G9925

G.992.5 refers to the ITU-T recommendation for ADSL2+, formally titled Asymmetric Digital Subscriber Line 2 Plus. It is an extension of the ADSL2 family (G.992.3/4) and is designed to provide higher data rates over existing copper telephone lines. The standard defines the physical layer, modulation, line coding, and management features needed to deliver broadband service using discrete multitone (DMT) modulation and existing copper pairs. It is specified to be backward compatible with earlier ADSL technologies, enabling mixed deployments and smoother upgrades in multi-vendor networks.

Key features of G.992.5 include the ability to achieve substantially higher downstream speeds compared to ADSL2, with improvements made possible by wider use of the available frequency spectrum on the copper pair. It also introduces optional enhancements to improve upstream performance. One notable option associated with G.992.5 is Annex M, which provides increased upstream bandwidth, typically up to about 3.5 Mbps, while maintaining strong downstream performance. The standard supports various annexes and profiles to accommodate different line conditions and regulatory environments.

In practice, G.992.5 has been widely deployed in residential and small-business broadband networks to deliver faster ADSL service over existing infrastructure. While it remains in service in many regions, some markets have shifted toward newer technologies such as VDSL2 and G.fast for higher throughput on short copper loops. ITU-T continues to provide compatibility and coexistence guidance for mixed networks involving G.992.5 equipment and legacy devices.