Test of an Assisted GPS Technique for High-Sensitivity Acquisition of Indoor Signals

A major issue of indoor GPS signals is the extremely low signal-to-noise ratio (e.g. C/N0 = 5 dB Hz ÷ 30 dB Hz ) and the consequent difficulty, for the acquisition stage, of identifying “reliable” autocorrelation peaks. Acquisition sensitivity can be increased by extending the coherent in-tegration time, but the maximum achievable performance is bounded, for instance, by the presence of navigation bits that introduce sign reversals within the coherent integration window. This may result in a partial or even total cancella-tion of “true” peaks. The “sensitivity assistance” approach enables High-Sensitivity (HS) acquisition by providing the acquisition engine with approximate code-phase/Doppler-frequency estimates together with fragments of the data bit-stream, to allow for wiping off the bit transitions and extending the coherent integration