Kalman Filter Based Adaptive Loop Aiding for Performance Improvement in Low CNIR Environments

Carrier tracking in GNSS receivers suffers in environments where platform dynamics, received noise and interference are expected simultaneously. Similar is the case of a Locata receiver which operates on the same basic principles as GNSS receivers. A reduction in tracking loop bandwidth may offer noise rejection, but at the same time it makes tracking more vulnerable to oscillator and platform dynamics. This paper aims to stabilise Locata receiver tracking in the presence of received noise and interference in a dynamic environment. It first compares two existing solutions: Adaptive Loop Aiding and the use of Kalman filters for noise reduction. It then proposes a Kalman filter based loop aiding scheme for further reduction in noise without making tracking more vulnerable to signal dynamics and loss of lock. It is shown that the proposed scheme offers reductions of 93% and 85% in error for static and dynamic platform cases respectively, as compared to adaptive loop aiding without a Kalman filter.