Virtual Array for Dual Function MIMO Radar Communication Systems using OTFS Waveforms

Virtual Array for Dual Function MIMO Radar Communication Systems using OTFS Waveforms
Notice: This research summary and analysis were automatically generated using AI technology. For absolute accuracy, please refer to the [Original Paper Viewer] below or the Original ArXiv Source.

A MIMO dual-function radar communication (DFRC) system transmitting orthogonal time frequency space (OTFS) waveforms is considered. A key advantage of MIMO radar is its ability to create a virtual array, achieving higher sensing resolution than the physical receive array. In this paper, we propose a novel approach to construct a virtual array for the system under consideration. The transmit antennas can use the Doppler-delay (DD) domain bins in a shared fashion. A number of Time-Frequency (TF) bins, referred to as private bins, are exclusively assigned to specific transmit antennas. The TF signals received on the private bins are orthogonal and thus can be used to synthesize a virtual array, which, combined with coarse knowledge of radar parameters (i.e., angle, range, and velocity), enables high-resolution estimation of those parameters. The introduction of $N_p$ private bins necessitates a reduction in DD domain symbols, thereby reducing the data rate of each transmit antenna by $N_p-1$. However, even a small number of private bins is sufficient to achieve significant sensing gains with minimal communication rate loss.


💡 Research Summary

The paper addresses the design of a dual‑function radar‑communication (DFRC) system that simultaneously performs sensing and data transmission using a multiple‑input multiple‑output (MIMO) architecture and orthogonal time‑frequency space (OTFS) waveforms. OTFS is chosen because it maps the time‑varying wireless channel into the Doppler‑delay (DD) domain where the channel appears linear and time‑invariant, thereby overcoming the inter‑carrier interference and channel‑estimation challenges that plague OFDM in high‑mobility scenarios such as high‑speed rail or vehicular networks.

In conventional MIMO DFRC designs, two extreme approaches have been explored. The first lets all transmit antennas share the entire DD grid, maximizing spectral efficiency for communication but coupling the transmitted symbols with radar parameters, which forces a high‑complexity joint maximum‑likelihood (ML) estimation at the radar receiver. The second assigns each antenna an exclusive portion of the DD grid, guaranteeing orthogonal radar returns and enabling a virtual array, but at the cost of a severe reduction in communication data rate because many DD symbols become unavailable for data.

The authors propose a middle‑ground solution that introduces a small number (N_{p}) of private time‑frequency (TF) bins. These bins are exclusively paired with specific transmit antennas, while the remaining TF bins are shared among all antennas. Because the signals transmitted on private bins are orthogonal across antennas, the radar receiver can isolate the returns from each antenna on those bins and synthesize a virtual array whose aperture is effectively multiplied by the number of transmit antennas that have private bins. For example, with two transmit antennas and one private bin per antenna, the virtual array size becomes (2N_{r}) (twice the physical receive‑array size). This virtual array provides additional spatial degrees of freedom that, when combined with coarse estimates of angle, range, and velocity obtained by the low‑complexity method of the authors’ prior work, yields high‑resolution target parameter estimation.

Mathematically, the received signal on a private TF bin ((u_{p},v_{p})) at receive antenna (n) is expressed as

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