JPH0955978A - Method and apparatus for radio frame synchronization between base stations - Google Patents

Abstract

(57) Abstract: Regarding a radio frame synchronization between base stations in a digital mobile communication system, a specific service is provided without using a communication signal transmitted from a mobile device of a subscriber in a radio zone of the base station. The purpose is to automatically perform radio frame synchronization between all base stations in the area. SOLUTION: One of base stations to be synchronized is defined as a reference station, and the other is set as a coordinating station, and the reference station transmits / receives signals by connecting a radio line to a test mobile device included in the own station. , The adjustment station intercepts a communication signal between the reference station and the test mobile unit, detects the radio frame phase of the reference station from the communication signal, and measures the phase difference of the radio frame between the reference station and the adjustment station. Based on the phase difference obtained by the above procedure, software control is performed so as to adjust the radio frame phase of the adjusting station so as to be in phase synchronization with the radio frame of the reference station.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for radio frame synchronization between base stations in a digital mobile communication system.

In a digital mobile communication system such as a car phone / mobile phone system, radio frame synchronization among all base stations is performed in order to improve the line quality. By synchronizing radio frames between base stations, the processing time for channel switching between base stations can be shortened, and the effect of suppressing radio wave interference can be obtained.

[0003]

Radio frame synchronization between two base stations in a mobile communication system adopts a method in which the phase of the radio frame of one base station is matched with the phase of the radio frame of the other base station. In the following description, a base station that serves as a reference of the radio frame phase is referred to as a reference station, and a station whose radio frame phase is adjusted according to the reference station is referred to as an adjustment station.

An example of conventional radio frame synchronization between base stations will be specifically described with reference to FIG. Monitoring device OMC in the figure
Can monitor and control the base stations A and B via the exchange MSC and the base station controller BCE. The system maintenance person performs radio frame phase synchronization between the base stations A and B by manually performing the following procedure from the monitor / control console of the monitor OMC. In this example, the base station A is the reference station and the base station B is the coordinating station.

Phase difference measurement When the communication channel between the base station A and the mobile station MS in the radio zone is in a communication state (a state in which a radio wave of the frequency is transmitted from the mobile station MS), the base station B intercepts the uplink speech channel from the mobile station MS to the base station A. Then, the base station B compares the phase of the synchronization word between the intercepted communication channel of the base station A and the communication channel of its own station, and determines how much phase difference there is in a symbol unit (1 symbol = 2 bits). To measure. Phase Adjustment FIG. 10 is a diagram showing an example of phase adjustment of a radio frame between the base stations A and B. 10A is a radio frame of an uplink communication channel from the mobile station MS to the base station A, FIG. 10B is a radio frame of a communication channel of the base station B, and d is a phase difference measured by the procedure. . Base station B is shown in FIG.
As shown in (c), the phase is adjusted by shifting the phase of the wireless frame of its own station by d and matching the wireless frame of the base station A with the synchronization word.

FIG. 11 is a diagram showing in detail the sync word portion of the radio frame of the base station B before and after adjustment. In this example, the phase adjustment is performed by shifting the sync word by two symbols. The actual phase adjustment operation is, for example, the phase amount that can be changed by one adjustment is ± 3 symbols, and the radio frame phase of the communication channel is set so that the phase difference of the synchronization word between base stations is within ± 1 symbol. Adjust.

Radio frame synchronization between all base stations within a specific service area of a mobile communication system
First, the above procedure is performed between any two base stations adjacent to the wireless zone, using either one as a reference station, and thereafter, the adjusted base station is the reference station, and the adjacent unadjusted base station is the adjustment station. , The procedure is repeated until the radio frame phases of all the base stations in the service area are adjusted.

[0008]

According to the conventional method, the above procedure cannot be executed unless there is a mobile station in communication within the radio zone of the reference station at the time of measuring the phase difference. In addition, all the above procedures were performed manually by the system maintainer from the supervisory control console, so it took a considerable amount of time and effort to synchronize the radio frames among all the base stations in the area, and it was not efficient. .

The present invention has been made in view of the above problems, and makes it possible to perform radio frame synchronization between base stations regardless of the presence / absence of a mobile station in communication within the radio zone of the reference station, The purpose is to implement radio frame synchronization between base stations within a service area quickly and reliably by automating the procedure of phase difference measurement and phase adjustment.

[0010]

FIG. 1 is a diagram illustrating the principle of the present invention. In order to solve the above-mentioned problems, the present invention provides a radio frame synchronization method between base stations for performing phase synchronization of radio frames between base stations of a digital mobile communication system, wherein one of the base stations to be synchronized is Reference station 6
0 and the other are defined as adjustment stations 61, and the reference station 60 connects a radio line to the test mobile unit 62 of its own station to transmit and receive signals, and the adjustment station 61 also moves the reference station 60 and the test mobile station. The communication signal with the device 62 is intercepted, the radio frame phase of the reference station 60 is detected from the communication signal, and the reference station 6
The phase difference of the radio frame between 0 and the adjusting station 61 is measured, and the radio frame phase of the adjusting station 61 is adjusted based on the phase difference obtained by the above procedure so as to be in phase synchronization with the radio frame of the reference station 60. A method of synchronizing radio frames between base stations is provided.

The present invention also provides an inter-base station radio frame synchronizer 50 for implementing the above method. The inter-base station radio frame synchronization device 50 includes a management unit 51 and a phase adjustment unit 52. The management unit 51 has one of the base stations to be synchronized as the reference station 60 and the other as the adjustment station 61.
, And requests the reference station 60 to connect and receive a signal by connecting a wireless line between the reference station 60 and the test mobile unit 62 included therein. The communication signal between the reference station 6 and the base station 6 and detects the radio frame phase of the reference station 60 from the communication signal.
It is requested to measure the phase difference of the radio frame between 0 and the adjusting station 61 and return the measured phase difference. Phase adjuster 5
2 transmits a radio frame phase adjustment instruction to the adjustment station 61 so that radio frame phase synchronization can be established between the reference station 60 and the adjustment station 61 based on the phase difference returned from the adjustment station 61.

Further, the inter-base station radio frame synchronizer 50
When the radio frame phase synchronization is established between the reference station and the coordinating station, the coordinating station is used as a new reference station, and another base station that has not yet been synchronized is used as the coordinating station to repeat the inter-base station synchronization in order to perform mobile communication. The management unit 51 further includes a synchronization order storage unit 53 that stores an inter-base station synchronization order such that radio frame phase synchronization can be achieved among all base stations within a predetermined area of the system, and the management unit 51 reads the base stations from the synchronization order storage unit 53. The radio frame phase synchronization between the base stations may be sequentially controlled according to the inter-synchronization order.

The inter-base station radio frame synchronizer 50 described above.
The operation will be described step by step with reference to FIG. The dotted lines with arrows in the figure show the flow of control or information, and the numbers added to each dotted line correspond to the numbers of the procedures described below.

Inter-base station radio frame synchronizer 50
However, for example, when it is started by a manual operation of a maintenance person (or automatically by a timer), the management unit 51 reads out the inter-base station synchronization order from the synchronization order storage unit 53, and based on that, the reference station 60 and the adjustment station 61 are connected. Establish. However, in the case of a configuration that does not include the synchronization order storage unit 53, the reference station 60 and the adjustment station 61 are determined by a manual operation of a maintenance person, for example. The management unit 51 uses the test mobile unit 62 for the reference station 60.
Request to communicate with. The reference station 60 connects a radio line to the test mobile unit 62 to send and receive signals. The management unit 51 requests the adjustment station 61 to measure the phase difference of the radio frame with the reference station 60. The coordination station 61 intercepts communication signals between the reference station 60 and the test mobile unit 62. The adjustment station 61 detects the radio frame phase of the reference station 60 from the intercepted communication signal, measures the phase difference of the radio frame between the reference station 60 and the adjustment station 61, and returns the measured phase difference to the phase adjustment unit 52. . Based on the returned phase difference, the phase adjustment unit 52 sends a radio frame phase adjustment instruction to the adjustment station 61 so that the radio frame phase synchronization between the reference station 60 and the adjustment station 61 is established. The adjusting station 61 adjusts the phase of the wireless frame of the own station according to the phase adjusting instruction from the phase adjusting unit 52.

After that, the above procedures (1) to (3) are repeatedly executed while changing the reference station and the coordinating station in accordance with the inter-base station synchronization order read from the synchronization order storage unit 53.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Normally, each base station of a mobile communication system is equipped with a test mobile device (TTR), and the monitoring device causes communication between the base station and the test mobile device.
Various tests can be performed for each base station.

In the radio frame synchronization between the base stations according to the embodiment of the present invention, a base station sets a call state with a test mobile device of its own station, and an uplink call channel in the call state is set to another base station. By monitoring by the station, the phase difference of the radio frame between both base stations is measured and the phase adjustment based on it is performed. In order to put a certain communication channel of the base station into a communication state, for example, the following test may be performed.・ ATM (Automatic line characteristic test) ・ TID (TTR incoming call connection test) ・ TOD (TTR outgoing call connection test) ・ TTR-TEL pull-in test Among these, TID is the most suitable for holding the call connection state at the set time Test or TOD test. Here, the TID test will be described as a representative.
It can be performed using either the ID test or the TOD test.

FIG. 2 is a diagram showing an apparatus configuration and method for carrying out the TID test. In order to carry out the TID test, first, as shown in FIG. 2 (a), the system maintenance person performs settings such as selection of a base station and a communication channel from the supervisory control console of the monitoring device OMC, and the selection is made accordingly. The communication channel between the selected base station and the test mobile device becomes the communication state.
Then, the bit error measurement pattern transmitted by the bit error measurement device in the monitoring device OMC arrives at the test mobile device via the base station. Next, as shown in FIG. 2 (b), the test mobile station transmits the received bit error measurement pattern to the base station as a response, and the bit error measurement device receives the returned bit error measurement pattern. To do. The bit error measuring device confirms the bit error rate by comparing the bit error measurement patterns at the time of transmission and at the time of reception.

FIG. 3 is a diagram showing an outline of a system configuration and an inter-base station radio frame synchronization method according to an embodiment of the present invention. In the present embodiment, the mobile station MS in the conventional example described in FIG.
Instead, a test mobile unit TTR is used. Also,
In reality, many base stations are controlled under the control of the base station controller BCE, but only two base stations A and B are shown in the figure. In order to perform radio frame synchronization between the base stations A and B using the base station A as a reference station and the base station B as a coordinating station, first, the TID for the base station A is controlled by the monitoring device OMC.
Conduct the test. Since the base station B is in a position where it can receive the uplink communication channel from the test mobile unit TTR to the base station A (for example, the base station B has a radio zone adjacent to the base station A), this uplink communication channel Can be monitored. After that, as in the case of the prior art, the monitoring device O
Under the control of the MC, the base station B measures the radio frame phase difference between the base stations A and B and performs the phase adjustment based on the measured radio frame phase difference.

According to this method, it is possible to solve the problem of the prior art that radio frame synchronization between base stations cannot be performed unless there is a mobile station in communication within the radio zone of the reference station. The system-maintenance person can perform the radio frame synchronization between the base stations by this method by manual operation from the supervisory control console, but if software for automatic processing is installed in the monitoring device OMC, system maintenance can be performed. It is possible to automatically carry out at any time according to a person's activation command or at a time preset in the timer.

Next, a method for adjusting the radio frame phase of all base stations within a specific service area will be described.
FIG. 4 illustrates base stations (A, B, C1 to C2, D1 to D4, E1 to E) subordinate to the base station control device BCE in the embodiment.
FIG. 6 is a diagram showing an example of a service area configured by wireless zones of No. 6, F1 to F4) and an order of wireless frame synchronization performed between these base stations. For example, when trying to match the phases of the radio frames of all base stations in this service area with the base station A, first, the base station A is set as the reference station and the base station B is set.
Is used as an adjusting station to adjust the phase of base station B (number in the figure), and then base station B is used as a reference station and base stations C1 and C2 are used as adjusting stations to perform the phase adjustment of base stations C1 and C2 (see the figure). No.), etc., and gradually expand the phase-adjusted range. In this example, if the phase adjustment is performed in the order from the number shown in the figure, all the base stations in the service area can be efficiently phase-synchronized.

FIG. 5 is a tree diagram showing the order of phase adjustment of the base station shown in FIG. The data which defines the order in which the phase adjustment of all base stations in the service area can be performed most efficiently is held in advance in the monitoring device OMC, and the software of the monitoring device OMC follows the phase according to this data. By performing the adjustment order control, quick and reliable radio frame synchronization between base stations becomes possible.

Further, from the monitoring device OMC to the TID of the reference station
When controlling the / TOD test, it is necessary to select a call channel to be used for the test, or change to another call channel when the selected call channel cannot be put into a call state. However, for example, in the case of a service area having a sector cell configuration, the number of communication channels differs for each sector. Therefore, in order to automate the above control by software, a communication channel management table for each base station is provided in the monitoring device OMC and selectable. Information about different call channels and their selection priority needs to be kept. FIG. 6 shows an example of call channel selection priorities set in the call channel management table. In this example, the base station uses four radio frequencies, and three channels are time-division-multiplexed on each frequency (that is, 12 communication channels). The software of the monitoring device OMC refers to the call channel management table to refer to the call channel TC.
H1-0 is selected with the highest priority, but if it fails to put the channel into the call state, TCH1-1 and TCH1 will be used thereafter.
-2, TCH2-0, ...

FIG. 7 is a diagram showing a functional configuration example of the monitoring device OMC. In the figure, 1 is a phase adjustment unit that manages the phase adjustment of the radio frame of each base station, 2 is a monitoring memory that stores monitoring information about each base station, and 3 is a radio system test (TID, TOD test) for each base station. And the like, a radio system test management unit 4, a supervisory control console 4 for the system maintainer to display monitor information and input control commands, and 5 an interface between the supervisory control console 4 and other functional units. The supervisory control console interface section 6 is a supervisory signal processing section for processing supervisory signals transmitted and received between the exchange MSC and each base station.

Also in the present invention, the configuration of the monitoring device OMC is not different from the conventional one, but new software (hatched portion in the figure) is added to the phase adjustment management unit 1 and the phase adjustment shown in FIG. The order data 21 is newly added. Further, the table 11 in the phase adjustment management unit 1 includes the speech channel management table shown in FIG.

The arrows in the figure show the procedure (control and information flow) of the inter-base station radio frame synchronization processing in the monitoring device OMC. In particular, the thick arrows indicate the new procedure added by the present invention. Hereinafter, with reference to FIG. 7, the monitoring device OM when performing inter-base station radio frame synchronization according to the phase adjustment order data 21 (contents are as shown in FIG. 5)
The operation of C will be described. The number of each procedure described below corresponds to the number of each arrow in FIG. 7.

1. The system maintenance person issues an automatic phase adjustment command from the supervisory control console 4 (or automatically by a timer) to the phase adjustment management unit 1 at a predetermined time (for example, at 0:00 am when traffic is least). 2. The phase adjustment management unit 1 requests the monitoring memory unit 2 for the phase adjustment order data 21. 3. The monitoring memory unit 2 returns the phase adjustment order data 21 to the phase adjustment management unit 1. 4. The phase adjustment management unit 1 requests the radio system test management unit 3 to perform the TID test at the highest base station A (reference station) in the phase adjustment order data 21. 5. Base station A performs the TID test. 6. The phase adjustment management unit 1 is notified of the TID test status by the base station A. 7. The phase adjustment management unit 1 is the second of the phase adjustment order data 21.
A phase difference measurement command is issued to the base station B (adjustment station) in the line. 8. Base station B measures the phase difference of the radio frame with base station A. 9. The phase adjustment management unit 1 is notified of the phase difference measured by the base station B. 10. The phase adjustment management unit 1 issues a phase adjustment command to the base station B based on the notified phase difference. 11. Base station B performs phase adjustment. 12. The phase adjustment management unit 1 is notified by the base station B that the phase adjustment has been completed. 13. The phase adjustment management unit 1 requests the radio system test management unit 3 to finish the TID test of the base station A. 14. The radio system test management unit 3 notifies the phase adjustment management unit 1 of the end of the TID test of the base station A.

The phase adjustment of the base station B is completed by the above procedure. After this, until the phase adjustment of all base stations in the service area is completed, the above steps 4 to 14 are repeatedly executed while changing the reference station and the adjustment station according to the order set in the phase adjustment order data 21.

FIG. 8 is a flow chart showing a software process for automatically performing the above phase adjustment sequence.
When an automatic phase adjustment command is issued to the phase adjustment management unit 1, the phase adjustment software (hereinafter, OMC software) in the phase adjustment management unit 1 adjusts with the reference station A according to the phase adjustment order data 21 of the monitoring memory 2. The station B is determined (step S1), and then the TID test speech channel TCHX- is used according to the speech channel management table for the reference station A.
a is selected (step S2).

The OMC software issues a command to the reference station A to execute the TID test on the communication channel TCHX-a (step S3), and the reference station A executes the TID test according to the command (step S4). Further, the OMC software issues a command to the adjusting station B to measure the phase difference of the radio frame between the reference station A and the communication channel TCHX-a (step S5), and the adjusting station B measures the phase difference according to the instruction. Is executed and the measurement result is notified to the monitoring device OMC (step S6).

The OMC software receives the phase difference information notified from the adjusting station B (step S7), and based on this, the phase difference of the radio frame between the reference station A and the adjusting station B is within ± 1 symbol. To the adjustment station B (step S8). The adjusting station B executes the phase adjustment of its own radio frame according to the phase adjusting command (step S9). When the OMC software confirms the end of the phase adjustment, it issues a command to the reference station A to end the TID test (step S10), and the reference station A ends the TID test (step 11). The OMC software refers to the phase adjustment order data 21 to check whether there is a further adjusting station below the adjusting station B (step S12). If there is a lower adjusting station, the adjusting station B is set to the reference station A and the adjusting station B to the lower order. Step S1 to step S12 are repeated with the adjusting station of No. 3 as the adjusting station B. If the phase adjustment of all the base stations is completed, the automatic phase adjustment ends (step S13).

[0032]

As described above, according to the present invention, a communication signal between a base station and a mobile unit of a subscriber in the radio zone is used when performing radio frame synchronization between base stations. Since it is not necessary to perform this, the phase adjustment can be performed at any time. Also, by simply adding software to the monitoring device, it is possible to utilize existing equipment as it is and automatically adjust the phase of all base stations in the service area.
As a result, it is possible to always maintain good line quality over the entire service area of the digital mobile communication system.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an apparatus configuration and a method for performing a TID test.

FIG. 3 is a diagram showing an outline of a system configuration and an inter-base station radio frame synchronization method according to an embodiment.

FIG. 4 is a diagram showing an example of a wireless zone configuration of a service area and an order of phase adjustment of a base station in the embodiment.

FIG. 5 is an example of a tree diagram showing the order of phase adjustment of the base station in the embodiment.

FIG. 6 is a diagram showing an example of call channel selection priorities in the embodiment.

FIG. 7 is a diagram illustrating a functional configuration example of a monitoring device according to an embodiment.

FIG. 8 is a flowchart showing software processing of an automatic phase adjustment sequence in the embodiment.

FIG. 9 is a diagram showing an outline of a conventional inter-base station radio frame synchronization method.

FIG. 10 is a diagram showing an example of phase adjustment of a radio frame.

FIG. 11 is a diagram showing in more detail an example of phase adjustment of a radio frame.

[Explanation of symbols]

 1 phase adjustment management unit 11 table 2 monitoring memory 21 phase adjustment order data 3 radio system test management unit 4 monitoring control console 5 monitoring control console interface unit 6 supervisory signal processing unit 50 inter-base station wireless frame synchronizer 51 management unit 52 phase adjustment Part 53 Synchronization order storage part 60 Base station (reference station) 61 Base station (coordination station) 62 Test mobile unit

Claims (3)

[Claims] 1. A radio frame synchronization method between base stations for phase-synchronizing radio frames between base stations of a digital mobile communication system, wherein one of base stations to be synchronized is defined as a reference station and the other is defined as a coordination station. The reference station transmits and receives a signal by connecting a radio line to the test mobile device provided in the own station, and the coordinating station intercepts a communication signal between the reference station and the test mobile device and transmits the communication signal. The radio frame phase of the reference station is detected from the above, the phase difference of the radio frame between the reference station and the adjustment station is measured, and based on the phase difference, the adjustment station of the adjustment station can be phase-synchronized with the radio frame of the reference station. A radio frame synchronization method between base stations that adjusts the radio frame phase. 2. An inter-base-station radio frame synchronization device for phase-synchronizing radio frames between base stations of a digital mobile communication system, comprising a management unit and a phase adjustment unit, the management unit comprising: One of the base stations to be synchronized is defined as a reference station, and the other is defined as a coordinating station, requesting the reference station to connect a radio line to a test mobile unit provided in the reference station to transmit and receive signals, Further, to the adjustment station, a communication signal between the reference station and the test mobile unit is intercepted, the radio frame phase of the reference station is detected from the communication signal, and the phase difference of the radio frame between the reference station and the adjustment station is detected. A request is made to measure and return the measured phase difference, and the phase adjusting unit, based on the phase difference returned from the adjusting station,
An inter-base station radio frame synchronization device that sends a radio frame phase adjustment instruction to the adjustment stations so that radio frame phase synchronization can be established between the adjustment stations. 3. When radio frame phase synchronization is established between a reference station and a coordinating station, the coordinating station is used as a new reference station, and another base station that is not yet synchronized is used as a coordinating station, and the inter-base station synchronization is sequentially repeated. The mobile communication system further includes a synchronization order storage unit that stores an inter-base station synchronization order that enables radio frame phase synchronization among all base stations in a predetermined area of the mobile communication system, and the management unit reads from the synchronization order storage unit. 3. The inter-base station radio frame synchronization apparatus according to claim 2, wherein control is performed such that radio frame phase synchronization between the base stations is sequentially performed in accordance with the inter-base station synchronization order.