DFT-spread Affine Frequency Division Multiplexing for Doubly Dispersive Channels

This thesis investigates DFT-spread affine frequency division multiplexing and spa-

tially modulated DFT-spread affine frequency division multiplexing for high-mobility

wireless communication. High-mobility communication channels are affected by both

delay spread and Doppler spread, making the channel doubly selective and degrad-

ing the performance of conventional orthogonal frequency division multiplexing. To

overcome these deleterious effects, orthogonal time frequency space modulation and

affine frequency division multiplexing have been proposed. Affine frequency division

multiplexing uses chirp-domain affine Fourier processing and is therefore suitable for

doubly dispersive channels. However, practical transmitters also require low peak-to-

average power ratio. To address these requirements, this thesis first develops a DFT-

spread AFDM transceiver for doubly dispersive channels. DFT spreading improves

the peak behavior of the transmitted waveform, while AFDM provides robustness

against delay–Doppler dispersion. The thesis then extends the waveform into a spa-

tial modulation-based MIMO framework, where the information is carried by both the

modulation symbol and the active antenna index. The proposed spatially modulated

DFT-spread AFDM system reduces active RF-chain requirements while maintaining

high-mobility waveform robustness. Simulation-based results show that DFT-spread

AFDM and spatially modulated DFT-spread AFDM provide favorable BER, PAPR,

and complexity trade-offs compared with benchmark systems based on OFDM and

OTFS. The thesis also discusses practical implementation issues and future research

directions for high-speed railway, vehicular, UAV, satellite, and 6G-oriented commu-

nication scenarios.

• Supervision