ADSLADSL2

ADSL, short for asymmetric digital subscriber line, is a family of broadband technologies that use existing copper telephone lines to deliver high‑speed data while preserving voice services. ADSL traffic is carried on higher frequency channels than voice, and the downstream channel generally provides higher bandwidth than the upstream channel, hence the term “asymmetric.” Data is transmitted using discrete multitone modulation (DMT), and the line is typically split from voice with filters or splitters to prevent interference.

ADSL2 and ADSL2+ are extensions of the original ADSL standard designed to improve speed, reach, and efficiency over copper pairs. ITU-T standards define these technologies as G.992.3 (ADSL2) and G.992.5 (ADSL2+), with ADSL2+ offering a broader high‑frequency spectrum than ADSL2. These enhancements allow higher downstream data rates and better performance on longer loops, as well as improved error correction and noise tolerance.

Typical performance varies with line length and condition. The original ADSL commonly delivers up to about 8 Mbps downstream and around 1 Mbps upstream on many installations. ADSL2 can push downstream toward roughly 12 Mbps on shorter loops, with similar or modest upstream improvements. ADSL2+ can reach as high as about 24 Mbps downstream on short copper, with upstream speeds generally in the 1–3 Mbps range. In practice, speeds depend strongly on loop length, line quality, and carrier provisioning.

Deployment of ADSL and its successors remains widespread in areas where fiber or high‑speed technologies are not yet available. They continue to coexist with newer broadband options, offering a cost‑effective upgrade path on existing copper infrastructure.