Wireless Sensor Networks and mHealth basics 2.

What standards, hardware and operating systems are  used for wireless sensor networks? There are three. I wrote some articles about ZigBee. It´s a proprietary mesh-networking specification intended for uses such as embedded sensing, medical data collection and home automation. WirelessHART is specifically designed for Industrial applications. 6LoWPAN is the IETF standards track specification. Also relevant to sensor networks is the emerging IEEE 1451 which attempts to create standards for the smart sensor market. The main point of smart sensors is to move the processing intelligence closer to the sensing device.

Hardware

The main challenge is to produce low cost and tiny sensor nodes. With respect to these objectives, current sensor nodes are mainly prototypes. Miniaturization and low cost are understood to follow from recent and future progress. Some of the existing sensor nodes are given below. Some of the nodes are still in research stage. Also inherent to sensor network adoption is the availability of a very low power method for acquiring sensor data wirelessly.

Operating systems

Operating systems for wireless sensor network nodes are typically less complex than general-purpose operating systems both because of the special requirements of sensor network applications and because of the resource constraints in sensor network hardware platforms. Wireless sensor network hardware is not different from traditional embedded systems and it is therefore possible to use embedded operating systems such as eCos or uC/OS for sensor networks. However, such operating systems are often designed with real-time properties. Unlike traditional embedded operating systems, however, operating systems specifically targeting sensor networks often do not have real-time support.

TinyOS is perhaps the first operating system specifically designed for wireless sensor networks. Unlike most other operating systems, TinyOS is based on an event-driven programming model instead of multithreading. TinyOS programs are composed into event handlers and tasks with run to completion-semantics. When an external event occurs, such as an incoming data packet or a sensor reading, TinyOS calls the appropriate event handler to handle the event. Event handlers can post tasks that are scheduled by the TinyOS kernel some time later. Both the TinyOS system and programs written for TinyOS are written in a special programming language called nesC which is an extension to the C programming language.

There are also operating systems that allow programming in C. Examples of such operating systems include Contiki, MANTIS, BTnut, SOS and Nano-RK. LiteOS is a newly developed OS for wireless sensor networks, which provides UNIX like abstraction and support for C programming language.