PDF of this tutorialThese are the two primary xDSL standards over which much debate has ensued. Although the debate continues, the real action is taking place in the marketplace. CAP demonstrated a clear lead in getting product to market. Chips were available in quantity, and they worked. Numerous products that incorporated these chips are installed in a number of locations by service providers. Standards and interoperability issues between vendors and implementations are now being addressed.
DMT, on the other hand, has been in the standards arena for some time and continues to evolve. It is now considered a standard by a number of service providers. This technology featured some innovations that were not originally in the CAP feature set such as rate adaptation. On the other hand, the chips are just now finding their way into products. Trial activities are only now beginning, and advanced chip sets that match the features of CAP chips are now being promised for 3Q97.
The issue is which will win the market. The service providers who are building the xDSL network will select the technology that meets their needs. Many vendors are offering products that use either technology. Some new chips are being announced that allow adaptation between either technology. The point here is that the technology of xDSL chips is not a roadblock to deployment. Either appears to work well and true interoperability remains in the future much like mid-span meets for SONET equipment.
