JPH07298347A - Base station subordinate synchronizing method and centralized control station - Google Patents

Abstract

PURPOSE:To suppress a decrease in frame synchronism precision between base stations by reviewing a transmission delay time at all times without lowering the utilization efficiency of the line between a base station and the centralized control station. CONSTITUTION:The centralized control station 1 generates and sends outgoing frames PHI1 to respective base stations 10-j (j is 1-n). Each base station sends incoming frame PHI2 to the centralized control station a fixed time after the reception of the frame phi1. The centralized control station estimates a transmission line delay quantity DELTAT on the basis of the phase difference between the outgoing frame and incoming frame each time a specific number of clock pulses of the frame phi2 are received, and varies the phase control quantity at the time of the generation of the frame PHI1 from a transmission reference frame phase PHI0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station dependent synchronization method and a centralized control station for a mobile communication system, for example, a digital mobile device having a microcell system structure such as a personal handyphone (PHP) system having a small base station area. It is applicable to a body communication system.

[0002]

2. Description of the Related Art A PHP system has been actively researched and studied so that a cordless telephone handset for home use (referred to as a PHP terminal) can be taken outdoors and used as a handy mobile telephone. The communication range of the PHP terminal is 100m
Since it is small and narrow, base stations must be installed at high density. Also, the adoption of the TDMA method has been almost decided as the access method of the PHP system.

TDM represented by PHP system
In the A-system microcell system, when the base stations are installed densely, the transmission waves from a plurality of base stations collide, or the transmission waves from other base stations collide with the radio waves from the mobile terminal. Therefore, there is a possibility that a call cannot be made, and by eliminating such waste, it is possible to achieve effective use of frequencies and reduction of the call loss rate. From the viewpoint of effective use of frequency and reduction of call loss rate, it is necessary for a plurality of neighboring base stations to operate in synchronization.

As a method for synchronizing such neighboring base stations, there is a base station dependent synchronization method. This base station dependent synchronization method is a method of synchronizing a plurality of base stations by giving a common synchronization signal to each base station from an exchange station (centralized control station), for example. In this case, the transmission path lengths from the exchange to each base station are not equal, and the difference in the transmission delay amount of the synchronization signal affects the synchronization.

A conventional base station dependent synchronization method, which also considers compensation for the difference in transmission delay amount, is as follows although not shown.

The base station inserts the synchronization data into a channel on the uplink and transmits it, the exchange exchanges the synchronization data back to the downlink, and the base station reports the time when the synchronization data was received and the synchronization data. The phase of the frame clock transmitted from the switching center is corrected based on the transmission delay amount obtained by the difference from the transmission time, thereby establishing synchronization between the base stations.

[0007]

However, in the conventional base station dependent synchronization method, in order to measure the transmission delay amount of the wired transmission line between the exchange station and the base station, the transmission delay amount between the base station and the exchange station is measured. Data is folded back on the line,
The line usage efficiency will be reduced.

Therefore, a method of returning using an empty channel can be considered in order to improve the utilization efficiency of the line, but the empty channel is designated and the acceptance of new information is suppressed between the exchange and the base station. In addition to the need for complicated procedures, there is the inconvenience that the transmission delay time cannot be measured at all times and synchronization reviews cannot be performed continuously.

Therefore, there is a demand for a base station dependent synchronization method capable of continuously performing synchronization adjustment in which the utilization efficiency of the line does not decrease even if the transmission delay time is measured.

[0010]

In order to solve such a problem, in the first aspect of the present invention, a centralized control station and a plurality of base stations respectively connected to the centralized control station by communication lines are provided. In a mobile communication system in which a base station is slave-synchronized with a central control station, the base station slave synchronization method is as follows.

That is, the centralized control station creates and transmits a downlink frame to each base station from the transmission reference frame phase common to each base station. Each base station transmits the uplink frame to the central control station after a fixed time from the timing of receiving the downlink frame. The central control station estimates the transmission path delay amount for each base station based on the phase difference between the downlink frame and the uplink frame every time when a predetermined number of clocks of the uplink frame from the base station are received. Then, the phase control amount in the process of creating the downlink frame is changed from the transmission reference frame phase.

A second aspect of the present invention relates to a centralized control station capable of realizing the first aspect of the present invention, and as a configuration corresponding to each base station,
It is characterized by including the following parts.

That is, a transmission phase generator for generating and transmitting a downlink frame to each base station from a transmission reference frame phase common to each base station, and a reception timing of an uplink frame from the base station are detected. Based on the phase difference between the received frame detection unit and the downlink frame and the uplink frame, the transmission path delay amount is estimated, and the transmission phase creation unit controls the phase when creating the downlink frame from the transmission reference frame phase. And a phase comparator for changing the amount.

[0014]

In the base station dependent synchronization method for a mobile communication system according to the first aspect of the present invention, the central control station creates and transmits a downlink frame to each base station, and each base station transmits the downlink frame. The uplink frame is transmitted to the central control station after a fixed time from the timing of receiving the. Then, the centralized control station estimates the transmission path delay amount based on the phase difference between the downlink frame and the uplink frame each time it receives a predetermined number of clocks of the uplink frame from the base station, and transmits the transmission path delay amount. The phase control amount when creating the downlink frame is changed from the reference frame phase.

Therefore, it is not necessary to transmit the data dedicated to the transmission line using the dedicated channel for measuring the amount of transmission line delay, and each time a predetermined number of upstream frame clocks are received. Since the phase control amount is reviewed, it is possible to keep the neighboring base stations synchronized at all times.

The centralized control station according to the second aspect of the present invention has a configuration for achieving the first aspect of the present invention.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a block diagram showing the main configuration of the mobile communication system according to this embodiment.

In FIG. 1, the mobile communication system according to the first embodiment has an exchange 1 and a plurality (n) of base stations 10-connected to the exchange 1 via communication lines. 1 to 10-n.

The exchange 1 is connected to the base station 10-
Base station corresponding unit 20 provided for every 1, ..., 10-n
, ..., 20-n, and an intra-station reference frame generation unit 2 and a transmission reference frame creation unit 3 that are common to the connected base stations 10-1, ..., 10-n.

The in-station reference frame generating section 2 is for generating an in-station reference frame which gives a timing reference for various operations in the switching center 1, and the generated in-station reference frame is also given to the transmission reference frame creating section 3. . Based on the intra-station reference frame, the transmission reference frame creation unit 3 common to the base station corresponding units 20-1, ..., 20-n is a transmission reference frame Φ 0 (note that the reference Φ 0 defines the frame type and the reference). Also means point phase: Φ 1, Φ
(2, φ1 and φ2 are also the same) and are given to each base station corresponding unit 20-1, ..., 20-n.

Each base station corresponding unit 20-j (j is 1 to n) performs communication processing corresponding to the connected base station 10-j. In FIG. Only the configuration related to the method is extracted and shown.
Each base station corresponding unit 20-j is a base station corresponding unit 20.
As shown in detail for -1, it includes a line interface 30-j and a frame transceiver 40-j.

The line interface 30-j transmits / receives the transmission frame and the transmission information, or the reception frame and the reception information in parallel with or over the communication line. The line interface 30-j is, for example, the frame transceiver 40-j.
From the base station 10-j, at least the received frame φ2-j is extracted as a signal component from the received signal from the base station 10-j. It is given to the transmitting / receiving unit 40-j. To give a more specific example, the line interface 30-j
The IFO memory is built in, and after the transmission data is buffered in this memory, the phase-adjusted transmission frame Φ 1 −
It is read and transmitted in synchronization with j.

The frame transmission / reception unit 40-j includes the base station 10
The received frame detection unit 43-j for detecting the received frame φ2-j from -j, the transmission frame phase Φ1-j to the base station 10-j, and the reception frame phase φ2-j from the base station 10-j. The phase comparison unit 42-j for comparison and the transmission phase creation unit 41-j for creating the transmission frame phase Φ 1 -j at the next timing based on the comparison result obtained by the phase comparison unit 42-j. There is.

On the other hand, each base station 10-j
As will be described in detail with reference to No. 1, a line corresponding unit 11-j connected to the exchange 1 by a communication line, a received frame φ 1 -j from the exchange 1 (corresponding to the above-mentioned exchange transmission frame Φ 1 -j) is detected. The received frame detection unit 12-j, which generates a transmission frame Φ2-j to the exchange 1 (corresponding to the exchange reception frame φ2-j described above) based on the received frame φ1-j. j, a radio unit 1 for performing communication with a mobile station (not shown) via a radio line
5-j, the radio unit 15-based on the received frame φ1-j
The wireless unit frame creation unit 14-j and the like that creates a transmission frame for j.

Here, the transmission frame creating section 13-j
A transmission frame Φ 2 -j having a phase different from the reception frame phase φ 1 -j by a fixed phase difference α (α may be the same in each base station or may be different in each base station).
To create.

Therefore, in the case of the first embodiment, unlike the prior art, each base station 10-j is not provided with a configuration for adjusting the phase of the synchronization signal, and the exchange 1 is used by each exchange. The station 10-j is provided with a frame transmission / reception unit 40-j configured to adjust the phase of the synchronization signal.

Next, the operation of the mobile communication system having the above switching center configuration and the base station configuration, particularly the base station dependent synchronization operation, will be described with reference to FIGS. 2 and 3. Here, FIG. 2 is a timing chart showing the phase relationship of various frames, and FIG. 3 is a flowchart showing processing in the frame transmitting / receiving unit 40-j in the base station corresponding unit 20-j.

In the following description, the base station 10
The description will be made by omitting the code portion "-j" that identifies -j or the corresponding element in the exchange (if the distinction is necessary, the description will be given similarly as above). Further, it is assumed that the transmission delay time in the downlink from the exchange station 1 to the base station 10 and the transmission delay time in the uplink from the base station 10 to the exchange station 1 are equal and both are ΔT.

First, the phase relationship between various frames will be described with reference to FIG.

The transmission phase creating unit 41 of the exchange 1 has a phase difference x with respect to the transmission reference frame Φ 0 shown in FIG.
A transmission frame Φ1 shown in (B) is created. Here, the phase difference x is not fixed, but is variable according to the comparison result from the phase comparison unit 42. As the phase control progresses, a certain value x0 (x0 in this embodiment is -ΔT).
To a value slightly deviating before and after this value x0. The state in which the phase difference x has converged means that the received frame φ1 at each base station 10-1, ..., 10-n will be described later.
-1, ..., φ1-n are in a synchronized state. The generated transmission frame Φ 1 is transmitted to the base station 10 by the line corresponding unit 30, but the reception frame detection unit 12 of the base station 10 changes the frame due to the transmission delay time ΔT due to the communication line. When received and detected,
As shown in (C), the phase of the received frame φ1 is delayed by the time ΔT compared to the phase of the transmitted frame φ1.

The transmission frame creation unit 13 of the base station 10
As shown in FIG. 2D, a transmission frame Φ 2 (= φ 1 + α) which is delayed from the reception frame φ 1 by a preset phase difference α (0 ≦ α <T) is created, and the line interface 11 switches the switching center. Send to 1. Also in this case, when the phase delay of the transmission delay time ΔT of the communication line occurs and the received frame detection unit 43 of the exchange 1 detects this frame,
The frame phase φ2 is Φ2 as shown in FIG.
It becomes + ΔT.

Since the various frames have the above-described phase relationship, the exchange 1 generates the transmission frame Φ1.
When the phase difference φ2-Φ1 between the received frame φ2 and
The phase difference φ2-Φ1 includes only the transmission delay time ΔT (unknown number) corresponding to the base station 10 as a variable, as shown in the following equation (1).

Φ 2 −Φ 1 = α + 2 · ΔT (1) Therefore, the transmission delay time ΔT (unknown number) with the base station 10 can be measured by a measurable phase difference φ, as shown in the following (2).
It can be obtained by an arithmetic expression including 2 −Φ 1 and a predetermined fixed value α.

ΔT = (φ 2 −Φ 1 −α) / 2 (2) If the transmission delay time ΔT (ΔT−1, ..., ΔT−n) is obtained, the base stations 10-1 ,. The phase of the received frame φ1-1, ..., φ1-n in 10-n is the phase of each base station 10-1,
... so that the transmission frame phase Φ1- in each base station corresponding part 20-1, ..., 20-n of the exchange 1 so as to match in 10-n.
, ..., Φ 1-n can be defined. For example, each base station corresponding unit 20-1, ..., 20-n (hence, each frame transmitting / receiving unit 40-1, ..., 40-n) has a transmission reference frame phase Φ0 as shown in the following equation (3). From the transmission delay time ΔT-1, ..., ΔT-n, the transmission frame phase Φ1-
, ..., Φ 1-n are advanced so that the received frames Φ 1 in all the base stations 10-1 to 10-n
The phases of −1 to φ1 −n can be matched with the transmission reference frame Φ0.

Φ 1 = Φ 0 −ΔT (3) In the case of this embodiment, the determination of the transmission frame phase Φ 1 according to the above-described principle is reviewed at a predetermined cycle (frame cycle), and the phase adjustment operation this time is performed. The value from the previous cycle is used. FIG. 3 shows each base station corresponding unit 20-j in the switching center 1, especially its frame transmitting / receiving unit 40-.
9 shows the phase adjustment processing of j.

When the base station dependent synchronization processing is started, the phase comparison unit 42 sets the processing number i to "1", the phase difference A (0) to "α", and the transmission frame phase Φ1 (i) to the transmission reference frame. Parameter initialization processing for setting the phase Φ 0 is performed (step 100).

Thereafter, the transmission frame Φ 1 (i) is transmitted from the transmission phase creating unit 41, and the reception frame φ 2 (i) is fetched from the reception frame detecting unit 43, and their phase difference A (i) = φ 2 (i). -Φ 1 (i) is calculated (steps 101 to 103). And this phase difference A
It is determined whether (i) is equal to the previous phase difference A (i-1) (step 104).

The phase difference A (i) of this time is the phase difference A of the previous time.
If it is equal to (i-1), the next transmission frame phase Φ
After setting 1 (i + 1) to be equal to the transmission frame phase Φ 1 (i) this time (step 105), the number of processings i is set to 1
It increments and returns to step 101 mentioned above (step 106).

On the other hand, if the current phase difference A (i) is different from the previous phase difference A (i-1), the next transmission frame phase Φ 1 (i + 1) is calculated according to the following equation (4). After obtaining and setting (step 107), the number of processings i is set to 1
It increments and returns to step 101 mentioned above (step 106).

Φ 1 (i + 1) = Φ 1 (i) − {A (i) −A (i−1)} / 2 (4) The phase difference φ 2 −Φ 1 in the above equation (2) is represented by A, and By substituting Eq. (2) for transmission delay time ΔT in Eq. (3), the transmission frame phase Φ 1 (i + 1) at the processing number i + 1 can be expressed by the following equation (5). The transmission frame phase Φ 1 (i) can be expressed by the following equation (6). For each of both sides of Eq. (5), the values on both sides of Eq.
Equation (4) is obtained.

Φ 1 (i + 1) = Φ 0 − {A (i) −α} / 2 (5) Φ 1 (i) = Φ 0 − {A (i−1) −α} / 2 (6) Therefore, (6) 4) Transmission frame Φ1 (i +
To transmit 1), the above-described principle explanation is valid and the phases of the reception frames φ1-1 to φ1-n in all the base stations 10-1 to 10-n can be matched with the transmission reference frame φ0. Like

As described above, each base station corresponding unit 20-j of the exchange 1 repeats the processing shown in the flowchart of FIG.
At any time, the transmission delay time ΔT can be automatically measured and its phase compensation can be performed. As a result, not only can wire-based frame synchronization be established in the neighboring base stations, but also wireless-based frame synchronization can be established in this embodiment (note that in the first embodiment, wired-based frames and wireless-based frames are It is assumed that the same period is synchronized).

According to the first embodiment described above, the delay amount of the wire transmission line is measured by using the phase of the frame clock transmitted and received between the exchange 1 and the base station 10-j, and the base station dependent synchronization is performed. Since this is achieved, the utilization efficiency of the line between the base station 10-j and the exchange 1 does not decrease. Further, since the delay time is automatically measured and the phase is compensated every time the frame is transmitted / received, it is possible to suppress the deterioration of the frame synchronization accuracy between the base stations due to the variation of the transmission delay time.

Incidentally, after measuring the delay time of the wired transmission line in the same manner as in the first embodiment, the measured delay time is transmitted to the base station 10-j and the phase compensation operation is performed by the base station 10-j.
However, the number of transmissions and receptions for establishing synchronization is larger than that in the first embodiment, which is not efficient.

It is also possible to measure the transmission delay time by transmitting and receiving the frame clock by executing the initial frame transmission from the base station 10-j. However, in general, because the exchanges are in control,
The switching center is not configured to make the time from frame reception to frame transmission constant. Therefore, if the above-mentioned attempt is made, it is necessary to considerably change the switching center. Therefore, it is preferable to perform the first transmission of the frame clock for measuring the transmission delay time from the exchange side as in the above embodiment.

In the first embodiment, the case where the frame period of the wired line between the exchange and the base station is the same as the frame period of the wireless line in the base station has been described as an example. A second embodiment conceptually shown in FIG. 4 when the frame period of the wired line and the frame period of the wireless line are different, particularly when the frame period of the wireless line is an integral multiple of the frame period of the wired line. As described above, the same synchronization establishment configuration as in the first embodiment may be separately prepared for the wired system and the wireless system.

As shown in FIG. 5, when the frame period of the wireless line is N (N is an integer) times the frame period of the wired line, even if the subordinate synchronization of the base station is established for the wired system, FIG. As shown, in the wireless system, N establishment point candidates may occur in the wireless frame cycle, and synchronization may be erroneously established.

Therefore, a radio frame transmitter / receiver 40-jA having a similar structure to that of the first embodiment, which has a low timing accuracy for capturing the phase difference, is provided in the exchange 1, and each base station 10-j is provided with a radio. A frame transmission / reception unit (according to the wireless system specifications of the reception frame detection unit 12-j and the transmission frame creation unit 13-j in FIG. 1) 16-j is provided, and the synchronization shift in each base station 10-j is 1 wired frame. In addition to providing the frame transmission / reception unit 40-jB for a wired system having the same configuration as that of the first embodiment, which performs a rough phase adjustment within a cycle and has a high timing accuracy for capturing a phase difference, , Each base station 10-j is provided with a wired frame transmission / reception unit (consisting of the reception frame detection unit 12-j and the transmission frame creation unit 13-j of FIG. 1) 17-j to adjust the phase within one wired frame period. To do.

The radio frame information may be, for example, information of one or several bit patterns inserted in a data series transmitted / received via a communication line.

According to the second embodiment described above, since the synchronization establishment structure of the first embodiment is hierarchically provided, even if the frame period of the wireless line is an integral multiple of the frame period of the wired line, Subordinate synchronization can be established with high accuracy.

Although the present invention was made with the PHP system in mind, it can be naturally applied to other mobile communication systems. Further, depending on the system, a station to which a plurality of base stations are connected may not have a switching function. Considering this point, the station called the exchange in the embodiment is called the central control station in the claims.

Further, according to the above embodiment, the phase adjustment amount is reviewed in the frame cycle, but it may be reviewed in a slightly longer cycle.

[0053]

As described above, according to the present invention, the central control station creates and transmits a downlink frame to each base station, and each base station fixes from the timing when this downlink frame is received. Each time the central control station transmits an upstream frame to the central control station after a lapse of time, and the central control station receives a predetermined number of upstream frame clocks from that base station, it is based on the phase difference between the downstream frame and the upstream frame. hand,
Since the amount of transmission path delay is estimated and the phase control amount when creating a downlink frame is changed from the transmission reference frame phase, it is possible to reduce the utilization efficiency of the line between the base station and the centralized control station. In addition, since the transmission delay time is constantly reviewed, it is possible to suppress deterioration in frame synchronization accuracy between base stations due to fluctuations in the transmission delay time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a mobile communication system according to a first embodiment.

FIG. 2 is a timing chart showing a phase relationship of various frames according to the first embodiment.

FIG. 3 is a flowchart showing processing of a frame transmitting / receiving unit of the first embodiment.

FIG. 4 is a block diagram showing a conceptual configuration of a second embodiment.

FIG. 5 is a diagram illustrating the necessity of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Switching station (centralized control station), 10-1 to 10-n ... Base station, 12-1 to 12-n ... Received frame detection unit in the base station, 13-1 to 13-n ... Transmission frame creation unit, 20-1 to 20-n ... Base station creation unit, 40-1 to 40-n ... Frame transmission / reception unit, 41-1 to 41-n ... Transmission phase creation unit, 42-1 to 42-n ... Phase comparison unit, 43-1 to 43-n ... Received frame detector.

Claims (2)

[Claims] 1. A mobile communication system comprising a centralized control station and a plurality of base stations respectively connected to the centralized control station via communication lines, wherein each base station is slave-synchronized with the centralized control station. The station creates and transmits a downlink frame to each of the base stations from the transmission reference frame phase common to each of the base stations, and each of the base stations receives a fixed time from the timing of receiving the downlink frame. An upstream frame is transmitted to the central control station, and the central control station, for each base station, receives a predetermined number of upstream frame clocks from the base station, and then downloads a downstream frame and an upstream frame. The transmission path delay amount is estimated on the basis of the phase difference between and, and the phase control amount at the time of creating the downlink frame is changed from the transmission reference frame phase. Base station dependent synchronization method. 2. A central control station of a mobile communication system, which is connected to a plurality of base stations via a communication line corresponding to the base stations, for subordinately synchronizing the base stations, wherein the base station has a configuration corresponding to the base stations. , A transmission phase creation unit that creates and transmits a downlink frame to each base station from a transmission reference frame phase that is common to each base station, and a reception that detects the reception timing of the uplink frame from the base station. Phase control when estimating the transmission path delay amount based on the phase difference between the frame detection unit and the downlink frame and the uplink frame, and when the transmission phase creation unit creates the downlink frame from the transmission reference frame phase A centralized control station comprising: a phase comparison unit for changing the amount.