Kwan-Wu Chin

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• PhD
• Professor at University of Wollongong

This paper considers a topology construction problem involving a fixed-wing Unmanned Aerial Vehicle (UAV), a set of quad-rotor UAVs and mobile ground users. The constructed topology must maximize the max-min flow rate of ground users over a given planning horizon. To this end, we outline a Mixed Integer Linear Program (MILP) that jointly optimizes...

Complete targets coverage is required by many Internet of Things (IoT) applications. In this respect, an important goal is to maximize the number of time slots with complete targets coverage. Achieving such coverage is challenging when devices experience spatio-temporal energy arrivals. To this end, this paper outlines a deep learning assisted appr...

This article considers an unmanned aerial vehicle (UAV) that is used in industrial Internet of things (IIoT) networks to execute one or more preloaded computation tasks. A key novelty is that these tasks support imprecise computation, where each task has a mandatory and optional part. Another novelty is that both parts of a task require data from o...

This paper considers an operator that deploys Unmanned Aerial Vehicles (UAVs) to service requests from users/devices in an Internet of Things (IoT) network; each request requires one or more so called services such as a database or an Artificial Intelligence (AI) model. A key problem faced by the operator is to determine which services to place on...

This paper considers a satellite network with free space optical links, where satellites are able to form intra and inter satellite links. Briefly, intra-satellite links connect satellites in the same orbit plane, and inter-satellite links (ISLs) connect satellites on different orbital planes. In this respect, a key problem is to jointly determine...

This paper considers the problem of scheduling uplinks and downlinks transmissions in an Internet of Things (IoT) network that uses a mode-based time structure and Rate Splitting Multiple Access (RSMA). Further, devices employ power splitting to harvest energy and receive data simultaneously from a Hybrid Access Point (HAP). To this end, this paper...

This paper studies virtual network function (VNF) scheduling in energy harvesting virtualized Internet of Things (IoT) networks. Unlike prior works, sensor devices leverage imprecise computation to vary their computational workload to conserve energy at the expense of computation quality. In this respect, an optimization problem of interest is to m...

Devices in Internet of Things (IoT) networks are likely to operate over a shared medium, and thus they have to use a channel access protocol to minimize or avoid collision. Further, they may have to harvest Radio Frequency (RF) energy in order to transmit or/and receive data. To this end, this survey presents the first comprehensive review of prior...

This paper considers a network design problem using Unmanned Aerial Vehicles (UAVs). It aims to create a network to provide communication and computation service to a set of source-destination ground node pairs. The main performance metric is the minimum amount of computed data among a set of source-destination pairs. To optimize this metric, we ou...

In this article, we study an industrial Internet of Things (IIoT) network with a sink/gateway that is capable of decoding multiple transmissions via successive interference cancellation (SIC), and energy harvesting devices tasked with providing complete targets coverage of targets. In particular, we study a novel question: how to schedule the sensi...

This paper considers the problem of scheduling uplinks and downlinks transmissions in an Internet of Things (IoT) network that uses a mode-based time structure and Rate Splitting Multiple Access (RSMA). Further, devices employ power splitting to harvest energy and receive data simultaneously from a Hybrid Access Point (HAP). To this end, this paper...

This paper considers the problem of monitoring one or more mobile targets over a given planning horizon. Unlike previous works, it leverages ambient backscatter communication to reduce the energy expenditure of sensor nodes in order to prolong coverage lifetime. We outline a mixed integer linear program (MILP) that aims to maximize the number of ti...

In Internet of Things (IoT) networks, Unmanned Aerial Vehicles (UAVs) play a critical role as mobile nodes that can be deployed to carry out data collection and computation. In this respect, this paper considers an operator that deploys UAVs to satisfy requests from IoT applications that require Virtual Network Functions (VNFs) that may communicate...

This paper considers maximizing coverage quality in Internet of Things (IoT) networks using Unnamed Aerial Vehicles (UAVs) to augment the link from solar-powered devices to a sink/gateway. Specifically, it aims to jointly optimize the assignment of UAVs to hovering points or a charging station, time in which devices monitor targets, and the amount...

In this article, we consider an unmanned aerial vehicle (UAV) with an in-band full-duplex radio that is used to interconnect industrial Internet of things (IIoT) devices and exploit their computation and energy resources to help process data. We formulate a mixed integer linear program to optimize the first sampling rate of each device, second amou...

A fundamental issue in blockchain systems is their scalability in terms of data storage, computation, communication, and security. To resolve this issue, a promising research direction is coding theory, which is widely used for distributed storage, recovery from erasures or channel errors and/or to reduce communication cost. To this end, this paper...

This article considers topology construction or design using unmanned aerial vehicles (UAVs) in order to maximize the traffic flow from a given source to a destination node. To this end, it outlines a mixed-integer linear program (MILP) to optimize the placement of UAVs and the routing of flow from the said source to the destination. The problem is...

The nodes, e.g., access points and clients, in current WiFi networks rely on carrier sense multiple access (CSMA) for channel access. This means they rely on a clear channel assessment (CCA) threshold to determine when it is safe to transmit a packet. In practice, this threshold is fixed, and nodes do not adapt their CCA threshold given varying cha...

This paper studies data collection in a wireless powered Internet of Things (IoT) network with a hybrid access point (HAP). A fundamental problem at the HAP is to determine the number of time slots over a given planning horizon that is used to charge and collect data from devices. To this end, we outline a mixed integer linear program (MILP) to det...

This paper considers task scheduling in solarpowered Internet of things (IoT) networks where devices are capable of sharing energy wirelessly. Our aim is to minimize the completion time of all tasks. We outline a novel mixed integer linear program (MILP) to schedule tasks and determine whether devices share their harvested energy via radio frequenc...

Many applications, e.g., digital twins, rely on sensing data from Internet of Things (IoT) networks, which is used to infer event(s) and initiate actions to affect an environment. This gives rise to concerns relating to data integrity and provenance. One possible solution to address these concerns is to employ blockchain. However, blockchain has hi...

This paper studies a coverage problem in Internet of things (IoT) networks using unmanned aerial vehicles (UAVs) supported by solar-powered charging platforms. The problem at hand is to determine an assignment of UAVs to either a charging station or a monitoring point over a planning horizon. A key constraint is $K$ -coverage, where given a set o...

Future WiFi networks require a channel access method that provides users with high capacity. Such a method must consider (1) channel bonding, which improves the transmission capacity of Access Points (APs), and (2) spatial reuse, where APs tune their Clear Channel Assessment (CCA) threshold and transmit power in order to transmit concurrently with...

This paper considers targets coverage in energy harvesting Internet of Things (IoT) networks. Specifically, solar-powered sensor devices employ network virtualization technology to partition their resources, such as energy, memory, and computation workload, in order to serve requests with different coverage requirements. Our objective is to maximiz...

This paper studies sample delivery in a multi-hop network where a power beacon charges devices via radio frequency (RF) signals. Devices forward samples with a deadline from a source to a sink. The goal is to minimize the power beacon’s transmit power and guarantee that samples arrive at the sink with probability $(1-\epsilon)$ by their deadline,...

In future Internet of Thing (IoT) networks, devices can be leveraged to compute tasks or services. To this end, this paper addresses a novel problem that requires devices to collaboratively execute tasks with dependencies. A key consideration is that in order to conserve energy, devices may execute a task in approximate mode, which generate errors....

This letter considers approximate computing and task offloading in a solar powered Internet of Things (IoT) network. Specifically, it addresses the novel problem of minimizing the energy consumption of IoT devices by either offloading their tasks or executing these tasks in approximate mode. To this end, this letter outlines a novel mixed integer l...

Many industries now rely on drones to monitor infrastructures. In this respect, this article considers maximizing the revenue of an Industrial Internet of Things operator that provides two services: 1) data trading; and 2) drones rental. In service 1), the operator sells data of locations/points it acquired via drones. For service 2), it rents idle...

This paper considers routing and link scheduling in a two-tier wireless Internet of Things (IoT) network. The first tier consists of routers that communicate via active Radio Frequency (RF) transmissions. The second tier consists of passive tags that backscatter ambient RF signals from routers. Our objective is to maximize the network throughput at...

This article considers deriving set covers or the set of active nodes that are responsible for monitoring all targets in an Internet of Things (IoT) network. A key distinction to prior works is that this article considers sensor nodes aided by backscatter communications, which allow them to communicate with negligible energy cost using ambient radi...

This article considers energy delivery by a hybrid access point (HAP) to one or more radio-frequency (RF)-energy harvesting devices. Unlike prior works, it considers imperfect and causal channel state information (CSI) and probabilistic constraints that ensure devices receive their required amount of energy over a given planning horizon. To this en...

Virtualization of devices operating in Internet of Things (IoT) networks allows them to host functions or tasks from different users; these devices can thus execute multiple on demand sensing and data processing services concurrently. Devices, however, have limited energy and operational lifetime. To this end, this article considers supporting virt...

Many applications operating in the Internet of Things (IoT) require timely and fair data collection from devices. This has motivated research into a new metric called Age of Information (AoI). This paper contributes to this effort by proposing to minimize the maximum average AoI (min-max AoI) in a multi-hop IoT network comprising of solar-powered P...

(Arxiv: https://arxiv.org/abs/2208.09255v1) This paper reviews and highlights how coding schemes have been used to solve various problems in blockchain systems. Specifically, these problems relate to scaling blockchains in terms of their data storage, computation and communication cost, as well as security. To this end, this paper considers the u...

The proliferation of IEEE 802.11 or WiFi networks, and the explosive growth in traffic demands call for solutions to maximize the capacity of WiFi networks. Hence, maximizing the spatial reuse of WiFi networks is critical as doing so allows multiple concurrent transmissions. In this respect, a critical network parameter, Clear Channel Assessment (C...

This letter considers the problem of embedding the maximum number of Virtual Network Requests (VNRs) in an Internet of Things (IoT) network with Power Beacons (PBs). It presents a Mixed Integer Linear Program (MILP) and a heuristic to determine the transmit power allocation of PBs, mappings of virtual nodes and edges onto devices and links, and a l...

Internet of Things (IoTs) networks are responsible for monitoring an environment or targets such as vehicles. A key issue is determining the active time of a set of sensor nodes, so called set cover, that monitors all targets. This requires battery level knowledge at sensor nodes as an incorrect active time may cause energy outage, leading to uncov...

This article considers routing and uplinks scheduling in space–air–ground integrated networks. Specifically, it considers a successive interference cancellation-capable unmanned aerial vehicle (UAV) that collects data from ground devices operating in an Internet of Things network. Its objective is to maximize the minimum flow rate to a terrestrial...

Data collection is a fundamental operation in energy harvesting industrial Internet of Things networks. To this end, we consider a hybrid access point (HAP) or controller that is responsible for charging and collecting $L$ bits from sensor devices. The problem at hand is to optimize the transmit power allocation of the HAP over multiple time fram...

The switches in legacy networks perform both control and data forwarding operations. In contrast, in a software defined network (SDN), a controller is responsible for network control and each SDN-switch ( ${s}$ -switch) only forwards data packets. Advantageously, controllers can be upgraded easily to run state-of-the-art network configuration an...

This paper studies targets coverage in an energy harvesting (EH) Internet of things (IoT) network. Specifically, it addresses the problem of activating subsets of EH sensor nodes to monitor targets such as valuable assets or the ingresses and egresses of a building. A key requirement, so called complete targets coverage, is that all targets must be...

This article considers the collection and processing of data by solar-powered servers operating in an Internet of Things (IoT) network. Specifically, these servers aim to cooperatively maximize the amount of data collected from devices and computed over multiple time slots. To achieve this aim, they must consider computation deadline, time-varying...

This paper studies a novel wireless powered Internet of Things (IoT) network that consists of (a) a Hybrid Access Point (HAP) that charges devices and also helps facilitate backscattering transmissions, (b) devices that use active Radio Frequency (RF) and backscattering transmissions, and (c) a mobile data collector. Our aim is to maximize the amou...

This article considers radio-frequency (RF) energy harvesting devices that use an irregular slotted Aloha (IRSA) channel access protocol to transmit their data to a hybrid access point (HAP). Specifically, it addresses the fundamental problem of optimizing the number of packet replicas transmitted by each device in each time frame. Unlike prior wor...

This letter considers optimizing information freshness in a network with Radio Frequency (RF)-energy harvesting wireless devices. A Hybrid Access Point (HAP) charges these devices and instructs a subset of devices to carry out sampling and transmit their sample. We outline a Distributed Q-Learning (DQL) algorithm that allows the HAP to select devic...

Devices in Internet of Things (IoT) networks are required to execute tasks such as sensing, computation and communication. These devices, however, have energy limitation, which in turn bounds the number of tasks they can execute and their tasks execution time. To this end, this paper considers energy delivery, tasks assignment and execution in a Ra...

This paper considers a Radio Frequency (RF) powered Internet of Things (IoT) network that exploits ambient backscatter communications to maximize the minimum number of samples of targets. We propose a Maximum Backscatter Opportunity Search (MBOS) heuristic algorithm to construct set covers to ensure complete targets coverage. Our results demonstrat...

This paper studies the complete targets coverage problem in a novel and practical context: sensor nodes operating in an Internet of Things (IoT) network that have a dual-battery system with non-ideal properties. Specifically, sensor nodes have batteries that cannot be charged and discharged simultaneously. Also, sensor nodes must fully discharge/ch...

Future green WiFi networks will require Access Points (APs) to minimize their energy usage and maximize their spectral efficiency; equivalently, APs need to maximize their Energy Efficiency (EE). To this end, transmit power control and channel bonding are promising approaches to improve the EE of APs. However, these approaches may cause interferenc...

This paper considers the novel problem of upgrading a legacy network into a Software Defined Network (SDN) over multiple stages and saving energy in the upgraded network or hybrid SDN. That is, in each stage, the problem at hand is to select and replace legacy switches with SDN switches, and reroute traffic to power off as many unused cables as pos...

Recently, many works seek to exploit the negligible transmission cost of backscattering radio frequency (RF) signals, and also demonstrated its feasibility in allowing passive or batteryless tags to communicate over multiple hops. In this context, this article studies data collection in a multihop Internet of Things (IoT) wireless network consist...

This paper considers data upload from multiple devices to a rotary-wing Unmanned Aerial Vehicle (UAV) equipped with a Successive Interference Cancellation (SIC) radio. The problem at hand is to optimize the UAV’s data collection points, and the set of transmitting devices at each point. We outline three contributions. The first is an Integer Linear...

This paper considers routing and link scheduling in a two-tier wireless backhaul network. The first tier consists of routers and the second tier consists of Radio Frequency (RF)-energy harvesting Internet of Things (IoT) devices that rely on routers for energy. Our aim is to derive the shortest Time Division Multiple Access (TDMA) link schedule tha...

Upgrading a legacy network to a Software Defined Network in stages, and minimizing the energy consumption of a network are now of great interest to operators. To this end, this paper addresses a novel problem: minimize the energy consumption of a network by upgrading switches over multiple stages subject to the available monetary budget at each sta...

This paper considers wireless link scheduling in a new setting: nodes with Energy Harvesting (EH) as well as energy sharing capabilities. We propose a Mixed Integer Linear Program (MILP) to determine (i) the shortest link schedule, whereby active links in the same slot adhere to the physical interference model, (ii) the optimal transmission power o...

This paper considers a novel Internet of Things (IoT) network comprising of sensor devices and Power Beacons (PBs); both types of nodes are equipped with a Cognitive Radio (CR). In addition, these sensor devices are powered by Radio Frequency (RF) signals from PBs. Our aim is to maximize the minimum rate of devices acting as sources. We outline the...

This article considers data collection in a wireless-powered Internet-of-Things (IoT) network. Specifically, it addresses the novel problem of determining the mode of each time slot, where a hybrid access point (HAP) needs to decide whether to charge or collect data from devices. Also, in data time slots, HAP has to decide on a device for data tr...

Future WiFi networks will be powered by renewable sources. They will also have radio frequency (RF)-energy harvesting devices. In these networks, a solar-powered access point (AP) will be tasked with supporting both nonenergy harvesting or legacy data users such as laptops, and RF-energy harvesting sensor devices. A key issue is ensuring the AP u...

This paper studies a novel problem that aims to maximize the number of uploaded samples by devices in wireless powered Internet of Things (IoTs) networks. To do so, it takes advantage of ambient backscatter communications (AmBC) to help sensor devices conserve energy, and thus leaving them with more energy to collect samples. We outline a Mixed Int...

A multi‐cell network that uses orthogonal frequency division multiplexing access (OFDMA) is studied here. Unlike prior works, the proposed network consists of both (i) legacy data users that do not have energy harvesting capability and have a minimum data rate requirement and (ii) radio frequency (RF)‐energy harvesting devices with a minimum energy...

This letter considers minimizing the time required to collect $L$ bits from each Radio Frequency (RF)-energy harvesting device serviced by a multi-antenna Hybrid Access Point (HAP). We outline a Mixed Integer Non-Linear Program (MINLP) to determine the transmit power allocation of the HAP and devices over multiple time slots. We also outline a...

This paper considers the novel problem of deriving a Time Division Multiple Access (TDMA) link schedule for rechargeable wireless sensor networks (rWSNs). Unlike past works, it considers: (i) the energy harvesting time of nodes, (ii) a battery cycle constraint that is used to overcome so called memory effects, and (iii) battery imperfections, i.e.,...

We consider a Radio Frequency (RF)-charging network where sensor devices harvest energy from a solar-powered Hybrid Access Point (HAP) and transmit their data to the HAP. We aim to optimize the power allocation of both the HAP and devices to maximize their Energy Efficiency (EE), which is defined as the total received data (in bits) for each Joule...

Future Internet of Things (IoTs) networks will consist of a Hybrid Access Point (HAP) that powers devices via Radio Frequency (RF) signals. These devices harvest RF-energy and are tasked with monitoring target(s) such as vehicles at key locations. In order to maximize their expected targets monitoring time, this paper considers the problem of opt...

In this article, we consider a network with a hybrid access point (HAP) and radio frequency (RF)-energy harvesting wireless devices. The HAP is responsible for charging these devices and receiving their data. Our problem is to select a set of devices to transmit in each time slot so as to maximize a given reward over a planning horizon. In contrast...

This article considers an energy-harvesting wireless sensor network (EH-WSN) where nodes have a dual alternative battery system. We aim to design a routing protocol that transmits a given amount of data to a sink using the minimum number of time slots. To this end, we first formulate the routing problem as a mixed-integer linear program (MILP) and...

This paper considers broadcast communications or information dissemination in Fixed-Schedule Dynamic Networks (FSDNs). It shows that the notion of spanning arborescences, commonly used in static networks, is not applicable in FSDNs. This paper then introduces two new concepts on spanning arborescences: (i) $t$ -arborescence — an arborescence in w...

This paper considers a swarm of Unmanned Aerial Vehicles (UAVs) managed by a ground station. These UAVs may experience highly varying channel gains and collisions when they transmit to the ground station. To this end, we introduce a novel Learning Medium Access Control (L-MAC) for multi-rate UAVs and equip the ground station with Successive Interfe...

The Access Points (APs) in a Wireless Local Area Network (WLAN) must be assigned one or more channels to meet traffic demands from users. This ensures a high user satisfaction. To date, prior works on channel assignment assume APs have a fixed traffic demand, meaning they do not consider or adapt to spatio-temporal changes in traffic demands. To th...

Future Internet of Things (IoTs) networks will have Radio Frequency (RF)-energy harvesting devices powered by a Power Beacon (PB). These devices will be tasked with collection and transmission of data over multiple hops to a fusion center. In this paper, our aim is to maximize the minimum data gathering rate of devices acting as sources. We formula...

Future Internet of Things networks are likely to have radio frequency (RF) energy harvesting sensor devices and also solar-powered hybrid access points (HAPs) that help monitor one or more targets such as assets in a warehouse. In this setting, we outline three contributions that ensure devices’ monitor targets at all times and upload the maximum n...

This letter considers a novel problem that aims to derive the shortest possible Time Division Multiple Access (TDMA) schedule for use by ground nodes to upload their data to an Unmanned Aerial Vehicle (UAV) over random channel gains. Its key novelties include equipping the UAV with a Successive Interference Cancellation (SIC) radio and applying a G...

In this paper, we consider a solar-powered Access Point (AP) that is tasked with supporting both non-energy harvesting or legacy data users such as laptops, and devices with Radio Frequency (RF)-energy harvesting and sensing capabilities. We propose two solutions that enable the AP to manage its harvested energy via transmit power control and also...

Future Internet of Things (IoTs) networks will consist of RF-energy harvesting devices that are charged by solar-powered Power Beacons (PBs). To this end, this paper aims to maximize the minimum data rate of devices acting as sources operating in a multi-hop IoTs network. The main problem is to decide the amount of energy delivered by solar-powered...

In this paper, we consider a Hybrid Access Point (HAP) that supplies energy to sensor devices tasked with monitoring one or more mobile targets with a known trajectory. The HAP's goal is to maximize a Quality of Monitoring (QoM) metric that is a ratio of the following quantities: (i) distance between a sensor device and a target, and (ii) duration...

Unmanned Aerial Vehicles (UAVs) require frequent transmissions to a ground station. In this paper, we consider Time Division Multiple Access (TDMA) and equip the ground station with a Successive Interference Cancellation (SIC) radio, and thereby, allowing it to receive multiple transmissions simultaneously. A key problem is to identify a suitable T...

We consider an Access Point (AP) equipped with multiple antenna elements and an in-band full-duplex radio. In each time slot, it needs to poll clients for uplink and/or carry out downlink transmissions, and to allocate its antenna elements for data transmissions and interference cancellation. We outline a Markov Decision Process (MDP) and use it to...

In a wireless network, a well designed link scheduler ensures links are activated frequently and experience minimal or no interference, meaning these links will have a high capacity. A challenging problem, however, is random or uncertain channel gains. Another challenge is determining whether a set of links can co-exist together, meaning they d...

This article considers channel access in a radio frequency (RF) powered Internet of Things network that consists of a successive interference cancellation (SIC) capable hybrid access point (HAP) and RF-energy harvesting devices. Unlike previous works, in addition to considering random channel access, both the HAP and these devices have imperfect ch...

We consider a Hybrid Access Point (HAP) that is equipped with a Successive Interference Cancellation (SIC) radio, and it is responsible for charging Radio Frequency (RF) energy harvesting devices. In addition, the HAP assigns one or more uplinks data transmission slots to these devices. In this work, we address an important and challenging problem:...

We consider Rechargeable Wireless Sensor Networks (R-WSNs) where nodes harvest energy from both solar and the Radio Frequency (RF) transmissions of their neighbors. Our aim is to maximize the minimum source or sensing rate of nodes. This rate is determined by the available energy at sensor nodes as well as link capacity, which is determined by the...

We consider a Hybrid Access Point (HAP) that charges one or more energy harvesting devices via Radio Frequency (RF). These devices then transmit their data to the HAP. To date, prior works assume devices use Time Division Multiple Access (TDMA) for channel access, and these devices are able to transmit using any amounts of harvested energy. By cont...

Backscatter communication can potentially find wide IoT applications because of its negligible energy consumption. Traditional backscatter communication relies on either dedicated Radio Frequency (RF) sources, such as RF identification readers and power beacons, or ambient RF sources, e.g., TV and cellular signals. In this paper, we study a backsca...