Introduction to Mobile Computing & GSM

Mobility

• What is Mobility????• Both Physical & Virtual objects are now Mobile– Physical – Movements of matter– Virtual – Movements of bits and bytes

• User Mobility- Access to Similar Communication device at different Places

• Device Portability- Communication device moves with or without user

What is Mobile Computing

Frequencies for Communication

Propagation Modes

Frequencies & Regulations

Categories of devices

• Communication Device can exhibit thus one of the following characteristics– Fixed & Wired– Mobile & Wired– Fixed & Wireless– Mobile & Wireless

Evolution of Wireless Data

• 1G – Analog Technology- FDMA. Ex.- AMPS• 2G – Digitized Technology – FDMA + TDMA. Ex.-

GSM• Both the above are circuit switched• 2.5G – Voice is circuitized but data is packetized

– FDMA + TDMA. Ex.- GPRS• 3G – Spread Spectrum technique for media

access & encoding. Both data & voice are packetized.

Multiplexing

Frequency Multiplexing

Time Multiplexing

Time & Frequency Multiplexing

Code Multiplexing

Spread Spectrum Technique

Cell Structure

Frequency Planning

GSM

• GSM• formerly: Groupe Spéciale Mobile (founded

1982)• now: Global System for Mobile Communication

( Since 1991)• Types of GSM• GSM 900• GSM 1800• GSM 1900

GSM Architecture & Entities