JP2003244750A - Optical transmission system for wireless base station - Google Patents

Optical transmission system for wireless base station

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Publication number
JP2003244750A
JP2003244750A JP2002035640A JP2002035640A JP2003244750A JP 2003244750 A JP2003244750 A JP 2003244750A JP 2002035640 A JP2002035640 A JP 2002035640A JP 2002035640 A JP2002035640 A JP 2002035640A JP 2003244750 A JP2003244750 A JP 2003244750A
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JP
Japan
Prior art keywords
signal
data signal
means
output
pilot signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2002035640A
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Japanese (ja)
Inventor
Hiroaki Yamamoto
浩明 山本
Original Assignee
Matsushita Electric Ind Co Ltd
松下電器産業株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Ind Co Ltd, 松下電器産業株式会社 filed Critical Matsushita Electric Ind Co Ltd
Priority to JP2002035640A priority Critical patent/JP2003244750A/en
Publication of JP2003244750A publication Critical patent/JP2003244750A/en
Pending legal-status Critical Current

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Classifications

    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THIR OWN ENERGY USE
    • Y02D70/00Techniques for reducing energy consumption in wireless communication networks
    • Y02D70/40According to the transmission technology
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THIR OWN ENERGY USE
    • Y02D70/00Techniques for reducing energy consumption in wireless communication networks
    • Y02D70/40According to the transmission technology
    • Y02D70/46Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication

Abstract

(57) [Summary] [PROBLEMS] To stabilize the frequency of radio waves radiated by each slave station by transmitting a pilot signal together with a data signal from a master station to each slave station, provided in a wireless base station for mobile communication. And an optical transmission system capable of reducing power consumption by stopping transmission of a pilot signal when there is no data signal to be transmitted. SOLUTION: Before performing optical modulation, a master station 100 outputs a pilot signal 104 in which a pilot signal 104 is modulated with a data signal 103, that is, a pilot signal 104 is output when the data signal 103 is a mark, and the data signal 103 is transmitted in a space. During the period, modulation is performed so that the pilot signal 104 is not output. In each of the slave stations 201 to 203, after the optical demodulation, the obtained electric signal is demodulated and separated into a data signal 103 and a pilot signal 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission system, and more specifically, to a plurality of slave stations that emit radio waves in the air from a master station mainly in a mobile communication radio base such as a mobile phone. To an optical transmission system for a wireless base station for optically transmitting a data signal.

[0002]

2. Description of the Related Art In an optical transmission system for a wireless base station, generally, in order to stabilize the frequency of a radio wave output from each slave station, a pilot signal is distributed from the master station to each slave station. . In this case, each slave station regenerates a clock based on the same pilot signal, so that highly accurate clocks synchronized with each other can be obtained. As a result of generating a carrier wave according to this clock, each slave station can radiate a radio wave having a stable frequency.

Conventionally, as a method of distributing a pilot signal for stabilizing a radio frequency, for example, the pilot signal is frequency-division-multiplexed with data to be transmitted, or the method is disclosed in Japanese Patent Laid-Open No. 6-98365. There is known a method of distributing a pilot signal using an optical transmission line different from that for data signals, such as the disclosed "optical transmission system for wireless link".

[0004]

However, in these conventional methods, the pilot signal is always transmitted from the master station to each slave station even when there is no signal to be transmitted, resulting in unnecessary power consumption. There was a problem that occurred.

Therefore, an object of the present invention is to provide a pilot signal together with a data signal from a master station to each slave station, which is provided mainly in a radio base for mobile communication.
An optical transmission system that can stabilize the frequency of radio waves radiated by each terminal, and can stop the transmission of pilot signals to save power consumption when there is no data to be transmitted Is to provide.

[0006]

A first invention is a system for optically transmitting a data signal from a master station to one or more slave stations, wherein the master station premodulates a pilot signal with the data signal. Pre-modulation means, and optical modulation means for modulating the carrier light by the output signal of the pre-modulation means, each slave station is an optical demodulation means for demodulating the output light of the optical modulation means, an electrical signal output from the optical demodulation means An electric demodulating means for demodulating the signal into a data signal and a pilot signal, a clock reproducing means for reproducing a clock based on a pilot signal output from the electric demodulating means, and a first clock according to a clock output from the clock reproducing means. First carrier generation means for generating a carrier,
The first carrier wave output from the first carrier wave generation means,
A modulation means for modulating the data signal output from the electrical demodulation means is provided.

As described above, in the first invention, the master station is
The pilot signal is pre-modulated with the data signal, and the carrier light is modulated with the signal obtained by the pre-modulation. Each slave station demodulates the modulated light transmitted from the master station, demodulates the electric signal obtained by demodulation to separate the data signal and the pilot signal,
A clock is regenerated based on the separated pilot signal, a first carrier is generated according to the regenerated clock, and the generated first carrier is modulated by the separated data signal. .

By performing such pre-modulation and electrical demodulation, it is possible for each terminal to reproduce mutually synchronized clocks having a stable frequency based on the pilot signal from the master station and to be transmitted. When there is no data, it becomes possible to stop the transmission of pilot signals.

In a second aspect based on the first aspect, the data signal is a binary baseband digital data signal, the pilot signal has a higher frequency than the data signal, and the pre-modulation means performs the pre-modulation. Is a modulation in which the pilot signal is output during the period when the data signal is the mark and the pilot signal is not output during the period when the data signal is the space.

In the second aspect, the transmission of the pilot signal is stopped even during the period when the data signal is a space.

A third invention is a method for optically transmitting a data signal from a master station to one or more slave stations, wherein the master station is obtained by premodulating a pilot signal with a data signal and premodulating the pilot signal. The carrier light is modulated with a signal, and each slave station demodulates the modulated light transmitted from the master station, demodulates the electric signal obtained by demodulation to separate the data signal and the pilot signal, and separates them. A clock is regenerated based on the pilot signal obtained as described above, a first carrier wave is generated according to the regenerated clock, and the generated first carrier wave is modulated with a data signal obtained separately. Characterize.

A fourth aspect of the present invention is a master station that optically transmits a data signal to one or more slave stations, and a pre-modulation means for pre-modulating a pilot signal with the data signal, and a carrier optical signal with an output signal of the pre-modulation means. And a data signal is a binary baseband digital data signal,
The pilot signal has a higher frequency than the data signal, and the pre-modulation performed by the pre-modulation means is such that the pilot signal is output during the mark period of the data signal and does not output during the space period of the data signal. Is characterized in that.

The fourth invention corresponds to the master station of the system according to the second invention described above.

In a fifth aspect based on the fourth aspect, the optical modulation means stops outputting the carrier light when there is no data signal to be transmitted and when the data signal is a space.

In the fifth aspect of the invention, when there is no data signal to be transmitted and when the data signal is a space,
The transmission of the carrier light itself is stopped.

A sixth invention is characterized in that, in the fourth invention, the pilot signal is a signal having a waveform capable of reproducing a clock based on the signal.

A seventh invention is characterized in that, in the sixth invention, the pilot signal is a sine wave having a constant frequency.

An eighth invention is characterized in that, in the sixth invention, the pilot signal is a square wave having a constant frequency.

A ninth invention is characterized in that, in the sixth invention, the pilot signal is a signal having predetermined information.

In the ninth aspect of the invention, information different from the data signal is transmitted to each slave station through the pilot signal.

A tenth aspect of the present invention is a slave station that receives a data signal optically transmitted from a master station, and is obtained by premodulating a pilot signal with the data signal from the master station. The modulated light obtained by modulating the carrier light with the signal is transmitted, and the optical demodulation means for demodulating the modulated light transmitted from the master station, the electrical signal output from the optical demodulation means is demodulated to obtain the data signal. An electric demodulation means for separating into a pilot signal, a clock reproduction means for reproducing a clock based on a pilot signal output from the electric demodulation means, and a first carrier wave for generating a first carrier wave according to a clock output from the clock reproduction means. The carrier wave generating means and the modulating means for modulating the first carrier wave outputted from the first carrier wave generating means with the data signal outputted from the electric demodulating means.

The tenth invention corresponds to the slave station of the system according to the first invention described above.

An eleventh invention is the tenth invention, wherein
The electrical demodulating means is a branching means for branching the electrical signal output from the optical demodulating means into two, and a high frequency for removing a high frequency component from one of the signals obtained by the branching of the branching means and extracting only the data signal. The removing means and the low frequency removing means for removing the low frequency component from the other signal obtained by the branching means branching into two and extracting only the pilot signal.

In the eleventh aspect of the invention, the electrical signal after the optical demodulation is branched into two, the high-frequency component is removed from one signal, and the low-frequency component is removed from the other signal. You are getting with a pilot signal.

The twelfth invention is the eleventh invention, wherein
It further comprises means for converting the output signal of the modulating means into a radio wave and radiating it into the air.

In the twelfth aspect of the invention, the modulated electric signal is converted into a radio wave and radiated into the air. Note that this modulation includes, for example, amplitude modulation, frequency modulation, phase modulation and the like.

The thirteenth invention is the same as the eleventh invention,
Second according to the clock output from the clock reproducing means
Mixing means for mixing the output signal of the modulating means and the second carrier wave output from the second carrier wave generating means, and the output signal of the mixing means to a radio wave. It further comprises means for radiating in the air.

In the thirteenth aspect of the invention, the frequency is up-converted to a value suitable for being radiated as a radio wave by mixing the modulated electric signal with the second carrier.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 1 is a block diagram showing a configuration of an optical transmission system for a radio base station according to a first embodiment of the present invention. In FIG. 1, the optical transmission system for a wireless base station according to the first embodiment includes a master station 1
00, three slave stations 201 to 203, and the optical transmission line 300.
It has and.

The master station 100 includes an optical modulation circuit 101 and a pre-modulation circuit 102. The slave station 201 includes the optical demodulation circuit 21.
1, electric demodulation circuit 212, identification circuit 213, clock recovery circuit 214, modulation circuit 215, two local oscillation circuits 216 and 217, mixing circuit 218, R
The F amplification circuit 219 and the antenna 220 are included. Child station 2
The configurations of 02 and 203 are similar to those of the slave station 201. Further, although the number of slave stations is three in the present embodiment, it may be other than that.

In the master station 100, the pre-modulation circuit 102
Premodulates pilot signal 104 with data signal 104 (described later). The light modulation circuit 101 includes a pre-modulation circuit 102.
The carrier light is modulated by the output signal of.

In the slave station 201, the optical demodulation circuit 211
Demodulates the modulated light (output light of the optical modulation circuit 101) transmitted from the master station 100 side through the optical transmission path 300. The electrical demodulation circuit 212 demodulates the electrical signal output from the optical demodulation circuit 211 and separates it into a data signal 103 and a pilot signal 104. The identification circuit 212 identifies the data signal 103 output from the electrical demodulation circuit 212 (that is, performs waveform shaping on the data signal 103).

The clock reproduction circuit 214 reproduces a clock based on the pilot signal output from the electric demodulation circuit 212. The local oscillation circuit 216 generates a carrier wave of frequency f1 according to the clock output from the clock recovery circuit 214. The local oscillator circuit 217 generates a frequency f according to the clock output from the clock recovery circuit 214.
Generate 2 carriers. The modulation circuit 215 modulates the carrier wave output from the local oscillation circuit 216 with the data signal 103 output from the identification circuit 213.

The mixing circuit 218 mixes the output signal (frequency f1) of the modulation circuit 215 and the carrier wave (several wave numbers f2) output from the local oscillation circuit 217. The RF amplification circuit 219 outputs the output signal (frequency f1 + f) of the mixing circuit 218.
2) is amplified. The antenna 202 is the RF amplifier circuit 21.
The output signal of 9 is converted into a radio wave and radiated in the air.

The data signal 103 may be generated outside the master station 100 or inside the master station 100. The pilot signal 104 may be generated outside the master station 100 or inside the master station 100. In addition, the data signal 10 output from the electrical demodulation circuit 212
The identification circuit 213 may be omitted if the disturbance of the waveform of 3 is small and shaping is not necessary. If the power of the signal output from the mixing circuit 218 is high, the amplifier circuit 219 may be omitted.

FIG. 2 shows time waveforms of signals at some points in the block diagram of FIG. Figure 2
The operation of the system shown in FIG. 1 will be described with reference to FIG. Master station 10
At 0, the data signal 103 and the pilot signal 104 to be transmitted are input to the pre-modulation circuit 102. The data signal 103 is a binary baseband digital signal, and its time waveform is shown in FIG. The frequency of the pilot signal 104 is f0 (where f0 is the data signal 1
2 is a sine wave having a constant larger than the frequency of 03), and its time waveform is shown in FIG.

Premodulation circuit 102 receives data signal 103 and pilot signal 104, and premodulates pilot signal 104 with data signal 103. Here, pre-modulation means
The modulation is such that the pilot signal 104 is output during the period when the data signal 103 is the mark (ON), and the pilot signal 104 is not output (or the output is blocked) during the period when the data signal 103 is the space (OFF). The output waveform of the pre-modulation circuit 102 is shown in FIG.

The output signal from the pre-modulation circuit 102 enters the light modulation circuit 101 and is converted into a light intensity modulation signal. Here, the light modulation circuit 101 may be configured to directly modulate the light intensity of a semiconductor laser or LED, or may be configured to modulate the intensity of a DC optical signal with an external light intensity modulator.

In this way, the optical modulator circuit 101 outputs the carrier light modulated by the pilot signal 104 during the mark of the data signal 103, and the data signal 10 to be transmitted.
3 is not present or the data signal 103 is in the space, the output of the carrier light modulated by the pilot signal 104 is stopped. That is, when there is no data signal 103 to be transmitted or when the data signal 103 is in a space, not only the pilot signal 104 but also the carrier light itself is not output, so that power consumption is suppressed accordingly. The optical signal output from the optical modulation circuit 101 is transmitted to the slave station 2 through the optical transmission line 300.
01 and the slave stations 202 and 203.

The operation on the slave station 201 side will be described below. The optical signal from the transmission path 300 enters the optical demodulation circuit 211 and is converted into an electric signal. The waveform of this electric signal is the master station 10
The waveform of the electric signal input to the optical modulation circuit 101 of 0 and the amplitude direction are similar to each other (see FIG. 2C).

The electric signal output from the optical demodulation circuit 211 is input to the electric demodulation circuit 212, and a data signal as shown in FIG. 2D and a signal having a waveform as shown in FIG. Frequency separated. The waveform in FIG. 2 (e) is
The waveform is such that a part of the pilot signal 104 shown in (b) (specifically, the part where the data signal corresponds to the space period) is lost. Even with such an incomplete waveform, since the frequency is held, the clock can be regenerated based on that.

Here, the electric demodulation circuit 212 will be described. FIG. 3 is a block diagram showing a configuration example of the electric demodulation circuit 212. In FIG. 3, the electric demodulation circuit 212 is
The signal branch part 212a, the high frequency removal part 212b, and the low frequency removal part 212c are included. Electric demodulation circuit 212
The electric signal input to is divided into two by the signal branching unit 212a, one signal is given to the high frequency removing unit 212b, and the other signal is given to the low frequency removing unit 212c. The high-frequency removing unit 212b removes high-frequency components from the input signal by performing envelope detection, for example, to remove the high-frequency component from the input signal.
A data signal as shown in (d) is output. The low-frequency removing unit 212c removes low-frequency components from the input signal and outputs the signal shown in FIG. 2 (e)-a signal obtained by amplitude-modulating or amplitude-shift keying a carrier wave having a frequency f0 with a data signal. Output.

Referring again to FIG. 1, the electric demodulation circuit 212 receives the data signal as shown in FIG.
A signal like (e) is output, and the former is the identification circuit 21.
3, the latter is input to the clock recovery circuit 214. The discrimination circuit 213 performs waveform shaping on the data signal of FIG. 2D, and the original data signal 103 as shown in FIG.
Is output.

On the other hand, the clock recovery circuit 214 is shown in FIG.
For the signal of (e), for example, a PLL (phase locked loop)
The clock signal is reproduced by performing processing or the like.
The output signal waveform from the clock recovery circuit 214 is shown in FIG.
It shows in (f). 1 generated by the master station 100 in this way
Each terminal 201 to 20 based on one pilot signal 104
When the three clocks reproduce the common clock, the clocks with higher accuracy can be obtained as compared with the case where the clocks are independently reproduced, and the clocks of the respective terminals can be synchronized with each other.

The local oscillator circuit 216 refers to the clock output from the clock recovery circuit 214 and determines that the frequency is f
It outputs a sine wave of 1 (described later). In addition, the local oscillator circuit 2
Reference numeral 17 refers to the clock from the clock reproduction circuit 214 and outputs a sine wave having a frequency f2 (described later).

The modulation circuit 215 modulates the sine wave from the local oscillation circuit 216 according to the data signal 103 from the identification circuit 213. The modulation performed here is amplitude modulation, frequency modulation, phase modulation, or the like. In this embodiment, QPSK modulation, which is a type of phase modulation, is performed.

The QPSK signal from modulator 215 enters mixer 218 and is frequency shifted by f2. The output signal from the mixing circuit 218 is amplified by the RF amplifier circuit 219 and then radiated from the antenna 220 into the air as a radio wave.

Here, the frequency f1 is called an intermediate frequency, and is a value suitable for performing modulation by the modulation circuit 215 (for example, in the case of performing QPSK modulation, about several M to several tens MHz).
Is selected. In the slave station 201, for the time being, the intermediate frequency f1
After modulating the carrier wave of the data signal 103 with the data signal 103 and shifting the frequency of the modulated wave upward by f2, the frequency band of a desired radio wave (for example, 800 MHz or 1.5
GHz) has been up-converted.

That is, if the frequency of the carrier wave is set to the frequency band of the radio wave from the beginning, the modulation operation cannot catch up. Therefore, the frequency of the carrier wave is kept relatively low at the time of modulation, and the modulated carrier wave is set to the radio wave frequency. The band is up-converted and then radiated. Therefore,
If the modulation circuit 215 can perform a sufficiently high-speed modulation operation, up-conversion is not necessary, so the local oscillation circuit 217
The mixing circuit 218 may be deleted. Note that the slave station 202 and the slave station 203 also perform the same operations as the slave station 201.

As described above, in the optical transmission system for the radio base station according to the first embodiment, the parent station 100 is the same as the conventional one.
For each slave station 201-203, the data signal 103
And a pilot signal (here, a sine wave) 104 for optical transmission to reproduce a clock common to the slave stations 201 to 203. The difference from the conventional one is that the master station 100 transmits the pilot signal 104 to the data signal 10 before performing the optical modulation.
3 is pre-modulated, that is, modulation is performed such that the pilot signal 104 is output during the period when the data signal 103 is the mark and the pilot signal 104 is not output during the period when the data signal 103 is the space. After the optical demodulation, the obtained electric signal is demodulated and separated into a data signal 103 and a pilot signal 104.

By carrying out such pre-modulation and electrical demodulation, the data signal 103 and the pilot signal 104 can be optically transmitted through the same transmission line 300. Therefore, the number of transmission lines can be reduced as compared with the case where they are transmitted through separate transmission lines. In addition to being able to reduce the data signal 103 to be transmitted
If there is no signal or the data signal 103 has a space, the transmission of the pilot signal 104 (and its carrier light) is stopped, so that the power consumption can be significantly reduced.

The pilot signal is a sine wave in the first embodiment, but is a square wave in the second embodiment described below. Except for this point, the configuration is similar to that of the first embodiment, and redundant description is omitted as appropriate.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
2 is a block diagram showing a configuration of an optical transmission system for a wireless base station according to the embodiment of FIG. In FIG. 4, the optical transmission system for a wireless base station according to the second embodiment includes a master station 400,
It is provided with three slave stations 501 to 503 and an optical transmission line 300.

The master station 400 includes an optical modulation circuit 401 and a pre-modulation circuit 402. The slave station 501 includes an optical demodulation circuit 51.
1, an electric demodulation circuit 512, an identification circuit 513, a clock recovery circuit 514, a modulation circuit 515, two local oscillation circuits 516 and 517, a mixing circuit 518, and R
It includes an F amplifier circuit 519 and an antenna 520. Child station 5
The configurations of 02 and 503 are similar to those of the slave station 501. Further, although the number of slave stations is three in the present embodiment, it may be other than that. Each of the above-described constituent elements performs the same operation as the corresponding constituent element in FIG. 1 (see the first embodiment).

FIG. 5 shows time waveforms of signals at some points in the block diagram of FIG. Figure 5
The operation of the system of FIG. 3 will be described with reference to FIG. Master station 40
At 0, the data signal 403 to be transmitted and the pilot signal 404 are input to the pre-modulation circuit 402. The data signal 403 is a binary baseband digital signal, and its time waveform is shown in FIG. The pilot signal 404 has a frequency of f0 (where f0 is the data signal 1).
A square wave having a constant larger than the frequency of 03), and its time waveform is shown in FIG.

Pre-modulation circuit 402 receives data signal 403 and pilot signal 404, and pre-modulates pilot signal 404 with data signal 403. Here, pre-modulation means
Similar to the first embodiment, the data signal 403 is a mark (O
In the period N), the pilot signal 404 is output, and in the period when the data signal 403 is space (OFF), the pilot signal 404 is not output (or the output is cut off). The output waveform of the pre-modulation circuit 402 is shown in FIG.

The output signal from the pre-modulation circuit 402 enters the light modulation circuit 401 and is converted into a light intensity modulation signal. Here, the circuit configuration of the light modulation circuit 401 is the same as that of the light modulation circuit 101 in FIG. The optical signal output from the optical modulation circuit 401 is distributed to the slave station 501 and the slave stations 502 and 503 through the optical transmission path 300.

The operation on the side of the slave station 501 is as follows.
The operation is similar to. The configuration of the electrical demodulation circuit 512 is similar to that of the electrical demodulation circuit 212 of FIG. 1 (see FIG. 3). The waveform of the signal output from the electric demodulation circuit 512 to the identification circuit 513 side is as shown in FIG. The waveform of the signal output from the electric demodulation circuit 512 to the clock recovery circuit 514 side is as shown in FIG. The output signal waveform of the clock recovery circuit 514 is as shown in FIG.

As described above, in the optical transmission system for the radio base station according to the second embodiment, the master station 300 is the same as the conventional one.
Is a data signal 403 for each slave station 401-403.
And a pilot signal (a square wave in this case) 404 is optically transmitted to reproduce a clock common to the slave stations 501 to 503. The difference from the conventional method is that the master station 400 transmits the pilot signal 404 to the data signal 40 before performing the optical modulation.
3 pre-modulation is performed, that is, modulation is performed such that the pilot signal 404 is output during the mark period of the data signal 403 and the pilot signal 404 is not output during the space period of the data signal 403. After the optical demodulation, the obtained electric signal is demodulated and separated into a data signal 403 and a pilot signal 404.

By carrying out such pre-modulation and electrical demodulation, the data signal 403 and the pilot signal 404 can be optically transmitted through the same transmission line 300. Therefore, the number of transmission lines can be reduced as compared with the case where they are transmitted through separate transmission lines. The data signal 403 to be transmitted can be reduced.
If there is no signal or the data signal 403 is a space, the transmission of the pilot signal 404 (and its carrier light) is stopped, so that the power consumption can be significantly reduced.

In the first and second embodiments, a sine wave or a square wave having a constant frequency is used as the pilot signal, but if the clock can be regenerated based on the signal, any waveform signal can be used. You may use.

Furthermore, not only the clock can be regenerated, but also a pilot signal which itself has some information can be used (the sine wave and the square wave of the first and second embodiments are I have no information about itself). By transmitting such a pilot signal, not only can a clock common to each slave station be reproduced, but also predetermined information can be transmitted to each slave station through the pilot signal.

However, in that case, since the pilot signal is not transmitted during the period when the data signal is a space (that is, the transmission of the pilot signal is stopped irregularly), the information that can be transmitted through the pilot signal is, for example, that of each slave station. It is limited to simple information such as instructions for switching operation modes. For example, there is a method of preparing several types of pilot signals having different frequencies and waveform patterns, and changing the type of pilot signal to be transmitted when the master station wants to switch the operation mode of each slave station.

[0064]

As described above, according to the present invention, since the pilot signal is pre-modulated with the data signal and optically transmitted from the master station to each slave station, the frequency of the radio wave radiated by each terminal is stabilized. In addition, the pilot signal transmission can be stopped when there is no data signal to be transmitted or when there is a space in the data signal, so that the power consumption can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical transmission system for a wireless base station according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a time waveform of a signal in each main part in the configuration shown in FIG.

3 is a block diagram showing a configuration example of an electric demodulation circuit 212 in FIG. 1 (the same applies to the electric demodulation circuit 412 in FIG. 4).

FIG. 4 is a block diagram showing a configuration of an optical transmission system for a wireless base station according to a second embodiment of the present invention.

5 is a diagram showing a time waveform of a signal in each main part in the configuration shown in FIG.

[Explanation of symbols]

100,400 ... Master station 101, 401 ... Optical modulation circuit 102, 402 ... Pre-modulation circuit 103, 403 ... Data signal 104, 404 ... Pilot signal 201-203, 501-503 ... Slave stations 211, 511 ... Optical demodulation circuit 212, 512 ... Electrical demodulation circuit 212a ... Signal branching unit 212b ... High-frequency removing section 212c ... Low frequency removing unit 213, 513 ... Identification circuit 214, 514 ... Clock recovery circuit 215, 515 ... Modulation circuit 216, 217, 516, 517 ... Local oscillator circuit 218, 518 ... Mixed circuit 219, 519 ... RF amplifier circuit 220, 520 ... Antenna

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Claims (13)

[Claims]
1. A system for optically transmitting a data signal from a master station to one or more slave stations, wherein the master station is a pre-modulation means for pre-modulating a pilot signal with the data signal,
And optical modulation means for modulating carrier light with the output signal of the pre-modulation means, each of the slave stations being an optical demodulation means for demodulating the output light of the optical modulation means, and an electrical signal output from the optical demodulation means. An electric demodulation means for demodulating the data into a data signal and a pilot signal, a clock reproduction means for reproducing a clock based on the pilot signal output from the electric demodulation means, Optical transmission comprising: a first carrier wave generating means for generating one carrier wave; a modulating means for modulating the first carrier wave outputted from the first carrier wave generating means with a data signal outputted from the electric demodulating means. system.
2. The data signal is a binary baseband digital data signal, the pilot signal has a higher frequency than the data signal, and the pre-modulation performed by the pre-modulation means is such that the data signal is a mark. The optical transmission system according to claim 1, wherein the modulation is such that a pilot signal is output during the period and the data signal is not output during the space period.
3. A method for optically transmitting a data signal from a master station to one or more slave stations, wherein the master station premodulates a pilot signal with a data signal and carries the signal obtained by premodulation. Each slave station modulates light, demodulates the modulated light transmitted from the master station, demodulates the electric signal obtained by demodulation to separate the data signal and the pilot signal, and separates them. A clock is regenerated based on the obtained pilot signal, a first carrier wave is generated according to the regenerated clock, and the generated first carrier wave is modulated by a data signal obtained by separation. The optical transmission method.
4. A master station for optically transmitting a data signal to one or more slave stations, comprising: pre-modulation means for pre-modulating a pilot signal with the data signal.
And optical modulation means for modulating carrier light with an output signal of the pre-modulation means, wherein the data signal is a binary baseband digital data signal, and the pilot signal has a higher frequency than the data signal, The pre-modulation performed by the pre-modulation means is a modulation which outputs a pilot signal during a mark period of a data signal and does not output a pilot signal during a mark period of a data signal.
5. The master station according to claim 4, wherein the optical modulator stops outputting the carrier light when there is no data signal to be transmitted and when the data signal is a space.
6. The master station according to claim 4, wherein the pilot signal is a signal having a waveform capable of reproducing a clock based on the pilot signal.
7. The master station according to claim 6, wherein the pilot signal is a sine wave having a constant frequency.
8. The master station according to claim 6, wherein the pilot signal is a square wave having a constant frequency.
9. The master station according to claim 6, wherein the pilot signal is a signal having predetermined information.
10. A slave station for receiving a data signal optically transmitted from a master station, wherein the master station premodulates a pilot signal with the data signal and carries the signal obtained by the premodulation. Modulated light obtained by modulating light is transmitted, optical demodulation means for demodulating the modulated light transmitted from the master station, data signal and pilot by demodulating the electrical signal output from the optical demodulation means An electric demodulation unit for separating the signal into a signal, a clock reproduction unit for reproducing a clock based on a pilot signal output from the electric demodulation unit, and a first carrier for generating a first carrier wave according to the clock output from the clock reproduction unit A carrier wave generating means, and a modulating means for modulating the first carrier wave output from the first carrier wave generating means with the data signal output from the electrical demodulating means. .
11. The electric demodulating means divides the electric signal output from the optical demodulating means into two parts, and removes a high frequency component from one signal obtained by the two branching parts to obtain data. A high-frequency removing means for extracting only a signal, and a low-frequency removing means for removing a low-frequency component from the other signal obtained by the branching means branching into two to extract only a pilot signal. Item 10
The child station described in.
12. The slave station according to claim 11, further comprising means for converting an output signal of the modulating means into a radio wave and radiating it into the air.
13. A second carrier generating means for generating a second carrier according to a clock output from the clock reproducing means, an output signal of the modulating means, and a second output from the second carrier generating means. 12. The slave station according to claim 11, further comprising: a mixing unit that mixes with the carrier wave of, and a unit that converts an output signal of the mixing unit into a radio wave and radiates it into the air.
JP2002035640A 2002-02-13 2002-02-13 Optical transmission system for wireless base station Pending JP2003244750A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007173960A (en) * 2005-12-19 2007-07-05 Nippon Telegr & Teleph Corp <Ntt> Radio communication system and signal distortion reducing method therefor
JP2010515313A (en) * 2006-12-27 2010-05-06 テレフオンアクチーボラゲット エル エム エリクソン(パブル) Link adaptation in wireless communication systems

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007173960A (en) * 2005-12-19 2007-07-05 Nippon Telegr & Teleph Corp <Ntt> Radio communication system and signal distortion reducing method therefor
JP2010515313A (en) * 2006-12-27 2010-05-06 テレフオンアクチーボラゲット エル エム エリクソン(パブル) Link adaptation in wireless communication systems

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