DSL (Digital Subscriber Line, Digital Subscriber Line) is the copper telephone lines for the transmission medium of transmission technology portfolio, which includes the HDSL, SDSL, VDSL, ADSL and RADSL and so on, commonly known as xDSL.Their main difference is reflected in the signal transmission speed and distance as well as uplink and downlink with different rates of the different symmetry of these two aspects.
HDSL and SDSL supports symmetric T1/E1 (1.544Mbps/2.048Mbps) transmission.HDSL which the effective transmission distance of 3-4 km, and requires two to four pairs of twisted-pair copper telephone lines; SDSL maximum effective transmission distance of 3 kilometers, only one pair of copper wires.In comparison, the symmetric DSL connection point is more applicable to enterprise applications such as file transfer, video conferencing, sending and receiving data roughly corresponding work.Compared with non-symmetric DSL, symmetrical DSL market is much less.
VDSL, ADSL and RADSL a non-symmetric transmission.VDSL technology is one of the fastest xDSL technology, in a pair of twisted-pair copper telephone line, upstream data rate of 13 to 52Mbps, the downlink data rate of 1.5 to 2.3 Mbps, but only in VDSL transmission distancea few hundred meters, VDSL can be fiber to the home of a cost-effective alternative to the current Shenzhen VOD (Video on demand) is achieved using this access technology; ADSL support in a pair of copper wires to 640Kbps uplink rate1Mbps, 1Mbps downlink speed to 8Mbps, the effective transmission distance of 3-5 km within; RADSL can provide the same speed range and the ADSL, but it can be twisted-pair copper wires according to the quality and transmission distance dynamically adjust the distanceuser's access speed.These characteristics make it RADSL RADSL be used for high-speed Internet surfing, video on demand (IAV), a remote local area network (LAN) to access the ideal technology, because in these applications users to download information more often than on the information contained in (send command)much more.
ADSL access high performance and low cost can do this, with ADSL access technology than other access technology has its unique technical advantages are inseparable.