2.1 Spread Spectrum Communications Flashcards
What is Processing Gain wrt to Spread Spectrum?
Processing gain is the difference between the spread and de-spread signals. The signal gets stronger as it is de-spread at the receiver due to constructive interference.
How does Spread Spectrum work?
The signal is spread accross a wide bandwidth using a spreading code.
The receiver de-spreads the signal with the same spreading code.
In this way you can transmit multiple signals over the BW and only the receivers with the correct spreading code will de-spread it.b
How does Spread Spectrum reduce the probability of intercept?
The power density can be spread enough that it is lower than the noise threshold, hiding the signal in the noise.
How is Spread Spectrum reistant to Jamming?
Same way the POI is reduced. It hides as noise.
What is Direct Sequence Modulation
The signal is spread by directly modulating the data with a spreading code.
This uses a wide bandwidth because it is spread over a broad frequency range.
This also gives it resistance to narrowband interference.
What is Frequency Hopping Spread Spectrum?
The signal code is spread by rapidly switching the carrier frequency among many channels within a specified frequency band.
This does not lower the power like DSM since it hops between narrow frequency bands.
However, it still provides resistance to narrowband interference by rapidly changing frequencies, making it difficult for an interfering signal to affect the entire communication.
