Telecommunications apparatus and methods

1. A terminal device for use in a wireless telecommunications system in Which downlink communications are made from a wireless telecommunications system using a radio interface that spans a system frequency bandwidth and the terminal device is configured to receive at least some communications from the wireless telecommunications system within a restricted subset of transmission resources selected from within the system frequency bandwidth and comprising a downlink channel having a channel bandwidth which is smaller than the system frequency bandwidth, and the wireless telecommunications system supports a Radio Resource Control (RRC) connected mode of operation in which the terminal device receives a type of user-plane data using the restricted subset of transmission resources and an RRC idle mode of operation in which terminal device does not receive the type of user-plane data, the terminal device comprising:

circuitry configured to

while the terminal device is in the RRC connected mode, receive from the wireless telecommunications system a paging message comprising an indication that an update to previously obtained system information is to be broadcast by the wireless telecommunications system, the indication indicating transmission resources to be used to broadcast the update to the previously obtained system information; and

responsive to the indication that the update to the previously obtained system information is to be broadcast by the wireless telecommunications system:

cause the terminal device to transition from the RRC connected mode to the RRC idle mode before seeking to acquire the update to the previously obtained system information, and

cause the terminal to seek and to acquire the update to the previously obtained system information broadcast by the wireless telecommunications system via the indicated transmission resources while the terminal device is in the RRC idle mode.

2. The terminal device of claim 1 , wherein

the terminal device is restricted from transitioning from the RRC idle mode back to the RRC connected mode until after the terminal device has successfully acquired the update to the previously obtained system information following the transition to the RRC mode.

3. The terminal device of claim 1 , wherein

the circuitry is configured to cause the terminal device to transition from the RRC connected mode to the RRC idle mode in response to receiving signaling from the wireless telecommunications system to indicate the terminal device should transition from the RRC connected mode to the RRC idle mode.

4. The terminal device of claim 3 , wherein

the indication that the update to the previously obtained system information is to be broadcast by the wireless telecommunications system is conveyed in association with the signaling from the wireless telecommunications system to indicate the terminal device should transition from the RRC connected mode to the RRC idle mode.

5. The terminal device of claim 3 , wherein

the signaling from the wireless telecommunications system to indicate the terminal device should transition from the RRC connected mode to the RRC idle mode further indicates the terminal device should not transition from the RRC idle mode back to the RRC connected mode until after the terminal device has successfully acquired system information following the transition to the RRC idle mode.

6. The terminal device of claim 3 , wherein

the signaling from the wireless telecommunications system to indicate the terminal device should transition from the RRC connected mode to the RRC idle mode comprises an RRC Connection Release message.

7. The terminal device of claim 1 , wherein

transitioning from the RRC connected mode to the RRC idle mode occurs at a time associated with when the wireless telecommunications system starts to broadcast the update to the previously obtained system information.

8. The terminal device of claim 1 , wherein

system information changes in the wireless telecommunications system are scheduled in accordance with a system information modification period, and

transitioning from the connected mode to the RRC idle mode occurs at a time associated with a boundary of a system information modification period following the indication that the update to the previously obtained system information is to be broadcast by the wireless telecommunications system.

9. The terminal device of claim 1 , wherein

the circuitry is configured to store a record to indicate that currently stored system information is no longer valid after it has received the indication of the update to the previously obtained system information and until it has acquired the update to the previously obtained system information.

10. The terminal device of claim 1 , wherein

the circuitry is configured to determine that the update to the previously obtained system information is not for a class of system information whose acquisition should not be delayed before transitioning from the RRC connected mode to the RRC idle mode to acquire the update to the previously obtained system information.

11. The terminal device of claim 1 , wherein

the circuitry is configured to cause the terminal device to transition from the RRC idle mode to the RRC connected mode in response to acquiring the update to the previously obtained system information.

12. The terminal device of claim 1 , wherein

the radio interface comprises a series of subframes and the physical resources corresponding to the restricted subset of transmission resources may be different for different subframes.

13. The terminal device of claim 1 , wherein

the terminal device is a machine type communication (MTC) terminal device.

14. Circuitry configured to be implemented in a terminal device for use in a wireless telecommunications system in which downlink communications are made from a wireless telecommunications system using a radio interface that spans a system frequency bandwidth and the terminal device is configured to receive at least some communications from the wireless telecommunications system within a restricted subset of transmission resources selected from within the system frequency bandwidth and comprising a downlink channel having a channel bandwidth which is smaller than the system frequency bandwidth, and the wireless telecommunications system supports a Radio Resource Control (RRC) connected mode of operation in which the terminal device receives a type of user-plane data using the restricted subset of transmission resources and an RRC idle mode of operation in which terminal device does not receive the type of user-plane data, the circuitry configured to:

while the terminal device is in the RRC connected mode, receive from the wireless telecommunications system a paging message comprising an indication that an update to previously obtained system information is to be broadcast by the wireless telecommunications system, the indication indicating transmission resources to be used to broadcast the update to the previously obtained system information; and

responsive to the indication that the update to the previously obtained system information is to be broadcast by the wireless telecommunications system:

cause the terminal device to transition from the RRC connected mode to the RRC idle mode before seeking to acquire the update to the previously obtained system information, and

cause the terminal to seek and to acquire the update to the previously obtained system information broadcast by the wireless telecommunications system via the indicated transmission resources while the terminal device is in the RRC idle mode.

15. A method of operating a terminal device in a wireless telecommunications system in which downlink communications are made by the wireless telecommunications system using a radio interface that spans a system frequency bandwidth and the terminal device is configured to receive at least some communications from the wireless telecommunications system within a restricted subset of transmission resources selected from within the system frequency bandwidth and comprising a downlink channel having a channel bandwidth which is smaller than the system frequency bandwidth, and wherein the wireless telecommunications system supports a Radio Resource Control (RRC) connected mode of operation in which the terminal device receives a type of user-plane data using the restricted subset of transmission resources and an RRC idle mode of operation in which terminal device does not receive the type of user-pane data, the method comprising:

receiving from the wireless telecommunications system a paging message comprising an indication that update to the previously obtained system information is to be broadcast by the wireless telecommunications system, the indication indicating transmission resources used to broadcast the update to the previously obtained system information

wherein the paging message is received while the terminal device is in the RRC connected mode;

responsive to receiving the indication that update to the previously obtained system information is to be broadcast by the wireless telecommunications system:

transitioning from the RRC connected mode to the RRC idle mode before seeking to acquire the update to the previously obtained system information; and

seeking to acquire and acquiring the update to the previously obtained system information broadcast by the wireless telecommunications system while the terminal device is in the RRC idle mode.