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

 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

 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

 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-to- Noise Ratio:

 The electrical signal-to-noise ratio (SNR) of IM/DD links is limited by noise from ambient light sources.

Achieving a High Signal-to- Noise 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.