KR20240080042A - Compression and Recovery based OTFS System for Higher Spectral Efficiency and Transmission/Reception Method Thereof - Google Patents

Abstract

The disclosed embodiment is a sample that receives a QAM symbol of size L It includes a compression precoder, a two-dimensional domain conversion module that converts DD symbols into TF symbols with size M × N in the time-frequency (TF) domain, and a modulator that transmits a transmission signal in the time domain obtained by modulating the TF symbols. Thus, an OTFS system and its transmission/reception method that can improve transmission efficiency while maintaining high compatibility with the OFDM system and performance gains of channel estimation and compensation of the existing OTFS system are provided.

Description

Compression and Recovery based OTFS System for Higher Spectral Efficiency and Transmission/Reception Method Thereof}

The disclosed embodiments relate to an OTFS system and its transmission and reception method, and to a compression and recovery-based OTFS system and its transmission and reception method for improving transmission efficiency.

The next-generation communication system aims to support various terminals (Smart home, wearable devices, unmanned aerial vehicles, high speed-trains, low-Earth-orbit satellites, etc.) anytime, anywhere. Therefore, in the next-generation communication environment, scenarios for high-speed time-varying channels due to the rapid mobility of terminals, that is, channels with high Doppler effect, must be considered. However, the OFDM system previously used in LTE and 5G can only overcome the delay effect caused by multi-path channels, so when trying to estimate a channel where the Doppler effect occurs due to high-speed movement, etc., a lot of overhead must be used. And this causes significant deterioration in channel compensation performance.

To overcome these limitations, effectively estimate channels and achieve excellent channel compensation performance, an Orthogonal Time Frequency Space (OTFS) system has been studied.

Figure 1 shows a schematic structure of an existing OTFS system.

Referring to FIG. 1, in the OTFS system, the transmitting device 10 includes a two-dimensional domain conversion module 11 and an OFDM modulator 12.

In the OTFS system, unlike the Orthogonal Frequency-Division Multiplexing (OFDM) system in which symbols are mapped to the Time-Frequency (TF) domain, symbols are mapped to the Delay-Doppler (DD) domain. Accordingly, the two-dimensional domain conversion module 11 maps the data to be transmitted to the DD domain and converts it into a symbol ( ) is approved. The two-dimensional domain conversion module 11 converts the authorized symbol ( ) is performed on the 2-dimensional inverse Fourier transform, Inverse Symplectic Finite Fourier Transform (ISFFT), and the symbol of the TF domain ( ) is converted to That is, the symbol of the DD domain ( ) as a symbol in the TF domain suitable for OFDM system ( ) is converted to

The OFDM modulator 12 has the same configuration as the modulator of the existing OFDM system, and converts the TF domain symbol ( ) is received and a transmission signal (transmitted in the time domain) is received according to the OFDM modulation method. ), and the transmission signal in the modulated time domain ( ) is transmitted.

Transmission signal transmitted from the transmitting device 10 ( ) is a received signal in the time domain via the channel 20 ( ) is received by the receiving device 30. At this time, the channel 20 has a transmission signal ( ) and received signal ( ) is a doubly dispersive channel that can cause large changes in both time and frequency.

The receiving device 30 may include an OFDM demodulator 31, a two-dimensional domain reconversion module 32, and a channel estimation and equalizer 33.

The OFDM demodulator 31 has the same configuration as the demodulator of the existing OFDM system, and receives a time domain signal ( ) is received, the received signal in the time domain ( ) is demodulated using the OFDM demodulation method for the received signal ( ) as a symbol in the TF domain ( ) is converted to And the two-dimensional domain re-conversion module 32 corresponds to the two-dimensional domain conversion module 11 of the transmitting device 10, and converts the TF domain symbol ( ) is performed on Symplectic Finite Fourier transform (SFFT) to obtain the signal in the TF domain ( ) again as a symbol in the DD domain ( ) is converted to

Symbols in the DD domain ( ) is obtained, the channel estimation and equalizer 33 estimates the state of the dual distribution channel 20, and generates a DD domain symbol ( ) by performing equalization on the transmitted symbol ( ) is estimated and restored.

In this OTFS system, the delay and Doppler elements of the dual distributed channel 20 in the DD domain of the receiving device 30 are applied to symbols through two-dimensional circular convolution, effectively changing the state of the dual distributed channel 20. It can be estimated and compensated.

As shown in Figure 1, the OTFS system is basically a system in which pre-processing and post-processing are applied additionally to the OFDM system, so it has high compatibility with the OFDM system and can effectively utilize the existing OFDM system structure. Additionally, the OTFS system has several advantages compared to the OFDM system, such as low channel estimation overhead, low PAPR (Peak to Average Power Ratio), high diversity gain, and low CP (Cyclic Prefix) overhead.

Therefore, the OTFS system is being studied to maximize the use of the existing OFDM system in order to reduce construction costs while inheriting the advantages of the OFDM system. In other words, the OTFS system must maintain high compatibility with the OFDM system. However, in order to maintain high compatibility with the OFDM system, it is difficult to change the transmission method, making it difficult to conduct research on additional techniques that can improve transmission efficiency.

Korean Patent Publication No. 10-2018-0051485 (published on May 16, 2018)

The disclosed embodiments are aimed at providing an OTFS system and a method for transmitting and receiving the same that can improve transmission efficiency while maintaining high compatibility with the OFDM system.

The disclosed embodiments are aimed at providing an OTFS system and a method for transmitting and receiving the same that can improve transmission efficiency while maintaining the performance gains of channel estimation and compensation of the existing OTFS system.

The transmitting device of the OTFS system according to the embodiment receives a QAM symbol of size L Sample compression precoder that compresses and converts to symbols; a two-dimensional domain conversion module that converts the DD symbol into a TF symbol having an M × N size in the time-frequency (TF) domain; and a modulator that transmits a time domain transmission signal obtained by modulating the TF symbol.

The sample compression precoder performs discrete Fourier transform on each of the N QAM symbol vectors of the QAM symbol and converts them into DD symbols of size L × N, and in each of the N DD symbol vectors of DD symbols of size L × N By excluding L-M elements exceeding M, it can be compressed into a DD symbol with size M × N.

The two-dimensional domain transformation module may perform an inverse symplectic finite Fourier transform on the DD symbol and convert it into the TF symbol.

The two-dimensional domain conversion module modulates the TF symbol according to an OFDM modulation technique to obtain a transmission signal in the time domain, and the obtained transmission signal in the time domain undergoes delay due to multipath and frequency shift due to the Doppler effect. It can be transmitted to the receiving device through a dual distributed channel.

The receiving device of the OTFS system according to the embodiment is a QAM symbol of size L × N (L, N is a natural number) in the transmitting device. A demodulator that receives a received signal that is compressed and converted into a symbol of the time frequency domain (hereinafter referred to as TF), modulated, and transmitted through a channel, and demodulated to obtain a TF symbol of the TF domain; a two-dimensional transform equalizer that reconverts and equalizes the TF symbol to a symbol of the DD domain to obtain a recovered DD symbol; a sample recovery post-processor for obtaining a recovered QAM symbol by expanding and converting the recovered DD symbol having a size of M × N to a size of L × N; And in the recovered QAM symbol, the transmitting device compensates for the ISI generated in the process of compressing the QAM symbol and the recovery process of obtaining the recovered QAM symbol from the recovered DD symbol to obtain a restored QAM symbol corresponding to the QAM symbol. Includes a symbol detector.

The sample recovery post-processor expands the recovered DD symbol to the size L The recovered QAM symbol of size L × N can be obtained by performing inverse discrete Fourier transform on the recovered DD symbol expanded to size N.

The symbol detector may obtain the restored QAM symbol by estimating a value such that each element of the restored QAM symbol has a correlation according to the cyclical characteristic of a correlation matrix representing the ISI generated during the compression and restoration process.

The symbol detector may estimate elements of the reconstructed QAM symbol according to the Maximum-Likelihood Seqeunce Estimation (MLSE) technique.

The demodulator may obtain the TF symbol by demodulating the received signal according to an OFDM demodulation technique.

The two-dimensional transform equalizer performs simplex finite Fourier transform on the TF symbol, converts it into a DD symbol of the DD domain, and equalizes the DD symbol according to the estimated state of the channel to obtain the recovered DD symbol. You can.

The reception method of the OTFS system according to an embodiment is a QAM symbol of size L A step of obtaining a TF symbol of the TF domain by receiving and demodulating a received signal that is compressed and converted into a symbol having a time frequency domain (hereinafter referred to as TF), and then modulated and transmitted through a channel; Obtaining a recovered DD symbol by reconverting and equalizing the TF symbol to a symbol of the DD domain; Obtaining a recovered QAM symbol by expanding and converting the recovered DD symbol having a size of M × N to a size of L × N; And in the recovered QAM symbol, the transmitting device compensates for the ISI generated in the process of compressing the QAM symbol and the recovery process of obtaining the recovered QAM symbol from the recovered DD symbol to obtain a restored QAM symbol corresponding to the QAM symbol. Includes steps.

Therefore, the OTFS system and its transmission and reception method according to the embodiment compress and modulate symbols in the delay Doppler domain and transmit them, demodulate the transmitted signal, and then restore the compression of the symbols in the delay Doppler domain, providing high compatibility with the OFDM system. Transmission efficiency can be improved while maintaining the performance gains of channel estimation and compensation of the existing OTFS system.

Figure 1 shows a schematic structure of an existing OTFS system.
Figure 2 shows a schematic structure of an OTFS system according to one embodiment.
FIG. 3 is a diagram for explaining the operation of the compression precoder of FIG. 2.
Figure 4 is a diagram to explain the relationship between the DD domain and the TF domain.
FIG. 5 is a diagram for explaining the operation of the recovery post-processor of FIG. 2.
Figure 6 shows a transmission and reception method of an OTFS system according to an embodiment.

Hereinafter, specific embodiments of one embodiment will be described with reference to the drawings. The detailed description below is provided to provide a comprehensive understanding of the methods, devices and/or systems described herein. However, this is only an example and the present invention is not limited thereto.

In describing one embodiment, if it is determined that a detailed description of the known technology related to the present invention may unnecessarily obscure the gist of an embodiment, the detailed description will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification. The terminology used in the detailed description is intended to describe only one embodiment and should in no way be limiting. Unless explicitly stated otherwise, singular forms include plural meanings. In this description, expressions such as “comprising” or “including” are intended to indicate certain features, numbers, steps, operations, elements, parts or combinations thereof, and one or more than those described. It should not be construed to exclude the existence or possibility of any other characteristic, number, step, operation, element, or part or combination thereof. In addition, terms such as "... unit", "... unit", "module", and "block" used in the specification refer to a unit that processes at least one function or operation, which is hardware, software, or hardware. and software.

FIG. 2 shows a schematic structure of an OTFS system according to an embodiment, FIG. 3 is a diagram for explaining the operation of the compression precoder of FIG. 2, and FIG. 4 is a diagram for explaining the relationship between the DD domain and the TF domain. am. And FIG. 5 is a diagram for explaining the operation of the recovery post-processor of FIG. 2.

When describing the OTFS system according to the embodiment with reference to FIGS. 2 to 5, first, in the OTFS system, the transmitter 40 includes a sample compression precoder 43, a two-dimensional domain transformation module 41, and an OFDM modulator 42. Includes. That is, the transmitting device 40 of the embodiment further includes a sample compression precoder 43, unlike the transmitting device 10 of FIG. 1.

The sample compression precoder 43 maps the data to be transmitted to the QAM (quadrature amplitude modulation) constellation coordinates and obtains the QAM symbol ( ) is approved. The transmitting device 40 of the embodiment is provided with a sample compression precoder 43, so that, unlike the existing transmitting device 10, the DD domain symbol ( ), not the QAM symbol ( ) is approved. At this time, the QAM symbol ( ) can be obtained as a matrix of size L × N (L, N are natural numbers). Here, a QAM symbol of size L × N ( ) can be seen as consisting of N QAM symbol vectors (q ₀ , q ₁ , …, q _N-1 ), each having L elements.

As shown in Figure 3, the sample compression precoder 43 uses L × N size QAM symbols ( ) is authorized, the authorized QAM symbol ( ) by performing the L-point Discrete Fourier Transform (DFT) to obtain the DD symbol (DD symbol), which is a symbol of the DD domain. ) is converted to

The sample compression precoder 43 generates L × N size QAM symbols ( ), when performing L point DFT on each of the N QAM symbol vectors (q ₀ , q ₁ , …, q _N-1 ), the DD symbol ( )'s N DD symbol vectors (s ₀ ^DD , s ₁ ^DD , ..., s _N-1 ^DD ) each have L elements. However ^{, in} the _{embodiment ,} the sample compression precoder 43 _uses ^M ( Here, by leaving only M < L (natural number) elements and excluding LM elements exceeding M, the DD symbol ( ) is the size of the QAM symbol ( ) is compressed to become smaller than .

That is, the sample compression precoder 43 uses L × N size QAM symbols ( ) is converted to a symbol of the DD domain by performing a discrete Fourier transform, but (LM) × N elements are removed to create a DD symbol ( ) is compressed so that its size is M × N, and the QAM symbol ( ) compared to the DD symbol ( ) to reduce the size.

At this time, the number (M) of elements to be left among the L elements of the DD symbol vector (s ₀ ^DD , s ₁ ^DD , ..., s _N-1 ^DD ) depends on the truncating factor (α) that controls the compression level. It can be determined as M = L×α. Here, as an example, it is assumed that the cutting factor (α) is 0.8, but the cutting factor (α) can be adjusted in various ways.

The two-dimensional domain conversion module 41 converts the DD symbol of the DD domain compressed into M × N size ( ) is authorized and performs ISFFT to create the DD symbol ( ) to the TF symbol ( ) is converted to

Here, the DD domain and the TF domain are different domains. If the TF domain is a domain to express the time and frequency changes that each symbol experiences while passing through the channel, the DD domain is the delay and Doppler effect caused by the channel in the signal. This is a domain to express . According to the relationship between the DD domain and the TF domain shown in FIG. 4, the DD symbol ( ), when ISFFT is performed on DD symbol ( ), M delay components are converted into M frequency components, and N Doppler components are converted into N time components to form M × N sized TF symbols ( ) can be obtained. Therefore, the TF symbol ( ) can also be converted to a matrix of size M × N.

Here, M and N are each TF symbol ( ) can be viewed as the number of subcarrier indexes and time indexes for each frequency.

The OFDM modulator 42 converts the TF symbol output from the two-dimensional domain conversion module 41 ( ) was approved, and the TF symbol ( ) OFDM modulation that sequentially allocates subcarriers according to the subcarrier index (m = {0, 1, …, M-1}) according to the time index (n = {0, 1, …, N-1}) Depending on the method, the TF symbol ( ) to the time domain signal ( ) is modulated. That is, in each of the N time intervals, M subcarriers are TF symbols ( ) to have an intensity according to the corresponding element.

And the transmitted signal in the modulated time domain ( ) is transmitted to be received by the receiving device 50 through the dual distribution channel 20. In the embodiment, the OFDM modulator 42 of the transmitting device 40 is configured to be the same as the transmitting device of the existing OFDM system in order to maintain compatibility with the transmitting device of the existing OFDM system. Therefore, the detailed configuration of the OFDM modulator 42 will not be described here.

The receiving device 50 receives a time domain received signal ( ) is approved. At this time, the received signal ( ) is the transmission signal ( ) is transmitted to the receiving device 50 moving at high speed through multiple paths, not only is it delayed in terms of time while passing through the dual distributed channel 20, but also a change in frequency occurs due to the Doppler effect, so that the receiving device 50 ) is the signal received.

The receiving device 50 is equipped with an OFDM demodulator 51, a 2-dimensional domain reconversion module 52, and a channel estimation and equalizer 33 in the same way as the receiving device 30 of the existing OTFS system shown in FIG. 1. do. However, the receiving device 50 according to the embodiment may include a sample recovery post-processor 54 and a symbol detector 55 compared to the existing receiving device 30.

The OFDM demodulator 51 applies delay and Doppler effects while being transmitted through the dual distributed channel 20 to produce a received signal in the time domain ( ) according to the OFDM demodulation method for the received signal ( ) by performing demodulation on the TF symbol ( ) to obtain. The OFDM demodulator 51 receives signals transmitted through a plurality of temporally separated subcarriers ( ), by identifying the signal transmitted on each subcarrier in each time interval, a TF symbol of size M × N ( ) can be obtained.

Here, the OFDM demodulator 51 may also be configured the same as the receiving device of the existing OFDM system in order to maintain compatibility with the receiving device of the existing OFDM system. Therefore, the detailed configuration of the OFDM demodulator 51 will not be described here. No.

And the two-dimensional domain reconversion module 52 converts the TF symbol (TF) obtained from the OFDM demodulator 51 ) by performing SFFT on the TF symbol ( ) to the DD symbol ( ) is converted to In this case as well, as shown in FIG. 4, the two-dimensional domain reconversion module 52 uses the TF symbol ( ), the TF symbol ( ), the frequency components according to the M subcarrier indices (m) are converted into M delay components, and the time components according to the N time indices (n) are converted into N Doppler components, resulting in M × N sized DD symbols. ( ) is obtained.

The acquired DD symbol ( ) is a symbol that reflects the delay and frequency shift due to Doppler that occurred depending on the channel state while passing through the dual distributed channel 20, so the channel estimation and equalizer 53 determines the state of the dual distributed channel 20 during the transmission process. is estimated, and the DD symbol ( ) by performing equalization on the transmitted DD symbol ( ) corresponding to the recovery DD symbol ( ) to obtain. Here, DD symbols of size M × N ( The recovery DD symbol (obtained from ) ) is also obtained in size M × N.

The two-dimensional domain retransformation module 52 and the channel estimation and equalizer 53 can be integrated and expressed as a two-dimensional transform equalizer.

After the OTFS system first acquires the DD symbol of the DD domain, converting it to a TF symbol suitable for OFDM can easily estimate and compensate for channel effects such as delay and Doppler depending on the state of the dual distributed channel 20 and perform equalization. This is to enable this, and since this is a concept already implemented in the existing OFTS system, detailed description is omitted here.

The sample recovery post-processor 54, which is additionally provided in the receiving device 50 of the embodiment, compresses and transmits the DD symbol (DD symbol) from the L × N size to the M × N size. ) recovered DD symbols of size M × N ( ) is sampled and restored to its pre-compressed L × N size to recover the QAM symbol ( ) to obtain.

As shown in Figure 5, the sample recovery post-processor 54 shown is a recovery DD symbol ( ) by performing L-point Inverse Discrete Fourier Transform (DFT) on the recovered QAM symbol ( ) to obtain. However, the recovery DD symbol ( ) has size M × N, so the recovery DD symbol ( ) of N recovered DD symbol vectors ( ) Each has M elements. Therefore, the recovery DD symbol ( ), it is not possible to perform the L point DFT as is, so the sample recovery postprocessor 54 uses the recovery DD symbol ( ) of N recovered DD symbol vectors ( ) After additionally inserting (LM) zeros into each, L point DFT is performed to obtain N restored QAM symbol vectors ( ), the recovery QAM symbol of size L × N ( ) can be obtained. That is, the transmitting device 40 sends an L × N size QAM symbol ( ) into DD symbols compressed to M × N size ( ) The number of symbol elements removed in the process of obtaining ) is filled by padding with 0 symbols.

The symbol detector 55 detects the recovery QAM symbol ( QAM symbol (QAM symbol) authorized from ) to the transmitting device 40 ) corresponding to the restored QAM symbol ( ) is estimated and detected.

Recovery QAM symbol ( ) means that the transmitting device 40 displays an L × N size QAM symbol ( ) into a DD symbol of size M × N ( ), information is lost in the process of compression, and the transmitted symbol elements are randomly filled with 0 symbol padding to restore the L × N size, so the recovered QAM symbol ( ) is the QAM symbol ( ) cannot be responded to. Accordingly, the symbol detector 55 generates a recovered QAM symbol ( ) from the QAM symbol ( ) corresponding to the restored QAM symbol ( ) is estimated and detected.

The ISI that appears during the compression and restoration process is expressed in the form of a correlation matrix (C) as shown in Equation 1.

where α is the cutting factor, and M = αL.

And in the correlation matrix (C) of Equation 1, each element (c[m,n]) is specified by Equation 2.

In the correlation matrix (C) of Equation 1, non-diagonal elements that are not 0 are interference components that appear during the compression and recovery process.

Accordingly, the symbol detector 55 generates a recovery QAM symbol ( ) by repeating and cyclically estimating the elements of the restored QAM symbol ( ) can be obtained.

Here, the symbol detector 55 applies the Maximum-Likelihood Seqeunce Estimation (MLSE) technique to reconstruct the QAM symbol ( ) can be detected.

That is, the symbol detector 55 is based on the MLSE technique to recover the QAM symbol ( ), by estimating the optimal value of the missing element to match the correlation according to the circulant characteristic of the correlation matrix (C), the recovery QAM symbol ( ), the restored QAM symbol ( ) can be obtained. Here, the symbol detector 55 may be implemented as a Trellis detector, for example.

In the OTFS system of the embodiment shown in FIG. 2, the sample compression precoder 43 of the transmitting device 40 uses a QAM symbol of L × N size ( ) into M × N sized DD symbols ( ), and in the receiving device 50, the sample recovery post-processor 54 and the symbol detector 55 perform the received signal ( ) The recovered DD symbol of size M × N obtained from ( ) from the restored QAM symbol of size L × N ( ) is different from the existing OTFS system shown in FIG. 1 only in that it restores It is completely identical to the OTFS system.

Therefore, a QAM symbol of size L × N ( ) into a DD symbol of size M × N ( ) and recovery DD symbols of size M × N ( ) from the restored QAM symbol of size L × N ( ) The ISI that occurs in the process of restoring ) does not affect the channel estimation and compensation process, which operates the same as the existing OTFS system. This is because the precoding and post-processing processes are performed before and after the existing OTFS system configuration, so the compression and restoration process can be separated from the channel estimation and compensation process and processed independently.

Additionally, the DD symbol ( Since the covariance matrix of ) forms an identity matrix due to the characteristics of the sample compression precoder (43), the DD symbol ( ) has independent and identically distributed (iid) properties. The OTFS system defaults to the DD symbol (DD symbol) in the DD domain. ) is structured to maintain the iid characteristics, and thus the compression and restoration process before and after the DD domain can be performed separately from the channel estimation and compensation process of the OTFS system.

As a result, the OTFS system of the embodiment allows the transmitting device 40 to transmit a QAM symbol of size L × N ( ) into M × N sized DD symbols ( ), then the compressed and converted DD symbol ( ) based on the transmission signal ( ) is generated and transmitted, and the receiving device 50 receives the received signal ( ), a recovery DD symbol of size M × N is obtained ( ) from the restored QAM symbol of size L × N ( ) can be obtained. Therefore, the size of each symbol can be reduced by (LM) × N, thereby improving transmission efficiency. At this time, the configuration of the existing OTFS system remains the same, so compatibility with the OFDM system, which is one of the advantages of the OTFS system, can also be maintained.

In the illustrated embodiment, each component may have different functions and capabilities in addition to those described below, and may include additional components other than those described below. Additionally, in one embodiment, each configuration may be implemented using one or more physically separate devices, one or more processors, or a combination of one or more processors and software, and, unlike the example shown, may be implemented in specific operations. It may not be clearly distinguished.

And the transmitting device 40 and receiving device 50 of the OTFS system shown in FIG. 2 may be implemented within a logic circuit by hardware, firmware, software, or a combination thereof, and may be implemented using a general-purpose or special-purpose computer. It could be. The device may be implemented using hardwired devices, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc. Additionally, the device may be implemented as a System on Chip (SoC) including one or more processors and a controller.

In addition, the transmitting device 40 and receiving device 50 of the OTFS system may be mounted on a computing device or server equipped with hardware elements in the form of software, hardware, or a combination thereof. A computing device or server includes all or part of a communication device such as a communication modem for communicating with various devices or wired and wireless communication networks, a memory for storing data to execute a program, and a microprocessor for executing a program to perform calculations and commands. It can refer to a variety of devices, including:

Figure 6 shows a transmission and reception method of an OTFS system according to an embodiment.

Referring to FIGS. 2 to 5, the transmission method 60 performed in the transmission device 40 of the OTFS system of the embodiment first uses a QAM symbol (QAM symbol) obtained by QAM mapping the data to be transmitted. ) is approved (61). QAM symbol ( ) is approved, the QAM symbol ( ) by performing DFT on the DD symbol (DD symbol, which is a symbol of the DD domain) ) (62). At this time, a QAM symbol of size L × N ( ) by performing L-point DFT on each of the N QAM symbol vectors (q ₀ , q ₁ , …, q _N-1 ) to obtain N DD symbol vectors (s ₀ ^DD , s 1 DD , s 0 DD , s ₁ ^DD , …, s _N-1 ^DD ) is obtained, then LM elements exceeding M are excluded from each of the N DD symbol vectors (s ₀ ^DD , s ₁ ^DD , …, s _N-1 ^DD ), resulting in M × N. DD symbols compressed to size ( ) to obtain.

Afterwards, a DD symbol of size M × N ( ) by performing ISFFT, a two-dimensional inverse Fourier transform, on DD symbols of size M × N ( ) into a TF symbol of size M × N ( ) (63). TF symbol of size M × N ( ) is acquired, the acquired TF symbol ( ) is OFDM modulated to transmit the signal ( ) is acquired, and the acquired transmission signal ( ) is transmitted to the receiving device 50 through the dual distribution channel 20 (64).

Meanwhile, the reception method 70 performed in the reception device 50 of the OTFS system is a transmission signal transmitted from the transmission device 40 ( ) is transmitted through the dual distributed channel 20, a received signal ( ) is applied, the received signal ( ) by performing OFDM demodulation on the TF symbol ( ) obtain (72). And the TF symbol ( ) by performing SFFT, a two-dimensional Fourier transform, on the TF symbol ( ) to the DD symbol ( ) (73). And by estimating the state of the dual distribution channel 20, the DD symbol ( ) by equalizing the transmitted signal ( ) compensates for the delay and Doppler that occurred while being transmitted through the dual distributed channel 20 to create a recovery DD symbol ( ) obtain (73). At this time, the state of the dual distribution channel 20 is estimated and the DD symbol ( ) can be performed in the same way as the existing OTFS system.

Recovery DD symbol ( ) is obtained, a recovered DD symbol of size M × N equalized and compensated in the DD domain ( ) by padding the 0 symbols, creating a recovery DD symbol ( ) is restored to L × N size, and then the recovered DD symbol ( ) by performing an L-point IDFT on L × N-sized recovered QAM symbols ( ) (74).

Here you can see the recovery QAM symbol ( ) is the recovery DD symbol ( ) by padding 0 symbols to expand the size, and since it is an IDFT converted symbol, the transmitting device 40 uses a QAM symbol of size L × N ( ) is a DD symbol of size M × N ( ), the information of the elements removed during the compression conversion process is not included, and ISI is generated through the compression and restoration process. At this time, the generated ISI follows the correlation matrix (C), so the recovery QAM symbol ( ) By estimating the elements of the restored QAM symbol ( ) obtain (75).

In FIG. 6, each process is described as being executed sequentially, but this is only an illustrative explanation, and those skilled in the art can change the order shown in FIG. 5 and execute it without departing from the essential characteristics of the embodiments of the present invention. Alternatively, it can be applied through various modifications and modifications by executing one or more processes in parallel or adding other processes.

Although the present invention has been described in detail through representative embodiments above, those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the attached claims.

40: Transmitting device 41: Two-dimensional domain conversion module
42: OFDM modulator 43: sample compression precoder
51: OFDM demodulator 52: 2-dimensional domain reconversion module
53: Channel estimation and equalizer 54: Sample recovery postprocessor
55: Symbol detector

Claims (20)

A sample compression precoder that receives a QAM symbol of size L
a two-dimensional domain conversion module that converts the DD symbol into a TF symbol having an M × N size in the time-frequency (TF) domain; and
A transmission device in an OTFS system including a modulator that transmits a time domain transmission signal obtained by modulating the TF symbol. The method of claim 1, wherein the sample compression precoder
Discrete Fourier transform is performed on each of the N QAM symbol vectors of the QAM symbol and converted into a DD symbol of size L × N,
A transmitting device in an OTFS system that excludes LM elements exceeding M from each of the N DD symbol vectors of a DD symbol of size L × N and compresses them into DD symbols having size M × N. The method of claim 1, wherein the two-dimensional domain transformation module
A transmitting device in an OTFS system that performs an inverse symplectic finite Fourier transform on the DD symbol and converts it into the TF symbol. The method of claim 1, wherein the two-dimensional domain transformation module
Obtaining a transmission signal in the time domain by modulating the TF symbol according to an OFDM modulation technique,
A transmitting device in an OTFS system that transmits the acquired transmission signal in the time domain to a receiving device through a dual distributed channel that causes delay due to multiple paths and frequency shift due to the Doppler effect. In the transmitting device, a QAM symbol of size L A demodulator that obtains a TF symbol of the TF domain by receiving and demodulating the received signal, which is converted into a symbol of TF) and then modulated and transmitted through a channel;
a two-dimensional transform equalizer that reconverts and equalizes the TF symbol to a symbol of the DD domain to obtain a recovered DD symbol;
a sample recovery post-processor for obtaining a recovered QAM symbol by expanding and converting the recovered DD symbol having a size of M × N to a size of L × N; and
A symbol for obtaining a restored QAM symbol corresponding to the QAM symbol by compensating for ISI generated in the restored QAM symbol during the process of the transmitting device compressing the QAM symbol and the restoration process of obtaining the restored QAM symbol from the restored DD symbol. Receiving device of an OTFS system containing a detector. The method of claim 5, wherein the sample recovery postprocessor
In the recovered DD symbol having a size of M
A receiving device in an OTFS system that performs an inverse discrete Fourier transform on the recovered DD symbol expanded to L × N size to obtain the recovered QAM symbol of L × N size. The method of claim 6, wherein the symbol detector is
A receiving device in an OTFS system that obtains the restored QAM symbol by estimating a value such that each element of the restored QAM symbol has a correlation according to the cyclical characteristics of a correlation matrix representing ISI generated during compression and restoration. The method of claim 7, wherein the symbol detector is
A receiving device in an OTFS system that estimates elements of the restored QAM symbol according to the Maximum-Likelihood Seqeunce Estimation (MLSE) technique. The method of claim 5, wherein the demodulator
A receiving device in an OTFS system that obtains the TF symbol by demodulating the received signal according to an OFDM demodulation technique. The method of claim 5, wherein the two-dimensional transform equalizer
Performing a simplex finite Fourier transform on the TF symbol and converting it to a DD symbol in the DD domain,
A receiving device in an OTFS system that equalizes the DD symbol according to the estimated state of the channel to obtain the recovered DD symbol. The method of claim 5, wherein the received signal is
The transmitting device performs discrete Fourier transform on each of the N QAM symbol vectors of the QAM symbol and converts them into symbols of size L × N in the DD domain,
A transmission signal obtained from a symbol compressed into a size of M × N by excluding LM elements exceeding M from each of the N symbol vectors in a symbol of the size of L receiving device in an OTFS system. The method of claim 11, wherein the transmission signal is
A receiving device in an OTFS system obtained by performing OFDM modulation on symbols in the TF domain, which are obtained by performing inverse symplectic finite Fourier transform on symbols in the DD domain compressed to M × N size. The method of claim 11, wherein the channel is
A receiving device for the OTFS system, a dual distributed channel in which delay due to multipath and frequency shift due to the Doppler effect are induced. In the transmitting device of the OTFS system, a QAM symbol of size L Obtaining a TF symbol of the TF domain by receiving and demodulating a received signal converted to a symbol of a domain (hereinafter referred to as TF) and then modulated and transmitted through a channel;
Obtaining a recovered DD symbol by reconverting and equalizing the TF symbol to a symbol of the DD domain;
Obtaining a recovered QAM symbol by expanding and converting the recovered DD symbol having a size of M × N to a size of L × N; and
Obtaining a restored QAM symbol corresponding to the QAM symbol by compensating for the ISI generated in the restored QAM symbol during the process of the transmitting device compressing the QAM symbol and the restoration process of obtaining the restored QAM symbol from the restored DD symbol. A receiving method in an OTFS system including. The method of claim 14, wherein the step of obtaining the recovered QAM symbol is
In the recovered DD symbol having a size of M
A reception method in an OTFS system for obtaining the recovered QAM symbol of L × N size by performing an inverse discrete Fourier transform on the recovered DD symbol expanded to L × N size. The method of claim 15, wherein the step of obtaining the restored QAM symbol is
A reception method in an OTFS system for obtaining the restored QAM symbol by estimating a value such that each element of the restored QAM symbol has a correlation according to the cyclical characteristics of a correlation matrix representing ISI generated during compression and restoration. The method of claim 16, wherein the step of obtaining the restored QAM symbol is
A reception method in an OTFS system for estimating elements of the restored QAM symbol according to the Maximum-Likelihood Seqeunce Estimation (MLSE) technique. The method of claim 14, wherein the step of obtaining the TF symbol is
A reception method in an OTFS system in which the received signal is demodulated according to an OFDM demodulation technique to obtain the TF symbol. The method of claim 14, wherein obtaining the recovered DD symbol includes
Performing a simplex finite Fourier transform on the TF symbol and converting it to a DD symbol in the DD domain,
A reception method in an OTFS system for obtaining the recovered DD symbol by equalizing the DD symbol according to the estimated state of the channel. The method of claim 14, wherein the received signal is
The transmitting device performs discrete Fourier transform on each of the N QAM symbol vectors of the QAM symbol and converts them into symbols of size L × N in the DD domain,
A transmission signal obtained from a symbol compressed into a size of M × N by excluding LM elements exceeding M from each of the N symbol vectors in a symbol of the size of L Receiving method in OTFS system.