JP2989378B2 - Synchronization method of mobile communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization system for a mobile communication network, and more particularly to a synchronization system for a mobile communication network in which phase synchronization is established between a plurality of radio base stations constituting the mobile communication network.

2. Description of the Related Art In a cellular radio system for a mobile phone, a cellular phone, or the like, a plurality of radio base stations covering small zones are installed and operated, and a predetermined service area is secured as a total thereof. However, the signals transmitted and received by each base station are
Phase synchronization must be established. Therefore, phase synchronization control is performed between base stations.

[0003]

2. Description of the Related Art FIG. 6 is a block diagram showing a conventional mobile communication network. That is, the radio base stations B1 to Bn are respectively installed at the centers of the small zones 61 to 63, and each of the radio base stations B1 to Bn transmits a signal from the mobile communication exchange 64 within its own small zone 61 to 63. Mobile terminal device C1
1 to C1p, C21 to C2q, and Cn1 to Cnz, respectively. In addition, wireless transmission is performed in the reverse direction.
The exchange 64 is connected to a general telephone via a fixed terminal exchange (not shown).

[0006] A synchronization signal is transmitted from the exchange 64 to each of the radio base stations B 1 to Bn via a transmission line.
There is a difference in the arrival time of the synchronization signal due to the difference in the length of each transmission path connecting the wireless base stations B1 to Bn. For this reason, each of the radio base stations B1 to Bn corrects the synchronization signal with a preset delay correction value corresponding to the difference, aligns the phases, and synchronizes the phase with the corrected synchronization signal. Generated clock signals.

[0005] However, if a detour is established due to construction on the way of the transmission line, etc., the above correction is not always appropriate, so the above correction is considered to be roughly performed, and as described below, More precise phase synchronization is taken.

FIG. 7A is a diagram showing a synchronous network between radio base stations. One of the wireless base stations B1 to Bn shown in FIG. 6 is defined as a reference base station M, and the other is defined as a dependent base station S. A reference synchronization signal is distributed from the reference base station M to each subordinate base station S, and each subordinate base station S generates a clock signal that is phase-synchronized with the reference synchronization signal so that accurate radio base station S Build a synchronous network. Since the transmission output of each radio base station is small, a plurality of synchronization signal distribution systems in which the reference synchronization signal is distributed from the reference base station M are configured, and the synchronization signals of the upper stations are sequentially received and phase-synchronized with the synchronization signals. Generate a clock signal for the local station. For example, from the reference base station M to the dependent base stations S1, S2, S3,.
The first system, and from the reference base station M to the dependent base station S2
, A second system of S22, S23, S24,... As a result, the phase synchronization between the radio base stations B1 to Bn is finely adjusted.

[0007]

However, in a conventional synchronous network between wireless base stations, as shown in FIG.
For example, when an abnormality occurs in the clock signal of the dependent base station S1, the lower dependent base station cannot determine the abnormality of the clock signal of the dependent base station S1, so that the dependent base stations S2 and S2 follow the abnormal clock signal. There is a problem in that S3 makes an erroneous synchronization adjustment, and each radio base station makes an erroneous synchronization adjustment in any way.

The present invention has been made in view of such a point, and even if an abnormality occurs in a clock signal of a radio base station in the middle of a synchronization signal distribution system, it does not hinder synchronization adjustment of a lower radio base station. It is an object of the present invention to provide a synchronization system for a mobile communication network in which the communication is not performed.

[0009]

According to the present invention, in order to achieve the above object, as shown in FIG. 1, an exchange 1 for mobile communication, and a synchronous signal delivered from the exchange 1 with a delay time. In a mobile communication network composed of a plurality of radio base stations 2 to 8, each clock signal generating means of the plurality of radio base stations 2 to 8, a plurality of synchronization signal distribution systems, and a first phase difference detecting means 4b , A second phase difference detecting means 4c and a synchronization control means 4d.

The clock signal generating means of each of the plurality of radio base stations 2 to 8 corrects the phase of the synchronization signal distributed from the exchange 1 by the delay time in the transmission path, and according to the corrected synchronization signal, Each generates a clock signal. The reference synchronization signal base station 2 of the plurality of wireless base stations 2 to 8 removes the synchronization signal based on a clock signal from its own clock signal generating means, excluding itself. Used to distribute to ~ 8. The first phase difference detection means 4b is provided in the lower radio base station 4 of the first synchronization signal distribution systems 2, 3, 4, and 5 of the plurality of synchronization signal distribution systems, and is sent from the upper radio base station 3. The phase difference between the synchronized signal thus generated and the clock signal generated by the clock signal generating means 4a of the lower radio base station 4 is detected. The second phase difference detecting means 4c is provided in the lower radio base station 4 and, when the phase difference detected by the first phase difference detecting means 4b is larger than a predetermined value, a second synchronization signal adjacent to the lower radio base station 4 A synchronizing signal sent from the adjacent radio base station 7 of the distribution system 2, 6, 7, 8;
The phase difference from the clock signal generated in a is detected. The synchronization control unit 4d evaluates the phase difference detected by the first phase difference detection unit 4b and the phase difference detected by the second phase difference detection unit 4c by majority logic processing, and based on the result, the clock of the lower radio base station 4 The synchronization control of the signal generating means 4a is performed.

[0011]

With the above arrangement, in FIG. 1, each of the radio base stations 2 to 8 normally performs transmission and reception as a radio base station based on a clock signal from its own clock signal generating means. At the same time, the first phase difference detecting means 4 of the lower radio base station 4
b detects the phase difference between the synchronization signal sent from the upper radio base station 3 and the clock signal generated by the clock signal generator 4a of the lower radio base station 4 at all times. When the detected phase difference is larger than the predetermined value, the second phase difference detecting means 4c sets the adjacent radio base stations 7 of the second synchronization signal distribution systems 2, 6, 7, 8 adjacent to the lower radio base station 4. And a clock signal generated by the clock signal generation means 4a of the lower radio base station 4 from the synchronization signal sent from the base station. During this time, the lower wireless base station 4 continues to transmit and receive as the wireless base station based on the clock signal spontaneously generated by the clock signal generator 4a.

The synchronization control means 4d evaluates the phase difference detected by the first phase difference detection means 4b and the phase difference detected by the second phase difference detection means 4c by majority logic processing. It is determined whether the clock signal is caused by the clock signal abnormality of the radio base station 4 or the clock signal of the radio base station higher than the lower radio base station 4. If it is due to an abnormality in the lower radio base station 4, the clock signal generating means 4 a of the lower radio base station 4 controls so as to follow the synchronization signal of the upper radio base station 3, and If it is caused by an abnormality of the radio base station, control is performed so as to follow the synchronization signal of the adjacent radio base station 7.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a synchronous network between radio base stations,
The operation principle of the present embodiment will be described with reference to FIG.

First, as shown in FIG. 2A, one of a plurality of radio base stations constituting a synchronous network is connected to a reference base station M.
And the rest are referred to as the dependent base station S. A plurality of synchronization signal distribution systems in which the reference synchronization signal is distributed from the reference base station M are configured, that is, from the reference base station M to the dependent base stations S1, S
, S3,..., And second base stations S21, S22, S23, S24.
A system is configured to receive the synchronization signal of the upper station in order, and to generate a clock signal of the own station which is normally synchronized in phase with the received synchronization signal. For example, the dependent base station S2 generates its own clock signal that is phase-synchronized with the synchronization signal of the upper station S1. Upon generation of this clock signal, the dependent base station S2 always monitors the phase difference between the synchronization signal of the upper station S1 and its own clock signal.

As shown in FIG. 2B, when an abnormality occurs in the clock signal of the upper station S1, the phase difference detected by the dependent base station S2 increases. The dependent base station S2 detecting this large phase difference runs the clock signal by itself and receives the synchronization signal of the adjacent station S22 of the adjacent second synchronization signal distribution system. And the adjacent station S2
The phase difference between the synchronization signal of the second station and its own clock signal is detected, and in the case of the abnormal clock signal of the upper station S1, the phase difference between the synchronization signal of the adjacent station S22 and its own clock signal is not large. Therefore, after confirming the small phase difference, the dependent base station S2 generates a clock signal following the synchronization signal of the adjacent station S22.

As described above, even if an abnormality occurs in the clock signal of the radio base station S1 in the middle of the synchronization signal distribution system,
This makes it possible to prevent trouble in synchronization adjustment of the lower wireless base stations S2 and S3.

If the phase difference between the synchronization signal of the adjacent station S22 and its own clock signal is large, the own base station S2 determines that its own clock signal is abnormal, and the dependent base station S2 first synchronizes with the host station S1. A clock signal is generated following the signal. In other words, even when a phase difference occurs between the slave station and the synchronization signal of the upper station S1, the dependent base station S2 does not immediately follow the synchronization signal of the upper station S1, but instead follows the synchronization signal of the upper station S1.
After confirming also the phase difference from the synchronization signal of No. 22, it follows the synchronization signal of the upper station S 1.

FIG. 3 is a diagram showing how a synchronization signal is transmitted and received between radio base stations in the synchronization network shown in FIG.
FIG. 3A corresponds to FIG. 2A, and FIG.
This corresponds to (B). That is, each radio base station S1, S
2, S21, S22, and S23 correspond to the mobile terminal device C (FIG. 6).
In addition to the transmitting and receiving device for transmitting and receiving the main signal to and from the base station, the receiving unit R for receiving the synchronization signal included in the main signal transmitted from the upper station and the adjacent station is provided. Then, for example, the receiving unit R2 of the dependent base station S2
1 (FIG. 3A), but if a large phase difference is detected, the receiving unit R2 of the dependent base station S2
Receives the synchronization signal of the adjacent station S22 (FIG. 3B).

FIG. 4 is a block diagram showing the internal configuration of the radio base station. That is, the main signal transmitting / receiving unit 41 for transmitting / receiving a main signal to / from a mobile terminal device (not shown) includes:
The exchange 30 (which does not constitute a radio base station) is connected, and the clock signal generator 42 is connected. The clock signal generator 42 normally corrects the synchronization signal supplied from the exchange 30 by a delay time in the transmission line, and synchronizes the phase with the synchronization signal supplied to another radio base station. .
Then, a clock signal synchronized with the corrected synchronization signal is generated and output to the main signal transmitting / receiving unit 41.

On the other hand, receiving section 43 receives a synchronization signal included in a main signal transmitted from an upper station or an adjacent station.
The receiving station designating section 44 is a designating section for designating which of the upper station and the adjacent station the receiving section 43 should receive, and usually designates to receive the synchronization signal of the upper station. The phase difference detection unit 45 detects a phase difference between the synchronization signal received by the reception unit 43 and the clock signal output by the clock signal generation unit 42, and outputs the same to the abnormality determination unit 46.

The abnormality judging section 46 firstly outputs the phase difference detecting section 4
5, the phase difference between the synchronization signal of the upper station and the clock signal of the clock signal generator 42 is compared with a predetermined value. If the phase difference is equal to or smaller than the predetermined value, the clock signal generator 42
However, a clock signal is generated based on the synchronization signal from the exchange 30 as usual. The predetermined value is set to the maximum value in a range where the phase fluctuation of the synchronization signal (clock signal) is allowed. On the other hand, when the phase difference is larger than the predetermined value, the clock signal generation unit 42 continues to oscillate the clock signal until immediately before (so-called self-running state) and the reception station designation unit 44 receives the clock signal. A change command is issued, and the receiving station designating section 44 instructs the receiving section 43 to receive the synchronization signal of the adjacent station.

Therefore, this time, the phase difference detection unit 45
Detects the phase difference between the synchronization signal of the adjacent station and the clock signal of the clock signal generation section 42, and the abnormality determination section 46 determines the phase difference between the synchronization signal of the adjacent station and the clock signal of the clock signal generation section 42. Compare with value. As a result, if the phase difference is larger than the predetermined value, the abnormality determining unit 46 determines that the own clock signal is abnormal, causes the receiving station specifying unit 44 to specify the reception of the upper station, and sets the clock signal generating unit 42
In response, a clock signal is generated in synchronization with the synchronization signal of the upper station. That is, the clock signal generator 4
2, a phase difference from the synchronization signal of the higher-level station is sent via the abnormality determination unit 46, and the clock signal generation unit 42 controls the phase of the clock signal so as to reduce this difference.

On the other hand, if the phase difference is equal to or less than the predetermined value, the abnormality judging section 46 judges that the clock signal of the upper station is abnormal, and notifies the clock signal generator 42 of the phase difference with the synchronization signal of the adjacent station. Then, the clock signal generator 42 controls the phase difference to decrease so as to generate a clock signal synchronized with the synchronization signal of the adjacent station. Until the clock signal of the upper station is determined to be abnormal, the clock signal generator 42 is in a self-running state.
By constructing a stable oscillation circuit,
The operation of the main signal transmitting / receiving unit 41 during that time can be stabilized. Further, the abnormality judging section 46 informs the central monitoring device provided in the exchange 30 that the clock signal of the upper station (not always immediately higher) has an abnormality and synchronizes with the adjacent synchronization signal distribution system. The fact that the network has been changed is reported as a report signal with its own code.

The central monitoring device of the switching center 30 specifies a faulty base station based on a broadcast signal from each radio base station, restricts transmission and reception to the specified radio base station, or performs early restoration. Or command.

FIG. 5 is a timing chart for explaining how the abnormality judging section 46 judges the abnormality of the own station or the upper station. (A) and (D) show clock signals generated by the clock signal generator 42 of the own station.
(E) shows a synchronization signal from the upper station, and (C) and (F)
Indicates a synchronization signal from an adjacent station. (A), (B),
(C) explains the own station abnormality, and (D), (E),
(F) explains the upper station abnormality.

First, the clock signal of the own station is the signal 51,
When an error occurs as in 52, a large phase difference 53 occurs between the synchronization signal from the upper station and a large phase difference 54 also occurs between the synchronization signal from the adjacent station. Therefore,
Conversely, if the phase difference 53 and the phase difference 54 are detected, it can be determined that the clock signal of the own station has an abnormality.

Next, the synchronizing signal from the upper station is the signal 5
In the case of an abnormality such as 5, 56, a large phase difference 57 occurs between the clock signal of the own station and the clock signal of the own station, but the phase difference 58 between the synchronization signal from the adjacent station and the clock signal of the own station is allowed to vary. Not more than the value. Therefore, conversely, the phase difference 5
Even if 7 is detected, when the phase difference 58 is smaller than the allowable variation value, it can be determined that the synchronization signal (clock signal) of the upper station has an abnormality.

In the above embodiment, the clock signal generator 42 generates a clock signal in synchronization with the synchronization signal of the upper station when the abnormality determiner 46 determines that the own station is abnormal. When the phase difference with the higher-level station is larger than a certain discrimination value, the central monitoring device of the exchange 30 is notified of the occurrence of a special abnormality in the local station, and the central monitoring device issues a notification to the local station. Restrictions on transmission and reception may be added.

In the above embodiment, the abnormality judging section 46
Compares the phase difference output from the phase difference detection unit 45 with a predetermined value, and outputs a command to the clock signal generation unit 42 and the receiving station designation unit 44 immediately if the phase difference is once larger than the predetermined value. However, a command may be output to the clock signal generator 42 and the receiving station designator 44 for the first time when the phase difference is greater than the predetermined value a predetermined number of times.

[0030]

As described above, according to the present invention, the phase difference between the synchronization signal of the upper radio base station and the clock signal of the lower radio base station is detected, and when the detected phase difference is larger than a predetermined value, The phase difference between the synchronization signal of the adjacent radio base station and the clock signal of the lower radio base station is detected. The detected phase difference is evaluated by majority logic processing, and if it is determined that the clock signal of the upper radio base station is abnormal, the lower radio base station follows the synchronization signal of the adjacent radio base station. Control. Thereby, even if an abnormality occurs in the clock signal of the wireless base station in the middle of the synchronization signal distribution system, it is possible to prevent the synchronization adjustment of the lower wireless base station from being affected.

Further, since the faulty station can be specified by the central monitoring device, the maintenance and monitoring of the communication network becomes easy. Further, since the failure does not spread to a radio base station lower than the failed station, the operation efficiency of the communication network can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating a synchronous network between wireless base stations.

FIG. 3 is a diagram illustrating a state of transmission and reception of a synchronization signal performed between wireless base stations in a synchronization network.

FIG. 4 is a block diagram illustrating an internal configuration of a wireless base station.

FIG. 5 is a timing chart illustrating a method of determining a local station abnormality or an upper station abnormality performed by the abnormality determining unit.

FIG. 6 is a block diagram showing a conventional mobile communication network.

FIG. 7 is a diagram showing a synchronous network between wireless base stations.

[Explanation of symbols]

 Reference Signs List 1 exchange station 2 radio base station (reference synchronization signal base station) 3 (upper) radio base station 4 (lower) radio base station 4a clock signal generating means 4b first phase difference detecting means 4c second phase difference detecting means 4d synchronization control Means 5 Radio base station 6 Radio base station 7 (adjacent) radio base station 8 Radio base station 2,3,4,5 First synchronization signal distribution system 2,6,7,8 Second synchronization signal distribution system

Claims (6)

(57) [Claims] 1. A mobile unit comprising: a mobile communication switching center (1); and a plurality of radio base stations (2 to 8) to which a synchronization signal is distributed with a delay time from the switching center (1). In the synchronization method of a communication network, each of the plurality of wireless base stations (2 to 8) generates a clock signal in accordance with the corrected synchronization signal by performing phase correction on the synchronization signal for the delay time. Means; and a reference synchronization signal base station (2) of the plurality of wireless base stations (2 to 8) excluding the synchronization signal based on a clock signal from its own clock signal generating means, excluding itself. A plurality of synchronization signal distribution systems used for distribution to (3 to 8); and a lower radio base station of a first synchronization signal distribution system (2, 3, 4, 5) of the plurality of synchronization signal distribution systems. Station (4), upper radio base First phase difference detection means (4b) for detecting a phase difference between the synchronization signal sent from the station (3) and the clock signal generated by the clock signal generation means (4a) of the lower radio base station (4); A second synchronization unit which is provided in the lower radio base station (4) and is adjacent to the lower radio base station (4) when the phase difference detected by the first phase difference detection means (4b) is larger than a predetermined value. A synchronization signal transmitted from an adjacent radio base station (7) of the signal distribution system (2, 6, 7, 8), a clock signal generated by clock signal generation means (4a) of the lower radio base station (4), Phase difference detecting means (4) for detecting the phase difference of
c), the phase difference detected by the first phase difference detection means (4b) and the phase difference detected by the second phase difference detection means (4c) are evaluated by majority logic processing, and based on the result, the lower-order radio is evaluated. Synchronization control means (4d) for performing synchronization control of clock signal generation means (4a) of the base station (4); and a mobile communication network synchronization method. 2. The synchronization control means (4d) includes:
If both the phase difference detected by the phase difference detection means (4b) and the phase difference detected by the second phase difference detection means (4c) are larger than the predetermined value, the lower radio base station (4) becomes abnormal. And the phase difference detected by the first phase difference detecting means (4b) is larger than the predetermined value, but the phase difference detected by the second phase difference detecting means (4c) is equal to the predetermined value. If it is less than or equal to, the first synchronization signal distribution system (2, 2) higher than the lower wireless base station (4)
2. The mobile communication network synchronization system according to claim 1, wherein it is determined that there is an abnormality in the wireless base station of (3, 4, 5). 3. The clock signal generating means (4a) of the lower radio base station (4), when the synchronization control means (4d) determines that the lower radio base station (4) is abnormal, 3. The mobile communication network synchronization system according to claim 2, wherein a clock signal synchronized with the synchronization signal sent from the upper radio base station is generated. 4. The clock signal generating means (4a) of the lower radio base station (4) is controlled by the synchronization control means (4d) to output the first synchronization signal higher than the lower radio base station (4). When it is determined that the radio base station of the distribution system (2, 3, 4, 5) has an abnormality, the adjacent radio base station (7) of the second synchronization signal distribution system (2, 6, 7, 8) 3. The mobile communication network synchronization method according to claim 2, wherein a clock signal synchronized with the synchronization signal sent from the communication device is generated. 5. The synchronous control means (4d) is configured to, when detecting the abnormality, notify a content of the abnormality and an identification code of the own radio base station (4) to a monitoring control station. 3. The synchronization system for a mobile communication network according to claim 2, wherein 6. The monitoring and control station is configured to identify a faulty radio base station based on the notification, and to regulate transmission and reception of the specified faulty radio base station. The mobile communication network synchronization method according to claim 5.