Although there are many different implementations of spread spectrum technology, what are the only types specified by the Federal Communications Commission (FCC) in CFR Part 15?

• A. Direct Sequencing Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).
• B. CDMA and OFDM.
• C. DSSS only.
• D. FHSS only.

Answer: (A)

Spread-spectrum implementations defined by the FCC under CFR Part 15 are two: Direct Sequence Spread Spectrum and Frequency Hopping Spread Spectrum.

In direct sequence spread spectrum, the data is combined with a high-rate pseudorandom code, spreading the signal across a wide bandwidth. The receiver uses the same code to despread and recover the original data. In frequency hopping spread spectrum, the carrier rapidly hops among multiple frequencies according to a pseudorandom sequence, so the energy is spread over time and frequency. Both methods are the two types specified by the regulation, which is why they’re the correct answer.

CDMA is a broader concept that uses spreading but isn’t listed as a distinct spread-spectrum type in CFR Part 15, and OFDM is a modulation technique rather than a spread-spectrum type defined there.