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Technical & Engineering

COFDM

Coded Orthogonal Frequency Division Multiplexing; a highly complex modulation method used heavily in DAB and digital television.

What is COFDM?

COFDM is the modulation scheme underpinning DAB radio, DAB+, DVB-T digital television, and several mobile-TV standards. It splits the transmitted signal across many closely-spaced orthogonal subcarriers, spreading the information across frequency. Even if specific subcarriers are wiped out by multipath interference or fading — a frequent problem for mobile reception — the error-correction coding embedded in COFDM recovers the original data.

The engineering elegance of COFDM is why digital terrestrial broadcast works robustly in cars, buses, and trains. Analog FM fades, crackles, and distorts when a driver passes through a tunnel or under an overpass; COFDM simply blanks out momentarily and resumes with no audible artefacts. This resilience is the single biggest practical advantage of digital-terrestrial broadcast over analog.

Why it matters

Provides immense ruggedness and resistance against transmission distortions, signal fading, and multipath interference in mobile vehicular environments.

Related terms

  • Bed— An instrumental music track played continuously underneath a presenter's voice or a commercial narrative read.
  • DAB / DAB+ (Digital Audio Broadcasting)— The dominant European standard for the digital transmission of radio signals, utilizing advanced audio coding (HE-AAC v2) for superior quality.
  • HD Radio— The proprietary in-band on-channel (IBOC) digital radio standard utilized predominantly across North American markets.
  • RDS (Radio Data System)— A standardized communications protocol used for embedding small amounts of digital information into conventional analog FM radio broadcasts.