DSL Technology

Presented by:Eng. Karam Al-sofy

What is DSL? Digital Subscriber Line (DSL) is a technology that

provides digital data transmission over the existing wires of local telephone network.

DSL (Eng. Digital Subscriber Loop) - a digital subscriber loop, the family of broadband access to the Internet technology

DSL service is delivered simultaneously with regular telephone on the same telephone line. This is possible because DSL uses a higher frequency.

Cont..,It assumes that digital data does not require changing into analog form and back to digital form.Digital data is transmitted directly to the computer, as is, exploiting the maximum bandwidth and the wide range of unused frequencies available in the existing copper wire of telephone networks for high-speed broadband communication. Moreover, the signal can also be separated, if one chooses, so that some of the bandwidth is used to transmit an analog signal for simultaneously using the telephone line for voice.

How it worksOver the Wire: You are connected to another ADSL modem which also has a POTS splitter, which separates voice calls from data.

Telephone Calls: Voice calls are routed to the phone company's public switched telephone network (PSTN) and proceed on their way as usual.

Internet Requests: DSL Access Multiplexer links many ADSL lines to a single high-speed asynchronous transfer mode (ATM) line, which in turn connects to the Internet.

Back at You: The requested data is retrieved from the Internet and routed back to you.

Basic DSL network

DSL DevicesDSL is actually not a physical line, but a modem pair. One DSL modem is located at the customer premises (Customer Premise Equipment or CPE) and another DSL Access Multiplexer (DSLAM) is at the Central Office (CO).

Cont..,These two modems create a Digital Subscriber Line or DSL. DSL modems transmit data at the rate of up to 160 Kbps over copper lines, up to 18000 feet.DSL Modem or DSL Transceiver, as it is also referred to as, is connected to the customer’s computer via USB or a 10-Base T connection.DSLAM at the Central Office or the Access Provider is the one that actually makes the DSL happen . It accepts connections from various customers and aggregates them into a single high capacity connection to the Internet. In addition, the DSLAM also does IP routing and Dynamic IP address assignment.

TYPES OF DSL ADSL(Asymmetric Digital Subscriber Line)

Most home and small business users typically use ADSL.The transfer of data from the internet to PC is much faster than the transfer from PC to internet.

Downstream speeds for ADSL range from 1.59 Mbps, while upstream speeds are up to 1.5 Mbps, for a distance of 18,000 feet from the service providers premises.SDSL(Symmetric Digital Subscriber Line )

Does not allows to use the phone at the same time. But internet speed of sending and receiving data is same.

Working of A Simplified ADSL

HDSL(High bit/data rate Digital Subscriber Line)HDSL was the first DSL technology that used a higher frequency spectrum of copper, twisted pair cables.

ISDN DSL(Integrated Service Digital Network)Symmetric data rates of up to 144 kbps using existing phone lines.Capable of using the same modem or terminal adaptor used for ISDN and is always available.

RADSL(Rate Adaptive Digital Subscriber Line)

RADSL it is automatically adapts the speed depending on the quality of the signal. Modern ADSL technologies are usually RADSL technologies. The Adaptive version of the asymmetrical access, called RADSL (Rate Adaptive DSL), allows for automatic adjustment of co-operating modems to the capacity available in the transmission route at the given moment. It is the most effective form of transmission via existing information channels with dynamically changing capacity, even during usage of a given telecommunication service.

VDSL(Very high-bit-rate Digital Subscriber Line)

VDSL technology can be recognized as development of ADSL standard and, at the same time, compatible with services based on SDH or ATM technologies.It Provides high speed internet connection but works only over a short distance.VDSL permits transmission in both asymmetrical and symmetrical mode, guaranteeing throughput up to 56 Mbit/s in the asymmetrical mode and 26 Mbit/s in each direction in the symmetrical mode.

Comparative study of different DSL flavors

ADVANTAGES DSL service is always ON and we can still use

the phone for voice calls.

 Broadband speed is much faster than dial up service.

Fixed monthly billing, regardless of time usage.  Digital data is directly transmitted to computer

as digital data which uses much wider bandwidth for transmitting

DISADVANTAGES

DSL has one significant downside: 

As you move away from the central office , the connection becomes slower.

  This results is distortion of signal.

Conclusion It is highly likely that xDSL will become

widely adopted particularly among high-speed Internet "power users" as well business requiring fast access to various networks, provided naturally that the prices come down.

xDSL technology offers a viable interim solution to the bandwidth problem while fiber optic cables are being installed.

Thank you.......…..….