Methods and network nodes for evaluating a connection

1. A method for evaluating a connection between a first network node, that serves a first cell, and a User Equipment (UE), in which the connection is via a second network node that serves a second cell, wherein the first network node and the second network node are different network nodes to provide a dual connectivity to the UE, the method comprising:

configuring the UE, via the first cell of the first network node, to send and receive a transmission via the second cell of the second network node;

initiate sending, from the first network node to the UE via the second cell of the second network node, a first message comprising a trigger for the UE to respond by sending a second message to the second network node via the second cell, the second message comprising feedback relating to quality of the connection;

when the second message comprising the feedback from the UE in response to the first message is not received within a time period, repeating initiating sending, to the UE via the second cell of the second network node, the first message comprising a trigger for the UE to respond by sending the second message comprising the feedback relating to the connection;

obtaining a time value difference between the sending of said first message and receiving of said second message in the first network node via the second cell of the second network node; and

evaluating use of the connection for providing the dual connectivity to communicate with the UE using both the first network node and the second network node, based on the obtained time value difference and the feedback,

wherein the connection is established by splitting bearer at a Packet Data Convergence Protocol (PDCP) layer of the first network node and rerouting the connection to the second network node.

2. The method according to claim 1 , wherein the time value difference between the sending of the first message and the receiving of the second message is measured by the first network node.

3. The method according to claim 1 , wherein the time value difference between the sending of the first message and the receiving of the second message is measured at the second network node.

4. The method according to claim 1 ,

wherein the time value difference relates to a first round trip path comprising the first network node, the second network node, the UE, the second network node, and the first network node,

or wherein the time value difference relates to a second round trip path comprising the second network node, the UE, and the second network node,

or wherein the time value difference relates to a third round trip path comprising the first network node, the second network node, and the first network node.

5. The method according to claim 4 , wherein the third round trip path is estimated based on the first round trip path and the second round trip path.

6. The method according to claim 1 , wherein the first message comprises a limited amount of data, which is limited to an amount of data that is required by the UE to be able to respond to the first message.

7. The method according to claim 1 , wherein the first message comprises no user data.

8. The method according to claim 1 , wherein the first network node is a Master eNodeB (MeNB) serving the first cell, and wherein the second network node is a Secondary eNodeB (SeNB) serving the second cell.

9. A network device for evaluating a connection between a first network node, that serves a first cell, and a User Equipment (UE), in which the connection is via a second network node that serves a second cell, wherein the first network node and the second network node are different network nodes to provide a dual connectivity to the UE, the network device is configured to:

configure the UE, via the first cell of the first network node, to send and receive a transmission via the second cell of the second network node;

after configuration of the UE, initiate to send, from the first network node to the UE via the second cell of the second network node, a first message comprising a trigger for the UE to respond by sending a second message to the second network node via the second cell, the second message comprising feedback relating to the connection;

when the second message comprising the feedback from the UE in response to the first message is not received within a time period, repeat to initiate sending, to the UE via the second cell of the second network node, the first message comprising a trigger for the UE to respond by sending the second message comprising the feedback relating to the connection;

obtain a time value difference between the sending of said first message and receiving of said second message in the first network node via the second cell of the second network node, wherein said second message comprises the feedback relating to the connection sent from the UE in response to the first message; and

evaluate use of the connection for providing the dual connectivity to communicate with the UE using both the first network node and the second network node, based on the obtained time value difference and the feedback;

wherein the connection is established by splitting bearer at a Packet Data Convergence Protocol (PDCP) layer of the first network node and rerouting the connection to the second network node.

10. The network device according to claim 9 ,

wherein the time value difference relates to a first round trip path comprising the first network node, the second network node, the UE, the second network node, and the first network node,

or wherein the time value difference relates to a second round trip path comprising the second network node, the UE, and the second network node,

or wherein the time value difference relates to a third round trip path comprising the first network node, the second network node, and the first network node.

11. The network device according to claim 9 , wherein the first network node is a Master eNodeB (MeNB) serving the first cell, and wherein the second network node is a Secondary eNodeB (SeNB) serving the second cell.