WO2013113142A1

WO2013113142A1 - Method and apparatus for providing uplink control information

Info

Publication number: WO2013113142A1
Application number: PCT/CN2012/070769
Authority: WO
Inventors: Erlin Zeng; Chunyan Gao; Shuang TAN; Jari Mattila
Original assignee: Renesas Mobile Corporation
Priority date: 2012-01-30
Filing date: 2012-01-30
Publication date: 2013-08-08

Abstract

A method, apparatus, and computer program product are provided to provide improved uplink control signaling so as to reduce downlink throughput loss. In this regard, a method, apparatus and computer program product may be provided in order to define an upper bound for supportable feedback payload size. A method, apparatus and computer program product may also adaptively reduce the ACK/NACK payload and/or the CSI payload so as to satisfy the upper bound of the feedback payload. By strategically reducing the ACK/NACK payload and/or the CSI payload, the method, apparatus and computer program product may provide sufficient feedback for reducing or eliminating downlink throughput loss by adherence to the upper bound for the feedback payload.

Description

METHOD AND APPARATUS FOR PROVIDING

UPLINK CONTROL INFORMATION

TECHNOLOGICAL FIELD

[0001] An example embodiment of the present invention relates generally to the transmission of uplink control information and, more particularly, to the uplink transmission of

acknowledgement/negative acknowledgement (ACK/NACK) and channel state information (CSI) bits.

BACKGROUND

[0002] In order to establish and maintain a downlink between an access point, such as a node B, an evolved node B (eNB), a base station or the like, uplink control signaling from the mobile terminal, such as user equipment, to the access point is provided. In at least some instances, such as in conjunction with the uplink control signaling for carrier aggregation, the uplink control signaling may include ACK/NACK bits and CSI bits. However, in systems compliant with Release 10 of the Long Term Evolution (LTE) standard, at least some of the CSI bits may be dropped from the uplink transmission, thereby causing downlink throughput loss.

[0003] The multiplexing of ACK/NACK bits with periodic CSI bits increases the total maximum payload size, which may be impossible to transmit with a single Reed-Muller (RM) encoder in some instances. Additionally, the link performance requirements for the ACK/NACK bits and the CSI bits may be different such that it may be necessary to separately adjust the rate matching for the ACK/NACK bits and the CSI bits. One potential technique for multiplexing ACK NACK bits and CSI bits in a physical uplink control channel (PUCCH) Format 3 channel is shown in Figure 1. As illustrated, separate bit streams are maintained for the ACK NACK bits and the CSI bits. The separate bit streams are separately encoded prior to being jointly interleaved. The multiplexing structure depicted in Figure 1 can accommodate up to 21 bits and may provide for rate matching flexibility. However, if the RM encoders reuse the Release 8 (32,0) RM code, the maximum number of uncoded ACK NACK bits shall be no more than 11. Additionally, due to the ACK/NACK payload restrictions introduced by this separate encoding structure, the ACK/NACK multiplexing with the CSI bits cannot be configured for mobile terminals that operate in accordance with time domain duplexing (TDD) with an ACK/NACK feedback codebook size larger than 11. [0004] In addition to the restrictions upon the multiplexing of the ACK/NACK bits with the CSI bits that are attributable to the limitations imposed by the encoding structure, the uplink geometry of the mobile terminal may also impose certain restrictions. In Release 10, for example, a mobile terminal that operates in accordance with frequency division duplexing (FDD) that supports more than two serving cells or a mobile terminal that operates in accordance with TDD that supports aggregation of more than 1 serving cell can be configured by higher layer signalling to utilize PUCCH Format 3 for transmission of the ACK/NACK bits with the maximum payload size carried by the PUCCH Format 3 being 21 bits. These 21 bits can, in turn, support 20 ACK/NACK bits in TDD as well as one source routing (SR) bit. However, only a fraction of the mobile terminals that operate in accordance with TDD may be able to support 20 ACK/NACK bits due to the geometry of the uplink and power limitations. As such, even though a dual encoder multiplexing structure of the type shown in Figure 1 can support up to 11

ACK/NACK bits and up to 11 CSI bits, a number of mobile terminals may not offer similar support.

[0005] Additionally, the maximum payload that is supported with PUCCH Format 3 depends upon the uplink signal to interference plus noise ratio (SINR), In one example, the required SINR to multiplex ACK NACK bits with 1 CSI bit is -3.6 dB while the SINR required to multiplex 10 ACK/NACK bits with 10 CSI bits is -0.3 dB. Thus, a mobile terminal having a lower SINR may have difficulties in supporting the multiplexing of ACK NACK bits with CSI bits even though the total payload is less than 21 bits,

[0006] In an instance in which the number of ACK NACK bits and CSI bits is below the upper bound of the payload as defined by the coding structure of PUCCH Format 3 and the uplink geometry, the ACK NACK bits may be multiplexed with the CSI bits and then

transmitted via the uplink. However, in an instance in which the number of ACK NACK bits and CSI bits exceeds the upper bounds, the CSI bits may be dropped such that only ACK/NACK bits are transmitted. Alternatively, the ACK NACK or CSI payload may be adjusted to meet the restrictions upon the payload. However, the dropping of CSI bits and the transmission of only ACK NACK bits is restrictive, particularly for TDD, e.g., a system having TDD configuration 2. For example, if one mobile terminal is configured to support three serving cells and the payload upper bound is configured to be 12 bits, the CSI bits for this mobile terminal will always be dropped if the CSI bits collide with the ACK/NACK bits. For another mobile terminal having the same TDD configuration with four serving cells being configured and a payload upper bound of 20 bits, all periodic CSI reports that are larger than 4 bits will have to be dropped. Thus, the dropping rate of the CSI bits can be frequent for some TDD configurations, such as for mobile terminals having relatively low SINR and/or mobile terminals configured to support a large number of carriers. The dropping of the CSI bits may, in turn, negatively impact the downlink throughput of the system.

[0007] The alternative technique of adjusting the ACK/NACK or CSI payload to meet the payload restrictions may reduce the CSI drop rate, but at the expense of having an ACK/NACK or CSI feedback payload which is of a reduced size. In Release 10, the ACK/NACK payload size depends upon the carrier configuration and also upon the TDD configuration for mobile terminals configured to operate in accordance with TDD. As such, more ACK/NACK bits are fed back than is required for physical downlink shared channel (PDSCH) transmission. As such, the number of ACK/NACK bits that are fed back may be reduced to enable the payload upper bound requirement to be met. However, the dynamic adjustment of the ACK/NACK payload size depending upon the scheduled PDSCH dis advantageously leads to payload size ambiguity. As yet another alternative, the ACK/NACK or CSI payload may be adjusted by ACK/NACK bundling feedback, although again at the expense of throughput loss.

BRIEF SUMMARY

[0008] A method, apparatus, and computer program product are therefore provided according to an example embodiment that may provide improved uplink control signaling so as to reduce downlink throughput loss. In this regard, a method, apparatus and computer program product may be provided in accordance with an example embodiment in order to define an upper bound for supportable feedback payload size. A method, apparatus and computer program product of an example embodiment may also adaptively reduce the ACK/NACK payload and/or the CSI payload so as to satisfy the upper bound of the feedback payload. By strategically reducing the ACK NACK payload and/or the CSI payload, the method, apparatus and computer program product of an example embodiment may provide sufficient feedback for reducing or eliminating downlink throughput loss by adherence to the upper bound for the feedback payload.

[0009] In one embodiment, a method is provided that includes determining a maximum number of acknowledgement (ACK)/negative acknowledgement (NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the ACK/NACK bits with channel status information (CSI) bits. The method of this embodiment also includes causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK NACK bits.

[0010] In another embodiment, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer program code configured to, with the processor, cause the apparatus to at least determine a maximum number of acknowledgement (ACK)/negative acknowledgement (N ACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the ACK/NACK bits with channel status information (CSI) bits. The at least one memory and the computer program code are also configured to, with the processor, cause the apparatus of this embodiment to cause an uplink transmission of the ACK NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK NACK bits exceeds the maximum number of ACK/NACK bits.

[0011] In a further embodiment, a computer program product is provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to determine a maximum number of acknowledgement (ACK)/negative acknowledgement (NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the ACK/NACK bits with channel status information (CSI) bits. The computer- readable program instructions of one embodiment also include program instructions configured to cause an uplink transmission of the ACK NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits.

[0012] In yet another embodiment, an apparatus is provided that includes means for determining a maximum number of acknowledgement (ACK)/negative acknowledgement

(NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the ACK/NACK bits with channel status information (CSI) bits. The apparatus of this embodiment also includes means for causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK NACK bits.

[0013] In one embodiment, a method is provided that includes determining a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative acknowledgement (NACK) bits to be fed back in a respective subframe. The method of this embodiment also includes causing an uplink transmission of the ACK NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

[0014] In another embodiment, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer pro ram code configured to, with the processor, cause the apparatus to at least determine a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative acknowledgement (NACK) bits to be fed back in a respective subframe. The at least one memory and the computer program code are also configured to, with the processor, cause the apparatus of this embodiment to cause an uplink transmission of the ACK NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

[0015] In a further embodiment, a computer program product is provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to determine a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative

acknowledgement (NACK) bits to be fed back in a respective subframe. The computer-readable program instructions of one embodiment also include program instructions configured to cause an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

[0016] In a further embodiment, an apparatus is provided that includes means for determining a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative acknowledgement (NACK) bits to be fed back in a respective subframe. The apparatus of this embodiment also includes means for causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Having thus described certain embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0018] Figure 1 is a flow chart illustrating the separate encoding of ACK/NACK bits and CSI bits;

[0019] Figure 2 is a block diagram of an apparatus that may be specifically configured to perform the operations of an example embodiment of the present invention;

[0020] Figure 3 is a flow chart illustrating the operations performed to manage the number of ACK/NACK bits in accordance with one example embodiment of the present invention;

[0021] Figure 4 is a flow chart illustrating the operations performed to manage the number of ACK/NACK bits in accordance with another example embodiment of the present invention;

[0022] Figure 5 is a flow chart illustrating the operations performed to manage the number of CSI bits in accordance with one example embodiment of the present invention;

[0023] Figure 6 is a flow chart illustrating the operations performed to manage the number of CSI bits in accordance with another example embodiment of the present invention;

[0024] Figure 7 is an illustration of a technique for reducing the number of ACK/NACK bits in accordance with an example embodiment of the present invention; [0025] Figure 8 is an illustration of another technique for reducing the number of AC /NACK bits in accordance with an example embodiment of the present invention;

[0026] Figure 9 is a flow chart illustrating the operations performed by an apparatus embodied by a base station in accordance with an example embodiment of the present invention;

[0027] Figure 10 is an illustration to two different scheduling sets in accordance with an example embodiment of the present invention; and

[0028] Figure 11 is an illustration to two different scheduling sets in accordance with another example embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0030] 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 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.

[0031] 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 application specific integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

[0032] In accordance with example embodiments of the present invention, a technique for providing uplink control signaling, such as to provide acknowledgement/negative

acknowledgement (ACK/NACK) and channel state information (CSI) bits as well as source routing (SR) bits for carrier aggregation or other purposes is provided. Referring this regard, a system that supports communications between a mobile terminal and a network, such as an LTE network, an LTE-Advanced (LTE-A) network, a Global Systems for Mobile communications (GSM) network, a Code Division Multiple Access (CDMA) network, e.g., a Wideband CDMA (WCDMA) network, a CDMA2000 network or the like, a General Packet Radio Service (GPRS) network or other type of network, via an access point is shown. Various types of mobile terminals may be employed including, for example, a mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. Regardless of the type of mobile terminal, the mobile terminal may communicate with the network via an access point, such as a Node B, an eNB, a base station, a relay node or other type of access point.

[0033] The communications between the mobile terminal and the access point may include transmissions via an uplink and a downlink that are established between the mobile terminal and the access point. Uplink control signaling including ACK/NACK bits and CSI bits may be provided via the uplink which, among other functions, may assist in the configuration of the downlink. By providing for improved uplink control signaling in accordance with an example embodiment of the present invention, the extent to which the CSI bits are dropped may be reduced which may, in turn, reduce the downlink throughput loss.

[0034] The mobile terminal and the access point may implement example embodiments of the method, apparatus and computer program product in order to provide for improved uplink control signaling. In this regard, the mobile terminal and a network entity, such as the access point, may each embody or otherwise be associated with an apparatus 10 that is generally depicted in Figure 2 and that may be configured in accordance with an example embodiment of the present invention as described below, such as in conjunction with Figures 3 and 4 from the perspective of the mobile terminal and Figures 5 and 6 from the perspective of the access point. However, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

[0035] As shown in Figure 2, the apparatus 10 may include or otherwise be in

communication with a processing system including, for example, processing circuitry that is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

[0036] In an example embodiment, the processing circuitry may include a processor 12 and memory 14 that may be in communication with or otherwise control a communication interface 16 and, in some cases in which the apparatus is embodied by the mobile terminal, a user interface 18. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the mobile terminal or the access point, the processing circuitry may be embodied as a portion of mobile terminal or the access point.

[0037] The user interface 18 (if implemented in embodiments of the apparatus 10 embodied by the mobile terminal) may be in communication with the processing circuitry to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a joystick, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms. In one embodiment, the user interface includes user interface circuitry configured to facilitate at least some functions of the user equipment by receiving user input and providing output.

[0038] The communication interface 16 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the communication interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network and/or any other device or module in communication with the processing circuitry, such as between the mobile terminal and the access point. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

[0039] In an example embodiment, the memory 14 may include one or more non-transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instmctions or the like for enabling the apparatus 10 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 12. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

[0040] The processor 12 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a

microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 14 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein.

Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

[0041] Figures 3 - 6 are flowcharts illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 10 of Figure 2, from the perspective of the mobile terminal in regards to Figures 3 and 4 and a network entity, such as an access point 12 in regards to Figure 5 and 6 in accordance with one embodiment of the present invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a non-transitory memory 14 of an apparatus employing an embodiment of the present invention and executed by a processor 12 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowchart blocks. These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. As such, the operations of Figures 3 - 6, when executed, convert a computer or processing circuitry into a particular machine configured to perfonn an example embodiment of the present invention. Accordingly, the operations of Figures 3 - 6 define an algorithm for configuring a computer or processing circuitry, e.g., processor, to perfonn an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figures 3 - 6 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

[0042] Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowchart, and combinations of blocks in the flowchart, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

[0043] In some embodiments, certain ones of the operations above may be modified or further amplified as described below. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations above either alone or in combination with any others among the features described herein. Referring now to Figure 3, the operations performed by a method, apparatus and computer program product of an example embodiment are illustrated from the perspective of an apparatus 10 that may be embodied by or otherwise associated with a mobile terminal. In order to provide for improved uplink control signaling, the apparatus embodied by the mobile terminal or the access point may include means, such as a processor 12 or the like, for identifying the upper bound for supportable feedback payload. See operation 20 of Figure 3. The upper bound may be a predefined value known to both the access point and the mobile terminal. Alternatively, the base station may be configured to define the upper limit of supportable feedback, such as based upon, for example, the SINR of the uplink, and to provide infonnation to the mobile terminal that either explicitly or implicitly defines the upper limit. In this regard, the explicit configuration of the mobile terminal may be based upon signalling from the access point that explicitly defines the upper limit. In contrast, the implicit configuration relies upon one or more rules and/or parameters, other than the upper limit, that are provided by the access point to the mobile terminal and from which the mobile terminal may determine the upper limit. By way of example, the upper limit may be implicitly defined by one or more transmission parameters, such as the modulation and coding scheme (MCS) configured for a recent physical uplink shared channel (PUSCH) transmission or based upon on a power headroom report (PHR) that had been recently reported to the access point.

[0044] As shown in operation 22 of Figure 3, the apparatus 10 embodied by the mobile terminal or the access point may also include means, such as a processor 12 or the like, for determining a maximum number of ACK/NAC bits that may be fed back from the mobile terminal to the access point based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the ACK/NACK bits with the CSI bits. In one embodiment, the determination of the actual number of ACK/NACK bits is also based upon the number of source routing (SR) bits to be fed back in a respective subframe. Thereafter, the apparatus embodied by the mobile terminal or the base station may also include means, such as the processor, the communications interface 16 or the like, for causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the ACK/NACK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK NACK bits. See operation 24. In an instance in which the apparatus is embodied by the mobile terminal, the mobile terminal may cause the uplink transmission of the ACK/NACK bits and the CSI bits to be supported by causing the uplink transmission of the ACK NACK bits and the CSI bits to the access point. Conversely, in an instance in which the apparatus is embodied by the access point, the access point may be configured to cause the uplink transmission of the ACK NACK bits and the CSI bits to be supported by receiving the uplink transmission of the ACK/NACK bits and the CSI bits from the mobile terminal.

[0045] Prior to the uplink transmission, however, the apparatus 10 embodied by the mobile terminal may be configured to reduce the number of ACK NACK bits that are fed back. In this regard, Figure 4 illustrates the operations performed by an apparatus embodied by a mobile terminal in accordance with one embodiment of the present invention. Although a number of the operations, e.g., operations 30 and 32, are identical to those described above in conjunction with Figure 3, the apparatus embodied by the mobile terminal of this embodiment may also include means, such as a processor 12 or the like, for reducing the number of ACK/NACK bits to be fed back in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits. See operation 34 of Figure 4. Additionally, the apparatus embodied by the mobile terminal of this embodiment may also include means, such as the processor, an interleaver or the like, for multiplexing the ACK/NACK bits, following the reduction of the ACK/NACK bits, with the CSI bits, as shown in operation 36 of Figure 4. Thereafter, the apparatus embodied by the mobile terminal may include means, such as the processor, the communications interface 16 or the like, for causing the multiplexed ACK/NACK bits and the CSI bits to be transmitted via the uplink. See operation 38.

[0046] With reference to operation 34 of Figure 4, the maximum number of ACK NACK bits may be defined in one embodiment as m_AcK.__max

ncsi, ns , coding scheme) where Lfcd max is the upper limit for supportable feedback by a mobile terminal, ncsi is the number of CSI bits, n_SR is the number of SR bits and the coding scheme is a coding scheme utilized for CSI and ACK/NACK multiplexing. In an instance in which N^^{m fonnat 3} is the number of

ACK NACK bits when PUCCH Format 3 is utilized for the transmission of ACK/NACK feedback as known by both the access point and the mobile terminal based on the TDD

configuration, the number of carriers configured and the transmission modes in each carrier, the maximum number of ACK/NACK bits may be defined as m_Ac_fc_„ma_X =min ( N^™ ^{{omM 3} , 11 ,

Lfed_max - n_Csi - n_SR) for separate coding and m_AcK._ max =min ( N ^^{CH fonnat} , Lfed max - n_Csi - n_SR) for joint coding.

[0047] In an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits, the apparatus 10 embodied by the mobile terminal, such as the processor 12, may be configured to reduce the ACK/NACK bits to be fed back in any one of various manners including spatial bundling, time domain bundling, dropping of ACK NACK bits, etc. By way of example, the ACK NACK bits may be spatially bundled such that there will be

AC /NACK bits following spatial bundling. In one embodiment in which

m_ACK__max<

a number of ACK NACK bits may be dropped from the ACK/NACK bits that result from the spatial bundling with the number of ACK/NACK bits being dropped being defined as

m_Ac _ma_X- Λ¾°^{Η f0r}™'^{3 bits}- ^The ACK NACK bits to be dropped may be selected in accordance with a predefined rule that defines a priority order for the dropping. For example, the ACK/NACK bits to be dropped may be identified, e.g., first and last, in accordance with the concatenation order of the ACK NACK bits as specified by TS 36.212 va30.

Alternatively, the ACK/NACK bits in the concatenation order defined by TS 36.212 va30 may be divided into Nd_rop groups with the im ACK NACK bits in each group being dropped. In this instance, i may be a random number determined by, for example, the identity (ID) of the mobile terminal and/or the system frame number (SFN). By relying upon a random value i, the apparatus, such as a processor, can avoid always dropping or bundling the ACK/NACK bits for the same subframe in the same carrier, thereby facilitating the frequency/time selective gain in the downlink scheduling. Once the ACK/NACK bits have been dropped, the remaining

ACK/NACK bits may be multiplexed with the CSI bits prior to causing the uplink transmission. See operations 36 and 8 of Figure 4. In order to avoid the impact to throughput and to avoid unnecessary transmissions, the access point of one embodiment may determine that the subframes and the carriers which correspond to the dropped ACK/NACK bits need not be scheduled.

[0048] As an alternative to dropping the ACK/NACK bits that remain following the spatial bundling, the ACK/NACK bits may be time domain bundled in _undie carriers so as to satisfy the ACK/NACK payload requirement. In this regard, 2xNb_undie+ (N-

where N is the number of carriers configured and M is the number of downlink subframes associated with one uplink subframe according to the TDD configuration. The apparatus 10 embodied by the mobile terminal, such as the processor 12, may select the carriers to perform the ACK NACK bundling based upon a predefined rule, such as a priority order in which the bundling begins with the Nbundie carriers configured with the highest carrier index or by bundling the N undie carriers with increasing order of carrier index started from carrier ID i wherein i is a random number determined by the ID of the mobile terminal and/or the SFN, for example.

Following the time domain bundling of the ACK/NACK bits, the resulting ACK/NACK bits may be multiplexed with the CSI bits prior to causing the uplink transmission.

[0049] As another alternative to dropping the ACK/NACK bits or performing time domain bundling, the apparatus 10 embodied by the mobile terminal, such as the processor 12, may identify only certain of the ACK NACK bits for feedback. In this regard, a scheduling set S_k may be defined by an access point that includes all or a subset of the subframes of a radio frame in all or a subset of the configured component carriers for a mobile terminal. Once the scheduling set is configured for a mobile terminal, the mobile terminal shall assume that downlink data transmissions can only be scheduled in the resources within the scheduling set. As such, the mobile terminal of this embodiment shall only generate ACK/NACK bits corresponding to the resources within the scheduling set and, as such, will only feedback the ACK/NACK bits for subframes within the scheduling set. The mobile terminal may be advised of the scheduling set by higher layer signalling that identifies the existence of the scheduling set and the pattern of the scheduling set. The scheduling set may be defined in such a manner that the number of ACK/NACK bits generated by a mobile terminal for the subframes of the scheduling set is equal or less than the maximum number of ACK NACK bits. In this embodiment, the apparatus embodied by the mobile terminal, such as the processor, may multiplex the ACK NACK bits for the subframe of the scheduling set with the CSI bits prior to causing the uplink transmission.

[0050] In addition to or instead of reducing the number of ACK/NACK bits, a method, apparatus and computer program product of an example embodiment may reduce the number of CSI bits. As shown in operation 40 of Figure 5, for example, an apparatus 10 embodied by either the mobile terminal or the access point may include means, such as the processor 12 or the like, for determining the upper limit for the supportable feedback by one mobile terminal as described above in conjunction with operation 20 of Figure 3. The apparatus embodied by the mobile terminal or the access point of this embodiment may also include means, such as a processor or the like, for determining a maximum number of CSI bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of ACK NACK bits to be fed back in the respective subframe. In one embodiment, the maximum number of CSI bits is also based upon the number of SR bits to be fed back in the respective subframe. See operation 42 of Figure 5. In one embodiment, the maximum number of CSI bits mcsi may be defined as

^{form l} - n_S ). The apparatus embodied by the mobile terminal or the access point may also include means, such as the processor, the communications interface 16 or the like, for causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits. In an instance in which the apparatus is embodied by the mobile terminal, the mobile terminal may cause the uplink transmission of the ACK/NACK bits and the CSI bits to be supported by causing the uplink transmission of the ACK/NACK bits and the CSI bits to the access point. Conversely, in an instance in which the apparatus is embodied by the access point, the access point may be configured to cause the uplink transmission of the ACKTNACK bits and the CSI bits to be supported by receiving the uplink transmission of the ACK/NACK bits and the CSI bits from the mobile terminal.

[0051 ] Prior to the uplink transmission, however, the apparatus 10 embodied by the mobile terminal may be configured to reduce the number of CSI bits that are fed back. In this regard, Figure 6 illustrates the operations performed by an apparatus embodied by a mobile terminal in accordance with one embodiment of the present invention. Although a number of the operations, e.g., operations 50 and 52, are identical to those described above in conjunction with Figure 5, the apparatus embodied by the mobile terminal of this embodiment may also include means, such as a processor 12 or the like, for reducing the number of CSI bits to be fed back in an instance in which the number of CSI bits exceeds the maximum number of CSI bits. See operation 54 of Figure 6. Additionally, the apparatus embodied by the mobile terminal of this embodiment may also include means, such as the processor, an interleaver or the like, for multiplexing the ACK NACK bits with the CSI bits, following the reduction of the CSI bits, as shown in operation 56 of Figure 6. Thereafter, the apparatus embodied by the mobile terminal may include means, such as the processor, the communications interface 16 or the like, for causing the multiplexed ACK/NACK bits and the CSI bits to be transmitted via the uplink. See operation 58.

[0052] With reference to operation 54 of Figure 6, in an instance in which the number of CSI bits exceeds the maximum number of CSI bits, a number of CSI bits may be reduced to be no greater than the maximum number of CSI bits in any one of various manners. In one

embodiment, the apparatus 10 embodied by the mobile terminal may include means, such as the processor 12 or the like, for determining if there is another periodic CSI report in the same subframe and, if so, if the other periodic CSI report has a size that is no greater than the maximum number of CSI bits. In an instance in which there is another periodic CSI report that has a size no greater than the maximum number of CSI bits, the CSI bits that exceed, in number, the other periodic CSI report may be caused to be transmitted within the same subframe instead of the CSI bits. Additionally, or alternatively, the apparatus embodied by the mobile terminal may include means, such as a processor or the like, for determining whether a predefined CSI report mode has been established in which the report size is no greater than the maximum number of CSI bits. In an instance in which a predefined CSI report mode has been established and the size of the predefined CSI report is no greater than the maximum number of CSI bits, the CSI bits may be reported in accordance with the predefined CSI report mode. Additionally, or alternatively, the apparatus embodied by the mobile terminal may include means, such as a processor or the like, for dropping a sufficient number of CSI bits such that the remaining CSI bits are no greater than the maximum number of CSI bits. Following the reduction in a number of CSI bits, the remaining CSI bits may be multiplexed with the ACK/NACK bits and then transmitted via the uplink to the access point.

[0053] Referring now to Figure 7, examples of the dropping of ACK/NACK bits for payload reduction are depicted. In these examples, the mobile terminal is presumed to have a relatively high SINR and

1 bit.

Additionally, these examples are predicated upon the use of joint coding for the multiplexing of the ACK/NACK bits with the CSI bits. As such, the number of ACK NACK bits that may be supported is mACK_max

- n_Csi - ^η _δκ) =12 bits. As such, 3

ACK/NACK bits must be dropped, e.g., 15-12. With reference to Figure 7, the set 60 of the 15 original ACK/NACK bits is shown on the left-hand side with the sets of ACK/NACK bits that are shown in the right-hand side of Figure 7 depicting three examples of ACK/NACK dropping. In the upper set 62 of ACK/NACK bits, the final 3 ACK/NACK bits are dropped. In the middle set 64 of ACK/NACK bits, the first 3 ACK/NACK bits are dropped and in the bottom set 66 of ACK/NACK bits, the ACK/NACK bits are divided into three groups and the i^th, e g., third, ACK/NACK bits in each group is dropped. As noted above, the random value i may be determined based upon the ID and/or the SFN of the mobile terminal in order to avoid dropping the same bits for mobile terminals having the same carrier configuration.

[0054] Referring now to Figure 8, two examples of ACK NACK payload reduction via bundling are provided. In this regard, the set 70 of original ACK/NACK bits is shown in the left-hand column of Figure 8 and the two examples 72, 74 of ACK NACK payload reduction are shown in the right-hand column of Figure 8. The assumption with respect to the number of bits, the SINR of the mobile terminal and the type of coding remain the same in Figure 8 as described above in conjunction with Figure 7 such that 12 ACK/NACK bits may be supported and N_bundie may be determined to be 3. In the first example 72 of the ACK/NACK payload reduction shown in the upper block of Figure 8, the three carriers having the highest carrier indices are bundled, while in the second example 74 shown in the lower of Figure 8, the three carriers beginning with carrier index i=2 are bundled. As before, the carrier index i may be based upon a random value that is determined with reference to the ID and/or the SFN of the mobile terminal so as to avoid bundling the same bits for mobile terminals having the same carrier configuration.

[0055] In regards to the reduction of the ACK/NACK bits based upon the identification of the ACK/NACK bits for subframes of a scheduling set, reference is made to Figure 9 which illustrates operations performed by an access point of this embodiment in regards to a respective mobile terminal. Since the procedure depicted in Figure 9 is specific for a mobile terminal, the access point may separately implement the procedure for each of a plurality of mobile terminals. As shown in operation 80 of Figure 9, the apparatus 10 embodied by the access point, such as the processor 12 or the like, may initially determine if there is a need to multiplex the ACK/NACK bits with the periodic CSI bits. An access point may determine that a scheduling set should be defined so as to avoid periodic CSI dropping and only introduces an acceptable scheduling restriction for a respective mobile terminal. Conversely, a mobile terminal may determine that a scheduling set is not needed in some instances since the scheduling restriction may compromise the gain otherwise achieved by reducing the CSI dropping. In an instance in which the

ACK/NACK bits are not required to be multiplexed with the periodic CSI bits, the apparatus embodied by the access point, such as a processor, the communications interface 16 or the like, may configure the mobile terminal to drop the periodic CSI bits in instances in which the periodic CSI bits collide with the ACK NACK bits. See operation 82.

[0056] If the ACK NACK bits are to be multiplexed with the periodic CSI bits, however, the apparatus 10 embodied by the access point, such as a processor 12, may determine if the number of ACK NACK bits without any restriction N_ACKJ exceeds a threshold _threshold. See operation 84. By way of example, the number N_ACK_1 of ACK/NACK bits without any restriction, in an instance in which each downlink subframe on each component carrier has one ACK/NACK bit, equals N_CC*N_SF where N_CC is the number of configured component earners and N__SF is the number of downlink subframes for which the ACK NACK bits have to be fed back in the relevant uplink subframe based on the hybrid automatic repeat request (HARQ) timing. Additionally, M_threshold is a threshold which may be predefined. For example,

M_threshold may be 11 bits, which is the maximum payload size that may be supported by one code block of a dual RM encoder. In an instance in which N_ACK_1 does not exceed

Mjhreshold, the apparatus embodied by the access point, such as a processor, communications interface 16 or the like, may configure the mobile terminal to multiplex periodic CSI bits with ACK/NACK bits. See operation 86 of Figure 9. However, in an instance in which N_ACK_1 exceeds M threshold, the apparatus embodied by the access point, such as a processor, may determine whether a scheduling set is defined for the mobile terminal. See operation 88.

[0057] In an instance in which the apparatus 10 embodied by the access point determines that a scheduling set is not to be defined for the mobile terminal, the apparatus embodied by the access point, such as the processor 12, the communications interface 16 or the like, may configure the mobile terminal to drop periodic CSI bits that collide with ACK/NACK bits. See opration 90. However, in an instance in which the apparatus embodied by the access point determines that a scheduling set is to be defined for the mobile terminal, the apparatus embodied by the access point, such as the processor or the like, may configure the scheduling set for the mobile terminal and may, in turn, configure the mobile terminal to multiplex the periodic CSI bits with the ACK/NACK bits for the subframes of the scheduling set. See operation 92 of Figure 9. Once the scheduling set is defined, the mobile terminal and the access point may operate in accordance with a predefined rule that defines how the ACK/NACK bits are arranged. For example, the ACK NACK bits may be mapped to the bit sequence first in the time direction and then in the component carrier direction.

[0058] In one embodiment, an access point may configure the scheduling sets for different mobile terminals such that the mobile terminals are grouped and restricted to certain resources. As such, it may be possible to maintain a multi-user scheduling gain, particularly in instances in which there are a moderate or large number of mobile terminals. Additionally, since the component carrier configuration is specific to a mobile terminal, all of the mobile terminals may not see the same restriction. Since the mobile terminal will not generate ACK/NACK bits for resources that are not included within the scheduling set, the mobile tenninal may skip the blind detection of downlink grants for the corresponding resources that are outside of the scheduling set, thereby conserving power of the mobile terminal

[0059] By way of example, Figure 10 illustrates scheduling sets 100, 102 for two mobile terminals that operate in accordance with TDD configuration number 4 and in which

N_ACK=11. Additionally, Figure 11 illustrates the scheduling sets 104, 106 for two mobile terminals having TDD configuration number 5 and again with _ACK=l 1. In the illustrated examples of Figures 10 and 11, the shaded blocks represent the subframes that are included within the scheduling set. In either instance, the number of ACK/NAC bits generated by a mobile terminal in accordance with the scheduling set does not exceed the predefined threshold, such as 1 1 in the illustrated embodiment.

[0060] By way of example with respect to the reduction of CSI bits, the number of CSI bits that may be supported is defined as mcsi=min (ncsi, Lfed_max - N™ ^{CH fomiat3} - sR)=5 bits. In an instance in which no other CSI report occurs within the same subframe, the CSI report may resort to a fallback mode which, in one embodiment, is a wideband CSI report with four bits. By resorting to the fallback mode with a wideband CSI report having four bits, the upper limit of the feedback payload may be satisfied, e.g. , 4 < 5, such that the wideband CSI report may be provided together with the ACK/NACK bits and the SR bits within the same subframe.

[0061 ] By deteiraining the maximum payload size and then adaptively reducing the

ACK/NACK bits and/or the CSI bits prior to provision of the uplink control signaling, improved uplink control signaling may be provided with less impact upon the downlink throughput.

Indeed, the method, apparatus and computer program product of one embodiment may target maximum utilization of the uplink feedback capability so as to improve both the mobile terminal and system performance.

[0062] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

What is Claimed is:

1. A method comprising:

determining a maximum number of acknowledgement (ACK)/negative acknowledgement (NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the

ACK/NACK bits with channel status information (CSI) bits; and

causing an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits.

2. A method according to Claim 1 further comprising:

reducing the ACK NACK bits to be fed back in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits; and

multiplexing the ACK/NACK bits, following reduction, with the CSI bits prior to causing the uplink transmission.

3. A method according to Claims 1 or 2 wherein determining the maximum number of ACK/NACK bits is also based upon a number of sounding reference (SR) bits to be fed back in a respective subframe.

4. A method according to any one of Claims 1 to 3 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

5. A method according to any one of Claims 1 to 3 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon one or more transmission parameters.

6. A method according to any one of Claims 2 to 5 wherein reducing the ACK/NACK bits comprises spatial bundling the ACK NACK bits.

7. A method according to any one of Claims 2 to 6 wherein reducing the ACK/NACK bits comprises dropping one or more ACK/NACK bits in accordance with a priority order such that the ACK NACK bits remaining after the dropping no longer exceeds the maximum number of ACK/NACK bits.

8. A method according to Claim 7 wherein the priority order is based upon a

concatenation order of the one or more ACK NACK bits.

9. A method according to Claim 7 wherein the priority order begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

10. A method according to any one of Claims 2 to 6 wherein reducing the ACK NACK bits comprises time domain bundling the ACK/NACK bits in accordance with a predefined rule.

11. A method according to Claim 10 wherein the predefined rule is based u on a priority order of a plurality of carriers.

12. A method according to Claim 10 wherein the predefined rule is based upon time domain bundling that begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

13. A method according to any one of Claims 2 to 6 wherein reducing the ACK NACK bits comprises identifying the ACK/NACK bits for subframes of a scheduling set configured by a base station that includes at least some of the subframes of a radio frame in at least some of the component carriers for a mobile terminal.

14. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the processor, cause the apparatus to at least: determine a maximum number of acknowledgement (ACK)/negative acknowledgement (NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the

ACK NACK bits with channel status information (CSI) bits; and

cause an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the ACK/NAK bits in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK NACK bits.

15. An apparatus according to Claim 14 wherein the at least one memory and the computer program code are further configured to, with the processor, cause the apparatus to: reduce the ACK NACK bits to be fed back in an instance in which the number of ACK NACK bits exceeds the maximum number of ACK/NACK bits; and

multiplex the ACK/NACK bits, following reduction, with the CSI bits prior to causing the uplink transmission.

16. An apparatus according to Claims 14 or 15 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to determine the maximum number of ACK/NACK bits based also upon a number of sounding reference (SR) bits to be fed back in a respective subframe.

17. An apparatus according to any one of Claims 14 to 16 wherein the at least one memory and the computer program code are further configured to, with the processor, cause the apparatus to configure the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

18. An apparatus according to any one of Claims 14 to 16 wherein the at least one memory and the computer program code are further configured to, with the processor, cause the apparatus to configure the maximum payload that the mobile temiinal is capable of feeding back based upon one or more transmission parameters.

19. An apparatus according to any one of Claims 15 to 18 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the ACK/NACK bits by spatial bundling the ACK/NACK bits.

20. An apparatus according to any one of Claims 15 to 19 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the ACK NACK bits by dropping one or more ACK NACK bits in accordance with a priority order such that the ACK NACK bits remaining after the dropping no longer exceeds the maximum number of ACK NACK bits.

21. An apparatus according to Claim 20 wherein the priority order is based upon a concatenation order of the one or more ACK NACK bits.

22. An apparatus according to Claim 20 wherein the priority order begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

23. An apparatus according to any one of Claims 15 to 19 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the ACK/NACK bits by time domain bundling the ACK/NACK bits in accordance with a predefined rule.

24. An apparatus according to Claim 23 wherein the predefined rule is based upon a priority order of a plurality of carriers.

25. An apparatus according to Claim 23 wherein the predefined rule is based upon time domain bundling that begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

26. An apparatus according to any one of Claims 1 to 19 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the ACK/NACK bits by identifying the ACK NACK bits for subframes of a scheduling set configured by a base station that includes at least some of the subframes of a radio frame in at least some of the component carriers for a mobile terminal.

27. An apparatus according to any one of Claims 14 to 26 wherein the apparatus is embodied by a mobile telephone.

28. An apparatus according to any one of Claims 14 to 27 further comprising user interface circuitry configured to facilitate user control of at least some functions of the mobile telephone through use of a display.

29. An apparatus according to Claims 14 or 16 tol8 wherein the apparatus is embodied by a base station.

30. A computer program product comprising at least one non-transitory computer- readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions comprising program instructions configured to:

determine a maximum number of acknowledgement (ACK)/negative acknowledgement (NACK) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a coding scheme for multiplexing the

ACK/NACK bits with channel status information (CSI) bits; and

31. A computer program product according to Claim 30 wherein the computer-readable program instructions further comprise program instructions configured to:

reduce the ACK/NACK bits to be fed back in an instance in which the number of ACK/NACK bits exceeds the maximum number of ACK/NACK bits; and

32. A computer program product according to Claims 30 or 31 wherein the program instructions configured to determine the maximum number of AC /NAC bits is based also upon a number of sounding reference (S ) bits to be fed back in a respective subframe.

33. A computer program product according to any one of Claims 30 to 32 wherein the computer-readable program instructions further comprise program instructions configured to configure the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

34. A computer program product according to any one of Claims 30 to 32 wherein the computer-readable program instructions further comprise program instructions configured to configure the maximum payload that the mobile terminal is capable of feeding back based upon one or more transmission parameters.

35. A computer program product according to Claims 31 or 34 wherein the program instructions configured to reduce the ACK/NACK bits comprise spatially bundle the

ACK/NACK bits.

36. A computer program product according to any one of Claims 31 to 35 wherein the program instructions configured to reduce the ACK/NACK bits comprise program instructions configured to drop one or more ACK/NACK bits in accordance with a priority order such that the ACK NACK bits remaining after the dropping no longer exceeds the maximum number of ACK/NACK bits.

37. A computer program product according to Claim 36 wherein the priority order is based upon a concatenation order of the one or more ACK/NACK bits.

38. A computer program product according to Claim 36 wherein the priority order begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

39. A computer program product according to any one of Claims 31 to 35 wherein the program instructions configured to reduce the ACK/NACK bits comprise program instructions configured to time domain bundle the ACK/NACK bits in accordance with a predefined rule.

40. A computer program product according to Claim 39 wherein the predefined rule is based upon a priority order of a plurality of carriers.

41. A computer program product according to Claim 39 wherein the predefined rule is based upon time domain bundling that begins at a random position that is based upon at least one of an identity (ID) of the mobile terminal or a system frame number (SFN).

42. A computer program product according to any one of Claims 31 to 35 wherein the program instructions configured to reduce the ACK NACK bits comprise program instructions configured to identify the ACK NACK bits for subframes of a scheduling set configured by a base station that includes at least some of the subframes of a radio frame in at least some of the component carriers for a mobile terminal.

43. A method comprising:

determining a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative acknowledgement (NACK) bits to be fed back in a respective subframe; and

causing an uplink transmission of the ACK NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

44. A method according to Claim 43 further comprising:

reducing the CSI bits to be fed back in an instance in which the number of CSI bits exceeds the maximum number of CSI bits; and

multiplexing the CSI bits, following reduction, with the ACK/NACK bits.

45. A method according to Claims 43 or 44 wherein determining the maximum number of CSI bits is also based upon a number of sounding reference (SR) bits to be fed back in the respective subframe.

46. A method according to any one of Claims 43 to 45 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

47. A method according to any one of Claims 43 to 45 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon one or more transmission parameters.

48. A method according to any one of Claims 43 to 47 wherein determining the maximum number of CSI bits mcsi as nicsi⁼mm (ncsi, Lfed max - N_A/ ^{~ nsR}^ ^wnere^^{n n}csi is ^a number of CSI bits to be fed back prior to reduction, L_fed_max is the maximum payload, N_A/N is the number of ACK/NACK bits to be fed back in the respective subframe and _SR is a number of SR bits to be fed back.

49. A method according to any one of Claims 43 to 47 wherein reducing the CSI bits comprises:

determining whether another periodic CSI report occurs in the respective subframe that has a size no greater than the maximum number of CSI bits; and

causing the other periodic CSI report to be fed back instead of the CSI bits in an instance in which the size of the other CSI report is no greater than the maximum number of CSI bits.

50. A method according to any one of Claims 43 to 47 wherein reducing the CSI bits comprises replacing the CSI bits to be fed back with a predefined CSI report in an instance in which a size of the predefined CSI report is no greater than the maximum number of CSI bits.

51. A method according to any one of Claims 43 to 47 wherein reducing the CSI bits comprises dropping the CSI bits from the respective subframe.

52. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the processor, cause the apparatus to at least:

determine a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (AC )/negative acknowledgement (NACK) bits to be fed back in a respective subframe; and

cause an uplink transmission of the ACK/NACK bits and the CSI bits to be supported following reduction of the CSI bits in an instance in which the number of CSI bits exceeds the maximum number of CSI bits.

53. An apparatus according to Claim 52 wherein the at least one memory and the computer program code are further configured to, with the processor, cause the apparatus to: reduce the CSI bits to be fed back in an instance in which the number of CSI bits exceeds the maximum number of CSI bits; and

multiplex the CSI bits, following reduction, with the ACK/NACK bits.

54. An apparatus according to Claims 52 or 53 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to determine the maximum number of CSI bits based also upon a number of sounding reference (SR) bits to be fed back in the respective subframe.

55. An apparatus according to any one of Claims 52 to 54 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to configure the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

56. An apparatus according to any one of Claims 52 to 54 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to configure the maximum payload that the mobile terminal is capable of feeding back based upon one or more transmission parameters.

57. An apparatus according to any one of Claims 52 to 56 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to determine the maximum number of CSI bits mcsi as mcs min (ncs Lfed_m„x -

IISR) wherein ncsi is a number of CSI bits to be fed back prior to reduction, Lf_etj_max is the maximum payload, NA/N is the number of ACK NACK bits to be fed back in the respective subframe and ≤R is a number of SR bits to be fed back.

58. An apparatus according to any one of Claims 52 to 56 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the CSI bits by:

59. An apparatus according to any one of Claims 52 to 56 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the CSI bits by replacing the CSI bits to be fed back with a predefined CSI report in an instance in which a size of the predefined CSI report is no greater than the maximum number of CSI bits.

60. An apparatus according to any one of Claims 52 to 56 wherein the at least one memory and the computer program code are configured to, with the processor, cause the apparatus to reduce the CSI bits by dropping the CSI bits from the respective subframe.

61. An apparatus according to any one of Claims 52 to 60 wherein the apparatus is embodied by a mobile telephone.

62. An apparatus according to any one of Claims 52 to 61 further comprising user interface circuitry configured to facilitate user control of at least some functions of the mobile telephone through use of a display.

63. An apparatus according to Claims 52 or 54 to 56 wherein the apparatus is embodied by a base station.

64. A computer program product comprising at least one non-transitory computer- readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions comprising program instructions configured to:

determine a maximum number of channel status information (CSI) bits based upon a maximum payload that a mobile terminal is capable of feeding back in one uplink subframe and further based upon a number of acknowledgement (ACK)/negative acknowledgement (NACK) bits to be fed back in a respective subframe; and

65. A computer program product according to Claim 64 wherein the computer-readable program instructions further comprise program instructions configured to:

reduce the CSI bits to be fed back in an instance in which the number of CSI bits exceeds the maximum number of CSI bits; and

multiplex the CSI bits, following reduction, with the ACK/NACK bits.

66. A computer program product according to Claims 64 or 65 wherein the program instructions configured to determine the maximum number of CSI bits are based also upon a number of sounding reference (SR.) bits to be fed back in the respective subframe.

67. A computer program product according to any one of Claims 64 to 66 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon signaling from an access point.

68. A computer program product according to any one of Claims 64 to 66 further comprising configuring the maximum payload that the mobile terminal is capable of feeding back based upon one or more transmission parameters.

69. A computer program product according to any one of Claims 64 to 68 wherein the program instructions are configured to determine the maximum number of CSI bits m_Csi as m_Csi=min (ncsi, Lfed_max - N - ^SR) wherein n_Csi is a number of CSI bits to be fed back prior to reduction, Lf_ed _max is the maximum payload, NA N is the number of ACK/NACK bits to be fed back in the respective subframe and US_R is a number of SR bits to be fed back.

70. A computer program product according to any one of Claims 64 to 68 wherein the program instructions ae configured to reducing the CSI bits by:

71. A computer program product according to any one of Claims 64 to 68 wherein the program instructions configured to reduce the CSI bits comprise program instructions configured to replace the CSI bits to be fed back with a predefined CSI report in an instance in which a size of the predefined CSI report is no greater than the maximum number of CSI bits.

72. A computer program product according to any one of Claims 64 to 68 wherein the program instructions configured to reduce the CSI bits comprise program instructions configured to drop the CSI bits from the respective subframe.