Affine Frequency Division Multiplexing Over Wideband Doubly-Dispersive Channels With Time-Scaling Effects

2025-07-04

AI Summary

In wideband doubly-dispersive channels, time-scaling effects (pulse broadening/compression) severely degrade the performance of Affine Frequency Division Multiplexing (AFDM) systems. Method: This paper first models and reveals the equivalent channel sparsity of AFDM in the discrete affine Fourier domain; proposes a novel AFDM architecture employing chirp-based cyclic prefix/suffix, with jointly optimized chirp parameters to match the channel’s time–frequency distortion characteristics; and designs a cross-domain distributed orthogonal approximate message passing (CD-D-OAMP) detector, integrating pairwise error probability analysis and state evolution theory for low-complexity, highly parallel detection. Contribution/Results: Simulation results demonstrate that the proposed scheme significantly outperforms existing modulation and detection methods, achieving substantial reductions in bit error rate and latency while maintaining high computational efficiency.

Technology Category

• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Distributed Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

The recently proposed affine frequency division multiplexing (AFDM) modulation has been considered as a promising technology for narrowband doubly-dispersive channels. However, the time-scaling effects, i.e., pulse widening and pulse shortening phenomena, in extreme wideband doubly-dispersive channels have not been considered in the literatures. In this paper, we investigate such wideband transmission and develop an efficient transmission structure with chirp-periodic prefix (CPP) and chirp-periodic suffix (CPS) for AFDM system. We derive the input-output relationship of AFDM system under time-scaled wideband doubly-dispersive channels and demonstrate the sparsity in discrete affine Fourier (DAF) domain equivalent channels. We further optimize the AFDM chirp parameters to accommodate the time-scaling characteristics in wideband doubly-dispersive channels and verify the superiority of the derived chirp parameters by pairwise error probability (PEP) analysis. We also develop an efficient cross domain distributed orthogonal approximate message passing (CD-D-OAMP) algorithm for AFDM symbol detection and analyze its corresponding state evolution. By analyzing the detection complexity of CD-D-OAMP detector and evaluating the error performance of AFDM systems based on simulations, we demonstrate that the AFDM system with our optimized chirp parameters outperforms the existing competitive modulation schemes in time-scaled wideband doubly-dispersive channels. Moreover, our proposed CD-D-OAMP detector can achieve the desirable trade-off between the complexity and performance, while supporting parallel computing to significantly reduce the computational latency.

Problem

• Addresses time-scaling effects in wideband doubly-dispersive channels
• Optimizes AFDM chirp parameters for improved transmission performance
• Develops efficient CD-D-OAMP algorithm for low-complexity symbol detection

Innovation

• Uses chirp-periodic prefix and suffix
• Optimizes AFDM chirp parameters
• Develops CD-D-OAMP detection algorithm