TABLE OF CONTENTS With the growth of telecommunications networks, increasing pressure is being placed on traditional maintenance methods. Trunk circuit testing on an individual basis is widely used; however, this approach requires that circuits are taken out of service with an ensuing loss of revenue and considerable inconvenience to the customer. It is, therefore, usually restricted to periods of low traffic activity and hence does not assess network performance under its most stringent operating conditions or on a continuous basis.
With FDM carrier systems still carrying the majority of long-haul traffic, ranging in capacity from a few voice channels to over 100,000 channels on a signal composite cable, this heavy concentration of traffic provides convenient monitoring points for network surveillance. Automatic monitoring can make a major contribution to the performance of a network by providing direct assessment of traffic and transmission-system performance on such long-haul routes. Operationally, automatic measuring systems can provide the dual benefit of continuous performance monitoring and fast, accurate fault location.
By making measurements of pilots, channels, carrier leaks, and so on, using an SLMS at various locations in a network, it is possible to monitor performance on a per-channel basis while simultaneously checking the operation of the associated multiplex and transmission equipment. System monitoring of this kind puts some special constraints on the design of an SLMS, as is described in some detail later on in this chapter.
With an SLMS and suitable equipment for test-point access and system control, reliable network monitoring can be provided...
