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To: Eric Goethals who wrote (4553)	10/30/1998 7:31:00 AM
From: bill c.	Read Replies (1) \| Respond to of 9236

Eric, During the discussions over the last few months, it seems that many compromises where made to get G.Lite done. I've located material that talks about the compromises with trellis coding, 1-bit constellation, efficient framing and "bit-swapping being optional" in G.Lite. It seems that trellis coding helps in the On/Off-Hock, but it wasn't added to the G.Lite standard. It would surprise me if any company got a patentable solution into the standard during this first cut....until later. Here is some of that Telecommunications article: Splitterless ADSL. Because its installation is most similar to traditional analog modems, the operation of both ADSL and voiceband services on a single line without any POTS splitters is the most desirable deployment option. However, without splitter functionality, these G.lite systems must employ capabilities such as power cutback to minimize audible noises created from ADSL frequencies intermodulating down into the voiceband. The POTS Splitter isolates ADSL from the home wiring. Splitterless solutions eliminate the Pots splitter, adding to line variability. A distributed splitter lowers complexity in terms of use, but raises the system's complexity. In addition, these G.lite systems must utilize a fast retraining method to dynamically adapt the data rate down when one or more telephones are taken off-hook --assuming that the customer is not at the edge of the service area and the system can maintain the connection during an off-hook condition. Since off-hook conditions and power cutback lower reach and performance, solution providers are considering ways to extend the reach of G.lite through better spectrum utilization (echo cancellation), improved equalization techniques, and coding gain algorithms such as Reed-Solomon forward error correction and trellis encoding. However, implementation complexity and costs must be weighed against the benefit achieved by the additional processing required. Another way to ensure a stable connection while minimizing the interaction of POTS and ADSL signals is to simply not use the two services simultaneously (like today's analog modems). With this approach, customers order a second telephone line and dedicate it to ADSL use. While this may not completely eliminate the interaction between POTS and ADSL, as there may still be interference between the lines, it does diminish interaction significantly. Distributed Splitter. A second option is to ship with the ADSL modem several small, in-line POTS splitters, which the customer plugs into each telephone in the house. This approach provides a significant amount of protection and addresses a number of the challenges listed above. However, it introduces several new problems, including difficult installation in wall-mounted phones, the reduction of ADSL performance due to having a number of filters in parallel, and tough manufacturer decisions on how many filters to ship with the modem. Despite these difficulties, the distributed splitter approach represents a compromise between a solution delivering high-quality POTS and excellent ADSL performance/ reach, and avoiding the need for professional ADSL installation. telecoms-mag.com