Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-12-27
2003-01-07
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432300, C455S435100, C370S401000
Reexamination Certificate
active
06505047
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a GPRS type of packet radio network and more specifically to reduction of signaling load therein as a mobile station changes routing areas.
A General Packet Radio Service (GPRS) is a new service in the GSM. It is one of the items that are being standardized in GSM (Global System for Mobile Communication) phase
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+ at the ETSI (European Telecommunication Standard Institute). The GPRS operational environment consists of one or more sub-network service areas that are interconnected by a GPRS backbone network. A sub-network comprises a number of packet data service nodes, which are herein called GPRS support nodes (or agents) and each one of which is connected to the GSM mobile network so that it can provide packet data service for mobile data terminals via several base stations, i.e. cells. An intermediate mobile network provides circuit-switched or packet-switched data transmission between a support node and the mobile data terminals. Different sub-networks, in turn, are connected to an external data network, for example to a Public Switched Packet Data Network (PSPDN). The GPRS service can thus be used for effecting packet data transmission between mobile data terminals and external data networks, with the GSM network functioning as an access network. One of the features of the GPRS service network is that it operates almost independently. of the GSM network. One of the requirements set for the GPRS service is that it must operate together with different types of external PSPDN networks, such as the Internet and X.25 networks. In other words, the GPRS service and the GSM network should be able to serve all users, irrespective of the type of data networks that they wish to be connected to via the GSM network. This means that the GSM network and GPRS service must support and process different network addressing methods and data packet formats. The data packet processing also comprises routing of packets in a packet radio network. In addition, users should be able to roam from their home GPRS network to a visited GPRS network.
FIG. 1A
illustrates a typical arrangement in a GPRS network. The architecture of GPRS networks is not as mature as that of the GSM networks. All GPRS terms should therefore be understood as being descriptive rather than limiting. A typical mobile station forming a mobile data terminal consists of a mobile station MS in a mobile network and of a portable computer PC connected to the data interface of the MS. The mobile station may be, for example Nokia 2110, manufactured by Nokia Mobile Phones Ltd., Finland. By means of a PCMCIA type Nokia Cellular Datacard, manufactured by Nokia Mobile Phones Ltd., the mobile station can be connected to any portable personal computer PC that has a PCMCIA card slot. The PCMCIA card thus provides the PC with an access point that supports the protocol of the telecommunication application used in the PC, such as the CCITT X.25 or Internet Protocol IP. Alternatively, the mobile station can directly provide an access point that supports the protocol used by the PC application. Further, a mobile station 3 and a PC 4 can be integrated to form a single unit, within which the application is provided with an access point that supports the protocol used by it. An example of such a mobile station with an integrated computer is a Nokia Communicator 9000, manufactured by Nokia Mobile Phones Ltd., Finland.
Network elements BSC and MSC are previously known from a typical GSM network. The arrangement of
FIG. 1A
comprises a separate Serving GPRS Support Node (SGSN). The support node controls certain operations of the packet radio service on the network side. The operations include logging on and off the system by the mobile stations MS, routing area updates by mobile stations MS, and data packet routing to correct destinations. In the present application, the term ‘data’ should be understood in the wide sense to refer to any information transmitted to/from a terminal in a digital telecommunication system. The information can comprise speech encoded into digital form, data communication between computers, telefax data, short segments of program code, etc. Information outside data transmission, such as subscriber data and related inquiries, routing area updates etc., is called signaling. The SGSN node can be located at a base station BTS, at a base station controller BSC or at a mobile switching center MSC, or it can be separate from all these elements. The interface between the SGSN node and the base station controller BSC is called a GB interface. An area managed by one base station controller BSC is called a Base Station Subsystem BSS.
The intermediate mobile network provides packet-switched data transmission between a support node and mobile data terminal equipment. Different sub-networks, in turn, are connected to an external data network, for example to a PSPDN, via a specific GPRS gateway support node GGSN. Packet data transmission between mobile data terminals and external data network functioning as an access network. Alternatively, the gateway node GGSN can be replaced with a router. In the following, the term ‘gateway node GGSN’ is also to be understood to refer to a structure in which the gateway has been replaced with a router.
In
FIG. 1A
the GPRS network connected to the GSM network comprises a number of serving GPRS support nodes SGSN and one gateway GPRS support node GGSN. The different support nodes SGSN and GGSN are interconnected via an intra-operator backbone network. It is to be understood that a GPRS network may comprise any number of support nodes SGSN and gateway nodes GGSN.
Each support node SGSN manages a packet data service in the area of one or more nodes in a cellular packet radio network. To achieve this, each support node SGSN is connected to a certain local part of the GSM system, typically to a mobile services switching center, but in some situations it may be preferable to connect it directly to a base station subsystem BSS, i.e. to a base station controller BSC or a base station BTS. A mobile station MS in a cell communicates with a base station BTS over a radio interface and further through a mobile network with the support node SGSN to the service area of which the cell belongs. In principle, the mobile network between the support node SGSN and the mobile station MS only transmits packets between these two. For this purpose, the mobile network can offer either a circuit-switched connection or packet-switched data packet transmission between a mobile station MS and a serving support node SGSN. An example of a circuit-switched connection between a mobile station MS and an agent is presented in FI 934115. An example of packet-switched data transmission between a mobile station MS and an agent is presented in FI940314. It should be noted, however, that a mobile network provides only a physical connection between a mobile station MS and a support node SGSN, and that its exact operation and structure are not relevant to the invention.
An intra-operator backbone network
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interconnecting an operator's SGSN and GGSN can be implemented by a local area network, for example. It should be noted that an operator's GPRS network can also be implemented without an intra-operator backbone network, by implementing all features in a single computer, for example, but this does not cause any changes in the call set-up principles according to the present invention.
A GPRS gateway node GGSN connects an operator's GPRS network to other operator's GPRS networks and to data networks, such as an inter-operator backbone network
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or an IP network. An Interworking Function IWF can be arranged between the gateway node GGSN and the other networks, but usually the GGSN is simultaneously the IWF. The inter-operator backbone network
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is one through which the gateway nodes GGSN of different operators can communicate with one another. The communication is needed to support GPRS roaming between the different GPRS networks.
The gateway node GGSN is also
Cong Le Thanh
D'Agosta Stephen M.
Nokia Telecommunications Oy
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