Robust medical ad hoc sensor networks (MASN) with wavelet-based ECG data mining

Heart disease is the top elder killer in the world. To reduce the healthcare cost, it is a necessary tendency to deploy self-organized, wireless heart disease monitoring hardware/software systems. Telemedicine platform based on ad hoc interconnection of tiny ECG sensors, called medical ad hoc sensor networks (MASN), can provide a promising approach for performing low-cost, real-time, remote cardiac patient monitoring at any time. The contribution of this research is the design of a practical MASN hardware/software platform to perform real-time healthcare data collections. It has reliable, cluster-based communication scheme. Due to the radio broadcasting nature of wireless networks, a MASN has the risk of being attacked. This research also designs a low overhead medical security scheme to achieve confidential ECG data transmission in the wireless medium. Finally, our MASN system has the capability of keeping track of cardiac patients and extracting ECG features based on wavelet theories. Our MASN platform is very useful to practical medical monitoring applications.     

A reliable transmission protocol for ZigBee-based wireless patient monitoring

Patient monitoring systems are gaining their importance as the fast-growing global elderly population increases demands for caretaking. These systems use wireless technologies to transmit vital signs for medical evaluation. In a multihop ZigBee network, the existing systems usually use broadcast or multicast schemes to increase the reliability of signals transmission; however, both the schemes lead to significantly higher network traffic and end-to-end transmission delay. In this paper, we present a reliable transmission protocol based on anycast routing for wireless patient monitoring. Our scheme automatically selects the closest data receiver in an anycast group as a destination to reduce the transmission latency as well as the control overhead. The new protocol also shortens the latency of path recovery by initiating route recovery from the intermediate routers of the original path. On the basis of a reliable transmission scheme, we implement a ZigBee device for fall monitoring, which integrates fall detection, indoor positioning, and ECG monitoring. When the triaxial accelerometer of the device detects a fall, the current position of the patient is transmitted to an emergency center through a ZigBee network. In order to clarify the situation of the fallen patient, 4-s ECG signals are also transmitted. Our transmission scheme ensures the successful transmission of these critical messages. The experimental results show that our scheme is fast and reliable. We also demonstrate that our devices can seamlessly integrate with the next generation technology of wireless wide area network, worldwide interoperability for microwave access, to achieve real-time patient monitoring.     

Strain-Isolating Materials and Interfacial Physics for Soft Wearable Bioelectronics and Wireless,Motion Artifact-Controlled Health Monitoring

Recent developments of micro-sensors and flexible electronics allow for the manufacturing of health monitoring devices, including electrocardiogram (ECG) detection systems for inpatient monitoring and ambulatory health diagnosis, by mounting the device on the chest. Although some commercial devices in reported articles show examples of a portable recording of ECG, they lose valuable data due to significant motion artifacts. Here, a new class of strain-isolating materials, hybrid interfacial physics, and soft material packaging for a strain-isolated, wearable soft bioelectronic system (SIS) is reported. The fundamental mechanism of sensor-embedded strain isolation is defined through a combination of analytical and computational studies and validated by dynamic experiments. Comprehensive research of hard-soft material integration and isolation mechanics provides critical design features to minimize motion artifacts that can occur during both mild and excessive daily activities. A wireless, fully integrated SIS that incorporates a breathable, perforated membrane can measure real-time, continuous physiological data, including high-quality ECG, heart rate, respiratory rate, and activities. In vivo demonstration with multiple subjects and simultaneous comparison with commercial devices captures the SIS's outstanding performance, offering real-world, continuous monitoring of the critical physiological signals with no data loss over eight consecutive hours in daily life, even with exaggerated body movements.     

Beat-based ECG compression using gain-shape vector quantization

An electrocardiogram (ECG) data compression scheme is presented using the gain-shape vector quantization. The proposed approach utilizes the fact that ECG signals generally show redundancy among adjacent heartbeats and adjacent samples. An ECG signal is QRS detected and segmented according to the detected fiducial points. The segmented heartbeats are vector quantized, and the residual signals are calculated and encoded using the AREA algorithm. The experimental results show that with the proposed method both visual quality and the objective quality are excellent even in low bit rates. An average PRD of 5.97% at 127 b/s is obtained for the entire 48 records in the MIT-BIH database. The proposed method also outperforms others for the same test dataset.     

Real-time processing of range-monitoring queries in heterogeneous mobile databases

Unlike conventional range queries, a range-monitoring query is a continuous query. It requires retrieving mobile objects inside a user-defined region and providing continuous updates as the objects move into and out of the region. In this paper, we present an efficient technique for real-time processing of such queries. In our approach, each mobile object is associated with a resident domain, and when an object moves, it monitors its spatial relationship with its resident domain and the monitoring areas inside it. An object reports its location to the server when it crosses over some query boundary or moves out of its resident domain. In the first case, the server updates the affected query results accordingly, while in the second case, the server determines a new resident domain for the object. This distributive approach achieves an accurate and real-time monitoring effect with minimal mobile communication and server processing costs. Our approach also allows a mobile object to negotiate a resident domain based on its computing capability. By having a larger resident domain, a more capable object has less of a chance of moving out of it and having to request a new one. As a result, both communication and server processing costs are reduced. Our comprehensive performance study shows that the proposed technique can be highly scalable in supporting location-based services in a wireless environment that consists of a large number of mobile devices.     

Compressed sensing for real-time energy-efficient ECG compression on wireless body sensor nodes

Wireless body sensor networks (WBSN) hold the promise to be a key enabling information and communications technology for next-generation patient-centric telecardiology or mobile cardiology solutions. Through enabling continuous remote cardiac monitoring, they have the potential to achieve improved personalization and quality of care, increased ability of prevention and early diagnosis, and enhanced patient autonomy, mobility, and safety. However, state-of-the-art WBSN-enabled ECG monitors still fall short of the required functionality, miniaturization, and energy efficiency. Among others, energy efficiency can be improved through embedded ECG compression, in order to reduce airtime over energy-hungry wireless links. In this paper, we quantify the potential of the emerging compressed sensing (CS) signal acquisition/compression paradigm for low-complexity energy-efficient ECG compression on the state-of-the-art Shimmer WBSN mote. Interestingly, our results show that CS represents a competitive alternative to state-of-the-art digital wavelet transform (DWT)-based ECG compression solutions in the context of WBSN-based ECG monitoring systems. More specifically, while expectedly exhibiting inferior compression performance than its DWT-based counterpart for a given reconstructed signal quality, its substantially lower complexity and CPU execution time enables it to ultimately outperform DWT-based ECG compression in terms of overall energy efficiency. CS-based ECG compression is accordingly shown to achieve a 37.1% extension in node lifetime relative to its DWT-based counterpart for "good" reconstruction quality.     

Privacy-preserving telecardiology sensor networks: toward a low-cost portable wireless hardware/software codesign.

Recently, a remote-sensing platform based on wireless interconnection of tiny ECG sensors called Telecardiology Sensor Networks (TSN) provided a promising approach to perform low-cost real-time cardiac patient monitoring at any time in community areas (such as elder nursing homes or hospitals). The contribution of this research is the design of a practical TSN hardware/software platform for a typical U.S. healthcare community scenario (such as large nursing homes with many elder patients) to perform real-time healthcare data collections. On the other hand, due to the radio broadcasting nature of MANET, a TSN has the risk of losing the privacy of patients' data. Medical privacy has been highly emphasized by U.S. Department of Health and Human Services. This research also designs a medical security scheme with low communication overhead to achieve confidential electrocardiogram data transmission in wireless medium.     

Secure and efficient scheme for fast initial link setup against key reinstallation attacks in IEEE 802.11ah networks

IEEE 802.11ah is a recently released IEEE standard to specify a wireless communication system with a long‐range, low‐power, and low data transmission rate over smart devices used in Internet of Things (IoT) systems. This new standard belongs to IEEE 802.11 wireless local area networks (WLANs) protocol family. It requires lightweight protocols to support the low‐power and low‐latency features of the IoT devices. On the other hand, an upcoming solution of fast initial link setup (FILS) specified by IEEE 802.11ai standard is a brand‐new approach aiming to establish fast and secure links among devices in WLANs to meet this new demand. It is natural and feasible to apply it to the 802.11ah networks to support massively deployed wireless nodes. However, security concerns on the link connection by the FILS scheme have not been fully eliminated, especially in the authentication process. It has been explored that a type of recently revealed malicious attack, key reinstallation attack (KRA) might be a threat to the FILS authentication. To prevent the success of the KRAs, in this paper, we proposed a secure and efficient FILS (SEF) protocol as the optional substitute of the FILS scheme. The SEF scheme is designed to eradicate potential threats from the KRAs without degrading the network performance.     

ECG/VCG rhythm diagnosis using statistical signal analysis--I. Identification of persistent rhythms

In this paper we describe a technique for detection and classification of cardiac arrhythmias for ECG or VCG data. The approach is based on the use of R-R interval data and the development of simple models that describe the sequential behavior of such intervals characteristic of different arrhythmias which persist over a period of about six or more heartbeats. In the second part of this two-paper series, we will deal with arrhythmias that manifest themselves as abrupt changes in the observed R-R intervals.     

A Distributed Virtual Backbone Development Scheme for Ad-Hoc Wireless Networks

The virtual backbone is an approach for solving routing problems in ad-hoc wireless networks. The virtual backbone approach features low latency, moderate routing overhead and is a hybrid scheme that uses the table-driven and on-demand routing protocols. This work presents a distributed virtual backbone development scheme for ad-hoc wireless networks. Using clustering, distributed labeling and heuristic Steiner tree techniques, our scheme outperforms other schemes in terms of the size and stability of the virtual backbone and the virtual backbone change rate. Experimental results demonstrate that our scheme has lower overhead than traditional table-driven and on-demand routing schemes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low‐cost wireless sensor networks for remote cardiac patients monitoring applications

One of today's most pressing matters in medical care is response time to patients in need. Scope of this research is to suggest a solution that would help reduce response time in emergency situations utilizing technologies of wireless sensor networks. The enhanced power efficiency, minimized production cost, condensed physical layout, and reduced wired connections present a much more proficient and simplified approach to the continuous monitoring of patients' physiological status. The proposed sensor network system is composed of wearable vital sign sensors and a workstation monitor. The wearable platforms are to be distributed to patients of concern. The wearable platforms can provide continuous electrocardiogram (ECG) monitoring by measuring electrical potentials between various points of the body using a galvanometer. They will then relay the ECG signals wirelessly to the workstation monitor. In addition to displaying the data, the workstation will also perform signal wavelet transformation for ECG characteristic extractions. Copyright © 2007 John Wiley & Sons, Ltd.     

Implementation of a WAP-based telemedicine system for patient monitoring

Many parties have already demonstrated telemedicine applications that use cellular phones and the Internet. A current trend in telecommunication is the convergence of wireless communication and computer network technologies, and the emergence of wireless application protocol (WAP) devices is an example. Since WAP will also be a common feature found in future mobile communication devices, it is worthwhile to investigate its use in telemedicine. This paper describes the implementation and experiences with a WAP-based telemedicine system for patient-monitoring that has been developed in our laboratory. It utilizes WAP devices as mobile access terminals for general inquiry and patient-monitoring services. Authorized users can browse the patients' general data, monitored blood pressure (BP), and electrocardiogram (ECG) on WAP devices in store-and-forward mode. The applications, written in wireless markup language (WML), WMLScript, and Perl, resided in a content server. A MySQL relational database system was set up to store the BP readings, ECG data, patient records, clinic and hospital information, and doctors' appointments with patients. A wireless ECG subsystem was built for recording ambulatory ECG in an indoor environment and for storing ECG data into the database. For testing, a WAP phone compliant with WAP 1.1 was used at GSM 1800 MHz by circuit-switched data (CSD) to connect to the content server through a WAP gateway, which was provided by a mobile phone service provider in Hong Kong. Data were successfully retrieved from the database and displayed on the WAP phone. The system shows how WAP can be feasible in remote patient-monitoring and patient data retrieval.     

Novel methods of faster cardiovascular diagnosis in wireless telecardiology

With the rapid development wireless technologies, mobile phones are gaining acceptance to become an effective tool for cardiovascular monitoring. However, existing technologies have limitations in terms of efficient transmission of compressed ECG over text messaging communications like SMS and MMS. In this paper, we first propose an ECG compression algorithm which allows lossless transmission of compressed ECG over bandwidth constrained wireless link. Then, we propose several algorithms for cardiovascular abnormality detection directly from the compressed ECG maintaining end to end security, patient privacy while offering the benefits of faster diagnosis. Next, we show that our mobile phone based cardiovascular monitoring solution is capable of harnessing up to 6.72 times faster diagnosis compared to existing technologies. As the decompression time on a doctor?s mobile phone could be significant, our method will be highly advantageous in patient wellness monitoring system where a doctor has to read and diagnose from compressed ECGs of several patients assigned to him. Finally, we successfully implemented the prototype system by establishing mobile phone based cardiovascular patient monitoring.     

Resource Allocation for Aggregate Multimedia and Healthcare Services over Heterogeneous Multi-Hop Wireless Networks

Nowadays, the pervasive wireless networks enable ubiquitous high-rate wireless access from everywhere. In this work, we discuss the integration of complementary wireless techniques to construct a personal moving network. The personal wireless devices (  smartphones, camcorders, and netbooks) and even medical monitoring sensors are interconnected with a wide-area backbone through a local multi-mode gateway. The mobile nodes in a personal moving network move in group and are provided seamless connectivity through a backhaul relay channel from the local gateway toward the backbone network. In some specific scenarios, the local gateway can be as simple as a multi-radio smartphone. In this study, we investigate the construction and resource allocation for a personal moving network. Aggregate multi-service traffic of interactive data, conversational video, and electrocardiography (ECG) monitoring are considered in the resource allocation. We develop a stochastic Petri net to model the access selection scheme, which is logically clear and easy to follow. The flow-level performance is evaluated in terms of new connection blocking probability and handoff dropping probability. We further analyze the packet-level performance of the heterogeneous two-hop network. Considering the urgency of medical services, a non-preemptive priority policy is applied to mitigate the impact of background traffic and prioritize the transmission of ECG data.     

一种鲁棒的无线传感器网络用户认证方案安全性的增强

In order to remedy the security weaknesses of a robust user authentication framework for wireless sensor networks, an enhanced user authentication framework is presented. The enhanced scheme requires proof of the possession of both a password and a smart card, and provides more security guarantees in two aspects: 1) it addresses the untraceability property so that any third party accessing the communication channel cannot link two authentication sessions originated from the same user, and 2) the use of a smart card prevents offline attacks to guess passwords. The security and efficiency analyses indicate that our enhanced scheme provides the highest level of security at reasonable computational costs. Therefore, it is a practical authentication scheme with attractive security features for wireless sensor networks.     

A secure mobile healthcare system using trust-based multicast scheme

Due to the introduction of telecommunication technologies in telemedicine services, the expeditious development of wireless and mobile networks has stimulated wide applications of mobile electronic healthcare systems. However, security is an essential system requirement since many patients have privacy concerns when it comes to releasing their personal information over the open wireless channels. For this reason, this study discusses the characteristics and security issues with wireless and pervasive data communications for a ubiquitous and mobile healthcare system which consists of a number of mobile devices and sensors attached to a patient. These devices form a mobile ad hoc sensor network and collect data that are sent to a hospital or healthcare center for monitoring. Subsequently, this paper discusses the innovation and design of a novel trust evaluation model. We then propose a secure multicast strategy that employs trust in order to evaluate the behavior of each node, so that only trustworthy nodes are allowed to participate in communications, while the misbehavior of malicious nodes is effectively prevented. We analyze the security properties of our multicast scheme and evaluate its performance based on simulation experiments. Our experimental results demonstrate that our scheme not only achieves the necessary data transmission in mobile environments, but also provides more security with reasonably little additional overhead.     

Timed strategic machine type communications for dual-level future wireless networks

For the next generation wireless networks, machine type communication (MTC) is gaining an enormous interest as a new communication paradigm. MTC is expected to become a cost-effective solution for improving the wireless communication performance. In MTC, one of the most critical issues is to support data transfers among devices without human interaction. In this study, we introduce a new MTC control scheme for the future network infrastructure. To effectively support a large number of MTC devices, we investigate a dual-level interaction mechanism by employing the timed strategy game model. In dynamic wireless network environments, our timed strategic game approach can practically adapt current system conditions while maximizing system performance. Main contribution of this research is to show a way of MTC system modeling based on the competitive and cooperative manner. Finally, numerical simulations illustrate the validity of our game-based approach. Our solution enables a better network resource utilization for heterogeneous traffic services in contrast to existing schemes.

     

Transmission Power Control in Body Area Sensor Networks for Healthcare Monitoring

This paper investigates the opportunities and challenges in the use of dynamic radio transmit power control for prolonging the lifetime of body-wearable sensor devices used in continuous health monitoring. We first present extensive empirical evidence that the wireless link quality can change rapidly in body area networks, and a fixed transmit power results in either wasted energy (when the link is good) or low reliability (when the link is bad). We quantify the potential gains of dynamic power control in body-worn devices by benchmarking off-line the energy savings achievable for a given level of reliability.We then propose a class of schemes feasible for practical implementation that adapt transmit power in real-time based on feedback information from the receiver. We profile their performance against the offline benchmark, and provide guidelines on how the parameters can be tuned to achieve the desired trade-off between energy savings and reliability within the chosen operating environment. Finally, we implement and profile our scheme on a MicaZ mote based platform, and also report preliminary results from the ultra-low-power integrated healthcare monitoring platform we are developing at Toumaz Technology.     

Weighted conditional random fields for supervised interpatient heartbeat classification

This paper proposes a method for the automatic classification of heartbeats in an ECG signal. Since this task has specific characteristics such as time dependences between observations and a strong class unbalance, a specific classifier is proposed and evaluated on real ECG signals from the MIT arrhythmia database. This classifier is a weighted variant of the conditional random fields classifier. Experiments show that the proposed method outperforms previously reported heartbeat classification methods, especially for the pathological heartbeats.