WO2021171707A1 - Transmission device, reception device, communication method, and baseband chip that use highly accurate channel estimation scheme in communication using otfs modulation - Google Patents

Transmission device, reception device, communication method, and baseband chip that use highly accurate channel estimation scheme in communication using otfs modulation Download PDF

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WO2021171707A1
WO2021171707A1 PCT/JP2020/041186 JP2020041186W WO2021171707A1 WO 2021171707 A1 WO2021171707 A1 WO 2021171707A1 JP 2020041186 W JP2020041186 W JP 2020041186W WO 2021171707 A1 WO2021171707 A1 WO 2021171707A1
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signal
time
delay
otfs
frequency
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PCT/JP2020/041186
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French (fr)
Japanese (ja)
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典征 橋本
昇 大澤
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Kddi株式会社
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes

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  • the present invention relates to a transmitting device, a receiving device, a communication method, and a baseband chip, and more particularly to a technique for improving the accuracy of channel estimation in a wireless communication system using OTFS (Orthogonal Time Frequency and Space) modulation.
  • OTFS Orthogonal Time Frequency and Space
  • OTFS Orthogonal Time Frequency and Space modulation
  • Patent Document 1 OTFS (Orthogonal Time Frequency and Space) modulation
  • the signal detection in the delay-Doppler region is performed by using the channel information in the delay-Doppler region.
  • the present invention provides a technique that enables efficient and realistic channel estimation in the delay-Doppler region.
  • the transmission device includes a first OTFS modulation means that generates a first signal by OTFS (Orthogonal Time Frequency and Space) modulation of a signal in a delay-Doppler region containing data to be transmitted.
  • OTFS Orthogonal Time Frequency and Space
  • Each of the first signal and the second signal obtained by OTFS-modulating a reference signal in which a predetermined value is arranged at a predetermined position in the delay-Doppler region has a predetermined pattern in the time-frequency region.
  • Mapping means for generating a third signal in the time-frequency region by mapping with, a conversion means for converting the third signal into a time signal by Heisenberg conversion, and a transmission means for transmitting the time signal to a receiving device. And have.
  • the receiving device includes a receiving means for receiving a signal from the transmitting device, a conversion means for converting the received signal using Wigner conversion to generate a signal in the time-frequency region, and the time-.
  • the separation means for separating the first component of the reference signal and the second component of the data signal mapped in the time-frequency region in a predetermined pattern, and the first component are OTFS ( Orthogonal Time Frequency and Space) Estimate to perform channel estimation in the delay-Doppler region based on the first OTFS demodating means that demolishes and generates the first signal in the delay-Doppler region.
  • OTFS Orthogonal Time Frequency and Space
  • the second OTFS demodulating means for demodulating the second component by OTFS (Orthogonal Time Frequency and Space) to generate a second signal in the delay-Doppler region, and the second signal. It has an extraction means for extracting a data signal using the result of channel estimation.
  • channel estimation in the delay-Doppler region can be performed efficiently and realistically.
  • FIG. 1 is a diagram showing a configuration example of a wireless communication system.
  • FIG. 2 is a diagram showing a hardware configuration example of a transmitting device and a receiving device.
  • FIG. 3 is a diagram showing a configuration example of a transmission function of the transmission device.
  • FIG. 4A is a diagram showing an example of a reference signal arrangement pattern.
  • FIG. 4B is a diagram showing an example of a reference signal arrangement pattern.
  • FIG. 4C is a diagram showing an example of a reference signal arrangement pattern.
  • FIG. 4D is a diagram showing an example of a reference signal arrangement pattern.
  • FIG. 5 is a diagram showing a configuration example of a transmission function of the receiving device.
  • FIG. 6 is a diagram showing an example of a processing flow in which a reference signal arrangement pattern is shared between a transmitting device and a receiving device.
  • FIG. 1 shows a configuration example of the wireless communication system according to the present embodiment.
  • the wireless communication system includes a transmitting device 101 and a receiving device 102.
  • the transmitting device 101 and the receiving device 102 may be, for example, a combination of a base station device and a terminal device in a cellular communication system.
  • the present invention is not limited to this, and a combination of the transmitting device 101 and the receiving device 102 can be used in any wireless communication system.
  • one transmitting device 101 and one receiving device 102 are shown for the sake of simplicity, but naturally there may be a plurality of transmitting devices and a plurality of receiving devices.
  • the combination of the transmitting device and the receiving device is shown for convenience, the transmitting device may have the function of the receiving device, or the receiving device may have the function of the transmitting device.
  • the transmitting device 101 generates a signal using OTFS (Orthogonal Time Frequency and Space) modulation as a modulation method, and the receiving device demodulates the signal using OTFS demodulation.
  • the transmission device 101 for example, modulates a bit string to be transmitted after error correction coding or the like is performed using QAM or the like to acquire a symbol sequence. Then, the series of QAM symbols is mapped to a two-dimensional region called a delay-Doppler region. After that, OTFS modulation is executed on the symbols mapped in this two-dimensional region.
  • OTFS Orthogonal Time Frequency and Space
  • This modulation uses a two-dimensional inverse symplectic Fourier transform (ISFFT) to transform a signal in the delay-Doppler region into a signal in the time-frequency domain. Then, the time-frequency domain signal obtained by OTFS modulation is converted into a time signal by a generalized inverse Fourier transform (Heisenberg transform).
  • Heisenberg transform is used as the inverse Fourier transform, but other inverse Fourier transforms may be executed.
  • a plurality of frequency elements corresponding to one time element are input to the Heisenberg converter to generate a time signal for one symbol. After that, a Cyclic Prefix (CP) is added to the generated time signal to form a transmission signal.
  • CP Cyclic Prefix
  • this symbol sequence x 0 (i) is mapped to the signal matrix x [k, l] in the two-dimensional delay-Doppler region according to a predetermined rule. Will be done.
  • OTFS modulation is applied to the two-dimensional signal matrix x [k, l].
  • the two-dimensional ISFFT converts a two-dimensional signal in the delay-Doppler region into a two-dimensional signal X [n, m] in the time-frequency region. This conversion is written as follows.
  • W tx [n, m] is a window function.
  • the signal in the frequency domain for each time is converted into the signal in the time domain by Heisenberg conversion, and CP is added to the signal in the time domain.
  • the transmission signal s (t) is generated.
  • the Heisenberg conversion performed here is written as follows. Note that g tx (t) is a transmission pulse forming filter.
  • the transmission signal is received by the receiving device 102 via the transmission line.
  • the received signal at this time is expressed as r (t).
  • the receiving device 102 removes the CP from the received signal r (t) and performs a generalized Fourier transform (Wigner transform) to convert it into a signal Y [n, m] in the time-frequency region.
  • the Wigner transformation corresponds to the inverse transformation of the Heisenberg transformation.
  • the Wigner transform is shown as an example of a generalized Fourier transform, but any conversion method is used as long as it can be used as a positive transform for the inverse Fourier transform executed in the transmitter 101. May be good. In Wigner conversion, a signal in the time domain for one symbol is converted into a signal in the frequency domain.
  • the signals in the time domain for a plurality of symbols are similarly converted, so that the signal Y [n, m] in the time-frequency domain can be obtained.
  • the signal Y [n, m] in this time-frequency domain is demodulated by OTFS.
  • OTFS demodulation a two-dimensional symplectic Fourier transform (SFFT) is used to convert a two-dimensional signal Y [n, m] in the time-frequency region into a two-dimensional signal y [l, k] in the delay-Doppler region. Be converted.
  • SFFT two-dimensional symplectic Fourier transform
  • the two-dimensional signal y [l, k] is demapped to the symbol string y 0 (i) in the order corresponding to the predetermined rule described above. After that, this symbol string is QAM demodulated, and error correction decoding is executed on the obtained bit string to acquire data.
  • the above description can be similarly applied even if at least one of the transmitting device 101 and the receiving device 102 uses a plurality of antennas for the sake of simplicity. That is, the above processing is executed for each antenna. Moreover, the conventional MIMO method can also be applied.
  • the received signal will be affected by the delay wave and Doppler shift during transmission.
  • the effect is that, when an ideal matching filter is used, the value obtained by circularly convolving the transmission path value in the delay-Doppler region with the transmission signal in the delay-Doppler region becomes the transmission signal in the delay-Doppler region. Appears in the form of.
  • CP is generally used in consideration of the influence of delay, but the influence of Doppler shift is not considered.
  • OTFS modulation / demodulation the signal is mapped to the delay-Doppler region and then transmitted, and the channel estimates expressed by the delay and Doppler shift are used to affect not only the delay but also the Doppler shift. Can be considered. Therefore, the signal reception characteristic can be improved.
  • the present embodiment provides a method of transmitting the data signal and the reference signal with the same symbol so that the data signal and the reference signal do not overlap in the delay-Doppler region.
  • the transmission device 101 separately maps the data signal and the reference signal to the delay-Doppler region, and separately performs OTFS modulation.
  • the signal in the first time-frequency region corresponding to the data signal and the signal in the second time-frequency region corresponding to the reference signal are separately obtained.
  • the signal in the first time-frequency region and the signal in the second time-frequency region are mapped to the element in the time-frequency region input to the Heisenberg converter, and the signal in the third time-frequency region is mapped.
  • the signal in the third time-frequency region is input to the Heisenberg converter, and then CP is added and transmitted to the receiving device 102.
  • the receiving device 102 When the receiving device 102 receives the signal in the time domain, it removes the CP and converts it into a signal in the fourth time-frequency domain by Wigner conversion.
  • This fourth time-frequency domain signal corresponds to a third time-frequency domain signal.
  • the receiving device 102 separates the signal in the fourth time-frequency region into a signal in the fifth time-frequency region corresponding to the data signal and a signal in the sixth time-frequency region corresponding to the reference signal.
  • the signal in the third time-frequency domain is generated by mapping the signal in the first time-frequency domain and the signal in the second time-frequency domain. Therefore, here, the inverse transformation (demapping) of the mapping is executed.
  • a signal in the fifth time-frequency region corresponding to the signal in the first time-frequency region and a signal in the sixth time-frequency region corresponding to the signal in the second time-frequency region are obtained. ..
  • the receiving device 102 performs OTFS inverse conversion on the signal in the fifth time-frequency region and the signal in the sixth time-frequency region.
  • the receiving device 102 can know how the reference signal has changed in the delay-Doppler region due to the influence of the transmission line, and delays. -Channel estimates in the Doppler region can be obtained.
  • the receiving device 102 identifies the channel estimate in the delay-Doppler region, and then the signal in the fifth time-frequency region is based on the channel estimate in the delay-Doppler region from the ISFFT-converted data signal component. And eliminate the influence of the channel.
  • the data signal component received in the delay-Doppler region is the result (and the noise component is added) in which the channel value in the delay-Doppler region is convoluted with the data signal component transmitted in the delay-Doppler region, respectively. It is observed as a result). Therefore, the influence of the channel in the delay-Doppler region can be eliminated by executing the process corresponding to the inverse operation of the circular convolution using the channel estimated value.
  • the transmission device 101 separately performs ISFFT conversion of the reference signal and the data signal to generate a signal in the time-frequency region to be input to the Heisenberg converter thereafter. Separately, ISFFT-converted signals are mapped according to a predetermined rule. As a result, the receiving device 102 can separate the reference signal and the data signal in the time-frequency domain. As a result, the receiving device 102 can obtain the channel estimated value in the delay-Doppler region without being affected by the data signal by performing the OTFS inverse transformation on the separated reference signal.
  • FIG. 2 shows a hardware configuration example of the transmitting device 101 and the receiving device 102 according to the present embodiment.
  • the transmitting device 101 and the receiving device 102 include a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205.
  • the processor 201 is a computer including one or more processing circuits such as a general-purpose CPU (central processing unit) and an ASIC (integrated circuit for a specific application), and is stored in a ROM 202 or a storage device 204. By reading and executing the existing program, the entire processing of each device and the above-mentioned processing are executed.
  • the ROM 202 is a read-only memory that stores information such as programs and various parameters related to processing executed by the transmitting device 101 / receiving device 102.
  • the RAM 203 is a random access memory that functions as a workspace when the processor 201 executes a program and stores temporary information.
  • the storage device 204 is composed of, for example, a detachable external storage device or the like.
  • the communication circuit 205 is composed of, for example, a circuit for wireless communication.
  • the transmitting device 101 / receiving device 102 includes, for example, a baseband circuit and an RF circuit for cellular communication, and an antenna as a communication circuit 205 for mutual communication. Although one communication circuit 205 is shown in FIG. 2, the transmission device 101 / reception device 102 may have a plurality of communication circuits.
  • the functional configuration of the transmitting device 101 / receiving device 102 described below may be configured mainly as a function of the communication circuit 205, but may be realized by a processor 201 or the like.
  • FIG. 3 shows a configuration example of the transmission device 101.
  • the example of FIG. 3 focuses only on the signal transmission portion of the transmission device 101, and omits other general functions.
  • the transmission device 101 includes, for example, a coding unit 301, a QAM modulation unit 302, a first OTFS modulation unit 303, a reference signal generation unit 304, a second OTFS modulation unit 305, a mapping unit 306, a Heisenberg conversion unit 307, and a CP. Includes additional section 308.
  • the coding unit 301, the QAM modulation unit 302, and the first OTFS modulation unit 303 are functional units for generating a data signal portion.
  • the coding unit 301 performs error correction coding of the data and acquires a sequence (for example, a bit string) after coding. ..
  • the QAM modulation unit 302 QAM-modulates the coded sequence to acquire a modulation symbol string.
  • QAM quadrature amplitude modulation
  • PSK phase shift keying
  • the first OTFS modulation unit 303 maps the modulation symbol sequence to the delay-Doppler region to generate the first signal in the delay-Doppler region.
  • the modulation symbol sequence x 0 (i) is mapped to the delay-Doppler region of M rows and N columns.
  • k is an index indicating the component of the delay region
  • l is an index indicating the component of the Doppler region. This is an example and other mappings may be used.
  • the first OTFS modulation unit 303 performs OTFS modulation on the first signal, and a second signal X [n, m] in the time-frequency region is generated. Since the operations executed here are as described above, the description thereof will be omitted.
  • the size of the second signal can be changed by adjusting the variable M or the variable N, for example. That is, when mapping the modulation symbol string to the delay-Doppler region, the signal in the time-frequency region corresponding to the data signal input to the Heisenberg converter 307 by adjusting the size of the matrix in the delay-Doppler region. You can adjust the size of.
  • the reference signal generation unit 304 and the second OTFS modulation unit 305 generate a reference signal after OTFS modulation has been performed.
  • the reference signal generation unit 304 arranges a predetermined value at a predetermined position in the delay-Doppler region to generate a reference signal in the delay-Doppler region. For example, in an N-by-M matrix, some values may be set to non-zero predetermined values and others to zero to generate a reference signal in the delay-Doppler region.
  • the second OTFS modulation unit 305 performs OTFS modulation on the reference signal in the generated delay-Doppler region.
  • the reference signal is also a signal in the time-frequency region corresponding to the reference signal input to the Heisenberg converter 307 by adjusting the size of the matrix in the delay-Doppler region when mapping to the delay-Doppler region. You can adjust the size of.
  • the reference signal can have a constant pattern. Therefore, a reference signal in the time-frequency region that has been ISFFT-converted in advance may be prepared. In this case, the reference signal generation unit 304 and the second OTFS modulation unit 305 may be omitted.
  • the mapping unit 306 maps the time-frequency region signal corresponding to the data signal and the time-frequency region signal corresponding to the reference signal according to a predetermined pattern, and inputs the time-frequency to the Heisenberg conversion unit 307. Generates a region signal.
  • the Heisenberg transform unit 307 executes a generalized inverse Fourier transform to convert the input time-frequency domain into a time domain signal. By mapping and Heisenberg transformation, the data signal and the reference signal are arranged orthogonally in the time-frequency domain, and the receiving device 102 can easily separate these signals.
  • the Heisenberg conversion unit 307 uses a plurality of frequency components corresponding to one or more times in the input time-frequency domain to generate a time waveform corresponding to one symbol.
  • the CP addition unit 308 adds a Cyclic Prefix to the generated time waveform. Since this process is a conventional technique, detailed description thereof will be omitted.
  • the size of the signal in the time-frequency region to be input to the Heisenberg converter 307 is constant, and the sum of the size of the data signal and the size of the reference signal component is equal to or less than the constant size.
  • the size of the signal and reference signal is adjusted. For example, for one time component, the data signal and the reference so that the sum of the size of the frequency component of the data signal and the size of the frequency component of the reference signal is less than or equal to the number of frequency components input to the Heisenberg converter 307.
  • the size of the signal is adjusted.
  • the size of the frequency component input to the Heisenberg converter 307 corresponds to the size of the delay component in the signal before OTFS modulation.
  • the size of the signal of the frequency component input to the Heisenberg converter 307 is made constant by reducing the size of the delay component of the data signal. Can be done.
  • the size of the time component input to the Heisenberg converter 307 corresponds to the size of the Doppler component in the signal before OTFS modulation. Therefore, for example, when the size of the Doppler component of the reference signal is increased, the size of the Doppler component of the data signal is reduced to keep the size of the time component of the signal input to the Heisenberg converter 307 constant. Can be done.
  • the size of the reference signal can be changed depending on the wireless environment, for example, the magnitude of the fluctuation of the channel in the delay region and the fluctuation of the channel in the Doppler region.
  • the mapping unit 306 maps the reference signal and the data signal in a pattern corresponding to the size thereof. For example, when the variation in the delay region is large, the reference signal can be configured so that the variation in the delay region can be appropriately estimated by increasing the size of the delay-Doppler region in the delay direction. Further, when the fluctuation in the Doppler region is large, the reference signal can be configured so that the fluctuation in the Doppler region can be appropriately estimated by increasing the size of the delay-Doppler region in the Doppler direction.
  • the mapping unit 306 performs mapping using a pattern capable of arranging a sufficient number of reference signal components in the frequency component. .. Further, as the size in the Doppler direction increases, the number of time components of the signal input to the Heisenberg converter 307 increases. Therefore, when a reference signal whose size is increased in the Doppler direction is used, the mapping unit 306 performs mapping using a pattern capable of arranging a sufficient number of reference signal components in the time component. ..
  • FIGS. 4A to 4D An example of selecting a pattern for this mapping is schematically shown in FIGS. 4A to 4D.
  • FIG. 4A shows an example in which both the variation of the channel in the delay region and the variation of the channel in the Doppler region are small.
  • the reference signal can appropriately perform channel estimation even if both the size in the delay direction and the size in the Doppler direction of the delay-Doppler region are small. Therefore, even in the signal in the time-frequency region, the size of the reference signal is small, so that only a small number of regions in the entire signal are allocated for the reference signal as shown in FIG. 4A.
  • FIG. 4B shows, for example, an example in which the variation of the channel in the delay region is large and the variation of the channel in the Doppler region is small.
  • the reference signal may have a small size in the Doppler direction in the delay-Doppler region, but may need to be large in size in the delay direction in order to properly perform channel estimation. Therefore, in the signal in the time-frequency region, the reference signal has a large frequency component size corresponding to the delay direction and a small size in the time direction corresponding to the Doppler direction. Therefore, for example, as shown in FIG. 4B, a pattern is used in which a large number of reference signals are arranged in the frequency direction and a small number of reference signals are arranged in the time direction in the time-frequency region.
  • FIG. 4C shows an example in which the fluctuation of the channel in the Doppler region is large and the fluctuation of the channel in the delay region is small, for example.
  • the reference signal may have a small delay-Doppler region size in the delay direction in order to properly perform channel estimation, but may need to be large in the Doppler direction. Therefore, in the signal in the time-frequency domain, the reference signal has a large time component size corresponding to the Doppler direction and a small size in the frequency direction corresponding to the delay direction. Therefore, as shown in FIG. 4C, for example, a pattern is used in which a large number of reference signals are arranged in the time direction and a small number of reference signals are arranged in the frequency direction in the time-frequency region. In a similar context, a pattern as shown in FIG. 4D can be used, for example, when both the delay region and the Doppler region channel variability is large.
  • the reference signal arrangement pattern used by the mapping unit 306, which indicates the position where the reference signal is arranged in the time-frequency region, is shared in advance between the transmitting device 101 and the receiving device 102. Thereby, the receiving device 102 can specify at which position of the received signal the component corresponding to the reference signal is included.
  • the transmitting device 101 selects and uses one pattern from a plurality of patterns as shown in FIGS. 4A to 4D, the receiving device 102 may be notified of information indicating the selected pattern. For example, a plurality of patterns may be shared in advance, and information indicating which of them may be used may be notified from the transmitting device 101 to the receiving device 102, or other information capable of identifying the pattern to be used may be transmitted.
  • the transmitting device 101 may notify the receiving device 102.
  • FIG. 5 shows a configuration example of the receiving device 102.
  • the example of FIG. 5 focuses only on the signal receiving portion of the receiving device 102, and omits other general functions.
  • the receiving device 102 includes, for example, a CP removing unit 501, a Wigner conversion unit 502, a demapping unit 503, a first OTFS demodulation unit 504, a channel estimation unit 505, a second OTFS demodulation unit 506, a signal detection unit 507, and a QAM demodulation unit. It has a unit 508 and a decoding unit 509.
  • the CP removal unit 501 removes the Cyclic Prefix part from the received time signal. Since this process is a conventional process, detailed operation will be omitted here.
  • the Wigner transforming unit 502 executes a generalized Fourier transform on the time waveform from which the Cyclic Prefix has been removed to generate a signal in the frequency domain.
  • the Wigner conversion unit 502 generates signals in the time-frequency domain by generating signals in a plurality of frequency domains from a plurality of time waveforms that are sequentially input.
  • the demapping unit 503 separates the signal in the time-frequency domain into a data signal component and a reference signal component.
  • the demapping unit 503 executes the inverse transformation of the mapping by the mapping unit 306.
  • the demapping unit 503 specifies the time-frequency component to which the mapping unit 306 has assigned the reference signal, and among the signals in the time-frequency region output from the Wigner conversion unit 502, the specified time-frequency component. Is extracted as a reference signal component. Further, the demapping unit 503 extracts other parts as data signal components.
  • the demapping unit 503 can input the component extracted as a reference signal to the first OTFS demodulation unit 504, and input the component extracted as a data signal to the second OTFS demodulation unit 506.
  • the reference signal input to the first OTFS demodulation unit 504 is a signal in the time-frequency region in which the data signal component is deleted and the size of at least one of the time component and the frequency component is reduced. be.
  • the data signal input to the second OTFS demodulation unit 506 is a signal in the time-frequency region in which the reference signal component is deleted and a part of the size is reduced.
  • the first OTFS demodulation unit 504 SFFT-converts the signal in the time-frequency region of the reference signal component to acquire the reference signal in the delay-Doppler region.
  • the channel estimation unit 505 acquires the channel estimation value in the delay-Doppler region from the reference signal in the delay-Doppler region.
  • the channel estimate is a value that indicates how the reference signal spreads in the delay-Doppler region.
  • the receiving device 102 recognizes in advance what value is arranged as the reference signal at which position in the delay-Doppler region and is transmitted, and acquires the channel estimation value based on that knowledge. That is, since the received signal is represented by a circular convolution integral of the transmitted signal and the value indicating the channel when an ideal matching filter is used, the channel is indicated as if a known reference signal was transmitted as the transmitted signal. The value is specified.
  • the second OTFS demodulation unit 506 performs SFFT conversion of the signal in the time-frequency region of the data signal component, and acquires the data signal in the delay-Doppler region.
  • the signal detection unit 507 detects each signal component in the delay-Doppler region with respect to the data signal in the delay-Doppler region by using the channel estimation value acquired by the channel estimation unit 505. For example, equalization can be performed by performing the inverse operation of two-dimensional circular convolution. By this equalization, it is possible to eliminate the state in which adjacent data are overlapped and received due to the influence of the channel in the delay-Doppler region.
  • the signal detection unit 507 converts each two-dimensional signal component in each of the delay-Doppler regions into a one-dimensional signal sequence.
  • This conversion corresponds to, for example, the inverse transformation of the first OTFS modulation unit 303 for the conversion in which the symbol sequence output by the QAM modulation unit 302 is rearranged into signals in the two-dimensional delay-Doppler region.
  • the QAM demodulation unit 508 QAM democratizes the one-dimensional signal sequence output by the signal detection unit 507 and outputs a bit string.
  • the decoding unit 509 executes error correction decoding on the output bit string and acquires the data string.
  • the data signal does not interfere with the reference signal, so that channel estimation can be performed with high accuracy. It becomes. Further, it is possible to suppress a decrease in frequency utilization efficiency due to, for example, using only one symbol for transmission of a reference signal, and it is possible to efficiently perform channel estimation.
  • the above-mentioned configuration of the transmitting device 101 and the configuration of the receiving device 102 can be mounted on the baseband chip, respectively. Further, the functions of both the transmitting device 101 and the receiving device 102 may be mounted on one baseband chip. In addition, implementations other than these may be used. Further, the above example is only an example, and other configurations may be used as long as the same processing can be executed.
  • the reference signal and the data signal are subject to channel fluctuations of different frequencies. Therefore, for example, the reference signal component can be arranged at a position in the time-frequency region confirmed by, for example, an experiment so that the reference signal receives a channel variation close to that of the data signal.
  • the transmitting device 101 and the receiving device 102 need to share information on which component of the signal in the time-frequency region the reference signal component is mapped to. If there is only one such mapping pattern, it is only necessary to share this one pattern in advance, for example, when manufacturing these devices.
  • the pattern to be used is switched according to the channel conditions (maximum delay spread and maximum Doppler frequency)
  • the pattern used is the transmitter 101. Processing shared with the receiving device 102 is required. This process is shown in FIG.
  • the receiving device 102 receives the signal from the transmitting device 101 (S601), measures the reference signal, and estimates the delay / Doppler fluctuation (S602). Then, the receiving device 102 notifies the transmitting device 101 of information on the maximum delay spread and the maximum Doppler frequency based on the estimated value (S603).
  • this information may be any information as long as it corresponds to the maximum delay spread and the maximum Doppler frequency. For example, the information is based on a value based on the number of symbols and the number of subcarriers in the delay-Doppler region. May be notified.
  • the transmitting device 101 determines the mapping of the reference signal based on the notified signal, and notifies the receiving device 102 of the result of the determination (S604).
  • information on how often the reference signal is mapped in time and frequency may be notified, and which of a plurality of prepared patterns is used. The indicated value may be notified.

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Abstract

Provided is a transmission device which: generates a first signal by subjecting a signal of delay-Doppler domain including data to be transmitted to orthogonal time frequency and space (OTFS) modulation; generates a third signal of time-frequency domain by mapping the first signal and a second signal, which is obtained by subjecting a reference signal having a predetermined value disposed in a predetermined position of delay-Doppler domain to OTFS modulation, to time-frequency domain with a predetermined pattern; transforms the third signal into a temporal signal by Heisenberg transform; and transmits the temporal signal to a receiver device.

Description

ＯＴＦＳ変調を用いた通信において高精度化されたチャネル推定手法を用いる送信装置、受信装置、通信方法、およびベースバンドチップTransmitters, receivers, communication methods, and baseband chips that use highly accurate channel estimation techniques in communication using OTFS modulation.
　本発明は、送信装置、受信装置、通信方法、およびベースバンドチップに関し、特に、ＯＴＦＳ（Orthogonal Time Frequency and Space）変調を用いる無線通信システムにおけるチャネル推定を高精度化する技術に関する。 The present invention relates to a transmitting device, a receiving device, a communication method, and a baseband chip, and more particularly to a technique for improving the accuracy of channel estimation in a wireless communication system using OTFS (Orthogonal Time Frequency and Space) modulation.
　近年、新たな変調方式としてＯＴＦＳ（Orthogonal Time Frequency and Space）変調が提案されている（特許文献１参照）。ＯＴＦＳ変調が行われた信号を受信する受信機では、遅延－ドップラー領域でのチャネル情報を用いて、遅延－ドップラー領域での信号検出が行われる。 In recent years, OTFS (Orthogonal Time Frequency and Space) modulation has been proposed as a new modulation method (see Patent Document 1). In the receiver that receives the OTFS-modulated signal, the signal detection in the delay-Doppler region is performed by using the channel information in the delay-Doppler region.
国際公開第２０１６／０１４５９８号International Publication No. 2016/014598
　本発明は、遅延－ドップラー領域でのチャネル推定を効率的かつ現実的に実行可能とする技術を提供する。 The present invention provides a technique that enables efficient and realistic channel estimation in the delay-Doppler region.
　本発明の一態様による送信装置は、送信対象のデータを含んだ遅延－ドップラー領域の信号をＯＴＦＳ（Orthogonal Time Frequency and Space）変調して第１の信号を生成する第１のＯＴＦＳ変調手段と、前記第１の信号と、遅延－ドップラー領域の所定の位置に所定値が配置された参照信号がＯＴＦＳ変調されることにより得られる第２の信号とのそれぞれを、時間－周波数領域に所定のパターンでマッピングして、時間－周波数領域の第３の信号を生成するマッピング手段と、前記第３の信号をHeisenberg変換により時間信号に変換する変換手段と、前記時間信号を受信装置へ送信する送信手段と、を有する。 The transmission device according to one aspect of the present invention includes a first OTFS modulation means that generates a first signal by OTFS (Orthogonal Time Frequency and Space) modulation of a signal in a delay-Doppler region containing data to be transmitted. Each of the first signal and the second signal obtained by OTFS-modulating a reference signal in which a predetermined value is arranged at a predetermined position in the delay-Doppler region has a predetermined pattern in the time-frequency region. Mapping means for generating a third signal in the time-frequency region by mapping with, a conversion means for converting the third signal into a time signal by Heisenberg conversion, and a transmission means for transmitting the time signal to a receiving device. And have.
　本発明の一態様による受信装置は、送信装置から信号を受信する受信手段と、Wigner変換を用いて受信した信号を変換して、時間－周波数領域の信号を生成する変換手段と、前記時間－周波数領域の信号において、時間－周波数領域に所定のパターンでマッピングされた参照信号の第１の成分とデータ信号の第２の成分とを分離する分離手段と、前記第１の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第１の信号を生成する第１のＯＴＦＳ復調手段と、前記第１の信号に基づいて、遅延－ドップラー領域におけるチャネル推定を実行する推定手段と、前記第２の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第２の信号を生成する第２のＯＴＦＳ復調手段と、前記第２の信号から、前記チャネル推定の結果を用いてデータ信号を抽出する抽出手段と、を有する。 The receiving device according to one aspect of the present invention includes a receiving means for receiving a signal from the transmitting device, a conversion means for converting the received signal using Wigner conversion to generate a signal in the time-frequency region, and the time-. In the signal of the frequency region, the separation means for separating the first component of the reference signal and the second component of the data signal mapped in the time-frequency region in a predetermined pattern, and the first component are OTFS ( Orthogonal Time Frequency and Space) Estimate to perform channel estimation in the delay-Doppler region based on the first OTFS demodating means that demolishes and generates the first signal in the delay-Doppler region. From the means, the second OTFS demodulating means for demodulating the second component by OTFS (Orthogonal Time Frequency and Space) to generate a second signal in the delay-Doppler region, and the second signal. It has an extraction means for extracting a data signal using the result of channel estimation.
　本発明によれば、遅延－ドップラー領域でのチャネル推定を効率的かつ現実的に実行可能とすることができる。 According to the present invention, channel estimation in the delay-Doppler region can be performed efficiently and realistically.
　本発明のその他の特徴及び利点は、添付図面を参照とした以下の説明により明らかになるであろう。なお、添付図面においては、同じ若しくは同様の構成には、同じ参照番号を付す。 Other features and advantages of the present invention will be clarified by the following description with reference to the accompanying drawings. In the attached drawings, the same or similar configurations are given the same reference numbers.
　添付図面は明細書に含まれ、その一部を構成し、本発明の実施の形態を示し、その記述と共に本発明の原理を説明するために用いられる。
図１は、無線通信システムの構成例を示す図である。 図２は、送信装置および受信装置のハードウェア構成例を示す図である。 図３は、送信装置の送信機能の構成例を示す図である。 図４Ａは、参照信号の配置パターンの例を示す図である。 図４Ｂは、参照信号の配置パターンの例を示す図である。 図４Ｃは、参照信号の配置パターンの例を示す図である。 図４Ｄは、参照信号の配置パターンの例を示す図である。 図５は、受信装置の送信機能の構成例を示す図である。 図６は、送信装置と受信装置との間で参照信号配置パターンを共有する処理の流れの例を示す図である。 The accompanying drawings are included in the specification and are used to form a part thereof, show embodiments of the present invention, and explain the principles of the present invention together with the description thereof.
FIG. 1 is a diagram showing a configuration example of a wireless communication system. FIG. 2 is a diagram showing a hardware configuration example of a transmitting device and a receiving device. FIG. 3 is a diagram showing a configuration example of a transmission function of the transmission device. FIG. 4A is a diagram showing an example of a reference signal arrangement pattern. FIG. 4B is a diagram showing an example of a reference signal arrangement pattern. FIG. 4C is a diagram showing an example of a reference signal arrangement pattern. FIG. 4D is a diagram showing an example of a reference signal arrangement pattern. FIG. 5 is a diagram showing a configuration example of a transmission function of the receiving device. FIG. 6 is a diagram showing an example of a processing flow in which a reference signal arrangement pattern is shared between a transmitting device and a receiving device.
　以下、添付図面を参照して実施形態を詳しく説明する。なお、以下の実施形態は特許請求の範囲に係る発明を限定するものでない。実施形態には複数の特徴が記載されているが、これらの複数の特徴の全てが発明に必須のものとは限らず、また、複数の特徴は任意に組み合わせられてもよい。さらに、添付図面においては、同一若しくは同様の構成に同一の参照番号を付し、重複した説明は省略する。 Hereinafter, embodiments will be described in detail with reference to the attached drawings. The following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiment, not all of the plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the attached drawings, the same or similar configurations are given the same reference numbers, and duplicate explanations are omitted.
　（システム構成）
　図１に、本実施形態にかかる無線通信システムの構成例を示す。本無線通信システムは、送信装置１０１と受信装置１０２とを含んで構成される。送信装置１０１および受信装置１０２は、例えば、セルラ通信システムにおける基地局装置と端末装置との組み合わせでありうる。ただし、これに限られず、任意の無線通信システムにおいて送信装置１０１および受信装置１０２の組み合わせが使用されうる。なお、本実施形態では、説明を簡単にするために、１つの送信装置１０１と１つの受信装置１０２とを示しているが、当然に複数の送信装置および複数の受信装置が存在しうる。また、便宜上、送信装置と受信装置との組み合わせを示しているが、送信装置が受信装置の機能を有してもよいし、受信装置が送信装置の機能を有してもよい。 (System configuration)
FIG. 1 shows a configuration example of the wireless communication system according to the present embodiment. The wireless communication system includes a transmitting device 101 and a receiving device 102. The transmitting device 101 and the receiving device 102 may be, for example, a combination of a base station device and a terminal device in a cellular communication system. However, the present invention is not limited to this, and a combination of the transmitting device 101 and the receiving device 102 can be used in any wireless communication system. In the present embodiment, one transmitting device 101 and one receiving device 102 are shown for the sake of simplicity, but naturally there may be a plurality of transmitting devices and a plurality of receiving devices. Further, although the combination of the transmitting device and the receiving device is shown for convenience, the transmitting device may have the function of the receiving device, or the receiving device may have the function of the transmitting device.
　本実施形態では、送信装置１０１が、変調方式としてＯＴＦＳ（Orthogonal Time Frequency and Space）変調を用いて信号を生成し、受信装置は、ＯＴＦＳ復調を用いて信号を復調する。送信装置１０１は、例えば、誤り訂正符号化等が行われた後の送信対象のビット列を、ＱＡＭ等を用いて変調して、シンボル系列を取得する。そして、ＱＡＭシンボルの系列が、遅延－ドップラー領域と呼ばれる２次元の領域にマッピングされる。その後、この２次元の領域にマッピングされたシンボルに対して、ＯＴＦＳ変調が実行される。この変調は、２次元のinverse symplectic Fourier transform（ＩＳＦＦＴ）を用いて、遅延－ドップラー領域の信号を時間－周波数領域の信号に変換する。そして、ＯＴＦＳ変調によって得られた時間－周波数領域の信号が、一般化された逆フーリエ変換（Heisenberg変換）によって時間信号に変換される。なお、ここでは、逆フーリエ変換として、Heisenberg変換が用いられるものとするが、これ以外の逆フーリエ変換が実行されてもよい。ＯＴＦＳ変調によって得られた時間－周波数領域の信号のうち、１つの時間要素に対応する複数の周波数要素がHeisenberg変換器へ入力されることにより、１シンボル分の時間信号が生成される。その後、生成された時間信号に対してCyclic Prefix（ＣＰ）が付加されることにより、送信信号が形成される。 In the present embodiment, the transmitting device 101 generates a signal using OTFS (Orthogonal Time Frequency and Space) modulation as a modulation method, and the receiving device demodulates the signal using OTFS demodulation. The transmission device 101, for example, modulates a bit string to be transmitted after error correction coding or the like is performed using QAM or the like to acquire a symbol sequence. Then, the series of QAM symbols is mapped to a two-dimensional region called a delay-Doppler region. After that, OTFS modulation is executed on the symbols mapped in this two-dimensional region. This modulation uses a two-dimensional inverse symplectic Fourier transform (ISFFT) to transform a signal in the delay-Doppler region into a signal in the time-frequency domain. Then, the time-frequency domain signal obtained by OTFS modulation is converted into a time signal by a generalized inverse Fourier transform (Heisenberg transform). Here, the Heisenberg transform is used as the inverse Fourier transform, but other inverse Fourier transforms may be executed. Of the time-frequency domain signals obtained by OTFS modulation, a plurality of frequency elements corresponding to one time element are input to the Heisenberg converter to generate a time signal for one symbol. After that, a Cyclic Prefix (CP) is added to the generated time signal to form a transmission signal.
　例えば、ＱＡＭシンボルの系列がｘ0(i)である場合に、このシンボル系列ｘ0(i)が、所定のルールに従って、２次元の遅延－ドップラー領域の信号行列ｘ[k,l]にマッピングされる。そして、この２次元の信号行列ｘ[k, l]に対して、ＯＴＦＳ変調が施される。ＯＴＦＳ変調では、２次元のＩＳＦＦＴによって、遅延－ドップラー領域の２次元の信号が、時間－周波数領域の２次元の信号Ｘ[n, m]に変換される。この変換は、以下のように表記される。
Figure JPOXMLDOC01-appb-I000001
なお、Ｗtx[n, m]は、窓関数である。このようにして得られた信号Ｘ[n, m]に対して、時間ごとの周波数領域の信号がHeisenberg変換により時間領域の信号に変換され、その時間領域の信号にＣＰが付されることにより、送信信号ｓ(t)が生成される。ここで実行される、Heisenberg変換は、以下のように表記される。
Figure JPOXMLDOC01-appb-I000002
なお、ｇtx(t)は、送信パルス成形フィルタである。 For example, when the sequence of QAM symbols is x 0 (i), this symbol sequence x 0 (i) is mapped to the signal matrix x [k, l] in the two-dimensional delay-Doppler region according to a predetermined rule. Will be done. Then, OTFS modulation is applied to the two-dimensional signal matrix x [k, l]. In OTFS modulation, the two-dimensional ISFFT converts a two-dimensional signal in the delay-Doppler region into a two-dimensional signal X [n, m] in the time-frequency region. This conversion is written as follows.
Figure JPOXMLDOC01-appb-I000001
W tx [n, m] is a window function. With respect to the signal X [n, m] thus obtained, the signal in the frequency domain for each time is converted into the signal in the time domain by Heisenberg conversion, and CP is added to the signal in the time domain. , The transmission signal s (t) is generated. The Heisenberg conversion performed here is written as follows.
Figure JPOXMLDOC01-appb-I000002
Note that g tx (t) is a transmission pulse forming filter.
　その後、送信信号が伝送路を介して受信装置１０２において受信される。このときの受信信号をｒ(t)と表記する。受信装置１０２は、この受信信号ｒ(t)からＣＰを除去して、一般化フーリエ変換（Wigner変換）を実行することにより、時間－周波数領域の信号Ｙ[n, m]に変換する。なお、Wigner変換は、Heisenberg変換の逆変換に相当する。なお、Wigner変換は、一般化されたフーリエ変換の例として示しているが、送信装置１０１において実行されている逆フーリエ変換に対する正変換として使用可能な限りにおいて、どのような変換方法が用いられてもよい。Wigner変換では、１シンボル分の時間領域の信号が周波数領域の信号に変換される。そして、複数シンボル分の時間領域の信号が同様に変換されることにより、時間－周波数領域の信号Ｙ[n, m]が得られる。この時間－周波数領域の信号Ｙ[n, m]は、ＯＴＦＳ復調される。ＯＴＦＳ復調では、２次元のsymplectic Fourier transform（ＳＦＦＴ）を用いて、時間－周波数領域の２次元の信号Ｙ[n, m]が、遅延－ドップラー領域の２次元の信号ｙ[l, k]に変換される。この変換は、以下のように表記される。
Figure JPOXMLDOC01-appb-I000003
なお、Ｗrxは、窓関数である。その後、その２次元の信号ｙ[l, k]が、上述の所定のルールに対応する順序でシンボル列ｙ0(i)にデマッピングされる。その後、このシンボル列は、ＱＡＭ復調され、得られたビット列に対して誤り訂正復号が実行されることにより、データが取得される。 After that, the transmission signal is received by the receiving device 102 via the transmission line. The received signal at this time is expressed as r (t). The receiving device 102 removes the CP from the received signal r (t) and performs a generalized Fourier transform (Wigner transform) to convert it into a signal Y [n, m] in the time-frequency region. The Wigner transformation corresponds to the inverse transformation of the Heisenberg transformation. The Wigner transform is shown as an example of a generalized Fourier transform, but any conversion method is used as long as it can be used as a positive transform for the inverse Fourier transform executed in the transmitter 101. May be good. In Wigner conversion, a signal in the time domain for one symbol is converted into a signal in the frequency domain. Then, the signals in the time domain for a plurality of symbols are similarly converted, so that the signal Y [n, m] in the time-frequency domain can be obtained. The signal Y [n, m] in this time-frequency domain is demodulated by OTFS. In OTFS demodulation, a two-dimensional symplectic Fourier transform (SFFT) is used to convert a two-dimensional signal Y [n, m] in the time-frequency region into a two-dimensional signal y [l, k] in the delay-Doppler region. Be converted. This conversion is written as follows.
Figure JPOXMLDOC01-appb-I000003
W rx is a window function. After that, the two-dimensional signal y [l, k] is demapped to the symbol string y 0 (i) in the order corresponding to the predetermined rule described above. After that, this symbol string is QAM demodulated, and error correction decoding is executed on the obtained bit string to acquire data.
　なお、上述の説明は、簡単のために送信装置１０１と受信装置１０２との少なくともいずれかが複数のアンテナを用いても同様に適用することができる。すなわち、アンテナごとに、上述の処理が実行される。また、従来のＭＩＭＯの手法を適用することもできる。 Note that the above description can be similarly applied even if at least one of the transmitting device 101 and the receiving device 102 uses a plurality of antennas for the sake of simplicity. That is, the above processing is executed for each antenna. Moreover, the conventional MIMO method can also be applied.
　受信信号は、伝送途中に遅延波およびドップラーシフトの影響を受けることとなる。このとき、その影響は、理想的な整合フィルターを用いた場合、遅延－ドップラー領域における送信信号に遅延－ドップラー領域における伝送路値が巡回畳み込みされた値が、遅延－ドップラー領域における送信信号となる、という形で現れる。従来のＯＦＤＭによる信号伝送では、一般に、遅延の影響が考慮されてＣＰが用いられるが、ドップラーシフトの影響は考慮されていなかった。これに対して、ＯＴＦＳ変調／復調では、信号を遅延－ドップラー領域にマッピングしてから送信し、遅延とドップラーシフトによって表現されるチャネル推定値を用いて、遅延のみならずドップラーシフトの影響をも考慮することができる。このため、信号の受信特性を改善することができる。 The received signal will be affected by the delay wave and Doppler shift during transmission. At this time, the effect is that, when an ideal matching filter is used, the value obtained by circularly convolving the transmission path value in the delay-Doppler region with the transmission signal in the delay-Doppler region becomes the transmission signal in the delay-Doppler region. Appears in the form of. In conventional signal transmission by OFDM, CP is generally used in consideration of the influence of delay, but the influence of Doppler shift is not considered. On the other hand, in OTFS modulation / demodulation, the signal is mapped to the delay-Doppler region and then transmitted, and the channel estimates expressed by the delay and Doppler shift are used to affect not only the delay but also the Doppler shift. Can be considered. Therefore, the signal reception characteristic can be improved.
　ここで、ＯＴＦＳ変調された信号を適切に検出するためには、遅延－ドップラー領域におけるチャネル推定が高精度に実行されることが必要となる。このとき、遅延－ドップラー領域においてデータ信号の中に参照信号を埋め込むと、伝送路の影響により、遅延－ドップラー領域の受信信号においてデータ信号と参照信号とが重なって観測され、伝送路を高精度に推定することができない。これに対して、例えば、参照信号が送信されるシンボルにおいて、データ信号を送信しないようにすることもできる。これにより、参照信号がデータ信号と重なることがなくなるため、高精度に伝送路を推定することができる。しかしながら、このような構成では、参照信号が送信されるシンボルでデータ信号が送信されないことにより、周波数利用効率が劣化してしまう。 Here, in order to properly detect the OTFS-modulated signal, it is necessary to perform channel estimation in the delay-Doppler region with high accuracy. At this time, if a reference signal is embedded in the data signal in the delay-Doppler region, the data signal and the reference signal are observed overlapping in the received signal in the delay-Doppler region due to the influence of the transmission line, and the transmission line is highly accurate. Cannot be estimated. On the other hand, for example, it is possible to prevent the data signal from being transmitted in the symbol to which the reference signal is transmitted. As a result, the reference signal does not overlap with the data signal, so that the transmission line can be estimated with high accuracy. However, in such a configuration, the frequency utilization efficiency deteriorates because the data signal is not transmitted at the symbol to which the reference signal is transmitted.
　このため、本実施形態では、データ信号と参照信号とが遅延－ドップラー領域において重なり合わないように、かつ、データ信号と参照信号とを同じシンボルで送信する手法を提供する。 Therefore, the present embodiment provides a method of transmitting the data signal and the reference signal with the same symbol so that the data signal and the reference signal do not overlap in the delay-Doppler region.
　具体的には、送信装置１０１は、データ信号と参照信号とを、それぞれ別個に遅延－ドップラー領域にマッピングし、それぞれ別個にＯＴＦＳ変調する。これにより、データ信号に対応する第１の時間－周波数領域の信号と、参照信号に対応する第２の時間－周波数領域の信号とが別個に得られる。そして、この第１の時間－周波数領域の信号と第２の時間－周波数領域の信号とを、Heisenberg変換器へ入力される時間－周波数領域のエレメントへマッピングして、第３の時間－周波数領域の信号を生成する。そして、第３の時間－周波数領域の信号がHeisenberg変換器へ入力され、その後にＣＰを付加されて受信装置１０２へ送信される。 Specifically, the transmission device 101 separately maps the data signal and the reference signal to the delay-Doppler region, and separately performs OTFS modulation. As a result, the signal in the first time-frequency region corresponding to the data signal and the signal in the second time-frequency region corresponding to the reference signal are separately obtained. Then, the signal in the first time-frequency region and the signal in the second time-frequency region are mapped to the element in the time-frequency region input to the Heisenberg converter, and the signal in the third time-frequency region is mapped. Generate a signal of. Then, the signal in the third time-frequency region is input to the Heisenberg converter, and then CP is added and transmitted to the receiving device 102.
　受信装置１０２は、時間領域で信号を受信すると、ＣＰを除去し、Wigner変換によって、第４の時間－周波数領域の信号に変換する。この第４の時間－周波数領域の信号は、第３の時間－周波数領域の信号に相当する。受信装置１０２は、第４の時間－周波数領域の信号を、データ信号に対応する第５の時間－周波数領域の信号と参照信号に対応する第６の時間－周波数領域の信号とに分離する。上述のように、第３の時間－周波数領域の信号は、第１の時間－周波数領域の信号と第２の時間－周波数領域の信号とがマッピングされることによって生成される。このため、ここでは、そのマッピングの逆変換（デマッピング）が実行される。この結果、第１の時間－周波数領域の信号に対応する第５の時間－周波数領域の信号と、第２の時間－周波数領域の信号に対応する第６の時間－周波数領域の信号が得られる。そして、受信装置１０２は、第５の時間－周波数領域の信号と第６の時間－周波数領域の信号に対して、ＯＴＦＳ逆変換を施す。第６の時間－周波数領域の信号がＯＴＦＳ逆変換されることにより、受信装置１０２は、伝送路の影響によって、遅延－ドップラー領域において参照信号がどのように変化したかを知ることができ、遅延－ドップラー領域におけるチャネル推定値を得ることができる。受信装置１０２は、この遅延－ドップラー領域におけるチャネル推定値を特定すると、続いて、第５の時間－周波数領域の信号がＩＳＦＦＴ変換されたデータ信号成分から、遅延－ドップラー領域におけるチャネル推定値に基づいて、チャネルの影響を除去する。ここで、遅延－ドップラー領域において受信されたデータ信号成分は、それぞれ、遅延－ドップラー領域において送信されたデータ信号成分に遅延－ドップラー領域におけるチャネルの値が畳み込まれた結果（および雑音成分が加算された結果）として観測される。このため、チャネル推定値を用いて巡回畳み込みの逆演算に相当する処理を実行することにより、遅延－ドップラー領域におけるチャネルの影響が除去されうる。 When the receiving device 102 receives the signal in the time domain, it removes the CP and converts it into a signal in the fourth time-frequency domain by Wigner conversion. This fourth time-frequency domain signal corresponds to a third time-frequency domain signal. The receiving device 102 separates the signal in the fourth time-frequency region into a signal in the fifth time-frequency region corresponding to the data signal and a signal in the sixth time-frequency region corresponding to the reference signal. As described above, the signal in the third time-frequency domain is generated by mapping the signal in the first time-frequency domain and the signal in the second time-frequency domain. Therefore, here, the inverse transformation (demapping) of the mapping is executed. As a result, a signal in the fifth time-frequency region corresponding to the signal in the first time-frequency region and a signal in the sixth time-frequency region corresponding to the signal in the second time-frequency region are obtained. .. Then, the receiving device 102 performs OTFS inverse conversion on the signal in the fifth time-frequency region and the signal in the sixth time-frequency region. By inversely converting the signal in the sixth time-frequency region to OTFS, the receiving device 102 can know how the reference signal has changed in the delay-Doppler region due to the influence of the transmission line, and delays. -Channel estimates in the Doppler region can be obtained. The receiving device 102 identifies the channel estimate in the delay-Doppler region, and then the signal in the fifth time-frequency region is based on the channel estimate in the delay-Doppler region from the ISFFT-converted data signal component. And eliminate the influence of the channel. Here, the data signal component received in the delay-Doppler region is the result (and the noise component is added) in which the channel value in the delay-Doppler region is convoluted with the data signal component transmitted in the delay-Doppler region, respectively. It is observed as a result). Therefore, the influence of the channel in the delay-Doppler region can be eliminated by executing the process corresponding to the inverse operation of the circular convolution using the channel estimated value.
　このように、本実施形態では、送信装置１０１は、参照信号とデータ信号とをそれぞれ別個にＩＳＦＦＴ変換して、その後のHeisenberg変換器へ入力される時間－周波数領域の信号を生成する際に、別個にＩＳＦＦＴ変換された信号を所定のルールでマッピングする。これにより、受信装置１０２は、時間－周波数領域において、参照信号とデータ信号とを分離することができる。この結果、受信装置１０２は、分離後の参照信号についてＯＴＦＳ逆変換をすることにより、データ信号の影響を受けずに、遅延－ドップラー領域におけるチャネル推定値を得ることができる。 As described above, in the present embodiment, the transmission device 101 separately performs ISFFT conversion of the reference signal and the data signal to generate a signal in the time-frequency region to be input to the Heisenberg converter thereafter. Separately, ISFFT-converted signals are mapped according to a predetermined rule. As a result, the receiving device 102 can separate the reference signal and the data signal in the time-frequency domain. As a result, the receiving device 102 can obtain the channel estimated value in the delay-Doppler region without being affected by the data signal by performing the OTFS inverse transformation on the separated reference signal.
　以下では、このような送信装置１０１と受信装置１０２との構成について説明する。 Hereinafter, the configuration of such a transmitting device 101 and a receiving device 102 will be described.
　（装置構成）
　図２に、本実施形態に係る送信装置１０１および受信装置１０２のハードウェア構成例を示す。送信装置１０１および受信装置１０２は、一例において、プロセッサ２０１、ＲＯＭ２０２、ＲＡＭ２０３、記憶装置２０４、及び通信回路２０５を含んで構成される。プロセッサ２０１は、汎用のＣＰＵ（中央演算装置）や、ＡＳＩＣ（特定用途向け集積回路）等の、１つ以上の処理回路を含んで構成されるコンピュータであり、ＲＯＭ２０２や記憶装置２０４に記憶されているプログラムを読み出して実行することにより、各装置の全体の処理や、上述の各処理を実行する。ＲＯＭ２０２は、送信装置１０１／受信装置１０２が実行する処理に関するプログラムや各種パラメータ等の情報を記憶する読み出し専用メモリである。ＲＡＭ２０３は、プロセッサ２０１がプログラムを実行する際のワークスペースとして機能し、また、一時的な情報を記憶するランダムアクセスメモリである。記憶装置２０４は、例えば着脱可能な外部記憶装置等によって構成される。通信回路２０５は、例えば、無線通信用の回路によって構成される。送信装置１０１／受信装置１０２は、相互に通信するための通信回路２０５として、例えばセルラ通信用のベースバンド回路及びＲＦ回路等とアンテナとを含んで構成される。なお、図２では、１つの通信回路２０５が図示されているが、送信装置１０１／受信装置１０２は、複数の通信回路を有しうる。以下で説明する送信装置１０１／受信装置１０２の機能構成は、主として通信回路２０５の機能として構成されうるが、プロセッサ２０１等によって実現されてもよい。 (Device configuration)
FIG. 2 shows a hardware configuration example of the transmitting device 101 and the receiving device 102 according to the present embodiment. In one example, the transmitting device 101 and the receiving device 102 include a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. The processor 201 is a computer including one or more processing circuits such as a general-purpose CPU (central processing unit) and an ASIC (integrated circuit for a specific application), and is stored in a ROM 202 or a storage device 204. By reading and executing the existing program, the entire processing of each device and the above-mentioned processing are executed. The ROM 202 is a read-only memory that stores information such as programs and various parameters related to processing executed by the transmitting device 101 / receiving device 102. The RAM 203 is a random access memory that functions as a workspace when the processor 201 executes a program and stores temporary information. The storage device 204 is composed of, for example, a detachable external storage device or the like. The communication circuit 205 is composed of, for example, a circuit for wireless communication. The transmitting device 101 / receiving device 102 includes, for example, a baseband circuit and an RF circuit for cellular communication, and an antenna as a communication circuit 205 for mutual communication. Although one communication circuit 205 is shown in FIG. 2, the transmission device 101 / reception device 102 may have a plurality of communication circuits. The functional configuration of the transmitting device 101 / receiving device 102 described below may be configured mainly as a function of the communication circuit 205, but may be realized by a processor 201 or the like.
　図３に送信装置１０１の構成例を示す。図３の例は、送信装置１０１の信号送信部分のみに着目したものであり、その他の一般的な機能については省略している。送信装置１０１は、例えば、符号化部３０１、ＱＡＭ変調部３０２、第１のＯＴＦＳ変調部３０３、参照信号生成部３０４、第２のＯＴＦＳ変調部３０５、マッピング部３０６、Heisenberg変換部３０７、およびＣＰ付加部３０８を含む。 FIG. 3 shows a configuration example of the transmission device 101. The example of FIG. 3 focuses only on the signal transmission portion of the transmission device 101, and omits other general functions. The transmission device 101 includes, for example, a coding unit 301, a QAM modulation unit 302, a first OTFS modulation unit 303, a reference signal generation unit 304, a second OTFS modulation unit 305, a mapping unit 306, a Heisenberg conversion unit 307, and a CP. Includes additional section 308.
　符号化部３０１、ＱＡＭ変調部３０２、および第１のＯＴＦＳ変調部３０３は、データ信号部分を生成するための機能部である。送信装置１０１において、例えば、所定のアプリケーションのためのデータ等の送信対象データが発生すると、符号化部３０１は、そのデータを誤り訂正符号化して、符号化後の系列（例えばビット列）を取得する。そして、ＱＡＭ変調部３０２は、この符号化後の系列をＱＡＭ変調して、変調シンボル列を取得する。なお、ＱＡＭ（quadrature amplitude modulation）は一例に過ぎず、例えば、ＰＳＫ（phase shift keying）等の他の変調方式が用いられてもよい。第１のＯＴＦＳ変調部３０３は、変調シンボル列を遅延－ドップラー領域にマッピングして遅延－ドップラー領域の第１の信号を生成する。例えば、変調シンボル列ｘ0(i)を、M行N列の遅延－ドップラー領域にマッピングする。例えば、第１の信号をｘ[k, l]と表す場合、ｘ[k, l]＝ｘ0(l×N + k)のようなマッピングが行われうる（ただし、0≦k＜Mかつ0≦l＜N）。なお、kは遅延領域の成分を示すインデクスであり、lはドップラー領域の成分を示すインデクスである。これは一例であり、他のマッピングが用いられてもよい。そして、第１のＯＴＦＳ変調部３０３は、第１の信号に対してＯＴＦＳ変調を施し、時間－周波数領域の第２の信号Ｘ[n, m]が生成される。ここで実行される演算は上述の通りであるため、説明については省略する。なお、ここで、例えば変数Mや変数Nを調整することにより、第２の信号のサイズを変更することができる。すなわち、変調シンボル列を遅延－ドップラー領域にマッピングする際に、遅延－ドップラー領域の行列のサイズを調整することにより、Heisenberg変換部３０７に入力される、データ信号に対応する時間－周波数領域の信号のサイズを調整することができる。 The coding unit 301, the QAM modulation unit 302, and the first OTFS modulation unit 303 are functional units for generating a data signal portion. In the transmission device 101, for example, when transmission target data such as data for a predetermined application is generated, the coding unit 301 performs error correction coding of the data and acquires a sequence (for example, a bit string) after coding. .. Then, the QAM modulation unit 302 QAM-modulates the coded sequence to acquire a modulation symbol string. Note that QAM (quadrature amplitude modulation) is only an example, and other modulation methods such as PSK (phase shift keying) may be used, for example. The first OTFS modulation unit 303 maps the modulation symbol sequence to the delay-Doppler region to generate the first signal in the delay-Doppler region. For example, the modulation symbol sequence x 0 (i) is mapped to the delay-Doppler region of M rows and N columns. For example, when the first signal is expressed as x [k, l], mapping such as x [k, l] = x 0 (l × N + k) can be performed (where 0 ≦ k <M and 0 ≤ l <N). Note that k is an index indicating the component of the delay region, and l is an index indicating the component of the Doppler region. This is an example and other mappings may be used. Then, the first OTFS modulation unit 303 performs OTFS modulation on the first signal, and a second signal X [n, m] in the time-frequency region is generated. Since the operations executed here are as described above, the description thereof will be omitted. Here, the size of the second signal can be changed by adjusting the variable M or the variable N, for example. That is, when mapping the modulation symbol string to the delay-Doppler region, the signal in the time-frequency region corresponding to the data signal input to the Heisenberg converter 307 by adjusting the size of the matrix in the delay-Doppler region. You can adjust the size of.
　参照信号生成部３０４および第２のＯＴＦＳ変調部３０５は、ＯＴＦＳ変調がなされた後の参照信号を生成する。参照信号生成部３０４は、遅延－ドップラー領域の所定の位置に所定値を配置して、遅延－ドップラー領域における参照信号を生成する。例えば、N行M列の行列において、一部の値が非ゼロの所定値に設定され、他の値がゼロに設定されて、遅延－ドップラー領域における参照信号が生成されうる。第２のＯＴＦＳ変調部３０５は、生成された遅延－ドップラー領域における参照信号に対してＯＴＦＳ変調を施す。なお、参照信号においても、遅延－ドップラー領域にマッピングする際に、遅延－ドップラー領域の行列のサイズを調整することにより、Heisenberg変換部３０７に入力される参照信号に対応する時間－周波数領域の信号のサイズを調整することができる。なお、参照信号は一定のパターンでありうる。このため、事前にＩＳＦＦＴ変換された時間－周波数領域の参照信号が用意されていてもよい。この場合、参照信号生成部３０４および第２のＯＴＦＳ変調部３０５は省略されてもよい。 The reference signal generation unit 304 and the second OTFS modulation unit 305 generate a reference signal after OTFS modulation has been performed. The reference signal generation unit 304 arranges a predetermined value at a predetermined position in the delay-Doppler region to generate a reference signal in the delay-Doppler region. For example, in an N-by-M matrix, some values may be set to non-zero predetermined values and others to zero to generate a reference signal in the delay-Doppler region. The second OTFS modulation unit 305 performs OTFS modulation on the reference signal in the generated delay-Doppler region. The reference signal is also a signal in the time-frequency region corresponding to the reference signal input to the Heisenberg converter 307 by adjusting the size of the matrix in the delay-Doppler region when mapping to the delay-Doppler region. You can adjust the size of. The reference signal can have a constant pattern. Therefore, a reference signal in the time-frequency region that has been ISFFT-converted in advance may be prepared. In this case, the reference signal generation unit 304 and the second OTFS modulation unit 305 may be omitted.
　マッピング部３０６は、データ信号に対応する時間－周波数領域の信号と参照信号に対応する時間－周波数領域の信号とを、所定のパターンに従ってマッピングして、Heisenberg変換部３０７へ入力される時間－周波数領域の信号を生成する。Heisenberg変換部３０７は、一般化された逆フーリエ変換を実行して、入力された時間－周波数領域を、時間領域の信号に変換する。マッピングとHeisenberg変換により、データ信号と参照信号とが時間－周波数領域において直交して配置されることとなり、受信装置１０２は、これらの信号を容易に分離することができるようになる。なお、Heisenberg変換部３０７は、入力された時間－周波数領域のうちの１つ以上の時間に対応する複数の周波数成分を用いて、１つのシンボルに相当する時間波形を生成する。ＣＰ付加部３０８は、生成された時間波形にCyclic Prefixを付加する。なお、この処理については従来技術であるため、詳細な説明については省略する。 The mapping unit 306 maps the time-frequency region signal corresponding to the data signal and the time-frequency region signal corresponding to the reference signal according to a predetermined pattern, and inputs the time-frequency to the Heisenberg conversion unit 307. Generates a region signal. The Heisenberg transform unit 307 executes a generalized inverse Fourier transform to convert the input time-frequency domain into a time domain signal. By mapping and Heisenberg transformation, the data signal and the reference signal are arranged orthogonally in the time-frequency domain, and the receiving device 102 can easily separate these signals. The Heisenberg conversion unit 307 uses a plurality of frequency components corresponding to one or more times in the input time-frequency domain to generate a time waveform corresponding to one symbol. The CP addition unit 308 adds a Cyclic Prefix to the generated time waveform. Since this process is a conventional technique, detailed description thereof will be omitted.
　ここで、例えばHeisenberg変換部３０７に入力すべき時間－周波数領域の信号のサイズは一定であり、データ信号のサイズと参照信号成分のサイズとの和がその一定のサイズ以下となるように、データ信号および参照信号のサイズが調整される。例えば、１つの時間成分について、データ信号の周波数成分のサイズと参照信号の周波数成分のサイズとの和が、Heisenberg変換部３０７に入力される周波数成分の数以下となるように、データ信号および参照信号のサイズが調整される。一例において、Heisenberg変換部３０７に入力される周波数成分のサイズは、ＯＴＦＳ変調前の信号における遅延成分のサイズに対応する。このため、例えば参照信号の遅延成分のサイズを大きくした場合には、データ信号の遅延成分のサイズを小さくすることにより、Heisenberg変換部３０７に入力される周波数成分の信号のサイズを一定とすることができる。同様に、Heisenberg変換部３０７に入力される時間成分のサイズは、ＯＴＦＳ変調前の信号におけるドップラー成分のサイズに対応する。このため、例えば参照信号のドップラー成分のサイズを大きくした場合には、データ信号のドップラー成分のサイズを小さくすることにより、Heisenberg変換部３０７に入力される信号の時間成分のサイズを一定とすることができる。 Here, for example, the size of the signal in the time-frequency region to be input to the Heisenberg converter 307 is constant, and the sum of the size of the data signal and the size of the reference signal component is equal to or less than the constant size. The size of the signal and reference signal is adjusted. For example, for one time component, the data signal and the reference so that the sum of the size of the frequency component of the data signal and the size of the frequency component of the reference signal is less than or equal to the number of frequency components input to the Heisenberg converter 307. The size of the signal is adjusted. In one example, the size of the frequency component input to the Heisenberg converter 307 corresponds to the size of the delay component in the signal before OTFS modulation. Therefore, for example, when the size of the delay component of the reference signal is increased, the size of the signal of the frequency component input to the Heisenberg converter 307 is made constant by reducing the size of the delay component of the data signal. Can be done. Similarly, the size of the time component input to the Heisenberg converter 307 corresponds to the size of the Doppler component in the signal before OTFS modulation. Therefore, for example, when the size of the Doppler component of the reference signal is increased, the size of the Doppler component of the data signal is reduced to keep the size of the time component of the signal input to the Heisenberg converter 307 constant. Can be done.
　なお、参照信号は、例えば、遅延領域のチャネルの変動とドップラー領域のチャネルの変動の大きさ等の、無線環境によって、そのサイズが変更されうる。この場合、マッピング部３０６は、そのサイズに応じたパターンで、参照信号とデータ信号とをマッピングする。例えば、遅延領域の変動が大きい場合は、参照信号は、遅延－ドップラー領域の遅延方向のサイズが増やされることにより、遅延領域における変動を適切に推定できるように構成されうる。また、ドップラー領域の変動が大きい場合は、参照信号は、遅延－ドップラー領域のドップラー方向のサイズが増やされることにより、ドップラー領域における変動を適切に推定できるように構成されうる。 The size of the reference signal can be changed depending on the wireless environment, for example, the magnitude of the fluctuation of the channel in the delay region and the fluctuation of the channel in the Doppler region. In this case, the mapping unit 306 maps the reference signal and the data signal in a pattern corresponding to the size thereof. For example, when the variation in the delay region is large, the reference signal can be configured so that the variation in the delay region can be appropriately estimated by increasing the size of the delay-Doppler region in the delay direction. Further, when the fluctuation in the Doppler region is large, the reference signal can be configured so that the fluctuation in the Doppler region can be appropriately estimated by increasing the size of the delay-Doppler region in the Doppler direction.
　上述のように、遅延方向のサイズが増えると、Heisenberg変換部３０７に入力される信号の周波数成分の数が増える。このため、マッピング部３０６は、遅延方向のサイズが増やされた参照信号が使用される場合には、周波数成分において十分な数の参照信号成分を配置することができるパターンを用いて、マッピングを行う。また、ドップラー方向のサイズが増えると、Heisenberg変換部３０７に入力される信号の時間成分の数が増える。このため、マッピング部３０６は、ドップラー方向のサイズが増やされた参照信号が使用される場合には、時間成分において十分な数の参照信号成分を配置することができるパターンを用いて、マッピングを行う。 As described above, as the size in the delay direction increases, the number of frequency components of the signal input to the Heisenberg converter 307 increases. Therefore, when a reference signal whose size in the delay direction is increased is used, the mapping unit 306 performs mapping using a pattern capable of arranging a sufficient number of reference signal components in the frequency component. .. Further, as the size in the Doppler direction increases, the number of time components of the signal input to the Heisenberg converter 307 increases. Therefore, when a reference signal whose size is increased in the Doppler direction is used, the mapping unit 306 performs mapping using a pattern capable of arranging a sufficient number of reference signal components in the time component. ..
　このマッピングのパターンの選択の例を、図４Ａ～図４Ｄに概略的に示す。図４Ａは、例えば、遅延領域のチャネルの変動とドップラー領域のチャネルの変動がともに小さい場合の例を示している。この場合、参照信号は、遅延－ドップラー領域の遅延方向のサイズとドップラー方向のサイズとが共に小さくても適切にチャネル推定を行うことができる。このため、時間－周波数領域の信号においても、参照信号のサイズが小さいため、図４Ａのように、信号全体の中で少数の領域のみが参照信号用に割り当てられる。図４Ｂは、例えば、遅延領域のチャネルの変動が大きく、ドップラー領域のチャネルの変動が小さい場合の例を示している。この場合、参照信号は、適切にチャネル推定を行うためには、遅延－ドップラー領域のドップラー方向のサイズは小さくてもよいが、遅延方向のサイズについては大きくすることが必要となりうる。このため、時間－周波数領域の信号において、参照信号は、遅延方向に対応する周波数成分のサイズが大きく、ドップラー方向に対応する時間方向のサイズが小さくなる。このため、例えば図４Ｂのように、時間－周波数領域において、周波数方向に多数の参照信号が配置され、時間方向には少数の参照信号が配置されるようなパターンが使用される。図４Ｃは、例えば、ドップラー領域のチャネルの変動が大きく、遅延領域のチャネルの変動が小さい場合の例を示している。この場合、参照信号は、適切にチャネル推定を行うためには、遅延－ドップラー領域の遅延方向のサイズは小さくてもよいが、ドップラー方向のサイズについては大きくすることが必要となりうる。このため、時間－周波数領域の信号において、参照信号は、ドップラー方向に対応する時間成分のサイズが大きく、遅延方向に対応する周波数方向のサイズが小さくなる。このため、例えば図４Ｃのように、時間－周波数領域において、時間方向に多数の参照信号が配置され、周波数方向には少数の参照信号が配置されるようなパターンが使用される。同様の文脈で、図４Ｄのようなパターンは、例えば、遅延領域とドップラー領域のチャネルの変動がいずれも大きい場合に用いられうる。 An example of selecting a pattern for this mapping is schematically shown in FIGS. 4A to 4D. FIG. 4A shows an example in which both the variation of the channel in the delay region and the variation of the channel in the Doppler region are small. In this case, the reference signal can appropriately perform channel estimation even if both the size in the delay direction and the size in the Doppler direction of the delay-Doppler region are small. Therefore, even in the signal in the time-frequency region, the size of the reference signal is small, so that only a small number of regions in the entire signal are allocated for the reference signal as shown in FIG. 4A. FIG. 4B shows, for example, an example in which the variation of the channel in the delay region is large and the variation of the channel in the Doppler region is small. In this case, the reference signal may have a small size in the Doppler direction in the delay-Doppler region, but may need to be large in size in the delay direction in order to properly perform channel estimation. Therefore, in the signal in the time-frequency region, the reference signal has a large frequency component size corresponding to the delay direction and a small size in the time direction corresponding to the Doppler direction. Therefore, for example, as shown in FIG. 4B, a pattern is used in which a large number of reference signals are arranged in the frequency direction and a small number of reference signals are arranged in the time direction in the time-frequency region. FIG. 4C shows an example in which the fluctuation of the channel in the Doppler region is large and the fluctuation of the channel in the delay region is small, for example. In this case, the reference signal may have a small delay-Doppler region size in the delay direction in order to properly perform channel estimation, but may need to be large in the Doppler direction. Therefore, in the signal in the time-frequency domain, the reference signal has a large time component size corresponding to the Doppler direction and a small size in the frequency direction corresponding to the delay direction. Therefore, as shown in FIG. 4C, for example, a pattern is used in which a large number of reference signals are arranged in the time direction and a small number of reference signals are arranged in the frequency direction in the time-frequency region. In a similar context, a pattern as shown in FIG. 4D can be used, for example, when both the delay region and the Doppler region channel variability is large.
　なお、マッピング部３０６によって使用される、時間－周波数領域における参照信号が配置される位置を示す参照信号配置パターンが、事前に送信装置１０１と受信装置１０２との間で共有される。これにより、受信装置１０２は、受信信号のどの位置に参照信号に対応する成分が含まれているかを特定することができる。なお、送信装置１０１が図４Ａ～図４Ｄのような複数のパターンの中から１つのパターンを選択して使用する場合は、その選択されたパターンを示す情報が受信装置１０２に通知されうる。例えば、複数のパターンが事前に共有され、そのうちのいずれが使用されるかを示す情報が送信装置１０１から受信装置１０２に通知されてもよいし、使用されるパターンを特定可能な他の情報が送信装置１０１から受信装置１０２に通知されてもよい。 The reference signal arrangement pattern used by the mapping unit 306, which indicates the position where the reference signal is arranged in the time-frequency region, is shared in advance between the transmitting device 101 and the receiving device 102. Thereby, the receiving device 102 can specify at which position of the received signal the component corresponding to the reference signal is included. When the transmitting device 101 selects and uses one pattern from a plurality of patterns as shown in FIGS. 4A to 4D, the receiving device 102 may be notified of information indicating the selected pattern. For example, a plurality of patterns may be shared in advance, and information indicating which of them may be used may be notified from the transmitting device 101 to the receiving device 102, or other information capable of identifying the pattern to be used may be transmitted. The transmitting device 101 may notify the receiving device 102.
　図５に、受信装置１０２の構成例を示す。図５の例は、受信装置１０２の信号受信部分のみに着目したものであり、その他の一般的な機能については省略している。受信装置１０２は、例えば、ＣＰ除去部５０１、Wigner変換部５０２、デマッピング部５０３、第１のＯＴＦＳ復調部５０４、チャネル推定部５０５、第２のＯＴＦＳ復調部５０６、信号検出部５０７、ＱＡＭ復調部５０８、および復号部５０９を有する。 FIG. 5 shows a configuration example of the receiving device 102. The example of FIG. 5 focuses only on the signal receiving portion of the receiving device 102, and omits other general functions. The receiving device 102 includes, for example, a CP removing unit 501, a Wigner conversion unit 502, a demapping unit 503, a first OTFS demodulation unit 504, a channel estimation unit 505, a second OTFS demodulation unit 506, a signal detection unit 507, and a QAM demodulation unit. It has a unit 508 and a decoding unit 509.
　ＣＰ除去部５０１は、受信した時間信号から、Cyclic Prefix部分を除去する。この処理については従来の処理であるため、ここでは詳細な動作については説明を省略する。Wigner変換部５０２は、Cyclic Prefixが除去された時間波形に対して、一般化されたフーリエ変換を実行して、周波数領域の信号を生成する。Wigner変換部５０２は、逐次的に入力される複数の時間波形から複数の周波数領域の信号を生成することにより、時間－周波数領域の信号を生成する。デマッピング部５０３は、時間－周波数領域の信号を、データ信号成分と参照信号成分とに分離する。デマッピング部５０３は、マッピング部３０６によるマッピングの逆変換を実行する。すなわち、デマッピング部５０３は、マッピング部３０６が参照信号を割り当てた時間－周波数成分を特定し、Wigner変換部５０２から出力された時間－周波数領域の信号のうち、その特定された時間－周波数成分を、参照信号成分として抽出する。また、デマッピング部５０３は、その他の部分をデータ信号成分として抽出する。デマッピング部５０３は、参照信号として抽出した成分を第１のＯＴＦＳ復調部５０４へ入力し、データ信号として抽出した成分を第２のＯＴＦＳ復調部５０６へ入力しうる。なお、例えば、第１のＯＴＦＳ復調部５０４へ入力される参照信号は、データ信号成分が削除されて、時間成分と周波数成分との少なくともいずれかのサイズが小さくなった時間－周波数領域の信号である。同様に、第２のＯＴＦＳ復調部５０６へ入力されるデータ信号は、参照信号成分が削除されて、一部のサイズが小さくなった時間－周波数領域の信号である。 The CP removal unit 501 removes the Cyclic Prefix part from the received time signal. Since this process is a conventional process, detailed operation will be omitted here. The Wigner transforming unit 502 executes a generalized Fourier transform on the time waveform from which the Cyclic Prefix has been removed to generate a signal in the frequency domain. The Wigner conversion unit 502 generates signals in the time-frequency domain by generating signals in a plurality of frequency domains from a plurality of time waveforms that are sequentially input. The demapping unit 503 separates the signal in the time-frequency domain into a data signal component and a reference signal component. The demapping unit 503 executes the inverse transformation of the mapping by the mapping unit 306. That is, the demapping unit 503 specifies the time-frequency component to which the mapping unit 306 has assigned the reference signal, and among the signals in the time-frequency region output from the Wigner conversion unit 502, the specified time-frequency component. Is extracted as a reference signal component. Further, the demapping unit 503 extracts other parts as data signal components. The demapping unit 503 can input the component extracted as a reference signal to the first OTFS demodulation unit 504, and input the component extracted as a data signal to the second OTFS demodulation unit 506. For example, the reference signal input to the first OTFS demodulation unit 504 is a signal in the time-frequency region in which the data signal component is deleted and the size of at least one of the time component and the frequency component is reduced. be. Similarly, the data signal input to the second OTFS demodulation unit 506 is a signal in the time-frequency region in which the reference signal component is deleted and a part of the size is reduced.
　第１のＯＴＦＳ復調部５０４は、参照信号成分の時間－周波数領域の信号をＳＦＦＴ変換して、遅延－ドップラー領域の参照信号を取得する。チャネル推定部５０５は、遅延－ドップラー領域の参照信号から、遅延－ドップラー領域のチャネル推定値を取得する。チャネル推定値は、参照信号が遅延－ドップラー領域においてどのように拡散したかを示す値である。受信装置１０２は、参照信号としてどのような値が遅延－ドップラー領域のどの位置に配置されて送信されたかを事前に認識しており、その知識に基づいてチャネル推定値を取得する。すなわち、受信信号は、理想的な整合フィルターを用いる場合、送信信号とチャネルを示す値との巡回畳み込み積分によって表されるため、既知の参照信号が送信信号で送信されたものとして、チャネルを示す値が特定される。 The first OTFS demodulation unit 504 SFFT-converts the signal in the time-frequency region of the reference signal component to acquire the reference signal in the delay-Doppler region. The channel estimation unit 505 acquires the channel estimation value in the delay-Doppler region from the reference signal in the delay-Doppler region. The channel estimate is a value that indicates how the reference signal spreads in the delay-Doppler region. The receiving device 102 recognizes in advance what value is arranged as the reference signal at which position in the delay-Doppler region and is transmitted, and acquires the channel estimation value based on that knowledge. That is, since the received signal is represented by a circular convolution integral of the transmitted signal and the value indicating the channel when an ideal matching filter is used, the channel is indicated as if a known reference signal was transmitted as the transmitted signal. The value is specified.
　第２のＯＴＦＳ復調部５０６は、データ信号成分の時間－周波数領域の信号をＳＦＦＴ変換して、遅延－ドップラー領域のデータ信号を取得する。信号検出部５０７は、遅延－ドップラー領域のデータ信号に対して、チャネル推定部５０５で取得されたチャネル推定値を用いて遅延－ドップラー領域のそれぞれにおける各信号成分を検出する。例えば、２次元の巡回畳み込みの逆演算が行われることにより、等化が行われうる。この等化により、遅延－ドップラー領域において隣接するデータがチャネルの影響で重なり合って受信された状態を解消することができる。なお、信号検出部５０７は、遅延－ドップラー領域のそれぞれにおける２次元の各信号成分を、１次元の信号系列に変換する。この変換は、例えば、第１のＯＴＦＳ変調部３０３において、ＱＡＭ変調部３０２が出力したシンボル系列を２次元の遅延－ドップラー領域の信号に並べ替えた変換に対する逆変換に相当する。ＱＡＭ復調部５０８は、信号検出部５０７によって出力された１次元の信号系列をＱＡＭ復調し、ビット列を出力する。復号部５０９は、出力されたビット列に対して誤り訂正復号を実行し、データ列を取得する。 The second OTFS demodulation unit 506 performs SFFT conversion of the signal in the time-frequency region of the data signal component, and acquires the data signal in the delay-Doppler region. The signal detection unit 507 detects each signal component in the delay-Doppler region with respect to the data signal in the delay-Doppler region by using the channel estimation value acquired by the channel estimation unit 505. For example, equalization can be performed by performing the inverse operation of two-dimensional circular convolution. By this equalization, it is possible to eliminate the state in which adjacent data are overlapped and received due to the influence of the channel in the delay-Doppler region. The signal detection unit 507 converts each two-dimensional signal component in each of the delay-Doppler regions into a one-dimensional signal sequence. This conversion corresponds to, for example, the inverse transformation of the first OTFS modulation unit 303 for the conversion in which the symbol sequence output by the QAM modulation unit 302 is rearranged into signals in the two-dimensional delay-Doppler region. The QAM demodulation unit 508 QAM democratizes the one-dimensional signal sequence output by the signal detection unit 507 and outputs a bit string. The decoding unit 509 executes error correction decoding on the output bit string and acquires the data string.
　このように、本実施形態では、データ信号と参照信号とを別個にＯＴＦＳ変調／復調することにより、データ信号が参照信号に干渉することがなくなるため、チャネル推定を高精度に実行することが可能となる。また、例えば１つのシンボルを参照信号の送信にのみ使用するなどによる周波数利用効率の低下を抑制することができ、効率的にチャネル推定を行うことが可能となる。 As described above, in the present embodiment, by separately OTFS-modulating / demodulating the data signal and the reference signal, the data signal does not interfere with the reference signal, so that channel estimation can be performed with high accuracy. It becomes. Further, it is possible to suppress a decrease in frequency utilization efficiency due to, for example, using only one symbol for transmission of a reference signal, and it is possible to efficiently perform channel estimation.
　なお、上述の送信装置１０１の構成と受信装置１０２の構成は、それぞれ、ベースバンドチップに実装されうる。また、１つのベースバンドチップに、送信装置１０１と受信装置１０２の両方の機能が実装されてもよい。また、これら以外の実装が用いられてもよい。また、上述の例は一例に過ぎず、同様の処理を実行可能な範囲で他の構成が用いられてもよい。 The above-mentioned configuration of the transmitting device 101 and the configuration of the receiving device 102 can be mounted on the baseband chip, respectively. Further, the functions of both the transmitting device 101 and the receiving device 102 may be mounted on one baseband chip. In addition, implementations other than these may be used. Further, the above example is only an example, and other configurations may be used as long as the same processing can be executed.
　なお、本実施形態では、参照信号とデータ信号とが異なる周波数のチャネル変動を受けることとなる。このため、例えば、参照信号がデータ信号と近いチャネル変動を受けるように、例えば実験等によって確認された時間－周波数領域の位置に、参照信号成分が配置されうる。 In the present embodiment, the reference signal and the data signal are subject to channel fluctuations of different frequencies. Therefore, for example, the reference signal component can be arranged at a position in the time-frequency region confirmed by, for example, an experiment so that the reference signal receives a channel variation close to that of the data signal.
　（参照信号配置パターンの共有処理）
　上述のように、送信装置１０１と受信装置１０２は、参照信号成分が時間－周波数領域の信号のどの成分にマッピングされるかの情報を共有する必要がある。このようなマッピングのパターンが１つしか存在しない場合は、例えばこれらの装置の製造時など、事前にこの１つのパターンを共有しておくのみでよい。一方で、図４Ａ～図４Ｄに関連して説明したように、チャネルの状況（最大遅延広がりや最大ドップラー周波数）に応じて、使用するパターンが切り替えられる場合、使用されるパターンが送信装置１０１と受信装置１０２との間で共有される処理が必要である。この処理について、図６に示す。 (Sharing process of reference signal arrangement pattern)
As described above, the transmitting device 101 and the receiving device 102 need to share information on which component of the signal in the time-frequency region the reference signal component is mapped to. If there is only one such mapping pattern, it is only necessary to share this one pattern in advance, for example, when manufacturing these devices. On the other hand, as described in relation to FIGS. 4A to 4D, when the pattern to be used is switched according to the channel conditions (maximum delay spread and maximum Doppler frequency), the pattern used is the transmitter 101. Processing shared with the receiving device 102 is required. This process is shown in FIG.
　図６の処理では、まず、受信装置１０２が、送信装置１０１からの信号を受信して（Ｓ６０１）、参照信号を測定して、遅延・ドップラー変動を推定する（Ｓ６０２）。そして、受信装置１０２は、推定した値に基づいて、最大遅延広がりや最大ドップラー周波数の情報を送信装置１０１へ通知する（Ｓ６０３）。なお、この情報は、最大遅延広がりや最大ドップラー周波数に対応する情報であればどのようなものであってもよく、例えば、遅延－ドップラー領域のシンボル数やサブキャリア数を基準とした値によって情報が通知されてもよい。また、推定した最大遅延広がりや最大ドップラー周波数の値に対して、現在使用されている参照信号パターンが適切であるか、最大遅延広がりをカバーしきれていないか余裕があるか、最大ドップラー周波数をカバーしきれていないか余裕があるか、などの情報によって、情報が通知されてもよい。そして、送信装置１０１は、通知された信号に基づいて、参照信号のマッピングを決定し、その決定の結果を受信装置１０２へ通知する（Ｓ６０４）。ここでは、例えば、時間、周波数において、どの程度の間隔で参照信号がマッピングされているかの情報が通知されてもよいし、事前に用意された複数のパターンのうちのいずれが使用されるかを示す値が通知されてもよい。 In the process of FIG. 6, first, the receiving device 102 receives the signal from the transmitting device 101 (S601), measures the reference signal, and estimates the delay / Doppler fluctuation (S602). Then, the receiving device 102 notifies the transmitting device 101 of information on the maximum delay spread and the maximum Doppler frequency based on the estimated value (S603). Note that this information may be any information as long as it corresponds to the maximum delay spread and the maximum Doppler frequency. For example, the information is based on a value based on the number of symbols and the number of subcarriers in the delay-Doppler region. May be notified. Also, for the estimated maximum delay spread and maximum Doppler frequency values, the currently used reference signal pattern is appropriate, the maximum delay spread is not covered or can be afforded, and the maximum Doppler frequency is determined. The information may be notified by information such as whether it is not completely covered or can be afforded. Then, the transmitting device 101 determines the mapping of the reference signal based on the notified signal, and notifies the receiving device 102 of the result of the determination (S604). Here, for example, information on how often the reference signal is mapped in time and frequency may be notified, and which of a plurality of prepared patterns is used. The indicated value may be notified.
　このようにして、チャネルに対して適切な参照信号の配置パターンが設定されることにより、チャネルの状況に応じて、チャネル推定を高精度かつ効率的に実行することが可能となる。 By setting an appropriate reference signal arrangement pattern for the channel in this way, it is possible to execute channel estimation with high accuracy and efficiency according to the channel situation.
　発明は上記の実施形態に制限されるものではなく、発明の要旨の範囲内で、種々の変形・変更が可能である。 The invention is not limited to the above embodiment, and various modifications and changes can be made within the scope of the gist of the invention.
　本願は、２０２０年２月２８日提出の日本国特許出願特願２０２０－０３３７０９を基礎として優先権を主張するものであり、その記載内容の全てを、ここに援用する。 This application claims priority based on Japanese Patent Application No. 2020-033709 submitted on February 28, 2020, and all the contents thereof are incorporated herein by reference.

Claims (13)

  1. 　送信対象のデータを含んだ遅延－ドップラー領域の信号をＯＴＦＳ（Orthogonal Time Frequency and Space）変調して第１の信号を生成する第１のＯＴＦＳ変調手段と、
    　前記第１の信号と、遅延－ドップラー領域の所定の位置に所定値が配置された参照信号がＯＴＦＳ変調されることにより得られる第２の信号とのそれぞれを、時間－周波数領域に所定のパターンでマッピングして、時間－周波数領域の第３の信号を生成するマッピング手段と、
    　前記第３の信号をHeisenberg変換により時間信号に変換する変換手段と、
    　前記時間信号を受信装置へ送信する送信手段と、
    　を有する送信装置。     A first OTFS modulation means that generates a first signal by OTFS (Orthogonal Time Frequency and Space) modulation of a signal in the delay-Doppler region containing data to be transmitted.
    Each of the first signal and the second signal obtained by OTFS-modulating a reference signal in which a predetermined value is arranged at a predetermined position in the delay-Doppler region has a predetermined pattern in the time-frequency region. Mapping means to generate a third signal in the time-frequency domain by mapping with
    A conversion means for converting the third signal into a time signal by Heisenberg conversion, and
    A transmission means for transmitting the time signal to the receiving device, and
    Transmitter with.
  2. 　前記参照信号をＯＴＦＳ変調して前記第２の信号を生成する第２のＯＴＦＳ変調手段をさらに有する、請求項１に記載の送信装置。 The transmission device according to claim 1, further comprising a second OTFS modulation means that OTFS-modulates the reference signal to generate the second signal.
  3. 　前記受信装置との間のチャネルの状態に基づいて、前記マッピング手段における前記所定のパターンを変更する変更手段をさらに有する、請求項１又は２に記載の送信装置。 The transmitting device according to claim 1 or 2, further comprising a changing means for changing the predetermined pattern in the mapping means based on the state of the channel with the receiving device.
  4. 　前記チャネルの状態は、前記チャネルにおける遅延広がりとドップラー周波数とに関する状態である、請求項３に記載の送信装置。 The transmission device according to claim 3, wherein the state of the channel is a state related to the delay spread and the Doppler frequency in the channel.
  5. 　前記チャネルの状態の情報を前記受信装置から取得する取得手段をさらに有する、請求項３又は４に記載の送信装置。 The transmitting device according to claim 3 or 4, further comprising an acquiring means for acquiring information on the state of the channel from the receiving device.
  6. 　変更されたパターンを前記受信装置へ通知する通知手段をさらに有する、請求項３から５のいずれか１項に記載の送信装置。 The transmitting device according to any one of claims 3 to 5, further comprising a notification means for notifying the receiving device of the changed pattern.
  7. 　送信装置から信号を受信する受信手段と、
    　Wigner変換を用いて受信した信号を変換して、時間－周波数領域の信号を生成する変換手段と、
    　前記時間－周波数領域の信号において、時間－周波数領域に所定のパターンでマッピングされた参照信号の第１の成分とデータ信号の第２の成分とを分離する分離手段と、
    　前記第１の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第１の信号を生成する第１のＯＴＦＳ復調手段と、
    　前記第１の信号に基づいて、遅延－ドップラー領域におけるチャネル推定を実行する推定手段と、
    　前記第２の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第２の信号を生成する第２のＯＴＦＳ復調手段と、
    　前記第２の信号から、前記チャネル推定の結果を用いてデータ信号を抽出する抽出手段と、
    　を有する受信装置。     A receiving means for receiving a signal from a transmitting device and
    A conversion means that converts the received signal using Wigner conversion to generate a signal in the time-frequency domain, and
    In the signal in the time-frequency domain, a separation means for separating the first component of the reference signal and the second component of the data signal mapped in the time-frequency domain in a predetermined pattern, and
    A first OTFS demodulation means that demodulates the first component by OTFS (Orthogonal Time Frequency and Space) to generate a first signal in the delay-Doppler region.
    An estimation means that performs channel estimation in the delay-Doppler region based on the first signal.
    A second OTFS demodulation means that demodulates the second component by OTFS (Orthogonal Time Frequency and Space) to generate a second signal in the delay-Doppler region.
    An extraction means for extracting a data signal from the second signal using the result of the channel estimation,
    Receiver with.
  8. 　前記送信装置から前記所定のパターンが変更されることの通知を取得する取得手段をさらに有し、
    　前記分離手段は、変更されたパターンに基づいて、前記第１の成分と前記第２の成分とを分離する、請求項７に記載の受信装置。     Further having an acquisition means for acquiring a notification that the predetermined pattern is changed from the transmission device.
    The receiving device according to claim 7, wherein the separating means separates the first component and the second component based on the modified pattern.
  9. 　前記チャネル推定に基づいて前記送信装置との間のチャネルにおける遅延広がりとドップラー周波数とに関する状態を、前記送信装置へ通知する通知手段をさらに有する、請求項７又は８に記載の受信装置。 The receiving device according to claim 7 or 8, further comprising a notification means for notifying the transmitting device of a state relating to a delay spread and a Doppler frequency in a channel with the transmitting device based on the channel estimation.
  10. 　送信装置によって実行される通信方法であって、
    　送信対象のデータを含んだ遅延－ドップラー領域の信号をＯＴＦＳ（Orthogonal Time Frequency and Space）変調して第１の信号を生成することと、
    　前記第１の信号と、遅延－ドップラー領域の所定の位置に所定値が配置された参照信号がＯＴＦＳ変調されることにより得られる第２の信号とのそれぞれを、時間－周波数領域に所定のパターンでマッピングして、時間－周波数領域の第３の信号を生成することと、
    　前記第３の信号をHeisenberg変換により時間信号に変換することと、
    　前記時間信号を受信装置へ送信することと、
    　を含む通信方法。     A communication method performed by a transmitter
    The delay-Doppler region signal containing the data to be transmitted is OTFS (Orthogonal Time Frequency and Space) modulated to generate the first signal.
    Each of the first signal and the second signal obtained by OTFS-modulating a reference signal in which a predetermined value is arranged at a predetermined position in the delay-Doppler region has a predetermined pattern in the time-frequency region. To generate a third signal in the time-frequency domain by mapping with
    Converting the third signal into a time signal by Heisenberg conversion,
    Sending the time signal to the receiver and
    Communication methods including.
  11. 　受信装置によって実行される通信方法であって、
    　送信装置から信号を受信することと、
    　Wigner変換を用いて受信した信号を変換して、時間－周波数領域の信号を生成することと、
    　前記時間－周波数領域の信号において、時間－周波数領域に所定のパターンでマッピングされた参照信号の第１の成分とデータ信号の第２の成分とを分離することと、
    　前記第１の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第１の信号を生成することと、
    　前記第１の信号に基づいて、遅延－ドップラー領域におけるチャネル推定を実行することと、
    　前記第２の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第２の信号を生成することと、
    　前記第２の信号から、前記チャネル推定の結果を用いてデータ信号を抽出することと、
    　を含む通信方法。     A communication method performed by the receiver
    Receiving a signal from the transmitter
    Converting the received signal using Wigner conversion to generate a signal in the time-frequency domain,
    In the time-frequency domain signal, separating the first component of the reference signal and the second component of the data signal mapped in the time-frequency domain in a predetermined pattern, and
    The first component is demodulated by OTFS (Orthogonal Time Frequency and Space) to generate a first signal in the delay-Doppler region.
    Performing channel estimation in the delay-Doppler region based on the first signal,
    The second component is demodulated by OTFS (Orthogonal Time Frequency and Space) to generate a second signal in the delay-Doppler region.
    Extracting a data signal from the second signal using the result of the channel estimation,
    Communication methods including.
  12. 　ベースバンドチップであって、
    　送信対象のデータを含んだ遅延－ドップラー領域の信号をＯＴＦＳ（Orthogonal Time Frequency and Space）変調して第１の信号を生成し、
    　前記第１の信号と、遅延－ドップラー領域の所定の位置に所定値が配置された参照信号がＯＴＦＳ変調されることにより得られる第２の信号とのそれぞれを、時間－周波数領域に所定のパターンでマッピングして、時間－周波数領域の第３の信号を生成し、
    　前記第３の信号をHeisenberg変換により時間信号に変換し、
    　前記時間信号を受信装置へ送信する、
    　ように構成されたベースバンドチップ。     It ’s a baseband chip,
    The delay-Doppler region signal containing the data to be transmitted is OTFS (Orthogonal Time Frequency and Space) modulated to generate the first signal.
    Each of the first signal and the second signal obtained by OTFS-modulating a reference signal in which a predetermined value is arranged at a predetermined position in the delay-Doppler region has a predetermined pattern in the time-frequency region. Map with to generate a third signal in the time-frequency domain,
    The third signal is converted into a time signal by Heisenberg conversion.
    Sending the time signal to the receiver,
    Baseband chip configured to.
  13. 　ベースバンドチップであって、
    　送信装置から信号を受信し、
    　Wigner変換を用いて受信した信号を変換して、時間－周波数領域の信号を生成し、
    　前記時間－周波数領域の信号において、時間－周波数領域に所定のパターンでマッピングされた参照信号の第１の成分とデータ信号の第２の成分とを分離し、
    　前記第１の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第１の信号を生成し、
    　前記第１の信号に基づいて、遅延－ドップラー領域におけるチャネル推定を実行し、
    　前記第２の成分を、ＯＴＦＳ（Orthogonal Time Frequency and Space）復調して、遅延－ドップラー領域の第２の信号を生成し、
    　前記第２の信号から、前記チャネル推定の結果を用いてデータ信号を抽出する、
    　ように構成されたベースバンドチップ。     It ’s a baseband chip,
    Receive a signal from the transmitter and
    Convert the received signal using Wigner conversion to generate a signal in the time-frequency domain.
    In the time-frequency domain signal, the first component of the reference signal and the second component of the data signal mapped in the time-frequency domain in a predetermined pattern are separated.
    The first component is demodulated by OTFS (Orthogonal Time Frequency and Space) to generate a first signal in the delay-Doppler region.
    Based on the first signal, channel estimation in the delay-Doppler region is performed and
    The second component is demodulated by OTFS (Orthogonal Time Frequency and Space) to generate a second signal in the delay-Doppler region.
    A data signal is extracted from the second signal using the result of the channel estimation.
    Baseband chip configured to.
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US12095685B2 (en) 2022-04-07 2024-09-17 Qualcomm Incorporated Orthogonal time frequency space precoding for tracking reference signal
CN115967595A (en) * 2022-11-30 2023-04-14 西安电子科技大学 Semi-blind channel estimation method of MIMO-OTFS system

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