Joint mode identification and localisation improvement of over-the-horizon radar with forward-based receivers

Target tracking of over-the-horizon radar (OTHR) suffers from the effect of multi-path propagation. To date, all corresponding tracking methods depend on the precondition that the ionospheric heights should be available via the ionosondes. However, the ionosondes cannot be arbitrary deployed, for example, in sea area or hostile zone. This study presents the problem of sensor fusion of OTHR and a set of forward-based receivers (FBRs) for online mode identification of OTHR echoes, estimation of virtual ionospheric heights and localisation improvement. This fusion problem faces two challenges. The first is `multi-path´, as a kind of uncertainty existing in both the forward propagation of FBRs and the forward/backward propagation of OTHR. The other is `coupling´, representing the complexity that the mode/parameter identification and estimation couple each other. Here the joint optimisation scheme of identification and estimation is proposed mainly including four sub-processes: coordinate mapping with target height, joint identification and estimation of FBRs, mode identification of OTHR and localisation improvement. The simulation shows that propagation/clutter modes can be identified effectively and ionospheric heights are estimated without the help of ionosondes. Meanwhile, target state including the target height is estimated and the localisation accuracy is further improved due to sensor fusion.