Leclère, Botteron, and Farine Figure 15. Timing diagram of the implementation of the pre-FFT secondary code removal in a sequential way (Figure 3) with NS = 4. Grey parts indicate zeros (NZ samples are padded to each accumulation result before the FFT, thus the FFTs length is NFFT = 2NP + NZ), and hatched parts indicate we do not care 2 about these samples. The processing time to compute K times the full correlation (i.e. K times NS outputs yi) is K × 2NP N S + NZ + L + NFFT + L + NP = 2 NP(2K N S + 3) + 2NZ + 2L. Figure 16. Timing diagram of the implementation of the pre-FFT secondary code removal in a parallel way (Figure 4) with NS = 4. The processing time to compute K times the full correlation is K × [2NPNS + NZ + NFFT(NS - 2)] + NFFT + L + NFFT + L + NP = NP[4K(NS - 1) + 5] + NZ[K(NS - 1) + 2] + 2L. AUGUST 2017 IEEE A&E SYSTEMS MAGAZINE 59