Iterative acquisition method based on Grey code for weak global positioning system signal

For weak global positioning system signal, long coherent integration can improve the acquisition performance effectively, but the unknown data bits restrict the coherent integration interval within a data bit. Data bits estimation can extend coherent integration interval over multiple data bits with more Doppler frequency search bins. To lighten the calculation burden of data bit combinations searching, an iterative acquisition algorithm is presented based on ordering data bit combinations by Grey code. Modified block-accumulating coherent integration over extended interval (BACIX) algorithm is also presented, which has linear complexity and better performance than BACIX algorithm.