WO2015149855A1

WO2015149855A1 - Transmission of uplink physical layer control information

Info

Publication number: WO2015149855A1
Application number: PCT/EP2014/056675
Authority: WO
Inventors: Esa Tapani Tiirola; Timo Erkki Lunttila; Kari Juhani Hooli
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2014-04-03
Filing date: 2014-04-03
Publication date: 2015-10-08

Abstract

To offload some uplink control information sent on a physical uplink control channel to a secondary cell, configuration information indicating a secondary cell as an indicated cell via which uplink control information may be transmitted is sent to a user apparatus, and when the user apparatus receives one or more downlink assignments triggering sending of uplink control information on a physical uplink control channel, the user apparatus uses a physical uplink control channel on the primary cell if the one or more downlink assignments were received via the primary cell, or primary cell associated cells; otherwise a physical uplink control channel on the indicated cell is used.

Description

TRANSMISSION OF UPLINK PHYSICAL LAYER CONTROL INFORMATION

FIELD

The invention relates to the field of telecommunications and, particularly, to transmitting uplink physical layer control information.

BACKGROUND

The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with dis-closures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context .

The evolvement of wireless cellular communications technologies and different services increase user needs to obtain over a wireless connection same broadband services that are obtained via a fixed connection. To fulfil both mobility requirements and increasing speed requirements, one step in the evolution path towards fourth generation (4 G) and beyond cellular systems is an LTE-A (long term evolution - advanced) . One feature of LTE-A is carrier aggregation, in which two or more component carriers (a component carrier is a carrier of an independently operable bandwidth unit) are aggregated in order to support wider transmission bandwidths, and hence increase capacity. The aggregated carriers are carriers from serving cells, one of which is a primary cell, PCell, and the other possible serving cells are secondary cells, SCells. The serving cells typically differ in that they have different frequencies but that need not to be the case. Further, the primary cell can be a macro cell and the secondary cells can be small cells within the coverage area of the primary cell. Physical layer transmissions in LTE-A uplink comprise three physical uplink channels, a physical uplink shared channel (PUSCH) , a physical uplink control channel (PUCCH) and a physical random access channel (PRACH) . When carrier aggregation is implemented, all uplink control information is transmitter using PUCCH on the primary cell. That may cause some problems when the amount of secondary cells increases, for example in a scenario in which several remote radio heads are providing small cells under the primary cell, and uplink control information for all the remote radio heads is sent via PUCCH on the primary cell.

SUMMARY

A general aspect of the invention provides a mechanism for offloading uplink control information transmitted over PUCCH. Various aspects of the invention comprise a method, an apparatus, a computer program product and a system as defined in the independent claims. Further embodiments of the invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figure 1 shows simplified architecture of a system and block diagrams of some apparatuses according to an exemplary embodiment;

Figures 2 and 3 are flow charts illustrating exemplary functionalities;

Figure 4 illustrates exemplary configurations for PUCCHs; and

Figures 5 and 6 are schematic block diagrams of exemplary apparatuses .

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment ( s ) in several locations, this does not

necessarily mean that each such reference is to the same embodiment ( s ) , or that the feature only applies to a single embodiment. Single features of different

embodiments may also be combined to provide other

embodiments .

Embodiments of present invention are applicable to any user apparatus (i.e. user eguipment, user terminal), a network apparatus (i.e. network node, access point) providing radio access, corresponding components,

corresponding apparatuses, and/or to any communication system or any combination of different communication systems supporting carrier aggregation. The communication system may be a wireless communication system or a communication system utilizing both fixed networks and wireless networks. The protocols used and the

specifications of communication systems, and apparatuses, especially in wireless communication, develop rapidly. Such development may reguire extra changes to an

embodiment. Therefore, all words and expressions should be interpreted broadly and are intended to illustrate, not to restrict, the embodiment.

In the following, different embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access

architecture LTE-A. Other examples of the radio access architecture include 4G and 5G radio access networks.

A general architecture of an exemplary radio access system 100 is illustrated in Figure 1. Figure 1 is a simplified system architecture only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. It is apparent to a person skilled in the art that the system may also comprise other functions and structures that are not illustrated, for example connections to the core network/system.

The exemplary radio access system 100 illustrated in Figure 1 comprises user eguipments 110 (only one

illustrated in Figure 1) and one or more access points 120 (only one illustrated in Figure 1) providing one or more cells .

The user eguipment 110 illustrates one type of an

apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with user eguipment may be implemented with a corresponding apparatus. The user eguipment 110 refers to a portable computing device that includes wireless mobile communication devices operating with or without a

subscriber identification module (SIM), including, but not limited to, the following types of devices: mobile phone, smart-phone, personal digital assistant (PDA), handset, laptop computer, e-reading device, tablet. The user eguipment 110 is configured to perform one or more of user eguipment functionalities described below with an

embodiment, and it may be configured to perform

functionalities from different embodiments . For this purpose, the user eguipment comprises an uplink control information unit (UCIU) 111 for providing functionality to form and transmit uplink control information over PUCCH on a primary cell or over PUCCH on a secondary cell according to one or more of the embodiments described below and memory for at least temporarily maintaining configuration information 112 for the uplink control information unit 111. Examples of the configuration information will be described below. Some of the configuration information may be predefined and hence stored permanently or semipermanently, and some received over the primary cell, or all is received over the primary cell, and stored semi- permanently, i.e. until configuration information

replacing the semi-permanently stored configuration information is received.

In the example of Figure 1, the access point 120 depicts an apparatus providing via a primary cell access to the network the user eguipments and the access point are connected to. In an LTE-A system, such an access point is an evolved node B (eNB) . The evolved node B 120, or any corresponding access point apparatus, is a computing device configured to control the radio resources, and connected to the evolved packet core network, thereby providing the user eguipment 110 a connection to the communication system. Typically, but not necessarily, the evolved node B comprises all radio-related functionalities of the communication whereby the evolved node B, for example, schedules transmissions by assigning certain uplink resources for the user eguipment and informing the user eguipment about transmission formats to be used. The evolved node B 120 is configured to perform one or more of evolved node B functionalities described below with an embodiment, and it may be configured to perform

functionalities from different embodiments. For this purpose, the evolved node B comprises an offloading unit (OU) 121 for PUCCH and memory 122 for at least temporarily storing at least association information that will be described in more detail below.

Further, in the example of Figure 1, a service area comprises, for illustrative purposes only, four cells: a primary cell 101 (Pcelll) and three secondary cells 102, 102', 102'' (Scelll, Scell2, Scell4). It should be appreciated that a service area may comprise any amount of secondary cells, starting from zero. It should be

appreciated that in a service area there may be multiple overlapping macro cells and/or multiple small cells. Some of the small cells may be overlapping. However, one of the macro cells is configured as Pcell for one user eguipment. In other words, for one user eguipment, there is only one PCell but different user eguipments may have different macro cells configured as the Pcells, the result being that within a service area there are one or more Pcells.

In the examples below it is assumed that each cell, regardless whether it is a primary cell or one of

secondary cells, has an identifier that is unigue at least within a service area formed by the primary cell and the one or more secondary cells so that the cells are

identifiable .

Figure 2 is a flow chart illustrating an exemplary functionality of the evolved node B providing the primary cell, or more precisely, an exemplary functionality of the offloading unit. For the sake of clarity, the

functionality is described assuming that one user

eguipment is offloaded. Figure 2 starts in a situation in which PUCCH uplink control information offloading is triggered (step 201), and one of the secondary cells is selected in step 202, to be a cell to which the uplink control information is offloaded. This is called below as UCI-cell. The reasons why the offloading is triggered and why a certain

secondary cell is selected to be the UCI-cell, bears no significance to the implementation. For example, a predefined strategy may be that PUCCH load is kept as uniformly distributed between different secondary cells as possible in which case the evolved node B monitors PUCCH load in the primary cell and in the selected secondary cells at the same time. It should be appreciated that the load monitoring at the same time may be performed for other purposes as well. Another exemplary strategy may be an energy saving strategy in which PUCCH load is

concentrated into one or more secondary cells.

When the UCI-cell is selected, zero or more further downlink component carriers, i.e. secondary cells, are associated with the primary cell, the primary cell being itself a component carrier, and the rest on the service area with the UCI-cell in step 203 in such a way that a secondary cell that is not a UCI-cell is associated either with a primary cell or with the UCI-cell. By means of associating some of the downlink component carriers with the primary cell and some downlink component carriers with the UCI-cell for the user eguipment, uplink control information load on PUCCH on the primary cell will be reduced .

Different examples of associations, using the cells illustrated in Figure 1 and assuming that the selected UCI-cell is Scelll are as follows:

alternative 1: no secondary cell is associated with

Pcelll,

alternative 2: Scell 2 is associated with Pcelll,

alternative 3: Scell 3 is associated with Pcelll

alternative 4: Scell 2 and Scell 3 are associated with Pcelll . When, especially in the above example, the primary cell is associated at most with 1 secondary cell, the usage of explicitly allocated PUCCH resources on the primary cell will be minimized.

Then PUCCH-related parameters, like configurations for periodic channel state information (CSI) reports and/or scheduling reguests (SRs), and/or what PUCCH format to use for HARQ (Hybrid automatic repeat reguest) ACK/NACK

(acknowledgement/negative acknowledgement) procedure, and/or possible PUCCH resources to be used in HARQ

ACK/NACK transmission, are determined in step 204. For example, PUCCH resources for CSI and SR are reserved only from the UCI-cell or in an alternative solution PUCCH resources for CSI and SR are reserved from the UCI-cell and the primary cell. An example of resource allocations for periodic CSI and SR is illustrated in Figure 3. It should be appreciated that herein "scheduling reguest" means positive scheduling reguest, i.e., that UE has data to transmit in uplink.

PUCCH formats differ in types of information that PUCCH can carry, in number of bits per subframe and in used modulation and/or multiplexing scheme. The different PUCCH formats for LTE-A are described in specification 3GPP TS 36.213 V12.0.0 (2013-12) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) ; Physical layer procedures" (Release 12) in chapter 5.1.2 "Physical uplink control channel".

However, it should be appreciated that any other suitable definitions may be used. Then the configuration

information including the PUCCH related parameters, information/indication on the UCI-cell (indicated cell), and at least primary cell associations are sent in step 205 to the user eguipment, for example using radio resource control (RRC) signalling on the primary cell. Instead of sending mere primary cell associations, from which the user eguipment is configured to conclude that any cell not mentioned is associated with the UCI-cell, the associations may indicate for each serving cell whether it is the UCI-cell or the primary cell or

associated with either the UCI-cell or the primary cell.

Then the configuration and associations are stored in step 206. After that the eNB continues the communications with the user equipment. For example, it receives various reports form the user equipment, like downlink measurement reports. Based on downlink measurement reports, user equipment activity, measured component carrier qualities, etc., the eNB may trigger carrier aggregation

reconfiguration, including cancelling the UCI-cell

configuration. During the reconfiguration ambiguity time, the eNB schedules the user equipment so that the user equipment does not send uplink control information on the reconfigured UCI-cell. This may be seen as an enabler for improved mobility handling between access points in small cells as smooth UCI-cell deactivation is facilitated.

Although in the above it was assumed that one user

equipment is offloaded, it should be appreciated that two or more user equipments may be offloaded to the same UCI- cell, or to another UCI-cell. If two or more user

equipments are offloaded to the same UCI-cell, the PUCCH related parameters may be the same or they may be

different. However, even if the user equipments are offloaded to the same UCI-cell at the same time with the same PUCCH related parameters, the information is

preferably sent individually to each PUCCH offloaded user equipment .

Figure 3 is a flow chart illustrating an exemplary

functionality of user equipment, or more precisely, an exemplary functionality of the uplink control information unit UCIU. In the example of Figure 3, it is assumed that following transmission rules are preconfigured (or preset) to the user equipment:

mode A:

• use when physical down link control channel (PDCCH) or enhanced physical downlink control channel (EPDCCH) scheduling physical down link shared channel (PDSCH) is received via the UCI-cell only

• HARQ-ACK feedback is transmitted on UCI-cell PUCCH using PUCCH Format 1 a/1 b PUCCH resource for PUCCH Format 1 a/1 b is derived from the UCI-cell resources implicit resource allocation. The implicit resource allocation may use the lowest control channel element index of PDCCH, or the lowest enhanced control channel element index of EPDCCH with the signalled resource offset to determine the PUCCH resource. The implicit resource allocation applied use the rules defined for non-carrier aggregation communication use when physical down link control channel (PDCCH) ) or enhanced physical downlink control channel (EPDCCH) scheduling physical down link shared channel (PDSCH) is received only via the primary cell or only via cells associated with the primary cell (including the primary cell)

HARQ-ACK feedback is transmitted using PUCCH on the primary cell

HARQ-ACK multiplexing and PUCCH resource allocation rules defined for carrier aggregation may be applied as such so that Carriers/cells not associated with PCell are not taken into account

When PDSCH is scheduled on the primary cell only and no secondary cells are associated with the primary cell

o HARQ-ACK feedback is transmitted using

PUCCH Format la/lb

o PUCCH resource for PUCCH Format la/lb is derived from the primary cell resources using implicit resource allocation. The implicit resource allocation may use the same rules as those used in mode A

When the primary cell and one or more

secondary cells are associated with the primary cell o HARQ-ACK feedback is transmitted using PUCCH format la/lb if PDSCH is scheduled on the primary cell only, otherwise HARQ-ACK feedback is transmitted using either PUCCH format lb with channel selection or PUCCH format 3, depending on the configuration information received from eNB

o resources for PUCCH may be allocated implicitly or explicitly using rules defined for carrier aggregation

mode C :

• use whenever uplink control information is multiplexed on physical uplink shared channel PUSCH, and when mode A or mode B are not usable

• HARQ-ACK feedback is transmitted on UCI-cell PUCCH when HARQ-ACK feedback is not multiplexed on PUSCH.

· HARQ-ACK multiplexing and PUCCH resource allocation rules defined for carrier aggregation may be applied as such, so that the UCI-cell takes the role of the primary cell in determination of uplink control information transmissions, and HARQ-ACK codebook is dimensioned according to the total number of serving cells configured for the user eguipment and respective transmission modes

· HARQ-ACK feedback is transmitted using PUCCH

Format 1/lb with channel selection or PUCCH format 3, depending on configuration information received from the eNB The above modes A, B and C support PUCCH fallback to the primary cell. Another advantage provided by means of the above modes is that it allows setting different PUCCH strategies for the cases when PUCCH is conveyed via macro and small cell layers. For example, it's possible to have PUCCH format lb with channel selection (which is resource efficient and has good coverage) for a macro layer (in configuration B) while having PUCCH Format 3 configured for a small cell layer (in configuration C) . It should be appreciated that herein "mode" means user eguipment behavior that may be partially configured and partially specified in a corresponding standard.

Referring to Figure 3, when the user eguipment receives in step 301 the configuration information, it in step 302 updates its configuration information correspondingly. Then at least one downlink assignment on PDCCH or EDPCCH is received in step 303, and the user eguipment checks in step 304 whether or not uplink control information (UCI) is to be multiplexed on the physical uplink shared channel PUSCH. The decision on multiplexing depends on the configuration information received from eNodeB and on uplink scheduling grants that UE has received. If the uplink control information is to be multiplexed on the physical uplink shared channel, HARQ-ACK is transmitted in step 305 using the configuration C.

If the uplink control information is not to be multiplexed on the physical uplink shared channel (step 304), it is checked in step 306, whether or not each of the at least one downlink assignment was received via the UCI-cell only. If yes, HARQ-ACK is transmitted in step 307 using the mode A.

If at least one of the at least one downlink assignment was not received via the UCI-cell (step 306), it is checked in step 308, whether or not each of the at least one downlink assignment was received via the primary cell associated cells only. If yes, HARQ-ACK is transmitted in step 309 using the mode B.

If at least one of the at least one downlink assignment was not received via a primary cell associated cell (step 308), i.e. for all other cases, HARQ-ACK is transmitted in step 305 using the mode C.

The steps 303 to 309 are repeated each time a downlink assignment is received on the physical downlink control channel or on the enhanced physical downlink control channel .

In another example, the configuration is simpler when PUCCH is to be used for transmitting the uplink control information (i.e. sending on PUCCH is triggered/selected) : use PUCCH on the primary cell if physical down link control channel (PDCCH) scheduling physical downlink shared channel (PDSCH) is transmitted only via the primary cell or only via cells associated with the primary cell (including the primary cell), otherwise use PUCCH on the UCI-cell. In other words, after receiving the PDCCH downlink assignment or assignments in step 303, the checking in step 308 is performed and based on the outcome, PUCCH on the primary cell or PUCCH on the UCI- cell is selected. (For example, in LTE-A the uplink control information is transmitted on PUSCH if the user eguipment has PUSCH scheduled for that subframe on any of the serving cells, and simultaneous PUCCH and PUSCH transmission is not configured. However, any other rules to determine when to use/select PUSCH and when PUCCH may be used as well . )

It should be appreciated that the above modes are only examples and any other mode may be used as well. Further, it is possible to use only two of the modes A, B and C. If PUCCH resources are reserved for periodic CSI and/or

SR, and uplink control information is offloaded to a UCI- cell, there are two options amongst which to choose how to handle the situation.

A first option is to reserve resources for the periodic CSI and/or SR only on the UCI-cell. In the first option, uplink control information is transmitted using PUCCH on the UCI-cell whenever periodic CSI and/or SR is to be transmitted and there is no PUSCH allocated.

A second option is that resources for the periodic CSI and/or SR are reserved from both the UCI-cell and the primary cell, preferably so that the periodicity on the primary cell is higher than the periodicity on the UCI- cell. However, it should be appreciated that the

periodicities may be the same or the periodicity on the the primary cell may be lower than the periodicity on the UCI-cell. Figure 4 illustrates an example of a mode 400 in which periodic resources 401, 401' are reserved from both the UCI-cell and the primary cell. In the example

illustrated in Figure 4, every 27^th PUCCH resource 401' on the primary cell is received for the periodic CSI and/or SR, whereas in principle every 9^th PUCCH resource 401 on the UCI-cell is received for the periodic CSI and/or SR, but because every 3rd reservation occurs at the same time as a corresponding reserved resource on the primary cell, the periodicity on the UCI-cell is 9^th, 18^th, 9^th, 18^th, etc. This facilitates a smooth fall-back from the UCI-cell to the primary cell. However, it should be appreciated that any other resource scheme may be used.

When the mode 400 illustrated in Figure 4 is used,

following additional rules should be followed when there is CSI and/or SR to be sent:

• CSI and/or SR on the received UCI-cell resource and HARQ-

ACK/NACK to be sent: multiplex considering UCI-cell as a primary cell

• CSI and/or SR on the received primary cell resource and

HARQ-ACK/NACK to be sent:

o if physical downlink control channel (PDCCH) scheduling physical downlink shared channel (PDSCH) is transmitted only via the primary cell or only via cells associated with the primary cell (including the primary cell), multiplex

o all other cases: the user equipment may be configured either to drop CSI and/or SR and transmit HARQ- ACK/NACK via PUCCH on the UCI-cell; or drop HARQ-ACK/NACK corresponding to secondary cells not associated with the primary cell, and transmit remaining HARQ-ACK/NACK multiplexed with CSI and/or SR via PUCCH on the primary cell. The configuration may be received from the eNB or the configuration may be preconfigured to the user equipment. As is evident from the above, by means of offloading transmissions of the uplink control information to the small cells PUCCH overhead on the primary cell may be reduced. A user eguipment that is offloaded to a UCI-cell, i.e. is in a "PUCCH Scell mode", uses only or mostly implicit PUCCH resources on PCell while higher layer configured PUCCH resource allocations are concentrated to the UCI-cell. This means that less PUCCH resources need to be reserved on the primary cell and therefore there remains enough PUSCH resources so that the primary cell (macro cell) is able to serve user eguipments that do not support the carrier aggregation, or are not located on the coverage area of small cells, or are not suitable for a carrier aggregation involving small cells, because of their high velocity, for example. Further, when less PUCCH resources are reserved, there is also more resources for actual uplink user data.

Still an advantage is that PUCCH transmission may be made as efficient as possible, without loss on the spectral efficiency or on uplink coverage as there is no need for parallel PUCCH transmission. This is useful especially if a carrier aggregation configured user eguipment ends to be on coverage limit. In that situation, avoidance of unnecessary parallel uplink control information

transmissions provides added reliability.

The steps, messages and related functions described above in Figures 2 and 3 are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps/points or within the steps/points, and other messages sent. For example, the evolved node B may select amongst user eguipments served by the primary cell, which ones are to be

offloaded. Some of the steps/points/messages or part of the steps/points/messages can also be left out or replaced by a corresponding step/point/message or part of the step/point/message .

The technigues described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment/example/implementation comprises not only prior art means, but also means for implementing the one or more functions of a corresponding apparatus described with an embodiment and it may comprise separate means for each separate function, or means may be configured to perform two or more functions. For example, the uplink control information unit and/or the offloading unit and/or algorithms may be software and/or software-hardware and/or hardware and/or firmware components (recorded indelibly on a medium such as read-only-memory or embodied in hardwired computer circuitry) or combinations thereof.

Software codes may be stored in any suitable,

processor/computer-readable data storage medium (s) or memory unit(s) or article (s) of manufacture and executed by one or more processors/computers, hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or combinations thereof. For a firmware or software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. Software codes may be stored in any suitable, processor/computer-readable data storage medium(s) or memory unit(s) or article (s) of manufacture and executed by one or more

processors/computers .

Figure 5 is a simplified block diagram illustrating some units for an apparatus 500 configured to be a user apparatus, i.e. an apparatus comprising at least the uplink control information unit. In the illustrated example the apparatus comprises one or more interfaces (IF) 501 for receiving and transmitting information over the radio access network, one or more user interfaces (U- IF) 501' for interaction with a user, a processor 502 configured to implement at least the uplink control information unit functionality described herein with a corresponding algorithm/algorithms 503 and a memory 504 usable for storing a program code reguired at least for the codec. The memory 504 is also usable for storing other possible information, like the configurations, modes, information on the UCI-cell, and the association.

Figure 6 is a simplified block diagram illustrating some units for an apparatus 600 configured to be a network apparatus (access point) comprising the offloading unit, or corresponding functionality. In the illustrated example, the apparatus comprises an interface (IF) 601 for receiving and transmitting information over the radio access network, a processor 602 configured to implement at least the offloading unit functionality described herein, with corresponding algorithms 603, and memory 604 usable for storing a program code reguired for the offloading unit and the algorithms. The memory 604 is also usable for storing other possible information, like information on configurations, modes and the associations.

In other words, an apparatus configured to provide the user apparatus, and/or an apparatus configured to provide the network apparatus, or an apparatus configured to provide one or more corresponding functionalities, is a computing device that may be any apparatus or device or eguipment configured to perform one or more of

corresponding apparatus functionalities described with an embodiment/example/implementation, and it may be

configured to perform functionalities from different embodiments/examples/implementations. The unit(s)

described with an apparatus may be separate units, even located in another physical apparatus, the distributed physical apparatuses forming one logical apparatus providing the functionality, or integrated to another unit in the same apparatus .

The apparatus configured to provide the user apparatus, and/or an apparatus configured to provide the network apparatus, or an apparatus configured to provide one or more corresponding functionalities may generally include a processor, controller, control unit, micro-controller, or the like connected to a memory and to various interfaces of the apparatus. Generally the processor is a central processing unit, but the processor may be an additional operation processor. Each or some or one of the units and/or algorithms described herein may be configured as a computer or a processor, or a microprocessor, such as a single-chip computer element, or as a chipset, including at least a memory for providing storage area used for arithmetic operation and an operation processor for executing the arithmetic operation. Each or some or one of the units and/or algorithms described above may comprise one or more computer processors, application-specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD),

programmable logic devices (PLD) , field-programmable gate arrays (FPGA) , and/or other hardware components that have been programmed in such a way to carry out one or more functions of one or more

embodiments/implementations/examples. In other words, each or some or one of the units and/or the algorithms

described above may be an element that comprises one or more arithmetic logic units, a number of special registers and control circuits .

Further, the apparatus configured to provide the user apparatus, and/or an apparatus configured to provide the network apparatus, or an apparatus configured to provide one or more corresponding functionalities may generally include volatile and/or non-volatile memory, for example EEPROM, ROM, PROM, RAM, DRAM, SRAM, double floating-gate field effect transistor, firmware, programmable logic, etc. and typically store content, data, or the like. The memory or memories may be of any type (different from each other), have any possible storage structure and, if reguired, being managed by any database management system. The memory may also store computer program code such as software applications (for example, for one or more of the units/algorithms) or operating systems, information, data, content, or the like for the processor to perform steps associated with operation of the apparatus in accordance with examples/embodiments. The memory, or part of it, may be, for example, random access memory, a hard drive, or other fixed data memory or storage device implemented within the proces sor/apparatus or external to the

processor/apparatus in which case it can be

communicatively coupled to the proces sor/network node via various means as is known in the art. An example of an external memory includes a removable memory detachably connected to the apparatus .

The apparatus configured to provide the user apparatus, and/or an apparatus configured to provide the network apparatus, or an apparatus configured to provide one or more corresponding functionalities may generally comprise different interface units, such as one or more receiving units and one or more sending units . The receiving unit and the transmitting unit each provides an interface in an apparatus, the interface including a transmitter and/or a receiver or any other means for receiving and/or

transmitting information, and performing necessary functions so that the information, etc. can be received and/or sent. The receiving and sending units may comprise a set of antennas, the number of which is not limited to any particular number .

Further, the apparatus may comprise other units.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways . The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A method comprising:

receiving, from a network apparatus providing a primary serving cell, configuration information indicating a secondary serving cell as an indicated cell via which uplink control information may be transmitted and

comprising at least an indication of primary cell

associated serving cells, the primary cell associated serving cells comprising at least the primary serving cell ;

receiving via one or more serving cells one or more downlink assignments triggering sending of uplink control information on a physical uplink control channel;

in response to receiving the one or more downlink

assignments only via the primary cell associated serving cells, using a physical uplink control channel on the primary serving cell for sending uplink control

information; otherwise

using a physical uplink control channel on the indicated serving cell for sending uplink control information.

2. A method as claimed in claim 1, further comprising: having at least two different modes for sending uplink control information, the modes defining at least physical uplink control channel format to be used, and how physical uplink control channel resources are selected; and selecting, in response to the one or more downlink assignments triggering sending of uplink control

information on a physical uplink control channel, a mode to use based on the one or more serving cells from which the one or more downlink assignments were received.

3. A method as claimed in claim 2, wherein the at least two modes further define one or more rules by means of which a mode to be used to transmit the uplink control information is selectable, and the method further

comprises selecting, in response to receiving the one or more downlink assignments and the one or more downlink assignments triggering sending of uplink control

information on a physical uplink control channel, a mode according to the rules, and sending the feedback according to the selected mode.

4. A method as claimed in claim 2 or 3, wherein the uplink control information to be sent is hybrid automatic repeat reguest acknowledgement/negative acknowledgement feedback and the at least two modes define one or more rules for the hybrid automatic repeat reguest

acknowledgement/negative acknowledgement feedback.

5. A method as claimed in any of the preceding claim, further comprising:

reserving periodic resources for channel state information reports and/or for scheduling reguests on the physical uplink control channel on the indicated cell; and

using the reserved resources on the physical uplink control channel on the indicated cell whenever there is a periodic channel state information report and/or a positive scheduling reguest to be sent and no physical uplink shared channel is allocated.

6. A method as claimed in any of the preceding claims 1 to 4, further comprising:

reserving periodic resources for channel state information reports and/or for scheduling reguests on the physical uplink control channel on the indicated cell with a first periodicity and on the physical uplink control channel on the primary serving cell with a second periodicity; and using the next reserved resource being available whenever there is a periodic channel state information report and/or a positive scheduling reguest to be sent.

7. A method as claimed in claim 6, wherein the second periodicity is higher than the first periodicity, and the method further comprises: using the resource on the primary serving cell whenever the resource on the primary serving cell and on the indicated cell overlap and whenever there is a periodic channel state information report and/or a scheduling reguest to be sent.

8. A method as claimed in claim 5, 6 or 7, further comprising :

having one or more additional rules defining how to handle sending of a periodic channel state information report and/or a scheduling reguest and other uplink control information if they are to be sent at the same time; and using the additional rules when the other uplink control information and the periodic channel state information report and/or the scheduling reguest are to be sent at the same time.

9. A method comprising:

selecting, by an apparatus providing a primary serving cell to a user apparatus, one of one or more secondary serving cells to be an indicated cell via which the user apparatus may transmit to the apparatus uplink control information on a physical uplink control channel; and sending to the user apparatus configuration information comprising information on the indicated cell.

10. A method as claimed in claim 9, further comprising: associating secondary serving cells with the primary serving cell or the indicated cell so that a secondary serving cell is associated either with the primary serving cell or with the indicated cell; and

sending to the user apparatus information on the

associations in the configuration information.

11. A method as claimed in claim 9 or 10, further

comprising :

defining at least physical uplink control channel

parameters for the indicated cell; and sending to the user apparatus the defined physical uplink control channel parameters in the configuration

information .

12. A method as claimed in claim 9, 10 or 11, further comprising:

defining at least one of the following: one or more physical uplink control channel formats to be used with the uplink control information, how to allocate the resources for the uplink control information, whether the resources are allocated from the primary serving cell or from the indicated cell, allocating periodic resources for channel state information reports and/or for scheduling reguests on the physical uplink control channel on the indicated cell, allocating periodic resources for channel state information reports on the primary serving cell; and sending a result of the defining to the user apparatus.

13. A user apparatus comprising:

at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor to cause the user apparatus to use, in response to receiving from a primary serving cell configuration information indicating a secondary serving cell as an indicated cell via which uplink control information may be transmitted and comprising at least an indication of primary cell associated serving cells, the primary cell associated serving cells comprising at least the primary serving cell, a physical uplink control channel on a primary cell if one or more downlink assignments triggering sending of uplink control information on a physical uplink control channel are received only via the primary cell associated serving cells, and otherwise to use a physical uplink control channel on the indicated cell for sending uplink control information.

14. A radio access network apparatus comprising: at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor: select one of one or more secondary serving cells to be an indicated cell via which a user apparatus may transmit uplink control information to the radio access network apparatus on a physical uplink control channel; and send to the user apparatus configuration information comprising at least information on the indicated cell.

15. An apparatus comprising means for implementing a method as claimed in any of claims 1 to 8.

16. An apparatus comprising means for implementing a method as claimed in any of claims 9 to 12.

17. An apparatus as claimed in claim 16, wherein the apparatus is configured to be an evolved node B.

18. A computer program product comprising program

instructions configuring an apparatus to perform any of the steps of a method as claimed in any one of claims 1 to 12 when the computer program is run.

19. A system comprising:

at least one radio access network comprising at least one apparatus as claimed in claim 16 or 17; and

at least one apparatus as claimed in claim 15.