Decision-Tree-Based Automatic Filtering and Recovery of Signal Tracking in GPS Software Receiver

This paper presents a decision-tree-based automatic (DTBA) signal filtering and recovery algorithm in the tracking procedure of GPS software receiver. In the first part, the basic digital tracking loop is proposed. The loop consists of phase lock loop (PLL), frequency lock loop (FLL) and delay lock loop (DLL). In the second part, an automatic decision-tree-based algorithm is proposed to handle some exceptional cases when the traditional tracking loop is difficult to work, and retrieve the original signals as much as possible. When the original signals are totally disordered, the DTBA detects and outputs zero signals to avoid producing error navigation bit (D code). The simulations show that over 95% of invalid signals are retrieved with the algorithm. And the shape of the signal wave became clear after correction.