EP-4742604-A1 - OTFS BASED WAVEFORM DESIGN FOR ISAC SYSTEM AND SENSING METHOD

EP4742604A1EP 4742604 A1EP4742604 A1EP 4742604A1EP-4742604-A1

Abstract

Disclosed are a method for transmission waveform design for an orthogonal time frequency space (OTFS)-based integrated sensing and communication (ISAC) system, and sensing technology. A sensing method for an OTFS-based ISAC system may include generating a time-frequency domain sample including a delay pilot and a Doppler pilot each that is designed in the time-frequency domain based on data to be transmitted; generating an integrated sensing and communication (ISAC) signal through an orthogonal frequency division multiplexing (OFDM) modulation technique for the generated time-frequency domain sample; and acquiring a sensing parameter through a reflected signal received from a sensing target as the generated ISAC signal is transmitted.

Inventors

PARK, HYUNCHEOL
Han, Junhee

Assignees

Korea Advanced Institute of Science and Technology

Dates

Publication Date: 20260513
Application Date: 20251104

Claims (15)

A sensing method for an orthogonal time frequency space (OTFS)-based integrated sensing and communication (ISAC) system, the sensing method comprising: generating a time-frequency domain sample including a delay pilot and a Doppler pilot each that is designed in the time-frequency domain based on data to be transmitted; generating an integrated sensing and communication (ISAC) signal through an orthogonal frequency division multiplexing (OFDM) modulation technique for the generated time-frequency domain sample; and acquiring a sensing parameter through a reflected signal received from a sensing target as the generated ISAC signal is transmitted.
The sensing method of claim 1, wherein the generating of the time-frequency domain sample comprises generating a data matrix including random quadrature amplitude modulation (QAM) symbols to form the Doppler pilot, generating the Doppler pilot in the delay-Doppler domain using the generated data matrix, and transforming the Doppler pilot generated in the delay-Doppler domain to the time-frequency domain through Fourier transform.
The sensing method of claim 2, wherein the generating of the time-frequency domain sample comprises generating the delay pilot for estimating delay in the time-frequency domain.
The sensing method of claim 2, wherein the generating of the time-frequency domain sample comprises generating the time-frequency domain sample including the Doppler pilot transformed to the time-frequency domain and the generated delay pilot.
The sensing method of claim 1, wherein the acquiring comprises acquiring a plurality of time domain samples corresponding to a specific OFDM symbol, selecting a sample with the largest amplitude, and if the magnitude of the selected sample with the largest amplitude in a specific delay slot of the time domain is greater than or equal to a threshold, determining that the reflected signal from the sensing target is returned after being delayed by a corresponding time interval.
The sensing method of claim 5, wherein the acquiring comprises estimating delay and a channel coefficient using the determined reflected signal, and estimating Doppler and a final channel coefficient using the estimated delay and channel coefficient.
The sensing method of claim 6, wherein the acquiring comprises acquiring fractional Doppler by dividing the magnitude of the channel coefficient acquired through the delay pilot and Doppler pilot power by the magnitude of the Doppler pilot, by generating an equation for a sine function, and by converting the generated equation to a polynomial equation using Talyor expansion.
A non-transitory computer-readable recording medium storing a computer program to execute a sensing method for an orthogonal time frequency space (OTFS)-based integrated sensing and communication (ISAC) system, wherein the sensing method comprises: generating a time-frequency domain sample including a delay pilot and a Doppler pilot each that is designed in the time-frequency domain based on data to be transmitted; generating an integrated sensing and communication (ISAC) signal through an orthogonal frequency division multiplexing (OFDM) modulation technique for the generated time-frequency domain sample; and acquiring a sensing parameter through a reflected signal received from a sensing target as the generated ISAC signal is transmitted.
An orthogonal time frequency space (OTFS)-based integrated sensing and communication (ISAC) system comprising: a sample generator configured to generate a time-frequency domain sample including a delay pilot and a Doppler pilot each that is designed in the time-frequency domain based on data to be transmitted; a signal generator configured to generate an integrated sensing and communication (ISAC) signal through an orthogonal frequency division multiplexing (OFDM) modulation technique for the generated time-frequency domain sample; and a sensing acquisition unit configured to acquire a sensing parameter through a reflected signal received from a sensing target as the generated ISAC signal is transmitted.
The ISAC system of claim 9, wherein the sample generator is configured to generate a data matrix including random quadrature amplitude modulation (QAM) symbols to form the Doppler pilot, to generate the Doppler pilot in the delay-Doppler domain using the generated data matrix, and to transform the Doppler pilot generated in the delay-Doppler domain to the time-frequency domain through Fourier transform.
The ISAC system of claim 10, wherein the sample generator is configured to generate the delay pilot for estimating delay in the time-frequency domain.
The ISAC system of claim 10, wherein the sample generator is configured to generate the time-frequency domain sample including the Doppler pilot transformed to the time-frequency domain and the generated delay pilot.
The ISAC system of claim 9, wherein the sensing acquisition unit is configured to acquire a plurality of time domain samples corresponding to a specific OFDM symbol, to select a sample with the largest amplitude, and to if the magnitude of the selected sample with the largest amplitude in a specific delay slot of the time domain is greater than or equal to a threshold, determine that the reflected signal from the sensing target is returned after being delayed by a corresponding time interval.
The ISAC system of claim 13, wherein the sensing acquisition unit is configured to estimate delay and a channel coefficient using the determined reflected signal, and to estimate Doppler and a final channel coefficient using the estimated delay and channel coefficient.
The ISAC system of claim 14, wherein the sensing acquisition unit is configured to acquire fractional Doppler by dividing the magnitude of the channel coefficient acquired through the delay pilot and Doppler pilot power by the magnitude of the Doppler pilot, by generating an equation for a sine function, and by converting the generated equation to a polynomial equation using Talyor expansion.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) BACKGROUND 1. Field of the Invention Example embodiments of the following description relate to technology for waveform design and sensing parameter estimation of an integrated sensing and communication (ISAC) system using orthogonal time frequency space (OTFS) modulation. 2. Description of the Related Art Orthogonal time frequency space (OTFS) modulation maps a quadrature amplitude modulation (QAM) data symbol to the delay-Doppler domain to be spread in the time-frequency domain. This technology is attracting attention as a waveform capable of replacing orthogonal frequency division multiplexing (OFDM) that maps a data symbol to the frequency domain in a time-varying channel. It is known that the time-varying channel has a sparse form when transformed to the delay-Doppler domain, and each parameter represents the radial distance between a transmitter and a target and the radial velocity of the target. Therefore, radar sensing and channel estimation may be integrated. A transmitter of a communication system transmits a pilot alone for channel estimation or simultaneously transmits the pilot by adding the pilot to a communication waveform. A transmission signal is reflected from an object and returns to the transmitter or reaches a target receiver. In both cases, the signal is modeled as having passed through each corresponding channel. In the delay-Doppler domain, resources for the pilot and resources for a guard area need to be allocated for channel estimation. Here, the size of researches varies depending on the pilot and the guard area depends on Doppler dispersion and delay of the channel. The Doppler dispersion is not localized on a delay-Doppler grid due to presence of fractional Doppler. Accordingly, the overhead by the pilot and the guard area becomes very large proportional to the product of the delay and the Doppler dispersion. Also, if simultaneously considering Doppler and delay when performing pulse compression, it is difficult to use a high-speed algorithm, which leads to increasing complexity. SUMMARY The present invention proposes a method of reducing the overhead by measuring delay and Doppler from different pilots, realizing fast pulse compression using a fast Fourier transform algorithm, and at the same time, generating communication data into a transmittable orthogonal time frequency space (OTFS) frame, and a sensing parameter estimation method. According to an aspect, a sensing method for an orthogonal time frequency space (OTFS)-based integrated sensing and communication (ISAC) system may include generating a time-frequency domain sample including a delay pilot and a Doppler pilot each that is designed in the time-frequency domain based on data to be transmitted; generating an integrated sensing and communication (ISAC) signal through an orthogonal frequency division multiplexing (OFDM) modulation technique for the generated time-frequency domain sample; and acquiring a sensing parameter through a reflected signal received from a sensing target as the generated ISAC signal is transmitted. The generating of the time-frequency domain sample may include generating a data matrix including random quadrature amplitude modulation (QAM) symbols to form the Doppler pilot, generating the Doppler pilot in the delay-Doppler domain using the generated data matrix, and transforming the Doppler pilot generated in the delay-Doppler domain to the time-frequency domain through Fourier transform. The generating of the time-frequency domain sample may include generating the delay pilot for estimating delay in the time-frequency domain. The generating of the time-frequency domain sample may include generating the time-frequency domain sample including the Doppler pilot transformed to the time-frequency domain and the generated delay pilot. The acquiring may include acquiring a plurality of time domain samples corresponding to a specific OFDM symbol, selecting a sample with the largest amplitude, and if the magnitude of the selected sample with the largest amplitude in a specific delay slot of the time domain is greater than or equal to a threshold, determining that the reflected signal from the sensing target is returned after being delayed by a corresponding time interval. The acquiring may include estimating delay and a channel coefficient using the determined reflected signal, and estimating Doppler and a final channel coefficient using the estimated delay and channel coefficient. The acquiring may include acquiring fractional Doppler by dividing the magnitude of the channel coefficient acquired through the delay pilot and Doppler pilot power by the magnitude of the Doppler pilot, by generating an equation for a sine function, and by converting the generated equation to a polynomial equation using Talyor expansion. According to an aspect, in a non-transitory computer-readable recording medium storing a computer program to execute a sensing method for an OTFS-bas