Collective Detection and Direct Positioning Using Multiple GNSS Satellites

Abstract

This paper describes and demonstrates an assisted GPS technique, termed ''Collective Detection,'' for combining satellite correlograms to enable rapid acquisition and direct positioning. Correctly combining correlation values from multiple satellites reduces the required C/N 0 such that satellite signals, which cannot be acquired individually, can contribute constructively to a position solution. The acquisition search is performed in a position/clock space that directly yields the navigation solution. Results from a hardware simulator and live experiments are presented. The simulations compare combinations of 11 satellites and four satellites at C/N 0 levels of 40 and 20 dB-Hz. The outdoor experiments show horizontal position accuracies on the order of 50 m in open sky conditions and in a narrow courtyard environment using one millisecond of data. Collective detection and positioning is shown to be a promising approach for positioning in weak signal environments.

Efficient and Innovative Techniques for Collective Acquisition of Weak GNSS Signals

“…Then, many works using the vectorial approach were proposed for snapshot positioning with coarse accuracy. The main idea of this concept is to improve the overall acquisition sensitivity by combining coherently the detection metrics from all visible satellites [7]- [19]. Assistance information can be used to eliminate the requirement for GNSS data recovery and the receiver's ability to increase integration time.…”

“…In order to mitigate the large computational burden required by the traditional CD scheme, this method is based on the hypothesis that there is at least one strong GNSS signal and it is known. Otherwise, an improvement of the multi-resolution approach initiated in [7] was developed in [15] by using small clock bias spacing with large horizontal position step size to get a high time resolution and reduce the calculation load. To accelerate the collective detection process, the combination of the Bi-dimensional Parallel Search (BPS) acquisition method and the Spectral Peak Location (SPL) method of Doppler frequency estimation with delta correction is proposed in [16].…”

“…In existing CD methods, the acquisition is performed by several iterations while refining the search space at each iteration until we can get an accurate estimate of the position [7] [8]. The CD approach is computationally intensive because of the important number of candidate points which makes its practical implementation very difficult.…”

“…For example in [7], an averaged correlogram is used at the beginning of the search in order to accelerate the detection process. Some works consider the CD approach as an estimation problem.…”

“…Some works consider the CD approach as an estimation problem. For example, [9] uses MLE (Maximum Likelihood Estimation) to get the position solution and [7] adopts the SAGE (Space Alternat-ing Generalised Expectation-Maximisation) optimization algorithm to solve the problems. The MLE is approximated sequentially by dividing a multi-dimensional search into a sequence of single dimensional searches.…”