Real Time Implementation of Deeply Integrated Software GPS Receiver and Low Cost IMU for Processing Low-CNR GPS Signals

摘要

A deeply integrated GPS/low-cost IMU system was previously developed to reacquire and track low carrier-to- noise ratio (CNR) GPS signals [1]. The deeply integrated system developed combines RF samples of a software GPS receiver with sampled inertial measurements. Inertial data provide the dynamic the receiver's correlators. Correlator outputs are applied to periodically calibrate the inertial system in order to maintain sufficient accuracy of the inertial dynamic aiding of the GPS signal integration. The deep integration approach allows for a significant increase in signal integration time as compared to conventional unaided GPS receivers. As a result, GPS signals of significantly lower CNR levels can be reacquired and tracked. Results of ground data tests presented in [1] demonstrate reacquisition and continuous carrier phase tracking of GPS signals at the 15 dB-Hz level. The algorithm does not require decoding of the navigation data message for signal tracking. This paper focuses on the real time implementation of the low-CNR reacquisition algorithm presented in [1]. A revised version of the block-serial GPS receiver prototype presented in [2] was used for the implementation.