Optimal interception and direction finding of signals in a mobile communication network with directive antennas

For hostile communication environments, a non-centralized mobile communication network with directive/adaptive antennas and Global Positioning System (GPS) has been proposed for the purpose of minimizing the radio exposure and making it difficult for an interceptor to detect the signals. This paper investigates the interceptor's search for the direction-of-arrival (DOA) of the transmitting signal by the method of sequential test and decision when the interceptor also uses a single beam directive antenna. We adopt the dynamic programming algorithm to obtain the optimal action and test to minimize the weighted sum of mean observation number and the average decision error. We also come up with the one-step-look-ahead policy and the maximum a posteriori policy that always chooses the direction with the maximum a posteriori probability and the corresponding costs by building new dynamic programmings. Simplifying an antenna beam shape, the numerical results are presented and compared among policies for a single beam antenna system.