JeongGil Ko

Wireless Sensor Networks for Healthcare

Driven by the confluence between the need to collect data about peoples physical, physiological, psychological, cognitive, and behavioral processes in spaces ranging from personal to urban and the recent availability of the technologies that enable this data collection, wireless sensor networks for healthcare have emerged in the recent years. In this review, we present some representative applications in the healthcare domain and describe the challenges they introduce to wireless sensor networks due to the required level of trustworthiness and the need to ensure the privacy and security of medical data. These challenges are exacerbated by the resource scarcity that is inherent with wireless sensor network platforms. We outline prototype systems spanning application domains from physiological and activity monitoring to large-scale physiological and behavioral studies and emphasize ongoing research challenges.

Wireless Medical Sensor Networks in Emergency Response: Implementation and Pilot Results

This project demonstrates the feasibility of using cost- effective, flexible, and scalable sensor networks to address critical bottlenecks of the emergency response process. For years, emergency medical service providers conducted patient care by manually measuring vital signs, documenting assessments on paper, and communicating over handheld radios. When disasters occurred, the large numbers of casualties quickly and easily overwhelmed the responders. Collaboration with EMS and hospitals in the Baltimore Washington Metropolitan region prompted us to develop miTag (medical information tag), a cost- effective wireless sensor platform that automatically track patients throughout each step of the disaster response process, from disaster scenes, to ambulances, to hospitals. The miTag is a highly extensible platform that supports a variety of sensor add-ons - GPS, pulse oximetry, blood pressure, temperature, ECG - and relays data over a self-organizing wireless mesh network Scalability is the distinguishing characteristic of miTag: its wireless network scales across a wide range of network densities, from sparse hospital network deployments to very densely populated mass casualty sites. The miTag system is out-of-the-box operational and includes the following key technologies: 1) cost-effective sensor hardware, 2) self-organizing wireless network and 3) scalable server software that analyzes sensor data and delivers real-time updates to handheld devices and web portals. The system has evolved through multiple iterations of development and pilot deployments to become an effective patient monitoring solution. A pilot conducted with the Department of Homeland Security indicates miTags can increase the patient care capacity of responders in the field A pilot at Washington Hospital showed miTags are capable of reliably transmitting data inside radio-interference-rich critical care settings.

Connecting low-power and lossy networks to the internet

Many applications, ranging from wireless healthcare to energy metering on the smart grid, have emerged from a decade of research in wireless sensor networks. However, the lack of an IP-based network architecture precluded sensor networks from interoperating with the Internet, limiting their real-world impact. Given this disconnect, the IETF chartered the 6LoWPAN and RoLL working groups to specify standards at various layers of the protocol stack with the goal of connecting low-power and lossy networks to the Internet. We present the standards proposed by these working groups, and describe how the research community actively participates in this process by influencing their design and providing open source implementations.

Empirical study of a medical sensor application in an urban emergency department

User needs and technology availability drive the introduction of wireless sensing applications in clinical environments. While these applications have the potential to improve efficiency and quality of care, very little is known about their performance during day-to-day use at the hospital. In this work, we use data from a deployment of a 802.15.4-based wireless sensor network at the Emergency Room of the Johns Hopkins hospital to answer these questions. Specifically, over a period of ten days we deployed a system of wireless vital signs monitors that measure the heart rate and blood oxygen levels of Emergency Room patients. During this time we collected statistics about the networks RF links, the performance of its tree routing protocol, and its end-to-end reliability. We find that the hospital environment we tested has considerably higher radio noise levels across multiple frequency channels and more bursty links compared to other indoor environments. Nonetheless, the routing protocol we use finds high quality links and the end-to-end packet reception ratio is above 99.9%. Taken as a whole, these preliminary results suggest that despite the challenges that clinical environments pose, wireless medical sensing applications can perform well in these conditions.

Performance Evaluation of IEEE 802.15.4 MAC with Different Backoff Ranges in Wireless Sensor Networks

The IEEE 802.15.4 MAC (medium access control) is a protocol used in many applications including the wireless sensor network. Yet the IEEE 802.15.4 MAC layer cannot support different throughput performance for individual nodes with the current specifications. However, if certain nodes are sending data more frequently compared to others, with the standard MAC, it is hard to achieve network efficiency. Therefore, we modified the IEEE 802.15.4 MAC and additionally proposed a new state transition scheme. By adjusting the minBE value of some nodes to a smaller value and by dynamically changing the value depending on the transmission conditions, we shortened the backoff delay of nodes with frequent transmission. It was observed through our simulations that the throughput of the node with a lower minBE value increased significantly, compared to nodes with the original BE range of 3 to 5. Also by the use of the state transition scheme the total network efficiency increased leading to increase in throughput performance

Industry: beyond interoperability: pushing the performance of sensor network IP stacks

Interoperability is essential for the commercial adoption of wireless sensor networks. However, existing sensor network architectures have been developed in isolation and thus interoperability has not been a concern. Recently, IP has been proposed as a solution to the interoperability problem of low-power and lossy networks (LLNs), considering its open and standards-based architecture at the network, transport, and application layers. We present two complete and interoperable implementations of the IPv6 protocol stack for LLNs, one for Contiki and one for TinyOS, and show that the cost of interoperability is low: their performance and overhead is on par with state-of-the-art protocol stacks custom built for the two platforms. At the same time, extensive testbed results show that the ensemble performance of a mixed network with nodes running the two interoperable stacks depends heavily on implementation decisions and parameters set at multiple protocol layers. In turn, these results argue that the current industry practice of interoperability testing does not cover the crucial topic of the performance and motivate the need for generic techniques that quantify the performance of such networks and configure their run-time behavior.

Wireless Sensing Systems in Clinical Environments: Improving the Efficiency of the Patient Monitoring Process

Multiple studies suggest that the level of patient care may decline in the future because of a larger aging population and medical staff shortages. Wireless sensing systems that automate some of the patient monitoring tasks can potentially improve the efficiency of patient workflows, but their efficacy in clinical settings is an open question. This article examines the potential of wireless sensor network (WSN) technologies to improve the efficiency of the patient-monitoring process in clinical environments. MEDiSN, a WSN designed to continuously monitor the vital signs of ambulatory patients, is designed. The usefulness of MEDiSN is validated with test bed experiments and results from a pilot study performed at the Emergency Department, Johns Hopkins Hospital. Promising results indicate that MEDiSN can tolerate high degrees of human mobility, is well received by patients and staff members, and performs well in real clinical environments.

MoMoRo: Providing Mobility Support for Low-Power Wireless Applications

Recently, mobile devices have been introduced in various wireless sensor network (WSN) applications in order to solve complex tasks or to increase the data collection efficiency. However, the current generation of low-power WSN protocols is mainly designed to support data collection and address application-specific challenges without any particular considerations for mobility. In this paper, we introduce MoMoRo, a mobility support layer that can be easily applied to existing data collection protocols, thereby enabling mobility support in the network. MoMoRo robustly collects neighborhood information and uses a fuzzy estimator to make link quality estimations. This fuzzy estimator continuously reconfigures its thresholds for determining the fuzzy sets, allowing MoMoRo to easily adapt to changing channel environments. Furthermore, MoMoRo includes an active destination search scheme that allows disconnected mobile nodes with sparse traffic to quickly reconnect if there are packets in the network destined to this mobile node. We evaluate MoMoRo both indoor and outdoor and show that a continuously moving device in a MoMoRo-enabled RPL (i.e., IPv6 Routing Protocol for Low-Power and Lossy Networks) network can achieve a high packet reception ratio of up to 96% and stay connected in areas where RPL alone cannot and with less than half the packet overhead needed by the well-known Ad hoc On-Demand Distance Vector routing protocol.

DualMOP-RPL: Supporting Multiple Modes of Downward Routing in a Single RPL Network

RPL is an IPv6 routing protocol for low-power and lossy networks (LLNs) designed to meet the requirements of a wide range of LLN applications including smart grid AMIs, home and building automation, industrial and environmental monitoring, health care, wireless sensor networks, and the Internet of Things (IoT) in general with thousands and millions of nodes interconnected through multihop mesh networks. RPL constructs tree-like routing topology rooted at an LLN border router (LBR) and supports bidirectional IPv6 communication to and from the mesh devices by providing both upward and downward routing over the routing tree. In this article, we focus on the interoperability of downward routing and supporting its two modes of operations (MOPs) defined in the RPL standard (RFC 6550). Specifically, we show that there exists a serious connectivity problem in RPL protocol when two MOPs are mixed within a single network, even for standard-compliant implementations, which may result in network partitions. To address this problem, this article proposes DualMOP-RPL, an enhanced version of RPL, which supports nodes with different MOPs for downward routing to communicate gracefully in a single RPL network while preserving the high bidirectional data delivery performance. DualMOP-RPL allows multiple overlapping RPL networks in the same geographical regions to cooperate as a single densely connected network even if those networks are using different MOPs. This will not only improve the link qualities and routing performances of the networks but also allow for network migrations and alternate routing in the case of LBR failures. We evaluate DualMOP-RPL through extensive simulations and testbed experiments and show that our proposal eliminates all the problems we have identified.

A Feasibility Study and Development Framework Design for Realizing Smartphone-Based Vehicular Networking Systems

Designing and distributing effective vehicular safety applications can help significantly reduce the number of car accidents and assure the safety of many precious lives. However, despite the efforts from standardization bodies and industrial manufacturers, many studies suggest that it will take more than a decade for full deployment. We start this work with the hypothesis that smartphones may be suitable platforms for catalyzing the distribution of vehicular safety systems. Specifically, smartphones connected to their respective cellular networks can report sensing data to back-end application servers and exchange safety-related messages. This paper first evaluates the performance of the vehicular ad-hoc networking standards and the hardware platforms that implement them. Next, we perform empirical evaluations on the performance of cellular networks to confirm their applicability in vehicular networking. Based on our observations, we present the VoCell application development framework. VoCell, comprehends a set of components that eases the development of smartphone applications for vehicular networking applications. Using VoCell, developers can easily access internal and external sensing components and share this data to servers. We present a number of example applications developed using VoCell and evaluate their effectiveness in local and highway environments using a pilot deployment. We envision that VoCell can act as a building block for enabling new smartphone-based systems for vehicular networking applications.