30-01-2013, 11:43 AM
INTRODUCTION TO WIRELESS COMMUNICATION SYSTEMS
1INTRODUCTION TO WIRELESS.pdf (Size: 316.31 KB / Downloads: 78)
Example of Wireless Communication
Systems
Examples
Cordless phone
Hand-held walkie-talkies
Pagers
Cellular telephone
Wireless LAN
Mobile
Historically - any radio terminal that could be moves
during operation
More recently - a radio terminal that is attached to a
high speed mobile platform
Portable - hand-held and used at walking speed
Subscriber - mobile or portable user
Subscriber unit - each user’s communication
devices.
Paging Systems
Conventional paging system send brief messages to a subscriber.
Modern paging system: news headline, stock quotations, faxes, etc.
Simultaneously broadcast paging message from each base station
(simulcasting).
Large transmission power to cover wide area.
Cordless Telephone System
Cordless telephone systems are full duplex
communication systems.
First generation cordless phone
in-home use
communication to dedicated base unit
few tens of meters
Cellular Telephone Systems
Provide connection to the PSTN for any user
location within the radio range of the system.
Characteristic
Large number of users
Large Geographic area
Limited frequency spectrum
Reuse of the radio frequency by the concept of
“cell’’.
Wireless Local Area Networks (WLANs)
Suitable for local short-distance networking.
Compatible with existing LANs.
WLANs use unlicensed radio frequence.
WLAN is already affordable and popular
Used widely in airports, railway stations, hotels,
business parks and office buildings
Integrating to laptops and PDA devices.
Trends in Cellular Radio and Personal
Communication
Since 1989, there has been enormous activity throughout
the world to develop personal systems that combined the
network intelligence of today’s PSTN with digital signal
processing and RF technology. The concept is called
Personal Communication Services (PCS).
Indoor wireless networking products are rapidly emerging
and promise to become a major part of the
telecommunications infrastructure. An international
standard body, IEEE 802.11, is developing standards for
wireless access between computers inside buildings.