A Markov-chain model for sensor scheduling in electronic support

In electronic support, receivers must maintain surveillance over the very wide portion of the electromagnetic spectrum in which threat emitters operate. A common approach is to use a receiver with a relatively narrow bandwidth which sweeps its centre frequency over the threat bandwidth to search for emitters. The sequence and timing of changes in the centre frequency constitute a search strategy. The search can be expedited if there is intelligence about the operational parameters of the emitters that are likely to be found. However, it can happen that the intelligence is deficient, untrustworthy or absent In this case, what is the best search strategy to use? We propose a random search strategy based on a continuous-time Markov chain (CTMC). When the search is conducted for emitters with a periodic scan, we show that there is an optimal configuration for the CTMC. It is optimal in the sense that the expected time to intercept an emitter approaches linearity most quickly with respect to the emitter's scan period. A fast and smooth approach to linearity is important since other strategies can exhibit considerable and abrupt variations in the intercept time as a function of scan period. In theory and in numerical examples, we compare the optimum CTMC strategy with other strategies to demonstrate its superior properties.