Frequency hopping spread spectrum (FH-SS) is a type of spread spectrum technique where the available channel bandwidth is divided into a large number of frequency slots arranged continuously. A transmitted signal occupies one or more of the available frequency slots, with the frequencies selected pseudo-randomly based on the output of a pseudo-noise generator. There are two types of FH-SS: slow FH-SS where one or more data bits are transmitted within one hop, and fast FH-SS where one data bit is divided over multiple hops. FH-SS provides advantages like improved interference rejection, code division multiplexing for CDMA, secure communication, and increased capacity and spectral efficiency. It is used in military communication systems, satellite communication,

1. Frequency Hopping Spread
Spectrum
(FH-SS)
~BY~
HARSHIT GUPTA

2. The term – “Spread Spectrum”
 IN TELECOMMUNICATION AND RADIO
COMMUNICATION, SPREAD SPECTRUM TECHNIQUES
ARE METHODS BY WHICH A SIGNAL GENERATED
WITH A PARTICULAR BANDWIDTH IS DELIBERATELY
SPREAD IN THE FREQUENCY DOMAIN, RESULTING IN
A SIGNAL WITH A WIDER BANDWIDTH.
….SAYS WIKIPEDIA

3. “Spread Spectrum” – In Simple Words
 A MODULATION TECHNIQUE WHEREBY A
MODULATED WAVEFORM IS MODULATED SECOND
TIME IN SUCH A WAY SO AS TO GENERATE AN
EXPANDED BANDWIDTH (WIDEBAND) SIGNAL, THAT
DOES NOT SIGNIFICANTLY INTERFERE WITH OTHER
SIGNALS.

4. Need of Spread Spectrum Technique
 TO PROVIDE EFFICIENT UTILIZATION OF BANDWIDTH
AND POWER.
 TO REJECT INTERFERENCE.
 TO ESTABLISH SECURE COMMUNICATION.

5. Spread Spectrum – “Illustration”

6. Types Of Spread Spectrum
 DIRECT SEQUENCE SPREAD SPECTRUM TECHNIQUE (DS-SS)
 FREQUENCY HOP SPREAD SPECTRUM TECHNIQUE (FH-SS)
 CARRIER SERVICE MULTIPLE ACCESS SPREAD SPECTRUM
(CSMA)
 TIME HOPING
 HYBRID SPREAD SPECTRUM

7. Insight Into – “FH-SS”
 THE AVAILABLE CHANNEL BANDWIDTH IS DIVIDED
INTO A LARGE NUMBER.
 ARRANGED IN CONTINOUS FRQUENCY SLOTS.
 TRANSMITTED SIGNAL OCCUPIES ONE OR MORE OF
THE AVAILABLE FRQUENCY SLOT.
 FREQUENCY SLOTS ARE SELECTED “PSEUDO
RANDOMLY”
 BASED ON THE OUTPUT OF THE PN GENERATOR.

8. FH-SS – “Illustration”

9. …an another illustration

10. FH-SS – “Block Diagram”

11. Pseudo Noise Generator
 USED TO SPREAD THE BANDWIDTH OF THE MODULATED
SIGNAL TO THE LARGER TRANSMISSION BANDWIDTH.

12. Types of FH-SS
THERE ARE TWO TYPES OF FREQUENCY HOPPING:
1. SLOW FREQUENCY HOPPING SPREAD SPECTRUM
2. FAST FREQUENCY HOPPING SPREAD SPECTRUM

13. Difference between Slow & Fast FH-SS
SLOW FAST
In this case one or more data bits
are transmitted within one Hop.
One data bit is divided over
multiple Hops.
Coherent data detection is
possible.
Coherent signal detection is
difficult, and seldom used.
Error controlling can be done No Error controlling

14. Advantages
 IMPROVED INTERFERENCE REJECTION
 CODE DIVISION MULTIPLEXING FOR CDMA
 SECURE COMMUNICATION
 HIGH RESOLUTION RANGING
 INCREASED CAPACITY AND SPECTRAL EFFICIENCY
 LOWER COST OF IMPLEMENTATION
 READILY AVAILABLE IC COMPONENTS

15. FH-SS – “Uses”
 IN MILITARY COMMUNICATION SYSTEMS.
- UNAUTHORISED RECEIVERS CANNOT DETECT
MESSAGE.
- MILITARY RADIOS USES CRYPTOGRAPHIC
TECHNIQUES TO GENERATE THE CHANNEL
SEQUENCE.
- TRANSMISSION SECURITY KEY (TRANSEC)
 IN SATELLITE COMMUNICATION
 IN LOCAL AREA NETWORKS (LAN)

16. Thank You Very Much
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