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This paper studies the coexistence between a downlink multiuser massive multi-input-multi-output (MIMO) communication system and MIMO radar. The performance of the massive MIMO system with maximum ratio (MR), zero-forcing (ZF), an...
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This paper studies the coexistence between a downlink multiuser massive multi-input-multi-output (MIMO) communication system and MIMO radar. The performance of the massive MIMO system with maximum ratio (MR), zero-forcing (ZF), and protective ZF (PZF) precoding designs is characterized in terms of spectral efficiency (SE) and by taking the channel estimation errors and power control into account. The idea of PZF precoding relies on the projection of the information-bearing signal onto the null space of the radar channel to protect the radar against communication signals. We further derive closed-form expressions for the detection probability of the radar system for the considered precoding designs. By leveraging the closed-form expressions for the SE and detection probability, we formulate a power control problem at the radar and base station (BS) to maximize the detection probability while satisfying the per-user SE requirements. This optimization problem can be efficiently tackled via the bisection method by solving a linear feasibility problem. Our analysis and simulations show that the PZF design has the highest detection probability performance among all designs, with intermediate SE performance compared to the other two designs. Moreover, by optimally selecting the power control coefficients at the BS and radar, the detection probability improves significantly.
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Soon after its introduction in the communications domain, the novel concept of multiple input–multiple output (MIMO) has been making its way also into the radar world. A new generation of multistatic netted systems with unprecede...
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Soon after its introduction in the communications domain, the novel concept of multiple input–multiple output (MIMO) has been making its way also into the radar world. A new generation of multistatic netted systems with unprecedented capabilities has been fully theorised, unveiling its potential advantages over its classical stand-alone, monostatic counterparts. However, MIMO radars mainly remained the object of abstract modeling, since electronic technology could hardly support the practical implementation of this new class of systems. With the development of microwave photonics, the realization of MIMO radar networks at the best of their capabilities has become a reality, thanks to the inherent coherence of photonics systems, and to the broad-band, low-distortion, and interference-immune optical signal distribution. This paper presents the results of a microwave photonics widely-distributed, dual-band MIMO radar network, deployed in a real freight port for maritime traffic monitoring, with inverse synthetic aperture radar imaging capabilities. It employs a central unit connected to multiple widely distributed remote radar peripherals thanks to optical fiber. The possibility to operate in dual-band mode, and the coherent management of the transmitted and received signals are demonstrated, exploiting geometric and frequency diversity in target detection. The system exhibits a spurious-free dynamic range of $\boldsymbol{\sim 82}\,{\mathbf{d}\mathbf{B}\cdot \mathbf{\mathbf{Hz}}^{\mathbf{2/3}}}$ and a sensitivity of $\mathbf{-110}\,\mathbf{dBm}$ . Under these premises, a small boat of $\mathbf \sim\! 1\,{\mathrm{\mathrm{m}}^{\mathrm{2}}}$ radar cross section has been detected at more than $\mathbf {800}\,{\mathbf{m}}$ , achieving a probability of detection of about $\mathbf {0.85}$ , for a false alarm rate of $\mathbf {7.7\times 10^{-4}}$ .
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In the present article, a reinforcement learning (RL)-based adaptive algorithm to optimize the transmit beampattern for a colocated massive multiple-input multiple-output (MIMO) radar is presented. Under the massive MIMO regime,...
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In the present article, a reinforcement learning (RL)-based adaptive algorithm to optimize the transmit beampattern for a colocated massive multiple-input multiple-output (MIMO) radar is presented. Under the massive MIMO regime, a robust Wald-type detector, able to guarantee certain detection performances under a wide range of practical disturbance models, has been recently proposed. Furthermore, an RL/cognitive methodology has been exploited to improve the detection performance by learning and interacting with the surrounding unknown environment. Building upon previous findings, we develop here a fully adaptive and data-driven scheme for the selection of the hyperparameters involved in the RL algorithm. Such an adaptive selection makes the Wald-RL-based detector independent of any ad hoc , and potentially suboptimal, manual tuning of the hyperparameters. Simulation results show the effectiveness of the proposed scheme in harsh scenarios with strong clutter and low SNR values.
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Sidelobes of radar waveforms can cause many undesirable consequences. Inspirited by achievements in multiple-input-multiple-output radar, the authors study how to use and design a set of nearly orthogonal waveforms for monostatic ...
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Sidelobes of radar waveforms can cause many undesirable consequences. Inspirited by achievements in multiple-input-multiple-output radar, the authors study how to use and design a set of nearly orthogonal waveforms for monostatic radar with coherent accumulation operation to transmit at successive pulse repetition intervals (PRIs). As the range sidelobes at different PRIs cannot be coherently accumulated anymore during the coherent accumulation, the overall sidelobe level after coherent accumulation can be decreased significantly, which is verified by numerical results.
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Two novel schemes are proposed to synthesize high-resolution range profile (HRRP) based on co-located multiple-input multiple-output (MIMO) system in the context of the joint radar and communication system. The difference between ...
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Two novel schemes are proposed to synthesize high-resolution range profile (HRRP) based on co-located multiple-input multiple-output (MIMO) system in the context of the joint radar and communication system. The difference between two schemes is the pattern of selecting pulses, which depends on the demand for the velocity information. The system, a type of frequency diverse array (FDA), takes full advantage of the phase-coded orthogonal frequency division multiplexing (OFDM) signal. Furthermore, the complete discrete form of the phase-coded OFDM echoes is utilized to derive the HRRP processing. The velocity estimation in the second scheme aims to eliminate velocity ambiguity, and high velocity can be retrieved exactly. Meanwhile, the imaging method is investigated with random frequency coding applied to an array. The desired performance of resolving velocity ambiguity and suppressing noise is shown by means of comparisons with previous work. The advantages in the radar imaging and the significance of the work are concluded in the end.
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The need for integrated sensing and communication (ISAC) services has significantly increased in the last few years. This integration imposes serious challenges such as joint system design, resource allocation, optimization, and a...
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The need for integrated sensing and communication (ISAC) services has significantly increased in the last few years. This integration imposes serious challenges such as joint system design, resource allocation, optimization, and analysis. Since sensing and telecommunication systems have different approaches for performance evaluation, introducing a unified performance measure which provides a perception about the quality of sensing and telecommunication is very beneficial. To this end, this paper provides performance analysis for ISAC systems based on the information theoretical framework of the Kullback-Leibler divergence (KLD). The considered system model consists of a multiple-input-multiple-output (MIMO) base-station (BS) providing ISAC services to multiple communication user equipments (CUEs) and targets (or sensing-served users). The KLD framework allows for a unified evaluation of the error rate performance of CUEs, and the detection performance of the targets. The relation between the detection capability for the targets and error rate of CUEs on one hand, and the proposed KLD on the other hand is illustrated analytically. Theoretical results corroborated by simulations show that the derived KLD is very accurate and can perfectly characterize both subsystems, namely the communication and radar subsystems.
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Frequency diverse array (FDA), which employs a small frequency increment across its array elements to generate controllable degrees-of-freedom (DOFs) in range dimension, has attracted extensive attentions in recent years. In order...
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Frequency diverse array (FDA), which employs a small frequency increment across its array elements to generate controllable degrees-of-freedom (DOFs) in range dimension, has attracted extensive attentions in recent years. In order to extract and exploit the DOFs in range and angle dimensions, FDA has been combined with multiple-input multiple-output (MIMO) technique, which shows sufficient performance improvement in clutter suppression in scenarios with range ambiguities. Therefore, clutter rank evaluation is an important issue for FDA-MIMO radar mounted on a moving platform. In this article, a clutter rank evaluation criterion is developed with respect to different transmit/receive array configurations and different number of range ambiguities. It is based on a subspace transformation matrix that decouples the clutter subspace and allows a direct determination of clutter rank. With the proposed clutter rank evaluation criterion, the maximum resolvable number of range ambiguities can be determined, which is bounded by the system’s DOFs. Three cases according to different relationships between uniform array element spacings are studied. Then, the aforementioned clutter rank evaluation method is extended to nonuniform array configurations. Moreover, the robustness of the method is studied in the presence of gain-phase errors. Several simulation results are provided to verify the effectiveness of the proposed method.
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A novel 4-D gesture sensing technique using reconfigurable virtual array method with a 60-GHz frequency-modulated continuous wave (FMCW) radar is presented. The 4-D sensing includes the 3-D spatial positioning and the 1-D motion t...
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A novel 4-D gesture sensing technique using reconfigurable virtual array method with a 60-GHz frequency-modulated continuous wave (FMCW) radar is presented. The 4-D sensing includes the 3-D spatial positioning and the 1-D motion tracking, which combines detection in both spatial and temporal domains. The proposed technique can be used for gesture sensing for both macro gestures such as handwriting letters and numbers, hand drawing different patterns in space and micro gestures such as the fingers’ actions of virtual slider, finger tap, and finger wave. Moreover, this work presents a method to reconfigure the working modes of different transmitting and receiving channels in the multiple input and multiple output (MIMO) architecture, which effectively increases the sensing range of the radar sensor and the signal-to-noise ratio (SNR) of the beat signal. For various gestures at different distances or in different environments, the proposed technique can adaptively achieve the best detection by reconstructing the virtual array of the MIMO radar. A series of experiments are carried out in both microwave anechoic chamber and office environments to validate the proposed technique. The experimental results show that the proposed technique performs well in sensing a variety of both macro gestures andmillimeter-level micro gestures. Compared with the conventional MIMO method, the proposed technique increases the sensing range by 3.5 times, and the SNR is also greatly improved by 12 dB when the radar performs gesture sensing at the distance of 0.65 m.
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Frequency spectrum sharing between radar and communication systems has recently attracted substantial attention. We consider the coexistence between a massive multiple-input multiple-output (MIMO) downlink system and MIMO radar to...
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Frequency spectrum sharing between radar and communication systems has recently attracted substantial attention. We consider the coexistence between a massive multiple-input multiple-output (MIMO) downlink system and MIMO radar to enable the operation of these two systems with minimal mutual interference. Through an asymptotic analysis, we show that by using more antennas at the base station (BS), we can improve the performance of massive MIMO, while keeping the interference to the radar system unchanged. Additionally, if we use a large number of antennas at the BS and make the transmit power inversely proportional to the number of antennas, we can avoid the interference from the massive MIMO system to the radar system, with no compromise in the performance of the massive MIMO system. Closed-form expressions for the probability of detection of the radar system and the downlink spectral efficiency of the massive MIMO system, are derived. Furthermore, we propose a power allocation scheme which selects the transmit powers at the MIMO radar and BS to maximize the probability of detection for the MIMO radar. Interestingly, the optimal power allocation can be determined in closed-form. These results provide valuable insights into the practical coexistence between massive MIMO and radar systems.
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Multiple-input multiple-output (MIMO) radar is a novel radar system which can achieve more individual observation echoes than the number of the actual antennas by transmitting orthogonal waveforms. At present, pattern theory is us...
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Multiple-input multiple-output (MIMO) radar is a novel radar system which can achieve more individual observation echoes than the number of the actual antennas by transmitting orthogonal waveforms. At present, pattern theory is usually utilised to evaluate the azimuth imaging indicator of the MIMO imaging radar system. Although it cannot describe the two-dimensional performance, it is quite effective to analyse the azimuth resolution of far-field targets. However, the pattern based on the far-field condition becomes invalid for targets in the near-field area, thus it cannot explain the appearance of near-field azimuth grating lobes. In this article, spatial spectrums and generalised ambiguity functions (GAFs) of near-field targets are calculated. By describing the near-field GAF (NGAF) approximately, the relationship between the distortions of NGAF and the spatial spectrum is studied qualitatively, which can explain the appearance of azimuth near-field grating lobes. In addition, the calibration method of amplitude and phase errors by an isolated corner reflector is presented in this article. Finally, a simulation and an experiment are carried out to verify the conclusions.
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