Method for modifying connections in a data compression-based communications system

The present invention relates to a method for replacing data frames arriving in a switching center of a communication system based on data compression, such as according to the UMTS standard.

The Universal Mobile Telecommunication System (UMTS) is one of several mobile radio systems that provide a variety of services to the subscriber of a mobile terminal.

UMTS operates in the ranges of 1885-2025 MHz and 2110-2200 MHz and also allows data rates of up to 2 Mbps over the previously known functionality of the narrow band mobile radio systems.

It is a goal of the mobile radio system UMTS to provide the subscriber with a uniform mobile radio system of the third generation worldwide and for the first time roaming and handover between technically different networks, such as GSM (Global System for Mobile Communications) with dual- Mode terminals.

Communication networks based on UMTS standards require the functionality in the UMTS mobile switching centers (UMSC) due to the selection of different codec modes for a subscriber A and a subscriber B or when TrFO (transcoder free operation) , Transcoding existing connections from an AMR (Adaptive-Multi-Rate) codec mode to another AMR codec mode. Via a voice channel of an air interface of a mobile radio network, a call of a subscriber is compressed, such as, for example, by means of an AMR codec for UMTS. An AMR codec contains an algorithm specific to it which compresses voice data. An RNC (radionetwork controller) of a mobile radio network, before setting up a UMTS voice connection, issues a set of AMR modes with a switching center, via which the voice connection is to run. In order to be able to feed further information into the connection or the call, it is necessary to enter the connection within the switching center. Here again, it is necessary to encode existing connections from an AMR codec mode back to the same or to another AMR codec mode, for example for feeding TDM-based sound.

Such a transcoding is conventionally performed by decoding data transmitted in a first codec mode into 160 linear samples with 13 bits and a subsequent encoding into a second codec mode. For this purpose, data transmitted to the switching center within a data frame transmitted by a radio network UTRAN at a distance of 20 ms is decoded by means of a decoding device, the data being stored in a first AMR (Adaptive-Multi-Rate) codec mode Were encoded. If, for example, speech data is concerned, the speech data contained in the speech frame are converted into linear pulse code-modulated (PCM) words with a length of, for example, 13 bits after their decoding. These are then compressed according to a so-called A / μ-law into words with an information content of 8 bits and are time-multiplexed over the time-division multiplexing link field. The time-multiplexed data are decompressed into linearly pulse-coded words having an information content of, for example, 13 bits, and then encoded in a new AMR codec mode.

The use of the synchronously functioning TDM coupling field for inserting tones and / or announcements requires coding and decoding, which requires additional coding and / or decoding system units.

Depending on different network sections within the UMTS standard-based communication network, different standard UMTS versions can be used within a connection.

The <patcit id="pcit0001" dnum="WO0191489A1"><text>WO 01/91489 A1</text></patcit> Discloses a method in a UMTS communication network for modifying a connection between sending and receiving subscribers by removing data frames.

It is an object of the present invention to provide a method by which it becomes possible to replace data frames of a connection with other data frames so that an insertion of, for example, tones and / or announcements without a decoding on a TDM basis and Subsequent decoding on an ATM basis.

The object is achieved according to the invention by a method according to claim 1. Further advantageous embodiments of the present invention are listed in the corresponding subclaims.

According to claim 1, a method for modifying a connection between a transmitting and a receiving subscriber in a data compression-based communication system within a switching center is provided, wherein a data frame which is formatted in the switching center and formatted according to a framing-protocol is independent of the length Of the data frame is replaced by a new data frame formatted according to the frame protocol so that additional information can be fed into the connection without loss of quality and time.

The data frames can have different lengths.

In a preferred embodiment of the method according to the invention, a UMTS system is selected as a communication system based on data compression. It is also possible to use a GSM edge radio access network (GERAN) system. The method according to the invention can also be used for replacing IP data frames, the transmission of which takes place by means of the ATM (asynchronous transfer mode) transmission technology, where IP data frames are then replaced by IP data frames by the method according to the invention.

Preferably, both the data frame arriving in the exchange station as well as the new data frame are / are segmented as a function of their respective length into one or more AAL2 packets which are each provided with a packet header.

Furthermore, in the respective packet header fields of the AAL2 packets, the data frame to which the respective AAL2 packet is allocated is displayed.

In a particularly preferred embodiment of the method according to the invention, it is indicated in the respective packet header fields of the AAL2 packets whether further subsequent AAL2 packets are to be assigned to a data frame.

This means that not just every data packet arriving in the exchange is assigned exactly one data packet, but that a data frame is segmented by two or more AAL2 packets, which in turn are forwarded by means of ATM cells.

In order to ensure that the complete data frame initially received in the exchange is segmented, which is segmented into one or more AAL2 packets, which are then also forwarded in the appropriately correct sequence, it must in each case be detectable whether an AAL2 packet is an end packet or not. Furthermore, it must be recognizable whether an AAL2 packet represents a subsequent packet of a preceding AAL2 packet and whether a subsequent packet exists for an AAL2 packet.

According to ITU-T Recommendations I.362.2 and I.366.1, the data packets in the packet header, in a UMTS system these are CPS packets with a corresponding CPS packet header, are marked in order to determine the membership of a data frame. For this purpose, a subfield of the packet header, namely a so-called UUI field (user-to-user indication), is used. If the data frame contains only one data packet, a UUI value &lt;27 is used. If the data frame contains several data packets, UUI = 27 is set for all data packets of the data frame, then UUI &lt;27 is set only for the last data packet. To replace data frames, it is first necessary to recognize these data frames as a whole. According to a preferred embodiment of the method according to the invention, it is not necessary to restore the complete data frame from the individual data packets of a data frame. It is sufficient to check a partial field of the packet header, namely the already described UUI field of each data packet, which is referred to as "UUI monitoring". A new data frame begins after a package with UUI &lt;27.

If the replacement of data frames is to be started, the end of a data frame (packet with UUI &lt;27) is awaited for the connection to be modified. This is to avoid that incomplete frames arrive. Thereafter, complete frames are replaced by complete frames.

An essential point of the invention is that further information can be fed into the switching center in a connection between a transmitting and a receiving subscriber, circumventing an encoding and a decoding device and a time division multiplexing coupling field.

The length of the new data frames are now selected specifically for the receiving subscriber according to the invention.

In a further preferred embodiment of the method according to the invention, additional information is fed into the new data frame, which is segmented into one or more data packages, in the switching center. The new data packets contain, for example, a tone or an announcement.

Advantages of the invention are, above all, to be seen in the fact that a detour via the TDM coupling network is no longer necessary. To date, TDM-based decoding has been required to insert tones or announcements, then the TDM-based tones or announcements have to be inserted by replacing voicebytes with tonebytes, and then decoding based on AMR.

The data frame length is normally dependent on a desired codec mode and the useful information of a respective data frame. In this case, for example, it is also possible to replace pause frames, so-called SID frames, which are transmitted when the subscriber of the sending side does not speak, by one or more, possibly longer sound frames.

For feeding additional information into a connection, the method according to the invention can also be used if only one empty data frame arrives at the switching center. If, for example, a subscriber A does not transmit data but only empty data frames are sent, information can still be fed into the connection for a receiving subscriber B. The exchange station thereby detects the empty data frames and their respective beginning and then sends the information in one or more new data frames instead of the empty data frames to the receiving subscriber B.

If no data frames arrive in the unmodified connection, for example during a longer speech pause, a replacement of data frames is not possible. In this case, new data frames, for example with tones, are inserted in a grid provided for the connection.

On the other hand, it is also possible to remove data frames without replacing them. This is, for example, the case when you want to insert voice pauses into a connection.

Furthermore, the present invention includes providing a device for modifying a connection between a sending and a receiving subscriber in a data compression based communication system within a switching device wherein a data frame which is formatted according to a frame protocol and is formatted in the exchange is independent of the length of the data frame A new data frame formatted according to the frame protocol can be replaced, or the data frame arriving at the switching center can be removed, or that one or more new data frames formatted according to the frame protocol can be generated and inserted into the connection if the data frames arrive in the switching center .