Teng Joon Lim

The University of Sydney · Electrical & Information Engineering

Digital pre-distortion (DPD) has recently been developed to compensate for in-phase and quadrature (IQ) imbalance and crosstalk, as well as power amplifier (PA) nonlinearity distortions in multi-input multi-output (MIMO) transmitters (TXs). Despite its limitations, most DPD models still use a simple non-iterative framework called the indirect learn...

Low-latency requirements of vehicular networks can be met by installing mobile edge hosts that implement mobile edge computing in the roadside units (RSUs). Adversaries can, however, compromise these RSUs and use them to launch cyber attacks. In this paper, we consider an adversary that selectively drops packets or selectively corrupts packets betw...

Ensemble approaches are promising for anomaly detection due to the heterogeneity of network traffic. However, existing ensemble approaches lack applicability and efficiency. We propose ODDITY, a new end-to-end data-driven ensemble framework. ODDITY use Diverse Autoencoders trained on a pre-clustered subset with contrastive representation learning t...

The use of unmanned aerial vehicles (UAVs) for diverse activities has increased rapidly in recent years. Nonetheless, if operational cyber security is not handled effectively , these technologies offer a significant hazard which can cause catastrophic harm. Therefore, it is important to identify the potential attacks that can be implemented by an a...

The use of unmanned aerial vehicles (UAVs) for diverse activities has increased rapidly in recent years. Nonetheless , if operational cyber security is not handled effectively, these technologies offer a significant hazard which can cause catastrophic harm. Therefore it is important to identify the potential attacks that can be implemented by an ad...

In this work, we present an IoT botnet detection solution, EDIMA, consisting of a set of lightweight modules designed to be deployed at the edge gateway installed in home networks with the remaining modules expected to be implemented on cloud servers. EDIMA targets early detection of IoT botnets prior to the launch of an attack and includes a novel...

There has been a strong interest in using deep neural networks (DNNs) for modeling the power amplifier (PA) non-linearity and designing the digital pre-distortion (DPD) circuit. Most DNNs only accept real-valued inputs since the baseband signal has in-phase and quadrature (I/Q) components. As a result, their entire structures can be highly complex....

In typical wireless heterogeneous networks (HetNets), users are clustered around known hotspots, e.g., shopping centres or schools, but such a non-uniform distribution of nodes is difficult to analyze. This paper explicitly models this scenario, with macro base stations (MBSs) modeled by a homogeneous Poisson point process (PPP), and millimeter-wav...

The Internet of Vehicles (IoV) may enhance road safety, improve traffic flow, etc. However, internet connected intelligent vehicles (IVs) are vulnerable to cyber-attacks. One of the important challenges in IoV is thus, verifying data integrity with strict latency requirements. The conventional way of providing data integrity in the Internet cannot...

This paper is concerned with the problem of distributed joint state and sensor fault estimation for autonomous ground vehicles subject to unknown-but-bounded (UBB) external disturbance and measurement noise. In order to improve the estimation reliability and performance in cases of poor data collection and potential communication interruption, a mu...

Given all of the extreme changes experienced over the last year, this issue of IEEE Potentials gives us an opportunity to look back at our engineering programs, assess the current state, and think of what the “Future of Engineering Education” entails. This issue contains five theme articles on engineering education that highlight different initiati...

Throughout history, the nature of professional engineering practice has constantly evolved, driven not only by evolution in technology and scientific knowledge but also by changes in the way in which our engineered solutions interact with society. As a consequence, there is a strong need for engineers to not only understand the changing nature of t...

In this paper, we present EDIMA, an IoT botnet detection solution to be deployed at the edge gateway installed in home networks which targets early detection of botnets. EDIMA includes a novel two-stage machine learning (ML)-based detector which first employs ML algorithms for aggregate traffic classification and subsequently Autocorrelation Functi...

A practical power amplifier (PA) has nonlinear characteristics that distort the output signal and hence increase the transmission error. Digital pre-distortion (DPD) has been widely accepted to compensate for the PA nonlinearity. However, in direct-conversion transmitters (DCTs), DPD performance is affected by in-phase and quadrature (IQ) imbalance...

In this work, we present a lightweight IoT botnet detection solution, EDIMA, which is designed to be deployed at the edge gateway installed in home networks and targets early detection of botnets prior to the launch of an attack. EDIMA includes a novel two-stage Machine Learning (ML)-based detector developed specifically for IoT bot detection at th...

Next generation wireless networks are under high risk of security attacks due to increased connectivity and information sharing among peer nodes. Some of the nodes could potentially be malicious, intending to disrupt or tamper sensitive data transfer in the network. In this paper, we present a detailed analysis of the sentinel based data integrity...

In network-coded wireless mesh networks, pollution attacks cause severe disruption to data transmission. Existing schemes to combat pollution attacks only focus on defensive performance but ignore their resource consumption. In this paper, we investigate the optimal trade-off between defensive performance and resource consumption through a game-the...

Byzantine attack is a severe security concern in network coding enabled wireless ad hoc networks, because the malicious nodes can easily inject bogus packets into the information flow and cause an epidemic propagation of pollution. In this paper, we address the Byzantine attack by proposing a malicious node identification scheme, which can achieve...

The widespread adoption of Internet of Things has led to many security issues. Recently, there have been malware attacks on IoT devices, the most prominent one being that of Mirai. IoT devices such as IP cameras, DVRs and routers were compromised by the Mirai malware and later large-scale DDoS attacks were propagated using those infected devices (b...

Increased device connectivity and information sharing in wireless IoT networks increases the risk of cyber attack by malicious nodes. In this paper, we present an effective and practical scheme for detecting data integrity and selective forwarding attacks launched by malicious relays in wireless IoT networks. The proposed scheme exploits the broadc...

We consider a multiple-access channel (MAC), where transmitters are powered by energy harvesting. They are equipped with batteries having non-ideal charging and discharging characteristics, resulting in a fractional loss of power driven into or drawn from them. Assuming that each user consumes constant power for circuit operation during transmissio...

The widespread adoption of Internet of Things has led to many security issues. Post the Mirai-based DDoS attack in 2016 which compromised IoT devices, a host of new malware using Mirai's leaked source code and targeting IoT devices have cropped up, e.g. Satori, Reaper, Amnesia, Masuta etc. These malware exploit software vulnerabilities to infect Io...

Many security issues have come to the fore with the increasingly widespread adoption of Internet-of-Things (IoT) devices. The Mirai attack on Dyn DNS service, in which vulnerable IoT devices such as IP cameras, DVRs and routers were infected and used to propagate large-scale DDoS attacks, is one of the more prominent recent examples. IoT botnets, c...

Clustering Internet of Things (IoT) Networks, to alleviate the network scalability problem, provides an opportunity for an adversary to compromise a set of nodes by simply compromising the relay they are associated with. In such scenarios, an adversary who has compromised the relay can affect the network’s performance by deliberately dropping the p...

Many security issues have come to the fore with the increasingly widespread adoption of Internet-of-Things (IoT) devices. The Mirai attack on Dyn DNS service, in which vulnerable IoT devices such as IP cameras, DVRs and routers were infected and used to propagate large-scale DDoS attacks, is one of the more prominent recent examples. IoT botnets, c...

The widespread adoption of Internet of Things has led to many security issues. Recently, there have been malware attacks on IoT devices, the most prominent one being that of Mirai. IoT devices such as IP cameras, DVRs and routers were compromised by the Mirai malware and later large-scale DDoS attacks were propagated using those infected devices (b...

Internet of Things (IoT) devices in clustered wireless networks can be compromised by compromising the gateway which they are associated with. In such scenarios, an adversary who has compromised the gateway can affect the network's performance by deliberately dropping the packets transmitted by the IoT devices. In this way, the adversary can actual...

For a radio resource limited multi-tier Machinetype Communication (MTC) network, controlling random access congestion while satisfying the unique requirements of each tier (type) and guaranteeing fairness among nodes is always a challenge. In this paper, we study the network dimensioning and radio resource partitioning for the uplink of an MTC netw...

To address the problem of multiple access for a large number of devices in machine-type communication (MTC), we study the use of full-duplex relays. In-band-full-duplex (IBFD) allows devices to receive and transmit concurrently on the same frequency band, potentially doubling the spectral efficiency. On the downside, the use of IBFD raises mutual i...

The scale of connected devices in the modern communication network and its heterogeneous nature have made securing the network more challenging. However, with the advent of Software Defined Networking (SDN), the algorithmic complexity is handled at a centralized control plane and the network elements perform only data forwarding based on control pl...

We consider a multiple-access channel where the users are powered from batteries having non-negligible internal resistance. When power is drawn from the battery, a variable fraction of the power, which is a function of the power drawn from the battery, is lost across the internal resistance. Hence, the power delivered to the load is less than the p...

In this paper, we propose a cost minimization strategy for facilities with shared access to a renewable energy farm. We assume space-time varying electricity prices, and model the facilities as non-deferrable, time-varying loads. A practical application of such an arrangement can be found in cellular networks, where operators can deploy a centraliz...

Facilities with limited flexibility to schedule their power consumption, such as office buildings or commercial establishments, can be modelled as time-varying non-deferrable loads. In this paper, we propose a demand response strategy for a non-deferrable load facility with renewable energy harvesting and storage capabilities. We assume time-varyin...

In this paper, we optimize an energy harvesting transmitter, communicating over a slow fading channel, using layered coding. The transmitter has access to the channel statistics, but does not know the exact channel state. In layered coding, the codewords are first designed for a given finite set of channel states at different rates, and then the co...

In this paper, we study a single-user multiple-input single-output (MISO) system with constant envelope (CE) transmission. To enable the nonlinear mapping from a fixed receiver signal constellation to the transmitter CE signal vectors, the availability of perfect channel state information at the transmitter (CSIT) is assumed in existing literature....

We propose two online demand response strategies to minimize the operational expenditure incurred by a nondeferrable load facility over a finite planning horizon. The facility is permanently connected to the grid, and is equipped with a rechargeable battery and a renewable energy (RE) harvester. The rechargeable battery can be operated in a linear...

Due to stringent constraints on resources, it may be infeasible to acquire the current channel state information at the transmitter in energy harvesting communication systems. In this paper, we optimize an energy harvesting transmitter, communicating over a slow fading channel, using layered coding. The transmitter has access to the channel statist...

Modern systems will increasingly rely on energy harvested from their environment. Such systems utilize batteries to smoothen out the random fluctuations in harvested energy. These fluctuations induce highly variable battery charge and discharge rates, which affect the efficiencies of practical batteries that typically have non-zero internal resista...

To accommodate massive access for machine-type communication (MTC) in cellular networks, we propose two single-hop relaying schemes exclusively designed for the MTC: signal-to-interference ratio based relaying and location based relaying. The relay nodes capture one or more MTC device (MTCD) transmissions and forward them to the base station (BS),...

In this letter, we study a multiple-input single-output (MISO) multicast system, where a multi-antenna transmitter sends a common message to multiple single-antenna users via constant envelope (CE) precoding. We aim to minimize the maximum symbol error rate over all users by jointly optimizing the CE precoding at the transmitter as well as the cons...

In terrestrial communication networks without fixed infrastructure, unmanned aerial vehicle (UAV)-mounted mobile base stations (MBSs) provide an efficient solution to achieve wireless connectivity. This letter aims to minimize the number of MBSs needed to provide wireless coverage for a group of distributed ground terminals (GTs), ensuring that eac...

Constant envelope (CE) precoding is an appealing transmission technique, which enables the realization of high power amplifier efficiency. For CE precoding in a single-user multiple-input single-output (MISO) channel, a desired constellation is feasible at the receiver if and only if it can be scaled to lie in an annulus, whose boundaries are chara...

Constant envelope (CE) precoding is an appealing transmission technique, which is realizable with a single radio frequency (RF) chain at the multi-antenna transmitter, while enabling highly efficient power amplification. In this paper, we study the transceiver design for a point-to-point multiple-input multiple-output (MIMO) system with CE precodin...

In this paper, we study the receive beamforming design to minimize the symbol error rate (SER) in a multiple-input multiple-output (MIMO) system with constant envelope (CE) precoding. In this case, a constellation is feasible at the combiner output of the receiver if and only if it can be scaled to lie in an annular region, whose boundaries are det...

Relaying is an effective technique to achieve reliable wireless connectivity in harsh communication environment. However, most of the existing relaying schemes are based on relays with fixed locations, or \emph{static relaying}. In this paper, we consider a novel \emph{mobile relaying} technique, where the relay nodes are assumed to be capable of m...

Wireless communication systems that include unmanned aerial vehicles (UAVs) promise to provide cost-effective wireless connectivity for devices without infrastructure coverage. Compared to terrestrial communications or those based on high-altitude platforms (HAPs), on-demand wireless systems with low-altitude UAVs are in general faster to deploy, m...

This paper studies a novel mobile relaying technique, where relays of high mobility are employed to assist the communications from source to destination. By exploiting the predictable channel variations introduced by relay mobility, we study the throughput maximization problem in a mobile relaying system via dynamic rate and power allocations at th...

Constant envelope (CE) precoding is an appealing transmission technique which enables the use of highly efficient nonlinear radio frequency (RF) power amplifiers (PAs). For CE precoding in a single-user multiple-input single-output (MISO) channel, a desired constellation is feasible at the receiver if and only if it can be scaled to lie in an annul...

This paper studies a multiple-input–single-output (MISO) broadcast channel (BC) featuring simultaneous wireless information and power transfer, where a multiantenna access point (AP) delivers both information and energy via radio signals to multiple single-antenna receivers simultaneously, and each receiver implements either information decoding (I...

In this paper, we minimize the total energy used in a two-tier heterogeneous cellular network (HCN), through the optimization of resource partitioning and user association, assuming that both macro and small-cell base stations may be put into sleep mode. With resource partitioning, one tier of base stations can be put into sleep mode on a fraction...

In this paper, we propose an energy cost minimization strategy for cellular base stations (CBSs) that are jointly powered by renewable and conventional energy. Energy tariffs follow time-of-use and consumption-based block pricing. In addition, consumers are allowed to return energy to the utility, e.g. following a net metering policy. Assuming that...

In ad hoc cognitive radio networks, nodes operate under critical power constraints which cause imperfections in carrier-sensing. Imperfect carrier-sensing often leads to false alarms and collisions. The focus of this paper is to study the theoretical performance of a cognitive radio network with imperfect carrier-sensing, when the nodes in the netw...

Cognitive Radio has emerged as a promising technology for the efficient utilization of the radio electromagnetic spectrum and to address the problem of spectrum shortage. Having a common control channel (CCC) over which control signals can be exchanged has several drawbacks including bandwidth inefficiency, susceptibility to denial of service (DoS)...

In machine-to-machine (M2M) communications, networking a large number of devices with bursty heterogeneous traffic is one of the most critical challenges. In the medium access control layer, the access class barring (ACB) mechanism may be used to regulate the transmission of packets by machine-type communications devices. In the current literature,...

Constant envelope (CE) precoding is an appealing transmission technique which enables the use of highly efficient nonlinear radio frequency (RF) power amplifiers (PAs). For CE precoding in a single-user multiple-input single-output (MISO) channel, a desired constellation is feasible at the receiver if and only if it can be scaled to lie in an annul...

Passive bistatic radar (PBR) is a well-known topic but research is mainly focused on detection and estimation, and relatively little work has been done on PBR imaging. This paper studies the feasibility of using existing signals for imaging airborne aircraft. The use of the FM band for that purpose is motivated by the geographic prevalence of radio...

In this paper, we propose an exclusion zone around each femtocell in a two-tier heterogeneous network, in which macro users enjoy exclusive interference-free access to a frequency band. The femto users, and macro users outside this region, share the remaining spectrum resource. The exclusion zone is a disc centered on the femto base station because...

In cognitive radio networks, a pair of communicating nodes are required to rendezvous or meet on a common available channel prior to control information exchange. Maintaining a common control channel (CCC), has several drawbacks such as channel saturation, vulnerability to jamming attacks, and spatial variation in the CCC availability. Although cha...

In this paper, we study the sum-rate maximization problem in a single-cell massive MIMO downlink system with K users. Unlike the conventional sum-power constraint (SPC) that limits the total average power over all the transmit antennas, the more practical per-antenna power constraint (PAPC) is considered. A precoding scheme based on the principle o...

In this paper, we propose a battery-aided demand response strategy to minimize the energy expenditure incurred by grid-tied systems such as domestic and industrial loads. Unlike existing algorithms in the literature, our proposed strategy takes into account the non-linear behavior of the rechargeable battery. In addition, continuous-time block tari...

The transmission capacity of wireless networks is limited by the intensity of the interference received from concurrent transmissions. Interference causes serious performance degradation, particularly when no centralized controller within the network exists. Cognitive radio (CR) is a promising solution for distributed interference management as use...

In this paper, we consider energy usage in a three node, two-way relay system with stochastic data arrivals and Gaussian channels. Specifically, we allow for a set of transmission modes, assuming a multi-access uplink transmission with the relay as an optimal multi-user receiver, and find the optimal allocation of time and energy resources to the m...

In this work, we consider a low-earth orbit (LEO) satellite communication system with a high-altitude platform (HAP) as a relay on the downlink. Both the satellite and the HAP are assumed to harvest solar energy to power their operations. The aim is to minimize the energy usage over one orbit, while delivering a given amount of information from the...

This paper studies a multiple-input single-output (MISO) broadcast channel (BC) featuring simultaneous wireless information and power transfer (SWIPT), where a multi-antenna access point (AP) delivers both information and energy via radio signals to multiple single-antenna receivers simultaneously, and each receiver implements either information de...

In this paper, we propose an optimal energy management strategy that minimises the energy bill incurred by cellular base stations (CBSs) in a smart grid environment. The CBS can harvest renewable energy for local use and is equipped with a limited-capacity battery that is subject to charging and discharging losses. Because the proposed optimal stra...

In this paper, we consider three transmit strategies for the fading three-node, two-way relay network (TWRN) -- physical-layer network coding (PNC), digital network coding (DNC) and codeword superposition (CW-Sup). The aim is to minimize the total average energy needed to deliver a given pair of required average rates. Full channel state informatio...

In this paper, we study the problem of minimizing the energy cost incurred by a Cellular Network Operator (CNO) in a Smart Grid (SG) environment. We consider a CNO that deploys several Cellular Base Stations (CBS) to serve a given geographical area. Each CBS is equipped with a limited-capacity battery and can be powered either by the SG or by a ren...

Cloud radio access network (C-RAN) has been recently proposed, in which densely deployed access points (APs) are empowered by cloud computing, to achieve enormous mobile data rates. However, close proximity of many active APs results in more severe interference and also inefficient energy consumption. To tackle this problem, we propose a joint down...