Types of xDSL

Types of DSL

xDSL, being a familiy of DSL technologies, consists of many types, some of which developed by personal companies for economical profits.

The main DSL types are summerized in this table:

DSL Type Description Data Rate
Downstream;
Upstream Distance Limit Application

IDSL ISDN Digital Subscriber Line (ISDN-DSL) 128 Kbps 18,000 feet on 24 gauge wire Similar to the ISDN service but data only (no voice on the same line)

ADSL Asymmetric Digital Subscriber Line 1.544 to 6.1 Mbps downstream;
16 to 640 Kbps upstream 1.544 Mbps at 18,000 feet;
2.048 Mbps at 16,000 feet;
6.312 Mpbs at 12,000 feet;
8.448 Mbps at 9,000 feet Asymmetric because most of its two-way or duplex bandwidth is devoted to the downstream direction, while smaller bandwidth is used for upstream. Don't need a seperate line for phone voice-conversation.

DSL Lite (or G.Lite) "Splitterless" DSL without the "truck roll" From 1.544 Mbps to 6 Mbps downstream, depending on the subscribed service 18,000 feet on 24 gauge wire The standard ADSL; sacrifices speed for not having to install a splitter at the user's home or business. This saves the cost of what the phone companies call "the truck roll."

HDSL High bit-rate Digital Subscriber Line 1.544 Mbps duplex on two twisted-pair lines (or T1)
2.048 Mbps duplex on three twisted-pair lines (or E1) 12,000 feet on 24 gauge wire
One of the earliest forms of DSL. Can be carried out as T1/E1 service between server and phone company or within a company;
it is symmetrical: an equal amount of bandwidth is available in both directions.

SDSL Symmetric DSL 1.544 Mbps duplex (U.S. and Canada); 2.048 Mbps (Europe) on a single duplex line downstream and upstream 12,000 feet on 24 gauge wire Same as for HDSL but requiring only one line of twisted-pair

RADSL Rate-Adaptive DSL from Westell Adapted to the line, 640 Kbps to 2.2 Mbps downstream; 272 Kbps to 1.088 Mbps upstream Not provided an ADSL technology from Westell in which software is able to determine the rate at which signals can be transmitted on a given customer phone line and adjust the delivery rate accordingly

VDSL Very high Digital Subscriber Line 12.9 to 52.8 Mbps downstream;
1.5 to 2.3 Mbps upstream;
1.6 Mbps to 2.3 Mbps downstream 4,500 feet at 12.96 Mbps;
3,000 feet at 25.82 Mbps; 1,000 feet at 51.84 Mbps A developing technology that promises much higher data rates over relatively short distances.

DSL Type	Description	Data Rate Downstream; Upstream	Distance Limit	Application
IDSL	ISDN Digital Subscriber Line (ISDN-DSL)	128 Kbps	18,000 feet on 24 gauge wire	Similar to the ISDN service but data only (no voice on the same line)
ADSL	Asymmetric Digital Subscriber Line	1.544 to 6.1 Mbps downstream; 16 to 640 Kbps upstream	1.544 Mbps at 18,000 feet; 2.048 Mbps at 16,000 feet; 6.312 Mpbs at 12,000 feet; 8.448 Mbps at 9,000 feet	Asymmetric because most of its two-way or duplex bandwidth is devoted to the downstream direction, while smaller bandwidth is used for upstream. Don't need a seperate line for phone voice-conversation.
DSL Lite (or G.Lite)	"Splitterless" DSL without the "truck roll"	From 1.544 Mbps to 6 Mbps downstream, depending on the subscribed service	18,000 feet on 24 gauge wire	The standard ADSL; sacrifices speed for not having to install a splitter at the user's home or business. This saves the cost of what the phone companies call "the truck roll."
HDSL	High bit-rate Digital Subscriber Line	1.544 Mbps duplex on two twisted-pair lines (or T1) 2.048 Mbps duplex on three twisted-pair lines (or E1)	12,000 feet on 24 gauge wire	One of the earliest forms of DSL. Can be carried out as T1/E1 service between server and phone company or within a company; it is symmetrical: an equal amount of bandwidth is available in both directions.
SDSL	Symmetric DSL	1.544 Mbps duplex (U.S. and Canada); 2.048 Mbps (Europe) on a single duplex line downstream and upstream	12,000 feet on 24 gauge wire	Same as for HDSL but requiring only one line of twisted-pair
RADSL	Rate-Adaptive DSL from Westell	Adapted to the line, 640 Kbps to 2.2 Mbps downstream; 272 Kbps to 1.088 Mbps upstream	Not provided	an ADSL technology from Westell in which software is able to determine the rate at which signals can be transmitted on a given customer phone line and adjust the delivery rate accordingly
VDSL	Very high Digital Subscriber Line	12.9 to 52.8 Mbps downstream; 1.5 to 2.3 Mbps upstream; 1.6 Mbps to 2.3 Mbps downstream	4,500 feet at 12.96 Mbps; 3,000 feet at 25.82 Mbps; 1,000 feet at 51.84 Mbps	A developing technology that promises much higher data rates over relatively short distances.

Next: Shared xDSL protocols