22-05-2012, 04:55 PM
FREQUENCY HOPPING SPREAD SPECTRUM
FHSS.pptx (Size: 276.94 KB / Downloads: 33)
INTRODUCTION
Implementation of WLANS:
Radio technology − Spread Spectrum Modulation
Spread Spectrum Modulation Techniques:
Frequency-hopping Spread Spectrum.
Direct Sequence Spread Spectrum.
Modern Technology:
Solid state radio frequency circuits – microprocessors
FHSS:
Wide bandwidth of frequency spectrum
transmitter hops around inside the allocated space.
The receiver was designed so it could match the
hopping sequence.
Advantages of this technologies:
Inherent transmission security
Resistance to interference
Redundancy
low power density
Frequency Hopping:
Transmitting radio signals by rapidly switching
a carrier among many frequency channels.
Highly resistant to narrow band interference.
Can share frequency bandwidth.
Principle :-
Transmitter hops in a wide bandwidth of frequency
spectrum set aside.
Design of Receiver – matches hopping sequence.
− reliable communication.
− minimum interference.
Spread Spectrum – bandwidth used is broad
Frequency Hopping – Tx and Rx change frequency
rapidly in a defined pattern.