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1 — Introduction
1.1
About SHDSL
DSL technology dramatically increases the digital capacity of ordinary telephone
lines (the local copper loops). The speeds obtainable using DSL technology are tied
to the distance between the customer and the Telco central office. The SHDSL
variant of DSL technology is designed for business applications, where high speed
is required in both transmission directions. SHDSL is a rate-adaptive technology,
which, unlike ADSL, cannot share lines with analog telephones.
SHDSL provides symmetric DSL delivery over a single copper pair at rates between
192 kb/s and 2304 kb/s, and a 35% to 50% improvement in distance at a given rate
over traditional symmetric DSL. It is a purely digital technique that uses the lower
band of frequencies to achieve range performance while maintaining the ability to
transmit voice or data services symmetrically.
The narrower frequency band of SHDSL reduces the possibility of interference or
crosstalk when it is deployed in the same binder group or cable as other DSL-based
services, such as ADSL.
Performance varies with loop characteristics, such as length, wire gauge, noise, and
the number and location of bridged taps and gauge changes. Best performance is
obtained on short, clean loops. The SHDSL bit rate can be configured to adapt to the
line conditions.
1.2
Overview of the Speed Touch 591s
The Speed Touch 591s is a device that provides SHDSL access to the ATM core
network from customer premises. It can be managed locally using its own NMTI via
its serial port, or remotely using the 5620 Network Manager. Four versions of the
Speed Touch 591s are available:
•
frame relay
•
V.35/X.21 circuit emulation
•
T1 circuit emulation
•
E1 circuit emulation
Figure 1-1 shows the front view of the Speed Touch 591s, which is the same for all
versions. Figure 1-2 shows the back view of the frame relay and V.35/X.21 circuit
emulation version, and Figures 1-3 and 1-4 show the back views of the T1 and E1
circuit emulation versions, respectively.
1-2
Figure 1-1 Front view of the Speed Touch 591s
Speed Touch
Ethernet
SHDSL
Ethernet
Speed Touch 591s Technical Practices
90-8785-01
Serial
15138
February 2001
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