JPH05252559A - Diversity transmission and reception system - Google Patents

Abstract

PURPOSE:To simplify the constitution of a base station at the time of operating a diversity control by a mobile communication. CONSTITUTION:Plural base stations 2 are equipped with a common centralized base station 1, and both of them are connected through optical fibers 11 and 26. Then, a local for a frequency conversion is transmitted with the same radio signal whose frequency is different to be transmitted from the centralized base station 1 to the base station 2, and the same signal from the base station 2 is converted into the same radio frequency by the local in the base station 2, and transmitted from an antenna 45 or 46. And also, at the time of frequency- converting the plural radio signals received by the plural antennas 45 and 46 at the base station 2, one received signal is frequency-converted by using the same local, and transmitted to the centralized base station 1. The switching of a signal accompanied with a signal modulation and demodulation, and a diversity control is operated at the centralized base station 1.

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 toll base station via a base station, and more particularly to a plurality of antennas in the toll base station. The present invention relates to a transmission / reception diversity system for switching.

[0002]

2. Description of the Related Art Conventionally, after demodulating radio signals received by a plurality of antennas in a base station by different demodulators and comparing the levels or error rates of the received signals of the respective antennas,
Diversity reception, which selects the optimum demodulator output, has all been done at the base station.

FIG. 2 is a block diagram showing a conventional embodiment. A voice baseband signal is input to the base station 47 from the exchange station, converted into a radio signal by the modulator 53, and then transmitted from the antenna 48 or 49 to the mobile unit 52 via the switch 52.
Radio waves are radiated to the. The received signal from the mobile device is the receiver 4
It is input to the demodulators 60 and 61 via 8, 49 and the carrier level from the receiver is judged by the level detector 54, and the switch 55 selects the demodulator output having a high level.

However, since the number of base stations increases when the wireless zone is reduced, it is necessary to downsize and simplify the base stations. However, when diversity control is performed by the base stations, there is a problem that this requirement cannot be satisfied. ..

[0005]

SUMMARY OF THE INVENTION According to the present invention, a plurality of diversity signals are frequency-multiplexed by frequency conversion and then transmitted to a centralized base station through a pair of electric / optical converters, optical / electrical converters and a single optical transmission line. However, it is an object of the present invention to provide a simple and economical base station by performing diversity control within the centralized base station.

[0006]

A feature of the present invention is that, in a communication system in which a base station and a toll base station are connected to each other through an optical transmission line to perform mutual communication, the frequency of the frequency transmitted from the toll base station to the base station is A frequency conversion local is sent together to different same radio signals, and the base station converts the same signal from the base station into the same radio frequency by the local and sends it out from one antenna. Also, when frequency-converting a plurality of radio signals received by a plurality of antennas in the base station, one received signal is frequency-converted using the same local and transmitted to the centralized base station. In the centralized base station, the frequency multiplexed signal is converted into the same frequency and demodulated. This enables economical transmit / receive diversity.

[0007]

According to the present invention, the base station and the toll base station perform frequency conversion using the common oscillator in the uplink and the downlink and frequency-division multiplex the diversity signal.
Further, since the frequency local is transferred from the centralized base station to the base station, the base station can be simplified, downsized, and made economical.

[0008]

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. In this embodiment, signal transmission between a base station 2 and a toll base station 1 in a mobile communication system is transmitted by optical fibers 11 and 26. A configuration for doing so will be described.

The base station 2 includes antennas 45 and 46 that form a wireless transmission path with a mobile station terminal in a wireless zone, a transmission / reception separator 43 that separates a transmission signal to the mobile station and a reception signal from the mobile station, 44, amplifier 18, 1 for amplifying received signal
9, a mixer 21 for converting one received signal to a different frequency, a band filter 23 for removing unnecessary waves, a combiner 24 for frequency-multiplexing a plurality of received signals, and a received signal from a mobile device is transmitted to a centralized base station. , An optical / electrical converter 25, an optical / electrical converter 12 for sending out an optical signal transmitted from a centralized base station to a mobile device, band filters 13, 14 for separating a frequency-multiplexed signal from the centralized base station, A band filter 15 for separating the frequency conversion local, a mixer 20 for converting the diversity transmission signal frequency-converted by the centralized base station into a radio frequency to the mobile device, a band filter 22 for removing unnecessary waves, and amplifiers 16 and 17. Is equipped with.

In the centralized base station 1, after the received signal from the mobile station via the base station is returned to the electric signal by the optical / electrical converter 27, the frequency-multiplexed signals are distributed by the bandpass filters 28 and 29, The reception signals frequency-converted by the base station are converted to desired frequencies by the mixers 30, 31, and the oscillators 34, 35, unnecessary waves are removed by the bandpass filters 32, 33, and the respective reception signals are demodulated by the demodulators 39, 40. Is entered. That is, the reception signals from the antennas 18 and 19 are input to the demodulators 39 and 40, respectively, and the transmission signals from the mobile station are demodulated. The distributed carrier is input to the judging device 42 and a high level reception path (antenna)
Is determined. (Or, the baseband signals of the demodulators 39 and 40 are input and compared in error rate.) Based on the result, one of the demodulators 39 and 40 is selected and output by the switch 41. The transmission signal from the modulator 3 is selected by the previous decision device through the switch 4, and the synthesizer 9 is supplied with either one of the signals frequency-converted by the mixers 5 and 6 and the oscillators 34 and 35. Also, the oscillators 34 and 35 stabilized by the phase comparator 38 are connected to the mixer 3
6, a frequency conversion local is generated, an unnecessary wave is removed by a bandpass filter 37, and then the combined signal is input to a combiner 9 and frequency-multiplexed and then input to an electric / optical converter 10. The converted optical signal is an optical fiber. 11 to the base station 2.

FIG. 3 shows a structural example of a phase comparator circuit for stabilizing the oscillator. Oscillators 34, 35
Is converted into a low frequency by frequency dividers 67 and 68, and the phase is compared with that of a highly stable low frequency oscillator 63. As a result, the oscillation frequencies of the oscillators 34 and 35 become stable, and the frequency difference between them can be made constant. The integrators 66 and 69 are used to stabilize the phase control of the oscillators 34 and 35.

[0012]

As described above, according to the present invention, the base station and the centralized base station can transmit the uplink and downlink diversity signals in one optical fiber and reduce the number of frequency conversion locals. It has the advantages that it can be downsized, simplified, and economical.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a conventional embodiment.

FIG. 3 is a configuration diagram of an example of a phase comparison circuit.

[Explanation of symbols]

1 Centralized base station 2 Base station 3 Modulator 4 Transmission changeover switch 5, 6, 20, 21, 30, 31, 31, 36 Mixer 7, 8, 13, 14, 14, 15, 22, 23, 28, 29,
32,33,37 bandpass filter 9,24 combiner 34,35 oscillator 10,25 electric / optical converter 11,26 optical fiber 12,27 optical / electrical converter 16,17,18,19,60,61 amplifier 43 , 44, 50, 51 Transmitter / receiver separator 45, 46, 48, 49 Transmitter / receiver antenna 39, 40, 58, 59 Demodulator 42, 54 Judgmenter 41, 55 Reception changeover switch 4, 52 Transmission changeover switch 62 Mobile terminal 63 oscillator 64,65 mixer 66,69 integrator 67,68 frequency divider

Claims (1)

[Claims] 1. 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, the radio channel signal from the mobile terminal is received by the plurality of antennas of the base station, each amplified reception signal is converted into a different frequency, and the plurality of frequency-converted reception signals are received. Means for frequency-multiplexing the frequency-multiplexed signal, converting the frequency-multiplexed signal into an optical signal by an electric / optical converter, and transmitting the optical signal to the toll base station through an optical transmission line; / After converting into an electric signal with an electric converter, distributing the frequency-multiplexed signal, converting each signal into the same frequency, and demodulating the electric signal into a baseband signal with different demodulators, The quality of the received signal respectively compared by the determination unit,
Equipped with a means for outputting a demodulated baseband signal of good quality, equipped with a transmission switch for branching and selecting a modulated signal from a centralized base station to a mobile terminal, converting an output signal to a different frequency, and transmitting the frequency-converted transmission. Frequency-multiplexing the signal, converting the frequency-multiplexed signal into an optical signal by an electrical / optical converter,
The optical signal is transmitted to a base station through an optical transmission line, the optical signal is converted into an electric signal by an optical / electrical converter in the base station, and the frequency-converted radio signal is converted into the same radio frequency, A local signal having a frequency difference between oscillators having different frequencies in the base station is transferred to the base station, the same modulated signal having a different frequency is converted to the same frequency by the local signal, and one received signal from the mobile terminal A diversity transmission / reception system characterized by performing frequency conversion on.