28-09-2012, 04:16 PM
Wireless Sensor Networks and How They Work
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Abstract
Wireless sensor networks are a budding technology with the potential to change the way
that we live. This report explains the workings of each network as a system of tiny
computers called motes and the parts of the network. Furthermore , this report goes on to
explain the parts of each mote, including a portion on MEMS technology to show the
development of motes.
Introduction
Wireless technology has expanded the limits of our world. Through this innovation, people have been given freedom to work away from their desks or even outside. The new found freedom that people are beginning to enjoy with their computers has started making the world of technology and nature blend. Wireless Sensor Networks are the next stage of this technology-nature cohesion. Although a young technology, the applications have been varied and promise to be even more varied. These networks are collections of small devices, known as motes, with limited computational power.
Wireless Sensor Networks, or WSNs, have been used to enable better data collection in scientific studies, create more effective strategic military defenses. All of these uses depend on the ability to collect data such as light, vibration, moisture, temperature, and more, as well as the ability to communicate with each other. This last ability is what makes a collection of motes so much more powerful than any mote in particular.
The purpose of this report is to explain how wireless sensor networks work, including the workings for each individual mote. The way the multi-function chips are made, as well as the communication system will be discussed. Past uses and potential applications will be touched upon briefly to further illustrate the faculty of these machines. The introduction of these collections of computing devices has brought forth changes in factory safety, machine maintenance, data collection, and military effectiveness
Section one describes how motes communicate with each other, the way they collect data, and the way they transfer data to a computer. The following section will discuss the capabilities and structure of an individual mote. The next section contains information about the chips used in the motes, including information about Micro-Electronic Mechanical Systems, MEMS, and how that applies to this field.
WSNs: How do motes make up a system?
Wireless Sensor Networks are collections of motes. Motes are the individual computers that work together to form networks. The requirements for motes are extensive. They must be small, energy efficient, multifunctional, and wireless. Collections of motes communicate with each other to reach a common goal. For example, if the goal is to collect information about the microclimates around all sections of redwoods in a forest, the motes are placed in the trees to form a network. Once placed, they collect and transmit data to each other, and eventually to a main computer.
Due to interference from the surroundings and the mote’s maximum broadcast range, not all of the motes placed around trees can communicate will all others. The mote’s radios are designed to save as much power as possible and therefore have a limited broadcast range. This range is approximately 30 meters .
How do motes communicate with each other?
Motes communicate with each other using radio transmitters and receivers. They form networks with other motes that change with the positions of the motes. They create links with each other in different configurations to maximize the performance for each mote.
These links all lead to the “parent” mote, which transmits the information from each of the “child” motes to whatever computer or PDA type device is used to collect and process the data. Figure 1 illustrates one possible path data can travel between the outermotes and those close to the computer.
Figure 1. The Motes 1 through 13 are the children motes (all the ones in light grey), Mote 14 is the parent
(in purple). The “Computer” (in red) can be any type of computer such as PDA, laptop, etc. as long as it is
capable of accessing the internet via a specified ISP (the grey building with yellow windows).