Method and apparatus for spectrally shaped signals in discrete affine frequency transform domain

Abstract

The present disclosure generally relates to generation of AFDM signals. An apparatus for obtaining a first pilot sequence comprising a set of pilot symbols and obtaining a plurality of chirp signals. The number of the chirp signals is equal to the sequence length of the first pilot frequency sequence. The apparatus is configured to generate a second pilot sequence based on a linear combination of the plurality of chirp signals, where a set of the pilot symbols of the first sequence is used as a linear combination coefficient. In this way, the second pilot sequence is bandwidth controllable, and spectrum shaping may be performed to fit a target spectrum occupancy. Furthermore, in order to ensure that both the pilot sequence and the data sequence can be spectrally shaped to fit the target spectrum occupancy, the data symbols of the data sequence can be pre-coded using IDFT or DAFT, where the specific input symbols are set to zero (zeroing).

Description

Technical Field

[0001] The present disclosure relates generally to the field of wireless communications. For example, the present disclosure relates to spectrum shaping affine frequency division multiplexing (AFDM) signals in discrete affine frequency transform (DAFT) domain. Background Art

[0002] Orthogonal chirp division multiplexing (OCDM) and AFDM are chirped multi-carrier waveforms based on wireless communications. OCDM is based on discrete Fresnel transform (DFnT), while AFDM is based on DAFT. DAFT is a generalization of discrete Fourier transform (DFT), which is a linear transform characterized by several parameters (c1, c2). DFnT is a special case of DAFT. In DAFT, the transmitter uses inverse discrete affine Fourier transform (IDAFT) to map the input symbols of the transmitter to a discrete time chirp signal parameterized by (c1, c2) at its output. This is similar to orthogonal frequency-division multiplexing (OFDM), which is based on DFT, where the OFDM transmitter uses an inverse discrete Fourier transform (IDFT) to map the input symbols of the OFDM transmitter to frequency subcarriers at its output. AFDM can achieve full diversity for linear time-varying (LTV) channels with low pilot overhead. AFDM can also provide extension (or coverage) gain that is robust to mobility, carrier frequency offset (CFO), and phase noise. Therefore, AFDM is suitable for high-mobility communications.

[0003] In OCDM and AFDM, the parameters (c1, c2) are set so that each DAFT domain symbol (i.e., each symbol at the input of the IDAFT module of the transmitter) is mapped to a chirp that spans the entire bandwidth. The "entire bandwidth" in the present disclosure can be understood as a frequency bandwidth equal to the sampling rate of the digital-to-analog converter (DAC) used to generate the signal. In order to control the bandwidth of these signals, the only way is to change the sampling rate of the DAC. This limits the flexibility of multi-user multiplexing schemes and pilot designs. In addition, in order to maintain the orthogonality between the chirps in OCDM and AFDM, the same sampling rate value used by the DAC at the transmitter should also be used by the analog-to-digital converter (ADC) for sampling at the corresponding receiver. However, since the signal bandwidth is equal to the sampling rate, this imposes very strict restrictions on the anti-aliasing filter, which should be used at the receiver before the ADC. Under these conditions, any non-zero roll-off of the anti-aliasing filter can generate a signal with a bandwidth greater than the sampling rate of the ADC at the output of the anti-aliasing filter. This causes the Nyquist constraint to be violated when sampling the output signal, resulting in aliasing.

[0004] In general, one of the main advantages of chirp signals (especially AFDM signals) is that channel estimation performance can be achieved based on chirp-based pilot sequences. Pilot sequences (or pilots for short) are signals known to the receiving device, which are inserted (or mixed) into the transmitted signal so that the receiving device can estimate the impact of channel propagation on the transmitted signal. In long-term evolution (LTE) and new-radio (NR) systems, downlink pilots include downlink demodulation reference signals (DMRS) and channel state information reference signals (CSI-RS), while uplink pilots include uplink demodulation reference signals (DMRS) and sounding reference signals (SRS). Since the multi-chirp signals in AFDM are based on discrete affine Fourier transform (DAFT), each chirp pilot obtained in AFDM is equivalent to a DAFT domain symbol, which usually spans the entire bandwidth. Summary of the invention

[0005] Spectrum shaping is often used in multiple access applications, where modern communication systems are mainly based on multiple access applications. However, since each chirp pilot in AFDM spans the entire bandwidth, this poses a challenge to spectrum shaping.

[0006] The object of the present disclosure is to provide an apparatus and method for generating an affine frequency division multiplexing (AFDM) signal having a controllable bandwidth occupancy. The above and other objects can be achieved by the features of the independent claims. Other implementations are apparent from the dependent claims, the description and the drawings.

[0007] According to a first aspect, a device for generating a signal is provided. The device is used to obtain a first pilot sequence according to a sequence length and a frequency bandwidth. The first pilot sequence includes a set of pilot symbols. The device is also used to obtain a plurality of chirp signals. The number of the chirp signals is equal to the sequence length. The device is also used to generate a linear combination of the plurality of chirp signals to obtain a second pilot sequence, wherein the set of pilot symbols is used as a linear combination coefficient.

[0008] In this way, the acquired second pilot sequence will not span the entire bandwidth. For example, according to different bandwidth requirements for different transmission requirements, the second pilot sequence can be limited to a certain bandwidth frequency.

[0009] Optionally, the device may also be configured to send the second pilot sequence to a receiving end, etc. The sent second pilot sequence may be used for channel estimation.

[0010] In an implementation manner of the first aspect, in order to generate the linear combination of the plurality of chirp signals, the device may be configured to map the first pilot sequence to a continuous input of IDAFT modulation.

[0011] In this way, the first pilot sequence in the DAFT domain is transformed into the second pilot sequence in the time domain through IDAFT modulation.

[0012] In an implementation of the first aspect, before generating the linear combination of the multiple chirp signals, the device can be used to: shift the first pilot sequence in the frequency domain by multiplying the first pilot sequence by a frequency shift vector element by element according to a frequency value.

[0013] In this way, the second pilot sequence can be fitted to the target frequency band. That is, the first pilot sequence can be shifted in the frequency domain so that its signal bandwidth is centered on the frequency value. Correspondingly, the signal bandwidth of the second pilot sequence is also centered on the frequency value.

[0014] In an implementation manner of the first aspect, the device may be configured to: use the sequence length and the frequency bandwidth as indexes to acquire the first pilot sequence through a predefined lookup table.

[0015] By storing the first pilot sequence in the lookup table, the device no longer needs to calculate the first pilot sequence in real time, thereby saving computing resources of the device and reducing processing delay when sending signals.

[0016] In an implementation manner of the first aspect, the device may be configured to acquire the first pilot sequence through the following steps:

[0017] -Acquire an initial sequence according to the sequence length;

[0018] - acquiring a plurality of projection sequences, wherein each projection sequence in the plurality of projection sequences has the same sequence length as the initial sequence, and a bandwidth is limited within the frequency bandwidth;

[0019] - By combining the initial sequence with the projection matrix PP H Left multiplication generates an orthogonal projection of the initial sequence on the span of the multiple projection sequences to obtain the first pilot sequence, wherein the columns of the matrix P are the multiple projection sequences.

[0020] These steps may be viewed as a method for generating a first pilot sequence used by a device to acquire a first pilot sequence.

[0021] Optionally, the predefined lookup table may include multiple first pilot sequences generated according to different combinations of sequence lengths and frequency bandwidths using the first pilot sequence generation method.

[0022] In an implementation manner of the first aspect, in order to obtain the initial sequence, the device may be configured to generate the initial sequence based on a cell identifier and / or a scrambling sequence.

[0023] In this way, the second pilot sequence based on the initial sequence and the first pilot sequence can be changed from one serving cell area to another serving cell area or over time, for example, to reduce inter-cell interference.

[0024] In an implementation manner of the first aspect, the plurality of projection sequences may include a discrete prolate spheroidal sequence (DPSS) corresponding to the sequence length and the frequency bandwidth.

[0025] DPSS has the best time-frequency positioning. Therefore, compared with other first pilot sequences of the same length generated using projection sequences other than DPSS, the generated first pilot sequence can be better positioned within the target frequency band. Thanks to this feature, the overhead of using the set of pilot symbols in the first pilot sequence as linear combination coefficients can be reduced. Because orthogonal projection using DPSS can achieve good frequency positioning of the pilot signal with fewer chirped carriers, more chirped carriers can be used for data transmission.

[0026] In an implementation manner of the first aspect, the plurality of projection sequences may include columns of a DFT matrix corresponding to the sequence length and the frequency bandwidth.

[0027] Using the DFT matrix as the projection sequence is particularly effective when the value of the sequence length is large.

[0028] In an implementation of the first aspect, the device may also be used for:

[0029] - obtaining a plurality of the first pilot sequences whose bandwidth is limited to non-overlapping frequency bands;

[0030] - providing said plurality of said first pilot sequences as the same input or overlapping inputs for IDAFT modulation.

[0031] In this way, the multiple second pilot sequences obtained as outputs of the IDAFT modulation are still orthogonal to each other.

[0032] In an implementation of the first aspect, the device may also be used for:

[0033] - obtaining a plurality of the first pilot sequences with bandwidth limited within overlapping frequency bands;

[0034] - providing said plurality of said first pilot sequences as non-overlapping inputs for IDAFT modulation.

[0035] In this way, the multiple second pilot sequences obtained as outputs of the IDAFT modulation are still orthogonal to each other.

[0036] In an implementation of the first aspect, the device may also be used for:

[0037] - Get a collection of data symbols;

[0038] - Provide the set of data symbols as N FFT Point inverse discrete Fourier transform (IDFT) input;

[0039] - The N FFTSet one or more data symbols of the input of the IDFT to zero and obtain the N FFT Point to the output of IDFT;

[0040] - Provide the N FFT The output of the IDFT and the first pilot sequence are aggregated as N DAFT Point to the input of IDAFT to obtain the N DAFT The output of IDAFT, where N FFT Less than N DAFT .

[0041] N DAFT The output of the point IDFAT includes, for example, pilot symbols to be transmitted (eg, included in the second pilot sequence) and data symbols superimposed in the time domain. In this way, both the pilot symbols to be transmitted and the data symbols can be spectrally shaped to fit the target spectrum occupancy.

[0042] It is worth noting that N FFT The "FFT" in N stands for "Fast Fourier Transform". FFT N represents the number of input points for the IDFT performed by the device. DAFT Indicates the number of input points of the IDAFT executed by the device. N FFT and N DAFT All are positive integers.

[0043] In an implementation manner of the first aspect, the device may be N DAFT Discrete affine Fourier transform-spread affine frequency division multiplexing (DAFT-s-AFDM) transmitter. The DAFT-s-AFDM transmitter can also be used for:

[0044] - Get a collection of data symbols;

[0045] - Provide the set of data symbols as N FFT Click DAFT input;

[0046] - The N FFT Set one or more data symbols of the input of the DAFT to zero and obtain the N FFT Click the DAFT output;

[0047] - Provide the N FFT The output of the DAFT point and the aggregation of the first pilot sequence are used as N DAFT Point to the input of IDAFT to obtain the NDAFT The output of IDAFT, where N FFT Less than N DAFT .

[0048] N DAFT The output of the point IDFAT includes the pilot symbols to be transmitted (eg, included in the second pilot sequence) and the data symbols superimposed in the time domain. In this way, both the pilot symbols to be transmitted and the data symbols can be spectrally shaped to fit the target spectrum occupancy.

[0049] In an implementation manner of the first aspect, the first pilot sequence may be a downlink demodulation reference signal or a channel state information reference signal.

[0050] In an implementation manner of the first aspect, the first pilot sequence may be an uplink demodulation reference signal or a sounding reference signal.

[0051] According to a second aspect, a method for generating a signal is provided. The method comprises the following steps:

[0052] - the device acquires a first pilot sequence according to the sequence length and the frequency bandwidth, wherein the first pilot sequence includes a set of pilot symbols;

[0053] - the device acquires a plurality of chirp signals, wherein the number of the plurality of chirp signals is equal to the sequence length;

[0054] - the device generates a linear combination of the plurality of chirp signals to obtain a second pilot sequence, wherein the set of pilot symbols is used as linear combination coefficients.

[0055] In an implementation of the second aspect, the step of generating the linear combination of the plurality of chirp signals may include mapping the first pilot sequence to a continuous input of IDAFT modulation.

[0056] In an implementation manner of the second aspect, before generating the linear combination of the multiple chirp signals, the method may also include: shifting the first pilot sequence in the frequency domain by multiplying the first pilot sequence by a frequency shift vector element by element according to a frequency value.

[0057] In an implementation manner of the second aspect, the first pilot sequence can be acquired through a predefined lookup table by using the sequence length and the frequency bandwidth as indexes.

[0058] In an implementation manner of the second aspect, the step of acquiring the first pilot sequence may include the following steps:

[0059] -Acquire an initial sequence according to the sequence length;

[0060] - acquiring a plurality of projection sequences, wherein each projection sequence in the plurality of projection sequences has the same sequence length as the initial sequence, and a bandwidth is limited within the frequency bandwidth;

[0061] - By combining the initial sequence with the projection matrix PP H Left multiplication generates an orthogonal projection of the initial sequence on the span of the multiple projection sequences to obtain the first pilot sequence, wherein the columns of the matrix P are the multiple projection sequences.

[0062] In an implementation manner of the second aspect, the step of acquiring the initial sequence may include generating the initial sequence based on a cell identifier and / or a scrambling sequence.

[0063] In an implementation manner of the second aspect, the multiple projection sequences may include discrete prolate ellipsoid sequences corresponding to the sequence length and the frequency bandwidth.

[0064] In an implementation of the second aspect, the plurality of projection sequences may include columns of a discrete Fourier transform matrix corresponding to the sequence length and the frequency bandwidth.

[0065] In an implementation of the second aspect, the method may further include the following steps:

[0066] - obtaining a plurality of the first pilot sequences whose bandwidth is limited to non-overlapping frequency bands;

[0067] - providing said plurality of said first pilot sequences as the same input or overlapping inputs for IDAFT modulation.

[0068] In an implementation of the second aspect, the method may further include the following steps:

[0069] - obtaining a plurality of the first pilot sequences with bandwidth limited within overlapping frequency bands;

[0070] - providing said plurality of said first pilot sequences as non-overlapping inputs for IDAFT modulation.

[0071] In an implementation of the second aspect, the method may further include the following steps:

[0072] - Get a collection of data symbols;

[0073] - Provide the set of data symbols as N FFT Click the IDFT input;

[0074] - The N FFT Set one or more data symbols of the input of the IDFT to zero and obtain the N FFTPoint to the output of IDFT;

[0075] - Provide the N FFT The output of the IDFT and the first pilot sequence are aggregated as N DAFT Point to the input of IDAFT to obtain the N DAFT The output of IDAFT, where N FFT Less than N DAFT .

[0076] In an implementation of the second aspect, the method may be performed by an N device serving as the device DAFT The method may further include the following steps:

[0077] - the transmitter obtains a set of data symbols;

[0078] - the transmitter provides the set of data symbols as N FFT Click DAFT input;

[0079] - The transmitter sends the N FFT Set one or more data symbols of the input of the DAFT to zero and obtain the N FFT Click the DAFT output;

[0080] - The transmitter provides the N FFT The output of the DAFT point and the aggregation of the first pilot sequence are used as N DAFT Point to the input of IDAFT to obtain the N DAFT The output of IDAFT, where N FFT Less than N DAFT .

[0081] In an implementation manner of the second aspect, the first pilot sequence may be a downlink demodulation reference signal or a channel state information reference signal.

[0082] In an implementation manner of the second aspect, the first pilot sequence may be an uplink demodulation reference signal or a sounding reference signal.

[0083] The method described in the second aspect and its implementation manner can achieve the same advantages and effects as the device described in the first aspect and its implementation manner.

[0084] A third aspect of the present disclosure provides a computer program comprising instructions. When the program is executed by a computer, the instructions cause the computer to perform the method according to the second aspect or any one of its implementations.

[0085] A fourth aspect of the present disclosure provides a non-transitory storage medium, which stores executable program code. When the executable program code is executed by a processor, the method according to the second aspect or any one of its implementations is performed.

[0086] It should be noted that all devices, elements, units and components described in this application can be implemented in software or hardware elements or any type of combination thereof. All steps performed by various entities described in this application and the functions described to be performed by various entities are intended to indicate that the corresponding entities are suitable for or used to perform the corresponding steps and functions.

[0087] Although in the description of the following specific embodiments, the specific functions or steps performed by the external entity are not reflected in the description of the specific detailed elements of the entity that performs the specific steps or functions, the technician should be aware that these methods and functions can be implemented in corresponding software or hardware elements or any type of combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] In conjunction with the attached drawings, the following description of specific embodiments will illustrate the above aspects and their implementation methods. In the drawings:

[0089] Figure 1 An example of an apparatus for generating a signal according to the present disclosure is shown;

[0090] Figure 2 An example of an initial pilot sequence and a first pilot sequence according to the present disclosure is shown;

[0091] Figure 3 An example of orthographic projection matrix generation according to the present disclosure is shown;

[0092] Figure 4 An example of a transmitter according to the present disclosure is shown;

[0093] Figure 5 Another example of a transmitter according to the present disclosure is shown;

[0094] Figure 6 An example of calculating the center frequency of a frequency band to be zeroed according to the present disclosure is shown;

[0095] Figure 7 A schematic diagram showing a method for generating a signal according to the present disclosure is shown;

[0096] Figure 8 An example of a device according to the present disclosure is shown;

[0097] Fig. 9 An example of the bandwidth relationship between signals having the same length at the input and output of an IDAFT module is shown;

[0098] Fig.10 shows an example of the bandwidth relationship between signals having different lengths at the input and output of an IDAFT module;

[0099] Fig.11 An example of a communication system according to the present disclosure is shown. DETAILED DESCRIPTION

[0100] Next generation wireless systems are expected to operate on many frequency bands (including those centered around VHF carriers) and serve users in high mobility scenarios. AFDM is a new waveform that can improve transmission performance in both use cases. AFDM is based on DAFT (or IDAFT) and can be used to generate multi-chirp signals characterized by multiple adjustable parameters.

[0101] When using N DAFT Point IDAFT module from the sample Generate signal in When , the signal can be expressed as the following equation:

[0102]

[0103] The adjustable parameters for generating a multi-chirp signal can be found in (c1, c2) in Equation 1. DAFT The signal generated by IDAFT can satisfy

[0104] Continuous-time affine Fourier transform (AFT) of the parameter matrix [a, b; c, d] of the signal f(t) It can be expressed as the following equation:

[0105]

[0106] When the Fourier transform (FT) is [a2, b2; c2, d2] = [0, 1; -1, 0], the AFT and Fresnel transform (FnT) are AFT at , where α is the chirp rate. The DAFT is a possible discretization of FnT. The composite (additive) property of AFT determines that the composite of two affine Fourier transforms with their respective parameter matrices [a1, b1; c1, d1] and [a2, b2; c2, d2] is an AFT with the following parameter matrix

[0107] Using the additive property of AFT, the FT applied to FnT is a composite AFT Its parameter matrix is:

[0108]

[0109] With FT The composite AFT of the signal f(t) As shown below:

[0110]

[0111] Therefore, if the signal f(t) has finite bandwidth in the variable of the composite transform (that is, if the signal f(t) satisfies has some finite support), then the signal satisfies have the same finite support. That is, f(t) has finite bandwidth in the frequency domain.

[0112] In discrete time, this means that if The sequence at the input of the IDAFT module is The spectrum in the frequency band (at digital frequency) is zero, the signal at the output of the IDAFT module The spectrum will have the same frequency bands (v1, v2) as support. Fig. 9 Shown in.

[0113] In another case, the sequence at the input of the IDAFT module has N non-zero values ​​{s m} m＝0…N-1 , and N <N DAFT The N non-zero values ​​{s m} m＝0…N-1 N occupies IDAFT module DAFT The consecutive (uninterrupted) positions of the long sequence input. In this case, if the shorter sequence {s m} m＝0…N-1 The N-point DFT has frequency bands (at digital frequency) as support, the signal at the output of the IDAFT module Most of the power of can be approximately (but not exactly) contained in the same interval (ν1, ν2) at the digital frequency, as Fig.10 As shown. <N DAFT The approximate nature of this relationship is due to the fact that N DAFT The power in the long sequence spectrum leaks out of the frequency range (ν1,v2), and this leakage is caused by the addition of N non-zero values ​​{s m} m＝0…N-1Zero padding is caused when zeros are added to form the sequence.

[0114] Some aspects of the present disclosure relate to generating a sequence value {s m} m＝0…N-1 The DAFT domain pilot signal can be designed so that this leakage in the spectrum of the pilot signal can be minimized.

[0115] Figure 1 A device for generating a signal according to the present disclosure is shown. The device 100 is used to obtain a first pilot sequence 110 according to a sequence length and a frequency bandwidth. The first pilot sequence 110 includes a set of pilot symbols.

[0116] Optionally, the device may be a transmitter or a part of a transmitter. The transmitter may be one of a plurality of user terminals that transmits signals in an uplink channel of a cellular network. The transmitter may also be a base station or access point that transmits signals in a downlink channel of a cellular network. Optionally, the cellular network may be a fourth generation (4G) network, a 5G network, a 6G network or any variation thereof.

[0117] Optionally, the first pilot sequence can be obtained by any conventional method for generating a pilot sequence of a cellular network. p The frequency bandwidth W<1 at the digital frequency can be determined according to system requirements and / or the configuration of the cellular network. For example, the sequence length can be set according to the minimum value of the frequency bandwidth that the sequence must occupy, so that the larger the length, the smaller the bandwidth, and the frequency bandwidth can be at least equal to the channel bandwidth of the channel to be estimated. Optionally, in order to obtain a channel estimate for the frequency band allocated to the data signal, a bandwidth at least the same as the bandwidth of the data signal can be allocated to the first pilot sequence. The pilot symbols included in the first pilot sequence can be used by the receiver to obtain a channel estimate.

[0118] The device is also used to obtain multiple chirp signals. The number of the multiple chirp signals is equal to the first sequence length. The device is also used to generate a linear combination of the multiple chirp signals to obtain a second pilot sequence, wherein the set of first pilot symbols is used as linear combination coefficients.

[0119] Optionally, the chirp signal can be determined by the device for the AFDM waveform. Each chirp signal can be characterized by a pair of parameters (c1, c2). In the present disclosure, multiple chirp signals are used, and the number of chirp signals is equal to the sequence length of the first pilot sequence. The pilot symbols included in the first pilot sequence are used as linear combination coefficients to linearly combine the multiple chirp signals to obtain the second pilot sequence.

[0120] The obtained second pilot sequence is a pilot sequence to be sent by the device for channel estimation of the receiver. The obtained second pilot sequence can be spectrally shaped to fit the target spectrum occupancy equal to W<1 (at digital frequency) and has a length N p The finite support of length N p Can be much smaller than the DAFT domain size N DAFT It should be noted that the frequency bandwidth W used in the present disclosure should be understood as a relative bandwidth relative to the entire bandwidth.

[0121] Figure 2 An example of an initial pilot sequence and a first pilot sequence according to the present disclosure is shown. Figure 2 The initial pilot sequence has only one non-zero sample and 15 zero samples (N p =16). Such a sequence is not frequency-band-restricted, and its 16-point DFT has a non-zero constant amplitude. If the samples of the initial pilot sequence are used as linear combination coefficients to generate a second pilot sequence, the second pilot sequence will include a chirp signal (corresponding to a non-zero sample of the first sequence), and thus will not be frequency-band-restricted.

[0122] Figure 2 Another example of a first pilot sequence is shown, labeled "Spectrum Shaping Pilot Sequence in DAFT Domain". The first pilot sequence in this example is generated in such a way that most of the energy of the 16-point DFT of the sequence is concentrated in a sub-band of width W<1 (in digital frequency) centered at zero frequency. When these samples of the first pilot sequence are used as linear combination coefficients to generate a second pilot sequence, the second pilot sequence can include a linear combination of multiple (e.g., 16) chirp signals and can concentrate most of its energy in a sub-band of width W<1 (in digital frequency) centered at zero frequency. In this way, the second pilot sequence can be frequency band limited.

[0123] Optionally, in order to generate a linear combination of multiple chirp signals, the device may be configured to map the first pilot sequence to N of the IDAFT modulation module. p The IDAFT modulation module can be the device or a part of the device. The IDAFT modulation module can be used to perform N DAFT Point IDAFT. The IDAFT operation performed by the IDAFT modulation module can be regarded as a linear combination, which can be expressed as follows:

[0124]

[0125] As shown in Equation 7, represents the first pilot sequence, p mrepresents the mth pilot symbol included in the first pilot sequence, represents the mth chirp signal, u n represents the nth time domain sample included in the second pilot sequence, represents the second pilot sequence.

[0126] Optionally, before generating the linear combination of the plurality of chirp signals, the device may be configured to shift the first pilot sequence in the frequency domain by element-wise multiplying the first pilot sequence with a frequency shift vector according to the frequency value.

[0127] The frequency shift vector can be defined as:

[0128]

[0129] Among them, ν c Indicates frequency value. The device can be used to calculate:

[0130]

[0131] where ⊙ represents element-wise (or Hadamard) multiplication.

[0132] In this way, the first pilot sequence and the obtained second pilot sequence may have a frequency value v c The signal bandwidth centered at . This frequency value can be the center frequency of the channel to be estimated.

[0133] In order to obtain the first pilot sequence, the device can be used to obtain the initial sequence according to the sequence length. For example, the device can determine the pilot value p according to a preset function of high-level parameters such as the cell ID and the scrambling sequence. ini . Given a sequence length N p , the device can use N p – 1 zero fills the value p ini , to form N p Entry vector p ini =[p ini ,0,0,0…0] T As the initial sequence. The device can also be used to obtain multiple projection sequences. Each projection sequence is N p It should be understood that defining a sequence as a bandwidth constrained within the frequency bandwidth (–W / 2, W / 2) means that the N pMost of the point DFT is concentrated in the digital frequency band (–W / 2, W / 2). Multiple projection sequences can be used as columns to form a projection matrix P. Since the columns of the projection matrix P are orthogonal, the projection matrix P can also be called an orthogonal projection matrix P, that is, the initial sequence is projected onto the frequency bandwidth (–W / 2, W / 2) span and the projection sequence is kept orthogonal. In general, the device can be used to calculate To obtain the first pilot sequence.

[0134] Figure 3 An example of orthogonal projection matrix generation according to the present disclosure is shown. The orthogonal projection matrix is ​​selected as It is N p Point DFT Matrix The columns of the DFT matrix correspond to the interval The digital frequency within. Then based on structure like Figure 3 shown.

[0135] The device can be used to convert the initial sequence into a projection matrix PP H Left multiplication generates an orthogonal projection of the initial sequence on the span of multiple projection sequences to obtain the first pilot sequence.

[0136] Due to the time-frequency positioning characteristics of the columns of the DFT matrix, based on N p The orthogonal projection matrix P generated by the point DFT matrix is p The value is valid. Alternatively, the orthogonal projection matrix can be generated based on a discrete prolatespheroidal sequence (DPSS). DPSS can also be called a Slepian sequence. That is, the multiple projection sequences can be DPSS corresponding to the sequence length and frequency bandwidth.

[0137] Given a sequence length N and a frequency bandwidth W∈(0,1) at digital frequency, (N,W)-DPSS consists of N vectors, which are long matrices B N,W The eigenvectors of the long matrix are (m,n) entries:

[0138]

[0139] Given an approximation parameter ∈ < 1, the N vectors can be arranged into a matrix S N,W The columns are defined as follows:

[0140]

[0141] Can be used as the projection matrix P. Project the vector x of signal samples to the front The projection matrix The columns of the (N,W)-DPSS vector with good spectral containment will generate the signal As the first pilot sequence, the sequence Only ∈ power content is available. Compared with the columns, The columns have better time-frequency positioning. Therefore, for the same N p The first pilot sequence generated based on DPSS can better Internal positioning. Figure 2 The spectral shaping pilot sequence shown is generated based on DPSS.

[0142] It should be noted that the orthogonal projection operation (based on the DFT matrix or DPSS) for pilot sequence generation can be implemented as an "online" mode or an "offline" mode. In the "online" mode, the orthogonal projection can be performed by an actual module of the device, which calculates the projection result "online" each time a frame of the signal to be transmitted is generated. Alternatively, in the "offline" mode, the device may not be used to perform the projection step. Instead, the device can be used to obtain the result of the projection, that is, the sequence length N p and the first pilot sequence in the lookup table indexed by the parameter of the frequency bandwidth W. In the "offline" mode, for multiple different parameters N p and W (assuming p ini =1 and v c =0), the above sequence generation method (based on DFT matrix or DPSS) can be used to pre-generate different first pilot sequences. p and band limited to the digital frequency range When the second pilot sequence is within p When the values ​​of and W are in the lookup table, the projection result can be expressed in the lookup table as p(N p ,W). The first pilot sequence can be calculated by the device as In the combination of values ​​(N p ,W) is not in the lookup table, the first pilot sequence is calculated "online" by the device using the above-mentioned orthogonal projection method.

[0143] The device may also be used to map the first pilot sequence to a continuous input of the IDAFT modulation. The device may also include an IDAFT module adapted to perform the IDAFT modulation. The first pilot sequence is a pilot sequence in the DAFT domain. In order to send the first pilot sequence, it is necessary to map it to an input of the IDAFT module and transform it into a signal in the time domain.

[0144] Optionally, the device can be used to obtain multiple first pilot sequences. When there are multiple first pilot sequences to be sent, the bandwidth of the multiple pilot sequences is limited to multiple non-overlapping frequency bands, and the multiple first pilot sequences can be mapped to the same or overlapping inputs of IDAFT modulation without losing orthogonality. Because on the receiver side, the received samples can be separated in the frequency domain. When the bandwidth of multiple first pilot sequences is limited to the same frequency band, the multiple first pilot sequences need to be mapped to non-overlapping inputs of IDAFT modulation to ensure their orthogonality. Multiple first pilot sequences can be used in various scenarios. For example, it may be necessary to send several pilot sequences with bandwidth limited to non-overlapping frequency band bandwidths from the downlink to the user terminal or from the uplink to the user terminal, where these non-overlapping frequency bands are allocated to the user terminal. In addition, even for the same frequency band, more than one pilot sequence may be required. For example, in multi-user multiple-input multiple-output (MU-MIMO) technology, on the same frequency band, there may be signals sent from different antenna ports of a multi-antenna user terminal or signals sent to different antenna ports of a multi-antenna user terminal or signals sent from a multi-antenna base station to different user terminals, wherein the signals are multiplexed in a specific domain using MU-MIMO technology. Another example of using multiple first pilot sequences is that when the effective DAFT domain channel changes relative to the DAFT domain index due to mobility, tracking the effective DAFT domain channel requires multiple first pilot sequences within the DAFT domain frame. In the latter case, the N first pilot sequences of one first pilot sequence are multiplexed in a specific domain using MU-MIMO technology. p symbols are not enough to estimate N in the DAFT domain DAFT ×N DAFT All entries of the effective channel matrix. In this case, multiple (for example, N PS >1) The first pilot sequence is mapped to the N of the IDAFT modulation module PS Group Continuous N p enter.

[0145] In the present disclosure, the device may also be used to perform the following pilot sequence transmission method. Assume that there are N PS (N PS >1) first pilot sequences are transformed and transmitted as in the second pilot sequence, and the bandwidth of each first sequence / second sequence is limited to N B (N PS ≥N B ) non-overlapping frequency bands (Each For an interval ) within one of the devices. The device can be used to PS The first sequence is divided into N G Group (N G ≤N PS ), each group contains at most N B sequences, each of which belongs to a different frequency band The device can be used to: use the same initial pilot value p ini Or different initial pilot values ​​p for different first pilot sequences ini , and for each sequence, an orthogonal projection matrix P customized for the target frequency band is used to generate the first pilot sequence. According to the requirements of the high-level layer, the first pilot sequence can have the same length N p , can also have different lengths, N p,max N PS The device can be used to strictly less than N length of the pilot sequence. p,max The first pilot sequence is zero-filled to make its length equal to N p,max . In the obtained N p,max In the long first pilot sequence, the device can be used to (g∈{1,…,N G}) to form an N p,max Long Sequence The device can be used to convert each p g (g∈{1,…,N G}) is mapped to IDAFT modulation A collection of continuous inputs The device can be used to select these sets so that for all g1≠g2, Thus, the orthogonality of all transmitted second pilot sequences generated based on the first pilot sequence is guaranteed.

[0146] Figure 4 An example of a transmitter 400 according to the present disclosure is shown. The transmitter 400 may be used to generate an AFDM signal based on one or more sets of data symbols. The multiple sets of data symbols may be for multiple user terminals or for multiple antennas of a terminal. The transmitter 400 may be the device 100. Alternatively, the device 100 may be a part of the transmitter 400. For example, the transmitter 400 may be a modulator within a baseband circuit of the transmitter. The transmitter may be a base station (or access point) transmitting in a downlink of a wireless system, a user terminal transmitting in an uplink, or a user terminal transmitting to another user terminal in a sidelink.

[0147] The transmitter 400 may include at least one zeroing module 410, at least one N FFT point IDFT module 420, at least one pilot sequence generation module 430, N DAFTThe arrows connecting these modules represent the signal flow. FFT and N DAFT are all positive integers, and N FFT <N DAFT .

[0148] exist Figure 4 In, N PS The first pilot sequences are generated by the pilot sequence generation module 430 and then mapped to the N inputs of the IDAFT module 440 of the transmitter. G non-overlapping subsets. Figure 1 , each first pilot sequence is transformed into a corresponding second pilot sequence. Non-pilot data such as data or control message symbols are first grouped into N s Blocks or sub-symbols. Grouped symbols use N FFT Point IDFT module (N FFT <N DAFT ) is precoded. The sth IDFT module (s∈{1,…,N s}) is mapped to the output of IDAFT module 440 A collection of consecutive inputs Select these collections So that for all s1≠s2, For all s∈{1,…,N s} and g∈{1,…,N G}, That is, the data symbols and pilot sequences are mapped to non-overlapping inputs of the IDAFT module. The spectrum shaping of the data symbols is performed by the zeroing module 410. The zeroing module 410 is used to set specific inputs of the IDFT module to zero (zeroing). In this way, the bandwidth of the time domain samples of the data symbols can be limited to the target frequency range. (under digital frequency). Zero input refers to the frequency band Digital frequencies other than N FFT Input in input.

[0149] The following example uses an example to determine the input k∈{0,…,N FFT -1} falls within the target frequency range. Calculate v defined in the following equation k :

[0150]

[0151] By doing so, the IDFT module 440 can generate most of the power in the digital frequency range. The time domain signal inside.

[0152] Select each transfer time c and the value of W, so that in, is the target bandwidth of the entire system (in Hz), T s is the sampling period of DAC 460. Any N FFT Each non-zeroed input of the IDFT module 440 corresponds to a digital frequency band In other words, satisfy Each value k∈{0,…,N FFT -1}(where v k The resource elements used for data or control message transmission in AFDM can be defined in the above equation. FFT The resource elements at the input of the IDFT module are grouped to form an AFDM physical resource block (PRB), each of which includes a predefined number of For example, in 4G (e.g., LTE) and 5G (e.g., NR) systems, Equal to 12. These resource blocks can be used as building blocks of physical transport channels and can have the same role as the physical downlink shared channel (PDSCH), physical downlink control channel (PDCCH), physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH), physical sidelink shared channel (PSSCH), and physical sidelink control channel (PSCCH) associated with LTE and 5G NR in the 3GPP standard.

[0153] Figure 5Another example of a transmitter 500 according to the present disclosure is shown. Similar to the DFT spread OFDM technique, the transmitter 500 can be used to generate a DFT spread AFDM signal based on a set of data symbols. The transmitter 500 can be the device 100, or the device 100 can be a part of the transmitter 500. For example, the transmitter 500 can be a modulator within a baseband circuit of the transmitter. The transmitter can be a base station (or access point) transmitting in a downlink of a wireless system, a user terminal transmitting in an uplink, or a user terminal transmitting to another user terminal in a sidelink.

[0154] The transmitter 500 may include a zeroing module 510, N FFT point DAFT module 520, at least one pilot sequence generation module 530, N DAFT The arrows connecting these modules represent the signal flow. FFT and N DAFT are all positive integers, and N FFT <N DAFT .

[0155] exist Figure 5 In, N PS The first pilot sequences are generated by the pilot sequence generation module 530 and mapped to the N inputs of the IDAFT module 540. g Non-overlapping subsets are transmitted as the second pilot sequence. Non-pilot data such as data or control message symbols are first transmitted using N FFT Point DAFT module 520 (N FFT <N DAFT ) is precoded. The output of DAFT module 520 is then mapped to N DAFT Point IDAFT module 540 A collection of consecutive inputs Choose this set so that for all g∈{1,…,N G}, For the allocation to N DAFT Any of the concurrent transmissions in the set of inputs to the IDAFT module 540 The spectrum shaping of the data symbol is performed by the zeroing module 410. The zeroing module 410 is used to set the specific input of the IDFT module to zero (zeroing). In this way, the bandwidth of the time domain samples of the data symbol can be limited to the target frequency range. Internal (at digital frequency).

[0156] when And N FFT The samples at the input of the DAFT module are When , the time domain sample of DAFT-s-AFDM signal is:

[0157]

[0158] in,

[0159] In Equation 13, g k represents a Dirichlet pulse, symbol Represents modular operation, that is, X modulo N DAFT Due to the time domain chirp (the multiplication term in Eq. 13 ), N in the summation FFT Each of the Dirichlet pulses occupies a portion of the total bandwidth that is shifted relative to the frequency band occupied by its two adjacent pulses in the sum by an amount equal to % of the total bandwidth. The total bandwidth is equal to the sampling rate of the DAC 460. This means that there is a bandwidth overlap between the frequency bands of two consecutive Dirichlet pulses in the summation, and the non-overlapping portion is equal to 1 / 2 of the total bandwidth. Therefore, the spectrum of the data portion of the DAFT-s-AFDM signal is shaped (i.e., the bandwidth of the time domain samples of the data portion of the signal is limited to the frequency range (at digital frequencies)), this can be accomplished by zeroing specific pulses in the summation, e.g., by FFT The sample sequence at the input of the DAFT module 520 is The specific sign of is set to zero. Since the frequency band shift of two adjacent pulses is equal to the total bandwidth Therefore the number of zeroing inputs should be approximately equal to in, represents the nearest integer greater than a (a is a real number). The following discloses how to determine the specific input to be zeroed. First, the symbol Indicates frequency band Center frequency The symbol “\” represents the set difference operator. More precisely,

[0160]

[0161] Defined.

[0162] In Equation 14, the symbol (X)1 represents an analog modulo operation of 1. The center frequency of the frequency band to be zeroed is It can be defined as follows:

[0163]

[0164] Figure 6An example for calculating the center frequency of a frequency band to be zeroed is shown.

[0165] To find the specific input to be zeroed, follow these steps:

[0166] 1. Find the chirped pulse The input index n0∈{0,…,N FFT -1}, the chirped pulse satisfies its spectrum with n=0…N FFT All chirped pulses at -1 The frequency closest to The frequency is centered.

[0167] 2. For each Settings n =0, where

[0168] 3. For each Settings n =0, where

[0169] and Figure 5 Similar to AFDM in , the system target bandwidth of the DAFT-s-AFDM system at digital frequency can be specified as W sys , in Hz, The DAFT-s-AFDM system is set up when all concurrent transmissions are allocated frequency bands. That is, W = W sys And v c = 0, for different concurrent transmissions, the precoding module size N FFT may have different values. In this case, use N FFT The number of non-zeroed inputs to the precoding module of the user of the point DAFT precoder is approximately W sys N FFT Each non-zeroed input to any one of the DAFT modules 520 defines a resource element in the DAFT-s-AFDM for data transmission or control message transmission. Resource elements at the input of the same DAFT module 520 may be grouped to form a DAFT-s-AFDM PRB. Each PRB includes a predefined number of consecutive resource elements. For example, in 4G (LTE) and 5G (NR) systems These PRBs can be used as building blocks of physical transport channels and can have the same role as PUSCH, PUCCH, PSSCH and PSCCH in LTE and NR related standards.

[0170] Figure 7A schematic diagram of a method 700 for generating a signal according to the present disclosure is shown. The method 700 comprises the following steps:

[0171] - Step 701: The device acquires a first pilot sequence according to a sequence length and a frequency bandwidth, wherein the first pilot sequence includes a set of pilot symbols.

[0172] - Step 702: The device acquires a plurality of chirp signals, wherein the number of the plurality of chirp signals is equal to the sequence length.

[0173] - Step 703: The device generates a linear combination of a plurality of chirp signals to obtain a second pilot sequence, wherein a set of pilot symbols is used as linear combination coefficients.

[0174] From the above Figures 1 to 6 From the perspective of FIG. 7 , the steps of method 700 may share the same functions and details. Therefore, the corresponding method implementation will not be described in detail here.

[0175] Figure 8 An example of a device 800 according to the present disclosure is shown. The device 800 may be a computer-implemented device for generating a signal according to the present disclosure. The device 800 may include at least one processor 802. The at least one processor 202 may include one or more of various processing units, such as a processing core, a microprocessor, a controller, a digital signal processor (DSP), a processing circuit including or not including an accompanying DSP, or various other processing devices including integrated circuits, including application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), microcontroller units (MCUs), hardware accelerators, dedicated computer chips, etc.

[0176] The device 800 may also include at least one memory 804. The memory 804 may be used to store computer program code 806, etc. The memory 204 may include one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the memory may be embodied as a magnetic storage device (e.g., a hard disk drive, a solid-state drive, a magnetic tape, etc.), an optical magnetic storage device, or a semiconductor memory (e.g., a mask ROM, a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, a random access memory (RAM), etc.). When the computer program code 806 is executed by at least one processor 802, the device 800 is used to generate a reference Figures 1 to 7 The signal described.

[0177] The device 800 may also include a communication interface 808, which is used to enable the device 800 to send and / or receive signals. The communication interface 808 may include an internal communication interface, for example, an interface between a baseband circuit and a radio frequency (RF) circuit of a transmitter or transceiver device. Optionally or additionally, the communication interface 808 can be used to provide at least one external wireless connection, for example, a 3GPP mobile broadband connection (e.g., 3G, 4G, 5G, and 6G); a wireless local area network (WLAN) connection, for example, standardized by the IEEE 802.11 series or the Wi-Fi Alliance; a short-range wireless network connection, for example, a Bluetooth connection. Therefore, the communication interface 808 may include one or more antennas to enable the transmission and / or reception of radio frequency signals over the air.

[0178] For example, device 800 may include a modulator chip, a demodulator chip, a baseband chip, a mobile phone, a tablet computer, a laptop computer, an IoT device, a base station, etc. Although device 800 is shown as a single device, it should be understood that the functionality of device 800 may be distributed to multiple devices, for example, between components of a transmitter or a transceiver, where applicable.

[0179] Fig.11An example of a communication system 1100 according to the present disclosure is shown. The communication system 1100 may include at least one transmitter 1110 and at least one receiver 1130. The transmitter 1110 and the receiver 1130 communicate via a transmission channel 1120. The transmitter 1110 generates a transmit signal x[m] based on a set of input symbols s[m]. The transmitter 1110 may generate a multi-chirp signal characterized by IDAFT coefficients (c1, c2), which may be set relative to certain performance criteria. The coefficients (c1, c2) may generally be understood as IDAFT (or DAFT) parameters. For example, these coefficients may be selected so that the frequency sweep range of each chirp signal is large enough to provide sufficient frequency diversity and so that the performance degradation caused by Doppler spread is mitigated.

[0180] The transmission signal x[m] is fed through the transmission channel 1120, which can be modeled by an impulse response h[l]. The impulse response h[l] may include L paths, l∈{1,…,L}. Each of the L paths may be associated with a delay τ l and Doppler shift v l Such a channel may be referred to as a dual dispersion channel. The delay-Doppler characteristics of the transmission channel 1120 may include the delays and Doppler shifts of different paths of the channel impulse response h[l]. Noise may be modeled by adding additive white Gaussian noise η after the transmission channel 1120. The receiver 1130 may determine an estimate of the input symbol based on the received signal r[m].

[0181] The discrete time waveform of the AFDM signal can be expressed as:

[0182]

[0183] When n=0, 1, ..., N-1, the input symbol s[m] comes from the set of (real or complex) input symbols, and N is the maximum number of chirp signals, for example, the upper limit of modulating orthogonal chirp signals. The chirp signal w[m,n] may include or be based on the term in, e is the Euler number e≈2.71828. The chirp signal can be represented by a binary polynomial p(m,n) with an input symbol index m and a chirp signal time index n. The polynomial p(m,n) can include a binary quadratic polynomial, i.e., a second-order binary polynomial. The time-discrete signal x[n] can be represented by the corresponding time-continuous signal defined for 0≤t≤T Sampling is performed to obtain, when n=0,1,…,N-1, the sampling point is

[0184] The AFDM signal can be represented by the following basis functions, for example:

[0185]

[0186] Therefore, the bivariate polynomial p(m,n) can be applied to the exponential term of the complex exponential function. However, it should be noted that any other suitable factor can be used instead of or in addition to the normalization factor

[0187] In general, a bivariate polynomial can be expressed as f(x,y)=a1x 2 +a2y 2 +a3xy+a4x+a5y+a6, where a1 to a6 are the coefficients of the different terms in the polynomial. The order of a term can be defined as the sum of the exponents of the terms. Therefore, the quadratic polynomial f(x,y) = a1x 2 +a2y 2 +a3xy+a4x+a5y+a6 includes three second-order coefficients a1 to a3, two first-order coefficients a4 and a5, and a zero-order coefficient a6, i.e., a scalar term. A quadratic term may refer to a term raised to the second power. Thus, the above quadratic polynomial includes the first quadratic term a1x with a coefficient a1 for the variable x. 2 The second quadratic term a2y of variable y with coefficient a2 2 If at least one coefficient of at least one of the quadratic terms of a bivariate polynomial is nonzero, then the bivariate polynomial is a bivariate quadratic polynomial.

[0188] The bivariate polynomial p(m,n) that characterizes the chirp signal w[m,n] can include By selecting appropriate first coefficient c1 and second coefficient c2, the tolerance of the generated AFDM waveform to impairments in a dual-dispersion (ie, time-varying) channel can be improved.

[0189] In the present disclosure, the transmitter 1110 is also used to generate the above-mentioned Figures 1 to 7 For example, the second pilot sequence and data symbols generated according to the present disclosure can be mixed and used together as Fig.11 The receiver 1130 uses the second pilot sequence to estimate the channel impulse response h[l]. Then, the receiver performs a channel impulse response calculation on the input symbol based on the estimated channel impulse response. Decode (or estimate).

[0190] By changing several parameters, namely, the number of zeroed subcarriers for data or control messages, and the parameter N used to generate the orthogonal projected pilot sequence (i.e., the first pilot sequence), p and W, the bandwidth of the signal generated according to the present disclosure can be easily controlled.

[0191] To decode signals generated according to the present disclosure, only low complexity changes need to be made at the receiver 1130. For example, the receiver 1130 may be configured to discard samples received at zeroed subcarrier locations when detecting data that has not been spectrally shaped.

[0192] Different from the conventional method of using a single chirp signal to send a pilot sequence, the present disclosure uses pilot symbols in the pilot sequence to linearly combine multiple chirp signals. The obtained second pilot sequence is bandwidth controllable and does not span the entire bandwidth.

[0193] In general, the present disclosure relates to generating a pilot sequence in the DAFT domain (e.g., over the span of a subset of a DFT or Slepian basis) using orthogonal projection to generate a pilot signal. The pilot signal can be spectrally shaped to fit a target spectrum occupancy equal to W<1 at digital frequencies while having a length N much smaller than the DAFT domain size. p Limited support. That is, the second pilot sequence generated in the present disclosure can be regarded as a pilot signal based on spectrum shaping chirp. When multiple second pilot sequences are generated, these multiple second pilot sequences are spectrally shaped respectively and are orthogonal to each other. The pilot sequence generated in the DAFT domain is mapped to certain inputs of the IDAFT module of the transmitter for transmission. For example, symbols belonging to different pilot sequences and having non-overlapping support in the frequency domain can be mapped to the same input of the IDAFT module. Pilot sequences with partially or completely overlapping support in the frequency domain can be mapped to different inputs of the IDAFT module to ensure orthogonality. The pilot sequence generated in the DAFT domain can also be multiplexed with data symbols and transmitted as input to the IDAFT module. In order to ensure that data (e.g., user data or control data) including data symbols and pilot signals have target spectrum occupancy, one possible way is to use an IDFT module to precode data symbols, wherein the specific input of the IDFT module is set to zero. Another possible way is to use a DAFT module to precode data symbols, wherein the specific input of the DAFT module is set to zero. Each non-zeroed input to any of the IDFT and DAFT modules defines a resource element for data transmission. Resource elements from the same IDFT module or the same DAFT module are grouped to form PRBs, each of which includes a predefined number of consecutive resource elements.

[0194] The present disclosure has been described in conjunction with various embodiments as examples and implementations. However, from a study of the drawings, the present disclosure and the independent claims, a person skilled in the art will be able to understand and implement other variations when implementing the claimed subject matter. In the claims and in the specification, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" and "an" do not exclude a plurality. A single element or other unit may fulfil the functions of several entities or items described in the claims. The listing of certain measures in mutually different dependent claims does not indicate that a combination of these measures cannot be effectively used.

Claims

1. A device (100) for generating a signal, wherein: The device (100) is used for: Acquire a first pilot sequence (110) according to the sequence length and the frequency bandwidth, wherein the first pilot sequence (110) includes a set of pilot symbols; Acquiring a plurality of chirp signals (130, 150), wherein the number of the plurality of chirp signals (130, 150) is equal to the sequence length; A linear combination of the plurality of chirp signals (130, 150) is generated to obtain a second pilot sequence (120), wherein the set of pilot symbols is used as linear combination coefficients.

2. The device (100) according to claim 1, wherein In order to generate the linear combination of the plurality of chirp signals (130, 150), the device (100) is configured to map the first pilot sequence (110) to a continuous input of an Inverse Discrete Affine Fourier Transform (IDAFT) modulation.

3. The device (100) according to claim 1 or 2, wherein: Before generating the linear combination of the plurality of chirp signals (130, 150), the device (100) is configured to: The first pilot sequence (110) is shifted in the frequency domain by element-wise multiplying the first pilot sequence (110) with a frequency shift vector according to a frequency value.

4. The device (100) according to any one of claims 1 to 3, wherein: The device (100) is used to: use the sequence length and the frequency bandwidth as indexes to obtain the first pilot sequence (110) through a predefined lookup table.

5. The device (100) according to any one of claims 1 to 3, wherein: The device (100) is used to obtain the first pilot sequence (110) in the following manner: Acquire an initial sequence according to the sequence length; Acquire a plurality of projection sequences, wherein each projection sequence in the plurality of projection sequences has the same sequence length as the initial sequence, and a bandwidth is limited within the frequency bandwidth; By combining the initial sequence with the projection matrix PP H Left multiplication generates an orthogonal projection of the initial sequence on the span of the multiple projection sequences to obtain the first pilot sequence (110), wherein the columns of the matrix P are the multiple projection sequences.

6. The device (100) according to claim 5, wherein: In order to obtain the initial sequence, the device is configured to generate the initial sequence based on a cell identifier and / or a scrambling sequence.

7. The device (100) according to claim 5 or 6, wherein: The plurality of projection sequences include a discrete prolate ellipsoid sequence corresponding to the sequence length and the frequency bandwidth.

8. The device (100) according to claim 5 or 6, wherein: The plurality of projection sequences includes columns of a discrete Fourier transform matrix corresponding to the sequence length and the frequency bandwidth.

9. The device (100) according to any one of claims 1 to 8, wherein: The device (100) is also used for: Acquire a plurality of the first pilot sequences whose bandwidths are limited to non-overlapping frequency bands; The plurality of the first pilot sequences are provided as the same input or overlapping inputs for IDAFT modulation.

10. The device (100) according to any one of claims 1 to 9, wherein: The device is also used for: Acquire a plurality of the first pilot sequences whose bandwidth is limited within an overlapping frequency band; The plurality of the first pilot sequences are provided as non-overlapping inputs for IDAFT modulation.

11. The device (100) according to any one of claims 1 to 10, wherein: The device is also used for: Get a collection of data symbols; Provide the set of data symbols as N FFT The input of the point inverse discrete Fourier transform IDFT; The N FFT Set one or more data symbols of the input of the IDFT to zero and obtain the N FFT Point to the output of IDFT; Provide the N FFT The output of the IDFT and the first pilot sequence (110) are aggregated as N DAFT Point to the input of IDAFT to obtain the N DAFT The output of IDAFT, where N FFT Less than N DAFT .

12. The device (100) according to any one of claims 1 to 10, wherein: The device is N DAFT A discrete point affine Fourier transform extended affine radio frequency division multiplexing (DAFT-s-AFDM) transmitter, wherein the transmitter is further used for: Get a collection of data symbols; Provide the set of data symbols as N FFT Click DAFT input; The N FFT Set one or more data symbols of the input of the DAFT to zero and obtain the N FFT Click the DAFT output; Provide the N FFT The output of the DAFT and the first pilot sequence (110) are aggregated as N DAFT Point to the input of IDAFT to obtain the N DAFT The output of IDAFT, where N FFT Less than N DAFT .

13. The device (100) according to any one of claims 1 to 12, wherein: The first pilot sequence (110) is a downlink demodulation reference signal or a channel state information reference signal.

14. The device (100) according to any one of claims 1 to 12, wherein: The first pilot sequence (110) is an uplink demodulation reference signal or a sounding reference signal.

15. A method (700) for generating a signal, wherein: include: The device acquires (701) a first pilot sequence according to the sequence length and the frequency bandwidth, wherein the first pilot sequence includes a set of pilot symbols; The device acquires (702) a plurality of chirp signals, wherein the number of the plurality of chirp signals is equal to the sequence length; The device generates (703) a linear combination of the plurality of chirp signals to obtain a second pilot sequence, wherein the set of pilot symbols is used as linear combination coefficients.

16. A computer program product comprising instructions, wherein: When the program is executed by a computer, the computer is caused to execute the method (700) according to claim 15.

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