J. Andrew Zhang

J. Andrew Zhang
University of Technology Sydney | UTS · School of Electrical and Data Engineering

Doctor of Philosophy

About

398
Publications
53,975
Reads
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7,767
Citations
Introduction
J. Andrew Zhang is an associate professor in University of Technology Sydney, Sydney, Australia. He has a wide research interest in signal processing for wireless communications and sensing. Prof. Zhang has published more than 200 papers in leading international journals and conference proceedings and hold 5 patents. He has won 5 best paper awards for his work, including the best paper award in ICC 2013.
Additional affiliations
July 2016 - present
University of Technology Sydney
Position
  • Professor
April 2004 - December 2009
National ICT Australia Ltd
Position
  • Researcher
January 2010 - June 2016
The Commonwealth Scientific and Industrial Research Organisation
Position
  • Senior Researcher
Education
March 2001 - March 2004
Australian National University
Field of study
  • Wireless Communications

Publications

Publications (398)
Article
Full-text available
Beamforming has great potential for joint communication and sensing (JCAS), which is becoming a demanding feature on many emerging platforms such as unmanned aerial vehicles and smart cars. Although beamforming has been extensively studied for communication and radar sensing respectively, its application in the joint system is not straightforward d...
Article
Full-text available
In this paper, we develop a framework for a novel perceptive mobile/cellular network that integrates radar sensing function into the mobile communication network. We propose a unified system platform that enables downlink and uplink sensing, sharing the same transmitted signals with communications. We aim to tackle the fundamental sensing parameter...
Article
Full-text available
Perceptive mobile network (PMN) is a recently proposed next-generation network that integrates radar sensing into communications. One major challenge for realizing sensing in PMNs is how to deal with spatially-separated asynchronous transceivers. The asynchrony between sensing receiver and transmitter will cause both timing offsets (TOs) and carrie...
Article
Full-text available
Mobile network is evolving from a communication-only network towards one with joint communication and radar/radio sensing (JCAS) capabilities, that we call perceptive mobile network (PMN). Radio sensing here refers to information retrieval from received mobile signals for objects of interest in the environment surrounding the radio transceivers, an...
Article
Full-text available
Joint communication and radar sensing (JCR) represents an emerging research field aiming to integrate the above two functionalities into a single system, by sharing the majority of hardware, signal processing modules and, in a typical case, the transmitted signal. The close cooperation of the communication and sensing functions can enable significa...
Article
Full-text available
This work investigates the impact of rainfall on cellular communication links, leveraging smartphone-collected measurements. While existing studies primarily focus on line-of-sight (LoS) microwave propagation environments, this work explores the impact of rainfall on typical signal metrics over cellular links when the LoS path is not guaranteed. We...
Article
Current research on faster-than-Nyquist (FTN) systems mainly focuses on baseband digital signal processing without considering the impact of I/Q imbalance (IQI) caused by hardware impairments in the signal chain. To address this problem, this paper considers frequency-dependent IQI and applies the frame-based decision-directed successive interferen...
Article
Integrated sensing and communications (ISAC) is a promising technique for next-generation mobile networks, offering reduced device size, power consumption, cost, and improved spectrum efficiency. Full realization of such benefits relies on waveform design and resource allocation. This paper focuses on frequency-time (FT) resource allocation of mult...
Article
Sensing in Integrated Sensing and Communications (ISAC) systems with clock asynchronism between the transmitter and receiver poses significant challenges. Understanding the fundamental limits of sensing performance in such setups, which remain largely unknown, is crucial. This paper investigates the sensing performance bounds in the presence of clo...
Article
Wideband millimeter wave and terahertz systems face severe nonlinearity and other practical impairments such as transmitter and receiver in-phase/quadrature imbalances (IQIs), carrier frequency offset, and phase noise. Based on a simplified yet effective received signal model including an expanded memory polynomial (EMP) and a noisy receiver filter...
Article
Bi-static sensing is crucial for exploring the potential of networked sensing capabilities in integrated sensing and communications (ISAC). However, it suffers from the challenging clock asynchronism issue. Channel state information (CSI) ratio-based sensing is an effective means to address the issue. Its performance bounds, particular for Doppler...
Article
For wideband transceivers operating at millimeter wave and terahertz frequencies, the implementation of conventional digital predistortion for nonlinearity mitigation faces significant challenges due to the limited availability and/or complexity of high-speed digital signal processing. In this paper, a simple received signal model is proposed for w...
Article
Millimeter-wave Integrated Sensing and Communications (ISAC) with multi-beam design holds significant promise for vehicular networks, offering multi-target omnidirectional sensing and high-capacity communication services concurrently. Nonetheless, the considerable challenge of potential mutual interference arises due to the high mobility and densit...
Article
Full-text available
Integrated sensing and communication (ISAC) is regarded as a promising technique for sixth-generation (6G) communication network. In this letter, we investigate the Pareto bound of the ISAC system in terms of a unified Kullback-Leibler divergence (KLD) performance measure. We firstly use KLD to analyze the detection performance of communication and...
Article
Full-text available
In this paper, we investigate the realization of covert communication in a general radar-communication cooperation system, which includes integrated sensing and communications as a special example. We explore the possibility of utilizing the sensing ability of radar to track and jam the aerial adversary target attempting to detect the transmission....
Article
In this work, we propose an integrated MIMO system which performs target tracking and downlink communications, as well as receiving uplink signals from other communication nodes to achieve bi-directional communications. The key to such a system is the constrained joint transmit waveform design, which constitutes the main contribution of this work....
Article
Integrated Sensing And Communication (ISAC) has been identified as a pillar usage scenario for the impending 6G era. Bi-static sensing, a major type of sensing in ISAC, is promising to expedite ISAC in the near future, as it requires minimal changes to the existing network infrastructure. However, a critical challenge for bi-static sensing is clock...
Preprint
Full-text available
When applying integrated sensing and communications (ISAC) in future mobile networks, many sensing tasks have low latency requirements, preferably being implemented at terminals. However, terminals often have limited computing capabilities and energy supply. In this paper, we investigate the effectiveness of leveraging the advanced computing capabi...
Article
Downlink (DL) and uplink (UL) joint communication and sensing (JCAS) technologies have been individually studied for realizing sensing using DL and UL communication signals, respectively. Since the spatial environment and JCAS channels in the consecutive DL and UL JCAS time slots are generally unchanged, DL and UL JCAS can be jointly designed to ac...
Preprint
Full-text available
Wireless communications are significantly impacted by the propagation environment, particularly in doubly selective channels with variations in both time and frequency domains. Orthogonal Time Frequency Space (OTFS) modulation has emerged as a promising solution; however, its high equalization complexity, if performed in the delay-Doppler domain, l...
Preprint
Full-text available
In this work, we investigate sensing parameter estimation in the presence of clutter in perceptive mobile networks (PMNs) that integrate radar sensing into mobile communications. Performing clutter suppression before sensing parameter estimation is generally desirable as the number of sensing parameters can be signiffcantly reduced. However, existi...
Article
In this paper, we propose a novel complex convolutional neural network (CNN) CSI enhancer for integrated sensing and communications (ISAC), which exploits the correlation between the sensing parameters (such as angle-of-arrival and range) and the channel state information (CSI) to significantly improve the CSI estimation accuracy and further enhanc...
Preprint
Full-text available
Waveform design has served as a cornerstone for each generation of mobile communication systems. The future sixth-generation (6G) mobile communication networks are expected to employ larger-scale antenna arrays and exploit higher-frequency bands for further boosting data transmission rate and providing ubiquitous wireless sensing. This brings new o...
Article
In this work, we study sensing-aided uplink transmission in an integrated sensing and communication (ISAC) vehicular network with the use of orthogonal time frequency space (OTFS) modulation. To exploit sensing parameters for improving uplink communications, the parameters must be first associated with the transmitters, which is a challenging task....
Preprint
Full-text available
Integrated sensing and communication (ISAC) is regarded as a promising technique for 6G communication network. In this letter, we investigate the Pareto bound of the ISAC system in terms of a unified Kullback-Leibler (KL) divergence performance metric. We firstly present the relationship between KL divergence and explicit ISAC performance metric, i...
Article
Full-text available
In the sixth generation (6G) era, intelligent machine network (IMN) applications, such as intelligent transportation, require collaborative machines with communication, sensing, and computation (CSC) capabilities. This article proposes an integrated communication, sensing, and computation (ICSAC) framework for 6G to achieve the reciprocity among CS...
Article
Intelligent reflective surface (IRS) assisted integrated sensing and communications (ISAC) is a promising technology for future mobile communications. However, high channel correlation, which may significantly degrade the performance of ISAC, has been overlooked. This letter addresses the issue by introducing user grouping to IRS-assisted ISAC. We...
Article
This paper proposes an orthogonal expanded memory polynomial (OEMP) model for circular complex Gaussian processes. The basis functions of the OEMP model are constructed from those of the expanded memory polynomial (EMP) model recently derived by expanding the conventional memory polynomial (MP) model for I/Q imbalanced signals, and proved orthogona...
Article
With integrated sensing and communications (ISAC) and reconfigurable intelligent surface (RIS) emerging as critical enablers for future mobile communications, their combination has attracted increasing attention lately. To effectively utilize RIS for improving ISAC, we propose two novel designs targeting different scenarios. The first design strike...
Article
Uplink sensing in integrated sensing and communications (ISAC) systems, such as Perceptive Mobile Networks, is challenging due to the clock asynchronism between transmitter and receiver. Existing solutions typically require the presence of a line-of-sight path and the knowledge of the transmitter’s location. In this paper, these requirements, we pr...
Article
Integrated sensing and communication (ISAC) technology empowers WiFi to function as both sensors for wireless sensing and communication devices for data exchange. Currently, achieving accurate object tracking with commercial WiFi devices is still challenging due to the limited bandwidth, a small number of antennas, and the clock asynchronization in...
Article
Waveform design has served as a cornerstone for each generation of mobile communication systems. The future sixth-generation (6G) mobile communication networks are expected to employ larger-scale antenna arrays and exploit higher-frequency bands for further boosting data transmission rate and providing ubiquitous wireless sensing. This brings new o...
Article
When applying integrated sensing and communications (ISAC) in future mobile networks, many sensing tasks have low latency requirements, preferably being implemented at terminals. However, terminals often have limited computing capabilities and energy supply. In this paper, we investigate the effectiveness of leveraging the advanced computing capabi...
Preprint
Full-text available
p>For wideband transceivers operating at millimeter wave and terahertz frequencies, the implementation of conventional digital predistortion for nonlinearity mitigation faces significant challenges due to the limited availability and/or complexity of high-speed digital signal processing. In this paper, a simple received signal model is proposed for...
Preprint
Full-text available
p>Wideband millimeter wave and terahertz systems face severe nonlinearity and other practical impairments such as transmitter and receiver I/Q imbalances ( IQIs ), carrier frequency offset, and phase noise. Based on a simplified yet effective received signal model, this paper proposes a low-complexity digital post-cancellation ( DPC ) framework for...
Article
Network Function Virtualization (NFV), which decouples network functions from hardware and transforms them into Virtual Network Functions (VNFs), is a crucial technology for data center (DC) networks. A service function chain (SFC) is composed of an ordered set of VNFs and virtual links (VLs) connecting them. To optimize the resource allocation in...
Article
Joint communication and sensing (JCS) has become a promising technology for mobile networks because of its higher spectrum and energy efficiency. Up to now, the prevalent fast Fourier transform (FFT)-based sensing method for mobile JCS networks is on-grid based, and the grid interval determines the resolution. Because the mobile network usually has...
Article
Analog beamforming with broadband large-scale antenna arrays in millimeter wave (mmWave) multiple input multiple output (MIMO) systems faces the beam squint problem. In this paper, we first investigate the sensitivity of analog beamforming to subarray spatial separations in widebandmmWave systems using hybrid arrays, and propose optimized subarray...
Article
Faster-than-Nyquist (FTN) signaling can improve spectral efficiency and enable high-speed transmission for next-generation communication systems. One of the most significant challenges in FTN transmission is how to remove the inter-symbol interference (ISI). In this paper, we propose a novel decision-directed successive interference cancellation (D...
Preprint
Full-text available
In this paper, we investigate the realization of covert communication in a general radar-communication cooperation system, which includes integrated sensing and communications as a special example. We explore the possibility of utilizing the sensing ability of radar to track and jam the aerial adversary target attempting to detect the transmission....
Chapter
In this chapter, we will provide an introduction on how to realize integrated sensing and communication in mobile networks. We will first introduce a framework including the network structure and required modifications for integrating sensing into the current communication-only mobile networks. Based on the framework, we will then discuss detailed...
Article
Joint communications and sensing (JCAS) is potentially a hallmark technology for the sixth generation mobile network (6G). Most existing JCAS designs are based on digital arrays, analog arrays with tunable phase shifters, or hybrid arrays, which are effective but are generally complicated to design and power inefficient. This article introduces the...
Article
Full-text available
In this paper, we propose a secure multi-user uplink communicaion scheme against a mobile aerial eavesdropper (AE) in Integrated Sensing and Communication (ISAC) systems, where the ISAC base station transmits radar signals to track and jam the AE. For tracking mobile AE, we adopt an extended Kalman filter technique to predict AE's motion state. Bas...
Article
Full-duplex (FD) integrated sensing and communication (ISAC) has great potential in future vehicular networks. However, the FD requirement and the ISAC functions make the receiver processing extremely complicated, particularly when multiple transmissions are uncoordinated. In this paper, we study frequency-hopping (FH) based receivers in an FD ISAC...
Preprint
Full-text available
p>Digital predistortion (DPD) has been widely used in microwave transmitters to remove the signal distortion and spectral re-growth caused by nonlinear high power amplifiers and I/Q imbalanced up-converters. However, a DPD can hardly be implemented at a wideband transmitter operating at millimeter wave or terahertz frequency. In this paper, a low-c...
Preprint
Full-text available
p>Digital predistortion (DPD) has been widely used in microwave transmitters to remove the signal distortion and spectral re-growth caused by nonlinear high power amplifiers and I/Q imbalanced up-converters. However, a DPD can hardly be implemented at a wideband transmitter operating at millimeter wave or terahertz frequency. In this paper, a low-c...
Article
Beam alignment is a process for receive and transmit antenna arrays to find the correct beamforming directions. It is typically based on beam scanning and peak-energy searching, which lead to time-consuming beam training process in communication protocols, such as 802.11ad for vehicular networks. In this correspondence, we propose a fast beam align...
Article
Joint communication and sensing (JCAS) is a promising technology for 6th Generation (6G) mobile networks, such as intelligent vehicular networks, intelligent manufacturing, and so on. Equipped with two spatially separated antenna arrays, the base station (BS) can perform downlink active JCAS in a mono-static setup. This paper proposes a Concurrent...
Preprint
Full-text available
In this paper, we propose a novel integrated sensing and communication (ISAC) complex convolution neural network (CNN) CSI enhancer for 6G networks, which exploits the correlation between the sensing parameters, such as angle-of-arrival (AoA) and range, and the channel state information (CSI) to significantly improve the CSI estimation accuracy and...
Preprint
Full-text available
In this work, we study sensing-aided uplink transmission in an integrated sensing and communication (ISAC) vehicular network with the use of orthogonal time frequency space (OTFS) modulation. To exploit sensing parameters for improving uplink communications, the parameters must be first associated with the transmitters, which is a challenging task....
Article
Full-text available
The air-ground integrated sensing and communications (AG-ISAC) network, which consists of unmanned aerial vehicles (UAVs) and ground terrestrial networks, offers unique capabilities and demands special design techniques. In this article, we provide a review on AG-ISAC, by introducing UAVs as "relay" nodes for both communications and sensing to reso...
Article
This letter proposes a virtual-array-based waveform optimization scheme for broadband joint radar-communication systems. We first formulate a problem of minimizing Cramér-Rao bound (CRB) of radar subject to communication constraints. To reduce the high complexity of directly solving the problem, we allocate the virtual arrays to users according to...
Preprint
Full-text available
Contact-free vital sign monitoring, which uses wireless signals for recognizing human vital signs (i.e, breath and heartbeat), is an attractive solution to health and security. However, the subject's body movement and the change in actual environments can result in inaccurate frequency estimation of heartbeat and respiratory. In this paper, we prop...
Article
The spectrally efficient multicarrier faster-than-Nyquist (MFTN) signaling provides an efficient and robust solution for enhancing transmission rate and resisting channel impairments. In this paper, an evolutionary non-orthogonal physical waveform is proposed for simultaneously achieving high spectral and energy efficiency via combining MFTN signal...
Preprint
Full-text available
Integrated sensing and communications (ISAC) is emerging as a critical technique for next-generation communication systems. Reconfigurable intelligent surface (RIS) can simultaneously enhance the performance of communication and sensing by introducing new degrees-of-freedom for beamforming in ISAC systems. This paper proposes two optimization techn...
Article
Full-text available
Beamspace millimeter-wave (mmWave) and terahertz (THz) massive MIMO constitute attractive schemes for next-generation communications, given their abundant bandwidth and high throughput. However, their user and beam selection problem has not been efficiently addressed yet. Inspired by this challenge, we develop low-complexity solutions explicitly. I...
Preprint
Full-text available
The air-ground integrated sensing and communications (AG-ISAC) network, which consists of unmanned aerial vehicles (UAVs) and ground terrestrial networks, offers unique capabilities and demands special design techniques. In this article, we provide a review on AG-ISAC, by introducing UAVs as "relay" nodes for both communications and sensing to reso...
Article
6G networks have been envisioned as key enablers for numerous emerging applications, including smart cities and homes, intelligently connected vechiles, smart manufactoring, and industrial Internet-of-Things (IoT). These applications require both extreme wireless connectivity as well as highly accurate and reliable sensing capability. Indeed, among...
Preprint
Full-text available
Joint radar and communications (JRC) can realize two radio frequency (RF) functions using one set of resources, greatly saving hardware, energy and spectrum for wireless systems needing both functions. Frequency-hopping (FH) MIMO radar is a popular candidate for JRC, as the achieved communication symbol rate can greatly exceed radar pulse repetitio...
Article
Full-text available
The performance of millimeter wave (mmWave) line-of-sight multiple input multiple output (LOS MIMO) systems using hybrid arrays of planar subarrays was studied. We characterized the achievable maximum spatial multiplexing gain for such LOS MIMO systems by the measures of spectral efficiency and effective degree of freedom (EDoF). By proposing a joi...
Article
Full-text available
The boundaries of tracking and sensing solutions are continuously being pushed. A stimulation in this field over recent years is exploiting the properties of millimeter wave (mmWave) radar to achieve simultaneous tracking and sensing of multiple objects. This paper aims to provide a critical analysis of the current literature surrounding multi-obje...
Article
Contact-free vital sign monitoring, which uses wireless signals for recognizing human vital signs (i.e, breath and heartbeat), is an attractive solution to health and security. However, the subject's body movement and the change in actual environments can result in inaccurate frequency estimation of heartbeat and respiratory. In this paper, we prop...
Article
Uplink sensing in perceptive mobile networks (PMNs), which uses uplink communication signals for sensing the environment around a base station, faces challenging issues of clock asynchronism and the requirement of a line-of-sight (LOS) path between transmitters and receivers. The channel state information (CSI) ratio has been applied to resolve the...
Article
Doppler frequency estimation is a challenging problem in integrated sensing and communication systems with clock asynchronism between transmitter and sensing receiver. Existing techniques have various limitations and are generally ineffective in multi-target sensing. In this correspondence, we propose an array-based scheme for multiple-target Doppl...
Article
Existing channel estimation techniques for orthogonal time frequency space (OTFS) transmission are mostly based on the pilots embedded in the two-dimensional delay-Doppler domain, which significantly increases the signaling overhead. In this paper, three variants of OTFS transmission, i.e., frequency-domain pilot-aided (FD-PA) OTFS, time-domain pil...
Article
Integrated sensing and communication (ISAC) is regarded as the enabling technology in the future 5th-Generation-Advanced (5G-A) and 6th-Generation (6G) mobile communication system. ISAC waveform design is critical in ISAC system. However, the difference of the performance metrics between sensing and communication brings challenges for the ISAC wave...
Article
In this paper, we propose a novel Kalman Filter (KF)-based uplink (UL) joint communication and sensing (JCAS) scheme, which can significantly reduce the range and location estimation errors due to the clock asynchronism between the base station (BS) and user equipment (UE). Clock asynchronism causes time-varying time offset (TO) and carrier frequen...
Article
Perceptive mobile networks aim to provide integrated sensing without compromising communication performance. To achieve high ranging accuracy, optimizing the transmitted signal is a critical task. In this letter, we optimize 5G NR signal for uplink sensing to improve ranging accuracy. Aiming at minimizing the Cramér-Rao bound (CRB) for delay estima...
Article
Joint communications and sensing (JCAS) have the potential to improve the overall energy, cost and frequency efficiency of Internet-of-Things (IoT) systems. As a first effort, we propose to optimize the MIMO-OFDM data symbols carried by sub-carriers for better time-and spatial-domain signal orthogonality. This can reduce inter-target and inter-ante...