Power limit reporting in a communication system using carrier aggregation
The invention relates to methods for informing an eNodeB on the transmit power status of a user equipment in a mobile communication system using component carrier (CC) aggregation. Furthermore, the invention is also related to the implementation of these methods by hardware and their implementation in software. The invention proposes procedures that allow the eNodeB to recognize the power usage status of a UE in a communication system using carrier aggregation. The UE indicates to the eNodeB, when the UE is close to using its total maximum UE transmit power or when it has exceeded same. This is achieved by the UE including indicator(s) and/or new MAC CEs to one or more protocol data units transmitted on respective component carriers within a single sub-frame that is providing the eNodeB with power status information. The MAC CEs may report a per-UE power headroom. Alternatively, the MAC CEs may report per-CC power headrooms and/or power reductions applied to the respective uplink CCs.
1. A method for informing an eNodeB of a transmit power status of a user equipment (UE) in a mobile communication system using component carrier aggregation, in which two or more component carriers (CCs) are aggregated, wherein the method comprises the following steps performed by the UE:
generating a power status report that includes: (i) a power headroom report indicative of a difference between a nominal UE maximum transmit power and an estimated UE transmit power, per each configured and activated uplink CC, and (ii) a CC specific maximum transmission power, P CMAX,c , which is said nominal UE maximum transmit power and which is obtained based on subtraction of a CC specific amount of power reduction from a higher bound of UE maximum transmit power, P CMAX — H,c , for each configured and activated uplink CC,
wherein the CC specific maximum transmission power, P CMAX,c , for each configured and activated CC is included in the power status report when the UE has a resource assignment for the configured and activated uplink CC, and
transmitting the power status report to the eNodeB.
2. The method according to claim 1 , wherein the transmission of the power status report is triggered at activation of a configured uplink CC.
3. The method according to claim 1 , wherein the power status report takes into account a Physical Uplink Control Channel (PUCCH) power transmitted on the same sub-frame.
4. The method according to claim 1 , wherein in case the power headroom report is to be transmitted for a configured and activated uplink CC for which there is no resource assignment available in the given sub-frame, the UE generates the power status report for the CC based on a predefined uplink grant or a predefined Physical Uplink Shared Channel (PUSCH) power.
5. The method according to claim 1 , wherein the power headroom report and the CC specific maximum transmission power, P CMAX,c , of each configured and activated uplink CC are included into a single Media Access Control (MAC) control element that is used for multiple power headroom reporting with a bitmap,
wherein a bit set at a certain position of the bitmap indicates that there is a power headroom report field included in the MAC control element for the associated CC.
6. The method according to claim 5 , wherein the MAC control element for multiple power headroom reporting further includes indicators that indicate the presence of the associated CC specific maximum transmission power, P CMAX,c , for the corresponding power headroom report, respectively.
7. A user equipment (UE) for informing an eNodeB of a transmit power status of the UE in a mobile communication system using component carrier aggregation, in which two or more component carriers (CCs) are aggregated, wherein the UE comprises
a processor configured to generate a power status report that includes: (i) a power headroom report indicative of a difference between a nominal UE maximum transmit power and an estimated UE transmit power, per each configured and activated uplink CC, and (ii) a CC specific maximum transmission power, P CMAX,c , which is said nominal UE power reduction from a higher bound of UE maximum transmit power, P CMAX — H,c , for each configured and activated uplink CC,
wherein the CC specific maximum transmission power, P CMAX,c , for each configured and activated CC is included in the power status report when the UE has a resource assignment for the configured and activated uplink CC, and
a transmitter configured to transmit the power status report to the eNodeB.
8. The UE according to claim 7 , wherein the transmitting of the power status report is triggered at activation of a configured uplink CC.
9. The UE according to claim 7 , wherein the power status report takes into account a Physical Uplink Control Channel (PUCCH) power transmitted on the same sub-frame.
10. The UE according to claim 7 , wherein in case the power headroom report is to be transmitted for a configured and activated uplink CC for which there is no resource assignment available in the given sub-frame, the processor generates the power status report for the CC based on a predefined uplink grant or a predefined Physical Uplink Shared Channel (PUSCH) power.
11. The UE according to claim 7 , wherein the power headroom report and the CC specific maximum transmission power, P CMAX,c , of each configured and activated uplink CC are included into a single Media Access Control (MAC) control element that is used for multiple headroom reporting with a bitmap,
wherein a bit set at a certain position of the bitmap indicates that there is a power headroom report field included in the MAC control element for the associated CC.
12. The UE according to claim 11 , wherein the MAC control element for multiple power headroom reporting further includes indicators that indicate the presence of the associated CC specific maximum transmission power, P CMAX,c , for the corresponding power headroom report, respectively.