WSN's and Fault Tolerance, a glimpse

In the upcoming age of the next generation internet, Wireless Sensor Networks are something with the potential to seriously influence the way we perceive the universe. With connectivity to the Internet of Things, WSN's can help us predict and monitor events from a remote locations. at various degrees of autonomy these WSN's pose interesting challenges in terms of routing algorithm design, protocols, network topology and even the core design of the sensor nodes themselves.

A major concern in WSN design is fault tolerance. WSN nodes may deployed in obscure locations and are generally not touched for months maybe even years. In such a case fault tolerance within the network is an important design parameter. A case in point is the WSN deployment in the Swiss Alps, where a fault manifested in the network in the form of clock drift at dawn and dusk, leading to loss of synchronization.

Talking about Fault Tolerance, I read a paper titled "A Two-Tier Data Dissemination Model for Large-scale Wireless Sensor Networks ". This paper talks about a data dissemination technique for efficient routing in large scale Wireless Sensor Networks. It also handles mobile data sinks as long as the source of data is static. Basically a virtual grid is set up by the source within the WSN and queries and responses travel along this grid.

A small issue with this method was that it proposes only one "upstream node" for every node, hence a unique path from the source to every node in the grid. Hence when a node fails, or a cluster of nodes fails, we might have to set up a major portion of the grid leading to increased traffic in the network. I studied this paper as a part of the "Embedded Systems Design" course, (Anyone from BITS Pilani will know exactly what I am talking about :P). As a solution I thought of using priority queuing and storing alternate redundant paths from the source to every node in the grid. This will not require the added cost involved with centralization in the network but at the same time will introduce fault tolerance in the sense that a path with lesser priority can be used in case of a fault.

The ideas that went into this are presented here in the form of a paper. We haven't yet implemented these ideas in simulation or otherwise, but I would really appreciate anyone's views on these before I implement the same.

A walk down the field, and along memory lane

I blogged (about a year ago :P) about work at CEERI Pilani, India.

Here is a follow up to that. It was a genuine dream to build a farm robot, I believed that it could actually contribute to a country like India. Moreover it is a serious technical challenge to any engineer, and brings to the forefront some very tough problems in embedded systems, computer vision, robotics and control theory. My continuing obsession with the "3 C's" has always kept me revisiting these problems sometimes through coding or circuit design, or some times as pure idle thoughts. "Sit back and reflect", as the great Hercule Poirot says. Admittedly these idle reflections have taught me a lot and I believe widened my perspective to an extent. I feel its really enriching to try and imagine all the pitfalls that one's design might get trapped into. A good designer I believe, can not only correct design flaws, but also predict and prevent them.

Following is an abstract of the project

"Identification of plant disease is of paramount importance in the greenhouse and plant wilting is a primary cause for loss of revenue in the industry. The need for an automated feature to identify plant anomaly is therefore necessary. The current work describes a farm robot with multiple sensors interfaced to acquire information about various physical parameters of the specimen as well as the environment. Image processing for defect identification utilizes machine vision and neural networks. The robot therefore serves as an efficient method for early detection of plant illness besides helping the user correct any anomalies that may be prevailing in the system. Besides the inherent fore-warning capabilities, it also enables the user to put in place measures to check further spread of any particular plant affliction."

We published our work in Procedia Engineering 2011 by Elsevier. Here are some slides, which I used for presenting the paper in Malaysia. (File upload courtesy opendrive!!, I found this site really useful)

This project is really close to me as it was the true beginning of what has been a wonderful journey as an undergrad student of Electrical Engineering. I sincerely hope that I can keep going along this quest, and who knows, be a part of future revolutions in the information age....