TAILIEUCHUNG - ADSL Residential and SOHO Installations

Asymmetric Digital Subscriber Line (ADSL) deployment to Residential and Small Office/Home Office (SOHO) environments has accelerated the development of appropriate splitters and filters. This Application Note briefly reviews the history and status of these devices, and provides guidelines for their selection and use in typical installations. | Splitters and Microfilters ADSL Residential and SOHO Installations Introduction Asymmetric Digital Subscriber Line ADSL deployment to Residential and Small Office Home Office SOHO environments has accelerated the development of appropriate splitters and filters. This Application Note briefly reviews the history and status of these devices and provides guidelines for their selection and use in typical installations. Previous Deployment Attempts Full-rate ADSL The initial ANSI and ITU from the ITU standards group full-rate ADSL standards stated that ADSL could enable the simultaneous transmission of analog voice and digital data over ordinary copper wire. To add high-speed data transmission however each subscriber line would require the installation of a splitter at the Network Interface Device NID . Figure 1 shows how the voice channel was routed as usual through the existing POTS line while the ADSL channel was distributed through new data wiring such as Category 5 . To separate the lower-frequency analog voice channel at 300Hz 4kHz from the higher-frequency ADSL digital data channel at 25kHz the splitter would need to use simple passive high- and low-pass frequency filters. Subscriber line line ADSL modem ADSL e ADSL ode ADSL oe NID with Splitter POTS ADSL FAX POTS Figure 1. Use of Splitters with Full-rate ADSL Under this plan ADSL data transmission required a truck roll by the service provider to install the splitter and new data wiring. ADSL deployment was consequently viewed as being too costly and too complex. n Splitters Filters in ADSL Installations Subsequently the ITU standards group developed an enhanced ADSL specification which included new features to overcome these perceived barriers. These features included Reduced maximum data rate and frequency bandwidth which lessens the likelihood of encountering problems with reflections or attenuation on the wiring. Fast Retrain which rapidly adjusts ADSL

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