Transmission Planning for an Evolving Local Switched Digital Network

This paper examines the major issues associated with transmission planning for an evolving local switched digital network. Three general topics are discussed. First is the need to establish various "receive" levels within the digital switch in order to maintain existing toll loss and level plans. These are required because the integration of the interface between digital switching and transmission facilities has eliminated the channel bank, traditional location of the pad which controls trunk losses. The second area examined is the inherent fourwire nature of a digital switch. In order to maintain existing loss-noise grade of service, a nominal 0 dB cross office loss has been proposed for the switch. The 0 dB loss operation must be attained while experiencing little or no degradation due to singing or near-singing distortion. Acceptable listener echo performance can be obtained in a zero loss office with existing outside plant if an appropriate impedance balance technique, such as segregation of balance networks for loaded and nonloaded loops, is adopted. The third topic is the increasing use of remote vehicles in a local digital network. The basic rule of thumb applied is that transmission performance for customers at a "remote" location should be equivalent to transmission performance for customers at the "host" office. Transmission plans can then be applied accordingly.