G.Lite (ITU G.992.2)
Due to the problem of POTS splitters, the ITU ratified ITU G.992.2 for splitterless service. This offers the services of ADSL, but at a lower speed. It also is intended to ease installation because a POTS splitter typically requires professional installation.
Even though G.Lite is a splitterless option, it still provides POTS service by reducing the transmission power used to send digital information when the modem detects that the analog telephone handset goes off-hook, either for a voice or fax session. Because there is a new power level used to modulate the line, a fast-retrain procedure occurs with the ATU-R to establish proper power levels. This results in a slight cessation of service of about 1 to 2 seconds while the retraining is in process. After retraining, digital service will operate a bit more slowly, but (hopefully) no interference occurs with the analog conversation. How much slower depends on the amount of interference incurred with the analog service. When the analog handset goes back on-hook, the digital service is retrained up to its maximum speed.
In addition to being consumer-installable, G.Lite supposedly has a longer reach than full-rate ADSL and consumes much less power than full-rate ADSL. This reduction in power consump-tion provides much greater port density at the telco site and makes it possible to put telco equipment into remote terminals and loop carrier systems.
G.Lite also simplifies inside wiring in the home. With ADSL, there should be no analog telephones connected to the wire that connects the POTS splitter to the ATU-C. With G.Lite, phones can be placed anywhere in the home. Therefore, for ADSL, professional installation may be required for both the POTS splitter and the new inside wiring dedicated to data use. G.Lite obviates both reasons for professional installation. However, each telephone in a home with G.Lite may need a small microfilter for some added isolation between the G.Lite service and the telephone service. There is the marketing question of how many of these microfilters need to be sold with the ATU-R for retail distribution.
Table 4-4 compares full-rate ADSL and G.Lite.
Despite its relative ease of installation, a splitterless option may not be popular in countries where the telephone company is still be responsible for internal wiring (which is not the case in the United States). Because those telcos (in France and Germany, for example) are required to make the truck roll in any case, going splitterless offers no installation savings and has the marketing problem of reduced speed. Also, in Europe, local loops tend to be shorter in distance than those in the United States, so their loops tend to be more qualified for higher speeds. This is perhaps why Deutsche Telekom will proceed with full-rate DSL.