Cell reselection using not updated mobility information

1. A communications device for communicating via a mobile communications network, the communications device comprising:

a transmitter configured to transmit signals to one or more infrastructure equipment of the mobile communications network via a wireless access interface provided by the one or more infrastructure equipment when in a connected mode;

a receiver configured to receive signals from the one or more infrastructure equipment via the wireless access interface; and

a controller configured to control the receiver to acquire mobility information, the mobility information providing an indication of communications parameters relating to the wireless access interface provided by the one or more infrastructure equipment for receiving signals at the receiver, and the controller is further configured

to store the mobility information as the latest mobility information in a data store,

to detect that the communications device cannot receive updated mobility information broadcast by a first of the one or more infrastructure equipment or any of the other one or more infrastructure equipment when a location of the communications device is changed from being completely out of coverage into a coverage enhanced region of the first of the one or more infrastructure equipment, and

when in an idle mode and the controller detects that the communication device cannot receive the updated mobility information based on the changed location

to measure signals received from at least one of the one or more infrastructure equipment using the latest mobility information stored in the data store, and

to perform a cell reselection process based on the measured signals in order to reselect one of the one or more infrastructure equipment, using the latest mobility information stored in the data store, only when the communication device previously received mobility information from a third of the one or more infrastructure equipment that is a neighbor of the first of the one or more infrastructure equipment.

2. The communications device as claimed in claim 1 , wherein the controller is configured with the receiver

to detect that the communications device cannot receive updated mobility information by determining that the communications device has entered a coverage extension condition in which data is communicated with the communications device by repeated transmission of signals representing the data to extend a radio coverage provided by one or more of the one or more infrastructure equipment.

3. The communications device as claimed in claim 1 , wherein the controller is configured in combination with the receiver

to detect that system information received from a infrastructure equipment relating the wireless access interface has become invalid,

to determine that the communications device is in a coverage extension mode for signals received from the first infrastructure equipment, for which updated mobility information cannot be received as part of the system information, and

to reuse the latest mobility information received from the first infrastructure equipment when in the coverage extension mode.

4. The communications device as claimed in claim 1 , wherein the controller is configured in combination with the receiver

to detect that system information received from a first of the one or more infrastructure equipment relating the wireless access interface has become invalid,

to determine that the communications device is in a coverage extension mode for signals received from a second infrastructure equipment of the one or more infrastructure equipment, for which updated mobility information cannot be received as part of the system information, and

to reuse the latest mobility information received from the first infrastructure equipment when in the coverage extension mode.

5. The communications device as claimed in claim 4 , wherein the controller is configured

to detect that the communications device can receive signals from the second infrastructure equipment in a coverage extension mode in which updated mobility information cannot be received by the communications device from the second infrastructure equipment,

to form a list of the one or more infrastructure equipment as candidates for reselection using the latest mobility information stored in the data store, the list being formed to include an indication the second infrastructure equipment as a current cell and the first infrastructure equipment as a neighbouring cell.

6. The communications device as claimed in claim 1 , wherein the controller is configured to control the receiver to receive system information provided in system information block transmitted repeatedly to extend a radio coverage of a cell served by the one or more infrastructure equipment, wherein the mobility information is not transmitted repeatedly with the system information so that the receiver cannot receive the updated mobility information when in a coverage extension mode.

7. The communications device as claimed in claim 1 , wherein the controller is configured with the transmitter and the receiver

to request from the first infrastructure equipment the updated mobility information,

to receive in response to the request the updated mobility information, and

to store the received updated mobility information in the data store as the latest mobility information.

8. The communications device as claimed in claim 1 , wherein the controller is configured with the receiver

to scan for signals transmitted by the one or more infrastructure equipment, to detect a plurality of the one or more infrastructure equipment as candidates for reselection,

to form updated mobility information from the detected candidate infrastructure equipment,

to store the updated mobility information as the latest mobility information in the data store, and

to use the updated mobility information for measuring the signals received from the candidate infrastructure equipment using the latest mobility information stored in the data store, and performing the cell reselection process based on the measured signals.

9. The communications device as claimed in claim 8 , wherein the controller is configured

to detect that the receiver cannot receive signals from one of more of the one or more infrastructure equipment identified by the latest mobility information stored in the data store, and if the receiver cannot receive the signals from the identified infrastructure equipment,

to scan for the signals transmitted by the one or more infrastructure equipment, to detect the plurality of the one or more infrastructure equipment as candidates for reselection.

10. The communications device as claimed in claim 1 , wherein the controller is configured with the receiver to acquire the latest mobility information by

scanning for signals transmitted by the one or more infrastructure equipment,

detecting one or more of the one or more infrastructure equipment as candidates for reselection using predetermined signal detection thresholds, and

forming the latest mobility information from the one or more detected candidate infrastructure equipment.

11. The communications device as claimed in claim 1 , wherein the controller is configured with the receiver to acquire the latest mobility information by

receiving the latest mobility information which has been broadcast by a first of the one or more infrastructure equipment.

12. A method of controlling a communications device for communicating via a mobile communications network, the method comprising:

transmitting signals from the communications device to one or more infrastructure equipment of the mobile communications network via a wireless access interface provided by the one or more infrastructure equipment when in a connected mode; and

receiving signals from the one or more infrastructure equipment via the wireless access interface, wherein the receiving comprises

acquiring mobility information, the mobility information providing an indication of communications parameters relating to the wireless access interface provided by the one or more infrastructure equipment for receiving signals at the receiver,

storing the mobility information as the latest mobility information in a data store,

detecting that the communications device cannot receive updated mobility information broadcast by a first of the one or more infrastructure equipment or any of the other one or more infrastructure equipment when a location of the communications device is changed from being completely out of coverage into a coverage enhanced region of the first of the one or more infrastructure equipment, and

when in an idle mode and the detecting detects that the communication device cannot receive the updated mobility information based on the changed location

measuring signals received from at least one of the one or more infrastructure equipment using the latest mobility information stored in the data store, and

performing a cell reselection process based on the measured signals in order to reselect one of the one or more infrastructure equipment, using the latest mobility information stored in the data store, only when the communication device previously received mobility information from a third of the one or more infrastructure equipment that is a neighbor of the first of the one or more infrastructure equipment.

13. The method as claimed in claim 12 , wherein the detecting that the communications device cannot receive updated mobility information comprises

determining that the communications device has entered a coverage extension condition in which data is communicated with the communications device by repeated transmission of signals representing the data to extend a radio coverage provided by one or more of the one or more infrastructure equipment.

14. The method as claimed in claim 12 , the method comprising

detecting that system information received from the one or more infrastructure equipment relating the wireless access interface has become invalid,

determining that the communications device is in a coverage extension mode for signals received from the first infrastructure equipment, for which updated mobility information cannot be received as part of the system information, and

reusing the latest mobility information received from the first infrastructure equipment when in the coverage extension mode.

15. The method as claimed in claim 14 , the method comprising

detecting that system information received from the first of the one or more infrastructure equipment relating the wireless access interface has become invalid,

determining that the communications device is in a coverage extension mode for signals received from a second infrastructure equipment of the one or more infrastructure equipment, for which updated mobility information cannot be received as part of the system information, and

reusing the latest mobility information received from the first infrastructure equipment when in the coverage extension mode.

16. The method as claimed in claim 15 , wherein the detecting that the communications device cannot receive updated mobility information broadcast by the first of the one or more infrastructure equipment or any of the other one or more infrastructure equipment comprises

detecting that the communications device can receive signals from the second infrastructure equipment in a coverage extension mode in which updated mobility information cannot be received by the communications device from the second infrastructure equipment, and the performing the reselection process based on the measured signals comprises

forming a list of the one or more infrastructure equipment as candidates for reselection using the latest mobility information stored in the data store, the list being formed to include an indication the second infrastructure equipment as a current cell and the first infrastructure equipment as a neighbouring cell.

17. The method as claimed in claim 13 , comprising

receiving system information provided in a system information block transmitted repeatedly to extend a radio coverage of a cell served by the one or more infrastructure equipment, wherein the mobility information is not transmitted repeatedly with the system information so that the updated mobility information cannot be received when in a coverage extension mode.

18. The method as claimed in claim 12 , the method comprising

determining that the communications device has entered the coverage extension mode by comparing a strength of signals received with a predetermined threshold.

19. The method as claimed in claim 12 , the method comprising

requesting from the first infrastructure equipment the mobility information,

receiving in response to the request the mobility information, and

storing the received mobility information in the data store as the latest mobility information.

20. The method as claimed in claim 12 , wherein the acquiring the latest mobility information comprises

scanning for signals transmitted by the one or more infrastructure equipment,

detecting a plurality of the one or more infrastructure equipment as candidates for reselection using predetermined signal detection thresholds, and

forming the latest mobility information from the one or more detected candidate infrastructure equipment.

21. The method as claimed in claim 12 , wherein the acquiring the latest mobility information comprises

receiving the latest mobility information which has been broadcast by a first of the one or more infrastructure equipment.

22. A communications device for communicating via a mobile communications network, the communications device comprising

a controller configured to control a receiver

to acquire mobility information, the mobility information providing an indication of communications parameters relating to a wireless access interface provided by the one or more infrastructure equipment for receiving signals at the receiver, and the controller is configured

to store the mobility information as the latest mobility information in a data store, and

when in an idle mode, to measure signals received from at least one of the one or more infrastructure equipment using the latest mobility information stored in the data store, in response to the receiver being unable to detect mobility information broadcast by one of the one or more infrastructure equipment when a location of the communications device is changed from being completely out of coverage into a coverage enhanced region of the first of the one or more infrastructure equipment, and

to perform a cell reselection process to reselect one of the one or more infrastructure equipment, using the latest mobility information stored in the data store, only when the communication device previously received mobility information from a third of the one or more infrastructure equipment that is a neighbor of the first of the one or more infrastructure equipment.