JPH04124919A - Radio base station antenna system, centralized base station, mobile communication equipment, and receiving state measuring instrument for mobile communication - Google Patents

Abstract

PURPOSE:To realize the miniaturization of a radio base station by concentrically handling the transmission.reception radio signals of scattered many base stations by using light transmission technique by utilizing the excellent low noise characteristic, low distortion characteristic and wide range characteristic of light beam type transmission. CONSTITUTION:Electricity/light conversion circuits 100, 200, 300, 400, 500, 600 convert the radio signal of every radio base station into a light signal. Transmitting optical fibers 1', 2', 3', 4', 5', 6' centralize the signal of every base station to a central station 9. Light/electricity conversion circuits 1000, 2000, 3000, 4000, 5000, 6000 return the radio signal converted into light to the signal of former frequency. A switching device 7 selects optional one of the light/ electricity converting devices, and supplies the output of it to a succeeding measuring instrument 8. The measuring instrument 8 is provided with a synthesizer, and is capable of switching the radio frequency to be measured. Accordingly, a receiving state measuring instrument for mobile communication can monitor the measuring state of different terminals by a time division system.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a small zone type mobile communication system.

(Prior Art) In a mobile communication system such as a car telephone system, a service area is divided into a plurality of zones, and a wireless base station is placed in each zone.

By doing so, it becomes possible to repeatedly use the same frequency between radio base stations where interference does not occur, and frequency resources can be used effectively. This method is called the small zone method.

The radio base station of a car telephone system consists of an antenna, an antenna sharing device, a transmitting/receiving device for communication and control, and a base station, as described in the Car Telephone published by the Institute of Electronics and Communication Engineers (edited by Moriji Kuwahara), page 252. It consists of a control device, etc.

(Problem to be solved by the invention) In a mobile communication system, frequency usage efficiency can be improved by dividing the service area into small zones, but in this case, wireless base stations are installed on streetlights or utility poles. That will happen. However, current wireless base stations include transmitting/receiving equipment and base station control equipment, and it is not always easy to achieve miniaturization and high reliability, which is an important issue when installing on streetlights and utility poles. there were.

Additionally, the number of base stations installed in each zone has been reduced from 1 to 1 in the past.
The number will be more than 00 times. Therefore, if these were to be handled in a distributed manner as before, there was a problem in that the control of radio channels would become extremely complicated.

The purpose of the present invention is to take advantage of the excellent low-noise, low-distortion, and wide-band characteristics of optical linear transmission to centrally handle transmitted and received radio signals from many dispersed base stations using optical transmission technology.
It is an object of the present invention to provide a mobile communication system that allows miniaturization of wireless base stations and centralized monitoring and control at a mobile telephone exchange.

(Means for Solving the Problems) (1) The present invention consists of an antenna that receives a radio signal from a mobile terminal, and an electrical/optical conversion circuit that exchanges the radio signal received by the antenna into an optical signal. This is a wireless base station antenna device characterized by:

The wireless base station antenna device further includes an optical/electrical conversion circuit that converts an optical signal sent from the exchange via the centralized base station into a wireless signal and outputs the signal to the antenna. It is.

The radio base station antenna device can be provided with an automatic gain control circuit that amplifies the radio signal received by the antenna to a certain output level and outputs it to the electrical/optical conversion circuit.

Further, the control signal of the automatic gain control circuit may be superimposed on the output signal of the automatic gain control circuit and input to the electrical/optical conversion circuit.

(2) The centralized base station of the present invention also includes an optical/electrical conversion circuit that converts an optical signal sent from a wireless base station antenna device via an optical fiber into the original wireless band signal; A demodulation circuit receives the radio band signal from the electrical conversion circuit and demodulates the call signal, a transmission circuit converts the call signal received from the exchange into a radio band signal, and the radio band signal from this transmission circuit is converted into an optical signal. and an electrical-to-optical conversion circuit that converts the signal and outputs it to the wireless base station antenna device via the optical fiber.

(3) Next, the mobile communication device of the present invention includes any of the radio base station antenna devices described in (1) above, the concentrated base station described in (2) above, and the wireless base station antenna device and the concentrated base station. (4) The reception condition measuring device for mobile communication of the present invention is characterized by comprising an optical fiber connecting the above (4)
2) It is characterized by having a base station control device that monitors each of the optical/electrical circuits or demodulation circuits of the centralized base station described above to grasp the reception status of all mobile terminals.

In addition, it is equipped with a switching device that selects any one of the optical/electrical circuit outputs of the centralized base station, and a measuring device that receives the output of this switching device and measures the reception status, and measures the reception status of signals from mobile terminals. This is a reception state measuring device for mobile communication characterized by measuring the reception state of a base station currently in communication and its neighboring base stations.

(Function) In the present invention, a high frequency signal received by a radio base station antenna is converted into an optical signal and transmitted to a mobile telephone exchange through a low-loss optical fiber. Therefore, the wireless base station antenna device can be downsized, and the number of parts can be reduced to improve reliability. However, with this alone, there is a problem that it is not necessarily easy to ensure the carrier-to-noise ratio (C/N) necessary for optical transmission when the level of the high-frequency signal received by the wireless base station is low. Therefore, in the present invention, by providing an automatic gain control circuit, the wireless signal received by the antenna is amplified to a constant output level, and a sufficient C/N is achieved.

The details will be explained next.

Here, it is assumed that five carriers are used in each wireless zone. When transmitting light by multiplexing five carrier waves and modulating a semiconductor laser, the total changes! , 1 index exceeds 100%, large distortion occurs due to overmodulation and sufficient characteristics cannot be obtained. Therefore, the modulation index per channel is usually suppressed to 20% or less at maximum. On the other hand, the C/N achieved during optical transmission is a modulation index of 20%.
It is about 80 dB at maximum. Here, as the modulation index decreases, the achieved C/N value also decreases by that amount. Generally, in mobile communication systems, there is a difference of 60 dB or more in signal levels received by radio base station antennas. Therefore,
The minimum signal level carrier is the required C/N, 15 dB.
may not be satisfied.

By the way, in normal usage conditions of a mobile communication system, traffic peaks do not occur very often, and furthermore, it is extremely rare that the reception level of each carrier is high.

Therefore, when the reception level of one carrier is low, the total modulation index of the semiconductor laser is often much smaller than 100%. Here, if the amplitude of the high frequency signal component that modulates the semiconductor laser is detected and its level is controlled so that the semiconductor laser is always modulated with a modulation index of almost 100%, even the carrier component with a low reception level will be significantly modulated. Since the signal is modulated by an index, a sufficient C/N can be achieved.

In such a system in which automatic gain control is applied in the optical transmitter, the C/N information etc. manually input to the control device housed in the mobile telephone exchange no longer directly reflects the actual wireless communication state. If the information regarding the automatic gain control control signal performed by each optical transmitter is simultaneously transmitted to the control device, the control device will be able to communicate wirelessly based on the reception state of the optical signal at the mobile telephone exchange and this control signal. It becomes possible to accurately grasp the communication status at

Furthermore, the following method can be considered to more accurately grasp the reception status of mobile communication. When a mobile terminal is communicating on a predetermined frequency (1) via a certain radio base station, not only the radio base station in use but also the radio that covers the zone adjacent to the zone covered by this radio base station. By monitoring the magnitude of the frequency f1 received by the base station, information on how the mobile terminal is moving can be obtained, and even when the mobile terminal moves between zones, it can be quickly captured.

In the mobile communication device of the present invention, a signal received by a wireless base station antenna device is transmitted as a wireless signal to a centralized base station via an optical fiber. Therefore, by switching the signals from each wireless base station gathered at a centralized base station and monitoring the same frequency signals, it is possible to know the reception status of one signal at different points, and the location of one mobile terminal can be known. You can learn more. By switching the frequency to be monitored here, the reception status of different mobile terminals can be monitored. In addition, when the number of mobile terminals covered by one centralized base station is large, by providing a plurality of monitoring devices, it becomes possible to grasp the reception status of all mobile terminals.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing a block diagram of an embodiment of the present invention. In the figure, 1.2.3.4.5.6 indicates each wireless zone. 10.20.30.40.50.60 are base station antennas provided corresponding to each wireless zone.

Also 100.200.300.400.500.600
is an electrical-to-optical conversion circuit that converts radio signals from each base station into optical signals. 1', 2', 3'', 4', 5', and 6' are transmission optical fibers for concentrating signals from each base station to the central station 9.

1000.2000.3000.4000.5000.
6000 is an optical-to-electrical conversion circuit that returns the optical radio signal to the original radio frequency signal.

7 is a switching device that selects any one of these converters and supplies its output to the next measuring device 8.

In this embodiment, the measuring instrument 8 has a synthesizer, and the radio frequency to be measured can be switched. Therefore, the reception state measuring device for mobile communication of this embodiment was able to monitor the measurement states of different mobile terminals in a time-division manner. Note that the measuring device 8 may be a receiving demodulator used as is, and the reception state may be measured based on the quality of the demodulated signal, or only the power of the received signal may be observed.

9 indicates a centralized base station.

In addition, in the embodiment shown in FIG. 1, only one fiber is drawn out from each wireless zone, but if each base station handles multiple wireless channels, one
It goes without saying that there will be a plurality of fibers such as ", 2', etc.".

Additionally, each radio zone is assigned a certain frequency repeating pattern (
It is also possible to consider this in relation to cell clusters). Furthermore, by providing a plurality of switching devices 7 and measuring devices 8, it is possible to increase the number of mobile terminals that can be monitored.

FIG. 2 is a diagram showing a second embodiment of the mobile communication device of the present invention. This mobile communication device includes a mobile terminal 11, wireless base stations 21 to 24, a centralized base station 91, and a mobile telephone switching center 5.
It consists of The mobile terminal 11 and the mobile telephone exchange 5 are similar to those commonly used, and their configurations are widely known to those in the industry and will not be described in detail here. Furthermore, in the embodiment shown in FIG. 2, a case will be explained in which there are four wireless base station antenna devices, but it is also possible to add more wireless base station antenna devices depending on conditions such as the range of the service area and traffic. .

In the wireless base station antenna device 21, the high frequency signal received by the antenna 20 is transmitted through a transmitting/receiving duplexer 203 and a receiving filter 2.
05. Through the reception amplifier 206, the signal is converted into an optical signal by the electric-to-optical conversion circuit 207 realized by a laser diode and its driver circuit, and transmitted to the common wireless transmitting/receiving device 400 via an optical fiber. In the centralized base station 91, first, optical-to-electrical conversion circuits 401 to 404 regenerate high frequency signals, and demodulation circuits 411 to 414 demodulate uplink communication signals and send them to the mobile telephone exchange 51. Downlink call signals from the car telephone exchange 51 are sent to the centralized base station 91
The signals are converted into high-frequency signals by transmitters 415 to 418 within, and then converted to optical signals by electrical-to-optical conversion circuits 405 to 408. The optical signal sent out by the centralized base station 91 is input to the optical/electrical conversion circuit 201 realized by the photodiode and front end circuit of the wireless base station antenna device 21, and is transmitted via the transmission amplifier 202 and the transmission/reception splitter 203. , is transmitted from the antenna 20. The other radio base station antenna devices 22 to 24 have similar configurations.

In the wireless antenna device 21 of this embodiment, the reception amplifier 206
is composed of a variable gain amplifier, whose output level is detected by a gain control circuit 208, and the output signal is used to control the gain of the receiving amplifier 206, thereby converting the electrical-to-optical conversion circuit 2.
The high frequency signal level input to the laser diode 07 was kept constant and its modulation index was always 95%. When this mobile communication system is actually operated, if the gain control of the receiving amplifier 206 is not performed, the centralized base station 9
1, the worst value of the C/H of the received signal was 15 dB, but by operating the gain control circuit 208 of this embodiment, the modulation index for each carrier increases on average, and the C/H
The worst value of N was also improved to 25 dB.

FIG. 3 is a diagram for explaining a third embodiment of the present invention. The basic configuration of the mobile communication system of this embodiment is the same as that of the second embodiment. Radio antenna device 21 of this embodiment
24, the output from the gain control circuit 208 is also sent to the electrical/optical conversion circuit 207, superimposed on a high frequency signal, and transmitted to the centralized base station 91. The centralized base station 91 sends the signal from the gain control circuit 208 to the base station controller 61 along with information regarding the received signal. Base station control device 6
1 can grasp the reception status of each mobile terminal 11 from these signals.

In fact, in this embodiment, due to the operation of the gain control circuit 208, the reception level of the received signal changed from moment to moment depending on the traffic condition at that time even if the received signal was received from the same place. By combining and determining the sent signals, the base station control device 61 was able to accurately grasp the location, etc. of each mobile terminal. By sending control signals based on this, the signal output of each mobile terminal 11 can be adjusted, and the dynamic range of the system can be substantially increased.

In the above embodiment, a case was described in which the gain control circuit 208 was installed in the radio base station antenna devices 21 to 24, but a similar gain control circuit could also be installed in front of the electrical/optical conversion circuit included in the centralized base station 91. It is also possible to do so. Furthermore, although the wireless antenna devices 21 to 24 and the centralized base station 91 are each connected by two optical fibers for transmission and reception, it is also possible to share the optical fibers by using optical wavelength multiplexing technology. Furthermore, it is also possible to arrange both those that include the gain control circuit 208 and those that do not include the gain control circuit 208, taking into account the size of the zone covered by each radio antenna device, traffic, the installation location of the radio antenna device, etc. .

(Effects of the Invention) According to the present invention, instead of monitoring received signals at each base station that originally exists separately, this function can be concentrated in a centralized station using optical fiber, and mobile devices moving between zones can can be captured efficiently.

Further, according to the present invention, by adding a gain control circuit to the radio base station antenna device, communication can be performed while maintaining a high C/N even when the radio reception signal level is low, and Since it is possible to centrally monitor the entire area and use this to perform various line controls, it is possible to provide a high-quality mobile communication system.

[Brief explanation of drawings]

1, 2 and 3 are diagrams showing an embodiment of the mobile communication device of the present invention. 11 is a mobile terminal, 21 to 24 are wireless base station antenna devices, 1.2.3.4.5.6 are each wireless zone 10.20.3
0.40.50.60 is a base station antenna corresponding to each wireless zone, 100.200.300.400.500.600 is an electrical/optical conversion circuit, 1000.2000.3000.4000.5000.
6000 is an optical/electrical conversion circuit, 7 is a switching device, 8 is a measuring device, 9.91 is a centralized base station, 51 is a mobile telephone exchange, 6
1 each indicates a base station controller.

Claims (8)

[Claims] (1) An antenna that receives wireless signals from a mobile terminal;
A wireless base station antenna device comprising an electrical/optical conversion circuit that converts a wireless signal received by the antenna into an optical signal. (2) The wireless base station antenna device according to claim 1, further comprising an optical/electrical conversion circuit that converts an optical signal sent from a switching center via a centralized base station into a wireless signal and outputs it to the antenna. A wireless base station antenna device characterized by: (3) The wireless base station antenna device according to claim 1 or 2, further comprising an automatic gain control circuit that amplifies the wireless signal received by the antenna to a certain output level and outputs the amplified signal to the electric/optical conversion circuit. (4) The radio base station antenna device according to claim 3, wherein the control signal of the automatic gain control circuit is superimposed on the output signal of the automatic gain control circuit and is input to the electrical/optical conversion circuit. Base station antenna equipment. (5) Optical /
An electrical conversion circuit, a demodulation circuit that receives a wireless band signal from this optical/electrical conversion circuit and demodulates a call signal, a transmitter circuit that converts the call signal received from the exchange into a wireless band signal, and from this transmitter circuit. converts wireless band signals into optical signals,
A centralized base station comprising: an electrical/optical conversion circuit that outputs to the wireless base station antenna device via the optical fiber. (6) Consisting of the wireless base station antenna device according to claim 2, 3 or 4, the concentrated base station according to claim 5, and an optical fiber connecting the wireless base station antenna device and the concentrated base station. A mobile communication device characterized by: (7) Mobile communication reception characterized by comprising a base station control device that monitors the output from each optical/electrical circuit or demodulation circuit of the centralized base station according to claim 5, and grasps the reception status of all mobile terminals. Condition measuring device. (8) A switching device for selecting any one of the optical/electrical circuit outputs of the centralized base station according to claim 5, and a measuring device for receiving the output of the switching device and measuring the reception state, A reception state measuring device for mobile communication, characterized in that the reception state of a signal is measured from the reception states of a base station currently in communication and its neighboring base stations.