JPH05252088A - Diversity transmission reception system - Google Patents

Abstract

PURPOSE:To build up the small size and economical system by tying a central base station A and a base station B with a 2-way optical transmission line via an orthogonal modulator and an orthogonal demodulator, allowing the station A to compare reception quality of the two antennas of the station B to select an antenna with excellent quality so as to make inter-communication with a mobile station. CONSTITUTION:The two signals received by antennas 19, 20 of a base station 2 are orthogonal-modulated by an orthogonal modulator 23, the result is converted into an optical signal by an electro-optic converter 24 and sent to a central base station 1 through an optical fiber 25. An optoelectric converter 26 of the station 1 converts the optical signal into an electric signal, an orthogonal demodulator 29 applies orthogonal demodulation and separation to the converted signal and demodulators 32, 33 and a discrimination device 34 discriminate the quality of the reception signal. The station 1 selects and uses an antenna with better quality in the antennas 19, 20 of the station 2 based on the result of discrimination and uses an orthogonal modulator 7, an electro-optic converter 11, a fiber 12, an optoelectric converter 13 and an orthogonal demodulator 14 or the like to make inter-communication with the mobile station. Thus, the small sized and economical system is built up.

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 particularly to a centralized base station having two antennas in the base station. This relates to a transmission / reception diversity system in which switching is performed in a station.

[0002]

2. Description of the Related Art Conventionally, diversity reception control is performed such that a radio signal received by two antennas is demodulated by different demodulators, the received signal quality of each antenna is compared, and an optimum demodulator output is selected. It's all done at the base station.

FIG. 3 is a diagram for explaining such a conventional diversity reception, in which 46 is a base station and 4 is a base station.
Reference numerals 7 and 48 are antennas, 49 and 50 are transmission / reception separators, 51 is a modulator, 52 and 58 are switches, 53 and 54 are receivers,
55 and 56 are demodulators, 57 is a level detector, and 59 and 60
Represents a mobile device.

In the figure, a mobile unit (59 or 6)
The radio wave from 0) is captured by the antennas 47 and 48, then input to the receivers 53 and 54 via the transmission / reception separators 49 and 50, and the outputs thereof are demodulated by the demodulators 55 and 56. The outputs of these demodulators are input to the switch 58, respectively.

On the other hand, the IF signals received by the receivers 53 and 54 and frequency-converted are respectively input to the level detector 57, and which system has a higher received level (carrier level) is checked. In response to this, a signal for controlling the switches 52 and 58 is output.

Based on this signal, the switch 58 selects and outputs the demodulation signal on the side of the higher reception level among the outputs of the demodulators 55 and 56. At this time, since the switch 52 also operates so as to select the antenna on the higher reception level side, the transmission signal input to the switch 52 via the modulator 51 is transmitted from the antenna on the higher reception level side to the mobile station. Sent out.

[0007]

In the conventional transmission / reception diversity system as described above, the base station controls diversity transmission / reception, so that the configuration of the base station becomes rather complicated.

On the other hand, if the number of base stations increases when the number of base stations increases in order to cope with the increase in the number of mobile terminals, it is necessary to downsize and simplify the base stations. In order to solve this problem, it is conceivable to adopt a transmission / reception diversity method in which the toll base station performs transmission / reception diversity control, and the antenna of the base station is selected by signal transfer between the base station and the toll base station. The most natural means for realizing this method is to use an electric / optical conversion circuit, an optical / electrical conversion circuit, and an optical transmission line for each diversity branch signal (branch signal).

However, in such a configuration, it is necessary to prepare an electric / optical conversion circuit, an optical / electrical conversion circuit, and an optical transmission line for the number of branch signals, so that a large amount of hardware is required, and for that reason, There was a problem that economic efficiency was impaired.

The present invention provides a pair of electrical / optical conversion circuits, an optical / optical conversion circuit.
It is an object of the present invention to provide a transmission / reception diversity system which can be realized with a simple configuration in which a base station and a centralized base station are connected by an electric conversion circuit and a single optical transmission line, and which is excellent in economic efficiency.

[0011]

SUMMARY OF THE INVENTION The present invention is a diversity transmission / reception system in which a base station uses two antennas in a mobile communication system in which a centralized base station and a mobile device are connected to each other through the base station to perform mutual communication. And a quadrature modulator that quadrature modulates the respective reception inputs from the two antenna systems, an electric / optical converter that receives the output of the quadrature modulator and converts it into an optical signal, and a centralized base station. An optical / electrical converter that converts an optical signal received from a station into an electrical signal, an orthogonal demodulator that receives the output of the optical / electrical converter and orthogonally demodulates it, and two outputs of the orthogonal demodulator, respectively. And a means for connecting to the two antenna systems, the centralized base station receiving an optical / electrical converter for converting an optical signal received from the base station into an electric signal, and an output of the optical / electrical converter. This is the baseband signal , And two demodulators for respectively demodulating the two outputs of the quadrature demodulator, and the signals of these two demodulators are compared to determine which of them has better reception quality. A first signal quality judgment device that makes a judgment and outputs a signal indicating the result, and a switching operation is performed according to the judgment result of the signal quality judgment device to select and output the demodulator output on the side with better reception quality. A switch, a modulator that modulates a signal to be transmitted, and a second switch that performs a switching operation according to the determination result of the signal quality determiner and connects the output of the modulator to one of two circuits, A quadrature modulator for quadrature modulating signals from the two circuits connected to the second switch; and an electrical / optical converter for receiving an output of the quadrature modulator and converting the signal into an optical signal, Power between base station and centralized base station / Between the optical converter and an optical / electrical converter is a diversity transceiving system formed by connecting an optical transmission path.

[0012]

According to the present invention, the two signals received by the two antennas in the base station are quadrature-modulated into one quadrature-modulated signal, which is then transmitted to the centralized base station by the electric / optical converter and one optical transmission line. It is transmitted, and the centralized base station transmits this
The electric signal is converted into an electric signal by using an electric converter and input to the quadrature demodulator, the signals are separated, the received signal quality from each antenna is compared, and the demodulation baseband from the optimum antenna is selected and output.

Further, the antenna selected at this time is selected as a transmitting antenna, the signal to be transmitted is subjected to electrical / optical conversion, and the signal is transmitted to the base station through one optical transmission line. The base station selects this. It operates to transmit toward the mobile station using the antenna on the remote side.

According to the present invention, since the centralized base station demodulates the radio signal and switches the antenna as described above, the base station does not require a demodulator, a signal quality judging unit and a switch. It is possible to reduce the size and simplification of the station. Further, by orthogonally modulating the two-branch signal between the centralized base station and the base station, it is possible to omit one optical fiber and a pair of electric / optical converters in the uplink and the downlink, respectively, which is extremely economical. A diversity transmission / reception system can be realized.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, showing a configuration in which signal transmission between a base station 2 and a centralized base station 1 in a mobile communication system is performed by optical fibers 12 and 25. ing.

In the figure, a base station 2 is an antenna 1 which forms a wireless transmission path with a mobile terminal in a wireless zone.
9, 20, transmission / reception separators 17 and 18 for separating transmission signals to and from mobile devices, amplifiers 21 and 22 for amplifying received signals, and quadrature modulation for quadrature modulation of output signals of amplifiers 21 and 22. 23, an electric / optical converter 24 for transmitting the received signal from the mobile terminal to the toll base station, and an optical / electric converter 13 for sending the optical signal transmitted from the toll base station to the mobile terminal. A quadrature demodulator 14 that demodulates a quadrature modulated signal from the toll base station, and amplifiers 15 and 16 that amplifies the output of the quadrature demodulator 14.

The toll base station 1 includes a switch 4 for inputting the output signal of the modulator 3, couplers 5, 6 for inputting the output signal of the switch 4, and a quadrature modulator 7 for inputting the output signals of the couplers 5, 6. , A mixer 8 for inputting the output signal of the quadrature modulator, a bandpass filter (BP for inputting the output signal of the mixer 8)
F) 10, an electric / optical converter 11 for converting the optical signal from the base station 2 into a radio signal by inputting the output signal of the BPF 10, an optical / electrical converter 26, an optical / electrical converter The mixer 27, which inputs the output signal of the mixer 26, the mixers 8 and 2
Signal oscillator 9 for supplying local signal to 7, mixer 27
Of the BPF 28, the quadrature demodulator 29 of which the output signal of the BPF 28 is input, the distributors 30 and 31 of which the two signals demodulated by the quadrature demodulator 29 are input, and the distributor 3
Demodulators 32, 3 for inputting output signals of 0, 31 respectively
3. Switch 3 for inputting output signals of demodulators 32 and 33
5. Input the output signals of the demodulators 32 and 33 to the switch 3
5 is provided with a determiner 34 for inputting an antenna selection signal.

In the base station 2, in the downlink, the radio signals from the mobile terminal received by the antennas 19 and 20 are input to the transmission / reception separators 17 and 18, respectively, and then to the amplifiers 21 and 22, respectively. The output signals of the amplifiers 21 and 22 are input to the quadrature modulator 23 and converted into quadrature modulated signals. The quadrature modulated signal is converted from a radio signal into an optical signal by the electro-optical converter 24 and transmitted to the toll base station 1 via the optical fiber 25. In the uplink, an optical signal transmitted from the base station 1 via the optical fiber 12 is input to the optical / electrical converter 13 and converted into a quadrature modulation signal. The quadrature modulation signal output from the optical / electrical converter 13 is separated and output into two branch signals by the quadrature demodulator 14. The two-branch signal is input to the amplifiers 15 and 16 and then to the antennas 19 and 20 via the transmission / reception separators 15 and 16, respectively.

In the toll base station 1, in the uplink,
The received signal from the mobile terminal via the base station 2 is converted into an electric signal by the optical / electrical converter 26, and then converted into an intermediate frequency by the mixer 27 and the signal oscillator 9. The BPF 28 blocks the local signal from the signal oscillator and the RF signal at the output of the optical / electrical converter.

The quadrature modulation signal output from the BPF 28 is input to the quadrature demodulator 29 and converted into the two branch signals, each branch signal is input to the distributors 30 and 31, and then to the demodulators 32 and 33. To be done. That is, the two branch signals from the antennas 19 and 20 are demodulated by the demodulators 32 and 33, respectively.

The demodulation signals from the demodulators 32 and 33 are input to the determiner 34, and the antenna with a high reception level is determined (or the baseband signals of the demodulators 32 and 33 are input, and the antenna with a low error rate is determined. Be done). Based on the result, one of the demodulators 32 and 33 is switched to the switch 35.
Is selected and output.

In the downlink, the transmission signal from the modulator 3 is selected by the switch 4 which performs a selection operation by the output of the judging device 34, and is input to either one of the couplers 5 and 6. The output is converted into a quadrature modulation signal by the quadrature modulator 7, frequency-converted by the mixer 8 and the signal oscillator 9, and input to the electric / optical converter 11 via the BPF 10. Then, the converted optical signal is transmitted to the base station 2 through the optical fiber 12.

FIG. 2 is a block diagram showing an example of the structure of the quadrature modulator / demodulator, in which (a) shows the structure of the quadrature modulator and (b) shows the structure of the quadrature demodulator. In the figure, the amplitude modulator 3
The output signal of 6 is the signal supplied from the signal oscillator 38,
Since the phase is delayed by π / 2 by the phase shifter 39, the output signal of the amplitude modulator 37 becomes a signal whose phase is delayed by π / 2, and these are combined by the coupler 40 and output as a quadrature modulation signal.

On the other hand, the quadrature modulation signal input to the combiner 41 is detected by the detectors 42 and 43. Since the output of the signal oscillator 44 of the detector 42 is delayed by π / 2 by the phase shifter 45, the detector 42 is detected. It is delayed by π / 2 from the detection signal of 43 and is output in the same phase as the output signal of the amplitude modulator 36.

[0025]

As described above, according to the present invention, in the diversity transmission / reception system, the centralized base station selects the reception signal from the mobile terminal and the selection of the transmission antenna to the mobile terminal. Therefore, the modulator / demodulator of the base station and the signal quality determiner are not required, so the base station can be downsized,
There is an advantage that simplification can be achieved.

Further, the two branch signals for diversity are subjected to quadrature modulation, so that one optical fiber and a pair of electric / optical converters, and a centralized base station and a base station are used in the upstream and the downstream respectively. Since it is possible to send and receive data between them, the amount of hardware is small, so it is also economical.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of the configuration of an orthogonal modulator / demodulator.

FIG. 3 is a diagram for explaining conventional diversity reception.

[Explanation of symbols]

 1 Centralized base station 2 Base station 3 Modulator 4 Transmission changeover switch 5, 6, 40, 45 Combiner 7, 23 Quadrature modulator 8, 27 Mixer 9, 38, 44 Signal oscillator 10, 28 BPF 11, 24 Electric / Optical converter 12,25 Optical fiber 13,26 Optical / electrical converter 14,29 Quadrature demodulator 15,16,21,22 Amplifier 17,18 Transmission / reception separator 19,20 Transmission / reception antenna 30,31 Distributor 32,33 Demodulation Device 34 Judgment device 35 Receiving changeover switch 36, 37 Amplitude modulator 39, 45 Phase converter 42, 43 Synchronous detector

Claims (1)

[Claims] 1. A mobile communication system in which a centralized base station and a mobile device are connected to each other through the base station to perform mutual communication, and the base station is a diversity transmission / reception system using two antennas. A quadrature modulator that quadrature modulates each reception input from one antenna system, an electro-optical converter that receives the output of the quadrature modulator and converts the output to an optical signal, and an optical signal received from a centralized base station. An optical / electrical converter for converting into an electric signal, an orthogonal demodulator for receiving the output of the optical / electrical converter for orthogonal demodulation, and two outputs of the orthogonal demodulator are respectively connected to two antenna systems. And an optical / electrical converter for converting an optical signal received from the base station into an electric signal, and an output of the optical / electrical converter for demodulation into a baseband signal. Orthogonal restoration A modulator, two demodulators that respectively demodulate the two outputs of the quadrature demodulator, and the signals of these two demodulators are compared to determine which of the reception qualities is good, and the result is obtained. A signal quality determiner that outputs a signal indicating the signal, a first switch that performs a switching operation according to the determination result of the signal quality determiner, selects and outputs the demodulator output on the side with better reception quality, and A modulator that modulates a signal; a second switch that performs a switching operation according to the determination result of the signal quality determination device to connect the output of the modulator to one of two circuits; and a second switch A base station and a centralized base station are provided with a quadrature modulator that quadrature modulates signals from two circuits connected to each other, and an electric / optical converter that receives an output of the quadrature modulator and converts the output to an optical signal. Electric / optical converter and light between each other Diversity reception scheme, characterized in that formed by connecting the electrical converter in the optical transmission path.