JPH05102894A - Diversity transmitting/receiving system - Google Patents

Abstract

PURPOSE:To provide the system to select the antenna of a base station while executing transmission/reception diversity control at a centralized base station by transferring signals between the centralized base station and the base station. CONSTITUTION:A base station 2 is equipped with electric/optical converters 17, 18 and optical/electric converters 11, 12 for transferring signals exchanged with a mobile equipment to a centralized base station 1. At the centralized base station 1, the signals received from the mobile equipment are inputted through the optical/electric converters 21, 22 to distributors 23, 24, distributed to demodulators 25, 26 corresponding to a desired frequency and demodulated. A level detector 27 decides a receiving route (antenna) at a higher level, and one demodulator is selected and outputted by a changeover switch 28 for reception. The signals transmitted from a modulator 3 are selected through a changeover switch 4 for transmission similarly and inputted to one of couplers 5, 6, and outputs are respectively converted to optical signals by electric/optical converters 7, 8 and afterwards transmitted to the base station 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for performing mutual communication between a mobile terminal and a centralized base station via a base station by a radio frequency signal, and more particularly to a plurality of antennas in the base station. The present invention relates to a transmission / reception diversity method when switching is performed by a centralized base station and the same frequency is used for transmission / reception.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing the structure of a conventional transmission / reception diversity system. In the figure, the base station 6
A voice baseband signal is input to the switch 0 from the switching station, converted to a radio signal by the modulator 66, and then transmitted from the antenna 61 or 62 to the mobile station 7 via the transmission changeover switch 65.
Radio waves are radiated to 3 or 74. Mobile unit 73 or 7
The received signal from 4 is sent to the demodulator 6 via the receivers 67 and 69.
8 and 70, the carrier level from the receiver is judged by the level detector 71, and the demodulator output with a high level is selected by the reception changeover switch 72.

Conventionally, the base station 60 has a plurality of antennas 6
Different demodulators 6 for the radio signals received at 1 and 62
After demodulating at 8 and 70 and comparing the level or error rate of the received signal of each antenna by the level detector 71, the diversity reception for selecting the optimum demodulator output has been performed by the base station 60.

[0004]

However, in the above-mentioned conventional method, the number of base stations increases when the wireless zone is reduced, so that it is necessary to downsize and simplify the base stations. However, there was a problem that this request was not met. Moreover, since only one frequency can be used at the same time, there is a problem when the traffic increases.

An object of the present invention is to efficiently allocate a plurality of frequencies to the same radio zone. Further, transmission / reception diversity control is performed by the centralized base station, and signals are transferred between the centralized base station and the centralized base station. It is an object to provide a transmission / reception diversity system that selects an antenna.

[0006]

A feature of the present invention is that a base station and a centralized base station are connected via an optical transmission line to perform mutual communication, and centralize radio signals received by a plurality of antennas in the base station. The signal is transmitted to the base station and the centralized base station compares the levels or error rates of the received signals from the respective antennas and outputs the demodulated baseband from the optimum antenna. Also,
It is characterized in that the same antenna as this is selected and transmitted as a transmitting antenna. Furthermore, after selecting the transmission antenna for each transmission signal with a different frequency, input the transmission signal to different couplers connected to the transmission antenna via the optical transmission line, and connect via multiple reception antenna optical transmission lines. The output of each of the different distributors is demodulated and switched. This makes it possible to multiplex radio channel signals of different frequencies to the combiner and distributor. Further, in order to reduce the number of electric / optical converters, the number of optical / electrical converters, and the number of optical fibers for transmitting between base stations, a plurality of received signals are frequency-converted to have different frequencies, and then the electric signal stage is used. By synthesizing, a transmission line between the centralized base station and the base station is constructed by one electric / optical converter and one optical / electrical converter.
This enables economical transmit / receive diversity.

[0007]

According to the present invention, a plurality of radio channels can be frequency-multiplexed in the centralized base station, and a plurality of radio channels having different frequencies can be simultaneously transmitted and received in one base station. Further, since the centralized base station demodulates the radio signal and switches the antenna, the demodulator and the error rate or signal level detector are not required in the base station, and the base station can be downsized and simplified.

Further, a plurality of transmission signals for diversity and a reception signal from the mobile station can be transmitted by frequency multiplexing between the centralized base stations, and one optical fiber and a pair of electric / electrical signals can be transmitted in multiple directions. Diversity transmission / reception can be performed by the optical converter.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a communication system according to a first embodiment of the present invention. This embodiment shows a base station 2 in a mobile communication system.
Signal transmission between the optical fiber 9 and the centralized base station 1
A configuration for transmitting 0, 19, and 20 will be described.

The base station 2 has an antenna 1 which forms a wireless transmission path with terminals of mobile units in a wireless zone (not shown).
5, 16, transmission / reception separators 13 and 14 for separating a transmission signal to a mobile device and a reception signal from the mobile device, an electric / optical converter 17 for transmitting a reception signal from the mobile device to a centralized base station,
18, and optical / electrical converters 11 and 12 for transmitting the optical signal transmitted from the centralized base station to the mobile device.
The transmission / reception separators 13 and 14 have built-in amplifiers.

In the centralized base station 1, the received signals from the mobile station via the base station 2 are converted into electric signals by the optical / electrical converters 21 and 22 and then input to the distributors 23 and 24. In the distributors 23 and 24, the frequency multiplexed signal is allocated to the demodulators 25 and 26 corresponding to the desired frequencies. Received signals from the antennas 15 and 16 are input to demodulators 25 and 26, respectively, and a transmitted signal from the mobile device is demodulated. The distributed carriers are input to the level detector 27, and a high-level reception path (antenna) is determined. Based on the result, either one of the demodulators 25 and 26 is selected and output by the reception changeover switch 28. The transmission signal from the modulator 3 is selected by the level detector 27 via the transmission changeover switch 4 and input to either one of the couplers 5 and 6. The outputs of the couplers 5 and 6 are electricity /
After being input to the optical converters 7 and 8 and converted into optical signals, they are transmitted to the base station 2 by the optical fibers 9 and 10.

FIG. 2 is a diagram showing the configuration of the communication system of the second embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in the conditions for switching the received signal and the transmitting antenna. Error rate of each path as error rate detector 2
9 differs in that it is detected.

FIG. 3 is a diagram showing a configuration of a communication system according to a third embodiment of the present invention. In this embodiment, signal transmission between the base station 2 and the centralized base station 1 in the mobile communication system is carried out by an optical fiber. The configuration for transmitting by 9 and 46 will be described.

The base station 2 has an antenna 1 which forms a wireless transmission path with a terminal of a mobile device in a wireless zone (not shown).
5, 16, transmission / reception separators 13 and 14 for separating a transmission signal to the mobile device and a reception signal from the mobile device, amplifiers 40 and 41 for amplifying the reception signal, and frequency multiplexing of respective reception signals by converting them. Frequency converters 42, 43 for
And a combiner 44, an electric / optical converter 45 for transmitting the received signal from the mobile unit to the toll base station, and an optical / electric converter 34 for sending the optical signal transmitted from the toll base station to the mobile unit. A divider 35 for separating the frequency-multiplexed signal from the toll base station, frequency converters 36, 37 and amplifiers 38, 39 for converting the diversity transmission signal frequency-converted by the toll base station into a radio frequency to the mobile station, Is equipped with.

In the centralized base station 1, the received signal from the mobile station via the base station 2 is converted into an electric signal by the optical / electrical converter 47 and then input to the distributor 48. In the distributor 48, the frequency-multiplexed signal is converted into a desired frequency by the frequency converters 49 and 50 and input to the demodulators 51 and 52. That is, the reception signals from the antennas 15 and 16 are input to the demodulators 51 and 52, respectively, and the transmission signals from the mobile device are demodulated. The distributed carriers are input to the determiner 53, and a high-level reception path (antenna) is determined. Alternatively, the baseband signals of the demodulators 51 and 52 are input and the error rates are compared. Based on the result, either one of the demodulators 51 and 52 is selected and output by the reception changeover switch 28. The transmission signal from the modulator 3 is selected by the determination unit 53 via the transmission changeover switch 4 and input to either one of the frequency converters 30 and 31. The output is passed through the combiner 32 to the electrical / optical converter 33.
Is input to the optical fiber 9 and converted into an optical signal, which is then transmitted to the base station 2 through the optical fiber 9.

FIG. 4 is a diagram showing the configuration of the communication system of the fourth embodiment of the present invention. This embodiment is different from the third embodiment shown in FIG. 3 in that frequency converters 30, 36, 42 ,. It is different in that 49 is unnecessary, and a plurality of signals for other diversity are frequency-converted and frequency-multiplexed.

[0017]

As described above, according to the present invention,
The centralized base station selects the reception signal from the mobile terminal and the transmission antenna for the mobile terminal, and the modulator / demodulator of the base station and the level detector or error rate detector are not required. It has the advantage that it can be simplified and simplified. Further, by providing the centralized base station with the combiner and the distributor, it is possible to simultaneously transmit and receive a plurality of radio channels having different frequencies in one base station. Further, a plurality of transmission signals or reception signals for diversity are converted into different frequencies and frequency-multiplexed to transmit / receive diversity between the centralized base station and the base station by one optical fiber and a pair of electric / optical converters. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional communication method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Centralized base station 2 Base station 3 Modulator 4 Change-over switch for transmission 5,6 Coupler 7,8,17,18,33,45 Electric / optical converter 9,10,19,20,46 Optical fiber 11,12 , 21, 22, 34, 47 Optical / electrical converter 23, 24 Distributor 25, 26, 51, 52 Demodulator 27 Level detector 28 Receiving changeover switch 29 Error rate detector 30, 31, 36, 37, 42 , 43, 49, 50 Frequency converter 32, 44 Combiner 35, 48 Distributor 38-41 Amplifier 53 Determiner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Ogasawara 1-1-6, Saiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. A communication system in which a toll base station and a mobile device are connected via a base station and perform mutual communication using the same frequency, wherein the toll base station and the base station are connected by an optical transmission line and a base is provided. In a diversity transmission / reception system using a plurality of antennas in a station, a transmission changeover switch for selecting a radio channel signal transmitted from the toll base station to a terminal of the mobile device, and a separate electrical switch for converting into an optical signal. / Optical converter,
Separate optical transmission lines for transmitting the optical signal to the base station,
The base station includes separate optical / electrical converters for converting the optical signal into an electric signal, and the base station receives the radio channel signals from the terminals of the mobile device with a plurality of antennas and amplifies them. The received signal is converted into an optical signal by different electric / optical converters, and the optical signal is transmitted to the toll base station through different optical transmission lines. At the toll base station, the optical signal is changed to different optical / optical signals. The electric signal is converted into an electric signal by an electric converter, the electric signal is demodulated into a baseband signal by different demodulators respectively, the reception level of the electric signal before demodulation is compared by a level detector, and the demodulation base having a high reception level is compared. A diversity transmission / reception system characterized in that a transmission antenna is selected by outputting a band signal and switching the transmission selector switch according to the level detector output. 2. In the centralized base station, demodulated baseband signals obtained by respective demodulators of a plurality of antenna reception signals transmitted via the base station are input to an error rate detector to detect the error rate. 2. The diversity transmission / reception system according to claim 1, wherein the demodulated baseband signal is output by a converter. 3. A communication system in which a toll base station and a mobile device are connected to each other via a base station to perform mutual communication, wherein the toll base station and the base station are connected by an optical transmission line and a plurality of antennas are provided at the base station. In the diversity transmission / reception method using, a transmission changeover switch for selecting a radio channel signal transmitted from the toll base station to the terminal of the mobile device, and a frequency converter for converting each output signal into a different frequency. An electric / optical converter for converting the optical signal to an optical signal, an optical transmission line for transmitting the optical signal to a base station, an optical / electric converter for converting the optical signal to an electric signal in the base station, and the frequency being different. And a frequency converter for converting a transmission signal to the same radio frequency, wherein the base station receives the radio channel signal from the mobile terminal by a plurality of antennas, and the amplified reception signals have different frequencies. And converting the plurality of frequency-converted received signals into an optical signal by an electric / optical converter, and transmitting the optical signal to a toll base station through an optical transmission line. After being converted into an electric signal by an optical / electrical converter, it is distributed to the plurality of received signals, each received signal is converted into the same intermediate frequency, and the electric signals are demodulated into baseband signals by different demodulators. , Comparing the reception levels of the respective electric signals before demodulation with a determiner, outputting the demodulated baseband signal having a high reception level, and selecting the transmission antenna by switching the transmission changeover switch with the output of the determiner. A diversity transmission / reception system characterized by the following. 4. The demodulated baseband signal is obtained by comparing the demodulated baseband signals obtained by the demodulators of the reception signals of a plurality of antennas transmitted via the base station, in the toll base station, and comparing the error rates by the determination. The diversity transmission / reception system according to claim 3, wherein a signal is selected. 5. One of the received signals from the plurality of antennas and one of the plurality of signals transmitted from the centralized base station to the base station are directly transmitted without frequency conversion. The diversity transmission / reception system according to claim 3.