Description
XGPON1, standardized by ITU-T as G.987 series and referenced in 3GPP, is a Time Division Multiplexing Passive Optical Network (TDM-PON) technology. In the 3GPP context, it is specified as a trusted, non-3GPP access network type that can interconnect with the 3GPP core, particularly for Fixed Mobile Convergence (FMC) and as a transport option for network nodes. The system comprises an Optical Line Terminal (OLT) at the service provider's central office and multiple Optical Network Units (ONUs) or Optical Network Terminals (ONTs) at the customer premises or cell site. These are connected via a passive optical splitter, which allows a single fiber from the OLT to serve multiple endpoints, making it a cost-effective shared medium.
The technology operates using different wavelengths for downstream and upstream traffic to avoid interference. Downstream traffic (from OLT to ONUs) is broadcast at a wavelength near 1577 nm, with each ONU selectively reading data destined for it based on encrypted addressing. Upstream traffic (from ONUs to OLT) uses Time Division Multiple Access (TDMA) on a wavelength near 1270 nm, where each ONU is allocated specific time slots by the OLT to transmit its data, preventing collisions. The physical layer uses NRZ line coding. XGPON1 supports a logical reach of up to 60 km and a split ratio of up to 1:256, allowing wide coverage from a single OLT port.
Within the 3GPP architecture, XGPON1 is integrated as a reliable, high-bandwidth wireline access. For fixed-mobile convergence, a Residential Gateway (RG) incorporating an XGPON1 ONT can connect to both the 3GPP EPC/5GC for mobility services and to IMS for fixed-line voice and IPTV. As a transport technology, it can provide backhaul connectivity for 4G eNodeBs and 5G gNBs, connecting them to the core network with high capacity and low latency, forming part of the mobile network's transport stratum.
Purpose & Motivation
XGPON1 was developed to meet the exploding demand for higher bandwidth from both residential broadband users and mobile networks. Its predecessor, GPON (G.984), offered 2.5 Gbps downstream and 1.25 Gbps upstream, which was becoming a bottleneck for high-definition video, cloud services, and the increasing bandwidth needs of mobile backhaul as LTE networks deployed. The primary motivation was to future-proof fiber access networks by providing a tenfold increase in downstream capacity.
3GPP's inclusion of XGPON1, starting in Release 10, was driven by the strategic initiative of Fixed Mobile Convergence (FMC). The goal was to standardize how high-performance wireline access networks, like PONs, could be seamlessly integrated with the 3GPP mobile core. This allows operators with both fixed and mobile assets to offer unified services, share infrastructure costs, and use the fiber network as a high-quality transport layer for mobile traffic. XGPON1 solved the problem of providing a standardized, cost-effective, and high-capacity 'last mile' and 'backhaul mile' solution that could support the stringent requirements of future mobile networks, including low latency and high availability for features like carrier aggregation and cloud RAN.
Key Features
- Asymmetric bandwidth: 10 Gbps downstream / 2.5 Gbps upstream line rate
- Operates on separate wavelengths (1577nm down / 1270nm up) for full-duplex communication
- Supports high split ratios (up to 1:256) and long logical reach (up to 60 km)
- Utilizes TDMA for upstream transmission to manage shared medium access
- Strong encryption (AES-128) for downstream broadcast security
- Defined as a trusted non-3GPP access type for integration with 3GPP core networks
Evolution Across Releases
Initially referenced XGPON1 (ITU-T G.987) as a high-capacity wireline access technology for Fixed Mobile Convergence. Defined architectural principles for integrating this PON technology as a trusted non-3GPP IP access connecting to the EPC, enabling unified policy and authentication.
Defining Specifications
| Specification | Title |
|---|---|
| TS 24.229 | 3GPP TS 24.229 |