# A Rate-Adaptive MAC Protocol for Flexible OFDM-PONs

## TL;DR

This paper introduces a new MAC protocol for OFDM-PONs that enables flexible data rate switching, validated through FPGA implementation.

## Contribution

A novel rate-adaptive MAC protocol with a three-layer header and dynamic rate probing mechanism for OFDM-PONs is proposed and experimentally verified.

## Key findings

- The protocol supports flexible net data rate switching from 8.1 Gbit/s to 32.8 Gbit/s on the downlink.
- A custom ring buffer pool was implemented for efficient multi-ONU data management.
- The protocol enables efficient management of multiple users with diverse, distance-dependent data rates.

## Abstract

What are the main findings?
A novel TDM-based, rate-adaptive MAC protocol for OFDM-PONs was designed, featuring a new physical adaptation sublayer and a discretized rate-stage model to manage variable transmission speeds.The OLT-side protocol was fully implemented in FPGA and experimentally validated, demonstrating flexible net data rate switching on the downlink from 8.1 Gbit/s to 32.8 Gbit/s.

A novel TDM-based, rate-adaptive MAC protocol for OFDM-PONs was designed, featuring a new physical adaptation sublayer and a discretized rate-stage model to manage variable transmission speeds.

The OLT-side protocol was fully implemented in FPGA and experimentally validated, demonstrating flexible net data rate switching on the downlink from 8.1 Gbit/s to 32.8 Gbit/s.

What are the implications of the main findings?
This work provides a complete, hardware-verified solution that bridges the critical gap between flexible OFDM physical layer advancements and practical, system-level network deployment.The protocol enables next-generation optical access networks to efficiently manage multiple users at diverse, distance-dependent data rates, which is a foundational requirement for deploying OFDM-PONs.

This work provides a complete, hardware-verified solution that bridges the critical gap between flexible OFDM physical layer advancements and practical, system-level network deployment.

The protocol enables next-generation optical access networks to efficiently manage multiple users at diverse, distance-dependent data rates, which is a foundational requirement for deploying OFDM-PONs.

The practical deployment of Orthogonal Frequency Division Multiplexing Passive Optical Networks (OFDM-PONs) is hindered by the lack of a Medium Access Network (MAC) protocol capable of managing their flexible, distance-dependent data rates, despite their high spectral efficiency. This paper proposes and validates a novel rate-adaptive, Time Division Multiplexing (TDM)-based MAC protocol for OFDM-PON systems. A key contribution is the design of a three-layer header frame structure that supports multi-ONU data scheduling with heterogeneous rate profiles. Furthermore, the protocol incorporates a unique channel probing mechanism to dynamically determine the optimal transmission rate for each Optical Network Unit (ONU) during activation. The proposed Optical Line Terminal (OLT) side MAC protocol has been fully implemented in hardware on a Xilinx VCU118 FPGA platform, featuring a custom-designed ring buffer pool for efficient multi-ONU data management. Experimental results demonstrate robust upstream and downstream data transmission and confirm the system’s ability to achieve flexible net data rate switching on the downlink from 8.1 Gbit/s to 32.8 Gbit/s, contingent on the assigned rate stage.