Kyung-Joon Park

Daegu Gyeongbuk Institute of Science and Technology | DGIST · Department of Information and Communication Engineering

Multijob production (MJP) is a class of flexible manufacturing systems, which produces different products within the same production system. MJP is widely used in product assembly, and efficient MJP scheduling is crucial for productivity. Most of the existing MJP scheduling methods are inefficient for multijob serial lines with practical constraint...

Digital Transformation integrates information technology across a broad spectrum of industrial sectors. Industrial Cyber-Physical Systems (ICPS) play a vital role in this transformation by harmonizing machinery, production, logistics, and societal needs through innovative information technologies. This paper investigates the adoption of industrial...

In the Industrial Internet of Things (IIoT), energy efficiency is critical for effective management of physical systems. To achieve stable control of IIoT with minimal energy consumption, it is essential to co-design the controller and the wireless network. In this paper, we present a novel reinforcement learning (RL) approach called the Learning-e...

Most of the existing studies on analyzing the productivity of serial production lines focus on cases where the coefficient of variation ( $CV$ ) for both uptime and downtime is less than 1. Hardly any result is available when $CV>1$ , i.e., uptime and downtime of machines exhibit high variability. The improvement of the production lines with hig...

Automated measurement of the machine reliability parameters for a production system enables a continuous update of the mathematical model of the system, which can be used for various analyses toward productivity improvement. However, the continuous update may be impeded by some machines of which automated parameter measurements are out of order. Su...

Cyber-physical systems (CPS) are considered the integration of physical systems in the real world and control software in computing systems. In CPS, the real world and the computing systems are connected through networks with real-time information exchange. The introduction of networking technologies in CPS has substantial advantages in terms of sy...

Wireless sensor–actuator networks (WSAN) for real-time reliable communications are being embraced in the Industrial Internet of Things. One key property required for WSAN is adaptability with respect to dynamic environments. Most existing studies assume that a network manager computes global schedules and disseminates schedule information to ever...

A tactical sensor network is a representative safety-critical environment that should satisfy strict guarantee of the requirements of tactical traffic. However, because of the lack of infrastructure in a military network environment, resource constraints on wireless channel and nodes can cause problems such as network congestion and packet collisio...

Controller failures can result in unsafe physical plant operations and deteriorated performance in industrial cyber–physical systems. In this paper, we present a controller switching mechanism over wireless sensor–actuator networks to enhance the resiliency of control systems against problems and potential physical failures. The proposed mechanism...

Networks on the cyber-physical systems (CPSs) configure feedback control loops between physical systems in the real world and control software in the cyber world. Malicious behaviors on the networks can increase network delays by exhausting limited network resources and security vulnerabilities to destabilize CPSs, which are entitled the network de...

Wireless technologies such as WirelessHART are being adopted in industrial wireless sensor-actuator networks (IWSAN), which is required to provide reliable quality of control (QoC). This work focuses on adaptively selecting the best network path for reliable QoC in IWSAN. The main challenge is estimating the time-varying packet delivery ratio (PDR)...

This paper presents a case study of continuous productivity improvement of an automotive parts production line using Internet of Everything (IoE) data for fault monitoring. Continuous productivity improvement denotes an iterative process of analyzing and updating the production line configuration for productivity improvement based on measured data....

Sharding is a promising solution to achieving scalability within the blockchain network. A sharded blockchain network consists of a beacon chain and several committees powered by the participants (i.e., validators) through the Proof-of-Stake (PoS) consensus protocol. Efficient and scalable as it can be, the sharded blockchain based on PoS is vulner...

A cyber-physical system (CPS) is the integration of a physical system into the real world and control applications in a computing system, interacting through a communications network. Network technology connecting physical systems and computing systems enables the simultaneous control of many physical systems and provides intelligent applications f...

To perform advanced operations with unmanned aerial vehicles (UAVs), it is crucial that components other than the existing ones such as flight controller, network devices, and ground control station (GCS) are also used. The inevitable addition of hardware and software to accomplish UAV operations may lead to security vulnerabilities through various...

Cyber-physical attacks exploit intrinsic natures of physical systems and can severely damage cyber-physical systems (CPSs) without being detected by the conventional anomaly detector. In this paper, based on software-defined networking, we propose a holistic resilient CPS framework that can detect, isolate, and recover from cyber-physical attacks i...

It has been reported that in the thermal control of real-time computing systems, zero-mean thermal sensor noise can induce a significant steady-state error between the target and actual temperatures of a CPU. Unlike the usual case of zero-mean sensor noise resulting in zero-mean temperature fluctuations around the target value, this noise-induced t...

In vehicular cyber-physical systems, cars are connected to create a mobile network called a vehicular ad hoc network (VANET) to perform various functions, including improved awareness of the surrounding environment. Moving vehicles continually broadcast beacon signals containing information such as position, heading, acceleration, steering angle, v...

The number of pedestrian accidents continues to keep climbing. Distraction from smartphone is one of the biggest causes for pedestrian fatalities. In this paper, we develop SaferCross, a mobile system based on the embedded sensors of smartphone to improve pedestrian safety by preventing distraction from smartphone. SaferCross adopts a holistic appr...

Cyber-physical system (CPS) provides a well-organized integration between communication , computation , and control (3C) technologies. CPS has been widely used in the vehicular networks and it requires to discover multimodal data from the physical system to make appropriate decisions and actions, for example, congestion warnings, applying bra...

This study investigates the synergy between centralized and decentralized (i.e., ad hoc) data scheduling in vehicular ad hoc networks (VANETs) for offloading and balancing the workloads of roadside units (RSU) in bidirectional road scenarios. In the centralized scheduling, an RSU schedules data dissemination using a hybrid of infrastructure-to-vehi...

Processor thermal control in real-time systems is crucial because overheated processors may result in critical performance degradation or even system failure. The main challenges in processor thermal control in real-time systems are as follows: (i) the need to satisfy both real-time and thermal constraints; (ii) uncertain system dynamics; and (iii)...

A cyber–physical system (CPS) consists of physical devices and operations that are closely controlled and monitored by computational processes. This concrete connection involves the real-time actuation of physical devices, real-time sensing of physical quantities, and modeling and control of the overall system. A CPS may be connected to the Interne...

Conventionally, a node or vehicle in the Named Data Networking (NDN) sends an interest packet to discover information and receives a single data packet in response. However, in the case of named data Vehicular Cyber-Physical System (VCPS), a vehicle may require content from multiple vehicles in the network. Therefore, NDN forwarding daemon must rec...

To improve vehicle safety, vehicular ad hoc networks (VANETs) periodically broadcast safety messages known as beacons. Consequently, it becomes safety critical to guarantee the timely reception of periodic beacons under the time-varying environments of VANET. However, existing approaches typically measure the packet delivery ratio, which is a time-...

A cyber-physical system (CPS) is an entanglement of the physical and the computing systems by real-time information exchange through networking, which can be considered as real-time IoT because of end-to-end real-time performance guarantee. Most of societal infrastructures such as transportation systems, smart power grid, smart factory, and smart b...

Named Data Networking (NDN) is one of the future networking architectures that communicates content using names, instead of the node addresses. It uses a very simple pull-based communication mechanism to retrieve content by sending an Interest message, and the node that has the required content or producer node replies with the Data message. In wir...

Design of wireless control systems has been extensively studied, which is one of the fundamental issues in cyber-physical systems. In this paper, we empirically investigate heterogeneous sampling rate assignment with a testbed when multiple physical systems are controlled through an IEEE 802.11 network. Among the critical design variables in wirele...

In this paper, we propose a resilient architecture for network and control co‐design, Wireless‐Simplex (W‐Simplex), which can ensure control performance by adaptively tuning the network and control parameters against wireless channel uncertainty in cyber‐physical systems. To the best of our knowledge, there has been no research into resilient netwo...

A traffic monitoring system (TMS) is an integral part of Intelligent Transportation Systems (ITS) for traffic analysis and planning. This paper addresses the endemic cost issue of deploying a large number of TMSs to cover huge miles of two-lane rural highways (119,247 miles in U.S.). A low-cost and portable TMS called DeepWiTraffic based on COTs Wi...

This article presents an attack-resilient architecture for cyber-physical systems (CPSs). As a case study, the authors build a radio-based train control testbed and validate the proposed resilient design architecture. The target CPS application is a hierarchical control system.

As various wireless devices share the same frequencies in the unlicensed 2.4 GHz Industrial Scientific Medical (ISM) band, frequency sharing has become a challenging issue in the heterogeneous network. Many Wi-Fi applications increase network traffic and lead to the significant performance loss of other protocol devices including ZigBee for critica...

Recently, unmanned aerial vehicle (UAV) or so called drones are used in various applications. Especially, UAVs are used for rescue systems, disaster detection, and military purposes, as well as for leisure and commercial purposes. In particular, UAVs that are controlled over networks by ground control stations (GCS) can provide various services wit...

[This corrects the article on p. 210 in vol. 11, PMID: 28572760.].

Named Data Networking (NDN) uses the content name instead of its location within the Interest message to locate the content within the network. Interest is broadcasted by the content seeking node over the wireless channel with specific content name and waits for the Data message containing the actual content. The broadcast region of an Interest is...

Underwater Acoustic Sensor Network (UASN) comes with intrinsic constraints because it is deployed in the aquatic environment and uses the acoustic signals to communicate. The examples of those constraints are long propagation delay, very limited bandwidth, high energy cost for transmission, very high signal attenuation, costly deployment and batter...

The mechanism of tinnitus suppression after cochlear implantation (CI) in single-sided deafness (SSD) is not fully understood. In this regard, by comparing pre- and post-CI quantitative electroencephalography (qEEG), we explored cortical changes relevant to tinnitus improvement. In SSD patients who underwent CI, qEEG data were collected: (1) before...

Drones are broadening their scope to various applications such as networking, package delivery, agriculture, rescue, and many more. For proper operation of drones, reliable communication should be guaranteed because drones are remotely controlled. When drones experience communication failure due to bad channel condition, interference, or jamming in...

In wireless sensor networks powered by battery-limited energy harvesting, sensor nodes that have relatively more energy can help other sensor nodes reduce their energy consumption by compressing the sensing data packets in order to consequently extend the network lifetime. In this article, we consider a data compression technique that can shorten t...

Network traffic can be divided into delay-sensitive and delay-tolerant traffic. Each delay-sensitive real-time flow has a different end-to-end delay deadline, and has to be delivered by that deadline. In general, real-time flows are to be processed prior to delay-tolerant flows, and each real-time flow may have the relative priority depending on it...

In this paper, we deal with the problem of assuring medical-grade quality of service (QoS) for real-time medical applications in wireless healthcare systems based on IEEE 802.11e. Firstly, we show that the differentiated channel access of IEEE 802.11e cannot effectively assure medical-grade QoS because of priority inversion. To resolve this problem...

Within a macrocell with a large coverage area, multiple small cells are deployed such that each small cell base station (SBS) supports wireless service demands from user equipments (UEs). Each UE can be simultaneously served by multiple SBSs for quality of service (QoS) enhancement. When there exist hotspot areas with a number of UEs, the SBSs near...

Cyber-physical systems (CPS) have emerged as a promising research paradigm, which is the convergence of control, communication, and computation. In CPS, real-time transactions visit multiple resources such as sensors, actuators, networks, and microprocessors. One fundamental issue, which is called control and real-time scheduling co-design, is how...

As a promising technology, drones are broadening its scope into various applications such as agriculture, delivery, broadcast, leisure, rescue, and many more. When drones experience communication failure due to interference, non-line-of-sight, or jamming, a possible solution is spatial retreat to evacuate drones from the communication failure area....

The advent of the Internet of things (IoT) is changing the way how we interact with the physical world. However, the current Internet suffers from exponential increase in bandwidth demand. In order to resolve the bandwidth issue, we can consider aerial networks by unmanned aerial vehicles (UAV) or the so-called drones for establishing a three-dimen...

Wireless body area networks (WBANs) in the industrial, scientific, and medical (ISM) bands have been increasingly adopted for various medical applications. Due to the shared nature of the ISM bands, when a WBAN coexists with a wireless local area network (WLAN), performance of WBAN may significantly degrade because of asymmetric attributes between...

Generally in mobile devices, localization is a critical issue to provide various services. A common way to find location is to use GPS. However, GPS has several limitations such as its reliability. Especially in none line of sight (NLOS) situations such as indoor environment, GPS is unable to find location. This could be a serious issue for drone f...

Traditional aerial networks by UAV have several issues such as limited battery capacity and frequent handover caused by time-varying aerial environment. In particular, failure of resolving the handover issue will induce not only unsuccessful seamless handover but also frequent handover attempts. In this paper, an effective coverage decision algorit...

We propose a data-delivery scheduling scheme for synchronized multi-hop industrial networks where source nodes periodically transmit their data packets. The proposed scheme adjusts the transmission times of source nodes in the network in order to prevent data buffering of the data-flows at the intermediate switches. The data packets can be delivere...

Thermal control is critical for real-time systems as overheated processors can result in serious performance degradation or even system breakdown due to hardware throttling. The major challenges in thermal control for real-time systems are (i) the need to enforce both real-time and thermal constraints; (ii) uncertain system dynamics; and (iii) ther...

A wireless electrocardiogram case study suggests that current CDMA2000 cellular technology has considerable potential in medical telemetry. Modifications to the network protocol stack ensure the highest data integrity and lowest service delay.

The increasing use of wireless networks and the constant miniaturization of electronic devices have empowered the development of wireless body area networks (WBAN). In this paper, we focus on the coexistence problem of WBAN and wireless LAN (WLAN) in medical environments. In order to resolve the unfairness issue caused by coexistence, we propose a...

The reliability of control in cyber-physical systems (CPSs) heavily depends on the network-induced delay. The problem of obtaining a maximum allowable delay bound has been widely studied in the networked control systems (NCS) area. Once the delay bound is derived, the remaining question is how to make a network satisfy the bound. In this paper, we...

A critical performance metric of multi-hop wireless networks is the end-to-end throughput of a multi-hop wireless path. When the packets of a traffic flow originating from a source node are relayed by intermediate nodes (relay nodes), competition between the nodes on the multi-hop routing path incurs transmission delays from the carrier sensing mec...

In this paper, we design an admission control mechanism on top of our previous study on medical-grade wireless LAN. The proposed admission control scheme controls the total number of real-time electrocardiogram (ECG) monitoring connections in order to guarantee the medical-grade quality of service. We verify the performance of the proposed scheme w...

New features are often added incrementally to avionics systems to minimize the need for redesign and recertification. However, it then becomes necessary to check that the timing constraints of existing as well as new applications are met. We facilitate these checks by introducing a new data switch that bounds the latency of end-to-end communication...

In this letter, we introduce medical-grade quality of service (QoS) for wireless healthcare applications. We first investigate the basic QoS requirements of medical applications. We point out that the conventional QoS metric of the packet error rate (PER) is insufficient for evaluating the QoS level of medical applications. The most critical concer...

To maintain the Internet connectivity of a group of nodes in intelligent transportation systems (ITSs), the network mobility basic support (NEMO BS) protocol was standardized. The NEMO BS provides mobility for mobile network nodes (MNNs) in a moving network through a mobile router (MR). Since packet loss in NEMO dramatically increases during a hand...

In this paper, we propose a novel best-effort broadcasting service (BEBS) scheme in cellular networks, which can be used for location-based advertising and real-time multimedia broadcasting. Unlike the conventional broadcasting service that aims to assure reliable data delivery to every user, the main objective of the proposed BEBS is to maximize t...

In this paper, we propose an adaptive tuning scheme of IEEE 802.11 WLAN for healthcare applications. Our proposed method can significantly improve medical-grade quality of service (QoS) and network performance at the same time. Though the conventional IEEE 802.11e protocol supports a certain level of QoS, it does not provide medical-grade QoS due t...

In this paper, we propose an adaptive tuning algorithm for wireless medical applications to in order to meet medical-grade quality of service (QoS). The conventional IEEE 802.11e protocol is designed to satisfy a certain level of QoS, which is insufficient for medical-grade QoS. In the proposed algorithm, we adaptively tune the AIFS value of the IE...

In this paper, we present a simple and effective solution for resolving the in-device coexistence problem of Wi-Fi and Bluetooth. The main idea is to introduce a canceller in the circuit in order to cancel out the in-device interference when Wi-Fi and Bluetooth radios simultaneously operate in the same device. Our proposed approach, entitled the hy...

Vehicular environments require continuous awareness of the road ahead. It is critical that mobile applications used in such environments (e.g., GPS route planners and location-based search) do not distract drivers from the primary task of operating the ...

The network mobility basic support (NEMO BS) protocol has been investigated to provide Internet connectivity for a group of nodes, which is suitable for intelligent transportation systems (ITS) applications. NEMO BS often increases the traffic load and handover latency because it is designed on the basis of mobile Internet protocol version 6 (MIPv6...

Most commercial network switches are designed to achieve good average throughput and delay needed for Internet traffic, whereas hard real-time applications demand a bounded delay. Our real-time switch combines clearance-time-optimal switching with clock-based scheduling on a crossbar switching fabric. We use real-time virtual machine tasks to serve...

The guest editorial section of Computer Communications journal provides an overview cyber-physical systems (CPS) by introducing major issues in CPS along with recent research efforts and future opportunities for CPS. The guest editorial section informs that the term CPS has emerged as a promising research paradigm, which involves the combination of...

Energy use is a key issue in battery-operated mobile devices. In order to extend battery life, mobiles showing video often allow a controlled drop in quality, which is tolerable when the shortcomings of a small screen are combined with the imperfections of visual perception. Both energy consumption and video quality are affected by the Reed-Solomon...

With the advance of hardware technology, more features are incrementally added to already existing networked systems. Avionics has a stronger tendency to use preexisting applications due to its complexity and scale. As resource sharing becomes intense among the network and the computing modules, it has become a difficult task for the system designe...

In order to reduce the overhead of legacy WLANs, the IEEE 802.11n standard defines two aggregation schemes, i.e., A-MSDU and A-MPDU. In general, A-MPDU outperforms A-MSDU due to its selective retransmission capability. However, A-MPDU has a fundamental restriction on the minimum separation in time between the start of two consecutive subframes carr...

In real-time networked control systems, the end-to-end path delays on the communication network should be bounded in order to satisfy the stringent timing constraints of physical system. While the packet delivery on a single path could be significantly affected by network congestion levels, transmitting duplicate packets along multiple paths can ov...

We show how to characterize the energy consumption of individual operating system (OS) functions in the µC/OS-II real time kernel running on an ARM7TDMI-based embedded system. We then derive a strategy for saving energy based on locking more energy-consuming kernel routines of µC/OS-II into the cache and reassigning cache locations to reduce cache...

Network switches are typically designed for best- effort Internet traffic. Most of existing studies have been focused on improving throughput and delay performance in an average sense rather than providing guaranteed delay bound that is critical for real-time applications. It has not been fully investigated how to design an efficient packet switchi...

Self-organizing network (SON), which is an essential technology of future radio networks, is proposed in the 3GPP Long Term Evolution (LTE) specification as a usage case. In this paper, we focus on user equipment (UE)'s power control considering interference mitigation and retransmission constraints especially for physical random access channel (PR...

In this paper, we consider best-effort broadcast service (BEBS) in wireless cellular networks, which can be used for location-based advertising or real-time multimedia broadcasting. Contrary to the conventional broadcasting service that aims to assure reliable data delivery to all users, we establish the objective of BEBS to maximize the effective...

Location-based services (LBSs), such as location-specific contents-providing services, presence services, and E-911 locating services, have recently been drawing much attention in wireless network community. Since LBSs rely on the location information in providing services and enhancing their service quality, we need to devise a framework of direct...

In 3G long term evolution (LTE) systems, the random access channel (RACH) is used for initial access, resource request, and handover. Since the random access delay is determined by the arrival rate of the random access preambles and the number of RACH subframes, we should configure the number of RACH subframes given the arrival rate in order to gua...

New features are often added incrementally to avionics systems. This avoids redesign and recertification but still requires verifying the timing constraints of both new and existing applications. We introduce a new switch that facilitates this verification by bounding the latency of end-to-end communication across a network. Our clock-driven real-t...

We propose an adaptive carrier sense (CS) scheme with enhanced fairness based on an observation that the conventional adaptive CS mechanism may lead to significant unfairness. Our experimental study with an IEEE 802.15.4 WPAN testbed shows that the proposed algorithm significantly improves fairness compared to the conventional mechanism while provi...