Orthogonal Frequency Division Multiplexing uses many subcarriers to transmit data. Each subcarrier is a narrow frequency band. They overlap without interfering because they are orthogonal. OFDM is used in Wi-Fi, 4G, 5G, digital TV, and DSL. It is the dominant modulation scheme of modern communication.

OFDM divides a wide channel into many narrow subcarriers. Each subcarrier carries a low-rate data stream. Together they carry a high-rate stream. This makes OFDM robust against frequency-selective fading. If one subcarrier is degraded, others still work. Error correction handles the rest.

OFDM characteristics

• Many subcarriers: narrow, orthogonal
• Robust: handles multipath and fading
• Efficient: uses spectrum well
• Complex: requires FFT processing
• Widely used: Wi-Fi, LTE, 5G, DVB

OFDM has drawbacks. It has a high peak-to-average power ratio, which reduces amplifier efficiency. It is sensitive to frequency and phase noise. It requires precise synchronization. But its advantages outweigh its costs. OFDM is the workhorse of modern wireless and wired communication.