WO1998048534A1

WO1998048534A1 - Synchronization method between base stations in a multicell system

Info

Publication number: WO1998048534A1
Application number: PCT/DE1998/000892
Authority: WO
Inventors: Ulrich Boetzel
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-04-18
Filing date: 1998-03-27
Publication date: 1998-10-29
Also published as: DE19716344C2; DE19716344A1

Abstract

The invention relates to a synchronization method and device, intended to enable synchronized functioning of one or more units by repeated post-synchronization of these units in a predetermined manner. The inventive method and device are characterized in that the post-synchronization is conducted before a parameter, which could be influenced by this post-synchronization, has reached a particular size. It is thus possible to minimize impairments caused by the post-synchronization to a system containing the units to be post-synchronized.

Description

description

SYNCHRONIZATION PROCEDURE BETWEEN BASE STONES IN A MULTICELL SYSTEM

The present invention relates to a synchronization method according to the preamble of claim 1 and a synchronization device according to the preamble of claim 9, i.e. a synchronization method and a synchronization device in order to be able to operate one or more units synchronously in a predetermined manner while repeatedly resynchronizing them.

Methods and devices of this type can be found everywhere

Application where different or similar elements or units of a technical system should or have to work together. For example, reference is made to DE-B 196 05 490.

Such units can, for example, but are known to be by far not exclusively, a plurality of base stations of a radio system operating according to the DECT standard, in particular the base stations of a so-called multicell system with the ability for so-called intercell handover. The basic structure of such a system is illustrated in FIG. 1.

The system shown in FIG. 1 consists of a common switching station 1, base stations 21, 22 and 23 connected to it and telecommunications terminal equipment in contact with them. Up to 12 of the telecommunication terminals can be connected to each of the base stations 21, 22 and 23. In the example under consideration, the telecommunications terminal devices may be mobile telephones 31, of which only one is shown in FIG. 1. While the switching station 1 and the base stations 21, 22 and 23 are connected via connecting lines 11, 12 and 13, communicate the base stations 21, 22 and 23 and the mobile telephones 31 via radio with one another.

The area within which a mobile telephone 31 can make contact with a respective base station m is referred to as a cell. The cells of the base stations 21, 22 and 23 are illustrated in FIG. 1 by circles 41, 42 and 43 surrounding the relevant base stations 21, 22 and 23.

In the example under consideration, cells 41, 42 and 43 are so-called mobility areas, in which mobile phone 31 can be moved at low speed (<30 km / h) even during a call.

If the cell of the base station in contact with the mobile phone 31 is left, the connection between the mobile phone and the relevant base station is broken. Such a disconnection can be prevented in systems with the intercell handover capability already mentioned above, by automatically establishing a new connection to a next base station (the mobile phone is indented at a next base station) before the connection is broken off when the cell phone 31 is already inside the cell of this next base station.

If, for example, the mobile telephone 31 is moved along a path designated W in FIG. 1, it is initially registered with the base station 21 and is then first transferred to the base station 22 and finally to the base station 23.

Such rebookings enable a seamless connection of the mobile telephone 31 to the base stations 21, 22 and 23. If the base stations 21, 22 and 23 run synchronously, calls made during the rebooking can be continued without interruption (undisturbed). According to the DECT standard, the base stations are considered to run synchronously if they have a maximum difference of 4 μs in relation to the time at which a burst is sent (bit 0 of the same) and if they are slot, frame and scan synchronous (see the ETSI document ent ETS 300 175 - 2, section 4.2.5).

It is easier to understand what is behind this definition if you know the format of the data that is transmitted between the base stations and the mobile phones registered there. This data format is - if necessary in the present case - explained below with reference to FIG. 2.

The data transmission between a base station and the (up to 12) mobile telephones registered there m systems operating according to the DECT standard takes place in m units of frames. As can be seen from FIG. 2, such a frame, more precisely the DECT full slot frame considered here, is composed of 24 so-called timeslots or slots (full slots). The first 12 of the 24 slots are transmitted from the base station to the cell phones, and the subsequent 12 second slots are transmitted from the cell phones to the base station. More specifically, the zero slot of each frame from the base station to a zero cell phone, the first slot from the base station to a first cell phone, the second slot from the base station to a second cell phone, ..., the eleventh slot from Base station to an eleventh mobile phone, and vice versa the twelfth slot from the zero mobile phone to the base station, the thirteenth slot from the first mobile phone to the base station, the fourteenth slot from the second mobile phone to the base station, ... and the twenty-third slot from the eleventh Mc- transfer the telephone to the base station. A frame or the 24 slots of a frame are transmitted within 10 ms. Each slot comprises 480 bits and is transmitted around 417 μs. As can be seen from FIG. 2, the 480 are distributed over a 32-bit wide sync field, a 388-bit wide D-field, a 4-bit wide Z-field, and a 56-bit wide guard space field.

320 bits are reserved within the D field for the transmission of the voice data of interest.

The base station can thus send 320 bits of voice data to each of the mobile phones within 10 ms and receive the same amount of voice data from each of the mobile phones; the transmission rate for voice data between the base station and each of the mobile telephones is thus 32 kbit / s in each direction.

If a call just being made is not to be disturbed or interrupted by rebooking the mobile phone from one base station to another base station, it is recognizable and in accordance with the aforementioned ETSI definitions that the base stations must be bit, slot - and run synchronously. That an x-th bit of a y-th slot of a z-th frame must be sent or received by all base stations essentially simultaneously.

In addition, as already mentioned above, the base stations must run in scan-synchronous fashion; So-called scan counters in the base stations determine which slot is to be transmitted with which frequency.

In order to be able to ensure such synchronization of the base stations, a more or less frequent and regularly repeated (re) synchronization of the base stations is required. The resynchronization is always on Initiated by the switching station 1 by the base stations 21, 22 and 23 itself.

The most common (m time intervals of usually far less than 1 second) is understandably the bit-based resynchronization of the base stations 21, 22 and 23. This post-synchronization is initiated by the switching station 1, for which purpose it simultaneously sends a synchronization signal to all base stations 21, 22 and 23, by means of which the base stations can in each case check whether they are running bit-by-bit synchronously (whether they are transmitting a specific bit to a one specified by the switching station Send or receive time). If necessary, a corresponding correction is made in the base stations. The correction takes place at a time at which the above-mentioned guard space field of a slot is transmitted. Said guard space field does not contain any useful data and thus makes it possible to carry out the bit-based resynchronization without disturbing the operation of the base station and / or the mobile telephones connected to it.

The situation is different with the slot, frame and scan-like resynchronization of the base stations. Although this is only carried out relatively rarely (e.g. once a day), it represents a massive intervention in the system.

Like the bit-based resynchronization of the base stations, their slot, frame and scan-based resynchronization is also initiated by the switching station 1. The post-synchronization can be carried out in different ways.

A first possibility is to set (reset) all base stations in a defined state at the request of the switching station. Such resetting inevitably disrupts or interrupts the operation of the base stations, both asynchronously current as well as the base stations running up to then synchronously.

In order to avoid such disruptions as far as possible, it can be provided that such a re-synchronization is only carried out if there is actually an asynchronicity. For this purpose, the switching station first ascertains whether the base stations are running synchronously or asynchronously, by obtaining appropriate information (whether slot, frame and scan counters provided for the base stations have values specified by the switching station). Only if it turns out that at least one of the base stations is running asynchronously is the subsequent synchronization of the base stations then ordered. Such a procedure can minimize operational disturbances in the system caused by post-synchronizations, but the repeated bidirectional communication required for this requires a not inconsiderable effort between the switching station and the base stations. Apart from this, the exchange of status and control information (signaling data) between the switching station and the base stations is more or less completely necessary for the post-synchronization for a longer time (several milliseconds); an exchange of other signaling data between the switching station and the base stations, which may be necessary, cannot take place during this time, or at most only to a limited extent.

None of the options for post-synchronization mentioned are fully satisfactory; undesirable impairments of the system occur in both cases.

The present invention is therefore based on the object of developing the synchronization method according to the preamble of patent claim 1 or the synchronization device according to the preamble of patent claim 9, that impairments of the system containing the units to be synchronized caused by post-synchronizations can be reduced to a minimum.

According to the invention, this object is achieved by those in the characterizing part of patent claim 1 (method) or by the in the characterizing part of patent claim 9 (device).

Accordingly, it is provided

- That the resynchronization is initiated before a parameter that can be influenced by this should have a certain size (characterizing part of patent claim 1) or

- That a synchronization control device is provided, through which the resynchronization is initiated before a parameter that can be influenced by this should have a certain size (characterizing part of patent claim 9).

As a result, the units that are to be operated synchronously can each decide for themselves whether they have deviations from the current target state, and any resynchronization that may need to be carried out (adjustment to the target state) can also be made immediately, i.e. be carried out to the required extent without separate external initiation and / or control.

If the point in time of the initiation of the post-synchronization and / or the type of post-synchronization is determined so that the parameters of a particular unit which deviate from the target state or the target size after the post-synchronization have exactly the values that they would have , if the synchronized unit would have run synchronously, the desired post-synchronization can then can be achieved if not all units (of any number) that are to be synchronized are re-synchronized.

Such a synchronization is advantageous in several respects: on the one hand - unlike before - it is not necessary that all units to be brought in sync are reset or manipulated in any other way, and on the other hand the communication between a synchronization control device initiating the resynchronization and the units to be synchronized to a minimum.

A method and a device have therefore been found, the use of which makes it possible in a simple manner to reduce to a minimum the impairments caused by post-synchronizations of a system containing the units to be post-synchronized.

Advantageous developments of the invention are the subject of the dependent claims.

The invention is explained in more detail below on the basis of an exemplary embodiment with reference to the drawing. Show it

Figure 1 shows the structure of a so-called multicell DECT system, and

FIG. 2 shows the format of the data that are exchanged between a base station and telecommunication devices that can communicate with it.

The method according to the invention and the device according to the invention are described below on the basis of the re-synchronization of base stations of a DECT radio system which are to be synchronized with one another. However, the application of the invention is not restricted to such an application. limits; in principle, it can also be used with any other units to be synchronized or m synchronized.

The basic structure of the DECT system under consideration does not differ from the system illustrated in FIG. 1, apart from the details relating to the resynchronization of the base stations.

The format of the data illustrated in FIG. 2, which is exchanged between the base stations 21, 22 and 23 and the telecommunication end devices connected or connectable thereto (represented by the mobile telephone 31), is also unchanged. For the sake of completeness, however, it should be mentioned at this point that in addition to so-called full slots (480 bits) shown in FIG. 2 and described with reference thereto, there are also half slots (240 bits) and double slots (960 bits).

As before, a more or less frequently and regularly repeated check and, if necessary, re-synchronization of the base stations is still required, these being running or having to be bit, slot, frame and scan synchronous.

The bit synchronicity of the base stations can be achieved as before or in any other way.

The slot, frame and scan synchronicity is evaluated and, if necessary, adjusted by the slots, frames or

Scanned paying slot, frame and scan payers checked and enforced. The way in which this is done in the example considered here differs fundamentally from previous practice.

The only thing that remains the same is that the resynchronization is initiated (initiated) by the switching station 1. The For this purpose, switching station 1 sends a post-synchronization command to all base stations of the system.

The time at which the post-synchronization command is sent is selected so that at the time the base stations receive the command, the parameters to be synchronized must have predetermined values (sizes) which are known to the base stations concerned. The predetermined values of the parameters to be brought into synchronization are either fixed or changeable in the base stations and / or are transmitted to the base stations together with the resynchronization command or on other occasions and / or are evaluated by evaluating information obtained otherwise (for example by evaluating a time information sent by a satellite or other transmitter).

When the post-synchronization command is received, the base stations determine whether the parameters to be synchronized have the predetermined values. More precisely, each base station checks whether the payer levels of their slot, frame and scan counters correspond to the target values known to the base stations.

Those base stations at which the check shows that the payer levels correspond to the target values do not have to be synchronized; for these base stations, the post-synchronization commanded by the switching station ends with the determination of the still existing synchronicity.

The situation is different for the base stations, where the check shows that one or more of the meter readings to be checked do not correspond to the target values. A post-synchronization is carried out in these base stations, by means of which they are put into a state in which they would have been if the base station in question had run as intended (synchronously). To do this, at least said payer levels are brought to values they would have been if the base station in question had run as intended (synchronously) by then.

The base stations must be able to specifically change the payer levels and / or other base station states through the synchronization in such a way that this results in the required adjustment to the current target values or target states.

If the base stations can only change the payer status and states by a complete or partial retraction or the like and therefore or for other reasons can only set very specific payer levels and / or states, the synchronization command from the switching station must be sent at a time chosen in this way is that the predetermined payer levels and states that arise as a result of performing any synchronization that may be required correspond exactly to those payer levels and states that would have occurred if the base station in question had run as intended (synchronously).

If, on the other hand, the base stations are able to synchronize themselves in such a way that more or less freely selectable payer levels and states occur, the synchronization command can be issued at any point in time, although it must also be ensured in this case that the predetermined ones Payer levels and states that arise as a result of performing any synchronization that may be required correspond exactly to the payer levels and states that would have occurred if the base station in question had run as intended (synchronously).

The synchronization of a base station is usually the termination of the connections to the mobile phones registered there blow dry. It can therefore be considered to terminate the existing connections in a defined manner (if possible to have a login to neighboring base stations that are not currently being synchronized). Regardless of this, it should be ensured after the synchronization that the aborted connections are automatically re-established.

From the above explanations it is clear that the synchronization of the base stations of a DECT system does not interfere with the operation of the system more than is absolutely necessary under the circumstances; Impairments only occur in the area of those base stations whose operation is disrupted anyway.

Claims

claims

1. synchronization method to be able to operate one or more units (21, 22, 23) with repeated resynchronization in the same m predetermined manner in a synchronized manner, the resynchronization taking place by resetting one or more parameters to specific sizes, characterized in that the resynchronization a resynchronization unit is initiated at a time which is selected so that the resynchronization is ended exactly when the parameters of synchronously running units that can be influenced by the resetting have the sizes that the relevant parameters of the resynchronizing unit have after resetting.

2. Synchronization method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the initiation of the resynchronization is carried out by a central synchronization control device (1).

3. Synchronization method according to claim 1 or 2, so that the resynchronization is initiated simultaneously for all units (21, 22, 23) to be operated synchronously.

4. Synchronization method according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the initiation of the resynchronization hm by the units (21, 22, 23) to be operated synchronously is first checked whether a resynchronization is necessary at all in the unit concerned.

5. synchronization method according to claim 4, characterized in that the actual synchronization of each of the units (21, 22, 23) to be operated synchronously takes place only when the unit in question has determined that a re-synchronization is required.

6. Synchronization method according to one of the preceding claims, that the resynchronization of a unit (21, 22, 23) to be operated synchronously takes place with complete or partial resetting of the same.

7. Synchronization method according to one of the preceding claims, that the resynchronization of a unit (21, 22, 23) to be operated synchronously is carried out by resetting one or more parameters to certain sizes.

8. Synchronization method according to one of the preceding claims, characterized in that the resynchronization is initiated at a point in time which is selected such that any synchronization to be carried out is terminated precisely when the parameters which can be influenced thereby should have the sizes which they follow the post-synchronization.

9. Synchronization device in order to be able to operate one or more units (21, 22, 23) with repeated resynchronization of the same in a predetermined manner, the resynchronization taking place by resetting one or more parameters to certain sizes, characterized in that a synchronization control device is provided, by which the post-synchronization is initiated at a time which is selected so that the post-synchronization on is ended exactly when the parameters of synchronously running units that can be influenced by the resetting have the sizes that the relevant parameters of the unit to be resynchronized has after resetting.

10. Synchronization device according to claim 9, so that the synchronization control device is designed to initiate a re-synchronization of base stations (21, 22, 23) of a DECT system to be operated synchronously.

11. The synchronization device as claimed in claim 10, so that the parameters which can be influenced by the post-synchronization are number levels of slot, frame and scan numbers of the base stations (21, 22, 23) of the DECT system.