Turbo-Loop: a rate-adaptive digital subscriber loop (RA-DSL) for advanced ISDN access applications

The authors report the implementation of prototype hardware and control protocols which will automatically maximize the transmission rate of individual subscriber loops. The result is a rate-adaptive digital subscriber loop (RA-DSL) technology called Turbo-Loop, which makes possible new applications such as a simple form of bandwidth-on-demand and a strategy for increased utilization of existing copper, while bridging the gap to having fiber in the loop. Results predict that Turbo-Loop can deliver 1.5 Mb/s up to 2 km, reaching subscribers to 10 km and 80 kb/s, and can provide a potential increase of 400% to 600% in the total utilization of existing copper access networks. The authors describe the hardware and software design of the RA-DSL prototype and report results of adaptive transmission rate experiments on actual copper loops. Also described are simulation studies which predict the ultimate performance of a fully developed design based on the Turbo-Loop principle