Process for transmitting data, in particular GSM data

The invention relates to a method for transmitting data, in particular GSM-data between at least two participants.

State of the art

In previous GSM data connections, in particular for digitized speech data between mobile subscribers via a communication network, for example, the public switched telephone network (PSTN - Public Switched Telephone Network), the GSM data in GSM format in the frame format of the communications network - 64 kbit / s PCM for PSTN - implemented by a recoding / a transcoder. Such transcoding occurs when mobile radio system DMCS 900 in the base stations or on the A-interface in the transition to the PSTN communication network. According to GSM Recommendation 0860/0861 digital speech transmission in so-called "TRAU frames" is carried out (transcode and rate adapter unit); ie transmission frame in the 16 kbit / s format in FR (Full Rate) transmission and 8 kbit / s or 16 kbit / s in HR (Half Rate) transmission.

From the <patcit id="pcit0001" dnum="US5091945A"><text>US 5,091,945</text></patcit> It is known to transmit only data in lieu of voice signal parameters (speech parameters), from which the user data can be reconstructed.

From the <patcit id="pcit0002" dnum="EPA0332345A"><text>EP-AA-0332345</text></patcit> It is known to carry out the transmission of speech in a first data flow and the transmission of synchronization patterns.

The published after the priority date of the present application International Patent Application <patcit id="pcit0003" dnum="WO9623297A"><text>WO 96/23297</text></patcit> It is known to carry out the transmission of speech in a first data stream and transmission of ID information as well as speech parameters for speech data reconstruction in a second data stream. A major disadvantage of the in<patcit id="pcit0004" dnum="WO9623297A"><text>WO 96/23297</text></patcit> disclosed data transmission method is that the identification information is transmitted continuously. The<patcit id="pcit0005" dnum="WO9623297A"><text>WO 96/23297</text></patcit> corresponding to the European patent application <patcit id="pcit0006" dnum="EP806032A"><text>EP 806 032</text></patcit> and 54 (3) EPC only in accordance with Art. may be significant.

ADVANTAGES OF THE INVENTION

The method with the features of the main claim has the advantage that for a handover of a TFO with two involved TFO-capable Umcodiereinrichtungen (TCE 1, TCE 2) to a non-TFO-capable recoding (TCE3) in the first recoding (TCE 1) provides the following measures:<ul><li>The data stream between the Umcodiereinrichtungen (TCE1, TCE2) is divided into a first data stream with voice samples, in particular PCM speech samples for transmission and a second data stream with signal parameters for speech data reconstruction, in particular TRAU frame;</li><li>the thus divided data streams are transmitted during a TFO (Tandem Free Operation) operation simultaneously from the first recoding (TCE 1) via an A-interface, is connected via the first recoding (TCE 1) with a central office;</li><li>when a handover from the second code conversion device (TCE2) to a non-TFO-capable recoding (TCE3) is registered discontinuation from the second code conversion device (TCE2) incoming signal parameters in the first code conversion device (TCE1), and it passes a first predetermined time ( T_release), Where after expiry of the first predetermined time (T_release) Incoming data is from the A-interface are encoded, wherein in the A-interface outgoing data stream to the TRAU frames decoded speech "PCM *" are inserted, wherein the first transmitted TRAU is a TRAU *, wherein the speech samples "PCM *" the speech samples with the processed high-order 6 bits, the TRAU * is an identification information; and</li><li>a second predetermined time (T_sync) In the first code conversion device (TCE1) starts, wherein the first code conversion device (TCE1) after the second predetermined time (T_sync) Falls back to normal operation, are in the encoded or decoded speech samples.</li></ul>

it is that results in an improvement of the quality of transmitted data, in particular GSM voice data, in particular by Tandem operating in connections between mobile subscribers is particularly advantageous. Due to the simultaneous transmission of samples z. B. PCM values, and signal parameters for speech data reconstruction, the interference in a transcoder, which is not provided for the tandem free operation with transparent through-connection of TRAU frames is less. Because there are still transmit voice data in the first data stream and in the transmission of identification information.

Also in handover operation, the invention provides advantages. The invention is easy to implement in existing systems. Only the speech transcoder of a network are affected. For example, of the 8 bits per speech sample, the two least significant bits replaced by a TRAU frame (speech is then reduced 6 bits), can be in which identification information and / or synchronization information appears to synchronize the transcoders.

By squeezing the lowest bits to zero in the transmission of voice during a call setup, the voice quality is improved compared to previously proposed methods.

In a handover, ie when changing to another transcoder, frame loss can be determined quickly, or be prevented from invalid frames are processed further as TRAU frames. A not for tandem-free operation equipped transcoder can already process speech samples during a synchronization process. If after completion of synchronization instead of the samples a reduced idle pattern is sent, the speech decoder of the transcoder can be switched off or used for other purposes, eg. As for transcoding Full Rate / Half rate in the downlink path are used.

drawings

<ul><li><figref idrefs="f0001">figure 1</figref> shows the structure of a connection between two subscribers,</li><li><figref idrefs="f0001">figure 2</figref> the data transmission interface in chronological sequence,</li><li><figref idrefs="f0002">figure 3</figref> in the <figref idrefs="f0001">figure 2</figref> Patterns used.</li><li><figref idrefs="f0002">figure 4</figref> the handover operation.</li></ul>

Description of Embodiments

In the existing GSM network (fixed network side), for example, the DMCS 900 network, transcoding; ie transcoding the voice data from the given TRAU (Transcode and Rate Adaptation Unit) -. Format according to GSM Recommendation 08.60 to the transmission format of the communications network, eg the public switched telephone network PSTN (PCM values ​​in the 64 kbit / s frame format) always carried out.

From participants Tl1 a connection to the subscriber Tl2 is switched. The transcoder, the following named transcoders TCE 1, which is associated with the subscriber TI1, sends the traffic channel of the A-interface A-IF identification information, which the connected transcoder TCE 2 signals (tandem), that it is a TFO (tandem free operation) - capable transcoder is. The two transcoders switch after they have recognized this signal in the TFO and exchange the voice parameters. Does the transcoder to a non-TFO-capable transcoder, it will not receive the code of the site within a certain period and therefore will return to normal operation, in which he language (speech) encoded or decoded.

The interfaces of the transcoder TCE1, TCE2 to the subscribers TL1, TL2, z., Via base stations BTS are connectable, are designated by ATER-IF. The Switching between transcoders is designated as MSC

call setup

During call setup, the detection of the transfer at the A interface (A-IF) in the lower (least) two bits of the A-samples of 00 to 00 ≠ the trigger. The trigger is necessary, to T_trigger delayed.

This trigger condition is selected so that it satisfies the following behavior of the switching equipment MSC:<ol><li>a) The MSC sends a not-busy transcoder an IDLE pattern (idle pattern).</li><li>b) The MSC switches when connecting first a loop between the input and output of the line to the transcoder before it switches.</li><li>c) The MSC switches the two directions through at different rates. This can with T_trigger be compensated.</li></ol>

Arbitration process

The transcoder TCE1 sends the A-IF interface instead of the conventional 8-bit PCM samples now in the least significant 2 bits of these samples a TRAU frame (this has been used for the transmission between the radio station and transcoder and contains signal parameters for Nutzdatenrekonstruktion). The data stream between the transcoders TCE1 TCE2 and is therefore divided into a first data stream having samples (PCM) values ​​and a second data stream with signal parameters in particular TRAU frames. Both data streams are transmitted simultaneously in particular during a connection setup phase. In such a TRAU frame, TRAU * is sent identification information for a predetermined period of time. Once the TRAU * is detected by the remote station, is switched to the TFO. The process is controlled by a timer T_sync monitored. When it runs out, there is a transition to normal operation.

Alternatively, n, n can be &lt;9 bits used for signaling with arbitrary frame structures.

Alternatively, to dispense with the TRAU * identification information and only the TRAU frame synchronization information are used.

As long as the synchronization T_sync running, are following the TRAU * identification information from the A_ter-IF Incoming TRAU frames sent in the low-order 2 bits of the A-IF. This allows for the remote station an immediate transition to TFO after receipt of the TRAU * identification information. The high-order 6 bits of the samples are filled with the processed high-order 6 bits PCM *. This reduces the quality loss if the other side is not a TFO-capable transcoder.

If within one repetition time T_repeat (T_repeat &lt;T_sync) No TRAU * received, is again a TRAU * sent. The purpose of this second TRAU * is described handover case.

TFO (Tandem Free Operation)

After recognizing the TRAU * at A-IF are subsequently the following TRAU frames (-Inhalte) to A_ter-IF Passed. The adaptation of the control bits and the timing of the A_ter-TRAU Frame is adapted to local conditions. Unusable frame from the remote terminal (BFI = 1, TRAU *) are replaced by the previous frame and muting is optionally initiated. Any jitter in the TRAU frame length of +/- 2 bits must also be compensated. Codec conversions, DTX and muting functions are also carried out in this direction. Advantage is that no signaling talking is required if change local conditions.

In the opposite direction, TRAU frames are from A_ter-IF The A-IF transparently passed through. The upper 6 bits are replaced instead of PCM * by IDLE * (010101). This allows the disconnection of the transcoding function, since this capacity in an FR / HR system environment if necessary for HRC - is needed FRC implementation &lt;&gt;. It also avoids an additional term. TRAU frames with data content can also be sent through transparently.

Instead of IDLE * can also be a modulo-n counters are installed, permitting even more reliable error detection.

handover

The handover case is to be broken down into the three cases described below.

a) Handover to a TFO-capable transcoder

First, the termination of the incoming TRAU frames is recorded and a timer T_release started. The transcoder after a certain time a TRAU * from the newly connected transcoder TCE3, T stops_release, Sends a TRAU * itself and remains in TFO. The transcoder can thus remain in TFO operation.

Can the first TRAU * not be received because the switching MSC has not yet been connected, its second TRAU * is detected, however, and leads to the TFO.

To as quickly as possible to detect the handover from transcoder TCE 2 to transcoder TCE3 and around may not trigger on a loop at A-IF, the newly connected transcoder TCE3 is (<figref idrefs="f0002">Fig. 4</figref>) Send the call setup "PCM +". "PCM +" are set to '00', in order not pretend TRAU sync bits, the PCM data to the lower 2 bits. This enables to suppress interference at the subscriber.

b) Handover to a non-TFO-capable transcoder

First, the termination of the incoming TRAU frames is recorded and a timer T_release started. The timer T_release expires and the transcoder returns to the arbitration, in which he, the incoming data at the A-IF encoded. In the outgoing data stream at A-IF he adds to the TRAU frames now decoded PCM samples "PCM *" a. The TRAU sent first is a TRAU *. The timer T_sync is started. As before timer T_sync no TRAU * has been received, it is reverted to normal operation.

c) handover from a non-TFO-capable transcoder

If the previous remote location not TFO capable, the transcoder can not recognize the handover. For the new remote site, it is a normal handshake, in which it, if it is TFO capable, first sends a TRAU *. The transcoder, also sends a TRAU * and goes into TFO. If the switching is delayed, the first TRAU * is lost and the second TRAU * after T_repeat leads to success.

The line breaks

The call is ended, either by the demolition of the TRAU frames on the A_ter-IF Or initiated by detected errors on the A-IF. The procedure is then as in the case 'handover to a non-TFO-capable transcoder.

Fault Conditions in TFO

a) Individual errors on the A-IF

Individual errors can not be detected in the data bits of the TRAU frames. Individual errors can only be detected in the synchronization of the TRAU frames. Measures are therefore not derive from it, since no information on the data bits of the TRAU frame is given.

b) burst errors on the A-IF

Strongly disturbed TRAU frame is forwarded to the Ater-IF, that possibly strong noise may occur at the subscriber. Therefore, it is assumed in detecting a single error by a burst error, the remainder of the TRAU frame is discarded and replaced by the TRAU frame previously transmitted. The following measures prevent noise largely:<ul><li>1. Double fault monitoring:<ul><li>1.1 by controlling the (TRAU) frame synchronization</li><li>1.2 by monitoring the IDLE *; pattern in the upper 6 bits</li><li>an alternative to 1.2: monitoring by a periodic pattern, for example, a modulo n counter, whose counts are transmitted within the first data stream.</li></ul></li><li>2) Error concealment buffer A buffer with approximately x ms (here 5ms) allows the data to the last TRAU sync bit to save and substitute in case of failure by the last valid data.</li></ul>

If the burst is very long, 'handover to a non-TFO capable transcoder as will be the case, passed in normal operation.

Preferred examples of the present invention will become apparent from the following aspects:<ol><li>1. A method of transmitting digitized data between a calling and a called subscriber unit (TI1, TI2) of a mobile network, wherein a predetermined frame format is used for transferring, with the following measures:<ul><li>Switching a connection between the subscriber units (TI1, TI2);</li><li>Signaling by a first Transkodiereinrichtung (TCE 1) that is associated with the calling subscriber unit (TI1), a second Transkodiereinrichtung (TCE 2) that is associated with the called subscriber unit (TI2), that it is the first Transkodiereinrichtung (TCE 1) to a TFO ( tandem Free operation) - enabled Transkodiereinrichtung concerns, said signaling takes place for a predetermined maximum period of time;</li><li>After having recognized the above-mentioned signaling flipping the Transkodiereinrichtungen (TCE 1, TCE 2), in a TFO mode; and</li><li>Replacing speech parameters between Transkodiereinrichtungen (TCE 1, TCE 2); wherein the data stream between the Transkodiereinrichtungen (TCE1, TCE2) which the subscriber units (TI1, TI2) are associated, both during the time phase of the signaling, as well as during the time phase of the exchange of speech parameters in a first data stream with speech samples and a second data stream is divided; and wherein the second data stream during the time phase of the signaling information and identification during the time phase of the exchange speech parameters containing speech data reconstruction.</li></ul></li><li>2. The method according to aspect 1, <b>characterized in that</b> for the signal parameters of the second data stream, the known systems for mobile TRAU (Transcoding rate adaption unit) frames are used.</li><li>3. The method according to aspect 1 or 2, <b>characterized in that</b> the first data stream from the high-order bits of a parallel bit sequence and the second data stream from the corresponding low-order bits of this bit sequence is.</li><li>4. The method according to aspect 3, <b>characterized in that</b> the second data stream is formed by reducing the data of the first data stream.</li><li>5. The method according to aspect 3 or 4, <b>characterized in that</b> the more significant bits are transmitted as PCM samples.</li><li>6. The method according to any one of aspects 1 to 5, <b>characterized in that</b> the second Transkodiereinrichtung (TCE 2) the first Transkodiereinrichtung (TCE 1) indicates that it is in the second Transkodiereinrichtung (TCE 2) to a TFO-capable Transkodiereinrichtung after the second Transkodiereinrichtung (TCE 2) of the first Transkodiereinrichtung (TCE 1) has received the identification information ,</li><li>7. The method according to any one of aspects 1 to 6, <b>characterized in that</b> the identification information to a transition to the TFO embedded is transmitted in TRAU frames between Transkodiereinrichtungen (TCE 1, TCE 2).</li><li>8. The method according to any one of aspects 1 to 7, <b>characterized in that</b> sent the signal parameters in TRAU frames immediately after the transmission of the identification information.</li><li>9. The method according to any one of aspects 1 to 8, <b>characterized in that</b> from the TFO between Transkodiereinrichtungen (TCE 1, TCE 2) a handover is possible to another TFO-capable, or to a non-TFO-capable Transkodiereinrichtung.</li></ol>