15-05-2012, 10:20 AM
Human Area Networking Technology: RedTacton
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Abstract
Ubiquitous services that are genuinely user-friendly to everyone will require technologies that enable Communi
cation between people and objects in close proximity.Focusing on the naturalness, inevitability and sense of security conv
eyed by touching in everyday life, this article describes human area net-working technology that enables communication
by touching, which we call RedTacton.
Human area network technology for communication between mobile terminals and between terminals that are
embedded in the environment has become important.when cables are used for communication between terminals, the
routing of the cables is clearly inconvenient .When very weak radio signals are used for the communication, data speeds
are reduced by packet collision and other such problems in crowded places such as exhibition sites and security risk from
unwanted signal interception is another problem.Technology for solving such problems includes the use of the person’s
body as a signal path for communication. A transmission path is formed automatically when a person come into contact
with a device and communication between mobile terminals begins. Here, the human body acts as a transmission medium
supporting IEEE 802.3 half-duplex communication at 10Mbit/s.
Human area network technology for communication between mobile terminals and between terminals that are
embedded in the environment has become important.when cables are used for communication between terminals, the
routing of the cables is clearly inconvenient.when very weak radio signals are used for the communication, data speeds are
reduced by packet collision and other such problems in crowded places such as exhibition sites and security risk from
unwanted signal Interception is another problem. Technology for solving such problems includes the use of the person’s
body as a signal path for communication. A transmission path is formed automatically when a person come into contact
with a device and communication between mobile terminals begins. Here, the human body acts as a transmission medium
supporting IEEE 802.3 half-duplex communication at 10Mbit/s.
1. Introduction
Today people can communicate anytime, anywhere,
and with anyone over a cellul ar 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 such as illustrated in Fig. 1 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 wirel ess 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 solution to
all these constraints of conventional technologies is
“intrabody” communication, in which the human
body serves as the transmission medium. In ubiquitous
servicesb (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 net
-work setup costs.
The concept of intrabody communication, whichuses
the minute electric field propagated by the human body
to transmit information, was first proposed by IBM .
The communication mechanism has subsequently been
evaluated and reported by several research groups arou
-nd the world. However, all
LAN
Peripheral computers
Human area
network
Human area
network
Wearable computers
Human area
network
Human area
network
Fig. 1. Human area networking technology.
those reported technologies had two limitations:
1) the operating range through the body
was limited to a few tens of centimeters and
2) the top communication speed was only 40
kbit/s. These limitations arise from the use of
an electrical sensor for the receiver. An electrical
sensor requires two lines (a signal line
and a ground line), whereas in intrabody
communication there is essentially only one
signal line, i.e., the body itself, which leads to
an unbalanced transmission line, so the signal
is not transmitted correctly.
2. Human area networking
NTT has had excellent success with an
electro-optic sensor combining an electrooptic
crystal with laser light and recently
Transmitte
r
Electric fields
Ground
Eb
Eb
Ea
Human
body
Ec
Laser light
Es
Ec
Electro-optic
sensor
Detector
circuit
reported an application of this sensor for measuring
high-frequency electronic devices [2],
[3]. The electro-optic sensor has three key features:
(1) it can measure electric fields from a device under
test (DUT) without contacting it, which minimizes
measurement disturbance, (2) ultrawide-band measurement
is possible, and (3) it supports one-point
contact measurement that is independent of the
ground, which is the most significant feature in the
present context. NTT utilized this third feature to fabricate
an intrabody communication receiver for its
human area networking technology, which is called
RedTacton*.
The operating principle of RedTacton is illustrated
in Fig. 2. The electric field induced toward the body
Fig. 2. Principle of RedTacton.
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
RedTacton
transceiver
PDA
Transmitter
Data sense
circuit
Detector
circuit
Receiver
Transmitt
er
circuit
Control signal
Electrooptic
sensor
Insulation film
Transmitting/receiving
electrode
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.