Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-08-07
2004-01-13
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S509000, C370S341000, C370S329000
Reexamination Certificate
active
06678527
ABSTRACT:
The invention generally relates to mobile communication networks and particularly to implementation of multiservice and multimedia calls in mobile communication systems.
In addition to conventional speech transmission, modern mobile communication systems offer various data transmission features to subscribers. The services of mobile communication systems are generally classified into tele-services and bearer services. A bearer service is a telecommunications service which provides signal transmission between the user interfaces and the network interfaces. An example of bearer services is a modem service. In the tele-service terminal services are also offered by the network. Important tele-services include speech, telefax and videotex services. The bearer services are usually subdivided into groups, such as asynchronous bearer services and synchronous bearer services, on the basis of a certain feature. In the case of the asynchronous bearer service the transmitting terminal and the receiving terminal are able to maintain their synchronization only for each single character to be transmitted. In the case of the synchronous bearer service the transmitting terminal and the receiving terminal are synchronized with each other for the whole duration of data transmission. Each such bearer service group comprises a number of bearer services, such as a transparent service and a non-transparent service. In the transparent service the data to be transmitted is unstructured and transmission errors are corrected only by means of channel coding. In the non-transparent service the data to be transmitted is structured into protocol data units (PDU) and transmission errors are corrected using automatic retransmission protocols (in addition to channel coding).
Existing mobile communication systems do not offer any special bearer services for multimedia calls or for simultaneous use of multiple data services. There is only one traffic channel available for a data call, the channel being either transparent (T) or non-transparent (NT). Depending on the required transmission rate a traffic channel may consist of one sub-channel (e.g. TDMA time slot) or several sub-channels (e.g. several TDMA time slots for high-speed data transmission, such as HSCSD in the GSM system). Any shared use of the traffic channel has to be implemented on the application layer, i.e. in the end user's applications. Time-critical multimedia calls, e.g. video phoning, have to use transparent circuit-switched bearer services because other data services cannot guarantee as small variation of the transmission delay as the video service requires. Too long a transmission delay causes visible interference in the video image at the receiving end. Applications which are not time-critical and require accurate transmission usually use non-transparent bearer services. An example of such an application is transfer of data files.
FIG. 2
illustrates a conventional video call which is connected through a GSM mobile communication system (Global System for Mobile Communication). The point-to-point transmission link between the mobile stations MS
1
and MS
2
consists of a first transparent traffic channel between the MS
1
and an interworking function IWF, which is located in a mobile services switching centre MSC, and of a second transparent traffic channel between the MS
2
and the IWF.
The European Telecommunications Standard Institute (ETSI) has begun to define an application programming interface and environment (Mobile API/Mobile Application Programming Interface MEXE/Mobile Execution Environment) which provide an opportunity e.g. for operators and parties independent of mobile station producers to develop applications and services for mobile users. This development work also comprises a multiplexed interface between the terminal equipment (TE) and the mobile station MS. This multiplexed interface comprises a multiplexed protocol and enables simultaneous use of several activities and/or services between the TE and the MS through one serial link. Examples of suitable services are data services and short message services. A TE which is to use simultaneously both the data service and the short message service activates multiplexing in which the data of both services are multiplexed into one data stream and supplied to the mobile station MS through the serial link. The MS carries out a similar multiplexing procedure in which the short message data is separated from the data service data and the data is transmitted to the corresponding units in the mobile station MS. After this the MS transmits the data service data, e.g. speed, telefax or data file, over the allocated transparent or non-transparent traffic channel in the usual manner. The short message data is transmitted outside the traffic channel, as is defined e.g. in the GSM system. Other activities, such as GPRS and USSD which use transmission outside the GSM traffic channel and e.g. information on the battery status, configuration information, phone books, etc., can also be transmitted over the TE-MS interface in the same way as short messages MSS. Thus this arrangement does not improve implementation of multimedia calls and multiservice calls in a mobile communication network, either.
As was stated above, the problem related to the present mobile communication systems is that they either provide a transparent or non-transparent traffic channel or a packet service (such as GPRS, General Packet Radio Service) for a multimedia call between two mobile stations or between a mobile station and a terminal or server in a fixed network. Packet radio services and the non-transparent traffic channel are not suitable for video phoning or other time-critical applications. On the application layer the transparent bearer service requires an error correction protocol which is usually not optimized for a radio connection. This means that a multiservice and/or multimedia channel has to always use a transparent bearer service and perform multiplexing and error correction on the application layer in the end users'terminals.
Another problem that may arise concerns rate adaptation between the fixed network traffic channel and the transparent mobile network traffic channel. The mobile network traffic channel and the fixed network traffic channel may have different bit rates, e.g. 28.8 kbits/s (2*14.4 kbits/s) on the GSM traffic channel and 32 kbits/s on the fixed network traffic channel, which is in accordance with the ITU-T H.221 recommendation (Telecommunication Standardisation Sector of International Telecommunication Union). The different rates of the traffic channels cause an unbearable situation on the transparent point-to-point traffic channel because the bit rate has to be constant over the whole point-to-point connection. The GSM recommendations teach to use a GSM channel with a higher rate and fill the excess capacity with a useless fill. On the GSM sub-connection it is possible to use for example a traffic channel of 38.4 kbits/s, of which 32 kbits/s are user data and 6.4. kbits/s fill data, and a fixed network sub-connection of 32 kbits/s on which 32 kbits/s of user data are transmitted. This prior art method, however, wastes valuable radio channel resources.
The objective of the invention is to enable multimedia and multiservice calls in mobile communication systems in a simple manner, utilizing the radio channel resources effectively.
This is achieved with a method of transmitting two or more different information flows simultaneously in one call in a mobile communication network, the method being characterized in that it comprises the steps of: assigning one mobile network traffic channel to the call; dividing the assigned traffic channel into at least two sub-channels, and transmitting at least one information flow in each virtual sub-channel.
The invention also relates to methods of making a multiservice or multimedia call according to claims 2 and 10, a mobile station according to claim 11 and mobile communication networks according to claims 15 and 19.
According to the basic
Nokia Networks Oy
Pillsbury & Winthrop LLP
Tran Congvan
Trost William
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