Overview of Wireless NetworksBy Najeeb Haider Zaidi

Wireless Network

•Difference between Guided and Unguided Medium

•Wireless Communications▫Rapid Growth▫Cellular Systems▫Wireless LAN’s▫Wireless Sensors Networks

History of Wireless Networks

Technical Objectives

Current Wireless SystemsCellular Telephony

Cellular Architecture

Current Cellular Network Architecture

Current Wireless SystemsCordless Phones

Cordless Phones•Evolved in 1970’s•Low Cost Low Mobility

Wireless Link to PSTN•CT-2 are used as telephone

Booth, they have extended range and nearly the similar voice Quality as compared to the 1st Generation Cordless Telephony

Current Wireless SystemsWireless Local Area Network

Wireless LAN Standards• 802.11a

▫300MHz spectrum ▫5GHz frequency Range▫Multicarrier Modulations▫20-70Mbps Data rate (50m Range)

• 802.11b▫80MHz Spectrum▫2.4GHz Frequency Range▫Multicarrier Modulations▫1.6Mbps Data rate (150m Range)

• 802.11g▫Can be used on either 2.4GHz or 5GHz band▫Multicarrier Modulations▫54Mbps Data rate

Current Wireless SystemsBroadband Wireless Networks

BWA

•Broadband wireless access provides high-rate wireless communications between a fixed access point and multiple terminals.

•Provides Interactive Video Services, High Speed Data Access to Internet to the Home/Business Users.

Types of BWA

•28 GHz spectrum for local distribution systems (local multipoint distribution systems or LMDS).

•2 GHz spectrum for metropolitan distribution systems (multichannel multipoint distribution services or MMDS).

•WiMax 10-66GHz with two sub standards 802.16d and 802.16e.

Applications of The Types

•LMDS•MMDS•Mobile WIMAX

Current Wireless SystemsSatellite Networks

Satellite Mobile (Voice/Data)• 1st Generation Inmarsatt and OmniTRACKS

▫GEO Satellites▫Provides Location Updates and Alphanumeric

Messaging besides 2 way voice communications

▫Large and Bulky Handsets are used with 1m Parabolic Dish

• 2nd Generation (Irridium, Globalstar)▫LEO Satellites▫Global Roaming with a single Phone Number▫Smaller Handset▫Data rates upto 10Kbps

Satellite Video Broadcast

•Analog Video Broadcast•Digital Video Broadcast•Live Video Coverage•High Capacity VSATT Links•Digital Satellite News Gathering•Satellite Positioning

Current Wireless SystemsLow Cost Low Power RadiosBluetooth and Zigbee

Bluetooth• Provides short range connection between wireless

devices with networking capabilities.• Connection is based on a tiny microchip which can

be installed in Laptops, Mobile phones, Palmtops and Network Access Points

• Achieves 10m range at 1mW of output power and 100m at 100mW of output power.

• The system operates at 2.4GHz unlicensed frequency band

• Provides 1 Asynchronous Data Channel at 723.2Kbps

• 3 Synchronous Channels each with 64Kbps data rate can be used.

Zigbee• The ZigBee3 radio specification is designed for

lower cost and power consumption than Bluetooth . • The specification is based on the IEEE 802.15.4

standard. • The radio operates in the same band as Bluetooth,

and is capable of connecting 255 devices per network.

• The specification supports data rates of up to 250 Kbps at a range of up to 30 m.

• The goal of ZigBee is to provide radio operation for months or years without recharging, thereby targeting applications such as sensor networks and inventory tags.

Current Wireless SystemsUltra Wideband Radio

Ultra Wide Band Radios • Ultra Wide Band (UWB) radios are extremely wideband radios

with very high potential data rates. • The concept of ultra wide band communications actually

originated with Marconi’s spark gap transmitter, which occupied a very wide bandwidth.

• However, since only a single low-rate user could occupy the spectrum, wideband communications was abandoned in favor of more efficient communication techniques.

• FCC in 2002 allowed operation of UWB devices as system underlayed beneath existing users over a 7 GHz range of frequencies.

• These systems can operate either at baseband or at a carrier frequency in the 3.6-10.1 GHz range.

• The underlay in theory interferers with all systems in that frequency range, including critical safety and military systems, unlicensed systems such as 802.11 wireless and Bluetooth, and cellular systems where operators paid billions of dollars for dedicated spectrum use.