Non-consecutive GNSS signal tracking-based ultra-tight integration system of GNSS/INS for smart devices

Consecutively tracking the global navigation satellite system (GNSS) signal can cause power and computation difficulties to a smart GNSS device with small battery capacity and weak computation capability. We propose a novel computationally efficient ultra-tight integration of GNSS and inertial navigation system (INS). Rather than be consecutively tracked in the traditional receiver as well as its integration with INS, the GNSS signal is non-consecutively tracked in the proposed ultra-tight integration. Compared to traditional GNSS duty cycling (DC) techniques, the proposed ultra-tight integration does not have a tracking loop inside the receiver baseband and only GNSS code signals are tracked with the assistance of INS. The non-consecutive tracking control methods for the GNSS code signals with different wavelengths are investigated, and a moving window-based method is also designed to monitor the non-consecutive code tracking. To validate the proposed ultra-tight integration, a vehicle-based experiment is performed in which global positioning system (GPS), Galileo and BDS (BeiDou Navigation Satellite System) signals are non-consecutively tracked by a developed multi-constellation and multi-frequency software-defined receiver and ultra-tightly coupled with micro-electro-mechanical system (MEMS) inertial measurement unit (IMU)-based INS. The experiment results show that the proposed ultra-tight integration can significantly reduce system computation burden and power consumption and can get a better navigation solution than traditional GNSS receiver and DC techniques.