Technical Field

An example embodiment relates generally to communications within a network and, more particularly, to a hybrid multicarrier technique to facilitate communications within a network.

Background

Wireless network operators are generally limited by network capacity. In order to increase the network capacity, a wireless network operator must either obtain and/or deploy additional radio resources for extending its services and/or for improving its service quality or improve the efficiency of the radio resources that are currently being utilized. Improvements with respect to the system efficiency can be at either the link level or the network level. However, the capacity improvements attributable to techniques at the link level, such as modulation, coding, the use of different types of diversity schemes, etc. may not be as significant as techniques employed at the network level. For example, system efficiency improvement at the network level may be brought about by self-network optimization and network coordination optimization. In this regard, self-network optimization is typically performed for a single network using a single radio access technology (RAT), such as a single RAT for a single operator. Network coordination optimization generally coordinates the resources under different RATs, such as different RATs for different operators.

Some efforts to improve system efficiency have been based upon a reduction in the cell size so that the channel condition of the cell may be improved. By improving the channel condition, the system performance can correspondingly be improved so that higher throughput may be obtained. One technique for reducing the cell size is the use of local area networks to access a network, such as via a femtocell.

In conjunction with the use of a local area network to access the network of a wireless network operator, uplink transmission is typically a bottleneck for the system. By way of example, a long-term evolution (LTE) network utilizes orthogonal frequency division multiple access (OFDMA) as the multiple access technique for the downlink. In the uplink, however, an LTE network generally has to use a single carrier scheme, such as single carrier frequency division multiple access (SC-FDMA) or discrete Fourier transform (DFT) spread OFDMA (DFT-s-OFDMA), due to the high peak to average power ratio (PAPR) of the orthogonal frequency division multiplexed (OFDM) signal in an effort to reduce the PAPR. By utilizing a single carrier scheme for the uplink, however, the system flexibility is reduced, at least in comparison to the use of OFDMA, since the resource scheduling is not adapted. Further, the system performance of SC-FDMA is less than that of OFDMA in local area (LA) scenarios, that is, scenarios in which a local area network is utilized as the access network. However, PAPR in an LTE network is of sufficient importance that the tradeoff in system performance is required to improve the radio frequency (RF) efficiency. Summary

A method, apparatus and computer program product are therefore provided in order to provide a hybrid multicarrier technique to facilitate communications within a network including, but not limited to, a local area network. In this regard, the method, apparatus and computer program product of one embodiment may utilize DFT -based OFDM modulation for the pilot and control signals and filter bank (FB)-based OFDM modulation for the data in order to utilize the advantages of each multi-carrier modulation scheme. Indeed, the method, apparatus and computer program product of an example embodiment may improve upon the system efficiency, the system performance and the flexibility of the system by utilizing the advantages of both a DFT-based OFDM technique and an FB-based OFDM technique.

In one embodiment, a method is provided that includes modulating pilot and control signals in accordance with discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulation. The method of this embodiment also modulates data in accordance with filter bank (FB)-based OFDM modulation. In accordance with this embodiment, the method also causes DFT-based OFDM modulated pilot and control signals and FB-based OFDM modulated data to be transmitted within a network.

In another embodiment, an apparatus is provided that includes a processing system that may be embodied by at least one processor and at least one memory including computer program code. The processing system is arranged to cause the apparatus to at least modulate pilot and control signals in accordance with discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulation. The processing system is also arranged to cause the apparatus to modulate data in accordance with filter bank (FB)-based OFDM modulation, and to cause the apparatus to cause DFT-based OFDM modulated pilot and control signals and FB-based OFDM modulated data to be transmitted within a network.

In a further embodiment, a computer program product is provided that includes a set of instructions, which, when executed by a processing system, causes the processing system to modulate pilot and control signals in accordance with discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulation, to modulate data in accordance with filter bank (FB)-based OFDM modulation, and to cause DFT-based OFDM modulated pilot and control signals and FB-based OFDM modulated data to be transmitted within a network.

In yet another embodiment, an apparatus is provided that includes means for modulating pilot and control signals in accordance with discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulation. The apparatus of this embodiment also includes means for modulating data in accordance with filter bank (FB)-based OFDM modulation. In accordance with this embodiment, the apparatus also includes means for causing DFT-based OFDM modulated pilot and control signals and FB-based OFDM modulated data to be transmitted within a network.

In one embodiment, a method is provided that includes receiving discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulated pilot and control signals and filter bank (FB)-based OFDM modulated data that has been transmitted within a network. The method of this embodiment also includes demodulating the DFT -based OFDM modulated pilot and control signals and demodulating the FB-based OFDM modulated data.

In another embodiment, an apparatus is provided that includes a processing system, which may be embodied as at least one processor and at least one memory including computer program code. The processing system is arranged to cause the apparatus to receive discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulated pilot and control signals and filter bank (FB)- based OFDM modulated data that has been transmitted within a network. The processing system is also arranged to cause the apparatus to demodulate the DFT- based OFDM modulated pilot and control signals and to demodulate the FB-based OFDM modulated data.

In a further embodiment, a computer program product is provided that includes a set of instructions, which, when executed by a processing system, causes the processing system to perform the steps of: receive discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulated pilot and control signals and filter bank (FB)-based OFDM modulated data that has been transmitted within a network, and to demodulate the DFT -based OFDM modulated pilot and control signals and program instructions configured to demodulate the FB- based OFDM modulated data.

In yet another embodiment, an apparatus is provided that includes means for receiving discrete Fourier transform (DFT)-based orthogonal frequency division multiplex (OFDM) modulated pilot and control signals and filter bank (FB)-based OFDM modulated data that has been transmitted within a network. The apparatus of this embodiment also includes means for demodulating the DFT -based OFDM modulated pilot and control signals and means for demodulating the FB-based OFDM modulated data.

Brief Description of the Drawings

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: Figure 1 is a block diagram of a system in which a user equipment and/or an access point may communicate within a network in accordance with an example embodiment of the present invention;

Figure 2 is a block diagram of an apparatus that may be embodied by or included within a user equipment, an access point or other network entity and may be specifically configured in accordance with an example embodiment of the present invention;

Figure 3 is a flow chart of the operations performed in regards to both modulation and demodulation in accordance with an example embodiment of the present invention;

Figure 4 is a flow chart of the operations performed by an apparatus specifically configured in order to modulate the pilot and control signals and the data in accordance with an example embodiment of the present invention;

Figure 5 is a representation of the pilot, control and data subcarriers in the frequency domain in accordance with one example embodiment of the present invention;

Figure 6 is a representation of an FB-based OFDM symbol for data modulation and a DFT-based OFDM symbol for pilot and control signal modulation in accordance with an example embodiment of the present invention; and

Figure 7 is a block diagram of the operations performed by an apparatus specifically configured in order to demodulate the pilot and control signals and their data in accordance with an example embodiment of the present invention.

Detailed Description

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. 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.

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.

In this specification, modulation and demodulation techniques are discussed as being based on Orthogonal Frequency Division Multiplexing (OFDM). In particular, the modulation and/or demodulation may involve the use of Fourier Transforms (FTs). The Fourier Transforms used in the modulation and/or demodulation may comprise one or more Inverse Discrete Fourier Transforms (IDFTs) and Discrete Fourier transforms (DFTs). The IDFTs, in some examples, may be implemented by Inverse Fast Fourier Transforms (IFFTs) and the DFTs may be implemented by Fast Fourier Transforms (FFTs), so as to provide a simple, fast and efficient solution for the modulation and/or demodulation. The OFDM modulation-demodulation of data using IDFTs and/or DFTs is said to be generally DFT-based. For example, a DFT-based OFDM technique may use an IDFT-DFT pair for the modulation-demodulation (e.g. as defined in 3GPP LTE TS36.211 version 10.4.0 Release 10 (section 6.12)), whereby data is modulated for transmission using the IDFT and received data is demodulated using the DFT. A DFT-based OFDM technique may alternatively use a DFT-IDFT pair, whereby data for transmission is modulated using a DFT and received data is demodulated using an IDFT.

The term "FB-based OFDM" refers to OFDM techniques that use filter banks

(FBs) for use in modulating and/or demodulating data. The technique is also known as a "Filter Bank Multi-Carrier" (FBMC) technique. These terms are intended to include any OFDM modulation and/or demodulation technique which uses filter banks. A filter bank is an array of filters, such as band pass filters, that act to separate an input signal into multiple components or carriers. Each component carries a single frequency sub-band of the input signal. The output responses of FB-based OFDM typically has different characteristics to the output responses of DFT-based OFDM and as such, modulated and/or demodulated data using FB-based OFDM may have different characteristics (e.g. time and frequency) compared with if that data were to be modulated and/or demodulated using DFT-based OFDM.

A method, apparatus and computer program product are provided in accordance with an example embodiment of the present invention in order to support communication within a network, such as a local area network, utilizing a hybrid multicarrier technique in order to improve upon system efficiency, system performance and the flexibility with which the network may be accessed. In this regard, the method, apparatus and computer program product of an example embodiment may support communication within a network by modulating pilot and control signals in accordance with DFT-based OFDM modulation and modulating data in accordance with FB-based OFDM modulation. As such, the method, apparatus and computer program product of an example embodiment of the present invention may utilize advantageous futures of each of DFT-based OFDM modulation and FB-based OFDM modulation so as to provide corresponding system improvements.

The method, apparatus and computer program product of an example embodiment may be deployed in conjunction with a variety of systems, such as frequency domain division (FDD) systems or time domain division (TDD) systems. Although generally described hereinbelow in conjunction with a local area network, this description is provided by way of example and not of limitation since the method, apparatus and computer program product of an example embodiment may facilitate communications within various types of networks including both wide area networks and local area networks. Additionally, the method, apparatus and computer program of an example embodiment may be utilized in conjunction with any multicarrier, e.g., OFDMA, based network, such as LTE and WiMax networks and 802.11 networks and/or as a basic multiple access (MA) scheme for new networks operated at the gigahertz (GHz) level frequency bands. By way of illustration, but not of limitation, one example of a local area network in which user equipment 10 communicates with an access point 12 and/or with other user equipment is shown in Figure 1. In this embodiment, the user equipment may be any of a wide variety of different types of user equipment including a mobile terminal, such as a mobile communication device, e.g., a mobile telephone, portable digital assistant (PDA), pager, laptop computer, tablet computer, a modem, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. Alternatively, the user equipment may be a fixed terminal, such as a personal computer, a work station or other fixed computing or communication device. As shown in Figure 1, the user equipment of one embodiment may communicate with an access point of the network. While the access point may be configured in various manners, the access point of one embodiment may be embodied as a femtocell, a home evolved Node B (HeNB), an evolved Node B (eNB), a Node B, a base station, a relay point or other network entity for facilitating communications between the user equipment within the network and/or with one or more other networks.

An apparatus 20 that may be embodied by or included within one or more of the user equipment 10, the access point 12 or other network entity is shown in Figure 2. The apparatus 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.

In an example embodiment, the processing circuitry may include a processor 22 and memory 24 that may be in communication with or otherwise control a communication interface 26 and, at least in instances in which the apparatus 20 is embodied by the user equipment 10, a user interface 28. 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, the processing circuitry may be embodied as a portion of mobile terminal.

The user interface 28 (if implemented in embodiments of the apparatus 20 embodied by the user equipment 10) 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.

The communication interface 26 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 the network and/or any other device or module in communication with the processing circuitry. 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.

In an example embodiment, the memory 24 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, instructions or the like for enabling the apparatus 20 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 22. 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.

The processor 22 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.

Figures 3, 4 and 7 are flowcharts illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2, 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 24 of an apparatus employing an embodiment of the present invention and executed by a processor 22 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, 4 and 7, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 3, 4 and 7 define an algorithm for configuring a computer or processing circuitry, e.g., processor, to perform 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, 4 and 7 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

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 flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions. 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.

In accordance with an example embodiment of the present invention, the data and the control and pilot signals may be separately modulated and demodulated utilizing multicarrier modulation. As such, Figure 3 depicts the operations performed in order to separately modulate the data and the control and pilot signals and then, following transmission via a channel within the network, such as between the user equipment 10 and the access point 12 as shown in solid lines in Figure 1 or between two or more user equipment in the case of device to device communications as shown in dashed lines in Figure 1 , to separately demodulate the data and the control and pilot signals. In this regard, the pilot signals, such as the pilot sequence, and control information may initially be provided or received along with data. The apparatus 20 may include means, such as the processing circuitry, the processor 22, the communication interface 26 or the like, for providing for frequency sharing between the pilot and control signals and the data signals. See block 30 of Figure 3.

As illustrated in block 50 of Figure 4 which illustrates the operations performed by the apparatus 20 of one embodiment in conjunction with the modulation of signals to be transmitted within a network, such as between the user equipment 10 and the access point 12 or another user equipment, the pilot signals may be allocated over a frequency band with equal distance therebetween. The density of the pilot signals may be dependent upon the channel conditions. With respect to a local area network, for example, the channel may be relatively flat so that the density of the pilot signals may be correspondingly relatively low. As described below, the pilot signals may be initially utilized to estimate the response of its own, overall frequency response and to then estimate, such as by interpolation, the channel estimation results for the pilot subcarriers. As shown in Figure 5, the control signals may be allocated to separate subcarriers. In one embodiment, the pilot subcarrier may be positioned in the middle of, that is, intermediate, the control signal subcarriers in order to provide improved channel estimation accuracy, for example. As also shown in Figure 5, the data signals may be allocated to the frequencies not utilized by the pilot and control signals. In one embodiment, a guard band may be reserved between the pilot and control signals and the data signals. However, utilization of a guard band is optional.

In order to support the transmission of data for a plurality of users, the apparatus 20 may include means, such as the processing circuitry, the processor 22, the communication interface 26, or the like, for applying multicarrier code division multiple access (MC-CDMA) to separate the data of the different users. In this regard, the spreading of the data of the different users is performed in the frequency domain, thereby providing a larger number of user indices than conventionally provided by OFDMA. In one embodiment, the frequency domain spreading of the data of different users may be performed over an interval between two consecutive pilot subcarriers (in frequency), or over a larger frequency band.

As shown in operations 32 and 34 of Figure 3 and in operations 52 and 54 of

Figure 4, the apparatus 20 may include means, such as the processing circuitry, the processor, the communication interface or the like, for separately modulating pilot and control signals and the data. In this regard, the pilot and control signals may be modulated with DFT-based OFDM modulation, while the data may be modulated with FB-based OFDM modulation. More specifically, the DFT-based OFDM modulation in this example uses an IDFT. With regards to the DFT-based OFDM modulation for the pilot and control signals, the IDFT link may cover all of the carriers in the system. In this regard, the pilot and control signals may be allocated to their corresponding subcarriers and all other subcarriers including any optional guard band subcarriers may be set to zero. By utilizing DFT-based OFDM modulation for the pilot signals, a single pilot subcarrier may be sufficient for its own channel estimation and may improve system efficiency and/or channel estimation accuracy. By generally allocating the pilot signal in the middle of, that is, intermediate, the control signals subcarriers, DFT-based OFDM modulation may also be advantageously utilized for the control signals.

With respect to the FB-based OFDM modulation for the data, the FB-based

OFDM modulation may utilize only the subcarrier bands that include data and may not transmit anything in the bands that are allocated to the pilot and control signals. The modulation of the data with FB-based OFDM modulation avoids the need for a cyclic prefix for FB-based multicarrier (FBMC) so that the system efficiency may be improved. Additionally, the high sideband attenuation of a FBMC may reduce the inter-channel/subcarrier interference due to the channel impacts so that the data transmission quality may be improved. Further, the high sideband attenuation of the FBMC may also reduce the interference from data subcarriers to the control and pilot subcarriers. Additionally, further modulation, such as offset quadrature amplitude modulation (OQAM) may be applied in FBMC without loss of system efficiency in order to reduce the overall interference.

The method, apparatus and computer program product of an example embodiment may also provide flexibility regarding the subcarrier spacing defined for DFT-based and FB-based OFDM modulation. In this regard, the FB-based OFDM modulation and the DFT-based OFDM modulation need not necessarily utilize identical subcarrier spacing. As such, while taking into account the relationship between the subcarrier spacing, the OFDM symbol duration and the sampling frequency, the method, apparatus and computer program product may provide significant freedom to design various alternatives utilizing a combination of DFT- based OFDM modulation and FB-based OFDM modulation.

With regards to the DFT-based OFDM modulation of the pilot and control signals, relatively high spectrum efficiency may be obtained since the spectrum may be overlapped. Additionally, DFT-based OFDM modulation may utilize the cyclic prefix to remove or absorb the inter-symbol interference (ISI) due to multipath propagation. DFT-based OFDM modulation may also offer relatively high spectrum flexibility due to the management of the spectrum at a subcarrier level. Further, DFT- based OFDM modulation may provide for an efficient DFT implementation and a relatively simple receiver structure since only a single-tap frequency domain equalizer may be required.

However, DFT-based OFDM modulation may have a relatively large PAPR value in the time domain due to the OFDM symbol consisting of multiple-frequency modulated multiple-valued symbols. Although PAPR may be an issue of import for cellular systems having large cells, the limited dynamic range of the power amplifier may distort the relatively high PAPR signal significantly so that the radio frequency (RF) efficiency is lower than desired. However, for some scenarios utilizing a cellular-based local area network, the PAPR is of much less importance due to the relatively low transmit power requirement. DFT-based OFDM modulation also has relatively low sideband attenuation, that is, the sideband signal attenuation that is around 13 dB. In this instance, the in-band emission may be of importance if the system is affected by the frequency errors, such as either fixed frequency errors or the spread frequency errors due to Doppler. In other words, the low sideband attenuation may make the system more sensitive to frequency errors. Additionally, DFT-based OFDM modulation utilizes a cyclic prefix that assists in the design of the system, but reduces the overall system efficiency, such as by increasing the efficiency loss due to the addition of the cyclic prefix from 4% to 15% in regards to an LTE network.

With regards to the FB-based OFDM modulation of the data, the FB-based

OFDM modulation offers high sideband attenuation so as to be more robust to system errors, particularly frequency errors, in comparison to DFT -based OFDM modulation schemes. Additionally, FB-based OFDM modulation does not require a cyclic prefix, thereby correspondingly increasing the system efficiency. Additionally, FB-based OFDM modulation is robust to delay and offers high spectrum efficiency, such as by allowing spectrum overlapping so as to maximize the spectrum efficiency. Additionally, FB-based OFDM modulation may allow the use of real valued data modulation without reducing the spectrum efficiency, thereby allowing the interference to be reduced compared to complex domain modulation schemes.

However, FB-based OFDM modulation may have a relatively high system complexity. In this regard, an FB multicarrier modulation implementation may have a substantially greater complexity than a corresponding DFT-based OFDM modulation implementation. Indeed, if the number of taps of the channel equalizer utilized for FBMC is substantial, the complexity of the FBMC can be significantly higher than the DFT-based OFDM modulation scheme since a single tap equalizer is needed for the DFT-based OFDM modulation scheme. However, if there are complicated coding and/or equalization schemes involved in the receiver design, the complexity difference between the DFT-based OFDM modulation and FB-based OFDM modulation schemes is not substantial since the coding complexity may define the overall complexity of the receiver. Additionally, due to the impact of mobile channels, such as multipath fading channels, FBMC may have some inherent interference from its neighbors in time and frequency so that a single pilot is insufficient to provide accurate channel estimations. Thus, FB-based OFDM modulation may require an assist pilot to obtain the correct channel estimation values. The requirement of an assist pilot, however, will reduce the system efficiency since more resources are used for the channel estimation. Since FBMC has the capability to determine the weights of effects from the neighbor points, one or two of the neighbor points, such as from among eight neighbor points, can be designed to dominate the inherent interference. However, the effect from other neighbor points can still be considerable even if they are not emphasized by the FBMC design.

By combining both DFT-based OFDM modulation for the pilot and control signals and FB-based OFDM modulation for the data, the advantages of each of the DFT-based OFDM modulation scheme and the FB-based OFDM modulation scheme may be leveraged while reducing drawbacks or other shortcomings presented by each of the modulation schemes individually. In this regard, the use of FB-based OFDM modulation for the data may maximize the spectrum efficiency while the utilization of DFT-based OFDM modulation for the pilot and control signals may preserve the signal quality and improve the spectrum efficiency. Additionally, the combination of the DFT-based OFDM modulation for the pilot and control signals and the FB-based OFDM modulation for the data may provide different time and frequency domain signal processing schemes so that the system may be simplified without meaningful loss of system orthogonality.

As shown in block 36 of Figure 3 and block 56 of Figure 4, the apparatus 20 may include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for matching sample frequencies of the DFT- based OFDM modulated pilot and control signals (i.e. which, in this example, have been modulated using an ID FT) and the FB-based OFDM modulated data and for providing for symbol rate matching. In this regard, the apparatus, such as the processing circuitry, the processor, the communications interface, may match the sampling frequency of the DFT-based OFDM data flow and the FB-based OFDM data flow. Additionally, the apparatus, such as the processing circuitry, the processor, the communications interface or the like, may synchronize the data signals and the pilot and control signals. Depending upon the FBMC scheme that is utilized, the FBMC sampling frequency may be equal to or multiple times greater than the DFT- based OFDM sampling frequency. As such, prior to combining the DFT-based OFDM data flow and the FB-based OFDM data flow, the output of the modulator that generates the DFT-based OFDM modulated data may be upsampled, if the sampling frequency is less than that of the FB-based OFDM modulated data so that each data flow has the same sampling frequency.

With regards to symbol matching, the apparatus 20 may be configured in various manners. In an instance in which the cyclic prefix (CP)-extended pilot and control symbol is longer than the FB-based symbol (having a duration equal to two or more FBCM symbols) a shown in Figure 6, the pilot and control signals may use a narrow frequency band, but the data symbols may have to be buffered while awaiting the decoding of the pilot and control signals. In this regard, the channel may be time invariant for a certain period so that the pilot and control signals may be utilized for subsequent symbols and/or blocks. Alternatively, in an instance in which the CP- extended pilot and control symbol is shorter than the FB-based symbol, the subcarrier spacing for the pilot and control symbol is larger than the data subcarrier spacing. Still further, in an instance in which the CP-extended pilot and control symbols 52 and the data symbols 50 have the same length, a single IDFT may be utilized for both modulation schemes. Furthermore, by tuning the length of the CP and the subcarrier spacing, the symbol matching schemes may be designed so that it may facilitate the separation of FB OFDM and IDFT OFDM signals in either the time domain or the frequency domain. For instance, the length of the CP may be equal to the length of the FB-based symbol as shown in Figure 6. This scenario may require relatively long CPs. However, since the CP is used only for pilot and control signals, the overhead is not significant.

As shown in block 58 of Figure 4, the apparatus 20 may include means, such as the processing circuitry, the processor 22, the communication interface 26 or the like, for causing the DFT-based OFDM modulated pilot and control signals and the FB-based OFDM modulated data to be transmitted within a network. The modulated signals may be transmitted via an uplink channel in an instance in which the user equipment 10 has modulated the pilot and control signals and the data, and is providing the modulated signals to a network entity, such as the access point 12, or, in the case of device-to-device communications, to another user equipment, or via a downlink channel in an instance in which a network entity, such as the access point, has modulated the pilot and control signals and the data and is providing the modulated signals via the network to the user equipment or the like.

As shown in block 38 of Figure 3 and in block 70 of Figure 7, the apparatus 20 that is specifically configured in accordance with an example embodiment of the present invention, in order to receive and demodulate the signals, may include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for receiving DFT-based OFDM modulated pilot and control signals and the FB-based OFDM modulated data that has been transmitted within a network, such as a local area network. In one embodiment, as shown in block 38 of Figure 3 and in block 72 of Figure 7, the apparatus may include means, such as the processing circuitry, the processor, the communications interface or the like, for time domain signal processing the DFT-based OFDM modulated pilot and control signals and the FB-based OFDM modulated data. In this regard, the data and synchronization signals that are received may be resampled. In an embodiment in which the synchronization signal utilizes DFT-based OFDM modulation, the sampled signal may not be down sampled prior to the time domain sequence correlation. After initial synchronization has been obtained, the sampled data may be provided directly to the FB-based OFDM demodulator as embodied, for example, by the processor and/or the communication interface, for demodulating the data signals. This same data flow may be down sampled and provided to the DFT-based OFDM demodulator as embodied, for example, by the processor and/or the communication interface, in order to demodulate the pilot and control signals.

As shown in block 74 of Figure 7, the apparatus 20 may also include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for demodulating the DFT-based OFDM modulated pilot and control signals. As illustrated in blocks 40 and 44 of Figure 3, the demodulation of the DFT-based OFDM modulated pilot and control signals may initially involve pilot and control multicarrier demodulation, such as by using a DFT. As similarly shown in block 76 of Figure 7, the apparatus may include means, such as the processing circuitry, the processor, the communications interface or the like, for demodulating the FB-based OFDM modulated data. In this regard, and as shown in blocks 42 and 46 of Figure 3, the FB-based OFDM modulated data may be initially subjected to multicarrier demodulation followed by data demodulation. Although the operations of block 74 are shown to occur prior to the operations of block 76, the operations of blocks 74 and 76 may occur in other orders, such as either concurrently or with the operations of block 76 being performed prior to the operations of block 74 in other embodiments.

As a result of the combined signals, the demodulation of the DFT-based

OFDM modulated signal and the FB-based OFDM modulated signal may suffer from out-of-band signals. In this regard, the output resulting from the demodulation of the DFT-based OFDM modulated signal may include a portion attributable to the FB- based OFDM modulated signals and the output resulting from the FB-based OFDM modulated signal may include a portion attributable to the DFT-based OFDM modulated signals. In one embodiment in which the sampling frequency is identical for both the demodulation of the DFT-based OFDM modulated signals and the FB- based OFDM modulated signals, the demodulation of the DFT-based OFDM modulated signals and the FB-based OFDM modulated signals should not induce any interference in its own band, that is, the demodulated output from the DFT modulator for the FB-modulated signals is generally located in its own band and the demodulated output from the FB modulator for the DFT-modulated signals is generally located in its own band.

In another embodiment in which the sampling frequencies are different than the demodulation of the FB-based OFDM signals and the DFT-based OFDM signals, such as in an instance in which the OQAM/FBMC sampling frequency is two times higher than the DFT-based OFDM signal, the demodulation of the FB-based OFDM signals should not pose an issue since the demodulation occurs at a higher sampling frequency. In this regard, and in an instance in which the FB-based OFDM demodulation attempts to demodulate the DFT-based OFDM modulated signal, no out-of-band interference will be induced. Alternatively, the demodulated output of the DFT demodulator may include some alias signals resulting from the demodulation of the FB-based OFDM modulated signals since the DFT demodulation operates at a lower sampling frequency. In this regard, in a common instance in which the highest subcarrier frequency of the FB-based OFDM modulated signals is comparable to the highest subcarrier frequency of the DFT-based OFDM modulated signals, the DFT- based sampling frequency may be utilized so that there are no alias signals of the FB- based or FDM modulated signals produced by the DFT demodulator.

After multicarrier demodulation as shown in block 40, each subcarrier should contain its carried information with interference and distortions. The apparatus 20 may include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for demodulating the pilot signals to obtain channel estimations. See operation 44. A two-dimensional (time and frequency) interpolation channel estimation scheme may be utilized to estimate the channel response. The apparatus of this embodiment may also include means, such as the processing circuitry, the processor, the communications interface or the like, for correcting at least one control channel that includes the control signals based upon the channel estimates. The apparatus of this embodiment may also include means, such as the processing circuitry, the processor, the communications interface or the like, for demodulating the control signals once the control channel has been corrected.

Also after multicarrier demodulation as shown in block 42, the apparatus 20 may include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for demodulating the data based upon the channel estimates. As shown in block 48 of Figure 3, the channel estimation and equalization may not only be utilized to facilitate the demodulation of the control signals but also the demodulation of the FB-based OFDM modulated data.

By employing both DFT-based OFDM modulation in regards to the pilot and control signals and FB-based OFDM modulation in regards to the data, the system efficiency may be increased by allowing said spectrum overlapping, eliminating any need for a cyclic prefix for data subcarriers utilizing the FB-based OFDM modulation, avoiding the need for any assist pilots as a result of the DFT-based OFDM modulation and minimizing the use of pilots by two-dimensional, e.g., time and frequency, interpolation. The method and apparatus and computer program product of an example embodiment may also improve the system performance as a result of the high sideband attenuation of the data subcarriers that make the system more robust to frequency-related errors. The high side band attenuation also reduces the inter- channel interference between data subcarriers and the interference to pilot and control subcarriers from data subcarriers. The method, apparatus and computer program product of an example embodiment may also improve system performance by utilizing real valued modulation, such as OQAM, for data transmission so that the interference may be significantly reduced. System performance may also be improved by obtaining acceptable channel estimation and equalization results using single tap frequency domain equalization and time and frequency domain interpolation since DFT-based OFDM modulation is utilized for pilot transmission and, in one embodiment, the network is a local area network that assumes a relatively flat response in time and frequency.

The method, apparatus and computer program product of an example embodiment may also provide meaningful flexibility. In this regard, the allocation of pilot signals, control signals and data is flexible in regards to time and frequency since pilot and control signals and data signals are allowed to be transmitted at different subcarrier bandwidths. Additionally, pilot and control signals and data signals may have different symbol durations, thereby allowing more flexible control arrangement. Further, the actual allocation of pilot signals, control signals and data signals may be quite flexible in that the resource sharing pattern can either by dynamic or stable. Further, the method, apparatus and computer program product of an example embodiment may flexibly share the resources for multiple users and/or services. In this regard, due to the relatively flat response in the frequency domain, user and/or service separation may be obtained by frequency domain spreading which may be more efficient than direct FDMA-based sharing.

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.