Terminology » 6G » OTFS vs OFDM: Key Differences Explained

OTFS vs OFDM: Key Differences Explained

otfs ofdm modulation 5g 6g wireless communication

Both OTFS and OFDM are modulation techniques used as multi carrier waveforms. OFDM works in time frequency domain where as OTFS works in delay doppler domain. Let us understand each before we delve into differences between them.

OFDM

  • It is a widely used modulation technique that transmits data by splitting it across multiple closely spaced orthogonal subcarriers in the time frequency domain.
  • Each subcarrier carries a portion of the data, allowing efficient use of bandwidth and resistance to frequency selective fading.
  • Advantages : simplicity, high spectral efficiency and ease of implementation.
  • Disadvantages : OFDM struggles in high mobility environments due to sensitivity to Doppler shifts which leads to inter carrier interference (ICI) and degraded performance.
  • Applications : 4G LTE, 5G NR, Wi-Fi, DVB

OTFS

  • It is an advanced modulation technique designed for high mobility and time varying wireless channels,
  • Unlike OFDM, OTFS operates in the delay Doppler domain, which offers a more stable representation of fast changing channels.
  • It spreads each data symbol across the entire time frequency space, allowing all symbols to experience the full channel diversity.
  • OTFS transforms a rapidly varying multipath channel into a nearly static and sparse one.
  • Advantages : Improvement in reliability and robustness, more effective equalization and significantly lower bit error rates in challenging environments like V2X, drones and satellites.
  • Applications : Ideal for 6G and future wireless systems.

Difference between OTFS and OFDM

FeatureOTFSOFDM
Full FormOrthogonal Time Frequency SpaceOrthogonal Frequency Division Multiplexing
Modulation DomainDelay-Doppler domainTime-Frequency domain
Mobility SupportExcellent (high Doppler environments like V2X, UAVs, HSR)Poor to moderate (suffers under high Doppler)
Doppler robustnessHighLow
Computational ComplexityHigh, requires ISFFT/SFFT transforms and advanced channel estimation techniqueLow, well established and optimized processing pipelines
Hardware Complexityrequires changes in baseband design and needs new hardwareCompatible with existing systems and chipsets
Equalizer designSimpler due to sparse, static channel in delay-Doppler domainMore complex equalization under Doppler shift
Channel BehaviorTransforms time varying channel into quasi static sparse channelChannel appears rapidly time-varying under high mobility
Diversity utilizationFully utilizes time and frequency (delay & Doppler) diversityLimited frequency diversity, low time diversity
Bit Error Rate (BER)Lower BER under high mobility and fadingHigher BER in dynamic/multipath environments
Spectral efficiencyHighModerate
LatencySlightly higher due to additional transformsLower latency for short packets
StandardizationUnder research for 6GFully standardized in 4G/5G systems

Summary

OFDM is mature, simple and works well in stable environments. OTFS is a next generation solution, better suited for extreme mobility and dynamic channels, making it a strong candidate for 6G.