DE19548153C2 - Procedure for the synchronization of the exchange of characters between a private branch exchange and a base station - Google Patents

Description

The invention relates to a method for synchronizing the Air interfaces of those belonging to a radio network Base stations according to the DECT standard, in which the Base stations permanently connected to a DECT controller unit are.

The base stations of such a radio network are based on DECT standard called Fixed Parts. A synchronization of the Fixed parts among themselves is required to be in one Radio network z. B. according to the DECT standard, the uninterruptible Handover of handsets that portable parts according to the DECT standard enable.

For cordless systems, e.g. B. Telephone systems are the Transmission method and the frequency bands in analog and standardized digital telephone networks. On this for local limited cellular communication standard Digital European Cordless Telecommunication (DECT) different DECT systems. Common characteristic of such DECT systems, e.g. B. DECT-PABX or the like, is an instance, z. B. DECT controller unit called, to which the fixed parts be connected to provide mobility for users (roaming, handover).

Depending on the location and location of the fixed parts, they come together Differences in running time, on the one hand by the different cable lengths and to the other Time slot offsets in the Dect controller unit (Space / time division) or in the circuits Phase differences arise. Furthermore, it is necessary that  all fixed parts of a synchronous DECT radio network are the same Multiframe number on your air interface in the form of a so-called broadcasts so that the portable parts can Can detect synchronicity in a handover.

It is a procedure for the synchronization of the air interfaces of DECT base stations known (DE 44 07 794 A1).

The invention was based, for such an object System the runtime differences between the fixed parts compensate and additionally at the same time for the same Multiframe number for all fixed parts in the system to provide a so-called seamless handover, the one free movement - without impairments - during a Conversation within a radio network allowed to enable.

This object is achieved by the invention, as in first claim is set out. More beneficial Measures are the subject of the subclaims.

In the invention, the first for each fixed part Term of the connecting line is determined, for this the remaining delay times of the Dect controller unit and the Circuits added and as real system delay to the Transfer fixed part. The fixed part can now be based on a known maximum system delay to the determined Add a value to the real system delay that represents the Difference between the maximum system delay and the determined real system delay is. So you get for all fixed parts always the maximum system delay, regardless of the real system delay. Thus at All fixed parts compensated for the runtime differences. The absolute timing determined by the multiframe number must, however, still be achieved for all fixed parts.

The invention is described below using one of three figures existing drawing explained in more detail. Show in the drawing the

Fig. 1 shows the block diagram of parts of a DECT system, the

Fig. 2 shows the principle of a pulse frame used in DECT systems and the

Fig. 3 shows the principle of synchronization according to the invention.

The system according to the DECT standard is shown in FIG. 1 from a DECT controller unit DCU with a plurality of such. B. N = 1000, permanently connected base stations FP1. , , FPN. The base stations FP1. , , FPN are about z. B. each two digital lines, which are drawn in Fig. 1 as a double line, connected to the DECT controller unit DCU. Each of the digital lines has e.g. B. on two basic channels and an auxiliary or signaling channel.

According to the invention, either one of the base stations FP1 is used. , , FPN as main (master) station, the others are sub (slave) stations or a central resource, e.g. B. a digital signal processor DSP generates the synchronization information and all base stations FP in the system are sub (slave) stations. In the example shown in FIG. 1, FP1 or DSP are the main stations and the substations FP2. , , FPN or FP1. , , FPN.

Furthermore, one of the signaling channels of the main station FP1, provided with arrows in FIG. 1, is used for the synchronization of the base stations FP1. , , FPN used with each other. This channel is referred to as "synchronization channel" in the following text. The other signaling channels of the main station FP1 and the sub-stations FP2. , , FPN are used for normal signaling traffic. Alternatively, the synchronization information from the digital signal processor DSP into the synchronization channels of the FP1. , , FPN fed.

The main station FP1 or the digital signal processor DSP generate the system multiframe number and send it, always if it has been incremented for the purpose of synchronization to the synchronization channel. The system multiframe number is for the access control (Medium Access Control) the portable Parts to the fixed parts required for handover.

The DECT controller unit DCU switches this synchronization channel of the main station FP1 or the digital signal processor DSP to all signaling channels of the sub-stations FP2. , , FPN and to that of the main station FP1. Each station FP1. , FPN receives the system multiframe and generates an internal synchronized multiframe “FP multiframe sync”, as indicated in FIG. 3.

A multiframe according to FIG. 2 consists of 16 frames. Each of the 16 frames has e.g. B. 24 time slots, of which, for. B. 12 each for normal transmission and 12 for normal reception of the stations FP1. , , FPN can be used. The multiframe number is incremented every 160 ms. Each frame is 10 ms long, a multiframe thus comprises 16 × 10 ms = 160 ms. Since the DECT controller unit DCU is the clock master of the system and is used in ISDN-based systems with 8 kHz frames corresponding to 125 µs, one has as soon as the multiframes of the stations FP1. , , FPN are synchronized, the synchronization of the fixed parts to the clock of the DECT controller unit DCU is achieved, since the multiframe consists of 1280 8 kHz samples (1280 × 125 µs = 160 ms) or the frame of 80 8 kHz samples ( 80 × 125 µs = 10 ms).

The frame synchronization information is in the Given synchronization channel, it is only for the Synchronization used.

The main station FP1 or the digital signal processor DSP send a synchronized multiframe sequence over the Synchronization channel. The DECT controller unit DCU manages the synchronized multiframe sequence to all substations FP2. . . FPN and the main station FP1 continue. The synchronized Multiframe sequence is sent to all stations in the same 8 kHz frame FP1. . . FPN sent, but with the previously determined and thus receive known transit time difference there.

In every station FP1. , , FPN uses a phase locked loop for synchronization. In principle, this phase locked loop consists of a flip-flop and a counter, as shown in FIG. 3. If the flip-flop is set by the "FP-Multiframe-sync" signal generated internally by each fixed part, the counter begins to count and is received by the "System-Multiframe" signal received in the synchronization channel and formed by the main station FP1 or the digital signal processor DSP - sync "stopped. Each fixed part must now place its FP multiframe sync so that the measured time difference between FP multiframe sync and the system multiframe sync corresponds exactly to the real system delay, since the signal arrives at the fixed parts with a delay and the multiframe numbers must match. This means that the system is also synchronized with regard to the multiframe number. This synchronization method can also be used on ISDN interfaces when using the known ISDN channel structure, two basic channels, one auxiliary channel.

Claims (4)

1. A method for synchronizing the air interfaces of base stations belonging to a radio network according to the DECT standard, in which the base stations are permanently connected to a DECT controller unit, characterized in that one of the base stations (FP1) as the main station and the further ( FP2... FPN) as dependent substations or a digital signal processor (DSP) as main station with all base stations (FP1... FPN) as sub stations and that a signaling channel of the base station used as main station (FP1) or the digital one Signal processor (DSP) serves exclusively as a synchronization channel for the synchronization between the DECT controller unit (DCU) and the base stations (FP1 ... FPN) and under the base stations (FP1 ... FPN) itself. 2. The method according to claim 1, characterized in that the used as the main station Base station (FP1) or the digital signal processor (DSP) a synchronized system Multiframe sequence (System-Multiframe-sync) over the synchronization channel that sends on the part of the DECT controller unit to all base stations (FP1 ... FPN). 3. The method according to claim 2, characterized in that the synchronized system Multiframe sequence (system multiframe sync) delayed to the base stations (FP1... FPN) is sent. 4. The method according to any one of claims 1 to 3, characterized in that the Base stations (FP1 ... FPN) an internal synchronized multiframe signal (FP-Multiframe-sync) generate and this for synchronization with the synchronized Feed the system multiframe sequence (system multiframe sync) to a phase locked loop.