Research on Fast Hot-Start Algorithm for Combined BDS and GPS Receiver

The core issue of fast positioning during the hot start process is to obtain the position result before frame synchronization. Due to the lack of incomplete time information needed to compute the pseudo range before frame synchronization, the pseudo range must be calculated by estimating the integer part of bit-scale time plus the precise fraction part within one bit. In this paper, we introduce a new fast hot-start algorithm that is easily implemented within traditional Least Square (LS) method framework. The proposed algorithm makes full use of an underling property which contributes to the establishment of a good linearity between the Satellite Transmitted Time (STT) biases and pseudo range residuals. With this relation, the integer part of bit-scale time can be precisely calculated, thus correct positioning results can be obtained. Simulation results show that the proposed algorithm can provide stable and fairly good positioning results after bit synchronization than that of traditional scheme. Furthermore, we extend the hot-start algorithm to the case of dual-system, and discuss the strategies for combined BDS and GPS receiver.