Next-Generation Passive Optical Network Based on Sparse Code Multiple Access and Graph Neural Networks

Hui Yang,Anlin Yi,Pengcheng Deng,Xianzhuo Zhang,Bangjiang Lin

doi:10.1109/jphot.2021.3128420

Abstract

Sparse code multiple access (SCMA) is a promising technology to provide high throughput and overall improved system performance at affordable cost for next-generation passive optical networks (NG-PONs). Message passing algorithm (MPA) based on a factor graph is usually used for low-complexity multi-user detection in SCMA. However, MPA requires accurate and effective channel estimation due to the interference between the user's signals on the same resource block and suffers uncertain convergence caused by the cycles in the factor graph. In this paper, a graph neural networks (GNN)-based detection method is proposed for SCMA-PON, which performs channel impairment compensation and signal detection in a joint manner. 25.5 Gb/s SCMA-OFDM system over 20/60 km single mode fiber link is simulated to demonstrate the feasibility with 8.5-G class optical devices. The simulation results show that GNN-based detection method outperforms MPA and is more robust to the nonlinear distortion for the same level of computational complexity.

Highlights

Based on a factor graph is usually used for low-complexity multiuser detection in Sparse code multiple access (SCMA)
The independent bit stream of each user is firstly mapped the multi-dimensional codewords selected from the codebook in the SCMA encoding module
The SCMA signals are encoded into SCMA-orthogonal frequency division multiplexing (OFDM) signals with the sizes of inverse discrete Fourier transform (IDFT) and CP 256 and 8, respectively

Summary

INTRODUCTION

Igorous development of Internet of things and the exponentially growth of traffic demand is pushing the optical access networks to provide larger capacity at affordable cost [1]. Various multiplexing methods using orthogonal resources in either frequency (wavelength), state of polarization, code domain or space have been proposed to tackle the performance and cost challenges in LR-PON [6,7,8,9]. In these multiplexing dimensions, the orthogonality of signals must be guaranteed, otherwise different signals cannot be separated correctly without affecting the detection of other signals. In [14], a non-orthogonal optical multicarrier access system based on filter bank and SCMA was proposed and demonstrated with 60 km single mode fiber.

PRINCIPLE

SIMULATION SETUP AND RESULTS

CONCLUSION