A low power medium access control protocol for wireless medical sensor networks

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A Low Power Medium Access Control Protocol for Wireless Medical Sensor Networks I. E. Lamprinos1, A. Prentza1, E. Sakka1, D. Koutsouris1

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Biomedical Engineering Laboratory, School of Electrical and Computer Engineering, National Technical University of Athens, Greece

Abstract—The concept of a wireless integrated network of sensors, already applied in several sectors of our everyday life, such as security, transportation and environment monitoring, can as well provide an advanced monitor and control resource for healthcare services. By networking medical sensors wirelessly, attaching them in patient’s body, we create the appropriate infrastructure for continuous and real-time monitoring of patient without discomforting him. This infrastructure can improve healthcare by providing the means for flexible acquisition of vital signs, while at the same time it provides more convenience to the patient. Given the type of wireless network, traditional Medium Access Control (MAC) protocols cannot take advantage of the application specific requirements and information characteristics occurring in medical sensor networks, such as the demand for low power consumption and the rather limited and asymmetric data traffic. In this paper, we present the architecture of a low power MAC protocol, designated to support wireless networks of medical sensors. This protocol aims to improve energy efficiency by exploiting the inherent application features and requirements. It is oriented towards the avoidance of main energy wastage sources, such as idle listening, collision and power outspending. Keywords—Energy efficiency, MAC protocol, medical sensor networks, telemedicine

I. INTRODUCTION Recent advances in sensor technology, low power analog and digital electronics and low-power radio frequency design have enabled the development of miniature, low-power sensor nodes, integrating sensing, processing and wireless communication capabilities [1-2]. Significant aspects of this evolution are remote patient monitoring and remote guidance and consultation. For this to happen, a Personal Area Network (PAN) infrastructure is formed in the body of the patient [3-4]. This infrastructure provides the capability of continuous vital signs monitoring and control of several operations, through data exchange between medical sensors and the healthcare provider. The patient’s PAN consists of several medical sensor nodes (i.e. ECG, pulse oximetry, blood pressure and body temperature), placed in relatively short distance between them and an intermediate, supervisor node, residing with the patient and being responsible for the local administration of the wireless network and communication with the monitoring facility. This type of wireless sensor networks has unique characteristics, which differentiate it from traditional ad hoc wireless networks. As the nodes of the network are attached in the patient’s body, the distance between them does not

exceed 1-1.5m. Moreover, medical sensors have limited processing power, memory and energy available. Actually, the demand for small, often miniature medical sensors size imposes the use of respectively small batteries. In many cases these sensors are used to support telemedicine services which rather than offering continuous patient monitoring, they are oriented towards occasional data transmission, according to specific criteria, set by the healthcare provider. This factor makes data traffic rather sporadic. The nature of these services does not necessitate for high data rate (