AFDM Channel Estimation in Multi-Scale Multi-Lag Channels
arxiv(2024)
摘要
Affine Frequency Division Multiplexing (AFDM) is a brand new chirp-based
multi-carrier (MC) waveform for high mobility communications, with promising
advantages over Orthogonal Frequency Division Multiplexing (OFDM) and other MC
waveforms. Existing AFDM research focuses on wireless communication at high
carrier frequency (CF), which typically considers only Doppler frequency shift
(DFS) as a result of mobility, while ignoring the accompanied Doppler time
scaling (DTS) on waveform. However, for underwater acoustic (UWA) communication
at much lower CF and propagating at speed of sound, the DTS effect could not be
ignored and poses significant challenges for channel estimation. This paper
analyzes the channel frequency response (CFR) of AFDM under multi-scale
multi-lag (MSML) channels, where each propagating path could have different
delay and DFS/DTS. Based on the newly derived input-output formula and its
characteristics, two new channel estimation methods are proposed, i.e., AFDM
with iterative multi-index (AFDM-IMI) estimation under low to moderate DTS, and
AFDM with orthogonal matching pursuit (AFDM-OMP) estimation under high DTS.
Numerical results confirm the effectiveness of the proposed methods against the
original AFDM channel estimation method. Moreover, the resulted AFDM system
outperforms OFDM as well as Orthogonal Chirp Division Multiplexing (OCDM) in
terms of channel estimation accuracy and bit error rate (BER), which is
consistent with our theoretical analysis based on CFR overlap probability
(COP), mutual incoherent property (MIP) and channel diversity gain under MSML
channels.
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