Enhanced full bit acquisition algorithm for software GPS receiver in weak signal environment

To acquire weak signals GPS receiver requires longer observation intervals to accumulate sufficient energy from the signal of intermediate frequency. Full bit method avoids effects of the data bit modulation thereby preserves a longer coherent integration yet consumes too much time and resources. In this paper, an enhanced full bit method is proposed, which aims at speeding up the full bit acquisition remarkably and maintain the superiority in receiving weak signals. All the acquisitions are based on the constant false alarm rate (CAFR) criteria. However, it is difficult to acquire the theoretical detection probability of the full bit method. Thus, an approach to it is given in this paper, and as a standard compared with the enhanced full bit results. The simulation results show that the new method increases the speed of acquisition by 28% on the average; the detection probability of the new method stay close to the full bit method; when non-coherent integration number equals 40, signals whose C/N₀ (carrier-to-noise ratios) are as low as 19 dB·Hz can be acquired.