Secondary cell activation/deactivation in carrier aggregation

1. A method of operating a radio access node comprising:

determining whether support from a secondary cell is required for a wireless device to communicate with the radio access node; and

in response to determining that support from the secondary cell is required,

calculating, based on a last known channel condition outer-loop value for the secondary cell, a modified channel condition outer-loop value for the secondary cell; and

using the modified channel condition outer-loop value in an initial activation decision step for the secondary cell, the initial activation decision step comprising either activating the secondary cell or refraining from activating the secondary cell, based on the calculated modified channel condition outer-loop value for the secondary cell.

2. The method of claim 1 , wherein the initial activation decision step comprises activating the secondary cell in response to determining that the sum of a device reported channel condition value and the modified channel condition outer-loop value is above an activation threshold.

3. The method of claim 1 wherein calculating the modified channel condition outer-loop value for the secondary cell comprises setting the modified channel condition outer-loop value to be the maximum value between zero and the last known channel condition outer-loop value for the secondary cell.

4. The method of claim 2 further comprising:

setting an initial link adaptation channel condition outer-loop value to be the minimum value between zero and the last known channel condition outer-loop value for the secondary cell; and

following activating the secondary cell, using the initial link adaptation channel condition outer-loop value in an initial link adaptation step for the secondary cell.

5. The method of claim 1 wherein calculating the modified channel condition outer-loop value for the secondary cell comprises:

determining whether the last known channel condition outer-loop value for the secondary cell is negative; and

in response to determining that the last known channel condition outer-loop value is negative, setting the channel condition outer-loop value to be the sum of the last known channel condition outer-loop value and a small predefined positive adjustment constant; or

in response to determining that the last known channel condition outer-loop value is not negative, setting the channel condition outer-loop value to be zero.

6. The method of claim 1 wherein calculating the modified channel condition outer-loop value for the secondary cell comprises

determining whether the last known channel condition outer-loop value for the secondary cell is negative; and

in response to determining that the last known channel condition outer-loop value is negative, setting the channel condition outer-loop value to be the sum of the last known channel condition outer-loop value and a small predefined positive adjustment constant; and

in response to determining that the last known channel condition outer-loop value is not negative, setting the channel condition outer-loop value to be the maximum value between zero and the last known channel condition outer-loop value.

7. The method of claim 2 , further comprising a deactivation decision step, the deactivation decision step comprising:

maintaining the secondary cell in the active state in response to determining that the sum of a device reported channel condition value and an updated channel condition outer-loop value is above a deactivation threshold below the activation threshold; and

deactivating the secondary cell in response to determining that the sum of a device reported channel condition value and the updated channel condition outer-loop value is below the deactivation threshold.

8. The method of claim 7 , wherein the deactivation decision step is performed subsequent to receiving a first negative acknowledgement (NACK) signal.

9. The method of claim 2 wherein activating the secondary cell comprises using a first stepsize in a set of initial iterations of an outer-loop adjustment algorithm (OLA), wherein the first stepsize defines a value by which the OLA algorithm is increased upon receipt of an acknowledgement (ACK) signal, wherein the first stepsize is used until the receipt of a negative acknowledgement (NACK) signal, after which a second stepsize, less than the first stepsize, is used.

10. The method of claim 1 wherein the radio access node is a base station.

11. A radio access node comprising circuitry, the circuitry containing instructions which when executed cause the radio access node to:

determine whether support from a secondary cell is required for a wireless device to communicate with the radio access node; and

in response to determining that support from the secondary cell is required,

calculate, based on a last known channel condition outer-loop value for the secondary cell, a modified channel condition outer-loop value for the secondary cell; and

use the modified channel condition outer-loop value in an initial activation decision step for the secondary cell, the initial activation decision step comprising either activating the secondary cell or refraining from activating the secondary cell, based on the calculated modified channel condition outer-loop value for the secondary cell.

12. The radio access node of claim 11 , wherein said circuitry comprises

at least one processor; and memory coupled to said processor, said memory comprising said instructions.

13. A radio access node for operating in a cellular communications network, comprising:

a circuit for determining whether support from a secondary cell is required for a wireless device to communicate with the radio access node;

a circuit for calculating, based on a last known channel condition outer-loop value for the secondary cell, a modified channel condition outer-loop value for the secondary cell in response to determining that support from the secondary cell is required; and

a circuit for using the modified channel condition outer-loop value in an initial activation decision step for the secondary cell, the initial activation decision step comprising either activating the secondary cell or refraining from activating the secondary cell, based on the calculated modified channel condition outer-loop value for the secondary cell.