A novel OFDM-MIMO radar with non-equidistant subcarrier interleaving and compressed sensing

Abstract

A novel concept of orthogonal frequency division multiplexing (OFDM) multiple input multiple output (MIMO) radar for automotive applications is presented in this paper. Multiple transmit antennas are multiplexed via OFDM subcarrier interleaving. Such a multiplexing enables a simultaneous operation of transmit antennas, while the complete bandwidth is utilized by each of them. Whereas the known OFDM-MIMO radar concepts perform multiplexing via equidistant subcarrier interleaving, we propose the use of non-equidistant subcarrier interleaving for multiplexing of transmit antennas. The advantage of this approach over the equidistant interleaving is the full unambiguously measurable distance range, not reduced through the subcarrier interleaving. To cope with the increased sidelobes in distance estimation due to the non-equidistant subcarrier interleaving, we propose a novel two-dimensional distancevelocity estimation algorithm based on compressed sensing that incorporates the radar images from all antennas. The proposed algorithm is able to detect weak targets, originally masked by the sidelobes of more dominant ones.

Random Multiplexing for an MIMO-OFDM Radar With Compressed Sensing-Based Reconstruction

“…It further allows exploiting the information of all channels within one CS instance and thereby improving the reconstruction, speeding up the processing, and reducing the computational complexity. In context of OFDM radar, CS has recently been proposed in various fields such as interference mitigation [5], bandwidth reduction [6], and MIMO [3]. Additionally, since both [3] and [4] lack a treatment of the directions of arrival (DoA), we verify that the DoA information is preserved.…”

“…In (d), the proposed random MIMO approach is shown. Compared to (c) [4], more flexibility in the waveform design of the signals is facilitated since the only requirement is a quasi random pattern, individual elements may even be unused. Compared to (a) and (b) which are pure FDM transmission patterns, random MIMO is a combination of FDM and TDM.…”

“…In contrast to conventional FMCW radars, OFDM offers the possibility of both TDM and FDM. In literature, there are only a few different MIMO-OFDM radar approaches, mostly FDM, including regular or equidistant interleaving [2], irregular or non-equidistant interleaving [3], and dynamic interleaving [4] (cf. Fig.…”

“…Though, this improvement comes at the expense of a distinct artifact ridge along the range cells of each target. In [3], it is proposed to apply compressed sensing (CS) to mitigate this effect, however, due to the constant allocation of subcarriers over time, channel information of only a single transmitter is available per subcarrier which is detrimental in CS signal reconstruction. In dynamic interleaving, the subcarriers are dynamically assigned to the transmitters over time.…”

Radar Waveform Optimization for Joint Radar Communications Performance

“…Waveform design has become a dominant research thread in joint radar communications phenomenology. Several waveform options are being studied including orthogonal frequency-division multiplexing (OFDM) [13][14][15][16][17][18][19][20][21] and spread spectrum waveforms [22][23][24][25] which have been considered due to their attractive, noise-like autocorrelation properties. Researchers have also looked at optimization theory based radar waveform design methods in spectrally dense environments that attempt to maximize some radar performance metrics (detection probability, ambiguity function features etc.)…”