By: Preethi Ramkumar
Meaning of HDSL - "High-Bit-Rate Digital Subscriber Line" is generally used as a substitute for T1/E1. HDSL is a way to provide full-duplex symmetric data communication at rates up to 1.5 Mbps (2.048 Mbps in Europe) over moderate distances via conventional telephone twisted-pair wires. Traditional T1 (E1 in Europe) requires repeaters every 6000 ft. to boost the signal strength. HDSL has a longer range than T1/E1 without the use of repeaters to allow transmission over distances up to 12,000 feet. It uses pulse amplitude modulation (PAM) on a 4-wire loop.
Unlike ADSL, HDSL is a symmetric method of transmitting data at rates up to 1.5 Mbps in both directions. Because of the symmetric properties, the highest transmission rates can only be supported at lengths of 15,000 foot distances of two or more twisted pair lines. Because of these distance requirements, HDSL is an ideal service for campus environments and digital local loops.
Unlike most other forms of DSL, HDSL is not a typical consumer service, it's used mostly to replace traditional T1/E1 connections, such as connecting PBXes to telco offices. The advantage of HDSL over the Alternate Mark Inversion line coding scheme traditionally used on T1/E1 lines is that it requires about an order of magnitude lower bandwidth to carry the same traffic.
“…High-bit rate Digital Subscriber Line. The earliest variation of DSL. It is used for wideband digital transmission within a business and between the telephone company and a customer. HDSL is symmetrical meaning an equal amount of bandwidth is available in both directions.
” [Auditmypc]
“… The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in both directions. HDSL can carry as much on a single wire of twisted-pair cable as can be carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection. " [Techtarget ]
“…HDSL).Or High-speed Digital Subscriber Line.A transmission technology that can send data at high speeds over regular copper telephone lines.Unlike ADSL, HDSL transmits data at the same speed in both directions, typically 784Kbps.
“ [Computeruser
]
“…Originally developed by Bellcore, high bit-rate DSL (HDSL)/T1/E1 technologies have been standardized by ANSI in the United States and by ETSI in Europe. The ANSI standard covers two-pair T1 transmission, with a data rate of 784 kbps on each twisted pair. ETSI standards exist both for a two-pair E1 system, with each pair carrying 1168 kbps, and a three-pair E1 system, with 784 kbps on each twisted pair.
HDSL became popular because it is a better way of provisioning T1 or E1 over twisted-pair copper lines than the long-used technique known as Alternative Mark Inversion (AMI). HDSL uses less bandwidth and requires no repeaters up to the CSA range. By using adaptive line equalization and 2B1Q modulation, HDSL transmits 1.544 Mbps or 2.048 Mbps in bandwidth ranging from 80ntrast to the 1.5 MHz required by AMI. (AMI is still the encoding protocol used for the majority of T1.)
” [Cisco]
“…High Bit-rate Digital Subscriber Line (HDSL) is generally used as a
substitute for T1/E1. HDSL is becoming popular as a way to provide
full-duplex symmetric data communication at rates up to 1.544 Mb/s
(2.048 Mb/s in Europe) over moderate distances via conventional
telephone twisted-pair wires. Traditional T1 (E1 in Europe)
requires repeaters every 6000 ft. to boost the signal strength.
HDSL has a longer range than T1/E1 without the use of repeaters to
allow transmission over distances up to 12,000 feet. It uses pulse
amplitude modulation (PAM) on a 4-wire loop.
” [Datacomm]
“…An xDSL technology that is symmetric, providing the same amount of bandwidth both upstream and downstream. Due to its speed--1.544 Mbps over two copper pairs and 2.048 Mbps over three copper pairs--telcos commonly deploy HDSL as an alternative to repeatered T1/E1.
” [IndustrialPartner.com]
