Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-04-13
2001-10-23
Kincaid, Lester G. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S560000, C370S353000
Reexamination Certificate
active
06308063
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a mobile communication system which comprises a base station having a data transmission connection to a mobile services switching centre through a transcoder unit, in which system: the base station comprises means for transmitting and, correspondingly, receiving speech parameters over a radio connection from a mobile station located within its radio coverage area, the transcoder unit comprises means for decoding the speech parameters it has received from the base station to speech signals to be transmitted to the mobile services switching centre and, correspondingly, for encoding the speech signals it has received from the mobile services switching centre to speech parameters to be transmitted to the base station, and the base station and the transcoder unit communicate with one another over a circuit-switched data transmission connection, on which data transmission connection the speech parameters are transmitted by TRAU frames. Furthermore, the invention relates to a mobile communication system which comprises a base station having a data transmission connection to a mobile services switching centre through a transcoder unit, in which system: the base station comprises means for transmitting and, correspondingly, receiving speech parameters over a radio connection from a mobile station located within its radio coverage area, the transcoder unit comprises means for decoding the speech parameters it has received from the base station to speech signals to be transmitted to the mobile services switching centre and, correspondingly, for encoding the speech signals it has received from the mobile services switching centre to speech parameters to be transmitted to the base station, and the base station and the transcoder unit communicate with one another over a circuit-switched data transmission connection, on which data transmission connection the speech parameters are transmitted by TRAU frames. Furthermore, the invention also relates to a transcoder unit comprising a transcoder which includes: decoding means for decoding speech parameters the transcoder unit has received from a first data transmission connection and for forwarding them as speech signals over a second data transmission connection, and encoding means for encoding speech signals the transcoder unit has received from the second data transmission connection and forwarding them as speech parameters over the first data transmission connection. Furthermore, the invention also relates to a converter means in a mobile communication system.
The present invention particularly relates to a data transmission connection between a mobile services switching centre and a base station system of the GSM mobile communication system (Global System for Mobile Communications). However, it should be noted that although in the following, the invention will be described with reference to the GSM system in particular, the invention can also be applied to other mobile communication systems.
The GSM system includes a digital radio path, whereby a frequency spectrum required is dependent on a data transmission rate used on the radio path. The higher the data transmission rate used on the radio path, the wider the radio spectrum needed. Consequently, speech coding used in a fixed PSTN/ISDN network (Public Switched Telephone Network/Integrated Services Digital Network), transmitting 64 kbit/s of digital coded data for each traffic channel, is not suitable for use in the radio path of the GSM system. Instead of the speech coding used in the fixed network, the radio path of the GSM system therefore uses RPE-LTP speech coding (Regular Pulse Exitation—Long Term Prediction).
In order to transmit data associated with a speech channel from the base station system to the mobile services switching centre, a transcoder unit is arranged between the base station system and the mobile services switching centre in the GSM system. Speech coding and rate adaptation operations required are concentratedly arranged in a transcoder unit TRCU (Transcoder/Rate Adaptor Unit) in the GSM system. On grounds of the GSM specifications, the transcoder unit having a 64 kbit/s interface towards the mobile services switching centre and 8 or 16 kbit/s interfaces towards the base station system may be located in several alternative locations, the choice of the location being up to the system manufacturer.
DESCRIPTION OF RELATED ART
In prior art GSM mobile communication systems, information between the base station system and the transcoder unit is transmitted in TRAU frames which are transmitted between the base station system and the transcoder unit over circuit-switched 2 Mbit/s PCM connections (Pulse Code Modulation). A disadvantage associated with prior art mobile communication systems of the above-described type is that the TRAU frames utilized therein contain a large number of bits which are actually unnecessary for speech transmission. Consequently, it has been necessary to reserve more capacity for the telecommunication connection between the base station system and the transcoder unit than actually required by efficient speech transmission.
Another disadvantage associated with the transmission capacity of mobile communication systems of the above-described type is that the base station system reserves a channel from the PCM connection to be used by the mobile station for the transmission of the TRAU frame whether or not there is speech included in the TRAU frame. In other words, in connection with discontinuous transmission DTX, for example, this leads to a situation in which a major portion of the PCM channel is unnecessarily reserved for a particular mobile station, since there is no speech information to be transmitted.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate the above-described disadvantages and to provide a mobile communication system having more efficient data transmission between a base station system and a transcoder unit. This objective is achieved by the mobile communication system of the invention, which is characterized in that the data transmission connection between the base station and the transcoder unit is partly composed of a packet-switched data transmission connection, and that a converter means is arranged on the data transmission connection between the base station and the transcoder unit, the converter means comprising means for converting a TRAU frame received from said circuit-switched data transmission connection into a packet which is to be transmitted over the packet-switched connection, said conversion including the removal of bits which are included in the TRAU frame and not needed on the packet-switched connection.
An embodiment of the mobile communication system of the invention is characterized in that the data transmission connection between the base station and the transcoder unit is partly composed of a packet-switched data transmission connection, and that a converter means is arranged on the data transmission connection between the base station and the transcoder unit, the converter means comprising means for converting a packet received from said packet-switched data transmission connection into a TRAU frame to be transmitted over the circuit-switched connection, said conversion including at least the addition of synchronization bits to the TRAU frame.
The invention is based on the idea that the available data transmission capacity can be more efficiently utilized by partly substituting data transmission connections that are utilized in prior art mobile communication systems between base station systems and transcoder units by packet-switched connections. Consequently, bits that are included in TRAU frames on circuit-switched connections and not needed on the packet-switched connections can be removed when the TRAU frames are converted into packets to be used on the packet-switched data transmission connection. If required, the removed bits can be regenerated at the receiving end, in case there is a need for converting the packet received
Koistinen Tommi
Suvanen Jyri
Altera Law Group LLC
Kincaid Lester G.
Nokia Networks Oy
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