JPH10108248A - Inter-base station frame synchronizing method of tdma mobile body communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit the deviation amount of a frame timings in respective base stations and a reference station to be within a permission range by executing a frame synchronization processing based on the deviation amount of the frame timings between a self station and a reference station and also adding the deviation amount of the frame timings of the both stations to a control signal so as to transmit it. SOLUTION: The number of deviation bits between the frame timing of the self station and that of the reference station is calculated based on the control signal outputted from the reference station (S3). Then, it is discriminated whether or not the deviation bit number exceeds the number of permission bits (S4). When the deviation bit number exceeds the permission bit number, the frame timing of the self station is permitted to coincide with that of the reference station and, after that, the number of the deviation bits between the self station and the reference station is added to the control signal so as to be transmitted (S5 and S6). In the meantime, unless the deviation bit number exceeds the permission bit number, the calculated number of the deviation bits in the frame timings between the self station and the reference station is added to the control signal so as to be transmitted (6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of synchronizing frames between base stations in TDMA mobile communication.

[0002]

2. Description of the Related Art PHS (Personal Handy-phone System)
, A four-channel multiplex multi-carrier TDMA (Time Division Multiple Access) / T
The DD (Time Division Duplex) system is adopted. T
The DMA / TDD scheme is a scheme in which a radio frequency is time-divided, a specific time zone (slot) is assigned to a caller, and communication is performed in the assigned slot.

In this system, as shown in FIG. 2, a digital signal on one radio carrier is divided into frames (TDMA frames) every 5 ms. One frame is divided into eight slots (625 μs). Then, four slots # 1D to # 4D are assigned to the downlink (base station → terminal), and four slots # 1U to # 4U are assigned to the uplink (terminal → base station).

[0004] Of the eight slots, one slot each for uplink and downlink is allocated for a control channel for transmitting and receiving a control signal, and the other six slots are allocated for a communication channel for transmitting and receiving a voice signal. Have been.

In the current PHS service, 100
The control signal is transmitted from the base station to the terminal at a rate of once every ms. That is, every time 20 TDMA frames are transmitted, a control signal is transmitted from a base station to a terminal in one slot allocated for a downlink control channel.

In the TDMA / TDD system, since one radio frequency band is used in a time-division manner, frame timings (timings for time-division of the radio frequency band) coincide between each base station so that signals do not overlap. It is necessary to be. If the frame timing does not match between each base station, control signals transmitted from each base station collide,
There is a risk that these base stations may not be able to set a communication path with the terminal.

[0007] When frame synchronization is not established between adjacent base stations (when frame timings do not match), those base stations select the same frequency band as a communication frequency band. In this case, a radio section shorter than the slot length that cannot be used in the frequency band occurs, and the frequency utilization rate decreases.

Therefore, in the mobile communication of the TDMA / TDD system, it is necessary to synchronize the TDMA frame timing of each base station.

[0009]

Therefore, a method of hierarchically synchronizing the frame timing of the base station is considered. For example, when base stations are arranged as shown in FIG. 3, the first base station A1 is set as the uppermost layer reference station, and the second base station A1 is used as the second base station.
And the third base stations A2 and A3 as base stations below the first base station, the fourth base station A4 as base stations below the second base station A2, and the fifth base station A5 below the third base station A3. Base station.

[0010] Each base station performs a frame synchronization process with the base station in the next higher layer. That is, the fifth base station A5 compares its own frame timing with the frame timing of the third base station A3 in the next higher layer,
If the frame timings of both stations are different from each other by more than the allowable range, the frame timing of the own station is changed to the third base station A.
Match the frame timing of 3.

The third base station A3 compares the frame timing of its own station with the frame timing of the first base station A1 in the next higher layer. , And adjusts the frame timing of the own station to the frame timing of the first base station A1.

The fourth base station A4 compares the frame timing of its own station with the frame timing of the second base station A2, which is one layer higher than the own base station. Then, the frame timing of the own station is adjusted to the frame timing of the second base station A2.

The second base station A2 compares the frame timing of its own station with the frame timing of the first base station A1 immediately above it. , And adjusts the frame timing of the own station to the frame timing of the first base station A1.

By the way, when such frame synchronization is performed, the frame timing between an arbitrary base station and a base station in a layer immediately above the base station and the above-described arbitrary base station and a layer below the same are determined. The frame timing with a certain base station is within an allowable range, but the base station is one layer higher than the arbitrary base station and the base station is one layer lower than the arbitrary base station. Frame timing may be out of the allowable range.

For example, if the allowable range of the frame timing deviation is ± 6 bits and the frame timings of the first to fifth base stations A1 to A5 are as shown in FIG. Frame timing between A1 and second base station A2, first base station A1 and third base station A
3 between the second base station A2 and the fourth
Frame timing with base station A4, third base station A
The frame timing between the third base station A5 and the fifth base station A5 is within an allowable range.

However, the frame timing between the first base station A1 and the fourth base station A4 and the frame timing between the first base station A1 and the fifth base station A5 are out of the allowable range.

An object of the present invention is to provide a method of synchronizing frames between base stations in TDMA mobile communication, in which the amount of deviation between the frame timing of each base station and the frame timing of a reference station having a hierarchical relationship can be within an allowable range. Aim.

[0018]

SUMMARY OF THE INVENTION TDMA according to the present invention
In the base station frame synchronization method of mobile communication, in a group of base stations to be subjected to frame synchronization, a hierarchical relationship is predetermined with a predetermined base station as a reference station being the highest layer, and each base station has In a method of synchronizing frames between base stations in TDMA mobile communication, which performs frame synchronization processing based on a control signal from a synchronization destination base station which is a base station in an upper layer, a base station whose synchronization destination base station is a reference station has its own base station. A frame synchronization process is performed based on the frame timing deviation between the station and the reference station, and the frame timing deviation between the own station and the reference station after the synchronization processing is added to the control signal and transmitted, and the synchronization destination base station is transmitted. Is a base station other than the reference station,
Based on the deviation amount of the frame timing between the own station and the synchronization destination base station and the deviation amount of the frame timing between the synchronization destination base station and the reference station, the deviation amount of the frame timing between the own station and the reference station was calculated and obtained. Based on the amount of deviation of the frame timing between the own station and the reference station, the frame synchronization processing is performed, and the deviation amount of the frame timing between the own station and the reference station after the synchronization processing is added to the control signal and transmitted. I do.

Specifically, the frame synchronization processing is performed such that the frame timing of the own station coincides with the frame timing of the synchronization-destination base station only when the deviation amount of the frame timing between the own station and the reference station exceeds an allowable range. This is a process of making the frame timing of the own station coincide with the frame timing of the reference station.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a PHS system will be described below with reference to FIG.

The group of base stations for which frame synchronization is achieved is shown in FIG.
It is assumed that a hierarchical relationship is set in advance as shown in FIG.

Each base station performs frame synchronization processing with the base station one layer above it as a synchronization destination base station. The control signal output from each base station includes an identification signal (base station identification signal) representing the own station. In this embodiment, the control signal output from each base station is added with the number of bits in the frame timing between the own station and the reference station.

FIG. 1 shows a frame synchronization processing procedure performed by each base station.

If the own station is a reference station (step 1
Then, the process proceeds to step 6, where the number of bits shifted from the frame timing of the reference station is added to the control signal and transmitted. In this case, since the own station is the reference station, the number of shift bits of the frame timing between the own station and the reference station is 0.
Becomes

The own station is not the reference station (N in step 1)
O) If the synchronization destination base station is a reference station (YES in step 2), that is, if the base station immediately above the own station is a reference station, based on a control signal output from the reference station. Then, the number of shift bits between the frame timing of the own station and the frame timing of the reference station is calculated (step 3). Whether the received control signal is a control signal from the reference station is determined based on the base station identification number included in the control signal.

Then, it is determined whether or not the number of shifted bits exceeds the allowable number of bits (step 4). If the number of shifted bits exceeds the allowable number of bits, the frame timing of the own station is made to match the frame timing of the reference station (step 5).

Thereafter, the process proceeds to step 6, where the number of bits shifted from the frame timing of the own station and the reference station is added to the control signal and transmitted. In this case, the number of shifted bits of the frame timing between the own station and the reference station is zero.

If it is determined in step 4 that the number of shifted bits does not exceed the allowable number of bits, the process proceeds to step 6 where the number of shifted bits of the frame timing between the own station and the reference station calculated in step 3 is controlled. It is added to the signal and transmitted.

The own station is not the reference station (N in step 1)
O), if the synchronization destination base station is not the reference station (NO in step 2), that is, if the own station is not the reference station and the
If the base station in the next higher layer is not the reference station, the number of shift bits between the frame timing of the own station and the frame timing of the synchronization destination base station is calculated based on the control signal output from the synchronization destination base station (step 7).

Then, the obtained number of bits of the frame timing deviation between the own station and the synchronization destination base station and the deviation of the frame timing between the synchronization destination base station and the reference station included in the control signal from the synchronization destination base station. Based on the number of bits, the number of bits that are shifted in frame timing between the own station and the reference station is calculated (step 8).

Next, it is determined whether or not the obtained number of shifted bits of the frame timing between the own station and the reference station exceeds the allowable number of bits (step 9). If the number of shifted bits in the frame timing between the own station and the reference station exceeds the allowable number of bits, the frame timing of the own station is made to match the frame timing of the synchronization destination base station (step 10). Thereafter, the process proceeds to step 11, where the number of bits shifted from the frame timing of the own station and the reference station is added to the control signal and transmitted. In this case, the number of bits in the frame timing between the own station and the reference station is equal to the number of bits in the frame timing between the synchronization destination base station and the reference station.

If it is determined in step 9 that the obtained number of shift bits of the frame timing between the own station and the reference station does not exceed the allowable bit number, step 1 is executed.
Then, the number of bits of the frame timing shift between the own station and the reference station calculated in step 8 is added to the control signal and transmitted.

According to the above embodiment, it is possible to reduce the number of shifted bits between the frame timing of each base station having a hierarchical relationship and the frame timing of the reference station to the allowable bit number or less. In step 10 described above, the frame timing of the own station is made to match the frame timing of the synchronization destination base station. However, the present invention is not limited to this, and the frame timing of the own station may be made to match the frame timing of the reference station. Good.

According to the present invention, the amount of deviation between the frame timing of each base station having a hierarchical relationship and the frame timing of the reference station can be kept within an allowable range.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a frame synchronization processing procedure.

FIG. 2 is a schematic diagram showing a frame structure of a TDMA / TDD system.

FIG. 3 is a schematic diagram showing a base station group to be subjected to frame synchronization.

FIG. 4 is an explanatory diagram for explaining a problem caused by the conventional hierarchical synchronization method.

Claims (2)

[Claims] 1. In a group of base stations to be subjected to frame synchronization, a hierarchical relationship is predetermined with a predetermined base station as a top-level reference station, and each base station is a base station of a higher hierarchical level. In a frame synchronization method between base stations for TDMA mobile communication, which performs frame synchronization processing based on a control signal from a synchronization destination base station, a base station whose synchronization destination base station is a reference station has a frame timing between itself and the reference station. Based on the deviation amount of the base station, the frame synchronization processing is performed, the deviation amount of the frame timing between the own station and the reference station after the synchronization processing is added to the control signal and transmitted, and the base station whose synchronization destination base station is other than the reference station is transmitted. The frame timing between the own station and the reference station is determined based on the frame timing deviation between the own station and the synchronization base station and the frame timing deviation between the synchronization destination base station and the reference station. Frame synchronization processing based on the obtained frame timing deviation between the own station and the reference station, and controls the frame timing deviation between the own station and the reference station after the synchronization processing. A method for synchronizing frames between base stations in TDMA mobile communication, characterized by transmitting the signal in addition to a signal. 2. The frame synchronization process is a process of matching the frame timing of the own station with the frame timing of the synchronization-destination base station only when the deviation amount of the frame timing between the own station and the reference station exceeds an allowable range. 2. The TDMA according to claim 1, wherein the TDMA is a process for matching the frame timing of the own station with the frame timing of the reference station.
A frame synchronization method between base stations for mobile communication.