Technical Control of the Digital Transmission Facilities of the Defense Communications System

Abstract

As an aid in evaluating technical control techniques, an emulation facility that automatically performs the status monitoring, performance assessment, and fault isolation technical control functions as they apply to a future, predominantly digital Defense Communications System (DCS) has been developed. This emulation facility is a multicomputer system which automatically monitors and isolates faults for digital transmission equipments (power generators, RF distributions, digital radios, second level multiplexers, first level multiplexers, submultiplexers, and key generator units). The status monitoring and performance assessment functions are performed by two processors, the adaptive channel estimator (ACE) and an LSI 11/03, the composite being referred to as the CPMAS-D unit. When the software residing in the CPMAS-D unit detects a monitor point transition (alarm to/from nonalarm), it transmits the monitor point information to the CPMAS emulator, a PDP 11/60 minicomputer. These messages, called exception reports, enable the CPMAS emulator to perform its prime mission: fault isolation. A unique fault isolation algorithm has been developed for test with this emulation facility. The algorithm consists of three discrete steps. First, the equipment alarms are mapped into their effect upon each transmission path (link, supergroup, group, or channel). Second, the stations with the faulty equipment are located by deleting the impact of sympathetic alarms. Third, the faulty equipment is identified using the equipment alarm status. Testing of the fault isolation algorithm is enhanced by an emulated network consisting of up to 16 stations, 2048 equipments, and two nodal control areas. Monitor point simulators and T1-4000 multiplexers, which provide simulated and real inputs to two CPMAS-D units, are also part of the emulation facility. Technical control terminals are provided to evaluate man-machine operation in an automated technical control environment. An adaptive channel estimator (ACE) field test was conducted at the Rome Air Development Center (RADC) test facilities so that the ACE development unit could be evaluated as a means of assessing performance of high-speed digital radio transmission systems. Also, the fault isolation algorithm was tested using the previously described emulation facility. The test data and subsequent technique evaluations are discussed in this paper.