JPH08191478A - Optical network and radio base station - Google Patents

Abstract

PURPOSE: To attain inter-communication of a radio signal between a central station and a radio base station or between arbitrary radio stations. CONSTITUTION: Radio base stations 10a, 10b, 10c are cascade-connected by an optical fiber transmission loop line 3 using a central station 100 as a start point and an end point. The radio base station 10b sends radio signals 201a to 201c among radio signals 201a to 201c and 202c obtained by receiving an input signal light 5c to a radio terminal equipment 200b. Furthermore, the radio signal 202b sent from the radio terminal equipment 200b is received by the radio base station 10b and combined with the radio signals 201a to 201c and 202c and converted into the signal light 5b and it is sent to the radio base station 10a. A filter 140 of the central station 100 extracts only the radio signals 202a to 202c among the radio signals obtained by receiving the input signal light 5a and a frequency conversion circuit 134 converts the signals into the radio signals 201a to 201c and they are given to a transmission light source 125, from which the signals are sent to the radio base stations 10a, 10b, 10c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical network for wireless signal transmission using a subcarrier multiplex optical transmission system.

[0002]

2. Description of the Related Art In recent years, optical transmission technology is being applied to wireless systems such as mobile communication systems and wireless local area networks (wireless LANs). In a mobile communication system such as a car phone or a personal handy phone system (PHS), a service area is divided into a plurality of wireless areas, and each wireless area has a wireless base station that exchanges wireless signals with mobile terminals in the area. Placed respectively. Conventionally, in addition to transmission and reception of radio signals, this radio base station also performs modulation and demodulation and control of radio channels. However, in recent years, there have been growing demands for downsizing, cost reduction, low power consumption, and improvement of flexibility for wireless base stations, so an optical fiber feeder method for transmitting a wireless signal between a wireless base station and a central station by an optical fiber feeder system. Is attracting attention.

In this system, a plurality of radio base stations and a central station are connected by an optical fiber, and radio signals are transmitted as they are, whereby functions such as modulation / demodulation and control of radio channels are integrated in the central station. Is. According to this optical fiber feeder method, the wireless base station only needs to convert the optical signal and the electric signal and amplify the wireless signal, so that it can be dramatically reduced in size and weight and highly reliable. Such an optical fiber feeder method is, for example, "Wireless signal collection and delivery method for optical microcell mobile communication" by Shibuya et al.
Institute of Electronics, Information and Communication Engineers, Study Group on Wireless Communication Systems, RCS9
It is described in detail in documents such as 0-12.

On the other hand, the demand for the wireless LAN is rapidly increasing mainly for office use, and it is required to increase the speed, increase the capacity and increase the frequency. Therefore, there is a demand for an optical network that transmits wireless signals between rooms, floors, and buildings.

[0005]

In the personal communication system using the optical fiber link and the wireless link, a large number of mobile terminals can be accommodated by using the optical wavelength multiplexing technique and the microwave subcarrier system. For example, Proceedings of the 1990 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers B-736 (4-71)
Page) (1990) or JP-A-4-48832, an optical link wireless communication system is proposed. However, for example, when an optical fiber feeder for a mobile communication system is applied to eliminate a dead zone such as an underground mall or a tunnel, a plurality of radio base stations and a central station are connected to each other in order to reduce costs.
It is required to connect with a type 1 optical fiber network. However, in the uplink in this case, that is, in the optical transmission from the base station to the central station, signal lights from a plurality of base stations are multiplexed on the optical fiber network. For this reason,
It is necessary to manage the wavelength of each signal light so that beat noise due to interference between the signal lights is not generated, which makes the system extremely expensive. In addition, the system scale is limited due to the loss at the time of multiplexing / demultiplexing the signal light.

In an optical network for wireless LAN,
It is necessary to freely transmit wireless signals between wireless base stations installed in each room, each floor or each building. If this optical fiber feeder is composed of an N-to-N type optical fiber network, beat noise due to interference between signal lights becomes a big problem as in the above-mentioned mobile communication system application. Further wireless L
In the optical network for AN, the echo generated due to the bidirectional transmission of radio signals in each radio base station poses a serious problem. That is, the radio signal transmitted from one radio base station A to another radio base station B is transmitted from the radio base station B, re-received by the radio base station B at the same time, and sent back to the radio base station A again. It becomes an echo, and a large interference deterioration occurs. To date, little consideration has been given to optical networks that can avoid such echoes.

Therefore, an object of the present invention is to provide an N-to-1 type or N-to-N type low-cost optical network capable of collecting and delivering radio signals between a plurality of radio base stations and a central station or between a plurality of radio base stations. To provide. Another object of the present invention is to provide an optical network in which echo does not occur even when such a plurality of wireless base stations are bidirectionally connected.

[0008]

In the optical network of the first invention, a radio base station installed in a plurality of radio areas and a central station are connected by an optical fiber, and the radio base station transmits and receives. In an optical network in which radio signals are collected and delivered to a central office by optical fiber transmission, each radio base station includes an optical receiver for converting signal light input from an optical fiber transmission line into a high frequency signal, and a radio from the radio area. A radio receiving unit for receiving the signal, a multiplexer for multiplexing the radio signal received by the radio receiving unit and the output of the optical receiver,
An optical transmitter that modulates the intensity of signal light output to the optical fiber transmission line by the output from the multiplexer, and the wireless signal received by each of the wireless base stations has the central station as an end point and the wireless signal. It is characterized in that it is transmitted to the central office by an optical fiber transmission line connecting the base stations in cascade connection.

In the optical network of the second invention, the radio base stations installed in a plurality of radio areas and the central station are connected by an optical fiber, and the radio signals transmitted and received by the radio base station are transmitted by the optical fiber. In the optical network concentrated and delivered to the central office by each of the wireless base stations, each of the wireless base stations converts the signal light input from the optical fiber transmission line into a high frequency signal, and the output of the optical receiver to the wireless area. A wireless transmission unit for outputting, a wireless reception unit for receiving a wireless signal from a wireless area, a multiplexer for multiplexing the wireless signal received by the wireless reception unit and the output of the optical receiver, and the multiplexer. An optical transmitter that modulates the intensity of the signal light output to the optical fiber transmission line by the output from the wave device, and the wireless signals transmitted and received by each of the wireless base stations have a central station as a starting point and an end point. Each radio base Characterized in that transmitted by loop optical fiber transmission line cascading station.

In the optical network of the third invention, the radio base stations installed in a plurality of radio areas and the central station are connected by an optical fiber, and the radio signals transmitted and received by the radio base station are transmitted by the optical fiber. In the optical network where the wireless signals are received and received by each of the wireless base stations, the wireless signals are received from each wireless base station from the wireless base station to the central station by an optical fiber transmission line connecting the central station and the wireless base stations in a one-to-one relationship. The central station combines the outputs of the plurality of optical receivers that are transmitted and convert the signal light sent from each of the wireless base stations via the optical fiber transmission line into a high frequency signal. It is characterized by having a multiplexer.

In the optical network of the fourth aspect of the present invention, the radio base stations installed in a plurality of radio areas and the central station are connected by an optical fiber, and the radio signals transmitted and received by the radio base station are transmitted by the optical fiber. In the optical network concentrating and delivering to the central station, the radio signals concentrated and delivered to the respective radio base stations are frequency-converted in the central station.

In the optical network of the fifth invention, radio base stations installed in a plurality of radio areas are mutually connected by an optical fiber, and radio signals transmitted and received by the radio base stations are collected and delivered by optical fiber transmission. In the optical network described above, the radio signals collected and delivered to each radio base station are frequency-converted in the radio base station.

A radio base station according to a sixth aspect of the present invention is an optical receiver for converting an input signal light input to the radio base station through an optical fiber transmission line into a high frequency signal, and an output of the optical receiver for the radio base station. Of the signal light output to the optical fiber transmission line by the wireless signal received by the wireless receiving unit, the wireless transmitting unit that outputs to the wireless area covered by the wireless receiving unit, the wireless receiving unit that receives the wireless signal from the wireless area. It is characterized by comprising an optical transmitter that modulates the intensity.

A radio base station according to a seventh aspect of the invention is an optical receiver for converting an input signal light input to the radio base station through an optical fiber transmission line into a high frequency signal, and an amplifier for amplifying an output of the optical receiver. A wireless transmission unit that outputs to a wireless area covered by the base station, a wireless reception unit that receives a wireless signal from the wireless area, and a wireless signal received by the wireless reception unit and the output of the optical receiver are combined. It is characterized in that it is composed of a wave multiplexer and an optical transmitter that modulates the intensity of the signal light output to the optical fiber transmission line by the output from the wave multiplexer.

A radio base station of an eighth invention is a first and a second optical receiver for converting the first and second input signal lights inputted to the radio base station into first and second high frequency signals. A wireless transmission unit that combines a part of the first and second high-frequency signals and outputs the combined signals to a wireless area covered by the wireless base station; and a wireless reception unit that receives a wireless signal from the wireless area. A first multiplexer for multiplexing a part of the radio signal received by the radio receiving unit and a part of the first high frequency signal,
A first optical transmitter that modulates the intensity of the first output signal light output from the wireless base station by the output from the first multiplexer, and a wireless signal received by the wireless reception unit. Section, a second multiplexer for multiplexing a part of the second high-frequency signal, and the intensity of the second output signal light output from the radio base station by the output from the second multiplexer. It is characterized by comprising a second optical transmitter for modulating the.

A radio base station according to a ninth invention is the radio base station according to the sixth, seventh or eighth invention, wherein the radio signal received by the optical receiver and the radio signal received by the radio receiving unit. It is characterized by having a means for frequency converting either one or both of the above.

A radio base station according to a tenth aspect of the present invention is the sixth,
The wireless base station according to the seventh or eighth aspect of the invention is characterized by including means for removing the wireless signal transmitted from the wireless transmission unit from the wireless signal received by the wireless reception unit.

The radio base station of the eleventh invention is the sixth,
The wireless base station according to the seventh or eighth aspect of the invention is characterized in that it has means for limiting the amplitude of the wireless signal received by the wireless receiving section.

The optical network of the twelfth invention is characterized in that the plurality of radio base stations of the sixth or seventh invention are cascade-connected by a loop type optical fiber transmission line.

An optical network according to a thirteenth invention is the optical network according to the twelfth invention, wherein the radio base station includes a radio signal received by the radio reception unit among high frequency signals output from the optical receiver. It is characterized by having a means for removing the same frequency component.

An optical network according to a fourteenth invention is characterized in that, in the optical network according to the twelfth invention, the strength of the radio signal which has gone through the optical network for one round or more is smaller than the strength of the radio signal for the first round.

The optical network of the fifteenth invention is the optical network of the twelfth invention, wherein the radio signal transmitted from the radio base station is the first radio signal, and the radio signal received by the radio base station. Is a second radio signal, the frequency bands of the first radio signal and the second radio signal are different, and in the central station, the signal light input to the central station is received by an optical receiver, Of the first and second radio signals included in the output of the optical receiver, the first radio signal is removed by a filter, and the second radio signal is converted into the same frequency band as the first radio signal by the frequency converter. The frequency conversion is performed, and the signal light output from the central office is modulated by the frequency-converted second radio signal.

The optical network of the 16th aspect of the present invention is the optical fiber transmission of the 1st and 2nd loop type or bus type, wherein the plurality of radio base stations of the 8th aspect of the invention respectively have opposite transmission directions of signal light. An optical network characterized by being cascaded by a road.

The optical network of the seventeenth invention is the optical network of the twelfth or sixteenth invention,
Either one of the radio frequency signal output from the optical receiver of the radio base station and the radio signal received by the radio reception unit,
Alternatively, both are frequency-converted, and the frequency conversion amount at the time of this frequency conversion is equal in all the radio base stations of the optical network.

The optical network of the eighteenth invention is the optical network of the twelfth or sixteenth invention,
The radio frequency signal output from the optical receiver of the radio base station is frequency-converted to the radio frequency side by the frequency X (X is a positive or negative real number), and the radio signal received by the radio reception unit is frequency-X lower frequency side. It is characterized by frequency conversion to.

The optical network of the nineteenth invention is the optical network of the twelfth or sixteenth invention,
When the frequency of the radio signal transmitted from the radio transmission unit of the radio base station is X (X is a positive real number), and the frequency of the radio signal received by the radio base station is Y (Y is a positive real number). , A radio frequency signal output from the optical receiver of the radio base station is frequency-converted by Z-X + Y (Z is a positive or negative real number) to a radio frequency side, and the radio signal received by the radio reception unit is Z-X + Y only. The feature is that the frequency is converted to the low frequency side.

[0027]

In the optical network of the first aspect of the invention, each radio base station first converts the input signal light into a high frequency signal and then converts it again into a signal light for output. That is, each radio base station performs non-regenerative optical relay. The wireless base stations are cascaded by an optical fiber transmission line, and the wireless signal input to a certain wireless base station is multiplexed with the high frequency signal, and the wireless base station at the next stage sequentially repeats the optical signal to the central station. Is transmitted. In this case, one radio fiber transmission line is shared by each radio base station as an upstream line, but since only one signal light passes through the optical fiber transmission line, beat noise does not occur.

In the optical network of the second invention, the radio base stations are cascaded by a loop type optical fiber transmission line having a central station as a start point and an end point, and the radio signal input to the radio base station is the first one. Similarly to the invention, the optical signals are sequentially relayed and transmitted to the central station, and at the same time, the wireless signals output from the wireless base stations are sequentially optically relayed from the central station and transmitted to the respective wireless base stations. In this case, one radio fiber transmission line is shared by each radio base station as an uplink and a downlink, but since only one signal light passes through the optical fiber transmission line, beat noise does not occur.

Third Invention In an optical network, a plurality of radio base stations and a central station are connected by an optical fiber for the uplink.
The signal lights connected by the pair 1 are sent from the respective radio base stations, respectively, converted into high frequency signals by the optical receivers, and then multiplexed. In this case, since each signal light is individually received, beat noise is not generated, and the radio signal received by each radio base station can be processed by one radio processing system.

In the optical network of the fourth aspect of the present invention, since the radio signals collected and delivered to each radio base station are frequency-converted at the central station, echo due to bidirectional transmission does not occur.

In the optical network of the fifth aspect of the present invention, since the radio signals mutually transmitted between the radio base stations are frequency-converted in each radio base station, echo due to bidirectional transmission does not occur.

The radio base station of the sixth invention converts the input signal light into a radio signal and outputs it, and also converts the radio signal input into the radio base station into a signal light for transmission. Further, since the radio signal output from the radio base station is input again to the radio base station and converted into an optical signal, this radio base station has an optical relay function. Therefore, by connecting these in cascade, an optical network in which beat noise does not occur can be realized.

The radio base station of the seventh invention performs optical relaying, takes out a radio signal output from the radio base station at an electric stage, and multiplexes a radio signal input to the radio base station at the electric stage. To transmit. By cascading these wireless base stations, an optical network without beat noise can be realized.

A radio base station of the eighth invention is a duplication of the radio base station of the seventh invention. By cascade-connecting the wireless base stations with a double loop type or dual bus type optical fiber network, an optical network capable of exchanging wireless signals between arbitrary wireless base stations can be realized.

The radio base station of the ninth invention frequency-converts either or both of the radio signal received by the optical receiver and transmitted from the radio base station and the radio signal received by the radio receiver. Therefore, since the transmission and reception radio signals can be separated, no echo occurs in the optical network using this radio base station.

The radio base station of the tenth invention has a filter for removing the radio signal transmitted from the radio transmission section from the radio signal received by the radio reception section. Therefore, no echo occurs in the optical network using this wireless base station.

The radio base station of the eleventh invention has means for limiting the amplitude of the radio signal received by the radio receiving section.
Therefore, even if a very strong wireless signal is received by the wireless base station, other wireless signals that are optically relayed do not deteriorate due to this.

In the optical network of the twelfth invention, the radio base stations of the sixth or seventh invention are cascaded by a loop type optical fiber transmission line. As a result, it is possible to realize an optical network that enables bidirectional transmission and does not generate beat noise.

In the optical network of the thirteenth invention, the radio base stations of the seventh invention are cascaded by a loop type optical fiber transmission line, and in each radio base station, a high frequency signal output from an optical receiver is transmitted. The same frequency component as that of the radio signal received by the radio reception unit is removed by the filter. As a result, it is possible to prevent the wireless signal received by the wireless receiving unit from being optically relayed and circulating around the loop type optical fiber network.

In the optical network of the fourteenth invention, the radio base stations of the sixth or seventh invention are cascade-connected by a loop type optical fiber transmission line, and the wireless base station makes one or more rounds of the loop type optical fiber transmission line. The loop gain for the wireless signal is adjusted so that the signal strength becomes smaller than the wireless signal strength in the first round. As a result, it is possible to suppress the echo due to the radio signal that travels over the loop type optical fiber transmission path once or more to the allowable value or less.

In the optical network of the fifteenth invention, the central station for optical relay and the radio base station of the sixth or seventh invention are cascade-connected by a loop type optical fiber transmission line.
At the central office, out of the uplink and downlink radio signals input to the central office, the downlink radio signals are removed by a filter, the uplink radio signals are frequency-converted and converted to downlink radio signals, and the Output from the station. That is, the uplink and downlink radio signals are once terminated at the central office. Therefore, it is possible to prevent the radio signal from circulating around the loop type optical fiber network.

In the optical network of the sixteenth invention, the radio base stations of the seventh invention are cascade-connected by a double loop type or dual bus type optical fiber transmission line in which signal light transmission directions are opposite to each other. Has been done. This allows wireless signals to be mutually transmitted between arbitrary wireless base stations.

In the optical network of the seventeenth aspect of the invention, in the twelfth or sixteenth aspect of the invention, the amount of frequency conversion at the time of performing frequency conversion in each radio base station is made equal in all radio base stations. Therefore, the control of the wireless channel becomes easy.

In the optical network of the eighteenth invention, in the twelfth or sixteenth invention, the amount of frequency conversion at the time of frequency conversion in each radio base station is made equal in the uplink and the downlink. Therefore, the frequency conversion circuits for the uplink and the downlink can be partially shared.

In the optical network of the nineteenth invention, in the twelfth or sixteenth invention, the frequency conversion amount for the uplink and downlink when performing frequency conversion in each radio base station is set to The frequencies of the intermediate frequency signals are set to be equal.

[0046]

The present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an optical network according to the first embodiment of the present invention. In FIG. 1, wireless areas 1a, 1b, 1
Radio base stations 10a, 10b, and 10c are installed in the respective c, and these are bus-type optical fiber transmission lines 3 and 4.
Central station 1 that performs modulation and demodulation of radio signals and line control by
00 is connected. In the present embodiment, the transmission (downlink) from the central station to the radio base station is performed by demultiplexing the signal light from the central station at each radio base station and receiving them respectively. In addition, the transmission from the wireless base station to the central station (uplink) is performed by non-regenerative repeating of the signal light at each wireless base station, that is, at each wireless base station, the signal light from the preceding wireless base station is converted into an electrical signal. After conversion, it is converted into signal light again and transmitted to the next-stage radio base station.

It is now assumed that the mobile terminal 2 is in the wireless area 1b. In the wireless base station 10b in the wireless area 1b, a part of the signal light 105 sent from the central station 100 via the optical fiber transmission line 3 is demultiplexed by the optical demultiplexer 11b and converted into the wireless signal 101 by the optical receiver 13b. To be converted. The radio signal 101 is amplified by the amplifier 17b and transmitted from the antenna 19b. In addition, the signal light 6c sent from the wireless base station 10c through the optical fiber transmission line 4 is the optical receiver 1
At 4b, it is converted into a high frequency signal 22b and input to the multiplexer 24b. Further, the radio signal 102 sent from the mobile terminal 2 is received by the antenna 20b, amplified by the amplifier 18b, and then input to the multiplexer 24b. Radio signal 1
02 and the high-frequency signal 22b are multiplexed by the multiplexer 24b, input to the optical transmitter 26b, and intensity-modulate the signal light 6b sent to the wireless base station 10a by the optical fiber transmission line 4. The radio base station 10a has the same configuration as the radio base station 10b. The radio base station 10c is obtained by removing the function of demultiplexing the signal light for the downlink from the radio base station 10b and the function of the optical relay for the uplink.

In the central station 100, the optical receiver 113 receives the signal light 6a sent from the wireless base station 10a through the optical fiber transmission line 4, and the wireless signal 102 is output from the optical receiver 113. The radio signal 102 is converted into a baseband signal 154 by the demodulator 151 and input to the exchange 150. Further, the baseband signal 153 output from the exchange 150 is converted into the radio signal 101 by the modulator 155, input to the optical transmitter 125, and intensity-modulates the signal light 105. This embodiment can be used as a system for dealing with dead areas such as underground shopping malls and tunnels in car phones. In this case, the frequency band of the downlink radio signal 101 is 810 MHz to 830 MHz, and the frequency band of the uplink radio signal 102 is 940 MHz to 960 MH.
z. In this embodiment, the optical non-regenerative repeater system is used for the upstream line, and beat noise, which is a big problem in the conventional system for multiplexing signal light on an optical fiber transmission line, does not occur. Therefore, it is not necessary to manage the wavelength of the signal light, and the system cost can be significantly reduced as compared with the conventional method.

FIG. 2 shows the configuration of an optical network according to the second embodiment of the present invention. In this embodiment, the wireless base stations 10a to 10c are cascade-connected by the loop type optical fiber network 3 having the central station 100 as a start point and an end point, and wireless signals are transmitted by an optical non-regenerative repeater system on both the up and down lines. .

In the radio base station 10b, the signal light 5c sent from the preceding radio base station 10c through the optical fiber transmission line 3 is received by the optical receiver 13b and converted into the high frequency signal 21b. The high frequency signal 21b is partially demultiplexed by the demultiplexer 27b, amplified by the amplifier 17b, and input to the duplexer 29b. The duplexer is a combination of a low pass filter and a high pass filter.
It is widely used in wireless systems to share transmitting and receiving antennas. High frequency signal 21b
Contains a radio signal 101 (frequency band: 810 MHz to 830 MHz) sent from the central station 100, and only this radio signal 101 passes through the duplexer 29b and is transmitted from the antenna 19b. In addition, the wireless signal 102 (frequency band: 940
(MHz to 960 MHz) is received by the antenna 19b, passes through the duplexer 29b, and is amplified by the amplifier 18b. The radio signal 102 and the high frequency signal 21b are combined by the multiplexer 2
After being multiplexed by 3b, the signal light 5b input to the optical transmitter 25b and sent to the next-stage radio base station 10a is intensity-modulated.

FIG. 3 shows the configuration of a radio base station according to the third embodiment of the present invention. The overall configuration of the optical network is the same as that of the second embodiment shown in FIG. In this embodiment, the radio signal 101 obtained by receiving the signal light 5c is transmitted from the antenna 19b as it is without being demultiplexed. This wireless signal 101 is a wireless signal 102 from the mobile terminal 2.
At the same time, it is received by the antenna 20b. Antenna 20b
The radio signals 101 and 102 received in 1 are converted into the signal light 5b and sent to the next-stage radio base station 10a. According to this embodiment, each radio base station can have a very simple structure.

FIG. 4 shows the configuration of a radio base station according to the fourth embodiment of the present invention. The overall configuration of the optical network is the same as that of the second embodiment shown in FIG. In this embodiment, frequency conversion of radio signals and amplitude limitation of received radio signals are performed in each radio base station.

In the radio base station 10b of FIG. 4, the optical receiver 13b outputs an intermediate frequency signal 31 having a frequency band of 110 MHz to 130 MHz, which is sent from the central station. This intermediate frequency signal 31 has a part of the demultiplexer 2
The signal is demultiplexed by 7b and input to the frequency conversion circuit 33b.
Here, the intermediate frequency signal 31 is frequency-converted by 700 MHz to the high frequency side, and the frequency band is 810 MHz to 830 MH.
It becomes the radio signal 101 of z and is transmitted from the antenna 19b. Also, the radio signal 102 received by the antenna 20b
Has a frequency band of 940 MHz to 960 MHz, and the frequency conversion circuit 34b frequency-converts 700 MHz to the low frequency side, and the frequency band is 240 MHz to 260 MH.
It is converted into the intermediate frequency signal 32 which is z. The intermediate frequency signal 32 is combined with the intermediate frequency signal 31 by the combiner 23b and modulates the intensity of the signal light 5b sent to the next-stage radio base station. As described above, in the present embodiment, since the radio signal is frequency-converted into an intermediate frequency signal having a low frequency and is optically transmitted,
Low cost optical transmitters and receivers can be used. Since the frequency conversion amounts of the frequency conversion circuits 33b and 34b are the same 700 MHz, it is possible to share the local oscillator and the like used for them.

Further, in the present embodiment, the amplitude of the radio signal 102 received by the antenna 20b is limited by the limiter 35b so that its amplitude does not exceed a certain value. For example, when the mobile terminal 2 is located in the immediate vicinity of the antenna 20b, the reception strength of the radio signal 102 becomes very strong,
Amplifier 18b, frequency conversion circuit 34b, transmission light source 25b
There is a risk that distortion will occur. However, in the present embodiment, the limiter 33b limits the amplitude of the received wireless signal, so that the occurrence of distortion can be suppressed. In addition to using the limiter, it is of course possible to use an amplifier or the like having an automatic gain control function.

FIG. 5 shows the configuration of an optical network according to the fifth embodiment of the present invention. According to the optical network of this embodiment, wireless signals can be mutually exchanged between the wireless base stations, which is applied to a wireless LAN or the like.

As shown in FIG. 5, the radio base station 10
a, 10b, and 10c are connected in cascade by a loop type optical fiber transmission line 3, and wireless areas 1a, 1b, and 1 are connected.
c are mobile terminals 200a, 200b, 200c, respectively.
Exists. The frequency of the radio signal was in the 2.5 GHz band.

The radio base station of this embodiment, like the radio base station of the second embodiment, performs non-regenerative repeating of signal light and multiplexing / demultiplexing of radio signals. By this optical network, for example, a radio signal 201b transmitted from the mobile terminal 200b
Is transmitted to the mobile terminals 200a and 200c via the radio base stations 10b, 10a and 10c in order. In this way, in this embodiment, it is possible to communicate between arbitrary mobile terminals.

In the loop type optical network without termination as in this embodiment, there is a possibility that deterioration due to circulation of the radio signal may occur. For example, the radio signal 201b received by the radio base station 10b returns to the radio base station 10b again via the radio base stations 10a and 10c, is transmitted from the antenna 19b, and interferes with the original radio signal 201b as an echo. Therefore, in this embodiment, the loop gain of the optical network for radio signals is suppressed to 1 or less. That is, the strength of the circulated wireless signal is 20d more than that of the wireless signal 201b.
The loss of the optical fiber transmission line and the gain of the amplifier 37b of the radio base station are adjusted so as to be smaller than B. As a result, the interference due to the circulating signal is suppressed below the allowable value.

FIG. 6 shows the configuration of a radio base station according to the sixth embodiment of the present invention. The overall configuration of the optical network is the same as that of the fifth embodiment shown in FIG. In this embodiment, each radio base station performs radio signal drop / insert to avoid radio signal circulation. That is, a unique frequency band is assigned to each wireless area, and each mobile terminal transmits a wireless signal at the frequency assigned to the wireless area in which it is located. For example, 2 in the wireless area 1b
The frequency band of 545 MHz to 2550 MHz is assigned, and the mobile terminal 200b in this wireless area has 25
It transmits a radio signal of 45 MHz to 2550 MHz. The stop band of the wireless base station 10b is 2545 MHz to 2
It has a band elimination filter 39b of 550 MHz, and thereby removes the radio signal 201b which has gone around the optical network from the high frequency signal 21b output from the optical receiver 13b. Other radio base stations in the optical network also have such bandstop filters, which prevent radio signal loops.

FIG. 7 shows the configuration of an optical network according to the seventh embodiment of the present invention. In the present embodiment, the wireless base stations 10a-
10c and the central station 100 are connected in series by a loop type optical fiber transmission line 3, and the frequency conversion at the central station avoids the circulation of radio signals.

In the radio base station 10b of FIG. 7, from the optical receiver 13b, radio signals 201a to 201c (frequency band: 2410 MHz to 24) sent from the central station 100 are transmitted.
30 MHz) and a radio signal 202c (frequency band: 2540 MHz to 2) transmitted from the radio base station 10c in the preceding stage.
560 MHz) is output. Of these, the wireless signal 201
The signals a to 201c pass through the low pass filter 39b having a cutoff frequency of 2500 MHz and are transmitted from the antenna 19b. On the other hand, the radio signal 202c is blocked by the low pass filter 39b and is not transmitted from the antenna 19b.

The radio signal 202b transmitted from the radio terminal 200b (frequency band: 2540 MHz to 2560 MH)
z) is received by the antenna 20b and has a cutoff frequency of 25.
After passing through the high pass filter 40b of 00 MHz, it is input to the multiplexer 23b. Further, in the antenna 20b, the radio signals 201a to 201 transmitted from the antenna 19b are transmitted.
c is also received but is blocked by the high pass filter 40b. The optical transmitter 25b has wireless signals 201a-2
01c, 202b, 202c are input, and the signal light 5b is modulated by these radio signals. Radio base station 10
a and 10c have the same configuration as the wireless base station 10b.

On the other hand, in the central office 100, the optical receiver 1
From 13, wireless signals 201a to 201c sent from the central station 100 and having gone around the optical network, and wireless signals 202a to 202c from the respective wireless terminals are output. Of these, only the radio signals 202a to 202c pass through the high-pass filter 140 having a cutoff frequency of 2500 MHz and are input to the frequency conversion circuit 134. Radio signal 20
2a to 202c are set to 13 by the frequency conversion circuit 134.
The frequency of 0MHz is converted to the low frequency side, and the radio signal 20
1a to 201c. These wireless signals 201a to 201
c is input to the transmission light source 125, and the wireless base stations 10a to 10a.
10c is transmitted. As described above, in this embodiment, the central station centrally frequency-converts the radio signals, so that the radio signals circulating in the optical network can be removed.

FIG. 8 shows the configuration of an optical network according to the eighth embodiment of the present invention. In this embodiment, the wireless base stations 10a to 10d are connected in cascade by the dual bus type optical fiber transmission lines 3 and 4. In FIG. 8, the optical fiber transmission line 3 transmits the signal light in the left direction, and the optical fiber transmission line 4 transmits in the right direction.

In the wireless base station 10b, the wireless terminal 20
The radio signal 202b transmitted from the antenna 0b is transmitted to the antenna 20
The signal is received at b and is converted into the intermediate frequency signal 31b by the frequency conversion circuit 34b. Radio signal 2 in this embodiment
The frequency band of 02b is 2540 MHz to 2560 MHz,
The frequency band of the intermediate frequency signal is 140 MHz to 160 MHz
And the frequency conversion circuit 34b changes the frequency of the input signal to 2
Only 400 MHz is converted to the low frequency side. The signal light 5c sent from the wireless base station 10c is the optical receiver 13b.
The light is received by and is converted into intermediate frequency signals 31c and 31d. Further, the signal light 6a sent from the wireless base station 10a is received by the optical receiver 14b and converted into the intermediate frequency signal 31a.

These intermediate frequency signals 31a to 31d are
The multiplexers 23b, 24b, 43b, and the demultiplexer 27b,
The signals are combined and demultiplexed at 28b and 41b. Finally, the intermediate frequency signals 31a to 31d are input to the frequency conversion circuit 33b,
The radio signals 201a to 201d are converted into the antenna 19
It is transmitted from b. Radio signal 201a in the present embodiment
The frequency band of ~ 201d is 2410MHz ~ 2430MH
z, the frequency conversion circuit 33b converts the frequency of the input signal by 2270 MHz to the high frequency side. The intermediate frequency signals 31a and 31b are input to the transmission light source 26b and modulate the signal light 6b sent to the wireless base station 10c. Further, the intermediate frequency signals 31b to 31d are input to the transmission light source 25b and modulate the signal light 5b sent to the wireless base station 10a.

The configuration of the radio base station 10c is the same as that of the radio base station 10b, and the radio base stations 10a and 10d are also provided.
Indicates that the function of optical relay is omitted from the above-described radio base station 10b. By using the optical network as described above, wireless signals can be exchanged between arbitrary wireless terminals.

When a wireless signal is bidirectionally transmitted as in this embodiment, an echo may occur. For example, the radio signal 202a received by the radio base station 10a is transmitted from the radio base station 10b through the optical fiber transmission line 4, but when it is received again by the radio base station 10b, the optical fiber transmission line 3 is transmitted. And returns to the radio base station 10a, and interferes with the original radio signal 202a as an echo. For this reason, in this embodiment, the uplink and downlink frequency bands are made different to prevent re-reception of radio signals at each radio base station. That is, the antenna 20b includes the antenna 19b in addition to the wireless signal 202b from the wireless terminal 200b.
Although the wireless signals 201a to 201c transmitted from the wireless communication system are also input, these wireless signals 201a to 201c are blocked by the high pass filter 40b. Therefore, in this embodiment, no echo is generated even though the wireless signal is bidirectionally transmitted.

FIG. 9 shows the configuration of an optical network according to the ninth embodiment of the present invention. In this embodiment, a double loop type optical fiber transmission line 3 having the central office 100 as a starting point and an ending point,
4, the wireless base stations 10a to 10c are connected in cascade.

In FIG. 9, the optical fiber transmission line 3 transmits the signal light in the clockwise direction, and the optical fiber transmission line 4 transmits the signal light in the counterclockwise direction. The configurations of the radio base stations 10a to 10c are the same as those of the radio base station of the eighth embodiment. Central station 1
In 00, the wireless base station 10 is connected by the optical fiber transmission line 3.
The signal light 5a sent from a is received by the optical receiver 113. From the optical receiver 113, the wireless base station 10
Intermediate frequency signals 31a to 31 sent from a to 10c
c is output. Similarly, from the optical receiver 114, the intermediate frequency signal 31a sent by the optical fiber transmission line 4 is transmitted.
~ 31c is output. The switch 162 inputs one of the outputs of the optical receivers 113 and 114 to the demodulator 151. The intermediate frequency signals 31a to 31c are demodulated by the demodulator 15
1 is converted into baseband signals 154a to 154c, respectively, and is input to the exchange 150. This exchange 150
Is connected to an external public line. Also the exchange 150
The baseband signal 153 output from the modulator 155
Is converted into an intermediate frequency signal 131 by the switch 16
It is input to either of the optical receivers 125 and 126 via 1. The intermediate frequency signal 131 passes through either of the optical fiber transmission lines 3 and 4 and the radio base stations 10a to 10c.
To the wireless signal 101 and then transmitted. The optical network of the present embodiment enables communication between arbitrary wireless terminals, and at the same time enables the wireless terminals to be connected to the public line through the exchange 150 of the central office 100.

FIG. 10 shows the configuration of an optical network according to the tenth embodiment of the present invention. In this embodiment, the optical network of the seventh embodiment is used as the sub optical network, and these are connected by a dual bus type optical fiber network.

The sub optical networks 300a-3 of FIG.
The radio base station 10 at 00c has the same configuration as the radio base station of the seventh embodiment. The central offices 100a to 100c, which are the starting point and the ending point of these sub optical networks,
The optical fiber transmission line 7 for transmitting the signal light in the left direction and the optical fiber transmission line 8 for transmitting the signal light in the right direction are connected in cascade. In addition, the sub optical networks 300a to 30
0c to the wireless terminals 200a-
200c exists, and the frequency band of each wireless terminal is 2410M
Radio signals 201a-201 that are Hz-2430MHz
c is received and the frequency band is 2540 MHz to 2560 MH
The wireless signals 201a to 201c of z are transmitted.

In the central office 100b, the optical signal 171 from the optical receiver 171 which receives the signal light transmitted from the sub optical network 300b is transmitted to the wireless signal 20 from the wireless terminal 200b.
2b and the wireless signals 201a to 201c that have gone around the sub optical network 300b are output. Of these, only the radio signal 202b passes through the high-pass filter 140 having a cutoff frequency of 2500 MHz and passes through the frequency conversion circuit 134.
And is converted into a wireless signal 201b. Further, from the optical receivers 113b and 114b, respectively, the central office 100
wireless signals 201c, 20 sent from
1a is output. These wireless signals 201a, 201
b and 201c are multiplexers 123b, 124b, and 143.
b and the demultiplexers 127b, 128b, and 141b perform demultiplexing. Finally, the radio signals 201a to 201c are sent to the sub optical network 300b, and the central office 100a
To the wireless signals 201b, 2 through the optical fiber transmission line 7.
01c is transmitted, and wireless signals 201a and 201b are transmitted to the central office 100c through the optical fiber transmission line 8.

As described above, in this embodiment, it is possible to perform communication between arbitrary wireless terminals within the sub optical network or between the sub optical networks. In addition, since the central station converts the frequency of the radio signal in the same manner as in the seventh embodiment, the radio signal does not circulate within the sub optical network or between the sub optical networks.

FIG. 11 shows the configuration of an optical network according to the 11th embodiment of the present invention. In the present embodiment, the radio signals received by the respective radio base stations are aggregated in the central station through the individual optical fiber transmission lines, and the frequencies are collectively converted here.

The radio base station 10b receives the received radio signal 2
02b (frequency band: 2540 MHz to 2560 MHz)
The signal light 6b is intensity-modulated by and is transmitted to the central office 100 through the optical fiber transmission line 4b. Further, the signal light 5b sent from the central office via the optical fiber transmission line 4b is received by the optical receiver 13b, and from there, the radio signal 2b is transmitted.
01a to 201c (frequency band: 2410 MHz to 243)
0 MHz) is output and transmitted from the antenna 19b. The wireless signals 201a to 201c are transmitted to the antenna 2
0b but is blocked by the high pass filter 40b having a cutoff frequency of 2500 MHz,
It will not be sent back to 00.

The central station 100 is composed of radio base stations 100a-1.
The signal lights 6a to 6c individually sent from 00c are received by the optical receivers 113a to 113c, respectively, and the obtained radio signals 202a to 202c are multiplexed by the multiplexer 123. The combined radio signals 202a to 202c are converted into radio signals 201a to 201c by the frequency conversion circuit 134, input to the optical transmitters 125a to 125c, and transmitted to the radio base stations 10a to 10c.

FIG. 12 shows the configuration of an optical network according to the twelfth embodiment of the present invention. This embodiment has almost the same configuration as that of the eleventh embodiment, except that the signal light from each radio base station is multiplexed on the optical fiber transmission line by the optical multiplexer 171 and the signal light from the central station is optically converted. The difference is that the demultiplexer 173 demultiplexes on the optical fiber transmission line. This saves optical fiber and simplifies the central office configuration. However, in this embodiment, it is necessary to use transmission light sources having different wavelengths from each other in order to prevent beat noise when the signal lights are multiplexed.

[0080]

As described above, according to the present invention, it is possible to realize an optical network capable of exchanging wireless signals between a central station and mobile terminals, wireless terminals or between arbitrary wireless terminals.

[Brief description of drawings]

FIG. 1 is a configuration of an optical network according to a first embodiment of the present invention.

FIG. 2 is a configuration of an optical network according to a second embodiment of the present invention.

FIG. 3 is a configuration of a radio base station according to a third embodiment of the present invention.

FIG. 4 is a configuration of a radio base station according to a fourth embodiment of the present invention.

FIG. 5 is a configuration of an optical network according to a fifth embodiment of the present invention.

FIG. 6 is a configuration of a wireless base station according to a sixth embodiment of the present invention.

FIG. 7 is a configuration of an optical network according to a seventh embodiment of the present invention.

FIG. 8 is a configuration of an optical network according to an eighth embodiment of the present invention.

FIG. 9 is a configuration of an optical network according to a ninth embodiment of the present invention.

FIG. 10 is a configuration of an optical network according to a tenth embodiment of the present invention.

FIG. 11 is a configuration of an optical network according to an eleventh embodiment of the present invention.

FIG. 12 is a configuration of an optical network according to a twelfth embodiment of the present invention.

[Explanation of symbols]

1a-1c Wireless area 2 Mobile terminal 3, 4, 7, 8 Optical fiber 5a-5d, 6a-6c, 105, 106 Signal light 10, 10a-10d Wireless base station 11b, 173 Optical demultiplexer 13b, 14b, 113 , 113b, 114, 114b
Optical receiver 17b, 18b, 37b Amplifier 19a-19d, 20a-20d Antenna 21b, 22b High frequency signal 23b, 24b, 43b, 123, 123b, 124,
124b, 143b multiplexer 25b, 26b, 125, 125b, 126, 126b
Optical transmitters 27b, 28b, 41b, 127, 127b, 128,
128b, 141b demultiplexer 29b Duplexer 31, 31a to 31d, 131, 32, 32a to 32d
IF signal 33b, 34b, 134 Frequency conversion 35b Limiter 39b, 40b, 140 Filter 100, 100a-100c Central station 101, 102, 201a-201d, 202a-20
2d wireless signal 150 switch 151 demodulator 153, 154, 154a to 154c BB signal 155 modulator 161 and 162 switch 171 optical multiplexer 200a to 200d wireless terminal 300a to 300c sub optical network

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04B 10/20 10/02 H04B 9/00 NU

Claims (19)

[Claims] 1. A radio base station installed in a plurality of radio areas and a central station are connected by an optical fiber, and radio signals transmitted and received by the radio base station are collected and delivered to the central station by optical fiber transmission. In the optical network, each wireless base station includes an optical receiver that converts the signal light input from the optical fiber transmission line into a high frequency signal, a wireless receiving unit that receives a wireless signal from the wireless area, and the wireless receiving unit. A multiplexer that multiplexes the radio signal received by the receiver and the output of the optical receiver, and an optical transmitter that modulates the intensity of the signal light output to the optical fiber transmission line by the output from the multiplexer. An optical network, wherein the wireless signal received by each of the wireless base stations is transmitted to the central station via an optical fiber transmission line that connects the wireless base stations in cascade with the central station as an end point. 2. A radio base station installed in a plurality of radio areas and a central station are connected by an optical fiber, and radio signals transmitted and received by the radio base station are collected and delivered to the central station by optical fiber transmission. In the optical network, each of the wireless base stations, an optical receiver that converts the signal light input from the optical fiber transmission line into a high frequency signal, and a wireless transmission unit that outputs the output of the optical receiver to the wireless area, A radio receiving unit for receiving a radio signal from a radio area, a multiplexer for multiplexing the radio signal received by the radio receiving unit and the output of the optical receiver, and an optical device by the output from the multiplexer. The wireless base station has an optical transmitter that modulates the intensity of signal light output to the fiber transmission line, and the wireless signals transmitted and received by each of the wireless base stations are connected in cascade with the central station as the starting point and the ending point. Loop type optical fiber An optical network characterized by being transmitted by a fiber transmission line. 3. A radio base station installed in a plurality of radio areas and a central station are connected by an optical fiber, and radio signals transmitted and received by the radio base station are collected and delivered to the central station by optical fiber transmission. In the optical network, the radio signal received by each of the radio base stations is transmitted from the radio base station to the central station by an optical fiber transmission line connecting the central station and the radio base stations in a one-to-one correspondence. ,
A plurality of optical receivers for converting the signal light sent from each of the wireless base stations through the optical fiber transmission path into a high frequency signal; and a multiplexer for multiplexing the outputs of the plurality of optical receivers. Characteristic optical network. 4. A radio base station installed in a plurality of radio areas and a central station are connected by an optical fiber, and radio signals transmitted and received by the radio base station are collected and delivered to the central station by optical fiber transmission. In the optical network, the radio signal collected and delivered to each of the radio base stations is frequency-converted in the central station. 5. An optical network in which wireless base stations installed in a plurality of wireless areas are mutually connected by an optical fiber, and wireless signals transmitted and received by the wireless base stations are collected and delivered by optical fiber transmission, An optical network in which radio signals collected and delivered to each radio base station are frequency-converted in the radio base station. 6. An optical receiver for converting an input signal light input to a wireless base station by an optical fiber transmission line into a high frequency signal, and an output of the optical receiver is output to a wireless area covered by the wireless base station. From a wireless transmitter, a wireless receiver that receives a wireless signal from the wireless area, and an optical transmitter that modulates the intensity of the signal light output to the optical fiber transmission line by the wireless signal received by the wireless receiver. A radio base station characterized by being configured. 7. An optical receiver for converting an input signal light input to a wireless base station by an optical fiber transmission line into a high frequency signal, and an output of the optical receiver for amplifying the output to a wireless area covered by the wireless base station. A wireless transmission unit for outputting, a wireless reception unit for receiving a wireless signal from the wireless area, a multiplexer for multiplexing the wireless signal received by the wireless reception unit and the output of the optical receiver, A radio base station comprising an optical transmitter that modulates the intensity of signal light output to an optical fiber transmission line by the output from a multiplexer. 8. A first and second optical receiver for converting first and second input signal lights input to a radio base station into first and second high frequency signals, and the first and second optical receivers. Of a high frequency signal of the wireless base station and outputs it to a wireless area covered by the wireless base station, a wireless receiving section that receives a wireless signal from the wireless area, and a wireless receiving section that receives the wireless signal from the wireless area. A part of the radio signal and a part of the first high-frequency signal, and a first multiplexer output from the radio base station by an output from the first multiplexer. A first optical transmitter that modulates the intensity of the output signal light; a second multiplexer that multiplexes a part of the wireless signal received by the wireless receiving unit and a part of the second high-frequency signal. , Modulating the intensity of the second output signal light output from the radio base station by the output from the second multiplexer Radio base station, characterized in that they are composed of an optical transmitter. 9. One of a radio signal received by the optical receiver and a radio signal received by the radio receiver,
Alternatively, the radio base station according to claim 6 or claim 7 or claim 8 further comprising means for frequency converting both of them. 10. The method according to claim 6, further comprising means for removing the radio signal transmitted from the radio transmission unit from the radio signal received by the radio reception unit.
Alternatively, the wireless base station according to claim 8. 11. The apparatus according to claim 6, further comprising means for limiting an amplitude of a radio signal received by the radio receiving unit.
Alternatively, the wireless base station according to claim 7 or claim 8. 12. An optical network in which a plurality of radio base stations according to claim 6 or 7 are cascade-connected by a loop type optical fiber transmission line. 13. The radio base station includes means for removing the same frequency component as the radio signal received by the radio reception unit from the high frequency signal output from the optical receiver. Optical network described. 14. The optical network according to claim 12, wherein the strength of the wireless signal transmitted through the optical network for one round or more is smaller than the strength of the wireless signal for the first round. 15. When the radio signal transmitted from the radio base station is a first radio signal and the radio signal received by the radio base station is a second radio signal, the first radio signal and the first radio signal The frequency bands of the two wireless signals are different, and in the central office, the signal light input to the central office is received by the optical receiver, and the first and second wireless signals included in the output of the optical receiver. A first radio signal is removed by a filter, a second radio signal is frequency-converted by a frequency converter into the same frequency band as the first radio signal, and the central portion is converted by the frequency-converted second radio signal. 13. The optical network according to claim 12, wherein the optical signal output from the station is modulated. 16. A plurality of radio base stations according to claim 8 are cascade-connected by first and second loop-type or bus-type optical fiber transmission lines whose signal light transmission directions are opposite to each other. Characteristic optical network. 17. The radio base station performs frequency conversion on one or both of a high frequency signal output from an optical receiver and a radio signal received by a radio reception unit, and frequency conversion is performed at the time of this frequency conversion. Optical network according to claim 12 or 16, characterized in that the quantity is equal in all radio base stations of the optical network. 18. A radio frequency signal output from an optical receiver of the radio base station is frequency-converted to a radio frequency side by a frequency X (X is a positive or negative real number), and the radio signal received by the radio reception unit is converted into a frequency. 17. The optical network according to claim 12 or 16, wherein frequency conversion is performed by X to a low frequency side. 19. A frequency of a radio signal transmitted from a radio transmission unit of the radio base station is X (X is a positive real number), and a frequency of a radio signal received by the radio base station is Y (Y is a positive number). Real number), the high frequency signal output from the optical receiver of the radio base station is frequency-converted by Z−X + Y (Z is a positive or negative real number) to the high frequency side, and the radio signal received by the radio receiving unit is obtained. 17. The optical network according to claim 12 or 16, wherein the frequency conversion is performed by Z-X + Y to the low frequency side.