Method for activating packet data protocol context for roaming subscriber, network equipment and telecommunication system for utilizing same

1. A method of activating a packet data protocol context for a roaming terminal in a telecommunication system comprising a home network, a gateway support node connected to an external packet network, said node being used in the home network, at least one roaming terminal and a visited network, in which system there is no signalling interface between the home network and the visited network to support mobility management, the method comprising:

storing at least a network identifier of an access point served by said gateway support node in the visited network for the at least one roaming terminal,

defining an address of said gateway support node in the visited network based on said network identifier and a subscriber identifier transmitted by the at least one roaming terminal, in response to the at least one roaming terminal requesting packet data protocol context activation,

transmitting a request for packet data protocol context activation from the visited network to said gateway support node based on said gateway support node address, and

finishing the activation of the packet data protocol context between the at least one roaming terminal and said gateway support node.

2. A method as claimed in claim 1 , wherein

said gateway support node is GGSN and said gateway support node address is defined based on an access point name APN.

3. A method as claimed in claim 1 , wherein the gateway support node address obtained based on the network identifier and the subscriber identifier transmitted by the at least one roaming terminal is a domain name, and

converting the domain name to an IP address of said gateway support node.

4. A method as claimed in claim 1 , wherein

at least said network identifier is stored subscriber-specifically or group-specifically.

5. A method as claimed in claim 1 , wherein an access point operator identifier is defined based on the subscriber identifier, and

said gateway support node address is defined based on the stored network identifier and the operator identifier.

6. A method as claimed in claim 1 , wherein an access point operator identifier is also stored in the visited network for roaming terminals, and

said gateway support node address is defined based on the stored operator identifier and network identifier.

7. A method as claimed in claim 1 , wherein

information on a desired access point served by the gateway support node is transmitted from the terminal in connection with the request for packet data protocol context activation,

checking whether a network identifier included in said information transmitted by the terminal is stored in the visited network, and

the request to said desired gateway support node is transmitted in order to activate the packet data protocol context, in response to the network identifier of said desired access point being stored in the visited network.

8. A method as claimed in claim 1 , wherein the home network and the visited network are TETRA networks and said subscriber identifier is an ITSI identifier.

9. A packet-switched telecommunication system comprising

a home network and at least one visited network, there being no signalling interface therebetween to support mobility management,

in the home network, a gateway support node connected to an external packet network, said node being used for at least one terminal, wherein the at least one visited network is configured to define an address of said gateway support node based on a pre-stored network identifier of an access point served by said gateway support node and a subscriber identifier transmitted by a roaming terminal, in response to the roaming terminal requesting packet data protocol context activation, and

the visited network is configured to transmit the request for packet data protocol context activation to said gateway support node based on said gateway support node address.

10. A telecommunication system as claimed in claim 9 , wherein said gateway support node is a General Packet Radio Service GPRS gateway support node GGSN and said gateway support node address is defined based on an APN.

11. A telecommunication system as claimed in claim 9 , wherein

the visited network is configured to define an access point operator identifier based on the subscriber identifier transmitted by a terminal, and

the visited network is configured to define the address of said gateway support node based on the network identifier and the operator identifier.

12. A telecommunication system as claimed in claim 9 , wherein

the visited network is configured to define the address of said gateway support node based on a pre-stored operator identifier and said network identifier.

13. A telecommunication system as claimed in claim 9 , wherein

the visited network is configured to check whether a network identifier of a desired access point served by the gateway support node and transmitted by a terminal is stored in the visited network, and

the visited network is configured to transmit the request to said desired gateway support node to activate the packet data protocol context, in response to a network identifier of said desired access point being stored in the visited network.

14. A network equipment for a telecommunication system comprising a home network, a gateway support node connected to an external packet network, said node being used in the home network, at least one roaming terminal and a visited network, in which system there is no signalling interface between the home network and the visited network to support mobility management, wherein

the network equipment is configured to store a network identifier of an access point served by said gateway support node for the at least one roaming terminal,

the network equipment is configured to define an address of said gateway support node based on said network identifier and a subscriber identifier transmitted by the at least one roaming terminal, in response to the at least one roaming terminal requesting for packet data protocol context activation, and

the network equipment is configured to transmit a request for packet data protocol context activation to said gateway support node based on the gateway support node address.

15. A telecommunication system as claimed in claim 9 , wherein the home network and the visited network are TETRA networks and the subscriber identifier is an Individual TETRA Subscriber Identity ITSI.

16. The network equipment as claimed in claim 14 , wherein the home network and the visited network are TETRA networks and the subscriber identifier is an Individual TETRA Subscriber Identity ITSI.