ZyXEL P-871 DMT 3/4/5-band, IP-based VDSL Modem 91-004-442002 Folheto

VDSL, the fastest offering of DSL, provides 

significantly higher bandwidth than other DSL 

technologies. VDSL technology, which is similar to 

that of ADSL, uses existing copper wires to deliver 

high-speed data services. 

The major issues with VDSL technology are the line 

codes to be employed, which can be divided into 

either single-carrier or multi-carrier modulation 

schemes. For example, QAM is the most widely used 

form of single carrier systems while DMT, the 

standard line code for ADSL, is the primary form of 

multi-carrier modulation. Both QAM- and DMT-

based systems can be designed for VDSL 

applications. However, DMT modulation 

dynamically adapts the bit rate to conditions on the 

local loop and offers excellent performance even over 

noisy lines. 

To provide VDSL service to end users, Telcos in 

different areas may have different deployment 

strategies unique to their existing and future network 

plans. Ethernet in the First Mile (EFM) is increasingly 

being adopted by service providers and is being 

evaluated by Telcos who have traditionally used ATM 

networks in the past. Without the ATM layer, 

networks become more cost-effective, flexible, and 

efficient. The Prestige 871, which is built without 

ATM, perfectly fits the network demands of today and 

tomorrow. 

ZyXEL's Prestige 871 DMT-based VDSL modem 

supports a complete range of speeds ranging from 

64Kbps to 25Mbps. Symmetric speeds for the Prestige 

871 range up to 25Mbps at 64Kbps increments while 

asymmetric speeds range up to 52Mbps downstream 

and 26Mbps upstream at 64Kbps increments.

DMT 3/4/5-band, 
IP-based VDSL Modem

The Prestige 871 is a DMT (Discrete Multi-Tone)-based VDSL CPE. DMT 

modulation dynamically adapts the bit rate to conditions on the local loop 

and offers excellent performance even over noisy lines. Network 

administrators become free from manually testing lines and from constantly 

adjusting equipment to noise conditions. Both IEEE 802.3ah Ethernet in the 

First Mile (EFM) Task Force and IEEE T1E1.4 Working Group selected DMT 

as its worldwide VDSL line-coding standard. 

The high-bandwidth Prestige 871 allows service providers to simultaneously 

deliver a variety of value-added services, such as broadband Internet access 

and multiple streaming video channels. With the Prestige 871, small to 

medium business users can have much higher bandwidth for both 

symmetric and asymmetric applications while home users can enjoy 

interactive media-rich entertainment which was previously unavailable. 

With VDSL, traditional “copper wire” telecom operators may begin offering 

“triple play” multimedia services such as multiple high-quality digital video 

streams, high-speed internet access, and voice services in a way which 

provides a user experience similar to today’s other existing distribution 

systems (cable, terrestrial, satellite). New revenue can be generated with a 

minimal amount of installation time and expense. 

VDSL can be implemented quickly, even if there is only one phone line per 

tenant. The existing POTS or ISDN services may be kept while adding new 

broadband services.

Due to Ethernet’s relatively low cost, simplicity, flexibility, ubiquity and 

high bandwidth, there has recently been growing momentum in the use of 

Ethernet in access networking. Such trends in access networking make the 

Prestige 871 a perfect solution for EFM applications.