GPU-Enabled Adaptive Frequency Domain Equalization for Fully Virtualized Coherent Access Networks

In recent years, access and metro networks have been transitioning toward architectures based on disaggregation and virtualization, where software-based implementation of physical-layer signal processing on general-purpose computing platforms has become an important technical challenge. In next-generation access systems, digital coherent transmission enables high-order modulation and polarization multiplexing but requires computationally intensive digital signal processing, such as polarization demultiplexing and adaptive equalization, to be executed in real-time. However, conventional time-domain equalization suffers from computational complexity that increases linearly with the number of equalizer taps, making real-time operation challenging under long-tap conditions caused by chromatic dispersion compensation and future wideband transceivers. To address this issue, this paper proposes a multi-thread frequency-domain adaptive equalizer (MT-FDE) that fully exploits the parallel processing capability of a graphics processing unit (GPU). By combining fast Fourier transform (FFT)–based frequency-domain processing with batch processing, the proposed method reduces computational complexity to logarithmic order with respect to the tap length and enables real-time adaptive equalization including polarization demultiplexing. Numerical simulations and offline and real-time experiments demonstrate that the proposed MT-FDE improves the tolerance to increased tap numbers by a factor of 4.8 and achieves real-time operation under long-tap conditions while maintaining transmission performance comparable to that of conventional time-domain equalizers, providing practical design guidelines for fully virtualized coherent access networks.