Wireless communication system, a wireless device, network nodes, and methods therein, for changing master node for the wireless device

1. A wireless communications system configured to change a master node for a wireless device comprising a processor, the wireless communication system comprising:

a first network node comprising a first processor, a second network node comprising a second processor, and a third network node comprising a third processor, wherein the wireless device, the first network node, the second network node and the third network node are operating in the wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, the master node being a signaling anchor point for the wireless device, wherein the second network node and the third network node are connected to the wireless device as secondary nodes for the wireless device and wherein the wireless communications system is configured to:

receive a first signal using the third network node, which first signal comprises information that the third network node currently connected to the wireless device as a secondary node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device;

transmit, using one of the first network node and the third network node, a second signal to the wireless device, which second signal comprises information about a change of the master node from the first network node to the third network node and information to the wireless device to reuse a second set of existing protocol entities and context for communication with the third network node; and

receive a third signal using the second network node, which third signal comprises information that the third network node is the master node for the wireless device and information to the second network node to reuse a third set of existing protocol entities and context for communication with the wireless device, whereby the master node for the wireless device is changed to the third network node.

2. A wireless device configured to change a master node for the wireless device, wherein the wireless device, a first network node comprising a first processor, a second network node comprising a second processor and a third network node comprising a third processor are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the second network node and the third network node are connected to the wireless device as secondary nodes for the wireless device, and wherein the wireless device comprises:

an input/output interface configured to communicate with the wireless communication system; and

a processor configured to,

receive a signal through the input/output interface, which signal comprises information about a change of the master node from the first network node to the third network node currently connected to the wireless device as a secondary node and information to the wireless device to reuse a set of existing protocol entities and context for communication with the third network node; and

reuse the set of existing protocol entities and context for communication with the third network as the master node.

3. The wireless device of claim 2 , wherein the processor is further configured to:

transmit a first signal through the input/output interface to the third network node, which first signal comprises information that the third network node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device.

4. The wireless device of claim 3 , wherein the processor is further configured to:

receive a first acknowledgement signal from the third network node through the input/output interface, which first acknowledgement signal acknowledges receipt of the first signal.

5. The wireless device of claim 2 , wherein the processor is further configured to:

receive the signal from the first network node or the third network node through the input/output interface.

6. The wireless device of claim 2 , wherein the processor is further configured to:

transmit an acknowledgement signal to the third network node, which acknowledgement signal acknowledges receipt of the signal.

7. The wireless device of claim 2 , wherein the set of existing protocol entities comprise one or more Radio Link Control, RLC, entities and/or one or more Medium Access Control, MAC, entities, and wherein the context comprises one or more of: state information such as a Radio Resource Control, RRC, state; security-related information such as a security capability or a key material; a UE identity such as an identity of a UE-associated logical S1-connection; and a UE radio access capability.

8. The wireless device of claim 2 , wherein the processor is further configured to:

derive a security key to be used in a radio bearer between the wireless device and the third network node; and

configure a Packet Data Convergence Protocol, PDCP, entity for the radio bearer between the wireless device and the third network node.

9. A first network node configured to change a master node for a wireless device, wherein the wireless device comprising a first processor, the first network node, and a third network node comprising a second processor are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the third network node is connected to the wireless device as a secondary node for the wireless device, and wherein the first network node comprises:

an input/output interface configured to communicate with the wireless device and with the second network node and the third network node; and

a processor configured to:

transmit a first signal through the input/output interface to the third network node, which first signal comprises information that the third network node currently connected to the wireless device as a secondary node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device; and

transmit a second signal through the input/output interface to the wireless device, which second signal comprises information about a change of master node from the first network node to the third network node and information to the wireless device to reuse a second set of existing protocol entities and context for communication with the third network node, whereby the master node for the wireless device is changed to the third network node.

10. The first network node of claim 9 , wherein the processor is further configured to:

receive a first acknowledgement signal from the third network node through the input/output interface, which first acknowledgement signal acknowledges receipt of the first signal.

11. The first network node of claim 9 , wherein the first set of existing protocol entities and the second set of existing protocol entities comprise one or more Radio Link Control, RLC, entities and/or one or more Medium Access Control, MAC, entities, and wherein the context comprises one or more of: state information such as a Radio Resource Control, RRC, state; security-related information such as a security capability or a key material; a UE identity such as an identity of a UE-associated logical S1-connection; and a UE radio access capability.

12. The first network node of claim 9 , wherein the processor is further configured to:

prepare to receive data from the third network node.

13. A third network node configured to change a master node for a wireless device comprising a first processor, wherein the wireless device, a first network node comprising a second processor, and a second network node comprising a third processor, and the third network node are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the second network node and the third network node are connected to the wireless device as secondary nodes for the wireless device; and wherein the third network node comprises:

an input/output interface configured to communicate with the wireless device and with the first and second network nodes; and

a processor configured to,

receive a first signal through the input/output interface, which first signal comprises information that the third network node currently connected to the wireless device as a secondary node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device;

transmit a second signal through the input/output interface to the wireless device, which second signal comprises information about a change of master node from the first network node to the third network node and information to the wireless device to reuse a second set of existing protocol entities and context for communication with the third network node; and

transmit a third signal through the input/output interface to the second network node, which third signal comprises information that the third network node is the master node for the wireless device and information to the second network node to reuse a third set of existing protocol entities and context for communication with the wireless device, whereby the master node for the wireless device is changed to the third network node.

14. The third network node of claim 13 , wherein the processor is further configured to:

receive the first signal from the first network node or the wireless device through the input/output interface.

15. The third network node of claim 13 , wherein the processor is further configured to:

transmit a first acknowledgement signal through the input/output interface to the first network node or the wireless device, which first acknowledgement signal acknowledges receipt of the first signal.

16. The third network node of claim 13 , wherein the processor is further configured to:

receive a second acknowledgement signal from the wireless device through the input/output interface, which second acknowledgement signal acknowledges receipt of the second signal.

17. The third network node of claim 13 , wherein the processor is further configured to:

receive a third acknowledgement signal from the second network node through the input/output interface, which third acknowledgement signal acknowledges receipt of the third signal.

18. The third network node of claim 13 , wherein the first set of existing protocol entities and the second set of existing protocol entities comprise one or more Radio Link Control, RLC, entities and/or one or more Medium Access Control, MAC, entities, and wherein the context comprises one or more of: state information such as a Radio Resource Controller, RRC, state; security-related information such as a security capability or a security key; a UE identity such as an identity of a UE-associated logical S1-connection; and a UE radio access capability.

19. The third network node of claim 13 , wherein the processor is further configured to:

transmit a fourth signal through the input/output interface to a core network node, which fourth signal informs the core network node that the third network node is the master node for the wireless device.

20. A method performed by a wireless device to change a master node for the wireless device, wherein the wireless device comprising a first processor, a first network node comprising a second processor, a second network node comprising a third processor, and a third network node comprising a fourth processor are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the second network node and the third network node are connected to the wireless device as secondary nodes for the wireless device, and wherein the method comprises:

receiving a signal, which signal comprises information about a change of the master node from the first network node to the third network node currently connected to the wireless device as a secondary node and information to the wireless device to reuse a set of existing protocol entities and context for communication with the third network node; and

reuse the set of existing protocol entities and context for communication with the third network node as the master node.

21. A method performed by a first network node comprising a first processor to change a master node for a wireless device comprising a second processor, wherein the wireless device, the first network node, and a third network node comprising a third processor are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the third network node is connected to the wireless device as a secondary node for the wireless device, and wherein the method comprises:

transmitting a first signal to the third network node, which first signal comprises information that the third network node currently connected to the wireless device as a secondary node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device; and

transmitting a second signal to the wireless device, which second signal comprises information about a change of master node from the first network node to the third network node and information to the wireless device to reuse a second set of existing protocol entities and context for communication with the third network node, whereby the master node for the wireless device is changed to the third network node.

22. A method performed by a third network node to change a master node for a wireless device, wherein the wireless device comprising a first processor, a first network node comprising a second processor, a second network node comprising a third processor and the third network node comprising a fourth processor are operating in a wireless communications system, wherein the first network node is connected to the wireless device as the master node for the wireless device, wherein the second network node and the third network node are connected to the wireless device as secondary nodes for the wireless device; and wherein the method comprises:

receiving a first signal, which first signal comprises information that the third network node currently connected to the wireless device as a secondary node is to be the master node for the wireless device and information to the third network node to reuse a first set of existing protocol entities and context for communication with the wireless device;

transmitting a second signal to the wireless device, which second signal comprises information about a change of master node from the first network node to the third network node and information to the wireless device to reuse a second set of existing protocol entities and context for communication with the third network node; and

transmitting a third signal to the second network node, which third signal comprises information that the third network node is the master node for the wireless device and information to the second network node to reuse a third set of existing protocol entities and context for communication with the wireless device, whereby the master node for the wireless device is changed to the third network node.