Network elements, wireless communication system and methods therefor
A radio access network element ( 101 ) obtains a permanent subscriber identity (IMSI) of a User Equipment ( 103 ) in an LTE wireless communication system ( 100 ) by sending a “fake” service reject message to a User Equipment which has attempted to attach to a cell ( 102 ) in a request for services message which includes its S-TMSI. The reject message may include a cause code which results in the UE attempting to attach again, this time using its IMSI. The fake service reject message may be generated in a an eNode B serving one or more macrocells or a evolved Home Node B serving a small cell.
1. A method for determining a permanent subscriber identity of a wireless communication unit located within a cell of a wireless communication system comprising a radio access network and a core network, the method including, at a network element:
serving said cell in the radio access network,
receiving a request for services from a wireless communication unit wherein the request for services includes a temporary identity of the wireless communication unit,
in response to receiving said request for services, at the network element, generating and transmitting to the wireless communication unit a response message wherein the response message prompts the wireless communication unit to make a second request for services including its permanent subscriber identity, and
receiving said second request for services including the permanent identity of the wireless communication unit.
2. The method of claim 1 including storing the permanent subscriber identity received from the wireless communication unit with the second request for services.
3. The method of claim 1 wherein the response message includes a cause code.
4. The method of claim 3 wherein the cause code is be chosen such that it indicates to the wireless communication unit that the temporary identity of the wireless communication unit could not be recognized by the core network.
5. The method of claim 1 wherein the temporary identity comprises an S-TMSI and the response message comprises a non-authenticated EMM (Evolved Packet System Mobility Management) Service Reject with Cause: “UE identity cannot be derived by the network” in response to a Service Request following an RRC Connection Request from the wireless communication unit.
6. The method of claim 1 comprising, at the network element, sending to the core network a request for services in respect of the wireless communication unit including the permanent subscriber identity received from the wireless communication unit, receiving from the core network a new temporary subscriber identity allocated to the wireless communication unit and storing said new temporary subscriber identity.
7. The method of claim 6 including, at the network element, determining if a temporary subscriber identity received with a request for services from a wireless communication unit is the same as a stored new temporary subscriber identity, and if so, sending a request for services in respect of the wireless communication unit to the core network without generating and transmitting to the wireless communication unit the response message.
8. A radio access network element for determining a permanent subscriber identity of a wireless communication unit located in a cell of wireless communication system comprising a radio access network and a core network, the radio access network element being arranged to serve said cell and comprising:
a receiver arranged to receive a request for services from a wireless communication unit wherein the request for services includes a temporary identity of the wireless communication unit,
a signal processor arranged, in response to receipt of said request for services by the receiver, to generate a response message wherein the response message prompts the wireless communication unit to make a second request for services including its permanent subscriber identity, and
a transmitter arranged to transmit said generated response message to the wireless communication unit and wherein the receiver is further arranged to receive the second request for services including the permanent subscriber identity of the wireless communication unit.
9. The radio access network element of claim 8 comprising a memory for storing the permanent subscriber identity received from the wireless communication unit with the second request for services.
10. The radio access network element of claim 8 wherein the signal processor is arranged to include a cause code in the generated response message.
11. The radio access network element of claim 8 arranged to send to the core network a request for services in respect of the wireless communication unit including the permanent subscriber identity received from the wireless communication unit and to receive from the core network a new temporary subscriber identity allocated to the wireless communication unit, and wherein the radio access network element includes a memory for storing said new temporary subscriber identity.
12. The radio access network element of claim 11 arranged to determine if a temporary subscriber identity received with a request for services from a wireless communication unit is the same as a stored new temporary subscriber identity, and if so, to generate and transmit a request for services in respect of the wireless communication unit to the core network without generating the response message.
13. The radio access network element of claim 8 wherein the signal processor is implemented in an integrated circuit.
14. A long term evolution, LTE, wireless communication system comprising:
a radio access network;
a core network; and
a radio access network element for determining a permanent subscriber identity of a wireless communication unit located in an LTE cell, the radio access network element being configured to serve said cell and comprising:
a receiver arranged to receive a request for services from a wireless communication unit wherein the request for services includes a temporary identity of the wireless communication unit,
a signal processor arranged, in response to receipt of said request for services by the receiver, to generate a response message wherein the response message prompts the wireless communication unit to make a second request for services including its permanent subscriber identity, and
a transmitter arranged to transmit said generated response message to the wireless communication unit and wherein the receiver is further arranged to receive the second request for services including the permanent subscriber identity of the wireless communication unit.