System and method for allocating transmission resources

A method for wirelessly transmitting data and control information using a plurality of transmission layers includes determining a number of bits in one or more user data codewords to be transmitted during a subframe and calculating a number of control vector symbols to allocate to control information during the subframe. The number of control vector symbols is calculated based at least in part on the number of bits in the one or more user data codewords to be transmitted during the subframe and an estimate of the number of vector symbols onto which the one or more user data codewords will be mapped. The estimate of the number of vector symbols depends, at least in part, on the number of control vector symbols to be allocated to control information. The method also includes mapping one or more control codewords to the calculated number of control vector symbols and transmitting vector symbols carrying the one or more user data codewords and the one or more control codewords over the plurality of transmission layers during the subframe.

TECHNICAL FIELD OF THE INVENTION

This disclosure relates in general to wireless communication and, more particularly, to resource allocation for multi-antenna transmissions.

BACKGROUND OF THE INVENTION

Multi-antenna transmission techniques can significantly increase the data rates and reliability of wireless communication systems, especially in systems where the transmitter and the receiver are both equipped with multiple antennas to permit the use of multiple-input multiple-output (MIMO) transmission techniques. Advanced communication standards such as Long Term Evolution (LTE) Advanced utilize MIMO transmission techniques that may permit data to be transmitted over multiple different spatially-multiplexed channels simultaneously, thereby significantly increasing data throughput.

While MIMO transmission techniques can significantly increase throughput, such techniques can greatly increase the complexity of managing radio channels. Additionally, many advanced communication technologies, such as LTE, rely on a substantial amount of control signaling to optimize the configuration of transmitting devices and their use of the shared radio channel. Because of the increased amount of control signaling in advanced communication technologies, it is often necessary for user data and control signaling to share transmission resources. For example, in LTE systems, control signaling and user data are, in certain situations, multiplexed by user equipment (“UE”) for transmission over a physical uplink shared channel (“PUSCH”).

However, conventional solutions for allocating transmission resources are designed for use with single layer transmission schemes in which only a single codeword of user data is transmitted at a time. Additionally, conventional solutions may not consider the size of the control information to be transmitted, when determining the number of vector symbols to allocate to each bit of control information. As a result, such resource allocation solutions fail to provide optimal allocation of transmission resources between control information and user data when MIMO techniques are being utilised to transmit data on multiple layers simultaneously, especially when a large amount of control information must be transmitted.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, certain disadvantages and problems associated with wireless communication have been substantially reduced or eliminated. In particular, certain devices and techniques for allocating transmission resources between control information and user data are described.

In accordance with one embodiment of the present disclosure, a method for wirelessly transmitting data and control information using a plurality of transmission layers includes determining a number of bits in one or more user data codewords to be transmitted during a subframe and calculating a number of control vector symbols to allocate to control information during the subframe. The number of control vector symbols is calculated based at least in part on the number of bits in the one or more user data codewords to be transmitted during the subframe and an estimate of the number of vector symbols onto which the one or more user data codewords will be mapped. The estimate of the number of vector symbols depends, at least in part, on the number of control vector symbols to be allocated to control information. The method also includes mapping one or more control codewords to the calculated number of control vector symbols and transmitting vector symbols carrying the one or more user data codewords and the one or more control codewords over the plurality of transmission layers during the subframe.

In accordance with another embodiment of the present disclosure, a method for receiving user data and control information transmitted wirelessly over a plurality of transmission layers includes receiving a plurality of vector symbols over a plurality of transmission layers. The method also includes determining a number of bits in one or more user data codewords carried by the vector symbols and calculating a number of control vector symbols that have been allocated to control information during the subframe. The number of control vector symbols is calculated based at least in part on the number of bits in the one or more user data codewords during the subframe and an estimate of the number of vector symbols onto which the one or more user data codewords will be mapped. The estimate of the number of vector symbols depends, at least in part, on the number of control vector symbols to be allocated to control information. The method also includes decoding the received vector symbols based on the calculated number of control vector symbols.

Additional embodiments include apparatuses capable of implementing the above methods and/or variations thereof.

Important technical advantages of certain embodiments of the present invention include reducing the overhead associated with transmitting control signaling by matching the allocation to the quality of the channel indicated by the payloads of the data codewords. Particular embodiments may provide additional benefits by accounting for the amount of control information to be transmitted when determining how much transmission resources to use in transmitting each bit of control information. Other advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a functional block diagram illustrating a particular embodiment of a multi-antenna transmitter100. In particular,FIG. 1shows a transmitter100configured to multiplex certain control signaling with user data for transmission over a single radio channel. The illustrated embodiment of transmitter100includes a splitter102, a plurality of channel interleavers104, a plurality of scramblers106, a plurality of symbol modulators108, a layer mapper110, and a carrier modulator112. Transmitter100allocates transmission resources to control signaling on multiple transmission layers based on an estimate of the quality of the radio channel over which transmitter100will transmit. As described further below, particular embodiments of transmitter100reduce the overhead for transmitted control information by using an estimate of the data payloads of multiple layers and/or codewords as a measure of the channel quality.

Control signaling can have a critical impact on the performance of wireless communication systems. As used herein, “control signaling” and “control information” refers to any information communicated between components for purposes of establishing communication, any parameters to be used by one or both of the components in communicating with one another (e.g., parameters relating to modulation, encoding schemes, antenna configurations), any information indicating receipt or non-receipt of transmissions and/or any other form of control information. For example, in LTE systems, control signaling in the uplink direction includes, for example, Hybrid Automatic Repeat reQuest (HARQ) Acknowledgments/Negative Acknowledgements (ACK/NAKs), precoder matrix indicators (PMIs), rank indicators (RIs), and channel quality indicators (CQIs), which are all used by the eNodeB to get confirmation of successful reception of transport blocks or to improve the performance of downlink transmissions. Although control signaling is often transmitted on separate control channels, such as the physical uplink control channel (PUCCH) in LTE, it may be beneficial or necessary to transmit control signaling on the same channel as other data.

For example, in LTE systems, when a periodic PUCCH allocation coincides with a scheduling grant for a user equipment (UE) to transmit user data, the user data and control signaling share transmission resources to preserve the single-carrier property of the discrete Fourier transform, spread orthogonal frequency-division multiplexing (DFTS-OFDM) transmission techniques used by LTE UEs. Furthermore, when a UE receives a scheduling grant to transmit data on the physical uplink shared channel (PUSCH), it typically receives information from the eNodeB related to the characteristics of the uplink radio propagation channel and other parameters that can be used to improve the efficiency of PUSCH transmissions. Such information may include modulation and coding scheme (MCS) indicators as well as, for UEs capable of using multiple transmission antennas, PMIs or RIs. As a result, UEs may be able to use this information to optimize PUSCH transmissions for the radio channel, thereby increasing the amount of data that can be transmitted for a given set of transmission resources. Thus, by multiplexing control signaling with the user data transmitted on PUSCH, a UE can support significantly larger control payloads than when transmitting control signaling by itself on PUCCH.

It may be possible to multiplex control signaling and user data by simply dedicating a set amount of the time-domain transmission resources to control information and then perform carrier modulation and precoding of the control signaling along with the data. In this way control and data are multiplexed and transmitted in parallel on all sub-carriers. For example, in LTE Release 8, DFTS-OFDM symbols are formed from a predetermined number of information vector symbols. As used herein, a “vector symbol” may represent any collection of information that includes an information element associated with each transmission layer over which the information is to be transmitted. Assuming a normal cyclic prefix length, fourteen of these DFTS-OFDM symbols can be transmitted in each uplink subframe. A predetermined number and distribution of these symbols are used to transmit various types of control signaling and the remaining symbols may be used to transmit user data.

Since control signaling and user data may each be associated with different block error-rate requirements, control signaling is often encoded separately and using a different encoding scheme from user data. For example, user data is often encoded with turbo codes or low-density parity-check (LDPC) codes that are highly efficient for longer block lengths (i.e., larger blocks of information bits). Control signaling that uses only a small amount of information bits, such as HARQ ACK/NAK signaling or rank indicators, is often most efficiently encoded using a block code. For medium-sized control signaling, such as larger size CQI reports, a convolutional code (possibly tail biting) often provides the best performance. Consequently, fixed or predetermined allocations of transmission resources to control signaling and user data can lead to inefficient use of such resources as the optimal resource allocation will often depend on numerous factors, including the channel quality, the type of control signaling, and various other considerations.

The use of multiple transmit antennas can further complicate the allocation of transmission resources between control signaling and user data when the two types of information are multiplexed together on a common channel. When MIMO techniques are used to simultaneously transmit multiple data codewords in parallel, control signaling may be transmitted on multiple different codewords and/or layers of the transmission scheme. The optimal allocation of resources in such situations may differ from the optimal allocation under the same circumstances when a single transmission antenna is used. Moreover, the multiple-antenna technique used for control signaling may be different from that used for user data. Control signaling is often encoded for maximum robustness (e.g., with maximum transmission diversity) rather than for maximum throughput. By contrast, user data is often combined with a retransmission mechanism that allows for more throughput-aggressive multiple-antenna encoding techniques. Thus, if transmitter100has information indicating the supported payload of user data, transmitter100may not be able to assume the supported payload for control signaling is the same when determining the optimal allocation of transmission resources for control signaling. For example, the supported peak spectral efficiency of the encoded user data may be significantly larger than the supported peak spectral efficiency of the encoded control signaling.

In many circumstances, it may be desirable to determine the amount of transmission resources to use for each bit of control signaling based on the quality of the channel over which the multiplexed control signaling will be transmitted. As part of this process, transmitter100may estimate an inverse spectral efficiency for the user data to be transmitted, based on the data payloads of one or more of the user control codewords to be transmitted, and use this estimate to determine the amount of transmission resources to use for each bit of control signaling. In such situations, it may be acceptable for transmitter100to determine the amount of transmission resources to devote to each bit of control signaling using an estimated spectral efficiency for user data without accounting for the fact that some of the transmission resources will ultimately be allocated to control signaling.

While this manner of allocating may be acceptable in many situations, the impact that neglecting the control signaling has on this estimate can become significant when a large amount of control signaling must be transmitted. Consequently, the effectiveness of the resulting allocation may be greatly diminished. Specifically, this may result in an extremely pessimistic estimate of the inverse spectral efficiency for user data, causing transmission resources to be significantly over-allocated to control signaling. The result may be especially detrimental as the amount of control signaling increases to satisfy the requirements of advanced communication technologies, such as LTE-Advanced. As the amount of control signaling increases, control overhead may, in effect, grow approximately quadratic with the control payload, rather than linearly.

To address this problem, particular embodiments of transmitter100determine an allocation of transmission resources per bit of control codeword120that takes into consideration the amount of control signaling to be transmitted under the allocation. More specifically, particular embodiments of transmitter100estimate the inverse spectral efficiency supported by the current multi-layer encoding scheme to determine an appropriate allocation of transmission resources between user data and control signaling. As part of estimating the spectral efficiency, transmitter100estimates the amount of transmission resources to be allocated to user data, and in doing so, considers the amount of transmission resources that transmitter100would allocate to control signaling given the estimated inverse spectral efficiency that would result in actuality from this user data allocation. Transmitter100may then transmit the relevant control signaling using an amount of transmission resources that corresponds to this estimated spectral efficiency.

Turning to the example embodiment illustrated byFIG. 1, transmitter100, in operation, generates or receives control codewords and data codewords (represented, inFIG. 1, by control codeword120and data codewords122aand122b, respectively) for transmission to a receiver over a radio channel. To permit multiplexing of control codewords120and data codewords122over a common channel, splitter102splits control codeword120for use by multiple channel interleavers104. Splitter102may split control codeword120in any appropriate manner between channel interleavers104, outputting a complete copy or some suitable portion on each datapath. As one example, splitter102may split control codeword120for use in the multiple datapaths by replicating control codeword120on both datapaths, outputting a complete copy of control codeword120to each channel interleaver104. As another example, splitter102may split control codeword120by performing serial-to-parallel conversion of control codeword120, outputting a unique portion of control codeword120to each channel interleaver104.

Channel interleavers104each interleave a data codeword122with control codeword120(a complete copy of control codeword120, a particular portion of control codeword120, or some combination of both). Channel interleavers104may be configured to interleave data codewords122and control codeword120so that layer mapper110will map them to vector symbols in a desired manner. The interleaved outputs of channel interleavers104are then scrambled by scramblers106and modulated by symbol modulators108.

The symbols output by symbol modulators108are mapped to transmission layers by layer mapper110. Layer mapper110outputs a series of vector symbols124that are provided to carrier modulator112. As an example, for embodiments of transmitter100that support LTE, each vector symbol124may represent an associated group of modulation symbols that are to be transmitted simultaneously on different transmission layers. Each modulation symbol in a particular vector symbol124is associated with a specific layer over which that modulation symbol will be transmitted.

After layer mapper110maps the received symbols into vector symbols124, carrier modulator112modulates information from the resulting vector symbols124onto a plurality of radiofrequency (RF) subcarrier signals. Depending on the communication technologies supported by transmitter100, carrier modulator112may also process the vector symbols124to prepare them for transmission, such as by precoding vector symbols124. The operation of an example embodiment of carrier modulator112for LTE implementations is described in greater detail below with respect toFIG. 2. After any appropriate processing, carrier modulator112then transmits the modulated subcarriers over a plurality of transmission antennas114.

As explained above, proper allocation of transmission resources to control signaling and user data may have a significant impact on the performance of transmitter100. In particular embodiments, this allocation of transmission resources is reflected in the number of vector symbols124transmitter100uses to transmit control codewords120(such vector symbols referred to herein as “control vector symbols”). Transmitter100may determine the number of vector symbols124to use for a particular control codeword120based on a measure of the quality of the channel or some other indication of the likelihood that the receiver will erroneously detect control codeword120after being transmitted over the radio channel.

In particular, certain embodiments of transmitter100may use the data payload of the multiple layers or codewords that will be used to transmit control codewords120(or a subset of such layers/codewords) to estimate the inverse spectral efficiency currently supported by the multi-layer encoding scheme to be used. In particular embodiments, transmitter100determines a data payload for the multiple layers or codewords based on information included in a scheduling grant received by transmitter. Such information may include any suitable information from which transmitter100can directly or indirectly determine the data payload to be used for the multiple layers or codewords. For example, transmitter100may receive a scheduling grant that includes a total resource allocation, a coding rate, and a modulation scheme, and may determine from this information, the data payload of the transmission layers transmitter100will be using for the transmission. Using the determined payload, transmitter100may then determine an estimate of the spectral efficiency for the current allocation.

Additionally, the estimate of the inverse spectral efficiency used by transmitter100to determine the number of control vector symbols124may itself depend, in turn, on the number of control vector symbols124that would result from the estimate. Transmitter100may determine the inverse spectral efficiency estimate and the corresponding number of control vector symbols124in any suitable manner. In particular embodiments, transmitter100may determine the number of control vector symbols124based on a value Q′ that is determined recursively, using a formula of the form:

Q′=f⁡(Q^data⁡(Q′),∑r=0Cn,0-1⁢K0,r,5,∑r=0Cn,NCW-1⁢KNCW-1,r,βoffset,O)⁢⁢⁢where⁢⁢⁢f⁡(Q^data⁡(Q′⁢),∑r=0Cn-1⁢K0,r,5,∑r=0Cn-1⁢KNCW-1,r)Equation⁢⁢(1)
represents a function that, given an estimate of the number of vector symbols124that will be allocated to transmitting user data codewords122({circumflex over (Q)}data(Q′)) (such vector symbols referred to herein as “user data vector symbols”) maps the data payloads

(∑r=0Cn-1⁢Kn,r)
of each of the NCWuser data codewords122into an estimate of the number of vector symbols124to be used for each bit of the control codewords120to be transmitted during the subframe. In Equation (1), Kq,rrepresents the number of bits in an r-th code block of a q-th codeword of user data to be transmitted during the subframe with r≧1 and q≧1, Cn,mis a number of code blocks in an m-th codeword of user data with m≧1, NCWis a number of codewords of control information to be transmitted during the subframe, O is a number of bits in one or more control codewords120to be transmitted during the subframe. If cyclic redundancy check (CRC) bits are used with user data codewords and/or control codewords, the relevant values for Kq,rand/or O may include any CRC bits in their totals. As suggested by the designated ranges of r (r≧1) and q (q≧1) for the above formula, transmitter100may perform this calculation using one or more code blocks from one or more codewords of user data. Because, in Equation (1), the value of {circumflex over (Q)}datadepends on the value of Q′, the inverse spectral efficiency utilized to determine the allocation of control vector symbols124will be based on the number of control vector symbols124that would actually result from such an allocation (or an improved estimate thereof).

In certain embodiments, transmitter100may specifically use a formulation of {circumflex over (Q)}data(Q′) that can be expressed in terms of a value (Qall) indicating the total amount of transmission resources allocated to transmitter100. The size and units of Qalldepends on the manner in which the access network allocates transmission resources to transmitter100. For instance, transmitter100may use a value of Qall=N×M, where N is the total number of vector symbols available to transmitter100for transmitting control information and user data in the relevant subframe (e.g. NsymbPUSCH-initialin certain LTE embodiments), and M is a total number of subcarriers available to transmitter100during the relevant subframe (e.g., MsePUSCH-initial). In such embodiments, transmitter100may specifically use a formulation of {circumflex over (Q)}data(Q′) that can be expressed as: {circumflex over (Q)}data=Qall−αQ′, for some value of α, including but not limited to α=1.

As shown by Equation 1, transmitter100may utilize a configurable offset (βoffsetPUSCH) to scale or otherwise adjust the estimated number of vector symbols124to be used for control signaling. (Note that in this context there is a linear ambiguity between ƒ(·) and βoffsetPUSCH, in that a constant scaling can be absorbed either by ƒ(·) or by βoffsetPUSCH; that is, the pair └ƒ(·),βoffsetPUSCH┘, is considered equivalent to the pair └{tilde over (ƒ)}(·),{tilde over (β)}offsetPUSCH┘, where

f~⁡(·)=f⁡(·)c,
and {tilde over (β)}offsetPUSCH=c·βoffsetPUSCH.) Additionally, as also indicated by Equation 1, particular embodiments of transmitter100may use a maximum threshold (Q′max) to limit the maximum amount of transmission resources that may be allocated to control codewords120for the subframe. Furthermore, as indicated by the ┌ ┐ operator in Equation 1, particular embodiments of transmitter100may round, truncate, or otherwise map the estimated (or scaled) number of control vector symbols124to an integer value, such as by applying the ceiling operator to the scaled value as shown.

Because of the interdependency between the number of control vector symbols124and the estimated inverse spectral efficiency for user data (as reflected by the number of vector symbols124allocated to user data), particular embodiments of transmitter100may be unable to determine the number of control vector symbols124using a closed-form expression. As a result, particular embodiments of transmitter100may determine the number of control vector symbols124using a recursive algorithm to solve Equation (1). Alternatively, such embodiments of transmitter100may determine a numerical value for Q′ and, based on Q′, a number of control vector symbols124to allocate, transmitter100by solving a modified version of Equation (1) and determining the smallest Q′ for which:

Alternative embodiments of transmitter100may determine the number of control vector symbols124to allocate using a value of Q′ defined by a closed-form expression that takes the control overhead into account. This closed-form expression may represent any suitable expression in which the estimated number of user data vector symbols124to be allocated has a relationship to the number of control vector symbols124to be allocated that can be entirely expressed in terms of other values.

As one example of such a closed-form expression, particular embodiments of transmitter100may use an estimate for the number of user data vector symbols124whose dependency on the number of control vector symbols124to be allocated can be expressed in terms of the size (O) of the control codewords120to be transmitted. For example, transmitter100may use a version of ƒ( ) in which:

f(Q^data⁡(Q′)·∑r=0Cn,0-1⁢K0,r,5,∑r=0Cn,NCW-1⁢KNCW-1,r,βoffsetPUSCH,O)=Qall-Q′g(∑r=0Cn,0-1⁢K0,r,5,∑r=0Cn,NCW-1⁢KNCW-1,r)⁢O·βoffsetEquation⁢⁢(3)
In such embodiments, Q′ can be obtained in closed form as:

depends on O and βoffset.

After calculating a nominal number of control vector symbols124to allocate using any of the techniques described above, transmitter inn may process this nominal value from the above algorithms (e.g., the value Q′) as appropriate to ensure a certain type of final value or a final value in a particular range. Transmitter100may then use the nominal number, or the result of any such processing, to determine a number of vector symbols124to allocate to control information. For example, transmitter100may convert Q′ to an integer-valued result (e.g., using a ceiling function) or may set a minimum and/or maximum for Q′ to ensure that the number of allocated control vector symbols124is within a particular range. Alternatively, transmitter100may process any of the individual inputs used by the above algorithms (e.g., the estimated inverse spectral efficiency of user data) as appropriate to ensure a suitable type or range for the resulting output. As one specific example, transmitter100may utilize a minimum threshold for the inverse spectral efficiency of user data to ensure that the resulting number of vector symbols124allocated to each bit of control signaling is greater than a minimum amount. Thus, in particular embodiments, transmitter100may calculate the number of data vectors (Q′) to allocate for transmission of a particular control signal using a minimum inverse spectral efficiency value (Kmin) such that:

Q′=O·βoffset·max(Qall-Q′g⁡(∑r=0Cn,0-1⁢K0,r,5,∑r=0Cn,NCW-1⁢KNCW-1,r),Km⁢⁢i⁢⁢n)Equation⁢⁢(5)
Equation (5) can be rewritten to show that in such embodiments:

Additionally, particular embodiments of transmitter100may utilize a compensation offset parameter, on its own or in conjunction with a default offset parameter (such as the βoffsetparameter discussed above) to improve the spectral efficiency estimation for large control signaling payloads. For example, transmitter100may estimate a nominal inverse spectral efficiency based on a compensation offset parameter ({tilde over (β)}offset) using the formula:

Qallg⁡(∑r=0Cn,0-1⁢K0,r,5,∑r=0Cn,NCW-1⁢KNCW-1,r)+O⁢⁢β~offset
Thus, in such embodiments, transmitter100may allocate a number of vector symbols124, Q′, to a control signal, such that:

In some embodiments, use of a compensation offset parameter by transmitter100may be configurable by other elements of the communication network in which transmitter100is operating, such as an eNodeB when transmitter100represents a UE. In particular embodiments, a serving eNodeB or other node of the network may activate or deactivate large uplink control information (UCI) compensation in transmitter100, and thereby activate or deactivate use of the compensation offset parameter by transmitter100. For example, the serving eNodeB may transmit downlink control information instructing transmitter100to activate or deactivate large UCI compensation, and transmitter100may adjust its use of the compensation offset parameter accordingly.

Additionally, while particular embodiments of transmitter100may use a predetermined compensation offset parameter, alternative embodiments may receive the value of the compensation offset parameter from other elements of the communication network. For example, a serving eNodeB may transmit a compensation offset parameter to transmitter100and transmitter100may then use the received compensation offset parameter as described above. As a result, other elements of the communication network can configure the aggressiveness of the large UCI compensation performed by transmitter100. Furthermore, by permitting elements such as the serving eNodeB to adjust the transmitter's use of large UCI compensation, such embodiments can configure transmitter100to operate consistent with assumptions made by those elements when allocating transmission resources to transmitter100.

Thus, transmitter100may provide improved resource allocation techniques in a variety of different forms. Using these resource allocation techniques, certain embodiments of transmitter100may be able to match the allocation of control-signaling transmission resources to the quality of the relevant radio channel and to account for the use of multiple codewords or layers in making the allocation. Additionally, certain embodiments accurately account for the amount of transmission resources that will be used for control signaling when estimating the supported inverse spectral efficiency of the transmission channel, resulting in a more accurate estimate and, thus, an improved allocation. As a result, such embodiments may reduce the amount of overhead used to transmit control signaling when the control signaling is multiplexed with user data. Consequently, certain embodiments of transmitter100may provide multiple operational benefits. Specific embodiments, however, may provide some, none, or all of these benefits.

Although the description above focuses on implementation of the described resource allocation techniques in a transmitter, the above concepts can also be applied at a receiver. For example, when decoding transmissions received from transmitter100, a receiver may utilize certain aspects of the described techniques to estimate the amount of transmission resources that have been allocated to control signaling. Furthermore, the described concepts may be applied for purposed of scheduling use of transmission resources in wireless communication systems that utilize centralized resource management. For example, an eNode B may utilize certain aspects of the described techniques to estimate the amount of transmission resources a UE that incorporates transmitter100will allocate to control signaling for a given period of time or for a given amount of transmitted data. Based on this estimate, the eNode B may determine an appropriate number of transmission resources to schedule for use by the relevant UE.FIGS. 5-7describe in greater detail the contents and operation of example devices capable of performing such receiving and/or scheduling. Additionally, although the description herein focuses on implementation of the described resource allocation techniques in wireless communication networks supporting LTE, the described resource allocation techniques may be utilized in conjunction with any appropriate communication technologies including, but not limited to LTE, High-Speed Packet Access plus (HSPA+), and Worldwide Interoperability for Microwave Access (WiMAX).

FIG. 2is a functional block diagram showing in greater detail the operation of a particular embodiment of carrier modulator112. In particular,FIG. 2illustrates an embodiment of carrier modulator112that might be used by an embodiment of transmitter100that utilizes DFTS-OFDM as required for uplink transmissions in LTE. Alternative embodiments may be configured to support any other appropriate type of carrier modulation. The illustrated embodiment of carrier modulator112includes a DFT202, a precoder204, an inverse DFT (IDFT)206, and a plurality of power amplifiers (PAs)208.

Carrier modulator112receives vector symbols124output by layer mapper110. As received by carrier modulator112, vector symbols124represent time domain quantities. DFT202maps vector symbols124to the frequency domain. The frequency-domain version of vector symbols124are then linearly precoded by precoder204using a precoding matrix, W, that is (NT×r) in size, where NTrepresents the number or transmission antennas114to be used by transmitter100and r represents the number of transmission layers that will be used by transmitter100. This precoder matrix combines and maps the r information streams onto NTprecoded streams. Precoder204then generates a set of frequency-domain transmission vectors by mapping these precoded frequency-domain symbols onto a set of sub-carriers that have been allocated to the transmission.

The frequency-domain transmission vectors are then converted back to the time domain by IDFT206. In particular embodiments, IDFT206also applies a cyclic prefix (CP) to the resulting time-domain transmission vectors. The time-domain transmission vectors are then amplified by power amplifiers208and output from carrier modulator112to antennas114, which are used by transmitter100to transmit the time-domain transmission vectors over a radio channel to a receiver.

FIG. 3is a structural block diagram showing in greater detail the contents of a particular embodiment of transmitter100. Transmitter100may represent any suitable device capable of implementing the described resource allocation techniques in wireless communication. For example, in particular embodiments, transmitter100represents a wireless terminal, such as an LTE user equipment (UE). As shown inFIG. 3, the illustrated embodiment of transmitter100includes a processor310, a memory320, a transceiver330, and a plurality of antennas114.

Processor310may represent or include any form of processing component, including dedicated microprocessors, general-purpose computers, or other devices capable of processing electronic information. Examples of processor310include field-programmable gate arrays (FPGAs), programmable microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), and any other suitable specific- or general-purpose processors. AlthoughFIG. 3illustrates, for the sake of simplicity, an embodiment of transmitter100that includes a single processor310, transmitter100may include any number of processors310configured to interoperate in any appropriate manner. In particular embodiments, some or all of the functionality descried above with respect toFIGS. 1 and 2may be implemented by processor310executing instructions and/or operating in accordance with its hardwired logic.

Memory320stores processor instructions, equation parameters, resource allocations, and/or any other data utilized by transmitter320during operation. Memory320may comprise any collection and arrangement of volatile or non-volatile, local or remote devices suitable for storing data, such as random access memory (RAM), read only memory (ROM), magnetic storage, optical storage, or any other suitable type of data storage components. Although shown as a single element inFIG. 3, memory320may include one or more physical components local to or remote from transmitter100.

Transceiver330transmits and receives RF signals over antennas340a-d. Transceiver330may represent any suitable form of RF transceiver. Although the example embodiment inFIG. 3includes a certain number of antennas340, alternative embodiments of transmitter100may include any appropriate number of antennas340. Additionally, in particular embodiments, transceiver330may represent, in whole or in part, a portion of processor310.

FIG. 4is a flowchart detailing example operation of a particular embodiment of transmitter100. In particular,FIG. 4illustrates operation of an embodiment of transmitter100in allocating transmission resources to the transmission of control codewords120. The steps illustrated inFIG. 4may be combined, modified, or deleted where appropriate. Additional steps may also be added to the example operation. Furthermore, the described steps may be performed in any suitable order.

Operation begins at step402with transmitter100determining a number of bits in one or more user data codewords122to be transmitted during a subframe. In particular embodiments, user data codewords122may include CRC bits, and transmitter100may consider these CRC bits when counting the bits in the relevant user data codewords122. Additionally, in particular embodiments, the plurality of user data codewords counted by transmitter100may represent all of the user data codewords122to be transmitted during the subframe or only a subset of those user data codewords122. For example, in certain embodiments, transmitter100may determine the number of bits in step402based only on the user data codewords122to be transmitted on certain transmission layers.

In particular embodiments, transmitter100may be configured to selectively utilize the techniques described above to provide more accurate estimates of the optimal allocation for control signaling. For example, in particular embodiments, transmitter100may utilize the above described techniques when a compensation feature of transmitter100has been activated (e.g., as a result of instructions from a serving base station). Therefore, in such embodiments, transmitter100may determine whether a compensation feature of transmitter100is activated as part of allocating vector symbols to user data and control signaling. For the illustrated example, it is assumed that transmitter100determines that the compensation feature is activated as shown at step404. Because the compensation feature is activated, transmitter100will then use the resource allocation techniques described above, rather than an alternative allocation technique that does not account for the effect of control signaling allocation on the available resources for transmitting user data.

At step406, transmitter100then uses the number of bits of user data codewords122to be transmitted during the subframe to calculate a number of vector symbols124to allocate to control information. As discussed above, transmitter100also bases this calculation in part on an estimate of the number of user data vector symbols onto which the user data codewords122will be mapped (e.g., as reflected by an estimated inverse spectral efficiency for user data). In particular embodiments, the number of user data vector symbols depends on the number of control vector symbols that would result if the calculated number of user data vector symbols were in actuality allocated to the transmission of user data.

For the purposes of the example inFIG. 4, transmitter100calculates a number of control vector symbols equal to Q′ such that:

Q′=f(Q^data⁡(Q′),∑r=0Cn,0-1⁢K0,r,6⁢∑r=0Cn,NCW-1⁢KNCW-1,r,O).
As discussed above, transmitter100may estimate the number of vector symbols124to be allocated to user data codewords122in any suitable manner including, but not limited to, using any of the formulations of {circumflex over (Q)}datadiscussed above. Because Q′ is a function of {circumflex over (Q)}data, which itself depends on Q′, in particular embodiments, transmitter100may solve for Q′ and {circumflex over (Q)}datarecursively. Alternatively, transmitter100may utilize a formulation of {circumflex over (Q)}datathat permits Q′ to be expressed in a closed form, and thereby enables transmitter100to solve for Q′ explicitly. For example, as part of step406, transmitter100may estimate {circumflex over (Q)}dataas:

Q^data⁡(Q′)=Qall-β~offsetβoffset⁢Q′,
where βoffsetis a first offset value that can be used to adjust a target block error rate (BLER) for control information transmitted using the resulting allocation and {tilde over (β)}offsetis a second offset value that can be used to adjust the aggressiveness of the control information compensation. As a result, transmitter100may use {circumflex over (Q)}datato calculate a value for Q′ such that:

In particular embodiments, Q′ may represent a nominal number of control vector symbols, and transmitter100may apply certain additional processing steps to this nominal number of control vector symbols to produce an appropriate final number of control vector symbols124for the transmission. For example, the illustrated embodiment of transmitter100compares the nominal number of control vector symbols124to a minimum number that transmitter100is configured to use in transmitting control codewords120at step408. This minimum number of control vector symbols124may be a genetic minimum threshold applied to all control codeword120transmissions or may be a minimum determined by transmitter100for this specific transmission (for example, based on the payload of the control codewords120to be transmitted). Transmitter100may then select the greater of the nominal calculated number and the minimum number as the number of vector symbols124to allocate to control information, as shown at step410.

In addition, or as an alternative to ensuring a minimum allocation, transmitter100may be configured to perform any other appropriate post-processing to the nominal number of vector symbols124, such as converting the nominal number to an integer value (e.g., by applying a ceiling operation) or otherwise increasing or decreasing the nominal number to ensure a final number within a certain range, as represented by step412. Transmitter100may then use the nominal number or the output of any additional post-processing as the final number of vector symbols124to allocate to control signaling.

After determining the final number of vector symbols124to allocate to control signaling, transmitter100then maps control codewords120available for transmission to the calculated final number of vector symbols124at step414. Transmitter100may perform any appropriate processing of the control vector symbols124to permit transmission of the control vector symbols124to a receiver in communication with transmitter100including, for example, the processing described above with respect toFIG. 2. After completing any appropriate processing of vector symbols124, transmitter100then transmits control vector symbols124over a plurality of transmission layers using the plurality of antennas114at step416. Operation of transmitter100with respect to transmitting these particular control codewords120may then end as shown inFIG. 4.

FIG. 5is a structural block diagram showing the contents of a network node500that may serve as a receiver for control codewords120transmitted by transmitter100and/or that may serve as a scheduler for scheduling transmission of control codewords120by transmitter100. As noted above, the described resource allocation techniques may also be utilized by devices in decoding transmissions received from transmitter100or in determining the appropriate amount of transmission resources to schedule for use by transmitter100in a given subframe. For example, in particular embodiments, transmitter100may represent a wireless terminal (such as an LTE UE) and network node500may represent an element of a radio access network that receives uplink transmission from the wireless terminal or that is responsible for scheduling the wireless terminal's use of transmission resources (such as an LTE eNodeB).

As shown inFIG. 5, the illustrated embodiment of network node500includes a processor510, a memory520, a transceiver530, and a plurality of antennas540a-d. Processor510, memory520, transceiver530, and antennas540may represent identical or analogous elements to the similarly-named elements ofFIG. 3. In particular embodiments of network node500, some or all of the functionality of network node500described below with respect toFIGS. 6 and 7may be implemented by processor510executing instructions and/or operating in accordance with its hardwired logic.

FIG. 6is a flowchart detailing example operation of a particular embodiment of network node500. In particular,FIG. 6illustrates operation of an embodiment of network node500in receiving and decoding control codewords120received from transmitter100. The steps illustrated inFIG. 6may be combined, modified, or deleted where appropriate. Additional steps may also be added to the example operation. Furthermore, the described steps may be performed in any suitable order.

Operation of network node500begins at step602with network node500receiving a plurality of vector symbols124from transmitter100. For purposes of decoding the vector symbols124, network node500may need to determine the manner in which transmitter100allocated these vector symbols124between control signaling and user data. As a result, network node500may determine the number of the received vector symbols124tint transmitter100used to transmit control codewords120.

To properly decode the received vector symbols124, network node500may need to follow the same or an analogous procedure to what transmitter100used to determine the resource allocation on the transmitting side. Thus, depending on the configuration of the relevant transmitter100, network node500may be configured to determine the number of vector symbols124allocated to control codewords120(referred to herein as “control vector symbols”) using any of the techniques described above. An example of this process for the example embodiment is shown at steps604-608ofFIG. 6. In particular,FIG. 6describes operation of an embodiment of network node500that communicates with the transmitter100described byFIGS. 1-3. Thus, network node500performs steps604-614in a similar or analogous fashion to that described above for the similarly-captioned steps inFIG. 3.

After network node500has determined the final number of vector symbols124that transmitter100allocated to control codewords120, network node500decodes the received vector symbols124based on this number at step616. For example, network node500may use this information to determine which of the received vector symbols124are carrying control codewords120and which are carrying user data codewords122. If transmitter100has encoded control signaling and user data using different encoding schemes, network node500may then apply a different decoding scheme to the two types of vector symbols124. Operation of network node500with respect to decoding the received symbol vectors may then terminate as shown inFIG. 6.

FIG. 7is a flowchart detailing example operation of a particular embodiment of network node500responsible for scheduling the use of transmission resources by transmitter100. The steps illustrated inFIG. 7may be combined, modified, or deleted where appropriate. Additional steps may also be added to the example operation. Furthermore, the described steps may be performed in any suitable order.

InFIG. 7, operation of network node500begins at step702with network node500receiving a request for transmission resources from transmitter100. This request may represent any appropriate information indicating network node500has information, including one or both of control signaling and user data, to transmit in a geographic area served by network node500. In particular embodiments, network node500may represent an LTE eNodeB and this request may represent a scheduling request transmitted by transmitter100on PUCCH. Additionally, network node500may possess information regarding transmissions transmitter100is expected to make during the relevant subframe. For example, in the relevant subframe, transmitter may expect a HARQ ACK/NACK transmission from transmitter100responding to a previous transmission from network node500. Alternatively or additionally, in particular embodiments, the scheduling request received by network node500may indicate the amount and/or type of information transmitter100is intending to transmit.

In response to receiving the request, network node500may determine an allocation of transmission resources to grant to transmitter100for use in transmitting the requested transmission. To determine this allocation, network node500may determine the amount of control information and user data network node500expects transmitter100to transmit in conjunction with the request. Network node500may determine these amounts based on information included in the request itself, information maintained locally by network node500itself (e.g., information on expected control information transmissions), and/or information received from any other suitable source.

Furthermore, in particular embodiments, network node500determines this overall allocation based on the assumption that transmitter100will determine an allocation for control vector symbols for the requested transmission based on the techniques described above. Thus, network node500may also use the techniques above to grant an appropriate amount of transmission resources to transmitter100for the requested transmission. Because the above techniques may involve transmitter100determining an allocation of control vector symbols that depends in part on the allocation of user data vector symbols, network node500may likewise estimate the control allocation based on an estimated allocation for user data. Furthermore, in determining a total allocation for transmitter100, network node500may also account for the fact that, as described above, transmitter100will consider the resulting control vector symbol allocation when allocating vector symbols124to user data. This may result in network node500determining a total allocation for transmitter100comprised of a user data allocation and a control information allocation, which are dependent upon one another. Thus, in particular embodiments, network node500may determine the total allocation recursively. An example of this is shown by step704ofFIG. 7.

Depending on the configuration of transmitter100, network node500may process the estimated number of control vector symbols in an appropriate manner as described above before using the value to make the determination of step704. For example, network node500may calculate a nominal number of control vector symbols based on the estimated number of data vector symbols, the estimated number of bits of control codewords120, and the number of bits of user data to be carried by each of the user data codewords. Network node500may then scale this nominal number by an offset, increase the nominal number to meet a minimum number, apply a ceiling operation to the nominal, and, or perform any other appropriate processing to the nominal number to calculate the final estimated number of control vector symbols.

Network node500then uses this determination in responding to the request sent by transmitter100. In particular embodiments, if network node500decides to grant the request, network node500may communicate aspects of the determined allocation to transmitter100. Therefore, in particular embodiments, network node500may respond to the request by generating a particular response (e.g., a scheduling grant) to the request based on the determined allocation and transmitting the response to transmitter100, as shown by steps706-708ofFIG. 7. For example, in certain LTE embodiments, network node500may generate a scheduling grant that includes information indicating the determined transmission rank, the determined total number of vector symbols, and the number of bits to be used for each data codeword and send this scheduling grant to transmitter100. Alternatively or additionally, network node500may use the determined allocation in deciding whether to grant the request or in deciding how to prioritize the request. Operation of network node500with respect to scheduling transmitter100for this subframe may then terminate as shown inFIG. 7.