Differential correlation for Galileo/GPS receivers

Current enhanced sensitivity GPS receivers developed for moderate indoor reception increase the observation period with noncoherent integration of the envelopes of coherently integrated predetection samples. The paper analyzes a novel method, differential correlation, where each current coherently integrated predetection sample is multiplied with the complex conjugate of the previous predetection sample. The products are then accumulated. The deterministic signal and stochastic noise components, together with their probability density functions and moments, are derived algebraically for differential correlation and conventional noncoherent integration, while also considering signal and implementation nonidealities. The paper shows that differential correlation can offer an average sensitivity gain over conventional noncoherent integration of around 1.5 dB.