Accelerated collective detection technique for weak GNSS signal environment

Abstract

Collective Detection is an Assisted-GNSS (A-GNSS) technique for direct positioning, where the information from all satellites in view is combined to enable rapid acquisition and a direct navigation solution. This technique is shown to perform effectively in weak signal environments like indoor navigation, reducing the required signal strength by 10 to 20 dB-Hz. When the signal from satellites cannot be acquired individually, Collective Detection constructively adds information from each satellite together, thus improving sensitivity and directly leading to a position solution. In a sense, the vector-based approach used generally in tracking, is extended to the acquisition stage. However, the existing Collective Detection techniques are computationally intensive and thus have limited practical applications. Also, the transmit-time assistance provided to the receiver is assumed to be of sub-millisecond accuracy, which is not a feasible assumption. This paper looks at these limitations of Collective Detection and aims to mitigate them under the assumption that at least one satellite can be acquired individually. It has been shown that the proposed Accelerated Collective Detection is faster and more efficient than the traditional scheme, and performs equally well in terms of accuracy.