On the Effectiveness of OTFS for Joint Radar and Communication

TL;DR

This paper demonstrates that OTFS modulation enables efficient joint radar and communication, achieving high data rates and accurate radar parameter estimation in vehicular scenarios, outperforming existing methods.

Contribution

It introduces an efficient approximation for radar parameter estimation and a soft-output detection scheme exploiting channel sparsity in OTFS for joint radar-communication.

Findings

OTFS achieves radar estimation accuracy comparable to FMCW.

The proposed detector outperforms state-of-the-art solutions.

Joint operation with OTFS maintains full data rate and near-optimal radar estimation.

Abstract

We consider a joint radar estimation and communication system using orthogonal time frequency space (OTFS) modulation. The scenario is motivated by vehicular applications where a vehicle equipped with a mono-static radar wishes to communicate data to its target receiver, while estimating parameters of interest related to this receiver. In a point-to-point communication setting over multi-path time-frequency selective channels, we study the joint radar and communication system from two perspectives, i.e., the radar estimation at the transmitter as well as the symbol detection at the receiver. For the radar estimation part, we derive an efficient approximated Maximum Likelihood algorithm and the corresponding Cram\'er- Rao lower bound for range and velocity estimation. Numerical examples demonstrate that multi-carrier digital formats such as OTFS can achieve as accurate radar estimation as state-of-the-art radar waveforms such as frequency-modulated continuous wave (FMCW). For the data detection part, we focus on separate detection and decoding and consider a soft-output detector that exploits efficiently the channel sparsity in the Doppler-delay domain. We quantify the detector performance in terms of its pragmatic capacity, i.e. the achievable rate of the channel induced by the signal constellation and the detector soft output. Simulations show that the proposed scheme outperforms concurrent state-of-the-art solutions. Overall, our work shows that a suitable digitally modulated waveform enables to efficiently operate joint radar and communication by achieving full information rate of the modulation and near-optimal radar estimation performance. Furthermore, OTFS appears to be particularly suited to the scope.