What is ICI?
ICI (Intercarrier Interference) is a form of interference in OFDM systems where energy from one subcarrier leaks into adjacent subcarriers, degrading signal quality. ICI occurs when the orthogonality between subcarriers is broken — typically due to carrier frequency offsets, Doppler shift from high-speed mobility, timing errors, or phase noise. In 5G NR, ICI management is particularly important at high frequencies (FR2/mmWave) and for high-mobility scenarios such as V2X and high-speed rail.
How Does ICI Work?
In a perfectly synchronised OFDM system, subcarriers are mathematically orthogonal and do not interfere with each other. However, any mismatch between transmitter and receiver frequencies — whether from oscillator drift, Doppler shift, or sampling clock offset — destroys this orthogonality. The result is that each subcarrier spreads energy into its neighbours, appearing as noise-like interference. ICI power increases with the frequency offset relative to subcarrier spacing, which is why 5G NR’s flexible numerology allows wider subcarrier spacings (30, 60, 120, 240 kHz) for higher frequency bands and high-mobility scenarios, directly reducing ICI impact.
Use Cases
5G NR numerology selection for high-mobility scenarios, V2X communication system design, mmWave link performance optimization, receiver algorithm design for ICI mitigation, and high-speed train communication system planning.
3GPP / Standards Reference
3GPP TS 38.211 (NR physical channels and modulation), 3GPP TS 38.104 (NR BS radio transmission and reception)
Related Terms
CPE | OFDM | Numerology | Carrier Aggregation | EVM
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
