Analysis and Design of Adaptive OCDMA Passive Optical Networks

TL;DR

This paper analyzes the BER performance of multi-class OCDMA systems, proposes a new approximation method for system analysis, and introduces adaptive code allocation algorithms for OCDMA-PONs that improve performance under dynamic traffic.

Contribution

It presents a novel BER approximation method and adaptive code allocation algorithms that enhance OCDMA-PON performance with dynamic user activity.

Findings

The approximation accurately estimates system BER using a simple mathematical form.

Adaptive code allocation can double transmission rates or significantly reduce power consumption.

Simulation confirms improved performance with adaptive algorithms under realistic traffic conditions.

Abstract

OCDMA systems can support multiple classes of service by differentiating code parameters, power level and diversity order. In this paper, we analyze BER performance of a multi-class 1D/2D OCDMA system and propose a new approximation method that can be used to generate accurate estimation of system BER using a simple mathematical form. The proposed approximation provides insight into proper system level analysis, system level design and sensitivity of system performance to the factors such as code parameters, power level and diversity order. Considering code design, code cardinality and system performance constraints, two design problems are defined and their optimal solutions are provided. We then propose an adaptive OCDMA-PON that adaptively shares unused resources of inactive users among active ones to improve upstream system performance. Using the approximated BER expression and defined design problems, two adaptive code allocation algorithms for the adaptive OCDMA-PON are presented and their performances are evaluated by simulation. Simulation results show that the adaptive code allocation algorithms can increase average transmission rate or decrease average optical power consumption of ONUs for dynamic traffic patterns. According to the simulation results, for an adaptive OCDMA-PON with BER value of 1e-7 and user activity probability of 0.5, transmission rate (optical power consumption) can be increased (decreased) by a factor of 2.25 (0.27) compared to fixed code assignment.