area of the present station by using radio waves and the repeater (b) is provided with the function for performing the radio communication with the mobile terminal station C inside the service area of the present station by using the radio waves as well. When the mobile terminal stations A and B inside the same area communicate with each other, the radio communication is performed only with the radio waves. Also, when the mobile terminal station C inside the service area of the repeater station (b) communicates with the mobile terminal stations A and B inside the service area of the repeater station (a), the optical signals are transmitted through the central station 10 between the repeater stations (a) and (b).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system combining optical space transmission and radio transmission by radio waves, and is particularly suitable for a radio communication system with small electric power such as in-house radio.

[0002]

2. Description of the Related Art Conventionally, a wire communication system using a wire transmission path such as a twisted pair cable, a coaxial cable, or an optical fiber has been widely used. In such a wired communication system, when the layout is changed due to the move of the office, it is necessary to move the service area of the already constructed network or to expand the communication system, the central station and the terminal station are required. It was necessary to re-install equipment such as and rewire the wired transmission line. Recently, in order to reduce rewiring of a wired transmission path as much as possible, it has been proposed to combine both wired communication and wireless communication to configure a communication system.

FIG. 8 shows a conventional example of a communication system using wired communication and wireless communication. When the mobile terminal station A communicates with the mobile terminal station C in another service area, the relay station a
The signal wirelessly transmitted from the mobile terminal station A in the service area of the relay station a is received by the relay station a, and the relay station a receives the wired transmission line L.
The signal is transmitted to the central office 10 via a, and the signal is transmitted from the central office 10 to the relay station b to which the destination mobile terminal station C belongs via the wired transmission line Lb. The signal from the relay station b is wirelessly transmitted to the mobile terminal station C. In this system, the terminal stations A, B, C, etc. can be easily moved, but when the service area is moved or the system is expanded, the relay stations a, b
It is necessary to change the wirings of the wired transmission lines La and Lb that connect to each other, which requires construction, inspection, and the like, which is a large scale problem.

Next, in a wireless communication system that does not require a wired transmission path, it is necessary to dispose a radio device using radio waves between a central station and a relay station. There was such a problem. First, when the transmission frequency from the central station or relay station is low, it is necessary to enlarge the antenna and sharpen the directivity in order to avoid radio wave interference. Then, there is a problem that the antenna hinders downsizing of the device. On the contrary, if the transmission frequency is increased and microwaves or millimeter waves are used, electronic components corresponding to them become expensive, and as a result, the cost of the device becomes high. Besides,
It is vulnerable to electromagnetic noise, and since the allocated frequency is allocated to two sections between the central station and the relay station and between the relay station and the terminal station, there is a problem that the frequency cannot be effectively used.

Next, when the optical space transmission is used as the radio communication means instead of the radio wave, if the obstacle exists in the optical space transmission section, the communication cannot be performed. For example, when the wired transmission lines La and Lb between the central station 10 and the relay stations a and b in FIG. 8 are replaced with optical space transmission sections, lighting equipment and alarm devices,
If there are obstacles that block light, such as columns and beams,
There was a problem that the installation location of the relay station was limited. In addition, since the transmitted light must be received by the partner station at all times, there is a problem in installation that the transmission distance is limited and the mobile station cannot move freely.

Further, in the optical communication system disclosed in Japanese Patent Laid-Open No. 2-9240, all the data is sent to the central office, frequency conversion is performed at the central office, and then the data is sent to the relay station where the terminal station of the communication partner exists. Optical signals are transmitted for communication, and even when communicating between terminals within the same service area, communication can only be done via the central office, so the traffic within the central office increases and the throughput of the entire system increases. It had the drawback of falling.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to configure a communication system without using a wired transmission line to move a service area. , A flexible communication system that can easily expand the system without degrading throughput, small size, low cost, maximum use of allocated frequencies, noise-resistant and highly reliable communication system Is to realize.

[0008]

According to the present invention, in order to solve the above problems, as shown in FIG. 1, a central station 10 for transmitting and receiving a signal by optical space transmission, and a predetermined station from the central station. A plurality of relay stations a, which are distributed and arranged in well-spaced places spaced apart from each other and which transmit and receive signals by optical space transmission.
, and a plurality of mobile terminal stations A, B, C, ... Arranged in a service area by the radio waves of the plurality of relay stations, each mobile terminal station A, B, C ,. The relay stations a, b, ... Are configured to communicate with each other by using other mobile terminal stations within the area or other service area as communication partners, and the plurality of relay stations a, b, ... It is configured such that the signal is converted into a signal and transmitted to the central station 10 in the optical space, and the signal transmitted from the central station 10 in the optical space is converted into a radio signal and transmitted to the mobile terminal station. To do.

Here, the relay station retransmits data for a terminal station within the same service area without transmitting the received radio wave signal through the central station, and for terminal stations in other service areas, It is preferable that the optical signal is converted into an optical signal and transmitted. Further, in the optical space transmission section, it is preferable to provide a waveguide or a reflector for an optical signal in a section where an obstacle that blocks light exists.

[0010]

In the radio communication system of the present invention, the central station 10 and the relay stations a, b, ... Communicate by optical space transmission, and the relay stations a, b, ... And the terminal stations A, B, C ,. Since it communicates by radio waves, a communication system can be configured without using a wired transmission line such as a twisted pair cable, a coaxial cable, or an optical fiber, so construction is easy and inexpensive, and the service area can be moved or the system can be expanded. Wiring work associated with such situations is unnecessary, and a highly flexible communication system can be realized. On the other hand, the central station 10 and the relay stations a, b, ...
.. and the terminal stations A, B, C, ... In the case of communicating by optical space transmission between the relay stations a, b, .. However, it is necessary to secure a line-of-sight route of a highly mobile terminal station, and the usability as a mobile terminal station is significantly reduced. In the present invention, the communication between the relay stations a, b, ... And the terminal stations A, B, C, ... Is performed by radio waves, so that the terminal stations A, B, C ,. It will be good. Also, the system can be expanded simply by additionally installing a relay station in a place where the central station and the central station can see each other. Furthermore, by using the optical space transmission between the central station and the relay station, the frequency can be effectively used by maximizing the use of the radio channel for accommodating the mobile terminal station, compared with the case where the entire system is constructed by radio. In addition, the wireless channel between the relay station and the central station and the relay station
There is no problem of interference of radio channels between mobile terminal stations.

Further, the relay station retransmits the received radio wave signal for data to the terminals within the same service area without passing through the central station, and transmits the optical signal to the terminal stations in other service areas. Can be configured to be converted to and transmitted to reduce central office traffic,
The throughput of the communication system can be increased. Also, if there is an obstacle that blocks light in the optical space transmission section between the central station and the relay station, if a waveguide or reflector for optical signals is provided in that section, the installation location of the relay station It is possible to enhance flexibility with respect to layout changes, system expansion, etc.

[0012]

FIG. 1 shows the overall configuration of a wireless communication system according to the present invention. In the figure, reference numeral 1 denotes a central station, which has a function of transmitting and receiving signals by optical space transmission. The repeater stations a and b, which are distributed and arranged at locations that can be seen from the central station 10, have a function of transmitting and receiving optical signals to and from the central station 10. Further, the relay station a has a function of performing radio communication with the mobile terminal stations A and B in its own service area by using radio waves, and the relay station b also communicates with the mobile terminal station C in its own service area. It has a function to perform wireless communication using radio waves. Mobile terminal stations A and B within the service area of the relay station a
When communicating with each other, wireless communication is performed only by radio waves within the same service area without transmitting an optical signal to the central office 10. Further, when the mobile terminal station C in the service area of the relay station b communicates with the mobile terminal station A or B in the service area of the relay station a, an optical signal is transmitted between the repeaters a and b via the central station 10. Is transmitted.

FIG. 2 shows the internal structure of the mobile terminal station, relay station, and central station 10 used in the wireless communication system of the present invention. In the figure, 1 is a transmitting circuit, 2 is a receiving circuit, 3 is a switching circuit, 4 is an antenna, 5 is an O / E conversion circuit, and 6 is an E / O.
A converting circuit, 7 is a transmitting circuit, 8 is a receiving circuit, and 9 is a control circuit. When the mobile terminal station A communicates with the mobile terminal station C in another service area, the signal modulated by the transmission circuit 1 of the mobile terminal station A is transmitted from the antenna 4 of the mobile terminal station A via the switching circuit 3. It The data transmitted by the radio wave is received by the antenna 4 of the relay station a whose service area is the mobile terminal station A, and demodulated by the receiving circuit 2. The demodulated signal is electrically / optically converted by the E / O conversion circuit 6, and is optically spatially transmitted to the central office 10 as an optical signal.
The signal received by the central office 10 is optoelectrically converted by the O / E conversion circuit 5, the signal is amplified by the reception circuit 8, and the waveform is shaped. The signal received by the transmission / reception circuit 11a is input to the control circuit 9 to determine the data transmission destination, and the central station 10 corresponding to the relay station b to which the mobile terminal station C of the transmission destination belongs.
The data is transferred to the transmitting / receiving circuit 11b. The data transferred to the transmission / reception circuit 11b passes through the transmission circuit 7 and becomes E / O.
The conversion circuit 6 performs electric / optical conversion and optical space transmission to the relay station b. The signal received by the relay station b is the O / E conversion circuit 5
Is converted into light / electricity, modulated by the transmission circuit 1, and transmitted as a radio wave from the antenna 4 to the mobile terminal station C via the switching circuit 3. In the mobile terminal station C, the signal received by the antenna 4 is demodulated by the receiving circuit 2 via the switching circuit 3, the waveform is shaped, and the signal is taken in as a received signal.

FIG. 3 shows the configuration of the transmitting section of the terminal station of the present invention. In the terminal station, first, an ASK modulation block 21 for creating an ASK-modulated address frame.
A modulation block 22 for creating a PSK or QAM-modulated address and data frame, a timing block 23 for synthesizing the outputs of the blocks, and a transmission circuit for converting the output from the timing block into a high-frequency signal for transmission. Consists of. The structure of the transmission signal transmitted from this terminal station is shown in FIG. The transmission signal frame in FIG.
The address information frame is SK-modulated, the PSK-modulated or QAM-modulated address information frame, and the PSK-modulated or QAM-modulated data frame. In this way, the signal transmitted from the terminal station is composed of frames having different modulation schemes. Therefore, in the relay station, the amplitude-modulated address information in the data frame is converted into a baseband signal by using a simple detector without using a demodulator that has a complicated circuit configuration, and a filtering function is provided. As a result, the traffic passing through the central office can be reduced and the throughput can be improved. Although not shown in FIG. 4, it goes without saying that a preamble having a sufficient bit length is transmitted to the transmission signal prior to the transmission.

FIG. 5 shows the configuration of the receiving section of the relay station of the present invention. In the receiver of the relay station, the transmission signal shown in FIG. 4 transmitted from the terminal station is detected by the detector 31, and the address information is received from the ASK-modulated address information frame and converted into a baseband signal. Input to the determination circuit 32. The determination circuit 32 stores the received address information in the storage unit 3
By comparing with the information of the terminal station registered in No. 3, it is determined whether the received signal is for the terminal station in the same service area. In addition, a part of the received signal is delayed by the delay circuit 34.
And is input to the switch control unit 35 through. In this delay circuit 34, the switch controller 3 is connected to the input to the detector 31.
5 has the function of delaying the signal by the time required for switching. The output from the delay circuit 34 is switched by the switch controller 35 according to the control signal from the determination circuit 32, to the transmission circuit 36 for the terminal station in the same service area, and to the terminals in other service areas. Is input to the O / E converter 37 for light intensity modulation.

Normally, the central station 10 and the relay stations a, b, ...
For example, the mobile terminal stations A, B, C, ... on the desk are installed in places where there are no obstacles that block light in that section, such as a ceiling or a wall, and they are in line of sight. Install in an area with limited reach. Further, when there are obstacles such as lighting equipment, alarm devices, pillars and beams in the optical space transmission line between the central office 10 and the relay stations a, b, ..., As shown in FIG. An optical waveguide 41 may be provided immediately before 40 to avoid the obstacle 40, and then an optical signal may be transmitted to the partner station. In FIG. 6, when an obstacle 40 is present between the relay station a and the central station 10 when communicating from the mobile terminal station A to the mobile terminal station C in another service area, if the obstacle 40 exists in the service area of the relay station a. A radio signal wirelessly transmitted from the mobile terminal station A is received by the relay station a, converted into electric / optical by the relay station a, and the optical signal from the relay station a is transmitted to the central station 10 through the waveguide 41. As the waveguide 41, for example, an optical fiber can be used. Then, the optical signal received by the central station 10 is transmitted to the relay station b to which the destination mobile terminal station C belongs, is optically / electrically converted by the relay station b, and is wirelessly transmitted to the mobile terminal station c as a radio signal. . An optical signal amplifier circuit that amplifies the level of the received optical signal and performs optical space transmission may be added to the waveguide 41. Further, instead of the waveguide 41, as shown in FIG. 7, a reflector 42 is provided at a position where both the central station 10 and the relay station a can be seen, and the optical space transmission path is changed to transmit an optical signal to the other station. May be configured to be transmitted.

[0017]

According to the first aspect of the present invention, a network can be constructed without using a wired transmission path, so that construction is very easy, and an inexpensive and flexible network can be constructed. is there. Moreover, since the central station and the relay station use optical space transmission without using radio waves, these devices do not need an antenna and can be realized in a small size and at low cost.
In addition, no radio wave interference occurs between the channel between the mobile terminal station and the relay station and the channel between the relay station and the central station. Furthermore, the radio signals used by mobile terminal stations belonging to the service areas of different relay stations may have overlapping frequencies, so the radio channel for accommodating mobile terminal stations can be used to the maximum extent and the frequency can be used effectively. There is an effect that it can be used.

According to the second aspect of the invention, when the radio signal from the terminal station received by the relay station is data for the terminal stations within the same service area, the received radio signal is transmitted to the central station. Since I tried to retransmit without going through, the traffic of the central office did not increase,
The throughput of the communication system can be increased.

According to the third aspect of the invention, when there is an obstacle in the optical space transmission line between the central station and the relay station, it is possible to avoid it and perform optical communication. There is an effect that it is possible to configure a communication system that is highly flexible with respect to layout changes and system expansion without being restricted by the installation location of the relay station.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a block configuration diagram showing an internal configuration of each station in the present invention.

FIG. 3 is a block configuration diagram of a transmission unit in the mobile terminal station of the present invention.

FIG. 4 is a configuration diagram of a transmission signal frame from the mobile terminal station of the present invention.

FIG. 5 is a block diagram of a receiver of a relay station according to the present invention.

FIG. 6 is a configuration diagram of a wireless communication system using a waveguide according to the present invention.

FIG. 7 is a configuration diagram of a wireless communication system using a reflector according to the present invention.

FIG. 8 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 A, B, C Mobile terminal station a, b Relay station 10 Central station

Claims (3)

[Claims] 1. A central station that transmits and receives signals by optical space transmission, and a plurality of relay stations that are dispersed and arranged at a predetermined distance from the central station so that they can see and receive signals by optical space transmission. It comprises a plurality of mobile terminal stations arranged in a service area by radio waves of the plurality of relay stations, and each mobile terminal station mutually communicates with another mobile terminal station in the same service area or in another service area. The plurality of relay stations are configured to perform communication, and the plurality of relay stations convert a received radio signal from the mobile terminal station into an optical signal and perform optical space transmission to the central station, and a signal spatially transmitted from the central station. Is converted to a radio signal and transmitted to the mobile terminal station. 2. The relay station retransmits a received radio wave signal for data to a terminal within the same service area without passing through a central station, and transmits an optical signal to a terminal station in another service area. The wireless communication system according to claim 1, wherein the wireless communication system is configured to be converted into and transmitted. 3. The wireless communication system according to claim 1, wherein a waveguide or a reflector of an optical signal is provided in a section where an obstacle that blocks light exists in the optical space transmission section.