Wireless
Infrared LAN
introduction
INTRODUCTION
 Now
a days the telecommunication
principles takes a wide ways and types
can be classified according to the
medium and frequencies used ; IR LANS or
routers is a part that uses the IR
frequencies to transport such a data and
build networks.
INTRODUCTION
INTRODUCTION
 The
network
shown can use IR
LANS to connect
the PCs but with
limitations (Line of
sight required to
transport with IR
frequency.
INTRODUCTION
 UNLIKE
radio LANS (routers) it can be
transmitted even if LOS is not avaliable (i.e
through walls)
INTRODUCTION
 UNLIKE
radio LANS (routers) it can be
transmitted even if LOS is not avaliable (i.e
through walls)
 BUT
data ranges and BW is better in IR and
channels can be separated because of
wide frequency range (carrier frequency will
be > 200 THZ and BW easily becomes wider)
INTRODUCTION
 UNLIKE
radio LANS (routers) it can be
transmitted even if LOS is not available (i.e
through walls)
 BUT
data ranges and BW is better in IR and
channels can be separated because of
wide frequency range (carrier frequency will
be > 200 THZ and BW easily becomes wider)
 IR
is more SECURED than radio networks
INTRODUCTION
INTRODUCTION
 This
table shows a differences between IR
and radio LANs
INTRODUCTION
 This
figure shows a typical topology for IR
Network (for example)
THE WIRELESS IR Channel
THE WIRELESS IR Channel
 Non-directed
infrared links, which do not
require alignment between transmitter
and receiver, can be categorized as
either line-of-sight (LOS) or diffuse ; LOS
links means communication with a line
without any object but diffuse can
depends on reflections
THE WIRELESS IR Channel
 The
optical signal in a diffuse link can
undergo many reflections and still have
appreciable energy.
THE WIRELESS IR Channel
 The
optical signal in a diffuse link can
undergo many reflections and still have
appreciable energy.
 Practical
wireless infrared link will use
intensity modulation and direct detection
(IM/DD).
Achieving a High Signal-toNoise Ratio:
Achieving a High Signal-toNoise Ratio:
 The
electrical signal-to-noise ratio (SNR) of
IM/DD links is limited by noise from
ambient light sources.
Achieving a High Signal-toNoise Ratio:
 The
electrical signal-to-noise ratio (SNR) of
IM/DD links is limited by noise from
ambient light sources.

Since a photodetector produces a
current proportional to the received
optical power, the SNR of IM/DD links is
proportional to the square of the received
optical power.
Bandwidth Reuse in Multi-User
Systems
 Evaluations
of the performance of time-,
subcarrier frequency- and code-division
multiple-access (TDMA, FDMA, and
CDMA) schemes for bandwidth reuse,
demonstrating this advantage of infrared
over radio.It appears also possible to
employ space-division multiple-access
(SDMA) with infrared, leading to an even
greater increase in network capacity.
Future Developments
 Optical
technology and communication
techniques could enable the realization
of a LAN that employs very high-bit-rate
(up to 100 Mb/s) diffuse infrared links to
access a wired backbone.
 Such
a LAN would enable users to run
communication-intensive applications,
including real-time video, on portable
computers.