Software Defined Radio (SDR) is the technology that enables communication by downloading programmed software on a hardware platform. The receiver equipped with the SDR technology is applied the flexibility for a various wireless access environments and also it can replace hardware components with software. For these reasons, interest of the software GPS receiver has been increasing recently. Recently, we have met increasing number of GPS jamming events. To enhance public safety, technologies to mitigate or eliminate the effects of GPS jamming should be studied extensively. In this paper, we proposed an estimation algorithm of GPS C/A code repeat counts to acquire pseudoranges without continuous signal tracking. The proposed method would be beneficial in the restricted cases when GPS signals can be acquired intermittently but continuous signal tracking cannot be guaranteed due to jamming. For performance analysis of algorithm, we estimated the position using TDOA(Time Difference of Arrival) algorithm. And then, we evaluated the characteristics of position error.

Keywords: GPS, SDR, codephase, TDOA