Radionavigation system power level optimization for reduced operating cost

Radionavigation system coverage, or violability, typically depends on the effective radiated power maintained by the system transmitting stations. A desired level of system availability can be maintained by reducing station radiated power below the maximum levels. An efficient algorithm referred to as SPLAA (station power level assignment algorithm) has been developed for determining the power levels of the Omega navigation system stations which minimizes system operating cost while maintaining a desired system availability index. For Omega, the relationship between system availability and station power levels is quite complex, depending on time/space-varying signal coverage, station reliability, receiver reliability, and geographic usage patterns. Because of this complex relationship, a workstation known as PACE (performance assessment and coverage evaluation) is used by the Coast Guard´s Omega Navigation System Center to predict and display system availability. A straightforward calculation of system availability for all possible power levels (at each of the eight transmitting stations) using PACE would require several thousand years of execution time on a PC. By comparison, SPLAA computes the optimal mix of station power levels for a given hour/month scenario in about 10 minutes on an i486/33 PC. To attain this speed with the required accuracy, SPLAA enlists a combination of analytical, rule-based, and efficient exploratory schemes. The paper traces the evolution of SPLAA and briefly describes the algorithm structure. Sample results are presented for representative operational scenarios