GNSS signal re-acquisition with biased Doppler aiding from INS

Existing INS-aided GPS re-acquisition methods use either long coherent integration periods or non-coherent accumulation to obtain the required frequency resolution or acquire low C/N0 signals. Such methods need accurate position or velocity aiding, which is generally unavailable in many signal re-acquisition scenarios that use low-cost receiver oscillators and sensors. Furthermore, in high dynamic scenarios, the re-acquisition result is not guaranteed with long time accumulation. In order to address these problems, a Doppler-only aiding re-acquisition algorithm based on an ultra-tightly coupled integration architecture is proposed. The algorithm uses biased Doppler values in the range ±50Hz to aid re-acquisition using short period coherent integration. In order to mitigate the Doppler bias, an “adjusted frequency accumulation” algorithm has been developed. The simulation and real data experiments indicate that the proposed re-acquisition algorithm can detect the signal and mitigate the bias of the aiding Doppler with low residual frequency than traditional non-coherent accumulation methods.