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FREQUENCY HOPPING SPREAD SPECTRUM

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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.