# Introduction to Frequency Hopping Spread Spectrum by 2lROJe5M

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```									      Introduction
to
Spectrum

- Supreet Tare
Recap
•   When was Nicola Tesla born?
•   With who did he started working in Paris?
•   Apart of Frequency Hopping why is Tesla known for?
•   What was the need for which Tesla came up with Frequency
Hopping mechanism?
•   How is it that Tesla achieved Security for his submersible boat?
•   Explain the basic concept of Frequency Hopping.
•   What is the definition for FHSS?
•   What were the other systems that make use of FH during early
nineties?
•   What are the advantages of Frequency Hopping?
•   What are the areas of application where FH can be used?
Techniques
•   Frequency Hopping Spread Spectrum (FHSS)
•   Direct Sequence Spread Spectrum (DSSS)
•   Time Hopping Spread Spectrum (THSS)
FHSS Algorithm
• The initiating party sends a request via a predefined frequency or control
channel.
• Once the receiving party have received the request, it sends a pseudo
number called seed to the transmitting party via the same channel.
• The initiating party uses this seed as a variable in predefined algorithm
and calculates the sequence of frequencies that must now be used to
transmit the signals. Most often the period of frequency change is
predetermined.
• The initiating party then sends the first piece of information via the lowest
band of newly generated frequency spectrum. Thus acknowledging the
receiving party that it has correctly calculated the sequence.
• The communication begins, and both the receiving party and the sending
party change the frequencies along with the calculated order. Starting at
the same point of the time.
FHSS Algorithm

In FH Data is divided into chunks and transmitted at different frequencies at
different times.
Image source: GlobalSpec.com
•   Highly restraint to narrowband interferences.
•   Low probability of Intercept.
•   Bandwidth becomes sharable.
•   Improved system efficiency.
• Thank You

– Supreet Tare
– Lecturer, Electronics and Communication
– Shriram Institute of Technology, Jabalpur

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