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What is HDSL (High-bit-rate digital subscriber line)?

HDSL stands for high-bit-rate digital subscriber line and is one of the oldest DSL technologies offering speeds of up to 2.3Mbs in both directions. HDSL in the UK is often used in the provision of a 2Mbs and 1Mbs leased line circuits over copper infrastructure.

There are no plans in the UK for any network provider to offer HDSL as a cheap broadband offering. HDSL is a symmetrical DSL service and the UK currently has SDSL for this type of service.

We may see some of the LLU operators start to offer HDSL as a symmetric service because of the distance from exchange problems experienced with SDSL. HDSL has a theoretical distance from exchange capability of 3 Miles .

DSL Variants

  • ADSL 256kbit/s upload, 2Mbit/s download
  • ADSL MAX Up to 800kbit/s upload, 8Mbit/s download
  • ADSL 2 Plus Up to 1Mbit/s upload 24Mbit/s download
  • Annex M Up to 2.5Mbit/s upload 16Mbit's download
  • HDSL 1.5Mbit/s to 2Mbit/s both ways (full duplex)
  • SDSL 2Mbit/s both ways (full duplex)
  • VDSL 13Mbit/s upload, 52Mbit/s download