Bit-flipping prediction acquisition algorithm of weak GPS signal

Abstract

Long coherent integration duration is needed for weak Global Positioning System(GPS) signal acquisition.However,it is limited in 10 ms by the navigation data bit flipping,which is far from enough. To further improve the acquisition sensitivity,a bit-flipping prediction algorithm was proposed. Firstly,the 5 ms signal with possible involve bitflipping,which was detected through the comparison of the coherent integration results of the several blocks of data,was canceled. Then coherent integration was applied to its sub-block signal in rest 15 ms and the results did differential coherent integration to overcome its bit-flip and reduced the square loss of non-coherence. At the same time,the summation operation was done ahead of coherent integration to depress its computational complexity. The theoretical research and simulation results show that the acquisition sensitivity and acquisition efficiency have been improved,and the algorithm even can capture the weak signal with Signal-to-Noise Ratio(SNR) less than- 50 dB.