ADSL - Asymmetric Digital Subscriber Line
RADSL - Rate adaptive Digital Subscriber Line
VDSL - Very high Bit rate Digital Subscriber Line
HDSL - High Bit rate Digital Subscriber Line
SDSL – Symmetric Digital Subscriber Line
There are
some characteristics included in all of the DSL technologies. When we consider
the bandwidths of these DSL technologies are depends on the length of the loop
(distance to the central office from the user end).
ADSL
In ADSL there are
many versions. They are ADSL, ADSL2, ADSL2+, The Downlink and Uplink will depend
on this versions. The data transfer rates downstream are much faster than the
upstream data rates in ADSL.
The data rate of ADSL is highly
dependent upon the distance from the Central Office (CO) to the Consumer Premises
(CPE). At a distance of 9000 ft we can achieve 8 Mbps downstream and while at
18000 ft we can only get 1.544 Mbps downstream. ADSL operates at frequencies
above 4 kHz, typically from 30 kHz to 1.1 MHz (Upstream is in the range from 30
kHz to 138 kHz, downstream ranges from 138 kHz, to ~1.1 MHz).
Applications
ADSL is used by home consumers and many small business
owners who mainly want to download files. It is used for carrying voice, data
and video at reasonable rate. We can download large data files, streaming
video, audio, and multimedia from the Internet fast. But, generally, cannot
upload much more than e-mail messages.
RADSL
RADSL
stands for Rate Adaptive Digital Subscriber Line. Rate Adaptive simply means that
the speed of the connection is adjusted to meet the line conditions that each
transmit and receive unit sees. And the upstream is 128kbps – 1Mbps and
downstream 600kbps – 7Mbps.RADSL same as ADSL but the distance will increase
due to adjustment
of streams.
Applications
RADSL is used by home consumers and many small business
owners who mainly want to download files and small uploads. It is used for carrying
voice, data and video at reasonable rate.
VDSL
This is the fastest DSL technology. VDSL
stand for Very high bit-rate Digital Subscriber Line. Not like other DSL
technologies the capacity of the link depends on the service offering and
spectrum regulations. It has 55.2 Mbps of download speed and 16 Mbps Upstream
over single twisted pair. And it has 34 Mbps of download speed and upstream if
the link is symmetric. It uses much wider bandwidth than ADSL IT also depends
on loop condition.
Applications
VDSL is capable of supporting high
bandwidth applications such as HDTV as well as telephone services (VOIP) and high
quality video conferencing.
HDSL
HDSL stands for
High-bit-rate Digital Subscriber Line. The main characteristic of HDSL is that
it is symmetrical. That means 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.
The primary disadvantage of HDSL is
that it requires two twisted pairs of wires to operate, which increases the
deployment cost for service providers. Also, HDSL does not support Plain Old
Telephone Service (POTS) on the same lines as the data.
Applications
It uses for business applications, server
access in large organizations and traditional T1 roles.
SDSL
SDSL
Broadband provides a high-speed internet access service, with matching upstream
and downstream data rates ranging from several speeds from 128kbit/s to 2Mbit/s.
Unlike ADSL, it cannot co-exist with a conventional voice service on the same
pair as it takes over the entire bandwidth. So using your phone line and the
SDSL simultaneously is impossible. It typically falls in price between ADSL and T-1, and it
is mainly targeted at small and medium businesses who may host a server on site.
Applications
Medium
businesses who need to host a server on site, high quality video
conferencing and multiple voice lines.
