Power-efficient measurement reporting for multi/dual connectivity in cellular communication networks

1. A method for power saving in multi-connectivity, comprising:

selecting by a user equipment, based on an uplink transmission power to a first node and an uplink transmission power to at least one second node, a Radio Resource Control, RRC, connection for transmitting measurement reports, wherein the user equipment compares the uplink transmission power of the first node to the uplink transmission power of the at least one second node and selects the RRC connection for transmitting to the at least one second node wherein the uplink transmission power for the first node is greater than the uplink transmission power of the at least one second node plus a hysteresis threshold, and wherein the user equipment starts a timer such that measurement reports are sent to the at least one second node at least until expiration of the timer, wherein the selecting further includes:

calculating the uplink transmission power to the first node;

calculating the uplink transmission power to the at least one second node; and

wherein the selecting further comprises comparing the calculated uplink transmission power to the first node and the calculated uplink transmission power to the at least one second node; and

transmitting by the user equipment, using the selected RRC connection, a measurement report associated with a transmission of the first node and/or a measurement report associated with a transmission of the at least one second node.

2. The method according to claim 1 , wherein the selecting further comprises selecting between an RRC connection to the first node and an RRC connection to the at least one second node.

3. The method according to claim 1 , wherein the selected RRC connection comprises at least one Signaling Radio Bearer, SRB.

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

determining that the uplink transmission power associated with the selected RRC connection is above a threshold; and

responsive to the determination, transmitting using the selected RRC connection.

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

determining that the uplink transmission power associated with a primary RRC connection is above a threshold; and

responsive to the determination, selecting the primary RRC connection and transmitting using the primary RRC connection.

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

determining that the uplink transmission power to the at least one second node is lower than, or lower by a threshold than, the uplink transmission power to the first node; and

responsive to the determination, transmitting to the at least one second node the measurement report associated with a transmission of the first node.

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

applying a penalty timer, wherein the penalty timer defines a time period during which the selected RRC connection is to be used; and

upon expiry of the penalty timer, enabling reselection of the RRC connection for transmitting measurement reports.

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

determining that the uplink transmission power to the first node is lower, or lower by a threshold, than the uplink transmission power to the at least one second node; and

responsive to the determination, transmitting to the first node the measurement report associated with a transmission of the at least one second node.

9. The method according to claim 1 , wherein the measurement report associated with the transmission of the first node and the measurement report associated with the transmission of the at least one second node are embedded to a single RRC message by the user equipment.

10. The method according to claim 1 , wherein the first node is a master node and the at least one second node is a secondary node.

11. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform:

select, by a user equipment, based on an uplink transmission power to a first node and an uplink transmission power to at least one second node, a Radio Resource Control, RRC, connection for transmitting measurement reports, wherein the user equipment compares the uplink transmission power of the first node to the uplink transmission power of the at least one second node and selects the RRC connection for transmitting to the at least one second node wherein the uplink transmission power for the first node is greater than the uplink transmission power of the at least one second node plus a hysteresis threshold, and wherein the user equipment starts a timer such that measurement reports are sent to the at least one second node at least until expiration of the timer, wherein the selecting further includes the user equipment:

calculating the uplink transmission power to the first node;

calculating the uplink transmission power to the at least one second node; and

wherein the selecting further comprises comparing the calculated uplink transmission power to the first node and the calculated uplink transmission power to the at least one second node; and

transmit, by the user equipment, using the selected RRC connection, a measurement report associated with a transmission of the first node and/or a measurement report associated with a transmission of the at least one second node.