24-07-2012, 11:46 AM
CELLULAR NETWORK
[attachment=28632]
INTRODUCTION
A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station.
Guglielmo Marconi invented the first Radio application for Naval requirements In 1912, with the drowning of the Titanic, Radio communications became essential In 1930, the First mobile transmitter was developed.
CELLULAR NETWORK ORGANISATION
Use multiple low-power transmitters (100 W or less)
Areas divided into cells
Each served by its own antenna
Served by base station consisting of transmitter, receiver, and control unit
Band of frequencies allocated
Cells set up such that antennas of all neighbors are equidistant (hexagonal pattern)
OPERATION OF CELLULAR SYSTEM
Base station (BS) at center of each cell
Antenna, controller, transceivers
Controller handles call process
Number of mobile units may in use at a time
BS connected to mobile telecommunications switching office (MTSO)
One MTSO serves multiple BS
MTSO to BS link by wire or wireless
MTSO: Assigns voice channel
Performs handoffs
Monitors calls (billing)
3 algorithms specified in GSM
A3 for authentication (“secret”, open interface)
A5 for encryption (standardized)
A8 for key generation (“secret”, open interface)
ADVANTAGES OF CDMA CELLULAR
Frequency diversity – frequency-dependent transmission impairments have less effect on signal
Multipath resistance – chipping codes used for CDMA exhibit low cross correlation and low autocorrelation
Privacy – privacy is inherent since spread spectrum is obtained by use of noise-like signals
Graceful degradation – system only gradually degrades as more users access the system
[attachment=28632]
INTRODUCTION
A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station.
Guglielmo Marconi invented the first Radio application for Naval requirements In 1912, with the drowning of the Titanic, Radio communications became essential In 1930, the First mobile transmitter was developed.
CELLULAR NETWORK ORGANISATION
Use multiple low-power transmitters (100 W or less)
Areas divided into cells
Each served by its own antenna
Served by base station consisting of transmitter, receiver, and control unit
Band of frequencies allocated
Cells set up such that antennas of all neighbors are equidistant (hexagonal pattern)
OPERATION OF CELLULAR SYSTEM
Base station (BS) at center of each cell
Antenna, controller, transceivers
Controller handles call process
Number of mobile units may in use at a time
BS connected to mobile telecommunications switching office (MTSO)
One MTSO serves multiple BS
MTSO to BS link by wire or wireless
MTSO: Assigns voice channel
Performs handoffs
Monitors calls (billing)
3 algorithms specified in GSM
A3 for authentication (“secret”, open interface)
A5 for encryption (standardized)
A8 for key generation (“secret”, open interface)
ADVANTAGES OF CDMA CELLULAR
Frequency diversity – frequency-dependent transmission impairments have less effect on signal
Multipath resistance – chipping codes used for CDMA exhibit low cross correlation and low autocorrelation
Privacy – privacy is inherent since spread spectrum is obtained by use of noise-like signals
Graceful degradation – system only gradually degrades as more users access the system