WO2013166684A1

WO2013166684A1 - Apparatuses, methods and computer program products related to improvements in uplink control signaling in carrier aggregation scenarios

Info

Publication number: WO2013166684A1
Application number: PCT/CN2012/075288
Authority: WO
Inventors: Erlin Zeng; Chunyan Gao; Shuang TAN; Jari Juhani Mattila
Original assignee: Renesas Mobile Corporation
Priority date: 2012-05-10
Filing date: 2012-05-10
Publication date: 2013-11-14

Abstract

According to at least an aspect of the present invention, there is provided a method, comprising receiving data in a carrier aggregation scenario based on at least two component carriers, deriving at least a first, e.g. CSI and a second, e.g. HARQ, feedback control signal for being fed back in a feedback signaling, evaluating a property of the first feedback control signal, deciding, based on the evaluated property of the first feedback control signal, to use a specific one of a plurality of feedback control signalings, switching, based on the decision, to the specific feedback control signaling decided to be used, and limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed. Other aspects of the present invention encompass a corresponding apparatus and computer program product.

Description

APPARATUSES, METHODS AND COMPUTER PROGRAM PRODUCTS RELATED TO IMPROVEMENTS IN UPLINK CONTROL SIGNALING IN CARRIER AGGREGATION SCENARIOS Field of the invention

The present invention relates to apparatuses, methods and computer program products configured to achieve improvements in uplink control signaling in carrier aggregation scenarios.

A typical scenario or environment in relation to such uplink control signaling in carrier aggregation scenarios is carrier aggregation as applied in conjunction with e.g. the LTE or LTE-A telecommunication standard. Background

Mobile communication is constantly making progress. Under one aspect of such progress, data throughput in downlink, i.e. from a network transceiver device such as a base station BS or eNB (evolved NodeB) towards a terminal such as a mobile station, MS, or user equipment, UE, is crucial. lin particular with an increase in data traffic for modern applications such as wireless Internet access or video streaming, or more generally, multi-media applications running/executed on such terminals, data throughput needs to be increased. Such increase can e.g . be accomplished gy virtue of adopting carrier aggregation scenarios.

The present invention is related on an ongoing 3GPP working item named "LTE Carrier Aggregation Enhancements". One of the topics covered by this working item is the uplink, UL, control enhancement in LTE Rel- 11.

As working assumptions, the following agreements have been made in 3GPP RANI #68bis : - Multi-Cell Periodic CSI Multiplexing for DL CA is supported in Rel-ll;

this is based on existing UL channel formats (not yet decided which formats)

- Multi-cell HARQ-ACK and Periodic CSI Multiplexing for DL CA is supported in Rel-ll;

A Rel-ll UE that supports PUCCH Format 3 can be configured for simultaneous transmission of multi-cell HARQ-ACK feedback, SR and periodic CSI report for one serving cell on PUCCH Format 3;

For a Rel-ll UE that is configured for Format lb with channel selection, simultaneous transmission of multi-cell HARQ-ACK feedback and a periodic CSI report on PUCCH Format 2a/2b is not yet decided;

Likewise, it is not yet decided whether separate coding or joint coding of HARQ-ACK and CSI shall be adopted. A UE may be configured with- UCCH format lb with channel selection for HARQ-ACK feedback for several reasons, e.g.,

- for FDD (Frequency Division Duplex) , if UE or el\IB doesn't support PUCCH format 3, or

- for TDD (Time Division Duplex), the HARQ-ACK payload size is too large if PUCCH format 3 is configured, as channel selection only supports up to

4 HARQ-ACK bits which can be much smaller than PUCCH format 3.

When a UE is configured with PUCCH format lb with channel selection, it is still an open issue, as mentioned above, how to multiplex HARQ-ACK and periodic CSI in a subframe. In the following, as an example, a focus is laid on simultaneous transmission of multi-cell HARQ-ACK feedback and a periodic CSI report on PUCCH Format 2a/2b. According to the use case of channel selection, we assume that a UE is configured with 2 component carriers (CCs).

For FDD such multiplexing is easier. For example, in one document it is proposed to use HARQ-ACK spatial bundling to create one HARQ-ACK bit for Pcell and Scell, respectively, so that the two bits can be multiplexed with periodic CSI based on PUCCH format 2b. However, that solution for FDD cannot solve the issue for TDD, as in LTE Rel-10, there is already time domain bundling per CC when UE is configured with channel selection.

According to another document, two bundled HARQ-ACK bits are created for each CC, which means the total number of HARQ-ACK bits are four. Therefore, it is still open issue how these four HARQ-ACK bits can be supported by PUCCH format 2b.

Due to the above mentioned problem, in a still further document it is proposed to limit such multiplexing only to FDD. However, this is not an efficient solution as periodic CSI has to be dropped if there is collision with HARQ-ACK.

In another document, it is proposed, for TDD, when simultaneous AckNack and CQI is present, that two ACK/NACK bits of PCC with channel selection can be transmitted using the reference signal and two ACK/NACK bits of SCC can be encoded jointly with the CQI information bits in Normal CP, which are corresponding to last two bit sequences of (20, A). Dropping CQI and only transmitting the ACK/NACK in Extended CP. The issue with this solution is a degraded performance compared with the original PUCCH format 2b, as the payload size is increased from two to four. Further, in another document it is proposed to introduce further CC- domain bundling to reduce the total payload size to two. This solution results in throughput loss, which is contradictory to the motivation of avoiding periodic CSI dropping. Since inherent to those mechanisms or solutions there is a throughput loss and/or degraded performance and/or an increase in payload, irrespective of the above proposals there is still a need to further improve such systems.

Summary

Various aspects of examples of the invention are set out in the claims.

According to an aspect of the present invention, there is provided

a method as defined in claim 1, and

an apparatus as defined in claim 12.

Advantageous further developments are set out in respective dependent claims. According to a further aspect of the present invention, as set out in claim 23, respectively, there are provided computer program products comprising respective computer-executable components which, when the program is run on a computer, are configured to perform the above method aspects, respectively.

That is, such computer program products also encompass computer readable storage media comprising a set of computer-executable instructions which, when the program is run on a device (or on a processor or processing unit thereof which may be part of a controller or control unit or control module), such as a terminal UE and its processor, cause the device to perform the method aspects. In particular, the above computer program product/products may be embodied as a computer- readable storage medium. Accordingly, under at least aspects of this invention, improvements are achieved in that adaptations of HARQ-ACK and periodic CSI multiplexing are made. AT least examples of those aspects of the present invention are directed to a simultaneous transmission of multi-cell HARQ-ACK feedback and a periodic CSI report on PUCCH Format 2a/2b. More specifically, in at least some examples, it is proposed an adaptation of HARQ-ACK and periodic CSI multiplexing in PUCCH for the case when a UE is configured with PUCCH format lb with channel selection.

Thus, the following advantages can be named as example advantages for at least some embodiments of the present invention :

- there is no need to restrict the downlink scheduling to Pcell or Scell in a semi-static manner, but the network is able to schedule either Pcell or

Scell in any subframe;

- such approach is less restrictive compared with only transmitting the two HARQ-ACK bits corresponding to Pcell or Scell;

- with a UE specific N_pCSI_MAX, the mode adaptation can depend on UE's UL SINR condition; for example, if the UL SINR is not able to support a total payload size of (4 +N_pCSI_MAX), UE will fall back to other option which has lower requirements on UL SINR.

Embodiments of the present invention can be applied to/embodied in relation to e.g. LTE radio access, or LTE-A radio access, in particular in modems and/or wireless devices and/or modules and/or chipsets thereof, in particular those related to/inserted in or insertable to terminals such as user equipments or "smartphones" or the like. Aspects of the invention would be reflected by corresponding adaptations to standards such as at least TS 36.212 and TS 36.213.

Brief description of drawings For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which : Fig. 1 illustrates one example of a carrier aggregation scenario; and

Fig 2 illustrates one example of a flowchart according to at least an aspect of the present invention.

Description of example embodiments

Exemplary aspects and/or embodiments of the invention will be described herein below.

Generally, the invention is implemented in a framework of e.g. an telecommunication system which uses carrier aggregation, CA, and more particularly, the invention affects a terminal (user equipment UE) operated within such a framework.

As a mere example only, the description refers to such modules or apparatuses related to user equipments, UEs, which conform to the LTE standard and are arranged / configured for communication in a CA (carrier aggregation) scenario, as the wireless communication modules. However, this does not preclude the use of other wireless communication modules achieving similar functionalities, or the use of other communication standards such as LTE-A and beyond, as long as carrier aggregation is applied/applicable. Also, the bandwidth of wireless communication is not crucial for the present invention.

General technical details of such CA scenarios, e.g. under LTE and adopted communication protocols are publicly available. A repeated detailed description of each such property/functionality of the known LTE system is considered dispensable as those skilled in the pertinent art of technology will readily understand the description as given herein. Examples of the present invention exploit those basic properties and at least in aspects modify the functionality so as to obtain the advantages of at least some embodiments of the present invention.

Fig. 1 illustrates one example of a carrier aggregation scenario. As shown in Fig. 1, a network transceiver device such as a eNB, denoted by 1, applies carrier aggregation CA for downlink transmission of data to a terminal, e.g. a user equipment UE denoted by 2. The data carried in CA in downlink comprise at least DL control channels such as the PDSCH and the PDCCH. The terminal 2 feeds back feedback control signals in uplink, UL, to the eNB. The uplink feedback comprises at least an uplink control channel such as the PUCCH . Data and/or signals carried on the PUCCH comprise at least CSI/CQI information (also referred to as a first feedback control signal) and HARQ related information (ACKs/NACKs) (also referred to as a second feedback control signal).

The eNB 1 comprises at least a control module 11 which controls, among other parts of the eNB (not shown/discussed herein) a receiver/ transmitter module 12 of the eNB, at least in terms of carrier aggregation. The Rx/Tx module 12 comprises carrier modules 121, 122, 123, each of which being configured to provide a distinct carrier for use in carrier aggregation CA. For example, the module 121 provides for a primary component carrier PCC, while the modules 122, 123, provide for respective secondary component carriers SCC# 1 and SCC#n, respectively. The number of possible component carriers is not limited to the number illustrated .

The user equipment UE 2 comprises a receiver/ transmitter module 22, controlled by a controller module 21, which in turn is connected to a memory module 23. The memory module 23 is a storage of control instructions and/or other data, e.g. configuration data, measurement data obtained by a measurement module ((not shown), could be associated to e.g. the control module 21 or the x/Tx module 22, (or be regarded as a separate module of the UE 2)).

Fig 2 illustrates one example of a flowchart according to at least an aspect of the present invention in terms of functionality of the user equipment UE according to at least aspects of the present invention. The processing at the UE in regard to at least an aspect of the present invention starts in a processing S30. The UE, in a processing S31, receives data in a carrier aggregation scenario based on at least two component carriers. In a processing S32, the UE (e.g . the control module21 shown in Fig. 1) derives at least a first, CSI, and a second, HARQ, feedback control signal for being fed back in a feedback signaling. In a processing S33, the UE (control module) evaluates a property of the first feedback control signal, i.e. of the CSI signal . In a processing S34, it is decided, based on the evaluated property of the first feedback control signal, to use a specific one of a plurality of feedback control signalings. (Note that for the purpose of the present description, a "signaling" is intended do denote the manner in which signals/data are conveyed.) It is thus switched (YES in S34), based on the decision, to the specific feedback control signaling decided to be used, and - in relation thereto - in a processing S38, the amount of data being fed back in the specific one of feedback control signalings is limited. In a processing S39, a feedback control channel of predetermined format is used, wherein the format depends on the [imitation performed in S38.

On the other hand, in case of NO in S34, a default feedback control signaling is applied as indicated in S35, and in relation thereto, as shown in S36, a feedback control channel of predetermined format for the default feedback control signaling is used .

After S36 and S39, the process returns to processing S31, and subsequent DL data are received in CA. E.g. the subsequent receipt of DL data occurs in a subsequent subframe according to the scheduling applied by the e B, which depends also on the content of the feedback received from the UE. With regard to S33, evaluating the property of the first feedback control signal comprises evaluating the payload size of the first feedback control signal, and deciding to use a specific one of the feedback control signalings comprises comparing the payload size with a threshold value for the payload size, and it is concluded to switch, if the payload size is greater than the threshold value.

With regard to S33, alternatively, evaluating the property of the first feedback control signal comprises evaluating a type of the first feedback control signal, and deciding to use a specific one of the feedback control signalings comprises comparing the type with a set of predefined types, and it is concluded to switch, if the type is contained in the set of predefined types.

With regard to S38, limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed comprises dropping the first feedback control signal from the feedback signaling, and feeding back only the second feedback control signal.

With regard to S38, alternatively, limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed comprises reducing the payload size of the second feedback control signal, and feeding back the first feedback signal together with the second feedback control signal of reduced payload size. With regard to S39, for feeding back only the second feedback control signal, a feedback control channel of a first predefined format is used, whereas for feeding back the first feedback signal together with the second feedback control signal of reduced payload size, a feedback control channel of a second predefined format is used. In this regard, feeding back the first feedback signal together with the second feedback control signal of reduced payload size comprises multiplexing.

Again with regard to S38, reducing the payload size of the second feedback control signal comprises detecting that data received via one of the component carriers require the second feedback control data, and reducing the payload size responsive thereto.

Again with regard to S38, reducing the payload size of the second feedback control signal comprises detecting that data are received via more than one of the component carriers in a same subframe, and reducing the payload size responsive thereto.

A decision to use a specific one of a plurality of feedback control signalings comprises selecting the specific one of the plurality of feedback control signalings based on a selection criterion or based on a higher layer signaling.

To select among options 1 and 3 (cf. below) to which switching is performed is based on another predefined threshold of number of CSI bits, or based on a use of a higher layer signaling to control the selection for switching to on of those two options. Aspects of the present invention were described herein above on a rather general level. Going, merely for the purpose of giving a more concrete example, into some technical implementation details, those aspects of the present invention are directed to the above mentioned topic of simultaneous transmission of multi-cell HARQ-ACK feedback and a periodic CSI report on PUCCH Format 2a/2b. More specifically, aspects concern adaptations of HARQ-ACK and periodic CSI multiplexing in PUCCH, for example in the case when a UE is configured with PUCCH format lb with channel selection.

According to an individual aspect, there is proposed a way to limit the amount of data in a specific feedback control signaling, i.e. to reduce the HARQ-ACK payload size from four to two. That is, the UE generates two HARQ-ACK bits based on from which CC it receives downlink data transmissions. According to another individual aspect, there is proposed a way to selectively use distinct feedback control channels (of different predefined formats), i .e. to adapt between different HARQ-ACK and periodic CSI multiplexing options (e.g. a default feedback signaling and one or more others). The selection/adaptation is based on an evaluated property of the first feedback control signal, ire. the CSI data, e.g . based on evaluating a predefined threshold of number of periodic CSI bits, or based on evaluating a type of the periodic CSI.

Several options for HARQ-ACK and periodic CSI multiplexing in PUCCH format 2b exist (#l^st scenario / embodiment).

Option 1 : To drop periodic CSI, i.e., only transmit HARQ-ACK using PUCCH format lb with channel selection;

Option 2 (herein assigned as "default option") : To reuse Rel-10 time bundling for TDD, and multiplex HARQ-ACK with periodic CSI as proposed in a prior art document, i.e., two HARQ-ACK bits are jointly encoded with periodic CSI, and the other two HARQ-ACK bits are modulated on reference signal;

Option 3 : To reduce the HARQ-ACK payload size to two and use PUCCH format 2b to multiplex HARQ-ACK with periodic CSI.

One way to reduce HARQ-ACK payload size from four to two is that UE only generates two HARQ-ACK bits using time domain bundling for a CC #A_r if UE receives at least one PDSCH or PDCCH from CC #A that requires HARQ-ACK feedback. With this proposal, there is no need to restrict the downlink scheduling to Pcell or Scell in a semi-static manner, but the network is able to scheduled either Pcell or Scell in any subframe. Therefore, this proposal is less restrictive compared with only transmit the two HARQ-ACK bits corresponding to Pcell or Scell.

A threshold value for the size of the periodic CSI payload is predefined, e.g., N_pCSI_MAX. If the CSI payload size (as an evaluated property) is greater than IM_pCSI_MAX, Option 1 or 3 is used, otherwise Option 2 (as default) is used. Alternatively, the mode adaptation is based on periodic CSI type, e.g., if periodic CSI is one of a set of predefined types, Option 1 or 3 is used, otherwise Option 2 is used. With a UE specific N_pCSI__MAX, the mode adaptation can also depend on UE's UL SINR condition . For example, if the UL SINR is not able to support a total payload size of (4 +N_pCSI_MAX), UE will fallback to Option 1 or 3, which has lower requirement on UL SINR compared with option 2.

The procedures shall be clear according to the above description and in relation to Fig. 2.

The network side determines to use Pcell or Scell for downlink transmissions on a subframe basis. UE assumes that either Pcell or Scell is used in a given subframe, if there is collision between HARQ-ACK and periodic CSI in that subframe. If the UE detects downlink scheduling for both Pcell and Scell, UE treats this as error case and one option in this case is to only generate 2 HARQ-ACK bits for Pcell (hence to limit the amount of data for feedback) . Nonetheless, aspects of the present invention are also applicable for the case when PUCCH format 3 is used (#2^nd scenario / embodiment). For example, if PUCCH format 3 resource is configured for a subframe with HARQ-ACK and periodic CSI multiplexing, according to an aspect of the present invention there is accomplished an adaptation between the following multiplexing options

Option 1 : To drop periodic CSI, i.e., only transmit HARQ-ACK using PUCCH format lb with channel selection

Option 2: To reuse Rel-10 time bundling for TDD and multiplex HARQ-ACK with periodic CSI in PUCCH format 3. HARQ-ACK bits can be jointly encoded with periodic CSI bits, or alternatively HARQ-ACK bits and periodic CSI bits are encoded separately.

Option 3: To reduce the HARQ-ACK payload size to two and use PUCCH format 2b or PUCCH format 3 to multiplex HARQ-ACK with periodic CSI

Periodic CSI types are defined according to 3GPP TS 36.213. More specifically, there are the following types

• Type 1 report supports CQI feedback for the UE selected sub-bands

• Type la report supports subband CQI and second PMI feedback

• Type 2, Type 2b, and Type 2c report supports wideband CQI and PMI feedback

· Type 2a report supports wideband PMI feedback

• Type 3 report supports RI feedback

• Type 4 report supports wideband CQI

• Type 5 report supports RI and wideband PMI feedback

• Type 6 report supports RI and PTI feedback

In LTE Rel-10, some CSI types are prioritized over the others, in case multiple CCs' periodic CSI collide in the same subframe. For example, according to 3GPP TS 36.213, the priority is as the following

1st (=Top) priority: Types 3, 5, 6, 2a

2nd priority: Types 2, 2b, 2c, 4

3rd priority: Types 1, la Normally, the CSI types with higher priority have smaller payload size compared with those with lower priority. In this sense, one optional implementation according to an aspect of the present invention is to predefine that Option 1 or 3 (applicable to both scenarios #1 and #2) is used when periodic CSI type belongs to the set or 1^st priority as above, otherwise Option 2 is used.

Various aspects of the present invention have been described herein above, on a genera! as well as on a specific implementation oriented level.

It is still to be noted that some embodiments of the invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware generally reside on control modules or modems, in general circuitry. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media . In the context of this document, a "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer or smart phone, or user equipment.

As used in this application, the term 'circuitry' refers to all of the following : (a)hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) to combinations of circuits and software (and/or firmware), such as (as applicable) :

(i) to a combination of processor(s) or

(ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or user equipment or any other terminal, or network entity such as a server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application_/ including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone (terminal) or a similar integrated circuit in server, a cellular network device, or other network device.

That is, it can be implemented as/in chipsets to such devices, and/or modems thereof.

If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.

Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims. List of some acronyms used:

CA Carrier Aggregation

CC Component Carrier

PCC Primary Component Carrier

SCC Secondary Component Carrier

UL Uplink

DL Downlink

LTE Long Term Evolution

3GPP 3rd Generation Partnership Project

RAN Radio Access Network

CSI Channel State Information

CQI Channel Quality Indicator

HARQ Hybrid Automatic Repeat Request ACK Acknowledgement

UE User Equipment

PUCCH Physical Uplink Control Channel

SR Scheduling Requests

CP Cyclic Prefix

BS Base Station

eNB evolved NodeB

MS Mobile Station

UE User Equipment

PDCCH Physical Downlink Control CHannel PDSCH Physical Downlink Shared CHannel

LTE Long Term Evolution

Pcell Primary CC

Scell Secondary CC

SINR Signal-to-Interference plus Noise Ratio FDD Frequency Division Duplex

TDD Time Division Duplex According to at least an aspect of the present invention, there is provided a method, comprising receiving data in a carrier aggregation scenario based on at least two component carriers, deriving at least a first (e.g. CSI) and a second (e.g. HARQ) feedback control signal for being fed back in a feedback signaling, evaluating a property of the first feedback control signal, deciding, based on the evaluated property of the first feedback control signal, to use a specific one of a plurality of feedback control signalings, switching, based on the decision, to the specific feedback control signaling decided to be used, and limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed. Other aspects of the present invention encompass a corresponding apparatus and computer program product.

Claims

What is claimed is:

1. A method, comprising

receiving data in a carrier aggregation scenario based on at least two component carriers,

deriving at least a first and a second feedback control signal for being fed back in a feedback signaling,

evaluating a property of the first feedback control signal,

deciding, based on the evaluated property of the first feedback control signal, to use a specific one of a plurality of feedback control signalings,

switching, based on the decision, to the specific feedback control signaling decided to be used, and

limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed.

2. A method according to claim 1, wherein

evaluating the property of the first feedback control signal comprises

evaluating the payload size of the first feedback control signal, deciding to use a specific one of the feedback control signalings comprises comparing the payload size with a threshold value for the payload size, and

concluding to switch, if the payload size is greater than the threshold value.

3. A method according to claim 1, wherein

evaluating the property of the first feedback control signal comprises

evaluating a type of the first feedback control signal,

deciding to use a specific one of the feedback control signalings comprises comparing the type with a set of predefined types, and

concluding to switch, if the type is contained in the set of predefined types.

4. A method according to claim 1, wherein

limiting the amount of data being fed back in the specific one of feedback control signalings to which switching is performed comprises

dropping the first feedback control signal from the feedback signaling, and

feeding back only the second feedback control signal.

5. A method according to claim 1, wherein

reducing the payload size of the second feedback control signal, and feeding back the first feedback signal together with the second feedback control signal of reduced payload size.

6. A method according to claim 4, wherein

for feeding back only the second feedback control signal, a feedback control channel of a first predefined format is used.

7. A method according to claim 5, wherein

for feeding back the first feedback signal together with the second feedback control signal of reduced payload size, a feedback control channel of a second predefined format is used.

8. A method according to claim 7, wherein

feeding back the first feedback signal together with the second feedback control signal of reduced payload size comprises multiplexing.

9. A method according to claim 5, wherein

reducing the payload size of the second feedback control signal comprises, detecting that data received via one of the component carriers require the second feedback control data, and reducing the pay!oad size responsive thereto.

10. A method according to claim 5, wherein

reducing the payload size of the second feedback control signal comprises, detecting that data are received via more than one of the component carriers in a same subframe, and reducing the payload size responsive thereto.

11. A method according to claim 1, wherein

deciding to use a specific one of a plurality of feedback control signalings comprises selecting the specific one of the plurality of feedback control signalings based on a selection criterion or based on a higher layer signaling.

12. An apparatus, comprising:

a control module configured to

receive data in a carrier aggregation scenario based on at least two component carriers,

derive at least a first and a second feedback control signal for being fed back in a feedback signaling,

evaluate a property of the first feedback control signal,

decide, based on the evaluated property of the first feedback control signal, to use a specific one of a plurality of feedback control signalings, switch, based on the decision, to the specific feedback control signaling decided to be used, and

limit the amount of data being fed back in the specific one of feedback control signalings to which switching is performed.

13. An apparatus according to claim 12, wherein

the control module is further configured to evaluate the property of the first feedback control signal by

evaluating the payload size of the first feedback control signal, decide to use a specific one of the feedback control signalings by

comparing the payload size with a threshold value for the payload size, and

conclude to switch, if the payload size is greater than the threshold value.

14. An apparatus according to claim 12, wherein

the control module is further configured to

evaluate the property of the first feedback control signal by

evaluating a type of the first feedback control signal,

decide to use a specific one of the feedback control signalings by

comparing the type with a set of predefined types, and

conclude to switch, if the type is contained in the set of predefined types.

15. An apparatus according to claim 12, wherein

the control module is further configured to

limit the amount of data being fed back in the specific one of feedback control signalings to which switching is performed by

dropping the first feedback control signal from the feedback signaling, and

feeding back only the second feedback control signal.

16. An apparatus according to claim 12, wherein

the control module is further configured to

17. An apparatus according to claim 15, wherein

the control module is further configured to

apply a feedback control channel of a first predefined format for feeding back only the second feedback control signal.

18. An apparatus according to claim 16, wherein

the control module is further configured to

apply a feedback control channel of a second predefined format for feeding back the first feedback signal together with the second feedback control signal of reduced payload size.

19. An apparatus according to claim 18, wherein

the control module is further configured to

apply multiplexing for feeding back the first feedback signal together with the second feedback control signal of reduced payload size.

20. An apparatus according to claim 16, wherein

the control module is further configured to

reduce the payload size of the second feedback control signal based on detecting that data received via one of the component carriers require the second feedback control data, and to reduce the payload size responsive thereto.

21. An apparatus according to claim 16, wherein

the control module is further configured to

reduce the payload size of the second feedback control signal based on detecting that data are received via more than one of the component carriers in a same subframe, and to reduce the payload size responsive thereto.

22. An apparatus according to claim 12, wherein the control module is further configured to

decide to use a specific one of a plurality of feedback control signalings by a selection of the specific one of the plurality of feedback control signalings based on a selection criterion or based on a higher layer signaling .

23. A computer program products comprising respective computer- executable components which, when the program is run on a computer, are configured to

evaluate a property of the first feedback control signal,