JP3029343B2 - TDMA frame synchronization between base stations in mobile communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA frame synchronization system between base stations in mobile communication. For example, an access system on a radio line between a digital cordless telephone and a radio base station is TDMA (Time Division Multiple Access).
) System that can be applied to a private branch exchange system.

[0002]

2. Description of the Related Art In recent years, for example, in offices and the like, an extension telephone housed in a private branch exchange or the like has been increasingly provided to each employee in order to improve work efficiency. As described above, a cordless telephone excellent in portability has been considered as a telephone to be provided to each employee, and a private branch exchange system that can handle the cordless telephone is being developed. Here, it has been considered to adopt a digital transmission method which has good confidentiality compared to the analog transmission method and can reduce the size and weight of the cordless telephone. Transmission between the digital cordless telephone and the wireless base station is considered. A method according to the TDMA method has been proposed.

[0003] In a private branch exchange system for mobile communication employing the TDMA system, it is desired to synchronize wireless base stations. When a cordless telephone moves from the service zone of one radio base station to the service zone of another radio base station, if the TDMA frame is not synchronized between the radio base stations before and after the movement, the radio of the movement destination may be changed. This is because it is necessary to start communication after the base station performs the synchronization operation, and the presence of such a synchronization establishment time causes an instantaneous interruption of communication. In order to establish TDMA frame synchronization in advance, the TDMA
It is necessary to keep the phase of the frame generator synchronized.

Conventional synchronization schemes for synchronizing TDMA frames between radio base stations include the following literatures 1 and 2.
There was a thing of a statement.

[0005] Reference 1 "Specification and Drawings of Japanese Patent Application No. 3-97401" Document 2 "Japanese Patent Application Laid-Open No. 3-224325" The method described in Reference 1 uses a base station interface circuit on the private branch exchange side to transmit radio base stations. In this case, the change point signal (TDMA frame synchronization signal) of the TDMA frame timing which the exchange side has centrally is notified by multiplex transmission to the polling signal.
The purpose is to synchronize a DMA frame between radio base stations.

[0006] In the method described in Document 2, a delay adjustment device is installed near a radio base station and used as a frame synchronization pulse transmitted from a synchronization signal generator provided near an exchange (control station). The delay adjuster performs delay control so that the transmitted pulse reaches each wireless base station at the same time, thereby trying to synchronize the TDMA frame between the wireless base stations. Reference 2 also discloses that the delay adjustment device loops back the pulse transmitted from the synchronization signal generation device, and the synchronization signal generation device determines the delay adjustment amount from the transmission time and the reception time of the pulse.

[0007]

In the system described in Document 1, no problem occurs if the length of the cable between the base station interface circuit on the exchange side and the radio base station is constant for all the cables. However, in practice, the cable length often varies, and in such a case,
There is a possibility that a large difference occurs in the transmission delay due to the cable, and the synchronization between the radio base stations may not be sufficient. As a result, if the cordless telephone moves between service zones of the wireless base station during communication, a momentary interruption occurs. For example, when the length of a plurality of in-house cables having a diameter of 0.5 mm is in the range of 0 to 2 km, a transmission delay time difference of about 10 μs has occurred.

[0008] The method described in Document 2 requires a dedicated device for establishing synchronization, such as a delay adjusting device, in addition to the switching center and the radio base station. The structure of the system as a whole is complicated and not economical. In particular, in a system in which there are a large number of wireless base stations installed under the private branch exchange, the method described in Reference 2 is not practical.

In the method described in Reference 2, the transmission delay is measured by the reciprocation of the pulse to adjust the timing of the TDMA frame. In this respect, the influence of the variation in the cable length is suppressed. The measurement cycle is long, the synchronization of the TDMA frame cannot be corrected quickly, and the dedicated measurement configuration complicates the overall configuration.

[0010] The above-mentioned problems occur widely not only in the private branch exchange system but also in a mobile communication switching system in which an access system on a radio line between a digital mobile communication terminal and a radio base station is a TDMA system.

The present invention has been made in view of the above points, and can improve the accuracy of synchronization between radio base stations accommodating digital mobile communication terminals conforming to the TDMA system, so that the mobile communication terminals can communicate with each other. It is intended to provide a TDMA frame synchronization system between base stations in a simple and economical mobile communication, in which instantaneous interruption does not occur even when moving between service zones of a radio base station. It is.

[0012]

In order to solve such a problem, a TDM between base stations in mobile communication according to the first invention is provided.
In the A frame synchronization system, a digital mobile communication terminal
And the access method on the wireless link between
It is a TDMA system and has a base station interface
Transmission method between the base circuit and the radio base station
In a switching system that uses the
Provide steps. That is, the base station interface
Source circuit operates in (1) master mode and
Received as a response from the radio base station to the transmitted burst
A first signal for equalizing and outputting a received burst waveform
Layer 2 processing circuit and (2) operate in slave mode,
1 layer 1 processing circuit equalizes the received burst waveform
Based on the synchronized clock, the reception burst after the equalization
SYNC output included in the received burst waveform
Second layer that is extracted and output as a head timing signal
1 processing circuit and (3) berth to the radio base station by own circuit
After the transmission, the response of the radio base station to the
In the layer 1 processing circuit, the first tag of the received burst waveform is
The time it took to be extracted as
Transmission delay measuring means for measuring each base station, and (4) transmission delay
The time measured by the delay measurement means is sent to each radio base station.
Transmission delay information transmitting means for transmitting each
I do. In addition, the wireless base station transmits from the transmission delay information transmitting means.
Based on the notified time information, the received TDMA file
A phase correction unit for correcting the phase of the frame synchronization signal is provided.
To do.

In the TDMA frame synchronization method between base stations in mobile communication according to the second invention, digital mobile communication is used.
Access on the wireless link between the communication terminal and the wireless base station
Is the TDMA system, and the base station
The transmission method between the interface circuit and the radio base station is
In a switching system that is a time-division directional control transmission method,
The following means shall be provided. That is, the base station
The interface circuit operates in (1) master mode and
Base station response to bursts transmitted from the circuit
Equalizes and outputs the received burst waveform
Operating in the first layer 1 processing circuit and (2) slave mode.
And the reception berth equalized by the first layer 1 processing circuit
Based on the clock synchronized with the
The SYNC output included in the received burst waveform is
The second to extract and output as the top timing signal of the
Layer 1 processing circuit and (3) to the wireless base station by its own circuit
The base station responds to after transmitting a burst of
Is the received burst wave in the second layer 1 processing circuit.
Time taken to be extracted as the head timing of the shape
Transmission delay measuring means for measuring each radio base station,
(4) Based on the time information measured by the transmission delay means,
Transmission of TDMA frame synchronization signal to be transmitted to wireless base station
Phase correction to correct timing individually for each wireless base station
Means.

[0014]

According to the first and second aspects of the present invention, both a radio base station and
The time-division directional control transmission method (ping-pong transmission method) is applied as a transmission method between the base station interface circuit of the switch body and the base station interface circuit. Therefore, the base station interface circuit transmits a burst to the radio base station, and when the radio base station receives this burst, transmission and reception are switched, and the radio base station transmits the burst to the base station interface circuit. The period from the transmission of the burst by the base station interface circuit to the reception of the burst in the reverse direction includes transmission delay information on the transmission path between the radio base station and the base station interface circuit. Therefore, the transmission delay measuring means is provided in the base station interface circuit, and the transmission delay measuring means measures the time from when the base station interface circuit transmits a burst to the radio base station to when the burst is received from the radio base station. Is measured for each wireless base station, and synchronization control of TDMA frames is performed based on the measurement time (transmission delay information).

According to a first aspect of the present invention, the radio base station performs synchronization control of a TDMA frame based on a measurement time (transmission delay information). That is, the base station
Transmission delay information transmitting means provided in the interface circuit transmits the measured time information to each radio base station, and each radio base station transmits the received TDMA frame synchronization signal based on the transmitted time information. in which it was decided to modify the phase. Also, this base station interface
First and second layer 1 processing used by the circuit as its configuration
When operating in master mode, the
Can output the received burst waveform that has been shaped.
Those that cannot output the start timing signal of the burst waveform
On the other hand, when operating in slave mode, the line
It operates in synchronization with the input (reception burst waveform) and
An easily available ray that can output the clock and the SYNC output.
Since it is a first processing circuit, its structure is simple and economical.
It is something that can be done.

According to a second aspect of the present invention, synchronization control of a TDMA frame based on a measurement time (transmission delay information) is performed by a base station.
This is performed on the interface circuit side.
That is, those base station interface circuit, based on the measured time information, it was decided to modify the transmission timing of the TDMA frame synchronization signal to each radio base station
There is . Also, in the case of the second present invention, the first present invention
The base station interface circuit has the same configuration as
The first and second layer 1 processing circuits used for
When operating in mode, equalized (waveform shaped, etc.) reception
Although burst waveforms can be output,
A timing signal cannot be output.
Line mode (receive burst)
Waveforms), and the clock and SYNC output
This is an easily obtainable layer 1 processing circuit that can output
So the structure itself can be simple and economical
It is.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a private branch exchange system will be described below in detail with reference to the drawings.

FIG. 2 shows the entire configuration of the private branch exchange system according to this embodiment. First, the entire private branch exchange system will be described with reference to FIG.

In FIG. 2, a private branch exchange system according to this embodiment includes a digital cordless telephone (hereinafter simply referred to as a cordless telephone) 61 and a cordless telephone 61.
And a cordless telephone 6 that accommodates the wireless base station 51 and communicates with the wireless base station 51 in accordance with the TDMA method.
1 and a private branch exchange 1 that performs exchange processing so that communication between them can be performed.

The radio base station 51 is a base station for exchanging voice signals and control signals by multi-carrier TDMA with a cordless telephone 61 which is a digital mobile communication terminal located in a micro zone assigned to the radio base station 51. Base station interface circuit 17 described later
Is housed in The wireless base stations 51 are arranged at predetermined intervals so that communication can be performed even when the cordless telephone 61 moves between zones during communication. This allows
While the cordless telephone 61 is communicating,
Even if the user moves across the zone, the switching process of the wireless base station is executed so that the telephone call can be continued.

The radio base station 51 has a built-in TDMA frame phase correction circuit (not shown), and based on transmission delay information given from the base station interface circuit 17,
TDMA provided from base station interface circuit 17
Frame timing signal (TDMA frame synchronization signal)
The phase is corrected and used.

The private branch exchange 1 is a multicarrier TDMA
Is an exchange that realizes digital mobile communication by
As shown in FIG.
1-n, time division switch 30 and central processing module 4
Has zero. Line trunk module 11 (11-1)
Reference numerals 11 to n) denote line accommodating units in which interface circuits such as wired or wireless subscriber terminals or various trunks are arranged as necessary. FIG. 2 shows only the base station interface circuit 17 directly related to the characteristic portion of this embodiment as a detailed configuration of the line trunk module 11.

The base station interface circuit 17 has the detailed configuration shown in FIG. 1, and accommodates a plurality of radio base stations 51.
An interface circuit for exchanging 2B + D + K signals with the wireless base station 51. In this example,
As a transmission method between the base station interface circuit 17 and the radio base station 51, a time division direction control transmission method (ping-pong transmission method) is applied. That is, the base station interface circuit 17 transmits a burst including the signal of 2B + D + K to the radio base station 51, and when the radio base station 51 finishes receiving this burst, transmission and reception are switched and the radio base station 51
Transmits a burst including the signal of 2B + D + K to the base station interface circuit 17. The base station interface circuit 17 measures the time from the transmission of the burst to the reception of the burst in the reverse direction, as described later, and provides the wireless base station 51 with the transmission delay information.

Each base station interface circuit 17 is connected to the time division switch 30 and the central processing module 40 via a predetermined switch or controller (not shown).

The time division switch 30 is a switch for forming a communication path between terminals (including not only the cordless telephone 61 but also a wired telephone) or trunks accommodated in the line trunk module 11 or between the rank trunk modules 11. . The time division switch 30 is connected to the central processing module 40, and performs switching processing in a time division multiplex system in accordance with a connection control instruction from the central processing module 40.

The central processing module 40 is a control circuit for controlling each component of the exchange 1, and executes connection control according to a call processing program. Further, the central processing module 40 has a clock generator for a TDMA frame having a period of 5 ms and a clock generator for ping-pong transmission burst having a period of 125 μs (both are not shown). The transmission burst clock is supplied to the line trunk module 11.

In this embodiment, the TDMA frame period is 5 ms, the burst period is 125 μs, and ping-pong transmission is performed between the base station interface circuit 17 and the radio base station 51 at a period of 125 μs. Here, the TDMA frame clock and the ping-pong transmission burst clock are synchronized.

FIG. 3 shows a base station interface circuit 17-.
2 shows a configuration of a layer 1 signal between the wireless base stations 51. The layer 1 signal has two B channels (64 kb / s) for user information (voice / data), a D channel (16 kb / s) for control information, and a K channel (8 KB / S) for housekeeping information. ),
A frame synchronization and ping-pong monitoring bit F / P and a DC balance bit DC are added to the information bits of these channels.

A layer 1 signal having such a configuration (burst time T2 is 50.78 μs) is transmitted in one communication cycle (1
25 μs) In T4, the base station interface circuit 17
Is transmitted to the wireless base station 51 and the wireless base station 5
1 to the base station interface circuit 17.
Here, immediately after the base station interface circuit 17 finishes transmitting the DC balanced bit DC, the radio base station 5
1 cannot receive the burst transmitted by the wireless base station 51 from the point of time delayed by the propagation delay time T5. Further, the base station interface circuit starts from the point in time when the transmission / reception switching time T3 has elapsed from the point in time when the burst transmitted by the radio base station 51 has been received (this point in time has elapsed one communication cycle T4 from the previous transmission start point). 17 resumes transmission. The above-described propagation delay time T5 includes the base station interface circuit 17
And transmission delay time defined by the length of the cable connecting the wireless base stations 51.

FIG. 1 shows four radio base stations 51-1 to 51-1.
4 is a functional block diagram illustrating a configuration of a main part of a base station interface circuit 17 accommodating -4. FIG. 1 shows only the elements and signal flows directly related to the features in this embodiment, and has no direct relationship to the features.
The components and signal flows of the B-channel system, the upstream D-channel system (in the direction from the radio base station to the base station interface circuit), and the upstream K-channel system are omitted from the drawings, and the description thereof is also omitted. .

In FIG. 1, a base station interface circuit 17 includes a microcomputer (μCPU) 20, a transmission delay measuring circuit 21, a first selector circuit 22, a K-bit control circuit 23, and radio base stations 51-1 to 51-. 4 is provided with the layer 1 processing circuits 24-1 to 24-4 corresponding to the C.4 and the second selector circuit 25.

The microcomputer 20 controls the overall operation of the base station interface circuit 17 and measures and controls the transmission delay between the base station interface circuit 17 and the wireless base stations 51-1 to 51-4. , 51-4, and also transmits the transmission delay information to the wireless base stations 51-1,..., 51-4. The microcomputer 20 has a serial input / output terminal and a selection control terminal for controlling selection of the selector circuits 22 and 25, and the first selector circuit 22, the layer 1 processing circuit 24-1,
, 24-4, a plurality of radio base stations 51-1,.
It transmits / receives control information (for example, transmission delay information) to / from the transmission line 51-4 through the D channel, and selects a line for measuring transmission delay.

The transmission delay measuring circuit 21 is based on a ping-pong transmission burst clock supplied from the central processing module (switch body side) 40 and a reception burst head timing signal supplied from the second selector circuit 25.
The base station interface circuit 17 and the wireless base station 5
The time which defines the transmission delay among 1-1,..., 51-4 is measured, and the measurement result information of the transmission delay is output to the microcomputer 20 through the bus interface. A detailed configuration example of the transmission delay measurement circuit 21 will be described later.

Note that the measurement may be performed only at the time of initial setting when the radio base station 51 starts up.
It may be performed periodically.

The K-bit control circuit 23 periodically changes the TDMA frame clock having a period of 5 ms and the ping-pong transmission burst clock having a period of 125 μs provided from the central processing module 40 once every 5 ms.
A DMA frame timing signal (TDMA frame synchronization signal) is generated for each of the layer 1 processing circuits 24-1,..., 24-4, and the layer 1 processing circuits 24-1,.
4-4 to the downstream K channel input terminal.
A method of transmitting a TDMA frame timing signal that changes periodically once every 5 ms using the K channel is as follows.
Any method may be used. For example, the TDMA frame timing signal has a bit rate of 200 b /
s, while the transmission capability of the K channel is 8 kb / s, so that the TDMA frame timing signal and other control information can be multiplexed and transmitted on the K channel. In this embodiment, the TDMA frame timing signal 5 ms is set to K as shown in FIG.
It is assumed that the signal is transmitted as a change point signal from 1 to 0 of the channel.

Each of the layer 1 processing circuits 24-1 to 24-4 is connected to a corresponding radio base station 51- via a cable.
1, ..., 51-4. Each of the layer 1 processing circuits 24-1 to 24-4 assembles the burst to be transmitted shown in FIG. 3 from each channel signal based on the ping-pong transmission burst clock, and decomposes the received burst into each channel signal. In the case of this embodiment, the head timing signal of the received burst is further formed and provided to the second selector circuit 25.

As described above, the TDMA frame timing signal formed by the K-bit control circuit 23 and inserted into the transmission burst by each of the layer 1 processing circuits 24-1 to 24-4 is transmitted to the radio base station 51-1,. , 51-4 at different timings.

FIG. 4 is a timing chart for explaining such variations in the reception timing. FIG.
The lengths of the cables from the base station interface circuit 17 to the radio base stations 51-1, 51-2, 51-3, 51-4 are d, 2d, 3d as shown in FIG.
d and d / 2 are shown. The TDM shown in FIG. 4B formed by the K-bit control circuit 23 mainly from a TDMA frame clock (FIG. 4A) having a period of 5 ms.
The A frame timing signal (change point of the K channel from 1 to 0) is transmitted to the radio base stations 51-1, 51-2, 51-3, and 5-3 accommodated by the respective layer 1 processing circuits 24-1 to 24-4.
Even if the signals are simultaneously transmitted to 1-4, the transmission delays Td1, Td2, Td3, T
For d4, each radio base station 51-1, 51-2, 51
As shown in FIGS. 4C to 4F, at −3 and 51−4, the difference between the transmission delays Td1, Td2, Td3, and Td4 appears as it is.

Each radio base station 51-1, 51-2, 51-
If the difference between the reception timings of the TDMA frame timing signals in 3, 51-4 is neglected, as described in the subject of the present invention, the synchronization between the radio base stations may not be sufficient, and the cordless telephone 61 may be in communication. When the mobile terminal moves between service zones of the wireless base station 51, an instantaneous interruption occurs. Therefore, in this embodiment, the transmission delay is measured, and the measured transmission delay time information is supplied to the radio base station to synchronize the transmission and reception timing of the TDMA frame between each radio base station and the cordless terminal.

FIG. 5 is a timing chart for explaining a method of measuring the transmission delay time between the radio base station 51 and the base station interface circuit 17. Note that, in FIG. 5, the same reference numerals are given to the corresponding times in FIG.

Here, the measurement of the transmission delay time utilizes the feature of the ping-pong transmission system, that is, the fact that the transmission direction of the burst is controlled by time division. This allows
The transmission and reception of a signal used only for measuring the transmission delay time is not required.

In FIG. 5, the base station interface circuit 17 is a master, the radio base station 51 is a slave, and the slave operates subordinately to the master. The base station interface circuit 17 starts transmission when the ping-pong transmission burst clock is supplied. The burst length T2 to be transmitted is 26 bits (50.78 μs). When detecting a burst with the frame synchronization and ping-pong monitoring bits F / P transmitted from the base station interface circuit 17, the wireless base station 51 starts data reception. When data reception is completed, transmission / reception switching time T3 (0.925 μs)
Within a short time, burst transmission to the base station interface circuit 17 is started immediately,
Starts data reception when a burst is detected by the frame synchronization and ping-pong monitoring bit F / P.

In this embodiment, the base station interface circuit 17 (more precisely, the transmission delay measuring circuit 21) determines the burst length T2 and the transmission / reception switching time T from the transmission start timing.
3 starts counting, and when the head of the burst given from the radio base station 51 is detected, the timer operation is completed and the measured time Td is output to the microcomputer 20. I do. The measurement time Td thus measured is equal to two times the transmission delay time between the base station interface circuit 17 and the radio base station 51 accommodated.
The sum is twice the transmission and reception switching time T3 in the wireless base station 51. Therefore, the transmission delay time can be obtained by subtracting the transmission / reception switching time T3 in the wireless base station 51 from the measurement time Td and then dividing by 2. Since the transmission / reception switching time T3 is considerably shorter than the transmission delay time, a value obtained by dividing the measurement time Td by 2 can be regarded as the transmission delay time.

FIG. 6 shows such transmission delay time information (T
FIG. 7 is a block diagram showing a detailed configuration of the transmission delay measuring circuit 21 for obtaining d), and FIG. 7 is a timing chart of each section.

In FIG. 6, the transmission delay measuring circuit 21
Timing generation circuit 71, clock clock oscillator 72, counter circuit 73, latch circuit 74, and buffer circuit 75
Consists of

The timing generation circuit 71 is supplied with the ping-pong transmission burst clock shown in FIG. 7A from the central processing module 40, and receives any one of the layer 1 processing circuits 24 through the second selector circuit 25. 1,
, 24-4 output from the reception burst head timing signal shown in FIG. The timing generation circuit 71 determines the burst length T2 and the transmission / reception switching time T from the point in time when the ping-pong transmission burst clock changes to active.
3 and the clock inhibit signal CL
KINH * (* means active low) is made inactive, and when the reception burst head timing signal changes to active, the clock inhibit signal CL
Return KINH * to active. Further, based on the received burst head timing signal, the timing generation circuit 71 forms a latch signal LT * shown in FIG. 7D having a logic opposite to the logic of the received burst head timing signal. Clock inhibit signal CLKINH * generated by timing generation circuit 71 is applied to counter circuit 73, and latch signal LT * is applied to latch circuit 74.

The clock generator 72 generates a clock (hereinafter referred to as a clock) for the counter circuit 73 to perform a counting operation. The higher the speed of the clock, the higher the resolution (measurement accuracy of the measurement time). The resolution of the measurement time measured at, for example, 4 MHz is 0.244 μs.

The counter circuit 73 is provided with a ping-pong transmission burst clock as a reset signal in addition to the clock inhibit signal CLKINH * and the clock. The counter circuit 73 is reset when the ping-pong transmission burst clock becomes active, and thereafter, the clock inhibit signal CLKINH *
Performs a count operation by the clock clock that has arrived during the inactive period, and generates the clock inhibit signal C.
After LKINH * returns to active, the counting operation is stopped.

The count value when the count operation is stopped is proportional to the inactive period of the clock inhibit signal CLKINH *, and the inactive period of the clock inhibit signal CLKINH * is equal to the time Td in FIG. This means that the counter circuit 73 has counted the time (transmission delay time information) Td.

The latch circuit 74 latches the transmission delay time information Td based on the latch signal LT *. The buffer circuit 75 buffers the transmission delay time information Td. Td
Is a microcomputer 2
Read to 0.

As described above, the microcomputer 20 notifies the wireless base station 51 to be measured of the transmission delay time information Td as it is using the downlink D channel (control channel).

The radio base station 51 that has received the transmission delay time information Td calculates the transmission delay time by subtracting the transmission / reception switching time T3 of the own station from the transmission delay time information Td and dividing the result by two. The phase of the TDMA frame on the wireless line is corrected based on the calculated transmission delay time.

Therefore, according to the first embodiment described above, in a system for transmitting a timing signal of a TDMA frame from a base station interface circuit side of a private branch exchange to a radio base station, between the radio base station and the base station interface circuit. Is transmitted from the base station interface circuit side to the radio base station, so that the radio base station side can correct the timing of the TDMA frame according to the transmission delay. At T
The synchronization of the DMA frame can be established with high accuracy. The TDMA frame phase difference between the radio base stations is conventionally up to 10 when the cable length between the radio base station and the base station interface circuit is in the range of 0 to 2 km.
μs, but if the phase is corrected by the radio base station according to the first embodiment, it can be made within 1 to 2 μs.

As a result, while the cordless telephone 61 is communicating, the zone of one radio base station 51 is shifted from the zone of another radio base station 5
Even when moving to one zone, the instantaneous interruption of communication can be reduced to a level that does not cause a problem.

The first embodiment utilizes the feature of the ping-pong transmission system (time-division directional control system) in which bidirectional communication is performed in a time-division manner within one communication cycle. Unlike the conventional method, the transmission delay time is frequently measured even during communication and the like, and the synchronization of the TDMA frame can be reviewed, and the synchronization establishment accuracy can be improved in this respect as well.

Further, according to the first embodiment, since the transmission delay amount is measured by using many circuit parts already existing in order to realize the ping-pong transmission system, that is, a special delay amount measurement method is used. Since no circuit is required, the number of newly added components is small, and highly accurate TDMA frame synchronization between wireless base stations can be realized with a simple structure without impairing economic efficiency.

FIG. 8 is a block diagram showing the configuration of the second embodiment of the present invention, in which the same or corresponding parts as in FIG. 2 are denoted by the same reference numerals.

In practice, the layer 1 processing circuit is an integrated circuit (I
C) The layer 1 processing circuit realized by the chip but easily available is equalized (waveform shaping, etc.) in the master mode.
The received burst signal can be output, but the head timing signal of the received burst cannot be output. This second
In the embodiment, such a layer 1 processing circuit is applied.

In FIG. 8, radio base stations 51-1 to 51-1
Such a layer 1 processing circuit is applied to the layer 1 processing circuits 24-1 to 24-4 that transmit and receive bursts to and from the LTE-4. These layer 1 processing circuits 24-1 to 24-1
The equalized reception burst output from 24-4 is supplied to a timing extraction layer 1 processing circuit 27 via a second selector circuit 25 having an analog switch configuration. The layer 1 processing circuit 27 operates in the slave mode, extracts a SYNC output having a period of 125 μs synchronized with a burst from the radio base station,
The YNC output is supplied to the transmission delay measurement circuit 21 as the head timing signal of the reception burst.

In the ping-pong transmission, the slave mode is basically operated in synchronization with the master mode. Therefore, a synchronization pulse of 8K (125 μs) of the master can be taken out as a SYNC output.

According to the second embodiment, the same effects as in the first embodiment can be obtained. That is, the accuracy of synchronization between radio base stations accommodating digital mobile communication terminals according to the TDMA scheme can be improved, and even when the mobile communication terminal moves between service zones of the radio base station during communication, instantaneous movement is possible. It is possible to realize a TDMA frame synchronization method between base stations in mobile communication which has a simple structure and is economical, in which no interruption occurs.

In the above embodiment, the influence of the transmission delay is eliminated by correcting the phase of the TDMA frame synchronization signal received by the radio base station. The influence of the transmission delay may be eliminated by correcting the phase of the TDMA frame synchronization signal transmitted to the station. In this case, it is not necessary to transmit the transmission delay information from the base station interface circuit to the wireless base station.

Further, in the above-described embodiment, the transmission of the time obtained by adding the transmission / reception switching time to twice the transmission delay time in the cable as the transmission delay information is transmitted from the base station interface circuit to the radio base station. The base station interface circuit may perform a predetermined operation on the measured time to obtain a transmission delay time on the cable, and transmit this to the wireless base station.

In the above embodiment, one base station interface circuit accommodates four radio base stations, but the number of accommodations is not limited to this.

Furthermore, in the above embodiment, the time measurement for obtaining the transmission delay time information is from the burst transmission timing pulse to the burst reception start timing pulse from the radio base station. However, the timing for defining the measurement cycle is as follows. The output is not limited to the burst reception start timing, and may be output after a fixed time from the burst reception start. Even in this case, if a certain time is guaranteed, the accuracy as delay time information is the same as in the above embodiment.

Further, the present invention is not limited to the private branch exchange system but can be applied to other switching systems, and the digital mobile terminal is not limited to the cordless telephone.

[0067]

As described above, according to the present invention, the time from when a base station interface circuit transmits a burst to a radio base station to when a burst from the radio base station is received is determined by each radio base station. Transmission delay measurement means
Provided in the base station interface circuit , based on the measured time, the radio base station side or the base station interface.
Since the phase correction of the TDMA frame is performed on the side of the TDMA frame, the accuracy of synchronization between the radio base stations accommodating the digital mobile communication terminals according to the TDMA scheme can be improved, and the radio base station can communicate with the radio base station during communication. It is possible to realize a TDMA frame synchronization method between base stations in mobile communication in which instantaneous interruption does not occur even when moving between service zones of a station. And the base station
The interface circuits include the first and second, which are easily available.
Since the layer 1 processing circuit of FIG.
Can be made simpler and more economical.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a base station interface circuit according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a private branch exchange system according to the first embodiment.

FIG. 3 is an explanatory diagram showing a format of a signal transmitted and received between a base station interface circuit and a radio base station according to the first embodiment;

FIG. 4 is a timing chart showing how a TDMA frame synchronization signal is affected by transmission delay due to a cable.

FIG. 5 is an explanatory diagram of a method of measuring transmission delay time information according to the first embodiment.

FIG. 6 is a block diagram illustrating a detailed configuration of a transmission delay measurement circuit according to the first embodiment.

FIG. 7 is a timing chart of each part in FIG. 6;

FIG. 8 is a block diagram illustrating a configuration of a base station interface circuit according to the first embodiment.

[Explanation of symbols]

1: Private branch exchange, 17: Base station interface circuit, 2
0: microcomputer, 21: transmission delay measuring circuit,
23 ... K bit control circuit, 241-1 to 24-4 ... Layer 1 processing circuit, 51 ... Wireless base station.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H04Q 7/26 7/30 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04Q ⁷ /00-7/38 H04B 7/24-7/26

Claims (2)

(57) [Claims] 1. Between a digital mobile communication terminal and a radio base station
The access method on the wireless line in
The base station interface circuit of the
The transmission method between base stations is a time-division directional control transmission method.
In one switching system, a base station interface circuit operates in a master mode, and transmits a burst transmitted from its own circuit.
Received by the radio base station in response to the
First Layer 1 processing circuit for equalizing and outputs the paste waveform
And operates in the slave mode, and in the first layer 1 processing circuit, etc.
Based on a clock synchronized with the reduction has been received burst waveform
SYNC included in the received burst waveform after the equalization
Output as the start timing signal of the received burst waveform
A second layer 1 processing circuit to extract and output a force, after the transmission of the bursts to the radio base station according to its own circuit, it
The response of the radio base station to the second layer 1 processing circuit
Oite extraction, as the head timing of the received burst waveform
The time it took to be completed is measured for each wireless base station.
That transmission delayed and extended measuring means, the time measured by the transmission delay measurement means, each radio base
Bei and transmission delay information transmitting means for sending respectively to the station
In addition, the radio base station uses the time information notified from the transmission delay information transmitting means to
Then, the phase of the received TDMA frame synchronization signal is
A mobile communication device provided with a phase correcting means for correcting
TDMA frame synchronization method between base stations in communication. 2. Between a digital mobile communication terminal and a radio base station.
The access method on the wireless line in
The base station interface circuit of the
The transmission method between base stations is a time-division directional control transmission method.
In one switching system, a base station interface circuit operates in a master mode, and transmits a burst transmitted from its own circuit.
Received by the radio base station in response to the
First Layer 1 processing circuit for equalizing and outputs the paste waveform
And operates in the slave mode, and in the first layer 1 processing circuit, etc.
Based on a clock synchronized with the reduction has been received burst waveform
SYNC included in the received burst waveform after the equalization
Output as the start timing signal of the received burst waveform
A second layer 1 processing circuit to extract and output a force, after the transmission of the bursts to the radio base station according to its own circuit, it
The response of the radio base station to the second layer 1 processing circuit
Oite extraction, as the head timing of the received burst waveform
The time it took to be completed is measured for each wireless base station.
That transmission delayed and extended measuring means, based on the time information measured by the transmission delay unit, each of the radio
Transmission type of TDMA frame synchronization signal transmitted to base station
Correction means for correcting the timing of each radio base station individually
Between base stations in a mobile communication, characterized in that it comprises bets
TDMA frame synchronization method.