Feeder Planning Methods for Digital Loop Carrier

For most of the twentieth century the subscriber loop network has been dominated by cable technology. Although carrier systems have been applied successfully in the rurad environment 1 for a number of years, it has only been in the very recent past that carrier has gained a foothold in the high-growth suburban environment. However, this situation is changing rapidly, and it is predicted that by the mid-tolate 1980s 50 percent of all loop growth will be served by digital loop carrier (DLC). 2129 To plan for this growth, a detailed study procedure, the Suburban Pair Gain Planning (SPGP) method, was developed. 3 SPGP was designed for general DLC applications where existing Bell System tools, which were designed for rural applications, 4 were not appropriate. The SPGP procedure uses six tabular forms and the existing Bell System planning tool for conventional cable and structure relief--the Exchange Feeder Route Analysis Program (EFHAP)5---to determine a DLC relief plan for a feeder route. SPGP performs the two planning steps necessary for developing a relief plan. First, it determines the appropriate technology for satisfying facility shortages along a feeder route (i.e., cable or DLC). Second, it selects from the possible alternatives an economic implementation plan for the selected technology. Although not optimal, the method has been shown to produce good relief plans on a wide variety of Bell System feeder routes. Since SPGP can be very time consuming to perform, three alternative planning systems have recently been developed for Bell System planning applications.