Code Acquisition Using Subexpression Elimination

As code acquisition in the baseband digital signal processing is still one of the major computational bottleneck limiting the time to first fix (TTFF) in navigation devices, this paper proposed a new code acquisition method that results in a lower computational complexity architecture and is more appropriate for searching multiple satellites. We transformed the traditional code acquisition problem into a multiple constant multiplications problem such that the technique of subexpression elimination can be utilized to reduce the addition complexity within code acquisition. A fast acquisition engine based on the proposed method is also demonstrated for its usability for GPS coarse/acquisition (C/A) codes. According to the simulation results, the number of required additions given the number of simultaneously processing satellites is larger than six can be decreased by about 70%, compared to the traditional architecture.