The present disclosure relates generally to wireless communication systems and, more specifically, the present disclosure relates to a peak-to-average power ratio (PAPR) reduction based on a pulse shaping operation in a wireless communication system.
5th generation (5G) or new radio (NR) mobile communications is recently gathering increased momentum with all the worldwide technical activities on the various candidate technologies from industry and academia. The candidate enablers for the 5G/NR mobile communications include massive antenna technologies, from legacy cellular frequency bands up to high frequencies, to provide beamforming gain and support increased capacity, new waveform (e.g., a new radio access technology (RAT)) to flexibly accommodate various services/applications with different requirements, new multiple access schemes to support massive connections, and so on.
The present disclosure relates to a PAPR reduction based on a pulse shaping operation in a wireless communication system.
In one embodiment, a user equipment (UE) in a wireless communication system is provided. The UE comprises a processor configured to: convert, using a discrete Fourier transform (DFT), a modulated block of data symbols to a first symbol block in a frequency domain; extend, based on a spectral extension ratio associated with extended subcarriers (Nse), the first symbol block to a second symbol block with a length that is identified based on a number of scheduled subcarriers (NSC), wherein the second symbol block is symmetrically extended DFT symbol block, generate, using a frequency domain spectrum shaping (FDSS) filter with a number of tap values (NP), third symbol block based on the second symbol block that is symmetrically extended DFT symbol block, and map the generated third symbol block to the NSC, and generate, based on the mapped third symbol block, orthogonal frequency division multiplexing (OFDM) symbols in a time domain using an inverse fast Fourier transform (IFFT). The UE further comprises a transceiver operably coupled to the processor, the transceiver configured to transmit, to a base station (BS), signals including the OFDM symbols.
In another embodiment, a method of UE in a wireless communication system is provided. The method comprising: converting, using a DFT, a modulated block of data symbols to a first symbol block in a frequency domain; extending, based on a spectral extension ratio associated with Nse, the first symbol block to a second symbol block with a length that is identified based on the NSC, wherein the second symbol block is symmetrically extended DFT symbol block; generating, using an FDSS filter with NP, third symbol block based on the second symbol block that is symmetrically extended DFT symbol block; mapping the generated third symbol block to the NSC; generating, based on the mapped third symbol block. OFDM symbols in a time domain using an IFFT; and transmitting, to a BS, signals including the OFDM symbols.
In yet another embodiment, a BS in a wireless communication system, the BS comprises a processor and a transceiver operably coupled to the processor, the transceiver configured to receive, from a UE, signals including OFDM symbols, wherein: a modulated block of data symbols is converted to a first symbol block in a frequency domain using a DFT, based on a spectral extension ratio associated with Nse, the first symbol block is extended to a second symbol block with a length that is identified based on NSC, wherein the second symbol block is symmetrically extended DFT symbol block, using an FDSS filter with a number of tap values (NP), third symbol block is generated based on the second symbol block that is symmetrically extended DFT symbol block, the generated third symbol block is mapped to the NSC, and based on the mapped third symbol block, the OFDM symbols are generated in a time domain using an IFFT.
Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C. B and C, and A and B and C.
Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.
Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.
For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:
To meet the demand for wireless data traffic having increased since deployment of 4G communication systems and to enable various vertical applications, 5G/NR communication systems have been developed and are currently being deployed. The 5G/NR communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as to accomplish higher data rates or in lower frequency bands, such as 6 GHZ, to enable robust coverage and mobility support. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G/NR communication systems.
In addition, in 5G/NR communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancelation and the like.
The discussion of 5G systems and frequency bands associated therewith is for reference as certain embodiments of the present disclosure may be implemented in 5G systems. However, the present disclosure is not limited to 5G systems, or the frequency bands associated therewith, and embodiments of the present disclosure may be utilized in connection with any frequency band. For example, aspects of the present disclosure may also be applied to deployment of 5G communication systems, 6G or even later releases which may use terahertz. (THz) bands.
As shown in
The gNB 102 provides wireless broadband access to the network 130 for a first plurality of user equipments (UEs) within a coverage area 120 of the gNB 102. The first plurality of UEs includes a UE 111, which may be located in a small business; a UE 112, which may be located in an enterprise; a UE 113, which may be a Wifi hotspot; a UE 114, which may be located in a first residence; a UE 115, which may be located in a second residence; and a UE 116, which may be a mobile device, such as a cell phone, a wireless laptop, a wireless PDA, or the like. The gNB 103 provides wireless broadband access to the network 130 for a second plurality of UEs within a coverage area 125 of the gNB 103. The second plurality of UEs includes the UE 115 and the UE 116. In some embodiments, one or more of the gNBs 101-103 may communicate with each other and with the UEs 111-116 using 5G/NR, long term evolution (LTE), long term evolution-advanced (LTE-A), WiMAX, WiFi, or other wireless communication techniques.
Depending on the network type, the term “base station” or “BS” can refer to any component (or collection of components) configured to provide wireless access to a network, such as transmit point (TP), transmit-receive point (TRP), an enhanced base station (eNodeB or eNB), a 5G/NR base station (gNB), a macrocell, a femtocell, a WiFi access point (AP), or other wirelessly enabled devices. Base stations may provide wireless access in accordance with one or more wireless communication protocols. e.g., 5G/NR 3rd generation partnership project (3GPP) NR, long term evolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS” and “TRP” are used interchangeably in this patent document to refer to network infrastructure components that provide wireless access to remote terminals. Also, depending on the network type, the term “user equipment” or “UE” can refer to any component such as “mobile station.” “subscriber station.” “remote terminal.” “wireless terminal.” “receive point.” or “user device.” For the sake of convenience, the terms “user equipment” and “UE” are used in this patent document to refer to remote wireless equipment that wirelessly accesses a BS, whether the UE is a mobile device (such as a mobile telephone or smartphone) or is normally considered a stationary device (such as a desktop computer or vending machine).
Dotted lines show the approximate extents of the coverage areas 120 and 125, which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with gNBs, such as the coverage areas 120 and 125, may have other shapes, including irregular shapes, depending upon the configuration of the gNBs and variations in the radio environment associated with natural and man-made obstructions.
As described in more detail below, one or more of the UEs 111-116 include circuitry, programing, or a combination thereof, for a PAPR reduction based on a pulse shaping operation in a wireless communication system. In certain embodiments, and one or more of the gNBs 101-103 includes circuitry, programing, or a combination thereof, for supporting a PAPR reduction based on a pulse shaping operation in a wireless communication system.
Although
As shown in
The transceivers 210a-210n receive, from the antennas 205a-205n, incoming RF signals, such as signals transmitted by UEs in the network 100. The transceivers 210a-210n down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are processed by receive (RX) processing circuitry in the transceivers 210a-210n and/or controller/processor 225, which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The controller/processor 225 may further process the baseband signals.
Transmit (TX) processing circuitry in the transceivers 210a-210n and/or controller/processor 225 receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor 225. The TX processing circuitry encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The transceivers 210a-210n up-converts the baseband or IF signals to RF signals that are transmitted via the antennas 205a-205n.
The controller/processor 225 can include one or more processors or other processing devices that control the overall operation of the gNB 102. For example, the controller/processor 225 could control the reception of UL channel signals and the transmission of DL channel signals by the transceivers 210a-210n in accordance with well-known principles. The controller/processor 225 could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor 225 could support beam forming or directional routing operations in which outgoing/incoming signals from/to multiple antennas 205a-205n are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a wide variety of other functions could be supported in the gNB 102 by the controller/processor 225.
The controller/processor 225 is also capable of executing programs and other processes resident in the memory 230, such as processes for supporting a PAPR reduction based on a pulse shaping operation in a wireless communication system. The controller/processor 225 can move data into or out of the memory 230 as required by an executing process.
The controller/processor 225 is also coupled to the backhaul or network interface 235. The backhaul or network interface 235 allows the gNB 102 to communicate with other devices or systems over a backhaul connection or over a network. The interface 235 could support communications over any suitable wired or wireless connection(s). For example, when the gNB 102 is implemented as part of a cellular communication system (such as one supporting 5G/NR, LTE, or LTE-A), the interface 235 could allow the gNB 102 to communicate with other gNBs over a wired or wireless backhaul connection. When the gNB 102 is implemented as an access point, the interface 235 could allow the gNB 102 to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet). The interface 235 includes any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or transceiver.
The memory 230 is coupled to the controller/processor 225. Part of the memory 230 could include a RAM, and another part of the memory 230 could include a Flash memory or other ROM.
Although
As shown in
The transceiver(s) 310 receives from the antenna 305, an incoming RF signal transmitted by a gNB of the network 100. The transceiver(s) 310 down-converts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is processed by RX processing circuitry in the transceiver(s) 310 and/or processor 340, which generates a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuitry sends the processed baseband signal to the speaker 330 (such as for voice data) or is processed by the processor 340 (such as for web browsing data).
TX processing circuitry in the transceiver(s) 310 and/or processor 340 receives analog or digital voice data from the microphone 320 or other outgoing baseband data (such as web data, e-mail, or interactive video game data) from the processor 340. The TX processing circuitry encodes, multiplexes, and/or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The transceiver(s) 310 up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna(s) 305.
The processor 340 can include one or more processors or other processing devices and execute the OS 361 stored in the memory 360 in order to control the overall operation of the UE 116. For example, the processor 340 could control the reception of DL channel signals and the transmission of UL channel signals by the transceiver(s) 310 in accordance with well-known principles. In some embodiments, the processor 340 includes at least one microprocessor or microcontroller.
The processor 340 is also capable of executing other processes and programs resident in the memory 360, such as processes for a PAPR reduction based on a pulse shaping operation in a wireless communication system.
The processor 340 can move data into or out of the memory 360 as required by an executing process. In some embodiments, the processor 340 is configured to execute the applications 362 based on the OS 361 or in response to signals received from gNBs or an operator. The processor 340 is also coupled to the I/O interface 345, which provides the UE 116 with the ability to connect to other devices, such as laptop computers and handheld computers. The I/O interface 345 is the communication path between these accessories and the processor 340.
The processor 340 is also coupled to the input 350 and the display 355 which includes for example, a touchscreen, keypad, etc., The operator of the UE 116 can use the input 350 to enter data into the UE 116. The display 355 may be a liquid crystal display, light emitting diode display, or other display capable of rendering text and/or at least limited graphics, such as from web sites.
The memory 360 is coupled to the processor 340. Part of the memory 360 could include a random-access memory (RAM), and another part of the memory 360 could include a Flash memory or other read-only memory (ROM).
Although
The transmit path 400 as illustrated in
As illustrated in
The serial-to-parallel block 410 converts (such as de-multiplexes) the serial modulated symbols to parallel data in order to generate N parallel symbol streams, where N is the IFFT/FFT size used in the gNB 102 and the UE 116. The size N IFFT block 415 performs an IFFT operation on the N parallel symbol streams to generate time-domain output signals. The parallel-to-serial block 420 converts (such as multiplexes) the parallel time-domain output symbols from the size N IFFT block 415 in order to generate a serial time-domain signal. The add cyclic prefix block 425 inserts a cyclic prefix to the time-domain signal. The up-converter 430 modulates (such as up-converts) the output of the add cyclic prefix block 425 to an RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to the RF frequency.
A transmitted RF signal from the gNB 102 arrives at the UE 116 after passing through the wireless channel, and reverse operations to those at the gNB 102 are performed at the UE 116.
As illustrated in
Each of the gNBs 101-103 may implement a transmit path 400 as illustrated in
Each of the components in
Furthermore, although described as using FFT and IFFT, this is by way of illustration only and may not be construed to limit the scope of this disclosure. Other types of transforms, such as discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) functions, can be used. It may be appreciated that the value of the variable N may be any integer number (such as 1, 2, 3, 4, or the like) for DFT and IDFT functions, while the value of the variable N may be any integer number that is a power of two (such as 1, 2, 4, 8, 16, or the like) for FFT and IFFT functions.
Although
Discrete Fourier transform spreading OFDM (DFT-s-OFDM) is a single carrier waveform with low peak-to-average power ratio (PAPR) and could be a promising candidate waveform for B5G and 6G systems. Improving PAPR of DFT-s-OFDM may improve power amplifier efficiency, uplink coverage range and power consumption of UEs.
There are different PAPR reduction techniques for DFT-S-OFDM (such techniques may introduce signal distortion and sacrifice SE). Among them, a pulse shaping (also known as spectrum shaping) is known as a data-independent and low-complexity technique to reduce DFT-s-OFDM's PAPR at the cost of spectral extension (additional required subcarriers) and potentially higher symbol-error rate (SER).
Frequency domain spectrum shaping (FDSS) and time domain spectrum shaping (TDSS) are two equivalent solutions to implement spectrum shaping. However, due to DFT-s-OFDM, FDSS method is a more computationally efficient and flexible. Moreover, the power of the side lobes for FDSS is lower than the TDSS.
The Discrete Fourier transform spreading OFDM (DFT-s-OFDM) has been adopted and commercialized as a key uplink waveform for the 3GPP 4G/5G mobile communication systems and widely regarded as the baseline waveform of B5G/6G systems.
In DFT-s-OFDM, the application of DFT spreading operation prior to subcarrier mapping spreads the signal's energy across subcarriers, effectively achieves lower PAPR compared to OFDM, and improves power amplifier efficiency and reduces the risk of distortion. The pulse shaping filter is preceded by the spectral extension (SE) operation to reduce PAPR at the expense of the spectral extension.
While DFT-s-OFDM offers notable advantages, optimizing the pulse shaping filter presents a unique challenge, considering a tradeoff between SER, PAPR, spectral extension, complexity and spectral flatness requirements.
Conventionally, pulse shaping filters have been defined using well-established mathematical functions, such as cosine or exponential, offering limited flexibility in tailoring the filter to specific requirements. Recent works have explored parametric construction for the pulse shaping and combination of hyperbolic functions. However, such pulse shapes may not achieve the best SER-PAPR trade-offs for given spectral extension.
It can be shown that end-to-end learning process to obtain filter values in a data-driven fashion can outperform conventional baselines in terms of PAPR, with minimal SER degradation. By imposing specific filter structures, such FDSS parameters could be learned to achieve desired SER-PAPR-flatness-complexity trade-off, in which could be flexibly adapted for different number of resource blocks without re-training/learning of parameters.
The present disclosure introduces a novel approach to enhance the performance of DFT-s-OFDM systems by learning FDSS filter parameters over specific spectrum shapes. Leveraging advances in machine learning and deep learning techniques, a method is provided to train FDSS filters to achieve superior PAPR reduction while maintaining SER.
The learned parameters of FDSS for given SE can be utilized for arbitrary number of scheduled resource blocks. Moreover, different shapes/structures for FDSS are introduced to impose flatness and ISI-free constraints on filter design. Disclosed by methods for configuring filter values based on different SE ratio and number of RBs. Additionally, the abovementioned methods to adapt the learned parameters for different number of resource blocks without re-training parameters could be utilized for different objectives (not necessarily for PAPR improvement, e.g., sensing).
FDSS-DFT-S-OFDM offers flexibility a backward compatible with 4G/5G(rectangular pulse shaping without SE), while striking better SER, PAPR, complexity and spectral flatness requirements. Low implementation complexity, no side information at the Rx, small modification of original architecture of DFT-s-OFDM, backward compatibility can make FDSS-DFT-s-OFDM a waveform candidate for B5G and 6G systems.
The embodiments of the present disclosure are applicable in general to any communication system.
A modulated (e.g., π/2 BPSK, QPSK) block of Ndata symbols x=[x1, . . . , xN
The DFT symbol block is circularly extended to a symbol block with length Nsc as Xext=[Xext1, . . . , XN
ranging from 0 (no spectral extension) to 1 (100% spectral extension).
The symmetrically extended DFT symbol block with length Nsc goes through the FDSS filter with the tap values of F=[F1, . . . , Fk, . . . , FN
The filtered symbol block {tilde over (X)} is mapped to the scheduled subcarriers and is converted into the OFDM symbol in time domain by IFFT with length of Nfft as {tilde over (x)}=[{tilde over (x)}1, . . . , {tilde over (x)}N
An operation of DMRS is similar to the operation of data from the spectrum extension module, where UE applies same FDSS for both data and DMRS.
The receiver (e.g., gNB) removes the CP of the received OFDM symbol, obtains the samples with length Nfft as {tilde over (y)}=[{tilde over (y)}1, . . . , {tilde over (y)}N
Moreover, the receiver equalizes the symbols on scheduled subcarriers with element wise multiplication,
where F* is conjugate of F and {tilde over (F)}=[FN
After equalization, to obtain the DFT symbol block with length Ndata, the corresponding symbols on the spectrum extension and data subcarriers can be combined as schematic is shown in
The DFT symbol block with length Ndata,
Different FDSS structures/shapes are provided to facilitate learning process of FDSS parameters and achieve desired SER-PAPR-flatness-complexity trade-off.
Real-valued pulses in a time domain exhibit even symmetry in frequency domain, and three symmetrical FDSS structures are introduced to achieve desired trade-off between SER, PAPR, flatness and Complexity. “ISI-free-flat” and “flat” FDSSs are flat over passband, hence does not need any signal processing operation for passband. However, “non-flat” may require higher number of multiplication and memory storage. For “ISI-free-flat,” Nyquist condition of zero-ISI is imposed and does not have any SER loss compared to a case with rectangular pulse shaping without spectral extension. “Non-flat” may achieve lower PAPR (spectrum is bell-shaped) but it may have SER degradation.
For this purpose, G(b) for b=0,1, . . . , Np−1 is defined as a function of b that can completely represent introduced filter structures; Np is number of taps and its value is dependent on FDSS structure, number of extended subcarriers and number of total subcarriers as follows:
In one example of ISI-free-flat, Nyquist condition is imposed by design (zero-ISI pulse) and FDSS is flat (equals to one) for passband:
For “ISI-free-flat” FDSS, a number of filter parameters Np=Nse taps determines the FDSS completely: in other words, to construct “ISI-free flat” FDSS, Fk with 1≤k≤Nsc, Nse taps (or equivalently G(b)) for subcarrier indexes of Nsc−2Nse+1≤k≤Nsc−Nse (or equivalently for b=0,1, . . . , Nse−1) is sufficient.
In one example of flat, the passband is constrained to be one and each sideband has 2Nse taps. For flat structure, number of parameters is Np=2Nse frequency domain tap values (or equivalently G(b)) of subcarriers with index of Nsc−2Nse+1≤k≤Nsc (or equivalently for b=0,1, . . . , 2Nse−1) is adequate to define FDSS filter Fk with 1≤k≤Nsc, completely:
In one example of Non-flat, this filter may not have flat passband, therefore filter has only symmetrical constraint, Fk=FN
is adequate number of taps to define non-flat FDSS. In other words, G(b) for b=0,1, . . . , Nsc/2−1 can describe the FDSS, Fk with 1≤k≤Nsc, completely:
As it can be seen from
AI-based techniques can be exploited to obtain the FDSS parameters with objective of minimizing a loss function for given SE and “FDSS Structure.” Loss function can be defined as a weighted sum of SER, PAPR and spectral flatness.
FDSS parameters can be learnt and optimized based on one of the following ways: (1) polynomial coefficients; (2) frequency domain tap values of FDSS; and (3) time domain tap values of FDSS.
The learnt filter taps provide consistent PAPR improvement for given SE ratio, regardless of QAM order.
In one embodiment of polynomial coefficients, FDSS parameters (i.e., G(b) for b=0,1, . . . , Np−1) are modeled as coefficients using polynomial approximations. By selecting an appropriately high polynomial order, this approach offers the requisite expressiveness to capture the filter's behavior effectively. For this purpose, standard may specify Dth order polynomial coefficients (e.g., AI learned), αd for d=0, . . . , D for given FDSS structure and SE. Therefore, UE or BS can calculate G(b) for b=0,1, . . . , Np−1 as follows: G(b)=Σd=0, . . . ,D αd s(b)d where s(0), . . . , s (Np−1) is the support vector representing equally spaced values with step-size of
over interval [−1, +1], and bth element (b=0, . . . , Np−1) of support vector can be calculated as:
Finally, once G(b) for b=0,1, . . . , Np−1 is calculated, based on utilizing corresponding equations per FDSS structure (Equation 2 to 4), the complete FDSS can be constructed. The order of D can be specified in the standard, and D could be as small as 2 (e.g., for case of π/2 BPSK).
In one embodiment of frequency domain tap values of FDSS, it is assumed that Pm, m=1, . . . , Npref are FDSS taps corresponding to specific set of reference FDSS subcarriers (that is sufficient to define G( )) as follows:
2Nse
The following two-step procedure can be taken (by UE or gNB) to covert Npref taps to complete FDSS with Nsc taps: (1) resampling of reference taps: in this step Npref taps are resampled to Np taps; and (2) FDSS construction: Np taps are utilized to construct complete Nsc FDSS taps.
In one design, Npref parameters can be specified in standard for smallest subcarrier spacing (e.g., 15 KHz) and max number of subcarriers (e.g., Nsc
In another design, reference number of subcarriers can be selected for intermediate number of subcarriers (e.g., Nsc
Depending on FDSS type, a reference number of taps, Pk for k=1, . . . , Npref Npref can be specified in standard (learnt based on AI). An arbitrary number of taps with size of Np (Tk for k=1, . . . , Np) can be generated from resampling reference tap values. Value of Np can be obtained based on Equation 1.
For this purpose, the ratio Np/Npref can be simplified to a rational number L/M, i.e.,
This is accomplished by L-fold up-sampling, followed by low-pass filtering and then M-fold down sampling.
In one embodiment of L-fold up-sampling, Wk for k=1, . . . , Npref are up-sampled parameters of reference taps (P), is calculated as follows:
In one embodiment of low-pass filtering, output of L-fold up-sampling (W) goes through ideal low-pass filter via convolution operation (or equivalently multiplication for Fourier transform of W) as follows: Ek=convolution (W, 2fc sinc(2fck)) where
In one embodiment of M-fold down-sampling, in this step, a number of samples are reduced from LNpref to Np by discarding M−1 samples for every M samples in the original sequence, i.e., Tk=EMk for k=1, . . . , Np.
Once Np taps (Tk for k=1, . . . , Np) are obtained, they can be mapped to subcarrier indexes k according to following equation:
Then, Equations 2, 3, and 4 can be utilized to construct a complete FDSS as G(b), b=0, . . . , Np−1 is determined.
For example, if Npref=330, SE=20%, Nsc=240 and ISI-free flat structure is utilized, it can be shown that Nse=24 and based on Equation 1, Np=24. Based on
L=4 and M=55; first Pm, m=1, . . . , Npref=330, is up sampled by 4 and resulting on 1320 samples: after convolution with ideal low pass filter with
the resultant samples are down sampled by 55 and becomes 24 samples corresponding to target FDSS taps for taps Nsc−2Nse+1=193≤k≤Nsc-Nse=216 (according to Equation 2). By utilizing Equation 2, full FDSS can be constructed.
In one embodiment of time domain tap values of FDSS, time domain filter taps h=[h0, . . . , hz−1] (Z is number of time domain taps) can be: (1) learned directly using AI or any other techniques; or obtained by time domain representation of complete frequency domain reference FDSS taps (i.e., Fk
In both above-mentioned approaches, time domain filter taps can be specified in standard.
For a total subcarrier allocation of NSC, Nsc frequency domain filter taps F1, . . . , FN
0≤k≤Nsc−1 (Equation 6).
With this approach, a UE or a gNB can calculate complete frequency domain FDSS filter taps based on number of subcarriers directly from the Fourier transform. Examples of time domain representation of complete frequency domain reference FDSS taps (learned using AI) is given in TABLE 8.
The summary of all three methods is given in TABLE 1.
The 10th order polynomial function (D=10) is utilized to learn coefficients αd, d=0, . . . ,10. The example coefficients are given per example structure and PAPR gain/SNR loss compared to baseline root-raised-cosine filter (RRC) is provided in TABLE 2 under QPSK modulations when 384 subcarriers are utilized as reference. The given filter values may need to be normalized to have unit energy.
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=33,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=24,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=19,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=9,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=33,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=24,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=19,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=33,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=24,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=19,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nsea=9,
QPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
The π/2-BPSK modulation, is a constellation-rotated BPSK modulation offers a much smaller PAPR of the transmitted signal than the QPSK. The π/2-BPSK modulation increases the number of supported cell-edge users that are power-limited and could increase the overall spectral efficiency of the system. Basic pulse shaping without spectral extension has been defined in 5G(since Rel-15) for π/2-BPSK, while the exact pulse shape is not defined in the specifications. It can be shown that by using spectral extension, the pulse-shaping can achieve much better PAPR performance for π/2 BPSK. Simulation results of AI-based pulse shaping demonstrate PAPR improvement compared to RRC. For instance, for SE=14%, non-flat offers about 0.7 dB PAPR gain and less than 0.05 dB SNR loss due to SER. TABLE 3 summarizes PAPR gain and SNR loss compared to RRC for three different filter structures. Additionally,
The 10th order polynomial function (D=10) is utilized to learn example FDSS coefficients αd, d=0, . . . ,10. The given filter values may need to be normalized to have unit energy.
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=33,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=24,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “ISI-free-flat” structure with Nsc=384, Nse=19,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=33,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=24,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “flat” structure with Nsc=384, Nse=19,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=33,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=24,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
In one embodiment of polynomial design for “non-flat” structure with Nsc=384, Nse=19,
π/2-BPSK, the polynomial coefficients are given as follows for this scenario, and the FDSS shape is illustrated in
Multiple examples of complete reference FDSS frequency domain tap values for Nsc
As it can be seen, FDSS-DFT-S-OFDM, achieves about 0.5 dB, 0.7 dB and 1.1 dB PAPR gains respectively compared with RRC based FDSS-DFT-s-OFDM at 10−3 CCDF level at 10−2 SER.
TABLE 5 shows complete FDSS taps for Nsc=384 and Nse=24 subcarriers, tap values for subcarrier index (SCI) of 1 to 192 is shown, the rest of subcarriers 193 to 384 has same values as first half of filter.
Multiple complete reference FDSS frequency domain tap values for Nsc
Time domain representation of complete frequency domain reference FDSS taps of TABLE 5 using inverse Fourier transform is shown in TABLE 8. A UE or a gNB can calculate complete frequency domain
FDSS filter taps based on number of subcarriers directly from the inverse Fourier transform of tap values from TABLE 8 based on Equation 6.
As illustrated in
In step 3904, the UE extends, based on a spectral extension ratio associated with Nse, the first symbol block to a second symbol block with a length that is identified based on NSC, wherein the second symbol block is symmetrically extended DFT symbol block.
In step 3906, the UE generates, using an FDSS filter with Np, third symbol block based on the second symbol block that is symmetrically extended DFT symbol block.
In step 3908, the UE maps the generated third symbol block to the NSC.
In step 3910, the UE generates, based on the mapped third symbol block, OFDM symbols in a time domain using an IFFT.
In step 3912, the UE transmits, to a BS, signals including the OFDM symbols.
In one embodiment, the UE identifies the Np based on a number of extended subcarriers and a number of total subcarriers.
In such embodiment, based on the Np, the FDSS filter is identified as one of: (1) an ISI-free-flat FDSS filter with the number of Nse, (2) a flat FDSS filter with twice the Nse, or (3) a non-flat FDSS filter with the NSC.
In one embodiment, the UE identifies polynomial coefficients with a Dth order and applies a set of FDSS parameters including the polynomial coefficients to the FDSS filter.
In one embodiment, the UE identifies Pm in the frequency domain, each of the Pm in the frequency domain corresponding to a set of reference FDSS subcarriers and applies a set of FDSS parameters including the Pm in the frequency domain to the FDSS filter.
In one embodiment, the UE re-samples a set of reference taps (Np_ref) to obtain the Np for the FDSS filter and utilizes the number Np to obtain the NSC for the FDSS filter.
In one embodiment, the UE maps the Np to a set of subcarrier indexes based on the Pm in the frequency domain and constructs the FDSS filter based on the mapped set of subcarrier indexes.
In one embodiment, the UE identifies h in the time domain based on Np_ref and applies a set of FDSS parameters including the h in the time domain to the FDSS filter.
The above flowcharts illustrate example methods that can be implemented in accordance with the principles of the present disclosure and various changes could be made to the methods illustrated in the flowcharts herein. For example, while shown as a series of steps, various steps in each figure could overlap, occur in parallel, occur in a different order, or occur multiple times. In another example, steps may be omitted or replaced by other steps.
Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims. None of the description in this application should be read as implying that any particular element, step, or function is an essential element that must be included in the claims scope. The scope of patented subject matter is defined by the claims.
The present application claims priority to U.S. Provisional Patent Application No. 63/543,595, filed on Oct. 11, 2023. The contents of the above-identified patent documents are incorporated herein by reference.
Number | Date | Country | |
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63543595 | Oct 2023 | US |