Matched-filter-based low-complexity correlator for simultaneously acquiring global positioning system satellites

In the global positioning system (GPS), code acquisition involves searching all possible code-phase candidates for the existence of satellites. Although code-phase search using a matched filter (MF) is efficient for one satellite, computational complexity increases if numerous satellites have to be searched simultaneously. In this study, a low-complexity routing correlator (RC) that can acquire multiple satellites is proposed. The rationale behind the RC is to fully utilise partial correlation values, which are by-products during the code acquisition process. Traditionally, each satellite´s partial correlation values are instantly summed to decide its existence only. The partial correlation values in the RC, in contrast, can be shared to derive the correlation results of multiple satellites. By sharing and reusing these temporary correlation values, the proposed RC can simultaneously tackle multiple satellites and output the corresponding correlation results, as if there are multiple MFs operating at the same time. In addition, using the RC will not degrade the signal-to-noise ratio. A low-complexity acquisition unit employing the RC for GPS coarse/acquisition (C/A) codes is demonstrated, and the simulation results show that the computational complexity is reduced by about 94´, compared to the conventional MFs.