Communications terminals, infrastructure equipment and methods, for UE:s acting as relays

1. A communications terminal forming part of a mobile communications network comprising one or more infrastructure equipment and one or more other communications terminals, the communications terminal comprising

a transmitter configured to transmit signals via a wireless access interface to the infrastructure equipment and to transmit signals via the wireless access interface to one or more of the other communications terminals in accordance with a device-to-device communications protocol,

a receiver configured to receive signals via the wireless access interface from the infrastructure equipment and to receive signals via the wireless access interface from one or more of the other communications terminals in accordance with a device-to-device communications protocol, and

circuitry comprising a controller configured to control the transmitter and the receiver to transmit and to receive data via the wireless access interface when in a connected mode and to select one of the one or more infrastructure equipment from which to receive paging messages for down-link communications when in an idle mode, wherein the controller is configured

to measure, when in the idle mode, signals received by the receiver from any of the one or more infrastructure equipment, and in accordance with predetermined conditions,

to enter the connected mode,

to discover that one or more of the other communications terminals can act as a relay node to transmit signals to one of the one or more infrastructure equipment which represent data having been transmitted by the transmitter and received by the relay node and to receive signals from the relay node which represent data transmitted by the infrastructure equipment for the communications terminal,

to select one of the discovered communications terminals to act as the relay node for the communications terminal,

to establish a connection in the connected mode with the infrastructure equipment via the relay node to register with the mobile communications network that paging messages for the communications terminal should be transmitted to the relay node, for transmission to the communications terminal, and

to switch from the connected mode to a DRX-connected mode that uses an extended discontinuous reception (DRX) communications protocol and that is distinct from the connected mode and operate in accordance with the DRX communications protocol, wherein, in the DRX-connected mode, the controller controls the receiver to monitor only the one of the one or more communications terminals acting as the relay node.

2. The communications terminal as claimed in claim 1 , wherein the receiver being configured in combination with the controller to operate in accordance with the DRX communications protocol comprises the controller being configured

to enter the DRX-connected mode in which the controller controls the receiver to only monitor the communications terminal acting as the relay node to determine whether the receiver can no longer receive the paging messages from the communications terminal acting as the relay node, wherein

when in the DRX-connected mode, the controller is configured to control the receiver to be configured receive signals for a predetermined portion of a predetermined period, wherein the predetermined period is determined in accordance with a DRX cycle.

3. The communications terminal as claimed in claim 2 , wherein the predetermined period of the DRX cycle is configured to be set by the controller in combination with one of the one or more infrastructure equipment.

4. The communications terminal as claimed in claim 2 , wherein the predetermined period of the DRX cycle is configured to be changed by one of the one or more infrastructure equipment, and the changed predetermined period of the DRX cycle is received by the receiver from the infrastructure equipment via the communications terminal acting as a relay node.

5. The communications terminal as claimed in claim 2 , wherein the communications terminal being configured to enter the DRX-connected mode is automatic.

6. The communications terminal as claimed in claim 2 , wherein the communications terminal being configured to enter the DRX-connected mode comprises the controller being configured

to detect that the connection to the communications terminal acting as a relay node has been established,

to set a timer,

to detect that the transmitter has not transmitted signals to the communications terminal acting as a relay node and the receiver has not received signals from the communications terminal acting as a relay node after the predetermined time at the timer is set to expire, and consequently,

to enter the DRX-connected mode.

7. The communications terminal as claimed in claim 6 , wherein the timer is configured to expire after a predetermined time.

8. The communications terminal as claimed in claim 6 , wherein the timer is configured to expire after a time configured by the infrastructure equipment.

9. The communications terminal as claimed in claim 2 , wherein the controller is configured

to detect that the receiver can no longer receive the paging messages from the communications terminal acting as a relay node, and consequently

to search for a second communications terminal to act as a relay node or to search for an infrastructure equipment with which the transmitter and receiver can transmit and receive signals.

10. The communications terminal as claimed in claim 1 , wherein the predetermined conditions comprise a relative quality of the signals being below a predetermined threshold.

11. The communications terminal as claimed in claim 1 , wherein the predetermined conditions comprise a relative quality of the signals being below a dynamic threshold, wherein the dynamic threshold is dynamically configured by the infrastructure equipment.

12. The communications terminal as claimed in claim 1 , wherein the discovering that one or more of the other communications terminals can act as a relay node comprises

the communications terminal transmitting a discovery signal, and consequently

the communications terminal receiving an acknowledgement signal from the one or more of the other communications terminals.

13. The communications terminal as claimed in claim 1 , wherein the discovering that one or more of the other communications terminals can act as a relay node comprises

the communications terminal receiving a discovery signal transmitted by the one or more of the other communications terminals, and consequently

the communications terminal transmitting an acknowledgement signal to the one or more of the other communications terminals.

14. The communications terminal as claimed in claim 1 , wherein the communications terminal is configured

to detect that the receiver can receive paging messages from any of the one or more infrastructure equipment,

to discover that one or more of the other communications terminals can act as a relay node,

to select one of the discovered communications terminals to act as a relay node for the communications terminal, and

to establish a connection with the infrastructure equipment via the relay node to register with the mobile communications network that paging messages for the communications terminal should be transmitted to the relay node, for transmission to the communications terminal.

15. The communications terminal as claimed in claim 1 , wherein the selecting of one of the discovered communications terminals to act as a relay node for the communications terminal is controller by the infrastructure equipment.

16. A method of operating a communications terminal forming part of a mobile communications network comprising one or more infrastructure equipment and one or more other communications terminals, the method comprising

transmitting and receiving data via a wireless access interface when in a connected mode,

selecting one of the one or more other communications terminals to act as a relay node for the communications terminal,

establishing a connection in the connected mode with the infrastructure equipment via the relay node to register with the mobile communications network that paging messages for the communications terminal should be transmitted to the relay node, for transmission to the communications terminal, and upon establishing the connection with the infrastructure equipment via the relay node,

switching from the connected mode to a DRX-connected mode that uses an extended discontinuous reception (DRX) communications protocol and that is distinct from the connected mode and operating in accordance with the DRX communications protocol, and

in the DRX-connected mode, monitoring only the one of the one or more communications terminals acting as the relay node.

17. Circuitry for a communications terminal forming part of a mobile communications network comprising one or more infrastructure equipment and one or more other communications terminals, the communications terminal comprising

a transmitter configured to transmit signals via a wireless access interface to the infrastructure equipment and to transmit signals via the wireless access interface to one or more of the other communications terminals in accordance with a device-to-device communications protocol, and

a receiver configured to receive signals via the wireless access interface from the infrastructure equipment and to receive signals via the wireless access interface from one or more of the other communications terminals in accordance with a device-to-device communications protocol, and

a controller configured to control the transmitter and the receiver to transmit and to receive data via the wireless access interface when in a connected mode, wherein the controller is configured

to select one of the one or more other communications terminals to act as a relay node for the communications terminal,

to establish a connection in the connected mode with the infrastructure equipment via the relay node to register with the mobile communications network that paging messages for the communications terminal should be transmitted to the relay node, for transmission to the communications terminal, and upon establishing the connection with the infrastructure equipment via the relay node, and

to switch from the connected mode to a DRX-connected mode that uses an extended discontinuous reception (DRX) communications protocol and that is distinct from the connected mode and operate in accordance with the DRX communications protocol, wherein, in the DRX-connected mode, the controller controls the receiver to monitor only the one of the one or more communications terminals acting as the relay node.