A RELNAV enhancement for reducing cumulative position error in Link-16 without GRU

Position information is important for conducting battlefield missions. GPS generally enables allies to identify positions. RELNAV defined in Link-16 is used for JU in the air to estimate its position as an auxiliary navigation system of GPS. However, there is a critical problem in RELNAV. To operate accurately, RELNAV requires the presence of ground reference units that help to estimate the positions of JUs operated by RELNAV. However, guaranteeing the constant presence of ground reference units in a battlefield is difficult. If the presence of ground reference units is not assured, JUs operated by RELNAV have a critical problem in maintaining high positional quality. They depend on inertial navigation systems that can accumulate positional errors with time. In this environment, such errors will become large, and hence maintaining accurate operation of RELNAV is difficult. Therefore, we propose an alternative that can solve such problems. In the proposed scheme, we select new references that can play the role of GRU in RELNAV among allies conducting operations on the ground. The new references are responsible for estimating the positions of JUs. To do so optimally, a JU uses a reference selection algorithm that assures high quality of dilution of precision between the JU and the new references. Position errors of JUs decrease largely as a result of the presence of new references in the proposed scheme. RELNAV can therefore be conducted with higher positional accuracy of JUs than that of the existing RELNAV. We verify through some simulations that the feasibility and performance of the proposed scheme are better than those of the existing scheme.