Dynamic bandwidth allocation in time division multiplexed passive optical networks: a dual-standard analysis of ITU-T and IEEE standard algorithms

In the last 25 years, operators have effectively established passive optical networks (PONs), catering to around 1 billion users and earning income surpassing 8.5 billion Euros. Major standardization bodies like IEEE and ITU-T have introduced several PON solutions to mitigate last-mile broadband access and bandwidth allocation problems for end users. In this case, a compelling dynamic bandwidth allocation (DBA) algorithm can provide contention-free access (fairness) to the end user for the upstream channel with high bandwidth efficiency, minimal upstream delays, and scalability. This, in turn, boosts network quality of service (QoS) and allows operators to accommodate more users (revenue). This article examines the evolution of time-division multiplexed PON solutions such as A/BPON, EPON, GPON, XGPON, 10G-EPON, and NG-PON2 under both IEEE and ITU-T standards, addressing their approaches to DBA challenges. We analyze the bottlenecks and compare reported works based on their key strengths/applications, weaknesses, and operational mechanisms, as well as highlight their quantitative insights. We also discuss next-generation PONs (NG-PONs) and their emerging applications, such as 5G/6G fronthaul architecture in the cloud radio access network (CRAN) environment, fiber to the room (FTTR), and industrial PON, with a focus on DBA designs. Finally, the article summarizes current progress, highlights challenges, and proposes future research directions for developing more efficient DBA algorithms for these new applications.