Message Passing-Based Moving Target Localization in Multistatistic Systems With Unknown Time and Frequency Offsets

It is challenging to localize a moving target using a multistatic system with unknown time delay (TD) and Doppler shift (DS) measurement offsets caused by asynchronization between transmitters and receivers. To address this issue, we develop a low complexity iterative message passing localization method using TD and DS measurements. In particular, to handle the unknown offsets, we formulate a joint estimation problem of target position, velocity and unknown offsets based on the maximum likelihood (ML) principle, which is nonlinear and nonconvex. Then, by transforming the objective function and relevant constraints into a product of multiple local functions, a message passing algorithm is developed. To handle the complex local functions in message updates, belief propagation (BP) and variational message passing (VMP) are combined. Comparisons with state-of-the-art methods demonstrate that, with much lower complexity, the proposed method delivers superior performance.