LQER: A Link Quality Estimation based Routing for Wireless Sensor Networks

Routing protocols are crucial to self-organize wireless sensor networks (WSNs), which have been widely studied in recent years. For some specific applications, both energy aware and reliable data transmission need to be considered together. Historical link status should be captured and taken into account in making data forwarding decisions to achieve the data reliability and energy efficiency tradeoff. In this paper, a dynamic window concept (m, k) is presented to record the link historical information and a link quality estimation based routing protocol (LQER) are proposed, which integrates the approach of minimum hop field and (m, k). The performance of LQER is evaluated by extensive simulation experiments to be more energy-aware, with lower loss rate and better scalability than MHFR [1] and MCR [2]. Thus the WSNs with LQER get longer lifetime of networks and better link quality.

A TELE-EMERGENT SYSTEM FOR LONG-TERM ECG MONITORING OVER WIRELESS SENSOR NETWORK

This paper presents the design and implementation of a tele-emergent system to provide constant monitoring of cardiac patients. Our system is consisted of a user integration device attached to the patient, a wireless sensor network (WSN) and a medical gateway installed in the patient's home, and a server set up in the hospital. The user integration device includes Electrocardiogram (ECG) signal acquisition and processing circuit utilizing a "Modified So and Chan" QRS detection algorithm to discriminate the R signal wave and calculate RR intervals to subsequently detect abnormal Heart Rate Variability (HRV), and a Bluetooth transmission module to communicate with WSN. The WSN which is consisted of wireless sensor nodes with power-saving scheme is used to relay the ECG data to the medical gateway for ubiquitous monitoring at home. The medical gateway includes the heart disease symptom recognition system to further analyze the ECG data and recognize the symptoms of serious heart diseases, and a General Packet Radio Service (GPRS) module with Multimedia Messaging Service (MMS) to communicate with the server in the hospital. The server in the hospital can passively process the MMS messages from the medical gateway, and actively send commands to the medical gateway to acquire the needed ECG data from the patient. With our integrated system it is possible to provide real-time and long-term monitoring of physiological data for cardiac patients which is vital for the patients' medical care.

A study of energy consumption and reliability in a multi-hop sensor network

For a moderate-size, multi-hop, sensor network, we present experimental measurements of radio energy consumption and packet reliability. We categorize the energy measurements by energy consumed in each radio state and for each traffic type. Packet reliability results are presented from a network and link perspective, whereas prior work only considered the former. We introduce a novel technique of application-aware radio duty cycling called on-demand spatial TDMA. When compared to the non-cycling case, this technique can achieve greater than an order of magnitude reduction in idle energy consumption, while not sacrificing reliability. We show end-to-end packet loss rates as low as 0.04 when averaged over the network. Even with substantial idle energy savings, we identify radio idling as the dominate energy consumer and overhearing as the dominate traffic type.

Wireless sensor networks

Wireless sensor networks (WSNs) consist of large populations of wirelessly connected nodes, capable of computation, communication, and sensing. Sensor nodes cooperate in order to merge individual sensor readings into a high-level sensing result, such as integrating a time series of position measurements into a velocity estimate. The physical time of sensor readings is a key element in this process called data fusion. Hence, time synchronization is a crucial component of WSNs. We argue that time synchronization schemes developed for traditional networks such as NTP [23] are ill-suited for WSNs and suggest more appropriate approaches.