22-06-2011, 11:39 AM
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INTRODUCTION
Today people can communicate anytime, anywhere, and with anyone over a cellular phone network. Moreover, the Internet lets people download immense quantities of data from remotely located servers to their home computers. Essentially, these two technologies enable communications between terminals located at a distance from each other. Meanwhile, all kinds of electronic devices including personal digital assistants (PDAs), pocket video games, and digital cameras are becoming smaller, so people can carry around or even wear various personal information and communication appliances during their everyday activities.
However, user friendly ubiquitous services involve more than just networking between remotely located terminals. Communication between electronic devices on the human body (wearable computers) and ones embedded in our everyday environments is also critical, so this has driven extensive research and development on human area networks. Wired connections between electronic devices in human area networks are cumbersome and can easily become entangled. Short-range wireless communication systems such as Bluetooth and wireless local area networks (IEEE 802.11b, etc.) have some problems. Throughput is reduced by packet collisions in crowded spaces such as meeting rooms and auditoriums filled with people and communication is not secure because signals can be intercepted. The principle drawback of Infrared Communications (IrDA) is the tight directionality of beams between terminals needed for the system to be effective. The ultimate Human Area Network (HAN) solution to all these constraints of conventional technologies is “intrabody” communication, in which the human body serves as the transmission medium. In ubiquitous services (which imply communication between electronic devices embedded in the environment in close proximity to people), if we could use the human body itself as a transmission medium, then this would be an ideal way of implementing human area networks because it would solve at a stroke all the problems including throughput reduction, low security, and high network setup costs. This concept of intrabody communication called REDTACTON uses weak electric fields on the surface of the body as a transmission medium.
Define RedTacton?
• RedTacton is a new Human Area Networking technology that uses the surface of the human body as a safe, high speed network transmission path. It uses the minute electric field emitted on the surface of the human body.
• A transmission path is formed at the moment a part of the human body comes in contact with a RedTacton transceiver. Physically separating ends the contact and thus ends communication is disconnected.
• Using RedTacton, communication starts when terminals carried by the user or embedded in devices are linked in various combinations according to the user's natural, physical movements.
• Communication is possible using any body surfaces, such as the hands, fingers, arms, feet, face, legs or torso. RedTacton works through shoes and clothing as well.
Fig 1.1 shows a typical arrangement of RedTacton
Chapter 2
WORKING and PRINCIPLE
2.1 Working of RedTacton:
The working of RedTacton is as described in the Fig 2.1.
Fig 2.1 working of RedTacton
1. The RedTacton transmitter induces a weak electric field on the surface of the body.
2. The RedTacton receiver senses changes in the weak electric field on the surface of the body caused by the transmitter.
3. RedTacton relies upon the principle that the optical properties of an electro-optic crystal can vary according to the changes of a weak electric field.
4. RedTacton detects changes in the optical properties of an electro-optic crystal using a laser and converts the result to an electrical signal in a optical receiver circuit.
2.2 Operating principle of RedTacton:
The operating principle of RedTacton is illustrated in figure 2.2. The electric field induced toward the body by the transmitter’s signal electrode is represented by Ea. The system requires a ground close to the transmitter signal electrode, so electric field Eb induced from the body can follow a return path to the transmitter ground. Moreover, since people are usually standing on a floor or the ground, electric field Ec escapes from the body to ground, mainly from the feet. The electric field Es that reaches the receiver is Es = Ea – (Eb + Ec). It couples to the electro-optic crystal and changes the crystal’s optical properties. This change is detected by laser light and transformed into digital data by a detector circuit.