Netopia R7100-C User Reference Manual

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Netopia R7100-C User Reference Manual Manual pdf 241 page image

About SDSL G-1AAAAppppppppeeeennnnddddiiiixxxx GGGGAAAAbbbboooouuuutttt SSSSDDDDSSSSLLLLThe Netopia R7100 SDSL Router (Symmetric Digital Subscriber Line) technology uses standard copper phonelines to send a digital signal between two points. Because the signal stays digital and does not go through thepublic switched telephone network SDSL allows a much faster data connection. Offering the same data rate inboth directions, the SDSL Router provides symmetric bandwidth needed for business applications such ase-mail, file transfer, web browsing, corporate Intranet access, web hosting, and remote LAN access. The SDSLRouter improves businesses productivity and competitiveness by providing cost effective, high speed Internetaccess over ordinary copper phone lines. SDSL creates a point-to-point link over a single copper wire sobandwidth isn't shared by anyone outside the remote office.SDSL will allow you to connect to the Internet at a minimum of 128Kbps bi-directional, up to 1.568Mbps. YourLAN will constantly be connected and you will not have to dial into the Internet. DSL utilizes more of thebandwidth on copper phone lines than what is currently used for plain old telephone service (POTS). By utilizingfrequencies between 26 kHz and 1MHz, DSL can encode more data to achieve higher data rates than wouldotherwise be possible in the restricted frequency range of a POTS network (up to 4 kHz). In order to utilize thefrequencies above the voice audio spectrum, DSL equipment must be installed on both ends and the copperwire in between must be clean enough to sustain the higher frequencies for the entire route. This means thatbandwidth limiting devices such as loading coils can prevent DSL from being used.SDSL is more appropriate for business users because bandwidth is the same in both directions. AsymmetricDSL Service is better suited for individual consumers who generally require more speed in the download stream(web surfing) with little data going in the other direction.Netopia's SDSL router has fewer implementation issues than ADSL routers. It uses 2B1Q line encoding (sameas T1 or ISDN) and this doesn't produce the same noise and interference as ADSL, which uses DMT or CAPencoding. In some cases the phone company may refuse to provision ADSL service due to crosstalk with othervoice and data lines bundled in the same cable.Historically, HDSL has been primarily used to deploy repeaterless T1 and E1 services in areas where repeaterinstallation was costly or problematic. Today there are over 300,000 such lines installed in the U.S. While theseimplementations typically require two or three pairs of copper wire, a new form of HDSL has emerged that usesa single pair of copper (i.e., SDSL) but still delivers up to 2 Mbps of symmetrical bandwidth depending on looplength and quality.Single pair HDSL (S-HDSL or SDSL) offers workable solutions to several of the challenges faced today by itsless mature cousin, ADSL. Both technologies will have their place in the service provider's network, and thatwill be based on the specific customer applications that are supported over the last mile connection. However,SDSL offers some very attractive solutions to today's main drivers—remote data connectivity for corporate orInternet applications.Because SDSL uses the same technology as the market-proven HDSL, it benefits from the maturity of HDSLimplementations. For example, SDSL silicon chipsets cost about a third of that for ADSL chipsets. The lower perline cost means service providers can launch high speed data services sooner rather than later.Higher speed ADSL solutions can then be brought on line when they are more cost effective.The maturity of SDSL silicon also includes an advantage in the area of power consumption. Where most ADSLimplementations require 6-8 watts of power, current SDSL modems consume 4 watts of power or less.