JPH05153010A - Mobile communication system - Google Patents

Abstract

PURPOSE:To miniaturize, simplify and economize a base station and a centralized base station by using an oscillator which is used at the time of frequency- multipllexing a diversity signal of up/down lines in the base station and the centralized base station in common. CONSTITUTION:The constitution of the system is that the centralized base station 1 and the base station 2 are connected by optical fibers 12 and 31 which are respectively the up/down lines. Then, in this case, the oscillator 17 outputting the signal for frequency conversion in the case station 2 and the oscillator 57 outputting the signal for frequency conversion in the centralized base station 1 are used for the up/down lines in common. Namely, in the base station 2, receiving signals from plural antennas 23 and 24 are transmitted to the centralized base station 1 by frequency-converting one of the receiving signals and frequency-multiplying the plural receiving signals base on the signal from the oscillator 17 shared for up/down. In the centralized base station 1, the signal is separated and demodulated by the signal from the oscillator 57 shared for up/down. The signal from the centralized base station 1 to the base station 2 is transmitted like this.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for wireless communication using a small and lightweight portable mobile terminal. In particular, it relates to a mobile communication system for performing communication using the same frequency between a base station and a mobile device. More specifically, the present invention relates to one that performs diversity reception or diversity transmission / reception in a base station under the control of a centralized base station.

[0002]

2. Description of the Related Art A diversity reception in which a radio signal received by a plurality of antennas in a base station is demodulated by different demodulators and the level or error rate of the received signal of each antenna is compared and the optimum demodulator output is selected Has all been done at the base station.

The structure of this conventional example is shown in FIG.

A voice baseband signal is input to the base station 42 from the exchange station, converted into a radio signal by the modulator 47, and then the antenna 43 or 44 via the switch 48.
Radio waves are radiated from the mobile device 55 or 56. The received signal from the mobile device is transmitted to the demodulator 5 via the receivers 49 and 50.
1 and 52, the carrier level from the receiver is determined by the level detector 53, and the switch 54 selects the high level demodulator output.

In this system, the number of base stations increases when the wireless zone is reduced, so it is necessary to downsize and simplify the base stations. Also, since only one frequency can be used at the same time, there is a problem that congestion occurs when traffic increases.

Therefore, for the purpose of efficiently allocating a plurality of frequencies to the same radio zone, transmission / reception diversity control is further performed in the centralized base station, and signals are transferred between the base station and the centralized base station to transmit the antenna of the base station. There is a diversity reception or transmission / reception method for selecting.

[0007] As this system, the present inventors have a structure in which the base station and the toll base station are first connected by an optical transmission line, and a plurality of diversity signals are transmitted from the base station to the toll base station through a pair of optical transmission lines. Proposed (Japanese Patent Application No. 3-249471).

[0008]

By the way, in the case of adopting a method of frequency-multiplexing diversity signals from a base station or a toll base station and transmitting them by an optical transmission line of two lines, an up line, At least two oscillators are required in the base station and the centralized base station to individually perform frequency multiplexing or demultiplexing of two signals in the downlink, which hinders downsizing and simplification of the base station and the centralized base station. ..

The present invention provides a compact, simple and economical base station and centralized base station by frequency-sharing one oscillator for both uplink and downlink to frequency-multiplex diversity signals. The purpose is to provide a configurable communication method.

[0010]

The present invention comprises a base station for performing wireless communication with a mobile terminal in a wireless zone, the base station being provided with a plurality of antennas. Provide a centralized base station that performs centralized control for each
The base station includes means for transmitting information about an antenna received signal to a toll base station controlling the base station, and the toll base station determines an antenna having good reception quality based on the information from the base station. In the mobile communication system including means for selecting an antenna having good reception quality and performing communication, the base station frequency-multiplexes received signals received by the plurality of antennas and transmits the frequency-multiplexed signals to the centralized base station. And means for demultiplexing and transmitting from the antenna as a radio signal a signal that has been frequency-multiplexed and transmitted from the toll base station, and the means for transmitting the signal received by one of the antennas. It includes means for frequency-converting one oscillator as a local oscillator and frequency-multiplexing with another received signal, and means for transmitting from the antenna is transmitted from the toll base station. The at least one signal of the frequency-multiplexed signals transmitted from the base station by the first oscillator, and the at least one signal of the frequency-multiplexed signals transmitted from the base station. As means for performing frequency conversion to demodulate to a received signal of the same frequency, means for determining an antenna with good reception quality based on this demodulated output, and at least one of the radio signals transmitted to the base station And a means for frequency-multiplexing with a second oscillator, frequency-multiplexing with another signal, and transmitting to the base station.

[0011]

In the base station, the received signals from the plurality of antennas are respectively amplified, and one received signal is frequency-converted based on the signal from the oscillator commonly used for uplink and downlink. The signals received by the plurality of antennas are frequency-multiplexed, converted into optical signals, and transmitted to the toll base station. The centralized base station converts the received signal into an electric signal, demodulates it, and converts it into a radio frequency. The demodulated radio frequency signal is separated into a reception signal corresponding to the antenna and demodulated by a signal from an oscillator commonly used for uplink and downlink provided corresponding to the base station.
The reception quality is determined by this demodulated signal, and the signal of the antenna having good reception quality is selected. Similarly, the signal from the centralized base station is also frequency-converted by the signal from the oscillator commonly used for uplink and downlink, frequency-multiplexed, converted into an optical signal, and transmitted to the base station. The base station converts the received optical signal into an electric signal, demultiplexes the signal, converts it into a radio frequency by the signal from the above-described upstream / downlink common oscillator, and then radiates it from the antenna to the mobile device.

As described above, in the base station and the centralized base station, one oscillator is shared by the uplink and the downlink, frequency conversion is performed, and the diversity signal is frequency-multiplexed or demultiplexed. The base station can be simplified, downsized, and made economical.

[0013]

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

FIG. 1 shows the configuration of a mobile communication system according to an embodiment of the present invention. In this mobile communication system, a base station 2, a toll base station 1 and a base station 2 are respectively connected to an uplink and In this configuration, the optical fibers 12 and 31 which are downlinks are connected. Although a plurality of base stations are connected to the centralized base station 1, only one is shown in FIG.

The base station 2 includes antennas 23 and 24 forming a wireless transmission path with a mobile station terminal in a wireless zone, and a transmission / reception separator 21 for separating a transmission signal to the mobile station and a reception signal from the mobile station. , 22 and an amplifier 25 for amplifying the received signal,
26, a mixer 27 for converting one received signal to a different frequency, an oscillator 17, a bandpass filter 28 for removing unnecessary waves of the frequency-converted signal, and a synthesizer 29 for frequency-multiplexing a plurality of received signals. And electric power for transmitting the received signal from the mobile device to the centralized base station 1 as an optical signal.
An optical converter 30 and an optical / electrical converter 13 for converting an optical signal transmitted from the toll base station 1 into a radio frequency signal.
A band-pass filter 14 or 15 for separating the frequency-multiplexed signal transmitted from the centralized base station 1, and a diversity transmission signal frequency-converted by the centralized base station supplied from an oscillator 17 to a radio frequency to the mobile device. , A bandpass filter 18 for removing unnecessary waves of the frequency-converted signal of the mixer 16, an amplifier 19 for amplifying a signal to be sent to a mobile device and giving it to the transmission / reception separators 21 and 22,
And 20.

The centralized base station 1 is an optical / electrical converter 32 for converting a signal transmitted as an optical signal from the base station 2 into an electric signal.
And a mixer 33 for converting a signal in the radio band converted by the optical / electrical converter 32 into an intermediate frequency and a radio frequency oscillator 9 for giving a radio frequency signal to the mixer 33.
, Band filters 34 and 35 that perform demultiplexing of the signals frequency-multiplexed in the base station 2, a mixer 36 that further frequency-converts the output of the band filter 34 based on the output of the oscillator 57, and unnecessary waves are removed. The bandpass filter 37, the demodulator (1) 38 for demodulating the received signals from the respective antennas 23, 24, the demodulator (2) 41, and the antenna with the error rate of the baseband signals output by the demodulators 38, 39. Judgment device 40 for comparing the reception qualities of 23 and 24
And the antenna 23 or 2 depending on the output of the determiner 40.
The reception changeover switch 41 selects one of the reception signals of No. 4 and the reception path. Further, as a configuration on the transmission side, a transmission changeover switch 4 for selecting which antenna of the base station 1 the output of the modulator 3 is applied to.
A mixer 5 that performs frequency conversion on the output of the oscillator 57 for one signal; a bandpass filter 6 that removes unnecessary waves; and a synthesizer 7 that frequency-multiplexes two radio signals.
An oscillator 9 for converting the frequency-multiplexed signal output from the combiner 7 into a radio signal, and an electric / optical converter 11 for removing an unnecessary wave with a bandpass filter 10 and then converting the optical signal into an optical signal 12. I have it.

Here, the feature of this embodiment is that the oscillator 17 for outputting the frequency conversion signal at the base station 2 and the oscillator 57 for outputting the frequency conversion signal at the centralized base station 1 are for uplink. It is shared by and for the downlink.

Next, the diversity control operation according to this embodiment will be described.

Received signals from the mobile station, which are received by the two antennas 23 and 24, are amplified by amplifiers 25 and 26, respectively, after passing through transmission / reception separators 21 and 22. The received signal from the antenna 23 is converted by the mixer 27 into a frequency different from that of the received signal from the antenna 24. The two signals are frequency-multiplexed by the combiner 29, converted into an optical signal by the electric / optical converter 30, and transmitted to the toll base station 1 through the optical fiber 31 of the upstream line.

In the centralized base station 1, after the received signal from the mobile station via the base station 2 is returned to the electric signal by the optical / electrical converter 32, the mixer 33, based on the signal from the radio frequency oscillator 9, outputs the intermediate frequency. Convert to. The frequency-multiplexed intermediate frequency signal is distributed by the bandpass filters 34 and 35, respectively. Antenna 23 whose frequency is converted by the base station
The received signal of the mixer 3 is based on the signal from the oscillator 57.
It is converted to a desired frequency by 6. And antenna 2
The received signals received at 3 and 24 are input to demodulators 38 and 39 and demodulated. The distributed carriers are input to the determiner 40, and a high-level reception path (antenna) is determined. Based on the result, either one of the demodulators 38 and 39 is selected and output by the reception changeover switch 41.

The transmission signal from the modulator 2 is sent to the above-mentioned judging device 4
According to the determination of 0, either the signal selected through the transmission changeover switch 4 and frequency-converted by the oscillator 57 or the mixer 5 or the modulation signal as it is is input to the synthesizer 7. This output is converted into a radio signal by a radio frequency oscillator 9 and a mixer 8 and then converted into an electric / optical converter 1
The optical signal input to the optical fiber 1 and converted is transmitted to the base station 2 by the optical fiber 12.

The decision of the reception quality by the decision device 40 is as follows.
You may input a baseband signal and compare by an error rate.

Further, although the present embodiment has been described with respect to the diversity transmission / reception system, it can be implemented also in the case of the diversity reception system in which only the receiving antenna is selected in the centralized base station.

[0024]

As described above, according to the present invention, the base station and the toll base station can commonly use the oscillator used for frequency-multiplexing the uplink and downlink diversity signals in the base station and toll base station. There is an advantage that the miniaturization, simplification and economy can be achieved.

[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 example.

[Explanation of symbols]

1 Centralized base station 2, 42 Base station 3, 47 Modulator 4, 48 Transmission changeover switch 5, 8, 16, 27, 33, 36 Mixer 6, 10, 14, 15, 18, 28, 34, 35, 37
Band-pass filter 7,29 Combiner 9 Radio frequency oscillator 11,30 Electrical / optical converter 12,31 Optical fiber 13,32 Optical / electrical converter 17,57 Oscillator 19, 20, 25, 26 Amplifier 21, 22, 45, 46 transmitter / receiver separator 23, 24, 43, 44 transmitting / receiving antenna 38, 39, 51, 52 demodulator 40 determiner 41 receiving changeover switch 49, 50 receiver 53 level detector 54 receiving changeover switch 55, 56 mobile unit

Claims (1)

[Claims] 1. A central station which comprises a base station for performing wireless communication with a mobile terminal in a wireless zone, wherein the base station is provided with a plurality of antennas, and centralized control is performed for each of the plurality of base stations. A base station is provided, and means for transmitting information about an antenna reception signal of the base station to a toll base station controlling the base station is provided, and the toll base station is configured to receive the reception quality based on the information from the base station. In a mobile communication system having means for determining a good antenna and selecting an antenna having good reception quality to perform communication, the base station frequency-multiplexes received signals received by the plurality of antennas, Means for transmitting to the station, and means for demultiplexing and transmitting the signal frequency-multiplexed and transmitted from the toll base station as a radio signal from the antenna, and the means for transmitting is The unit includes means for frequency-converting a received signal received by one of the antennas using the first oscillator as a local oscillator and frequency-multiplexing with another received signal, and means for transmitting from the antenna is transmitted from the centralized base station. The at least one signal of the frequency-multiplexed signals transmitted from the base station, and the second oscillator as a local oscillator. Means for performing frequency conversion to demodulate to a reception signal of the same frequency, means for determining an antenna with good reception quality based on this demodulation output, and at least one signal of radio signals transmitted to the base station A mobile communication system comprising: means for frequency-converting by a second oscillator, frequency-multiplexing with another signal, and transmitting to the base station.