Enabling location based services with a combined Galileo/GPS receiver architecture

Several new requirements and challenges are introduced with the transition of traditional navigation applications towards location based services. The three most important ones are low cost, low energy consumption, and high sensitivity. This paper introduces the HIGAPS receiver concept. Aim of the first phase in the HIGAPS project is to develop the concept for a combined Galileo/GPS receiver that is specially tailored for location based services, E-911, and other consumer market applications. After providing a brief overview of the receiver, the partitioning into analog hardware, digital hardware, and software is outlined. The architecture of the combined Galileo/GPS RF front-end is presented in low-IF topology. The digital baseband presents a highly parallel correlation architecture for combined Galileo/GPS reception, allowing moderate times to fix for extended dwell times. Parallel digital signal processing combined with aiding data allows single shot measurements par ticularly designed for location based services. Differential correlation, where the current coherently integrated predetection sample is multiplied with the conjugated complex of the previous predetection sample further improves the reception sensitivity. The acquisition sensitivity thresholds for differential correlation are compared versus conventional noncoherent integration for white noise and strong interfering signals. After summarizing multipath mitigation techniques, the multipath performance of the Galileo L1 signal is evaluated through ray-tracing simulations. The introduction of the navigation software and the simulation model finalize the paper