Anatomy of RTOS and Analyze the Best-Fit for Small, Medium and Large Footprint Embedded Devices in Wireless Sensor Network

A wireless sensor network is characterized as a massively distributed and deeply embedded system with small medium and large footprint embedded devices. The sensor devices and wireless sensor nodes are often severely resource constrained. Typical they are equipped with 8-bit MCU, 100-512KB code memory and 4-64KB of RAM. Background / foreground approach, finite state machine based software design and event-driven programming techniques are capable of handling concurrent and asynchronous events usually occur in these devices. But network routers and coordinators are often medium and large footprint devices, equipped with 16/32-bit MCU, 640 KB-64 MB code memory and more RAM where real-time operating system is easier to implement. For a wireless sensor network design choosing and deciding a suitable lightweight real-time operating system and OS abstractions that provide a rich enough execution environment while staying within the limitations of the constrained devices is a great challenge. This paper presents several RTOS architectures and analyzes the best-fit for sensors and other wireless network devices.