Dynamic Scan Scheduling Specification

1. Dynamic Scan Scheduling Specification Bruno Dutertre System Design Laboratory SRI International E-mail: bruno@sdl.sri.com

2. Dynamic Scan Scheduler External Parameters Performance Requirements Assessment Schedule Construction Scan Schedule Signal & Data Processing EW Receiver Detected Pulses Detected Emitters • Assessment function: • determines when rescheduling is required • specifies requirements for the new schedule • Schedule-construction function: • generates a schedule that meets the requirements • under real-time constraints

3. DSS Specification • Objective: • Determine requirements for the schedule-construction function (on a single platform) • Key Issues: • Schedule representation • Metrics for expressing performance requirements and measuring schedule performance

4. Schedule Representation • Strongly periodic schedules: • Defined by pairs dwell time/revisit time for each frequency band • Feasibility results show that this is too restrictive • Pattern-based schedules: • Defined by a basic pattern repeated periodically • The pattern describes a finite list of successive dwell intervals Dwell interval Pattern

5. Performance Metrics • Two emitter types: • Search and track radars produce successive illuminations (rotating beams) • Missile radars continuously illuminate their target • In both cases, detection and tracking require intercepting a minimal number M of pulses in a single dwell • Good performance requires a high probability of intercepting M or more pulses in dwell intervals

6. Periodic-Illumination Emitters • First Metric: Coverage • The probability of intercepting at least M pulses from a single illumination: , m : emitter parameters L, n, A: parameters derived from the schedule pattern This gives an estimate of how well the schedule does at detecting an illumination from an emitter not already detected

7. Extensions of Coverage • The previous metric can be generalized to • Coverage with respect to successive illuminations (probability of detecting an emitter after a few illuminations) • Relative coverage: estimate of how good the schedule is for tracking already detected emitters (uses information about the likely time of occurrence of future illuminations) • Probabilistic coverage: to deal with emitters whose characteristics are not known with exactitude, but with some probability distribution • All these metrics can be computed from the schedule pattern

8. Metric for Continuous Emitters • Requirements for continuous emitters: • A good schedule must minimize detection delays • Associated metric: • Expected delay between the activation of the emitter and the interception of at least M pulses in a single dwell:  : pulse repetition interval of the emitter L, n, : parameters derived from the schedule pattern

9. Global Performance Constraints • We can partition emitters in two classes: • Emitters already detected (that need to be tracked) • Emitters likely to be present (that need to be searched for) • This gives three sets of constraints on the scan schedule: • Tracking constraints: maximize the relative coverage for each tracked emitter • Searching constraints for continuous emitters: minimize the expected detection delay for each probable emitter • Searching constraints for periodic emitters: maximize coverage for each probable emitter

10. Conclusion • New results: • Analysis of scan-schedule performance • Metrics for evaluation of pattern-based schedules • Requirements for a schedule-construction algorithm • Future work: • Algorithm development and experimentation • Extension to the multi-platform case