Hybrid Digital-Analog Beamforming and MIMO Radar with OTFS Modulation

Abstract

Motivated by future automotive applications, we study some joint radar target detection and parameter estimation problems where the transmitter, equipped with a mono-static MIMO radar, wishes to detect multiple targets and then estimate their respective parameters, while simultaneously communicating information data using orthogonal time frequency space (OTFS) modulation. Assuming that the number of radio frequency chains is smaller than the number of antennas over the mmWave frequency band, we design hybrid digital-analog beamforming at the radar transmitter adapted to different operating phases. The first scenario considers a wide angular beam in order to perform the target detection and parameter estimation, while multicasting a common message to all possible active users. The second scenario considers narrow angular beams to send information streams individually to the already detected users and simultaneously keep tracking of their respective parameters. Under this setup, we propose an efficient maximum likelihood scheme combined with hybrid beamforming to jointly perform target detection and parameter estimation. Our numerical results demonstrate that the proposed algorithm is able to reliably detect multiple targets with a sufficient number of antennas and achieves the Cramér-Rao lower bound for radar parameter estimation such as delay, Doppler and angle-of-arrival (AoA).

Integrated Sensing and Communication-assisted Orthogonal Time Frequency Space Transmission for Vehicular Networks

“…Observed from (25), for the angle relative to each vehicle, an exhausted search in the set Θ is required to find the optimal estimate. To reduce the estimation complexity, we could only choose the values in the set Θ that are close to the predicted angle θi to find the estimated angle θi that maximizes the likelihood function p(r i |θ i ).…”

“…To realize the dual goal of sensing and communication, a maximum likelihood (ML) estimator was designed for estimating the sensing parameters from the echoes at the RSU, while message passing algorithm (MPA)-based receivers were adopted for data detection at the vehicles. On the other hand, OTFS-based radar sensing system with multiple-input multiple-output (MIMO) was developed in [25], where a hybrid digital-analog beamforming design was devised for parameter estimation and tracking. Both works have demonstrated the effectiveness of OTFS signaling for communication and sensing.…”

A Novel ISAC Transmission Framework based on Spatially-Spread Orthogonal Time Frequency Space Modulation

“…For example, the effectiveness of OTFS modulation for ISAC transmission has been evaluated in [12], where the authors have shown that the estimation error lower bounds for radar sensing can be achieved by using OTFS signals while maintaining a satisfactory communication performance. Then, this work has then been extended to the case of multiple-input multiple-output (MIMO) [13], where a hybrid digital-analog beamforming is devised for both radar sensing and communication. In addition, the author in [13] have also developed an efficient maximum-likelihood (ML) algorithm to facilitate target detection and parameter estimation.…”

“…Then, this work has then been extended to the case of multiple-input multiple-output (MIMO) [13], where a hybrid digital-analog beamforming is devised for both radar sensing and communication. In addition, the author in [13] have also developed an efficient maximum-likelihood (ML) algorithm to facilitate target detection and parameter estimation.…”

“…On the other hand, the downlink communication transmission is designed based on the CSI obtained from radar sensing, such that it can bypass the need of channel estimation and equalization at the receiver side. Although the applications of OTFS modulation in ISAC transmissions have shown promising performances, they often rely on sophisticated beamforming schemes [4], [13] that are designed according to the CSI at transmitter (CSIT). However, it should be noted that for some practical scenarios, such as co-located radar and communication antennas, channel fading coefficients for communication cannot be directly obtained from radar sensing.…”