Which type of modulation technique is used in local area wireless networks (LAWNs)?

Orthogonal Frequency-Division Multiplexing (OFDM) is the primary modulation technique used in modern local area wireless networks (LAWNs), also known as WLANs or Wi-Fi. It was introduced with the IEEE 802.11a and 802.11g standards to achieve higher data rates and improve resilience to multipath interference. All subsequent major Wi-Fi standards, including 802.11n, 802.11ac, and 802.11ax (Wi-Fi 6/6E), are built upon OFDM, often combining it with other technologies like MIMO (Multiple-Input Multiple-Output) to further increase throughput and reliability.

A. FHSS (Frequency-Hopping Spread Spectrum) was used in the original 802.11 standard but was quickly superseded due to its low data rate.
C. DSSS (Direct-Sequence Spread Spectrum) was used in the 802.11b standard but was replaced by the more efficient OFDM in later standards.
D. MIMO-OFDM describes a system using both MIMO and OFDM. While correct for modern networks (802.11n and later), OFDM is the fundamental modulation technique itself, making it the more accurate and foundational answer.

1. IEEE Std 802.11-2020. (2020). IEEE Standard for Information Technology--Telecommunications and Information Exchange between Systems Local and Metropolitan Area Networks--Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. IEEE. Clause 17 (OFDM PHY specification for 5 GHz band) and Clause 19 (ERP-OFDM PHY specification for 2.4 GHz band).

2. Van Nee, R., & Prasad, R. (2000). OFDM for wireless multimedia communications. Artech House. Chapter 6, "OFDM in Wireless LANs". (Details the adoption and implementation of OFDM in IEEE 802.11a).

3. Perahia, E., & Stacey, R. (2013). Next Generation Wireless LANs: 802.11n and 802.11ac (2nd ed.). Cambridge University Press. Chapter 2, "The Evolution to OFDM". (Explains the transition from DSSS to OFDM as the core technology for high-throughput WLANs).