高信頼ミリ波帯 WBAN の研究

Tohoku University末松憲治課

Requirements for Designing a Wearable Smart Blanket System for Monitoring Patients in Ambulance

Introduction: Nowadays, smart systems and advanced tools such as wearable systems have grown significantly in order to monitor patients and keep their condition under control. The aim of this study was to determine the requirements for designing a wearable smart blanket system (WSBS) to monitor patients in ambulance instantaneously. Method: After reviewing the characteristics of wearable systems by conducting a comparative study, the requirements for designing the proposed system were determined using appropriate data collection methods. In the first step, studies were conducted to identify the requirements for the development of wearable systems, and in the second step, a questionnaire obtained from the studies was distributed among specialists, and based on the results obtained from the questionnaire, the requirements for designing the system were determined. Results: Wearable Smart Blanket System (WSBS) has special functional features such as monitoring of vital signs, ability to communicate with the environment, instantaneous processing of vital signs, the ability to alert when vital signs exceed the threshold, and the ability to record all the patients' vital signs. The main non-functional features of WSBS include easy installation and operation, interoperability, error tolerance, low power consumption, accuracy of signs recording, data evaluation and analysis. Conclusion: The WSBS records all the vital signs needed for the control of patients seamlessly and provides interpreted data for the ambulatory treatment team. All patients' medical, diagnostic, and monitored health information are stored in the physician assistants' system, and therefore, allows them to provide early diagnosis

Energy Efficient Cooperative Communications for Wireless Body Area Networks

It is expected that Wireless Body Area Network (WBAN) will greatly improve the quality of our life because of its myriad applications for our human beings. However, one of the challenges is to design energy efficient communication protocols to support the reliable communication as well as to prolong the network lifetime. Cooperative communications have the advantage of spatial diversity to combat multipath fading, thus improving the link reliability and boosting energy efficiency. In this thesis, we investigate the energy efficient cooperative communications for WBAN. We first analyze the outage performance of three transmission schemes, namely direct transmission, single relay cooperation, and multi-relay cooperation. To minimize the energy consumption, we then study the problem of optimal power allocation with the constraint of targeted outage probability. Two strategies of power allocation are considered: power allocation with and without posture state information. Simulation results verify the accuracy of the analysis and demonstrate that: 1) power allocation making use of the posture information can reduce the energy consumption; 2) within a possible range of the channel quality in WBAN, cooperative communication is more energy efficient than direct transmission only when the path loss between the transmission pair is higher than a threshold; and 3) for most of the typical channel quality due to the fixed transceiver locations on human body, cooperative communication is effective in reducing energy consumption

Experimental investigation into novel methods of reliable and secure on-body communications with low system overheads

Until recently the concept of wearable biosensors for purposes of medical monitoring was restricted to wired sensor applications. Recent advances in electronics and wireless communications have made the possibility of removing the wire from sensor applications a possibility. These advances have led to the development of small scale, wearable, sensing and communication platforms that can be placed on the human body creating the foundation for a Body Sensor Network (BSN). Body Sensor Networks aim to remove the restrictions that traditional wired sensors impose. The anticipation is that BSNs will permit the monitoring of physiological signals in any environment without limitation, giving Physicians the ability to monitor patients more closely and in environments that they cannot monitor today. Even with the recent advancements of electronics and wireless communications there are still many unanswered questions for practical solutions of BSNs that prevent BSNs from replacing traditional wired systems altogether. There is a great need for research into BSN architectures to set the standard for wireless sensor monitoring. In this work a development platform has been created for the investigation into the design and implementation of practical BSN solutions. The platform is used to compare BSN architectures and provide quantifiable results. From this work BSN architecture components that provide optimizations in system performance, energy, network lifetime and security are recommended. In Chapter 3 BSN network architectures employing the use of relaying of creeping waves is investigated. The investigation includes experimental analysis of various test environments. Experimentation demonstrates that the relaying of creeping waves offers considerable performance gains when compared to non-relay networks. For example, relaying is shown to increase network-lifetime by a factor of 13, decrease energy-per-bit requirements by 13 dB and provide the ability for the network to compensate for considerably wider fade margins. In Chapter 4 utilizing the randomness of the wireless channel for securing on-body communications with low overheads is considered. A low-complexity algorithm for establishing symmetric encryption keys is presented and validated. The algorithm relies on readily available RSSI measurements obtained from existing packets being sent and received in the network. The generated bit sequences from the algorithm are evaluated for matching between two communicating parties and mismatching with a malicious eavesdropper. It is shown that the algorithm produces long sequences of highly random bits that are perfectly matched between legitimate parties and highly mismatched with the eavesdropper

A comprehensive review of wireless body area network

Recent development and advancement of information and communication technologies facilitate people in different dimensions of life. Most importantly, in the healthcare industry, this has become more and more involved with the information and communication technology-based services. One of the most important services is monitoring of remote patients, that enables the healthcare providers to observe, diagnose and prescribe the patients without being physically present. The advantage of miniaturization of sensor technologies gives the flexibility of installing in, on or off the body of patients, which is capable of forwarding physiological data wirelessly to remote servers. Such technology is named as Wireless Body Area Network (WBAN). In this paper, WBAN architecture, communication technologies for WBAN, challenges and different aspects of WBAN are illustrated. This paper also describes the architectural limitations of existing WBAN communication frameworks. blueFurthermore, implementation requirements are presented based on IEEE 802.15.6 standard. Finally, as a source of motivation towards future development of research incorporating Software Defined Networking (SDN), Energy Harvesting (EH) and Blockchain technology into WBAN are also provided

Desarrollo de una técnica de acoplamiento para aplicaciones en sistemas de comunicación a través del cuerpo humano

Esta tesis propone una nueva técnica para la comunicación a través del cuerpo humano (HBC) que utiliza el acoplamiento magnético en el transmisor y el receptor, denominada HBC de doble inductor. Se presenta una discusión sobre la presencia de caminos parásitos, cuando se usa acoplamiento magnético en el transmisor, y se usa acoplamiento eléctrico en el receptor; mostrando que la técnica aquí presentada reduce la influencia del ambiente circundante al mismo tiempo que simplifica los esquemas de recepción convencionales. También se observó que la técnica propuesta en distancias largas ( 30 cm) no tiene variaciones significativas en el canal de pérdidas. Además, se mostró que el movimiento del cuerpo no introduce perturbaciones o cambios significativos en la integridad de la señal transmitida mediante la técnica MHBC de doble inductor. Finalmente, se propone un modelo de circuito equivalente que describe adecuadamente el canal HBC para la técnica propuesta, obteniendo una desviación máxima de ± 2 dB al correlacionar el modelo con los resultados experimentales en el rango de frecuencia desde 5 MHz a 20 MHz.Abstract. This thesis proposes a new technique for Human Body Communication (HBC) that uses the magnetic coupling in transmitter and receiver, this is called double-inductor MHBC technique. A discussion about the presence of parasitic paths, when magnetic coupling is used in the transmitter, and electrical coupling is used in the receiver is presented; showing that the technique presented here, reduces the influence of the surrounding environment at the same time that simplifies the conventional reception schemes. Also, It was observed that the technique proposed in long distances (30 cm) does not have significant variations in the pathloss. In addition, it was appreciated that the movement of the body does not introduce significant changes in the integrity of the signal transmitted when the doubleinductor MHBC technique is used . Finally, an equivalent circuit model that characterizes the HBC channel for the proposed technique is proposed and it adequately describes the HBC channel for the proposed technique, it has a maximum deviation of ±2 dB when the model and experimental results are correlating in the frequency range from 5 MHz to 20 MHz.Maestrí

Reliable and Energy Efficient Network Protocols for Wireless Body Area Networks

In a wireless Body Area Network (WBAN) various sensors are attached on clothing, on the body or are even implanted under the skin. The wireless nature of the network and the wide variety of sensors offers numerous new, practical and innovative applications. A motivating example can be found in the world of health monitoring. The sensors of the WBAN measure for example the heartbeat, the body temperature or record a prolonged electrocardiogram. Using a WBAN, the patient experiences a greater physical mobility and is no longer compelled to stay in a hospital. A WBAN imposes the networks some strict and specific requirements. The devices are tiny, leaving only limited space for a battery. It is therefore of uttermost importance to restrict the energy consumption in the network. A possible solution is the development of energy efficient protocols that regulate the communication between the radios. Further, it is also important to consider the reliability of the communication. The data sent contains medical information and one has to make sure that it is correctly received at the personal device. It is not allowed that a critical message gets lost. In addition, a WBAN has to support the heterogeneity of its devices. This thesis focuses on the development of energy efficient and reliable network protocols for WBANs. Considered solutions are the use of multi-hop communication and the improved interaction between the different network layers. Mechanisms to reduce the energy consumption and to grade up the reliability of the communication are presented. In a first step, the physical layer of the communication near the human body is studied and investigated. The probability of a connection between two nodes on the body is modeled and used to investigate which network topologies can be considered as the most energy efficient and reliable. Next, MOFBAN, a lightweight framework for network architecture is presented. Finally, CICADA is presented: a new cross layer protocol for WBANs that both handles channel medium access and routing

Modeling and experimental performance analysis of ZigBee-IEEE 802.15.4 for wireless body area networks

Dissertação de mestrado integrado em Engenharia de ComunicaçõesThe emerging field of wireless body area networks (WBAN) has the potential to play an important role in everyday life, and there are many industries such as health, sports and entertainment that can take advantage of these networks. The wireless monitoring of users’ physical state, in indoor or outdoor environments, can bring benefits in several application scenarios; for example, it can increase patients’ general well-being and reduce caregivers’ workload by allowing continuous monitoring. This dissertation identifies and analyzes key performance aspects of using the ZigBee and IEEE 802.15.4 protocols in WBAN applications. The main reason behind this work is because these protocols were designed primarily for wireless sensor networks (WSNs) but are also being used in WBAN applications, particularly in the healthcare area. The differences between WSN and WBANs are explained and are used to discuss the usage of the ZigBee and the IEEE 802.15.4 standards in WBANs. The analysis performed in this work consists mainly in the execution of experimental tests with non-beacon enabled ZigBee/IEEE 802.15.4 networks, using widespread hardware and software platforms from Texas Instruments, regarding relevant quality of service (QoS) metrics (maximum throughput, delivery ratio and network delay), as well as the effects of multiple constraints, such as hidden nodes, clock drift and body interference in the network performance. A clock drift model was proposed to estimate when two nodes will interfere with each other. This model was conceived due to the lack of support from the ZigBee to overcome this issue. A solution to overcome the clock drift and the hidden node problems was then designed. A parametric software delay model of ZigBee network devices was also defined and introduced into a simulator so that more accurate simulation results could be obtained. The proposed models were deemed valid since they were thoroughly tested and the predicted results were obtained.As redes de sensores sem fios de área corporal (WBAN) têm o potencial de desempenhar um papel importante no dia-a-dia. Hoje em dia há muitas indústrias, tais como na área da saúde, do desporto e do entretenimento, que podem tirar proveito dessas redes. A monitorização sem fios de sinais fisiológicos, tanto em ambientes fechados como ao ar livre, pode trazer benefícios em vários cenários de aplicação, tais como, aumentar o bem-estar de pacientes que são monitorizados e reduzir a carga de trabalho de médicos, permitindo a monitorização contínua. Esta dissertação identifica e analisa aspetos chave do desempenho das redes ZigBee e IEEE 802.15.4, quando usadas em aplicações típicas das WBAN. A principal motivação para a realização deste trabalho reside no facto de que, apesar de terem sido projetados principalmente para redes de sensores sem fio (WSN), estes protocolos estão também a ser utilizados em aplicações características das WBAN, particularmente na área da saúde. As diferenças entre as WSN e as WBAN são destacadas e usadas para discutir o uso dos protocolos ZigBee e IEEE 802.15.4 nas WBAN. A análise realizada neste trabalho consiste, principalmente, na execução de testes experimentais de redes ZigBee/IEEE 802.15.4 a funcionar no modo non-beacon enabled, usando as plataformas de hardware e software da Texas Instruments. A análise leva em consideração métricas relevantes (o máximo goodput, a taxa de entrega e o atraso da rede) de qualidade de serviço (QoS) e os efeitos de várias condicionantes, como os nós escondidos, o clock drift e a interferência do corpo humano no desempenho da rede. Um modelo para o clock drift foi proposto para estimar quando dois dispositivos irão interferir um com o outro devido a este fenómeno. Este modelo foi concebido devido à falta de capacidade para o ZigBee superar este problema. Posteriormente foi concebida uma solução para ultrapassar os problemas associados ao clock drift e aos nós escondidos. Um modelo paramétrico de atrasos de software em dispositivos de redes ZigBee foi também definido e introduzido num simulador, de modo a que resultados de simulações mais precisos possam ser obtidos. Os modelos propostos foram considerados válidos dado que foram testados e os resultados previstos foram obtidos

A MAC protocol for quality of service provisioning in adaptive biomedical wireless sensor networks

Doctorate program on Electronics and Computer EngineeringNew healthcare solutions are being explored to improve the quality of care and the quality of life of patients, as well as the sustainability and efficiency of the healthcare services. In this context, wireless sensor networks (WSNs) constitute a key technology for closing the loop between patients and healthcare providers, as WSNs provide sensing ability, as well as mobility and portability, essential characteristics for wide acceptance of wireless healthcare technology. Despite the recent advances in the field, the wide adoption of healthcare WSNs is still conditioned by quality of service (QoS) issues, namely at the medium access control (MAC) level. MAC protocols currently available for WSNs are not able to provide the required QoS to healthcare applications in scenarios of medical emergency or intensive medical care. To cover this shortage, the present work introduces a MAC protocol with novel concepts to assure the required QoS regarding the data transmission robustness, packet delivery deadline, bandwidth efficiency, and energy preservation. The proposed MAC protocol provides a new and efficient dynamic reconfiguration mechanism, so that relevant operational parameters may be redefined dynamically in accordance with the patients’ clinical state. The protocol also provides a channel switching mechanism and the capacity of forwarding frames in two-tier network structures. To test the performance of the proposed MAC protocol and compare it with other MAC protocols, a simulation platform was implemented. In order to validate the simulation results, a physical testbed was implemented to replicate the tests and verify the results. Sensor nodes were specifically designed and assembled to implement this physical testbed. New healthcare solutions are being explored to improve the quality of care and the quality of life of patients, as well as the sustainability and efficiency of the healthcare services. In this context, wireless sensor networks (WSNs) constitute a key technology for closing the loop between patients and healthcare providers, as WSNs provide sensing ability, as well as mobility and portability, essential characteristics for wide acceptance of wireless healthcare technology. Despite the recent advances in the field, the wide adoption of healthcare WSNs is still conditioned by quality of service (QoS) issues, namely at the medium access control (MAC) level. MAC protocols currently available for WSNs are not able to provide the required QoS to healthcare applications in scenarios of medical emergency or intensive medical care. To cover this shortage, the present work introduces a MAC protocol with novel concepts to assure the required QoS regarding the data transmission robustness, packet delivery deadline, bandwidth efficiency, and energy preservation. The proposed MAC protocol provides a new and efficient dynamic reconfiguration mechanism, so that relevant operational parameters may be redefined dynamically in accordance with the patients’ clinical state. The protocol also provides a channel switching mechanism and the capacity of forwarding frames in two-tier network structures. To test the performance of the proposed MAC protocol and compare it with other MAC protocols, a simulation platform was implemented. In order to validate the simulation results, a physical testbed was implemented to replicate the tests and verify the results. Sensor nodes were specifically designed and assembled to implement this physical testbed. Preliminary tests using the simulation and physical platforms showed that simulation results diverge significantly from reality, if the performance of the WSN software components is not considered. Therefore, a parametric model was developed to reflect the impact of this aspect on a physical WSN. Simulation tests using the parametric model revealed that the results match satisfactorily those obtained in reality. After validating the simulation platform, comparative tests against IEEE 802.15.4, a prominent standard used in many wireless healthcare systems, showed that the proposed MAC protocol leads to a performance increase regarding diverse QoS metrics, such as packet loss and bandwidth efficiency, as well as scalability, adaptability, and power consumption. In this way, AR-MAC is a valuable contribution to the deployment of wireless e-health technology and related applications.Novas soluções de cuidados de saúde estão a ser exploradas para melhorar a qualidade de tratamento e a qualidade de vida dos pacientes, assim como a sustentabilidade e eficiência dos serviços de cuidado de saúde. Neste contexto, as redes de sensores sem fios (wireless sensor networks - WSN) são uma tecnologia chave para fecharem o ciclo entre os pacientes e os prestadores de cuidados de saúde, uma vez que as WSNs proporcionam não só capacidade sensorial mas também mobilidade e portabilidade, caracteristicas essenciais para a aceitação à larga escala da tecnologia dos cuidados de saúde sem fios. Apesar dos avanços recentes na área, a aceitação genérica das WSNs de cuidados de saúde ainda está condicionada por aspectos relacionados com a qualidade de serviço (quality of service - QoS), nomeadamente ao nível do controlo de acesso ao meio (medium access control - MAC). Os protocolos MAC actualmente disponíveis para WSNs são incapazes de fornecer a QoS desejada pelas aplicações médicas em cenários de emergência ou cuidados médicos intensivos. Para suprimir esta carência, o presente trabalho apresenta um protocolo MAC com novos conceitos a fim de assegurar a QoS respeitante à robustez de transmissão de dados, ao limite temporal da entrega de pacotes, à utilização da largura de banda e à preservação da energia eléctrica. O protocolo MAC proposto dispõe de um novo e eficiente mecanismo de reconfiguração para que os parâmetros operacionais relevantes possam ser redefinidos dinamicamente de acordo com o estado de saúde do paciente. O protocolo também oferece um mecanismo autónomo de comutação de canal, bem como a capacidade de encaminhar pacotes em redes de duas camadas. Para testar o desempenho do protocolo MAC proposto e compará-lo com outros protocolos MAC foi implementada uma plataforma de simulação. A fim de validar os resultados da simulação foi também implementada uma plataforma física para permitir replicar os testes e verificar os resultados. Esta plataforma física inclui nós sensoriais concebidos e construídos de raiz para o efeito. Testes preliminares usando as plataformas de simulação e física mostraram que os resultados de simulação divergem significativamente da realidade, caso o desempenho dos componentes do software presentes nos componentes da WSN não seja considerado. Por conseguinte, desenvolveu-se um modelo paramétrico para reflectir o impacto deste aspecto numa WSN real. Testes de simulação efectuados com o modelo paramétrico apresentaram resultados muito satisfatórios quando comparados com os obtidos na realidade. Uma vez validada a plataforma de simulação, efectuaram-se testes comparativos com a norma IEEE 802.15.4, proeminentemente usada em projectos académicos de cuidados de saúde sem fios. Os resultados mostraram que o protocolo MAC conduz a um desempenho superior no tocante a diversas métricas QoS, tais como perdas de pacotes e utilização de largura de banda, bem como no respeitante à escalabilidade, adaptabilidade e consumo de energia eléctrica. Assim sendo, o protocolo MAC proposto representa um valioso contributo para a concretização efectiva dos cuidados de saúde sem fios e suas aplicações