System and method for restricting access to a mobile communications network

1. A system for restricting access to a mobile communications network by mobile communication devices within a restricted area, the system comprising:

a plurality of transmitters each configured to transmit a beacon signal for reception by the mobile communication devices within the restricted area; and

an access control entity, communicable with a mobile communication device via a base station,

wherein:

the access control entity is configured to decide, based on measurement data from the mobile communication device indicative of reception by the mobile communications device of the beacon signals transmitted by the plurality of transmitters, whether or not to provide the mobile communication device with access to a service of the mobile communications network;

each transmitter is a simplex communication device arranged so that the beacon signals emulate signals emitted by base stations of the mobile communications network to indicate the presence of those base stations; and

the access control entity is arranged to vary a time for which a dedicated channel with a mobile communications device is held open, whereby enabling a varying number of measurement reports to be received from the mobile communications device.

2. A system according to claim 1 , wherein each of the plurality of transmitters transmits the beacon signal at a power of about 0 dBm.

3. A system according to claim 1 , wherein each of the plurality of transmitters comprises a directional antenna.

4. A system according to claim 1 , wherein the access control entity is arranged to deny access to the service of the mobile communications network under one or more conditions, the one or more conditions including if the measurement data indicates that at least one detected beacon signal satisfies a measurement condition.

5. A system according to claim 1 , wherein the access control entity is arranged to allow access to the service of the mobile communications network under one or more conditions, the one or more conditions including if the measurement data indicates that at least one detected beacon signal satisfies a measurement condition.

6. A system according to claim 1 , wherein the access control entity is provided in the mobile communications network.

7. A system according to claim 6 , wherein the access control entity is implemented by code in a radio access network, a core network, or both the radio access network and the core network of the mobile communications network.

8. A system according to claim 1 , wherein:

the mobile communications network is a first mobile communications network;

the access control entity is arranged to control access to the service provided by the first mobile communication network, and

the access control entity is provided in a second mobile communication network separate from the first mobile communication network.

9. A system according to claim 1 , wherein said service is a voice call, an SMS message or a data session.

10. A system according to claim 1 , wherein the measurement data is provided in a measurement report in accordance with a wireless communications standard.

11. A system according to claim 10 , wherein the wireless communications standard is the GSM standard.

12. A method of restricting access to a mobile communications network by mobile communication devices within a restricted area, the method comprising:

providing a plurality of transmitters each configured to transmit a beacon signal for reception by the mobile communication devices within the restricted area;

varying a time for which a dedicated channel with a mobile communications device is held open, whereby enabling a varying number of measurement reports to be received from the mobile communications device;

receiving a measurement report from the mobile communications device, the measurement report conveying measurement data indicative of reception by the mobile communications device of the beacon signals transmitted by the plurality of transmitters; and

deciding, based on the measurement data from the mobile communication device, whether or not to provide the mobile communication device with access to a service of the mobile communications network,

wherein:

the or each transmitter is a simplex communication device arranged so that the beacon signals emulate signals emitted by base stations of the mobile communications network to indicate the presence of those base stations.

13. A method according to claim 12 , wherein the transmitters are disposed within the restricted area.

14. A method according to claim 12 , wherein the transmitters are disposed outside of the restricted area with directional antennas that direct the beacon signal into the restricted area.

15. A method according to claim 12 , wherein the restricted area comprises an immigration hall of an airport.