Which statement correctly differentiates FHSS and DSSS?

• A. FHSS hops carrier frequency according to a pseudorandom code; DSSS spreads data with PN code; both increase resistance to interference and enable multiple access
• B. FHSS uses fixed carrier frequency and DSSS uses fixed PN code
• C. FHSS does not provide interference resistance
• D. FHSS and DSSS are identical techniques

Answer: (A)

The key idea is how each method spreads the signal and why that helps in noisy environments and with multiple users.

FHSS (Frequency-Hopping Spread Spectrum) changes the carrier frequency over time following a pseudorandom sequence shared by transmitter and receiver. This hopping makes the signal resilient to narrowband interference because any single interferer only disrupts the transmission for a short portion of the hop cycle, not across the entire bandwidth. The hopping pattern can also separate users by giving them different sequences, enabling multiple access.

DSSS (Direct-Sequence Spread Spectrum) multiplies the data by a high-rate pseudorandom PN code, spreading the signal across a much wider bandwidth. This wider spectrum lowers the impact of narrowband interference and jamming and lets multiple users share the same spectrum via different codes (code division multiple access).

So the statement that FHSS hops the carrier frequency with a pseudorandom code, while DSSS spreads data with a PN code, and that both increase interference resistance and enable multiple access, is correct. The other ideas—FHSS using a fixed carrier, FHSS not providing interference resistance, or FHSS and DSSS being identical—don’t fit how these techniques actually work.