The development of modularized post processing GPS software receiving platform

Modularized GPS software defined radio (SDR) software platform has many advantages of applying and modifying algorithm. Hardware based GPS receiver uses many hardware parts (such as RF front, correlators, CPU and others) that process tracked signal and navigation data to calculate user position, while SDR uses software modules, which run on general purpose CPU platform, to implement same function. SDR needs not change hardware part and it is not limited by hardware capability when new processing algorithm is required. The weakness of SDR is that software correlation takes lots of processing time. However, in these days the evolution of MPU and DSP, and the size minimization of general purpose CPU increase the competitiveness of SDR against the hardware GPS receiver. This paper presents a study of modulization of GPS SDR software platform and development of the GNSS SDR software platform using MATLAB Simulinktrade. We focus on especially post processing SDR platform which is usually adapted in research area. The main functions of SDR are GPS signal acquisition, signal tracking, decoding navigation data and calculating stand alone user position from stored data that was intermediate frequency (IF) down converted and sampled. Each module of SDR platform is categorized by function for applicability. The developed SDR software platform was tested using stored data that IF down converted and sampled. The test results present that the SDR software platform calculates user position properly.