研發無線感測網路用於居家健康照護

Abstract

無線感測網路尚未廣泛地應用於居家健康照護服務上，大多數在健康照護相關方面的研究都只著重於點對點的傳輸，而沒有採取網路的架構。如此，將會使系統的擴充性受到限制。然而少數具有使用網路架構的研究大都採用藍芽的無線傳輸技術，藍芽是無線個人區域網路的標準之一，其Piconet網路最多只容許八個裝置加入，網路定址能力將受到限制。為了實現無線感測網路，使其具有高度網路定址能力，本研究透過ZigBee發展無線感測網路。ZigBee為無線個人區域網路，其建構在IEEE 802.15.4 的標準之上，具低功率消耗，高度網路定址能力的優點。 本研究所實現之居家健康照護系統是由多個無線生理信號感測器、路由器與個人區域網路仲裁器所組成的。開發此系統之硬體平台包含了一個微控制器 (MSP430F1611, TI, USA) 與ZigBee 射頻晶片(UZ2400, UBEC, Taiwan)。本研究已完成ZigBee網路層之開發，並建構無線感測網路為一個樹狀三階層式之架構。透過無線生理感測器量測病人之心電圖與血氧濃度傳送至路由器；路由器負責分配每個無線感測器可擁有的傳送時間，使用階層式的路由方式將封包傳送給個人區域網路仲裁器。個人區域網路仲裁器接收路由器傳送之封包並取出生理信號資料，以RS232傳送至個人電腦。 居家健康照護上常伴隨大量生理信號的處理，由於無線感測網路在管理與控制會面臨棘手的問題，例如感測裝置如何做有效的管理及資料時效性的問題, 因此本研究採用web-based 的管理方式，並結合web 2.0的概念, 使生理信號圖形能夠流暢地顯示於網頁上。其技術主要結合非同步Java描述語言、可延伸性標示語言、可縮放向量圖形與資料庫，具有跨平台、不受空間限制與整合性等優點。 本研究已建構完具有遠端監控與管理能力之無線感測網路系統，其優點為具有高定址能力、低功率消耗、快速反應時間。將本研究應用於居家健康照護系統上，可讓病人在家裡就可以透過此系統讓醫生即時監看居家病人的健康情形，但是在病人隱私權上面卻是相當有道德爭議，未來居家健康照護系統須加強資料安全以保護病人隱私。

The Wireless Sensor Network (WSN) is an underdeveloped area today in the health-care service industry. Many studies in health-care issues focus on implementation of peer-to-peer communication without network topology, which refers to the extension of system limits. Furthermore, most studies adopt Bluetooth, which is a wireless standard for the Wireless Personal Area Network (WPAN). Bluetooth has limited addressing capability; a Piconet of Bluetooth contains eights devices at most. For the above reasons this study uses ZigBee, a wireless standard based on IEEE 802.15.4, which is a WPAN with low power consumption and high addressing capability. The home-care system proposed in this study consists of sensor devices, a router, Personal Area Network (PAN) coordinators and a remote database server. The sensor device, router and PAN coordinator are all developed on the ZigBee module, which consists of a micro-controller (MCU; MSP430F1611, TI, USA) and a ZigBee RF chip (UZ2400, UBEC, Taiwan). Furthermore, the ZigBee network (NWK) layer and application (APP) layer are built on MCU for a WSN with three-level topology. For the sensor devices, physiological signals of the electrocardiogram (ECG) and (Oxygen Saturation) SpO2 are measured from patients and then transmitted to the router. The router is responsible for scheduling a sending time for each associated device and using hierarchical routing to forward data to a specific device. On the PAN coordinator side, data is extracted from received packages and then passed to the personal computer through RS232. Due to the large number of sensor devices in the WSN, management and querying present a number of problems. In this study a web-based management method is used to manage physiological information in the WSN. To display physiological signals on the web interface smoothly and rapidly, the latest design of web 2.0, which contains Ajax (Asynchronous Java Script + XML) and Scalable Vector Graphing (SVG), is adopted. This is a high-performance web based technology that is cross-platform, has no limitations of space and integrates the WSN and database servers. The WSN with web-based management has been implemented successfully with many advantages, including higher addressing capability, lower power consumption, and reduced waking time. The system proposed in this study has the potential to bring healthcare out of the hospital and into the patient’s home, replace nurses with sensor devices, and collect sensitive information. This will create many ethical considerations, which must be dealt with in order to ensure that any changes made in the health-care industry are for the good of the patients.