JP3223952B2 - Signal transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting a signal from a plurality of mobile terminals via a radio base station installed in each radio zone to a centralized base station connected to the radio base station via an optical transmission line. The present invention relates to a signal transmission device for transmitting and receiving signals.

[0002]

2. Description of the Related Art Signal transmission in which a plurality of mobile terminals transmit and receive signals via a radio base station installed in each radio zone to a centralized base station connected to the radio base station via an optical transmission line. In the apparatus, a plurality of radio signals allocated to each radio base station are frequency-multiplexed, and subcarrier optical multiplexing (SCM:
Subcarrier Multiplexing) is used.

FIG. 5 is a block diagram showing a configuration example of the conventional signal transmission device. In this figure, C is a centralized base station and D is a wireless base station. The centralized base station C has a line controller and a modem for a wide area communication line, and is connected to another centralized base station via the wide area communication line. The modulator 9- in the centralized base station C
A signal modulated by i (i = 1,..., n, and so on)
After the frequency conversion by the frequency converter 10-i, the signals are multiplexed and become a frequency multiplexed signal. Then, the frequency multiplexed signal is converted into an optical signal by the electric / optical converter 8 and transmitted to the radio base station D via the optical fiber 7. Next, the optical signal is reconverted into a frequency multiplexed signal by the optical / electrical converter 6 in the radio base station D, and is distributed by the distributor 5 to n bandpass filters 4-Di. From the distributed signals, only signals in a predetermined pass band are extracted by the band pass filter 4-Di. The extracted signal is frequency-converted into a radio frequency band by the frequency converter 26-Di, and is amplified by the high-power amplifier 3-Di. Then, the n signals output from the respective high-power amplifiers 3-Di are combined by the combiner 22 and then transmitted to the mobile terminal by the antenna 1 via the duplexer 2.

On the other hand, a transmission signal from a mobile terminal is received by an antenna 1 and is distributed to n low-noise amplifiers 11-Di via a transmission / reception switch 2 by a distributor 23. Each of the divided signals is frequency-converted by the frequency converter 27-Di, and is combined by the combiner 13. The frequency-division multiplex signal output from the coupler 13 is converted into an optical signal by the electric / optical converter 14, and
It is transmitted to the centralized base station C. The optical signal is transmitted to the centralized base station C
Is converted again into an electric signal by the optical / electrical converter 16 and distributed to the n frequency converters 19-i. Each of the divided signals is frequency-converted by the frequency converter 19-i and then demodulated by the demodulator 18-i.

Next, FIG. 6 is a block diagram showing a configuration example of a conventional signal transmission device when the centralized base station C is connected to the radio base stations Di in a plurality of radio zones. In this figure, each radio base station Di has the same configuration as the radio base station D shown in FIG. In this case, the centralized base station C and each wireless base station Di are connected by individual optical transmission lines (E / O, O / E, optical fibers).

[0006]

By the way, in the signal transmission device of the above-mentioned method, it is important to reduce the power consumption and the size of the radio base station. One means for reducing the power consumption of the radio base station is to reduce the power consumption of a high power amplifier (HPA). However, in the signal transmission device shown in FIG. 5, between the high-power amplifier 3-Di and the antenna 1,
Since the coupler 22 and the duplexer 2 are arranged, the output level of the high-power amplifier 3-Di needs to be set in consideration of the insertion loss of these components. In particular, the insertion loss of the coupler 22 is about 4 even in the case of two-wave coupling.
Since it is dB, the high power amplifier requires about 2.5 times as much power consumption as compared to the case without the coupler 22. For this reason, the conventional signal transmission device described above has a disadvantage that it is difficult to reduce the power consumption and size of the wireless base station.

In a conventional signal transmission apparatus, as shown in FIG. 6, when a wireless base station is installed in each of a plurality of wireless zones, optical transmission is individually performed from a centralized base station to each wireless base station. There is a drawback that it is necessary to provide a road, and laying and maintenance of the road requires a lot of cost.

SUMMARY OF THE INVENTION The present invention has been made in view of such a background, and aims to reduce the power consumption and size of a radio base station and to connect a plurality of radio base stations and a centralized base station with a small number of optical transmission lines. It is an object of the present invention to provide a signal transmission device capable of connecting between the two.

[0009]

According to the first aspect of the present invention,
In a signal transmission device having a configuration in which a centralized base station having a line control device and a modem device for a wide area communication line and a wireless base station that transmits and receives wireless signals to and from mobile terminals in a predetermined wireless zone are connected by an optical fiber, The centralized base station includes an electrical / optical converter and an optical / electrical converter for connecting the optical fiber, and the wireless base station includes a main wireless base station and one or more slave wireless base stations. The main radio base station receives an optical signal output from the centralized base station via the antenna for transmitting / receiving a radio signal to / from the mobile terminal and the optical fiber, and frequency-multiplexes the optical signal. An optical / electrical converter for converting the signal into a signal; a distributor for distributing the frequency multiplexed signal output from the optical / electrical converter of the main radio base station; A frequency separator for separating the signal of the number 1; a transmission frequency converter for converting a signal separated by the frequency separator of the main radio base station into a transmission signal of an antenna of the main radio base station; A receiving frequency converter that converts the frequency of the received signal received by the station antenna, and a coupler that frequency-multiplexes the signals output by the receiving frequency converters of the master radio base station and the slave radio base station,
An electrical / optical converter for converting the frequency multiplexed signal output from the coupler into an optical signal and transmitting the optical signal to the centralized base station via the optical fiber, wherein the slave radio base station comprises: An antenna for transmitting / receiving a radio signal to / from a mobile terminal different from the mobile terminal for transmitting / receiving a radio signal to / from the main radio base station; A frequency separator for separating one signal having a different frequency from the radio signal separated by the separator, and a signal separated by the frequency separator of the slave radio base station into a transmission signal of an antenna of the slave radio base station A transmission frequency converter, and a reception frequency converter for converting a frequency of a reception signal received by an antenna of the slave radio base station, wherein the distributor of the master radio base station and the frequency separator of the slave radio base station With , And it is characterized in that between the coupler of the main radio base station and the reception frequency converter of the 従無 base station is connected by a coaxial cable.

According to a second aspect of the present invention, in the signal transmission apparatus of the first aspect, the slave radio base station is installed in a radio zone different from a radio zone in which the master radio base station is installed. It is characterized by:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

§1. Overview The features of the present invention are the following two points. (1) The wireless base station is separated into a main wireless base station having an electric / optical converter, an optical / electrical converter, and a transmitting / receiving section, and one or more slave radio base stations having only a transmitting / receiving section, An antenna is provided for each of the radio base station and each slave radio base station. (2) Only the main radio base station is connected to the centralized base station by an optical transmission line, and the slave radio base station is connected to the main radio base station by a coaxial cable.

This eliminates the need to provide a coupler between the high power amplifier and the antenna. As a result, the output level of the high power amplifier can be reduced by the insertion loss of the coupler as compared with the conventional configuration, and the power consumption of the high power amplifier can be reduced accordingly. Therefore, it is possible to reduce the power consumption and size of the wireless base station. When a wireless base station is installed in each of a plurality of wireless zones, an optical transmission line may be provided only between the centralized base station and the main wireless base station. The number can be reduced.

§2. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the signal transmission device according to the first embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. The difference between the signal transmission device shown in this figure and the signal transmission device of FIG.
−i. Hereinafter, unless otherwise specified, i = 1,..., N. However, for clarity of explanation, "1," instead of "i" as necessary
..., n ". In the above-mentioned radio base station group,
Only the main radio base station A has the optical / electrical converter 6 and the electric / electrical
An optical converter 14 is provided, and the optical fibers 7 and 1 are connected through the optical / electrical converter 6 and the electrical / optical converter 14.
5 is connected to the centralized base station C.

Next, the operation of the signal transmission device having the above configuration will be described. First, from the centralized base station C to the main radio base station A
Signal transmission on a line going to the slave radio base station Bi (hereinafter, referred to as a downlink) will be described. First, the modulator 9 in the centralized base station C uses a built-in synthesizer to output an arbitrary frequency signal within a frequency bandwidth allocated in a wireless section. Then, the frequency converter 10 frequency-converts the output signal of the modulator 9 respectively. The other modulators 9-Bi and frequency converters 10-Bi in the centralized base station C also perform similar processing in parallel.

The respective frequency converters 10, 1
The output signals of 0-Bi are multiplexed to form a frequency multiplexed signal. Next, the electric / optical converter 8 converts the frequency multiplexed signal into an optical signal, and transmits the signal through the optical fiber 7 to the main radio base station A.
To be transmitted. In the main radio base station A, the optical / electrical converter 6 reconverts the optical signal transmitted from the centralized base station A into a frequency multiplexed signal.

FIG. 2 is an explanatory diagram showing a frequency arrangement in an output signal (frequency multiplexed signal) of the optical / electrical converter 6 and a pass band of each band-pass filter 4, 4-Bi. In this figure, SA, S1,..., And Sn have frequency-converted output signals of modulators 9, 9-B1,..., 9-Bn by frequency converters 10, 10-B1,. Indicates a signal. SA, S1,..., Sn are
.., 4-Bn
Passband _{△ f A, △ f B1,} ..., they are arranged in the frequency of the △ f _Bn. Further, △ f _A , Bf _B1 , ..., △ f
_Bn corresponds to the variable frequency bands of the modulators 9, 9-B1,..., 9-Bn, respectively.

The distributor 5 shown in FIG.
Distributes the frequency multiplexed signal output by n + 1, and
The signal is passed through the bandpass filter 4 in the main radio base station A and
The band-pass filter 4-Bi in each slave radio base station Bi
input. The band-pass filter 4 performs the above-described frequency multiplexing signal.
From the predetermined passband (Δf _A) Signal (see Figure 2)
Shown in SA) and output. Next, the frequency change
The converter 24 converts the output signal (SA) of the bandpass filter 4
The frequency is converted to a radio frequency band, and the high-power amplifier 3
The output signal of the wave number converter 24 is amplified. And high output
The output signal of the amplifier 3 is transmitted to the antenna via the transmission / reception switch 2.
1 and transmitted to the mobile terminal.

In each slave radio base station Bi,
The same processing as the processing performed in the main radio base station A described above is performed in parallel. That is, the frequency multiplexed signal output from the distributor 5 in the main radio base station A is
Only signals within a predetermined pass band (△ f _Bi ) are taken out by −Bi, frequency-converted by a frequency converter 24-Bi, amplified by a high-power amplifier 3-Bi, and then transmitted / received through a transmission / reception switch 2-Bi. The signal is input to the antenna 1-Bi and transmitted to the mobile terminal. Thus, in this configuration, since there is no coupler between the high-output amplifier and the transmission / reception switch, the output of the high-output amplifier can be designed to be lower than that of the conventional configuration shown in FIG. 5, and the power consumption of the radio base station can be reduced. Can be reduced.

Next, signal transmission on a line (hereinafter referred to as an uplink) from the main radio base station A and the sub radio base stations Bi to the centralized base station C will be described. In the main radio base station A shown in FIG. 1, a transmission signal of a mobile terminal (not shown) is received by an antenna 1 and input to a frequency converter 25 via a transmission / reception switch 2 and a low noise amplifier 11. Similarly, in each slave radio base station Bi, the transmission signal of another mobile terminal is received by the antenna 1-Bi, and the transmission / reception switch 2-Bi and the low-noise amplifier 11-Bi.
The signal is input to the frequency converter 25-Bi via Bi.
Then, the coupler 13 in the main radio base station A combines the output signals of the frequency converters 25 and 25-Bi, and
Input to the optical converter 14.

FIG. 6 shows the frequency arrangement in the output signal (frequency multiplexed signal) of the coupler 13 and the pass bands of the band-pass filters built in the frequency converters 25, 25-B1,..., 25-Bn. FIG. In this figure, RA, R1,..., Rn are output signals of the frequency converter 25, RA ′, R1 ′,..., Rn ′ are output signals of the frequency converter 25-B1, and RA ″, R1 ″,. , R
n "denotes an output signal of the frequency converter 25-Bn. _{Also, △ f A ', △ f} B1', ..., △ f Bn ' is the frequency converters 25,25-B1, ..., built in the 25-Bn This is the pass band of the band pass filter that is being used.

The electric / optical converter 14 in the main radio base station A shown in FIG. 1 converts the frequency multiplexed signal output from the coupler 13 into an optical signal, and outputs the signal through the optical fiber 15 to the centralized base station C.
To be transmitted. In the centralized base station C, the optical / electrical converter 1
6 reconverts the optical signal into a frequency multiplexed signal. The output signal of the optical / electrical converter 16 is output to the frequency converter 1
9, 19-Bi. The frequency converter 19 frequency-converts a signal group within a predetermined signal band (（f _A ′ shown in FIG. 3) into a signal group within the input signal band of the demodulator 18.
The demodulator 18 extracts one wireless signal from the frequency-converted signal group using a built-in synthesizer and a band-pass filter, and then demodulates the wireless signal. Further, the other frequency converters 19-Bi and demodulators 18-Bi in the centralized base station C also perform similar processing in parallel, and after frequency-converting a signal group within a predetermined signal band (Δf _Bi ), Extract and demodulate one radio signal.

Next, the correspondence between the first embodiment and the present embodiment will be described. Antenna: Antenna 1, 1-Bi Optical / electrical converter: Optical / electrical converter 6 Divider: Divider 5 Frequency separator: Bandpass filter 4, 4-Bi Transmission frequency converter: Frequency conversion , 24-Bi receiving frequency converter… frequency converter 25, 25-Bi coupler… coupler 13 electric / optical converter… electric / optical converter 14

§3. Second Embodiment Next, a second embodiment of the present invention will be described. FIG.
FIG. 6 is a block diagram showing a configuration of a signal transmission device according to a second embodiment of the present invention. In this figure, a master radio base station A, a slave radio base station Bi, and a centralized base station C have the same configurations as those shown in FIG. 1 (first embodiment). However, in the first embodiment, the main radio base station A and the slave radio base station Bi are installed in the same radio zone, whereas in the present embodiment, each radio base station is It is installed in different wireless zones (however, each wireless zone is all covered by the centralized base station C).

Then, of the main radio base station A and the slave radio base stations Bi, only the main radio base station A is connected to the centralized base station C by the optical fibers 7 and 15. On the other hand, each slave radio base station Bi is a splitter and a combiner included in the master radio base station A (the splitter 5 and the combiner 13 shown in FIG. 1).
Is connected to the main wireless base station A via a metallic cable. Therefore, in the conventional embodiment shown in FIG. 6, the connection between the centralized base station C and each wireless base station is
Although the respective optical fibers are connected by individual optical fibers, in the present embodiment shown in FIG. 4, only two optical fibers are required. The operation of the signal transmission device according to the present embodiment is as follows.
Since the operation is the same as that of the signal transmission device according to the first embodiment, the description of the operation is omitted.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and changes in design and the like may be made without departing from the gist of the present invention. Even if there is, it is included in the present invention.

[0026]

As described above, according to the present invention,
In the signal transmission device for connecting the centralized base station and the wireless base station with the optical fiber, the antennas are installed at the main wireless base station and each of the slave wireless base stations, so that the coupler is provided between the high-power amplifier and the antenna. There is no need to provide As a result, the output level of the high power amplifier can be reduced by the insertion loss of the coupler as compared with the conventional configuration, and the power consumption of the high power amplifier can be reduced accordingly. Therefore, it is possible to reduce the power consumption and size of the wireless base station. When a wireless base station is installed in each of a plurality of wireless zones, an optical transmission line may be provided only between the centralized base station and the main wireless base station. The number can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a signal transmission device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a frequency allocation of a frequency multiplexed signal and a pass band of the frequency multiplexed signal in a downlink of the embodiment.

FIG. 3 is an explanatory diagram showing a frequency allocation of a frequency multiplexed signal and a pass band of the frequency multiplexed signal in an uplink of the embodiment.

FIG. 4 is a block diagram illustrating a configuration of a signal transmission device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration example of a conventional signal transmission device.

FIG. 6 is a block diagram illustrating a configuration example of a conventional signal transmission device.

[Explanation of symbols]

A: master radio base station, B-1, Bn: slave radio base station, C: centralized base station, D: conventional radio base station,
1,1-B1,1-Bn ... antenna, 2,2-B1,
2-Bn ... transmission / reception switch, 3,3-B1,3-Bn ...
High power amplifier (HPA), 4,4-B1,4-Bn ...
Band-pass filter (BPF), 5, 23 ... distributor
6, 16 ... optical / electrical converter, 7, 15 ... optical fiber, 8, 14 ... electrical / optical converter, 9, 9-B1, 9
−Bn... Modulator (MOD), 10, 19, 24, 25
... Frequency converter (f-conv), 11, 11-B
1,11-Bn Low noise amplifier (LNA) 13,2
2 ... Coupler, 18, 18-B1, 18-Bn ... Demodulator (DEM)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-70361 (JP, A) JP-A-5-14264 (JP, A) JP-A-6-233345 (JP, A) JP-A-5-233345 122135 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 14/00-14/08 H04B 10/00-10/28 H04Q 7/36

Claims (2)

(57) [Claims] A centralized base station having a line controller and a modem for a wide area communication line and a wireless base station for transmitting and receiving wireless signals to and from mobile terminals in a predetermined wireless zone are connected by an optical fiber. In the signal transmission device, the centralized base station includes an electric / optical converter and an optical / electrical converter that connect the optical fiber, and the radio base station includes a main radio base station and one or more slave radios. And a base station, wherein the main radio base station receives an optical signal output from the centralized base station via the optical fiber, an antenna for transmitting and receiving a radio signal to and from the mobile terminal, An optical / electrical converter for converting an optical signal into a frequency multiplexed signal, a distributor for distributing a frequency multiplexed signal output from the optical / electrical converter of the main radio base station, and a frequency multiplexer output from the distributor. From the signal, a frequency separator that separates one signal of a predetermined frequency, a transmission frequency converter that converts the signal separated by the frequency separator of the main radio base station into a transmission signal of the antenna of the main radio base station, A reception frequency converter that converts the frequency of a reception signal received by the antenna of the main radio base station; and a coupler that frequency-multiplexes signals output by the reception frequency converters of the main radio base station and the slave radio base station. An electrical / optical converter for converting the frequency multiplexed signal output from the coupler into an optical signal and transmitting the optical signal to the centralized base station via the optical fiber; An antenna for transmitting / receiving a radio signal to / from a mobile terminal different from the mobile terminal for transmitting / receiving a radio signal to / from the main radio base station; A frequency separator for separating one signal having a different frequency from the radio signal separated by the frequency separator of the base station; and transmitting the signal separated by the frequency separator of the slave radio base station to the antenna of the slave radio base station. A transmission frequency converter for converting the signal into a signal; and a reception frequency converter for converting the frequency of the reception signal received by the antenna of the slave radio base station. The distributor of the master radio base station and the slave radio base station A signal transmission device, wherein a connection between the reception frequency converter of the slave radio base station and a coupler of the master radio base station is connected by a coaxial cable. 2. The signal transmission device according to claim 1, wherein the slave radio base station is installed in a radio zone different from a radio zone in which the master radio base station is installed. Transmission equipment.