Frequency Hopping Spread Spectrum (FHSS):
- FHSS uses TDM and FDM, splitting available bandwidth into smaller channels.
- Transmitter and receiver hop between channels after a set time.
- The hopping sequence defines the pattern of frequency changes.
- Dwell time is the duration spent on a frequency before hopping.
- Two types: Slow hopping (few hops per bit) and Fast hopping (multiple hops per bit).
FHSS Transmitter:
- Modulation: User data is modulated using FSK or BPSK (e.g., f₀ for binary 0, f₁ for binary 1).
- Hopping Sequence: Used to generate the carrier frequency fᵢ via a frequency synthesizer.
- Final Modulation: The spread signal is created with frequencies fᵢ + f₀ (for 0) and fᵢ + f₁ (for 1).
FHSS Receiver:
The receiver reverses the FHSS transmission process to recover user data.
- Demodulation: Uses the hopping sequence to extract the narrowband signal.
- Analog-to-Digital Conversion: Converts the signal back to original binary data.