Data transmission in speech channel of DECT systems

The invention relates to a method for transmitting data in the voice channel between the base station and mobile station of cordless telecommunications systems with wireless interfaces to the DECT standard and speech coding devices.

For wireless telecommunication systems a European standard is set, which includes the transfer process and the frequency bands used for wireless communications in analog and digital telephone networks. This DECT (Digital European Cordless Telecommunication) refers to the radio interface between mobile wireless terminals and permanently connected to a telecommunication system base stations. Such systems operate with a so-called ADPCM speech coding means (Adaptive Differential Pulse Code Modulation), a speech encoding of 32 kbit / s, which allows a time-division multiplex transmission and a time division multiplex reception at the same frequency channel.

An unsecured ADPCM coded data transmission in the voice channel of a DECT system is subject to strong interference. As a result, unexpected faulty reactions of the connected data transmission devices, such. As loss of synchronization and the connection loss caused. The main cause is the presence in the DECT system high bit error rate.

To avoid the DECT system in transferring the language disturbing noise, cracking or the like, various measures are taken, such. As noise blocking or repetition of pulse frames. These measures, however, the shape of the original signal is distorted that it no longer be reconstructed. For voice transmission which has a subordinate role because the ear is less sensitive to disturbances.

If the DECT system does not distinguish between data transmission and language makes and it is optimized for voice transmission, the data transmission is very restricted.

The invention had the object of disclosing a technical solution for data communication over a DECT voice channel, which does not require supplementing the control of the voice channel, a voice channel of the standard voice channel of 32 kbit / s is given in both directions.

This object is achieved by the invention as it is set forth in claim. 1 Further advantageous features of the invention are subject of the subclaims.

The invention will be described with reference to a panel of three figures drawing. In the drawing, the<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>the block diagram of a mobile station MS, the</dd><dt>FIG. 2</dt><dd>the block diagram of an analog base station BSA and</dd><dt>Fig. 3</dt><dd>the block diagram of a digital base station BSD.</dd></dl>

A mobile station MS according to Figure 1 has a connection with F- and N-coded connectors NF for telephone and non-telephone provider, to which, for example, a modem or fax machine can be connected, and a V.24 interface connector, eg. B. for the connection of a personal computer (PC). Via an interface circuit A / B of the NF-terminal to an ADPCM codec is connected, which is in turn connected via a burst mode controller BMC for a channel to the transmitting / receiving device HF. The V interface is implemented through an interface circuit and a protocol computer PR to the burst-mode controller BMC. Between the logging site PR and the a / b interface a modem M is connected, the digital side of the modem M is connected to the logging site PR. By means of this modem M is monitored for existence of a modem-specific signaling, the a / b line. By connecting the digital interface circuit the V interface, it is possible, a request for transmitting data during a call connection over the A / B-line to detect.

With a reputation the ringing AC voltage is applied to the a / b interface and set the paging Indicator line of V interfaces. The device, which the first is an interface that has the possibility to transfer data. During data transfer, the ADPCM codec is switched off by the logging site PR. The protocol computer PR simultaneously takes on the backup on the radio interface (DECT system).

The analog base station BSA a DECT system according to Figure 2 is equipped in accordance with the mobile station MS with a modem M and a protocol computer PR. The trunks A / B are thus guided parallel to the ADPCM codec. The digital side of the modem M analyzes the logging site PR to detect a data transfer request. During a data transfer the ADPCM codec is switched off by the logging site as in the mobile station MS, which also realizes the backup on the DECT range between base station and mobile station MS BSA.

In a digital base station BSD of a DECT system according to Figure 3, for example, according to the ISDN standard, a modem is not required. Its function is taken over by a powerful logging site PR, the edited directly the digital information of the base channel. In the case of a data transfer PCM-ADPCM conversion is switched off in order to provide direct access to the data of the DECT link.

Different variants are possible for the method for transmitting data in a deratigen DECT system:<ul><li>External data transfer with an analog a / b connection of the base station;</li><li>External data transmission in a digital ISDN connection of the base station with the sub-variants of incoming and outgoing call;</li><li>Internal data transfer between handsets and a base station.</li></ul>

For all versions, an automatic recognition of the services provided. In the cases where this is not possible, is a device that accepts the call, counted as services determinative, such as telephone, standard fax machine, V24 PC-Fax.

For external data transmission with an analog a / b connection of the base station BSA is always first creates an acoustic link for documents through a telephone or fax machine, because it is unclear to determine whether an outgoing or incoming call comes. The modem M in the base station BSA is connected in parallel to the a / b interface. The modem M of the mobile station is also connected in parallel to be a / b interface. After a possible choice, possibly with Hörtonauswertung, when a possible fax signal the acoustic connection is suspended until either one of the two modems M is in synchronization or no synchronization takes place. If a synchronization in the base station BSA is, is caused that the modem M in the mobile station MS establishes a data connection. If a synchronization in the mobile station MS is concluded, the modem M of the mobile station MS on a data connection. Subsequently, the data transmission via the logging site PR is caused. This connection remains active as long as data is transferred. In case of loss of synchronization, the connection will be released to prevent possibly a modem connection via the acoustic path is established.

Busy at the mobile station MS, a personal computer to a V-terminal, the protocol converter PR recognizes the mobile station to the PC and transmits this to the base station BSA. This turns the modem M to the a / b interface, and waits for the synchronization. In this case, no acoustic connection is set up. After the end of data transfer, the connection is triggered.

For external data transfer at an ISDN connection to the base station BSD and an incoming call is decided by checking compatibility, whether and where the two basic channels is or is called. In a teleservice, z. B. "7 kHz telephony" the call is rejected. In a teleservice, z. B. "Facsimile G4" only the V-port is addressed. If a PC connected with a special driver that supports certain protocols is a data connection between the PC and ISDN is realized without modems M.

In a teleservice, z. B. "ISDN telephony 3,1 kHz" both the a / b connection and the ring indicator signal to the V-terminal is activated.

If the a / b connection is occupied, an acoustic connection is realized so that the protocol machine PR in the base station BSD and the modem M in the mobile station MS can decode a fax signal on the respective lines. In this case, the acoustic connection is discontinued to establish a data connection.

Is the V-terminal has been assigned, a data link with the base station BSD is set up directly.

For an outgoing call a connected to an ISDN connection base station BSD initially an acoustic connection is established for documents of a / b connection of the mobile station MS. After selecting the modem M of the mobile station MS and the logging site PR of base station BSD are connected so that a fax signal can be decoded. In this case, the acoustic connection is canceled and realizes a data connection. After the transfer, the connection is triggered.

Is the V-connection of the mobile station MS has been occupied, a data link with the base station BSD is set up directly.

An internal data transmission between two mobile stations MS to a base station BSA or BSD is built according to documents on the respective a / b ports, after one of the modems M in the mobile stations MS detects a fax signal during the voice connection.

If on the V connections of the mobile stations MS is busy, a data connection is set up directly. The protocol computer PR of both sides have to filter out the standard modem commands in an appropriate manner.