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high bitrate digital subscriber line (HDSL)

High BitrateDigital Subscriber Line (HDSL) is a transmission method for full- duplex transmission with transmission speeds of 1.544 Mbit/s on T1 lines or 2.048 Mbit/s on E1 lines. Like the other xDSL methodsADSL (asymmetric), SDSL (symmetric) and VDSL (very high speed), HDSL can be transmitted on conventional UTP cables between the local exchange and the customer, but two or three copper pairs are required.

This transmission method was developed by Bellcore for T1 lines and allows bridging of up to 5 km. HDSL is ideal for connectingprivate branch exchanges, it offers an alternative for local frame relay and can replace amplifier-supported T1 or E1 lines. Carrierless Amplitude-PhaseModulation( CAP) has been standardized as the line coding.

DSL variants

DSL variants

There are several HDSL variants such as 1- DA-HDSL, 2-DA-HDSL, CAP-HDSL, 2B1Q-HDSL and Multirate Digital Subscriber Line( MDSL), which are constantly being developed to increase coverage and to open up interfaces for new applications. ANSI has finalized a new specification that is based on a copper twisted pair and is expected to have the same range as the familiar twisted pair-based HDSL.

The enhanced version is designated HDSL2 for clear differentiation and is intended to replace the previous 2B1Q-HDSL version. HDSL2 was standardized by ANSI for bit rates of 1.544 Mbit/s and operates with an OPTIS (Overlapped PAMTransmission with Interlocking Spectra) line code. This system operates with a twisted pair and uses the 2B1Q line code. Based on this, the European Telecommunications Standards Institute( ETSI) has defined a system that transmits the European bit rate of 2.048 Mbps. This method uses a sixteen-stage PAM process with trellis coding and with asymmetry of the two transmission directions.

The fourth generation of HDSL is called HDSL4 and has a distance range that is about 30% larger than HDSL2. This HDSL variant operates with two twisted pairs, whereas HDSL2 uses one twisted pair.

Informations:
Englisch: high bitrate digital subscriber line - HDSL
Updated at: 25.02.2013
#Words: 303
Links: transmission, method, duplex transmission, transmission system 1 (WAN) (T1), E1 line (E1)
Translations: DE
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