JP2995967B2 - Mobile communication system - Google Patents

Abstract

PURPOSE:To relieve a stress exerted onto circuit components of each of base stations for phase synchronization operation by sufficiently measuring a delay time difference of a transmission line between two base stations even when a reception electric field intensity is weak in the simultaneously transmission of plural stations. CONSTITUTION:A phase difference measurement station 2 installed at a position able to sufficiently receive a radio wave from a radio base station such as a central station 1 and plural peripheral stations 3 always receives and decodes a 1st special signal sent from the radio base station at a prescribed time interval and outputs an instruction signal of phase synchronization to the central station 1 when the 1st special signal cannot be decoded and a 2nd special signal included in a radio wave from the central station 1 and the peripheral station 3 is received and decoded, and the decoded phase difference of the 2nd special signal is measured and sent to the central station 1. When the central station 1 receives an instruction signal of phase synchronization operation, the start and stop of the transmitter of each peripheral station 3 and its own station are controlled so that the phase difference measurement station 2 measures the phase difference and the phase difference is corrected in response to the phase difference sent from the phase difference measurement station 2.

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, and more particularly to a small zone mobile communication system in which a wide service area is formed by using a plurality of base stations.

[0002]

2. Description of the Related Art A mobile communication system uses a radio system between a base station and a terminal, and is characterized by having no alternative means. Since there is a limit to the frequency band that can be used in such a mobile communication system, effective use of radio frequency is indispensable to accommodate a large number of users and configure a system with good serviceability. One of the factors is the configuration of wireless zones, and when multiple small wireless zones are used to cover a wide service area, from the effective use of frequency, multiple wireless base stations installed in each small wireless zone are required. A method of simultaneously transmitting the same transmission radio waves is often used (Reference: "Basics of mobile communication", published by the Institute of Electronics, Information and Communication Engineers, section 7.4).

[0003] At this time, in order to secure required transmission quality in an area where the intensities of radio waves from a plurality of radio base stations are almost equal, it is necessary to synchronize the phases of signals transmitted from the radio base stations. In order to synchronize the phases between two base stations, the delay time of a transmission path between a station that sends out a signal (hereinafter referred to as a "central station") and each wireless base station is measured, and the delay times are all measured. It is necessary to delay the signal to the same radio base station as the central station. As a method of measuring the delay time, radio waves such as a radio wave of a reference radio base station (hereinafter, referred to as “reference station”) are received by another radio base station (hereinafter, referred to as “peripheral station”) and compared. It is common to use a line (reference: published by the Institute of Electronics, Information and Communication Engineers, "" mobile phone ", section 7.5). It is necessary to insert a delay circuit in the central office so that the delay time of the signal transmitted from the central office is longer than the delay time of the transmission path between the central office and each peripheral office.

FIG. 6 shows a configuration of a conventional small zone type mobile communication system. The system shown in FIG. 6 includes a central station 31 for transmitting a signal for phase synchronization, a reference station 32, and a peripheral station 33. Here, the reference station 32 and the peripheral station 33 are connected to the line transmission lines 34 and 35.
Are connected to the central office 31 via the respective terminals. In FIG. 6, reference numeral 36 denotes a transmitting antenna of the central office 31,
Reference numeral 37 denotes a reception antenna of the reference station 32, reference numeral 38 denotes a transmission antenna of the reference station 32, and reference numeral 39 denotes a modem (MO).
DEM).

FIG. 7 shows a configuration of the peripheral station 33. The peripheral station 33 includes a reception / control unit 41 and a transmitter 4
The reception control unit 41 includes an RF receiver 44 that receives and demodulates a radio wave arriving via the reception antenna 43, and a code decoding unit 45 that decodes a special signal included in the arriving radio wave. A phase comparator 46 for measuring a phase difference between the decoded special signals, and a phase comparator 46
A variable delay unit 47 into which a delay amount corresponding to the phase difference measured in is inserted, and a clock synchronization unit 49. In this figure, reference numeral 48 indicates a transmitting antenna.

FIG. 8 shows a timing chart of the phase difference measurement in the conventional system having such a configuration. A conventional phase difference measurement operation for phase synchronization will be described with reference to the timing chart of FIG.
The RF receiver 44 of the peripheral station 33 receives the radio wave (own local station radio wave) EW2 transmitted from its own transmitting antenna 48 via the receiving antenna 43 and the radio wave (reference station radio wave) EW1 transmitted from the reference station 32, respectively. The signal is demodulated, and the code decoding unit 45 decodes a special signal included in the received radio wave (accurately, a demodulated signal of the received radio wave). Then, the phase comparator 46
Then, as shown in FIG. 8, the received special signal S1 of the own station is received.
Is generated, the timing of the virtual special signal S2 is generated, the special signal S3 of the reference station 33 is compared with the timing received and demodulated by the RF receiver 44, and the phase difference A is measured. By measuring the phase difference A, that is, the delay time difference in this way, the delay time of the transmission path is equivalently measured.

Here, the radio wave E received by the RF receiver 44 is
Since the frequencies of W1 and EW2 are the same, FIG.
As shown by, when receiving the radio wave EW1 from the reference station 32, it was necessary to temporarily stop the output of the radio wave EW2 from the peripheral station 33 and receive the radio wave EW1 from the reference station 33. However, if the distance between the reference station 32 and the peripheral station 33 is long, or if there is an obstacle such as a mountain between the reference station 32 and the peripheral station 33, the RF receiver 44 installed in the peripheral station 33 will not be sufficient. In some cases, a receiving electric field cannot be obtained. In such a case, a high-gain receiving antenna is used, or an amplifier with good NF is inserted before the RF receiver 44 to increase the gain.

[0008]

However, in the above-mentioned conventional example, when the gain of the receiving antenna is limited or when the number of channels increases in the same system, the RF power becomes lower.
Even when an amplifier having a good NF is inserted in the front stage of the receiver, it is necessary to provide a narrow-band bandpass filter to reduce cross-modulation, so that there is a disadvantage that sufficient gain cannot be obtained. Further, in the above-described conventional system, phase correction operation is performed at regular intervals, so that starting and stopping of the transmitter of each base station exerts stress on circuit components and the like, which may cause a failure. I was

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the inconvenience of the prior art, and in particular, it is possible to sufficiently measure the delay time difference of a transmission line between two base stations even when the received electric field strength is weak, and to achieve phase synchronization. An object of the present invention is to provide a mobile communication system capable of reducing stress applied to circuit components of each base station for operation.

[0010]

A mobile communication system according to the present invention includes a central station provided in one of a plurality of small radio zones for transmitting a signal for phase synchronization between radio base stations, and the central station. Multiple peripheral stations installed in each of the small wireless zones other than the designated small wireless zone and connected to the central station via a line transmission line, and both the radio waves from the central station and the radio waves from the multiple peripheral stations are sufficient. And a phase difference measuring station installed at a position where it can receive signals and connected to the central office via a line transmission line. The phase difference measuring station always receives and decodes the first special signal transmitted from the plurality of radio base stations at fixed time intervals, and a central station when the first special signal cannot be decoded. And a function of receiving and decoding the second special signal contained in the radio waves from the central station and the peripheral stations, and determining the phase difference between the decoded second special signals. The transmitter has a function of measuring and transmitting the signal to the central station, and the transmitter of each peripheral station and its own station so that the phase difference measuring station can measure the phase difference when the central station receives a command signal for the phase synchronization operation. And a function to correct the phase difference according to the phase difference transmitted from the phase difference measurement station. With such a configuration, the object described above is to be achieved.

[0011]

The phase difference measuring station that measures the delay time difference (phase difference) of the transmission path between several base stations (between the central station and several peripheral stations)
The phase difference measuring station is located at a point where the received electric field of the radio wave from the central station and the received electric field of the radio wave from each peripheral station are sufficiently obtained (for example, an intermediate point). The delay time (phase difference) of the transmission line is measured, and the phase difference is corrected by the central station based on the measured phase difference, whereby the phases of the base stations are synchronized. In addition, the phase difference measuring station constantly monitors special signals transmitted from several base stations at regular intervals, and performs a phase correction operation only when the special signals cannot be decoded. The stress on the circuit components and the like due to the start and stop of the operation is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of an embodiment of the present invention. The embodiment shown in FIG. 1 includes a central station 1 provided in one of a plurality of small wireless zones and transmitting a signal for phase synchronization between wireless base stations, and a central station 1 other than the small wireless zone in which the central station 1 is provided. The three peripheral stations 3 installed in each of the small radio zones and separately connected to the central station 1 via the line transmission line 7, and both the radio waves from the central station 1 and the radio waves from the three peripheral stations 3 are sufficient. And a phase difference measuring station 2 connected to the central station 1 via a line transmission line 8 at a position where the signal can be received. In FIG. 1, reference numeral 4 denotes a transmitting antenna of the central station 1, and reference numeral 5 denotes a transmitting antenna of the peripheral station 3.

Here, the phase difference measuring station 2 always receives and decodes the first special signal transmitted from the central station 1 and the three peripheral stations 3 at fixed time intervals, and has a function of transmitting the first special signal. A function of outputting a command signal for a phase synchronization operation to the central station 1 when the decoding is not possible, and receiving and decoding a second special signal contained in radio waves from the central station 1 and the peripheral station 3; It has a function of measuring the phase difference between the respective second special signals and transmitting the same to the central office 1. Further, the central station 1 has a function of starting / stopping the peripheral stations 3 and its own transmitter so that the phase difference measuring station 2 can measure the phase difference when receiving the command signal of the phase synchronization operation. And a function of correcting the phase difference according to the phase difference transmitted from the phase difference measuring station 2.

This will be described in more detail.
As shown in FIG. 5, a clock synchronization unit 13, a code decoding unit 14 for decoding the control signal sent from the central office 1 via the line transmission line 7, and a signal from the code decoding unit 14 and the signal from the central office 1 And a transmitter 15 to be controlled.

As shown in FIG. 3, the phase difference measuring station 2 transmits the radio waves EW1 and EW1 arriving from the central station 1 and the three peripheral stations 3 through the receiving antenna 11, the receiving antenna 12, and the RF receiving radio wave combining unit 30, respectively. An RF receiver 17 that receives and demodulates the EW2, and a first special signal transmitted from the central station 1 and the three peripheral stations 3 at fixed time intervals and included in the demodulated wave of the arriving radio wave (see symbols S111 and S121 in FIG. 5). ), And a second special signal (see reference numeral 13 in FIG. 5) included in a radio wave EW1 from the central station 1 and radio waves EW2 from the three peripheral stations 3 and a first code decoding unit 18 which constantly receives and decodes the signals. A second decryption unit 19 for receiving and decrypting, and the second decryption unit 19
And a code for encoding a delay amount corresponding to the phase difference measured by the phase comparison unit 20 and transmitting the delay amount to the central office 1 And a decoding unit 23 that decodes a signal input from the central office 1 via the line transmission line 8 and outputs the decoded signal to the phase comparison unit 20, and clock synchronization circuits 21 and 22.

As shown in FIG. 4, the central station 1 decodes the respective delay amounts coded by the coding section 24 provided for the three peripheral stations 3 and constituting the phase difference measuring station 2. It includes three delay amount decoding units 26, three variable delay units 27 provided corresponding to the line transmission paths 7 to the respective peripheral stations 3 and into which the decoded delay amounts are inserted, and a clock synchronization unit 25. It is composed of 1 to 4, reference numeral 6 denotes a modulator / demodulator.

FIG. 5 shows a timing chart of the phase difference measurement in this embodiment. Here, FIG.
The operation of this embodiment will be described with reference to FIG.

In the phase difference measuring station 2, the radio wave transmitted from each radio base station is received by the RF receiver 17 and demodulated. The first code decoder 18 decodes the first special signal included in the received radio wave. In this case, as shown in FIG. 5A, the radio wave EW transmitted simultaneously from the central station 1 and the peripheral station 3
1 and EW2, the first special signal (see S111 and 121 in FIG. 5) can be decoded by the code decoder 18. However, if the phases of the signals included in the radio waves transmitted simultaneously from the central station 1 and the peripheral station 3 are shifted, the first special signal (see S112 and S122 in FIG. 5).
Cannot be decoded by the first code decoding unit 18.

At this time, the phase comparator 20 of the phase difference measuring station 2
Then, since the phases cannot be compared, a command signal for the phase synchronization operation is sent to the central station 1 via the encoder 24 and the line transmission line 8. The central station 1 receives the command signal of the phase synchronization operation and outputs a control signal to each of the peripheral stations 3 so that each of the transmitters 1
The transmission operation of No. 5 is stopped, and the peripheral station radio wave which becomes the interfering radio wave for the measurement of the central station radio wave is temporarily stopped as indicated by the reference symbol C in FIG. 5B. At this time, the phase difference measuring station 2 receives and demodulates the second special signal S13 from the central station 1 with the RF receiver 17 and decodes the second special signal S13 with the second code decoding unit 19.

Next, in the phase comparing section 20, the timing of the virtual second special signal S15 of the central station is generated as shown in FIG. 5C based on the received second special signal 13 of the central station. . In addition, the central station 1 temporarily suspends the radio wave from the local station (the radio wave of the central station 1), as indicated by the symbol D in FIG. 5B. At this time, the phase difference measuring station 2 receives and demodulates the second special signal S14 from the peripheral station 3 with the RF receiver 17, and decodes the second special signal S14 with the second code decoding unit 19.

The phase comparing section 20 compares the timing at which the second special signal S14 from the peripheral station 3 is received and demodulated with the timing of the virtual second special signal S15 of the central station described above. Phase difference (delay amount) shown in (C)
Measure A. The measured phase difference A is encoded by the encoding unit 24 and transmitted to the central office 1 via the line transmission line 8. Next, in the central station 1, the transmitted coded delay amount is decoded by the delay amount decoding unit 26, inserted into the variable delay unit 27, and the surrounding area where the phase difference is measured via the line transmission line 7. The signal is transmitted to the station 3 and the phase of the signal is synchronized. In this way, all phases can be synchronized by performing the phase synchronization operation on all the peripheral stations 3.

[0023]

As described above, according to the present invention, the phase difference measuring station is installed at a point where the received electric field strength from the central station and the received electric field strength from each peripheral station can be sufficiently obtained. , Even if the received field strength from the central office is weak
It is possible to sufficiently measure the delay time difference (phase difference) of the transmission path between the base stations (the central station and each peripheral station), and to cope with the cross modulation that occurs in the RF receiver when the number of channels increases in the same system. However, since the desired wave (D wave) becomes stronger and the interfering wave (U wave) becomes weaker, the characteristics are improved, and it is sufficient to provide only a phase difference measuring station with a device used for phase difference measurement. There is no need to provide each station separately,
An unprecedented superior mobile communication that can reduce the stress on circuit components and the like due to the start and stop of the transmitter of each base station because the phase correction operation is performed only when the phase of the signal from each base station is shifted. A system can be provided.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration of a peripheral station in FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a phase difference measuring station in FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of a central office in FIG. 1;

FIG. 5 is an operation explanatory diagram of the embodiment of FIG. 1;

FIG. 6 is a block diagram showing a configuration of a conventional mobile communication system.

FIG. 7 is a block diagram showing a configuration of a conventional peripheral station.

FIG. 8 is a diagram showing a conventional phase difference measuring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central station 2 Phase difference measuring station 3 Peripheral station 7 Line transmission line 8 Line transmission line 18 First code decoding unit 19 Second code decoding unit 20 Phase comparison unit 24 Encoding unit 27 Delay amount decoding unit 28 Variable delay unit

Claims (2)

(57) [Claims] 1. A central station provided in one of a plurality of small wireless zones for transmitting a signal for phase synchronization between wireless base stations, and a small wireless zone other than the small wireless zone in which the central station is provided. And a plurality of peripheral stations connected to the central station via a line transmission line, and a line transmission line installed at a position where both the radio waves from the central station and the radio waves from the plurality of peripheral stations can be sufficiently received. And a phase difference measuring station connected to the central station via the first base station, wherein the phase difference measuring station is transmitted from the plurality of radio base stations at regular time intervals.
A function of constantly receiving and decoding the special signal, and outputting a phase synchronization operation command signal to the central station when the first special signal cannot be decoded, and including the command signal in the radio waves from the central station and peripheral stations. A second special signal received and decoded, and a function of measuring the phase difference between the decoded second special signals and transmitting the second special signal to the central office. A function of controlling the start / stop of each of the peripheral stations and its own transmitter so that the phase difference measuring station can measure the phase difference when receiving the command signal of the synchronous operation; and A mobile communication system having a function of correcting the phase difference according to the transmitted phase difference. 2. A first code decoding section, wherein the phase difference measuring station constantly receives and decodes a first special signal transmitted from the plurality of radio base stations at fixed time intervals, and A second code decoding unit that receives and decodes the radio wave and a second special signal included in the radio waves from the plurality of peripheral stations; and a second code decoding unit that decodes the second special signal decoded by the second code decoding unit. A phase comparison unit that measures a phase difference, and includes an encoding unit that encodes a delay amount corresponding to the phase difference measured by the phase comparison unit and transmits the delay amount to the central station,
The central station decodes the encoded delay amount, a delay amount decoding unit, and a variable delay unit that is provided corresponding to the line transmission path to each of the peripheral stations and is inserted with the decoded delay amount. The mobile communication system according to claim 1, wherein the mobile communication system is configured to include: