Methods and nodes for detecting activation of serving cell

1. A method, implemented by a network node of a wireless communication system supporting carrier aggregation, for detecting that an additional serving cell is activated, wherein the network node serves a wireless device configured with a first serving cell and the additional serving cell, the method comprising:

configuring the wireless device to transmit feedback information associated with the additional serving cell at a first rate;

transmitting a command to the wireless device to activate the additional serving cell;

detecting the activation of the additional serving cell based on reception of feedback information from the wireless device;

configuring the wireless device to transmit feedback information associated with the additional serving cell at a second rate after activation of the additional serving cell, wherein the second rate is lower than the first rate.

2. The method of claim 1 , wherein the wireless device is configured to transmit feedback information associated with the additional serving cell at the first rate at reception of the command to activate the additional serving cell, or at activation of the additional serving cell.

3. The method of claim 2 , wherein the configuring the wireless device to transmit feedback information associated with the additional serving cell at the second rate is performed by configuring the wireless device to transmit feedback information associated with the additional serving cell at the first rate during a defined period of time after which feedback information is to be transmitted at the second rate.

4. The method of claim 1 , wherein the configuring the wireless device to transmit feedback information associated with the additional serving cell at the second rate is performed at or after detecting the activation of the additional serving cell.

5. The method according to claim 1 , further comprising:

receiving a capability from the wireless device indicating whether the wireless device is capable of autonomously adjusting a rate for transmitting feedback information associated with the additional serving cell at activation of the additional serving cell; and

determining, based on the received capability, whether to configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell, respectively.

6. The method of claim 5 , further comprising when the received capability indicates that the wireless device is capable of autonomously adjusting the rate for transmitting feedback information:

determining not to configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell respectively;

transmitting information defining the first and the second rate to the wireless device, for enabling the wireless device to autonomously adjust the rate for transmitting feedback information at activation of the additional serving cell.

7. The method of claim 1 , further comprising:

determining whether at least one of following criteria is met:

that intra-band contiguous carrier aggregation is configured;

that the additional serving cell is collocated with the first serving cell of the network node;

that a measurement report for the additional serving cell before activation is available; and

that radio characteristics of the radio environment for the wireless device are stable since reception of the wireless device measurement report for the additional serving cell;

configuring the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell, respectively, only if at least one of the criteria is met.

8. A method, implemented by a wireless device supporting carrier aggregation and configured with a first serving cell and an additional serving cell, for enabling detection of activation of the additional serving cell by a network node serving the wireless device, the method comprising:

receiving a command from the network node to activate the additional serving cell;

in response to the received command:

adjusting a rate for transmitting feedback information associated with the additional serving cell to a first rate; and

activating the additional serving cell;

adjusting the rate for transmitting feedback information associated with the additional serving cell to a second rate, after activating the additional serving cell, wherein the second rate is lower than the first rate.

9. The method of claim 8 , wherein information defining the first rate and the second rate is received from the network node.

10. The method of claim 8 , wherein the rate is adjusted to the second rate when a period of time has lapsed from activating the additional serving cell.

11. The method of claim 10 , wherein information defining the period of time is received from the network node.

12. The method of claim 8 :

further comprising receiving a configuration to transmit feedback information associated with the additional serving cell at the second rate from the network node;

wherein the rate is adjusted to the second rate in response to the received configuration.

13. The method of claim 8 , further comprising transmitting a capability to the network node indicating that the wireless device is capable of autonomously adjusting the rate for transmitting feedback information associated with the additional serving cell at activation of the additional serving cell.

14. The method of claim 8 , further comprising:

determining whether at least one of following criteria is met:

that intra-band contiguous carrier aggregation is configured;

that the additional serving cell is collocated with the first serving cell of the network node;

that a time period between performing a measurement for the additional serving cell and reception of the command from the network node to activate the additional serving cell is shorter than a threshold; and

that radio characteristics of the radio environment for the wireless device are stable since performing the measurement for the additional serving cell;

adjusting the rate for transmitting feedback information associated with the additional serving cell to the first rate and to the second rate before and after activating the additional serving cell, respectively, only if at least one of the criteria is met.

15. The method of claim 8 , wherein the feedback information comprises at least one of sounding reference signal (SRS) transmissions and channel state information (CSI) reports.

16. The method of claim 8 , wherein the first serving cell is a primary serving cell and the additional serving cell is a secondary serving cell.

17. A network node of a wireless communication system, the network node for detecting that an additional serving cell is activated, the network node configured to support carrier aggregation and to serve a wireless device configured with a first serving cell and the additional serving cell, the network node comprising:

a transceiver;

a processing circuit operatively connected to the transceiver and configured to:

configure the wireless device to transmit feedback information associated with the additional serving cell at a first rate;

transmit, via the transceiver and to the wireless device, a command to activate the additional serving cell;

detect the activation of the additional serving cell based on reception of feedback information from the wireless device;

configure the wireless device to transmit feedback information associated with the additional serving cell at a second rate after activation of the additional serving cell, wherein the second rate is lower than the first rate.

18. The network node of claim 17 , wherein the processing circuit is configured to configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate at reception of the command to activate the additional serving cell, or at activation of the additional serving cell.

19. The network node of claim 18 , wherein the processing circuit is configured to configure the wireless device to transmit feedback information associated with the additional serving cell at the second rate by configuring the wireless device to transmit feedback information associated with the additional serving cell at the first rate during a defined period of time after which feedback information is to be transmitted at the second rate.

20. The network node of claim 17 , wherein the processing circuit is configured to configure the wireless device to transmit feedback information associated with the additional serving cell at the second rate at or after detecting the activation of the additional serving cell.

21. The network node of claim 17 , wherein the processing circuit is configured to:

receive, via the transceiver and from the wireless device, a capability indicating whether the wireless device is capable of autonomously adjusting a rate for transmitting feedback information associated with the additional serving cell at activation of the additional serving cell;

determine whether to configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell, respectively, based on the received capability.

22. The network node of claim 21 , wherein the processing circuit is configured to, when the received capability indicates that the wireless device is capable of autonomously adjusting the rate for transmitting feedback information:

determine not to configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell respectively;

transmit, via the transceiver and to the wireless device, information defining the first and the second rate for enabling the wireless device to autonomously adjust the rate for transmitting feedback information at activation of the additional serving cell.

23. The network node of claim 21 , wherein the processing circuit is configured to:

determine whether at least one of following criteria is met:

that intra-band contiguous carrier aggregation is configured;

that the additional serving cell is collocated with the first serving cell of the network node;

that a measurement report for the additional serving cell before activation is available; and

that radio characteristics of the radio environment for the wireless device are stable since reception of the wireless device measurement report for the additional serving cell;

configure the wireless device to transmit feedback information associated with the additional serving cell at the first rate and at the second rate before and after activation of the additional serving cell, respectively, only if at least one of the criteria is met.

24. A wireless device for enabling detection of activation of an additional serving cell by a network node of a wireless communication system supporting carrier aggregation, the network node serving the wireless device, the wireless device configured with a first serving cell and the additional serving cell, the wireless device comprising:

a transceiver;

processing circuit operatively connected to the transceiver and configured to:

receive, via the transceiver and from the network node, a command to activate the additional serving cell;

in response to the received command:

adjust a rate for transmitting feedback information associated with the additional serving cell to a first rate; and

activate the additional serving cell;

adjust the rate for transmitting feedback information associated with the additional serving cell to a second rate, after activating the additional serving cell, wherein the second rate is lower than the first rate.

25. The wireless device of claim 24 , wherein the processing circuit is configured to receive information defining the first rate and the second rate from the network node via the transceiver.

26. The wireless device of claim 24 , wherein the processing circuit is configured to adjust the rate to the second rate when a period of time has lapsed from activation of the additional serving cell.

27. The wireless device of claim 26 , wherein the processing circuit is configured to receive information defining the period of time from the network node via the transceiver.

28. The wireless device of claim 24 , wherein the processing circuit is configured to:

receive, via the transceiver and from the network node, a configuration to transmit feedback information associated with the additional serving cell at the second rate;

adjust the rate for transmitting feedback information to the second rate in response to the received configuration.

29. The wireless device of claim 24 , wherein the processing circuit is configured to transmit a capability via the transceiver to the network node, the capability indicating that the wireless device is capable of autonomously adjusting the rate for transmitting feedback information associated with the additional serving cell at activation of the additional serving cell.

30. The wireless device of claim 24 , wherein the processing circuit is configured to:

determine whether at least one of following criteria is met:

that intra-band contiguous carrier aggregation is configured;

that the additional serving cell is collocated with the first serving cell of the network node;

that a time period between performing a measurement for the additional serving cell and reception of the command from the network node to activate the additional serving cell is shorter than a threshold; and

that radio characteristics of the radio environment for the wireless device are stable since performing the measurement for the additional serving cell;

adjust the rate for transmitting feedback information associated with the additional serving cell to the first rate and to the second rate before and after activating the additional serving cell respectively, only if at least one of the criteria is met.