Which networks or products use spread spectrum technologies?

• A. Wireless local area networks (WLAN), Bluetooth, and global positioning systems (GPS).
• B. Cellular networks only.
• C. Traditional wired Ethernet.
• D. Satellite television services.

Answer: (A)

Spread spectrum spreads a signal over a wider bandwidth than strictly needed, which helps resist interference, reduces the impact of noise, and allows multiple devices to share the same spectrum. Wireless LANs use spread spectrum techniques in their earlier and some current forms (like DSSS and FHSS), Bluetooth uses frequency-hopping spread spectrum to rapidly switch frequencies and avoid collisions, and GPS relies on pseudorange codes that spread the signal across a wide band to allow receivers to distinguish signals from different satellites and achieve precise timing. Traditional wired Ethernet doesn’t use spread spectrum since it transmits over fixed physical channels, and satellite television uses fixed modulation schemes on a carrier rather than spreading the signal across a wide band. While cellular networks can employ spread-spectrum concepts in some systems, they are not described as “cellular networks only,” so they’re not the definitive best match for networks and products that clearly use spread-spectrum technologies.