User equipment, communication system, and method of controlling a user equipment

1. A user equipment, comprising:

a radio interface; and

a processing device coupled to the radio interface to control the radio interface, the processing device being operative to control a mode switching between a first mode in which the user equipment is configured for communication with a first cellular network and a second mode in which the user equipment is configured for communication with a second cellular network, wherein the processing device is operative to effect the mode switching between the first mode and the second mode in response to a trigger event,

the user equipment having a first power consumption when operating in the first mode and a second power consumption when operating in the second mode, the second power consumption being different from the first power consumption, and

wherein the trigger event relates to at least one of a data payload size, a transmission interval, a buffer status, payload data context, or a required coverage.

2. The user equipment of claim 1 ,

wherein the user equipment is configured for communication with a Cellular Internet of Things, CIoT, network when operating in the second mode.

3. The user equipment of claim 2 ,

wherein the first cellular network has a first core network and the second cellular network has a second core network different from the first core network.

4. The user equipment of claim 1 , wherein

the user equipment when operating in the first mode has to exchange a first number of messages with the first cellular network before user data can be sent to the first cellular network or can be received from the first cellular network, and

the user equipment when operating in the second mode has to exchange a second number of messages with the second cellular network before user data can be sent to the second cellular network or can be received from the second cellular network, the second number of messages being less than the first number of messages.

5. The user equipment of claim 1 ,

wherein the user equipment is operative to transmit and/or receive user data in a control plane signalling message when operating in the second mode.

6. The user equipment of claim 1 ,

wherein the user equipment is operative to perform the mode switching in dependence on

an amount of user data that is to be transmitted or received, and/or

a time interval between successive user data transmissions.

7. The user equipment of claim 6 ,

wherein the user equipment is operative to switch to the second mode if the amount of user data is less than a data amount threshold and if the time interval exceeds a time interval threshold.

8. The user equipment of claim 6 ,

wherein the user equipment is operative to transmit a buffer status report, BSR, to indicate an amount of user data that is to be transmitted.

9. The user equipment of claim 1 ,

wherein the processing device is operative to control the user equipment to effect the mode switching from the second mode to the first mode in response to a paging signal from the second cellular network.

10. The user equipment of claim 9 ,

wherein the processing device is operative to control the user equipment to attach to the first cellular network in response to the paging signal received from the second cellular network.

11. The user equipment of claim 9 ,

wherein the paging signal includes an indicator for an amount of user data that is to be transmitted in a downlink transmission.

12. The user equipment of claim 1 ,

wherein the processing device is operative to cause storage of operating parameters of a mode in which the user equipment operated prior to a first mode switching and to reuse the operating parameters when the user equipment returns to the mode in a subsequent second mode switching.

13. The user equipment of claim 12 ,

wherein the processing device is operative to process system information transmitted or broadcast by a base station to determine whether the operating parameters are to be reused.

14. The user equipment of claim 1 ,

wherein the user equipment is configured such that the mode switching is performed as a function of a mobility of the user equipment.

15. A communication system, comprising:

a base station coupled to a first core network and to a second core network; and

the user equipment of claim 1 .

16. The communication system of claim 15 ,

wherein the first core network comprises a first core network node and the second core network comprises a second core network node interfaced with the first core network node,

wherein

the first core network node is operative to transfer to the second core network node user equipment context information stored in the first core network node, and

the second core network node is operative to transfer to the first core network node user equipment context information stored in the second core network node.

17. The communication system of claim 15 ,

wherein the second core network is a Cellular Internet of Things, CIoT, core network.

18. A method of controlling operation of a user equipment, wherein the user equipment comprises a radio interface and is operative to attach to a first cellular network and to attach to a second cellular network ( 40 ) different from the first cellular network, wherein the method comprises:

controlling the user equipment such that it operates in a first mode in which the user equipment is operative to attach to the first cellular network, the user equipment having a first power consumption when operating in the first mode;

controlling a mode switching between the first mode and a second mode in which the user equipment is operative to attach to the second cellular network, wherein the mode switching is in response to a trigger event; and

controlling the user equipment such that it operates in a second mode in which the user equipment is operative to attach to the second cellular network, the user equipment having a second power consumption when operating in the second mode, the second power consumption being different from the first power consumption,

wherein the trigger event relates to at least one of a data payload size, a transmission interval, a buffer status, payload data context, or a required coverage.

19. The method of claim 18 , wherein the user equipment comprises:

a radio interface; and

a processing device coupled to the radio interface to control the radio interface, the processing device being operative to control a mode switching between a first mode in which the user equipment is configured for communication with a first cellular network and a second mode in which the user equipment is configured for communication with a second cellular network,

the user equipment having a first power consumption when operating in the first mode and a second power consumption when operating in the second mode, the second power consumption being different from the first power consumption.