Co-Designing Statistical MIMO Radar and In-band Full-Duplex Multi-User MIMO Communications -- Part I: Signal Processing

TL;DR

The resulting non-convex problem is solved by incorporating block coordinate descent (BCD) and alternating projection (AP) methods in a single algorithmic framework called BCD-AP MRMC by exploiting the relationship between mutual information and weighted minimum mean-squared-error (WMMSE), which allows use of the Lagrange dual problem in finding closed-form solutions for precoders and radar waveform.

Abstract

We consider a spectral sharing problem in which a statistical (or widely distributed) multiple-input multiple-output (MIMO) radar and an in-band full-duplex (IBFD) multi-user MIMO (MU-MIMO) communications system concurrently operate within the same frequency band. Prior works on joint MIMO-radar-MIMO-communications (MRMC) systems largely focus on either colocated MIMO radars, half-duplex MIMO communications, single-user scenarios, omit practical constraints (clutter, uplink [UL]/downlink [DL] transmit powers, UL/DL quality-of-service, and peak-to-average-power ratio), or MRMC co-existence that employs separate transmit/receive units. The purpose of this and companion papers (Part II and III) is to co-design an MRMC framework that addresses all of these issues. In this paper, we propose signal processing for a distributed IBFD MRMC, where radar receiver is designed to additionally exploit the downlink communications signals reflected from a radar target. Extensive numerical experiments show that our methods improve radar target detection over conventional codes and yield a higher achievable data rate than standard precoders. The following companion paper (Part II) describes the theory and procedure of our algorithm to solve the non-convex design problem. The final companion paper (Part II) considers the case of multiple targets and examines the tracking performance of our MRMC system.

Figures (5)

• Figure 1: Co-design system model comprising a statistical (widely distributed) MIMO radar and IBFD MU-MIMO communications.
• Figure 2: Transmission sequence during the observation interval $t\in{\left [{0,KT_{\mathrm{r}}+GT_\mathrm{p}}\right ]}$. Each bin represents a discrete-time radar/communications transmit signal of duration $T_{\mathrm{p}}$. The communications data transmissions occur continuously while pulsed radar Txs emit probing signals at the rate $1/T_\mathrm{r}$.
• Figure 3: The overlaid receive signal timing diagram during ${k}{\text{-th}}$ radar PRI and ${k}{\text{-th}}$ communications frame in the observation window; noise trails have been excluded. The purple bin with more opacity indicates the DL signal reflected from the target and observed in the radar CUT, i.e., $\mathbf{y}^{\left({n_\mathrm{t}}\right)}_{\textrm{Bt},n_\mathrm{r}}{\left [{k}\right ]}$. Other more translucent purple bins indicate $\mathbf{y}^{\left({n^\prime_\mathrm{t}}\right)}_{\textrm{Bt},n_\mathrm{r}}{\left [{k}\right ]}$ for $n^\prime_\mathrm{t}\neq n_\mathrm{t}$ (see \ref{['eq:Bt_range_cell']}).
• Figure 4: Target detection performance of the co-designed system compared with other radar codes and cooperation schemes using the NP detector. (a) $P_{\textrm{d}}$ versus $\nu$ (b) ROC of the NP detector.
• Figure 5: Performance of the IBFD MU-MIMO communications system compared with varying numbers of (a) UL and (b) DL UEs.