Optimal Digital Switching Introduction Into the Local Network

This paper describes a local network evolution model for digital switching introduction and the associated algorithm used to determine a feasible optimal network evolution policy. Such a policy is defined by the type, location, and time of placement of digital switches and remote concentrators as well as the homing pattern, i.e., the assignment of concentrators to digital switches. In addition, the evolution policy is characterized by the mode in which the digital switch or remote concentrator is used. Two modes are considered here: 1) overlay where analog equipment is retained at a switching center, growth as well as potentially removed analog lines being served by digital eqmpment; and 2) replacement where analog switches are replaced by digital equipment. The basic cash flows considered in the economic analysis correspond to switching, trunking, and interface costs. Optimality is understood here in terms of minimizing an economic criterion such as the present worth of annual Charges (PWAC) or net present value (NPV). Results obtained using the optimization algorithm in conjunction with a real local telephone exchange network are also presented.