Assisted Global Navigation Satellite System (AGNSS) with Precise Ionosphere Model Assistance
Embodiments enable higher accuracy GNSS performance by generating local/regional ionosphere models tailored to specific local/regional areas of interest and by using location-based delivery of the local/regional ionosphere models to mobile GPS receivers. Different types and levels of reference locations (e.g., Cell ID (CID), Location Area Code (LAC), Radio Network Controller ID (RNC-ID), Mobile Country Code (MCC)) can be used to estimate the location of mobile GPS receivers and to deliver the appropriate local/regional ionosphere models to the mobile GPS receivers. According to embodiments, the local/regional ionosphere models are fit into the same 8-parameter set as the broadcast global ionosphere model, therefore being compatible with existing GPS receivers that accept the broadcast global ionosphere model.
1 . A method of providing precise ionosphere model assistance to a mobile Global Positioning System (GPS) receiver, comprising:
selecting a region of interest;
retrieving historical ionosphere data for the selected region of interest;
generating predictions of ionospheric delays for the selected region based on the historical ionosphere data;
fitting the predictions of ionospheric delays to a standard GPS ionosphere model to generate a predictive ionosphere model for the selected region; and
storing the predictive ionosphere model in a database.
2 . The method of claim 1 , wherein the region of interest represents a geographical area represented by a latitude range and a longitude range.
3 . The method of claim 1 , wherein the historical ionosphere data includes localized ionospheric delays generated by a reference network.
4 . The method of claim 1 , wherein the historical ionosphere data includes broadcast ionospheric delays sent by a Wide Area Augmentation System (WAAS).
5 . The method of claim 1 , wherein the historical ionosphere data includes historical ionospheric delays stored in a database.
6 . The method of claim 5 , wherein the database includes a Crustal Dynamics Data Information System (CDDIS) database.
7 . The method of claim 1 , wherein the historical ionosphere data includes ionospheric delays for the selected region of interest over a K-day period, wherein K is any integer number.
8 . The method of claim 1 , wherein the historical ionosphere data includes a plurality of grid maps, each grid map having a respective time tag that indicates a validity time-of-day for the grid map.
9 . The method of claim 8 , wherein each grid map includes a plurality of grid lines, each grid line including ionospheric delays for a respective sub-region within the selected region of interest.
10 . The method of claim 1 , further comprising:
augmenting the historical ionosphere data prior to said generating step.
11 . The method of claim 1 , wherein said generating step comprises:
generating predicted ionospheric delays for a future N-day period based on historical ionospheric delays for a past K-day period, where N and K are integer numbers.
12 . The method of claim 11 , wherein the predicted ionospheric delays for the future N-day period are generated by averaging the historical ionospheric delays for the past K-day period.
13 . The method of claim 11 , wherein N is equal to 10 and K is equal to 5.
14 . The method of claim 1 , wherein said fitting step comprises:
applying one or more of a least mean squares error (LMSE), Kalman filtering, linear search, and non-linear search algorithm to the predictions of ionospheric delays to generate a plurality of model parameters of the standard GPS ionosphere model.
15 . The method of claim 14 , wherein the plurality of model parameters include 8 Klobuchar parameters.
16 . The method of claim 1 , wherein the method is performed by an Assisted GPS (AGPS) processing site.
17 . The method of claim 1 , further comprising:
retrieving the predictive ionosphere model from the database; and
sending the predictive ionosphere model to a mobile GPS receiver determined to be within the selected region.
18 . The method of claim 17 , wherein the predictive ionosphere model is sent to the mobile GPS receiver using Assisted GPS (AGPS).
19 . The method of claim 17 , further comprising:
determining a reference location associated with the mobile GPS receiver, wherein the reference location estimates a current position of the mobile GPS receiver.
20 . The method of claim 19 , wherein the reference location associated with the mobile GPS receiver includes one of a wireless network cell ID (CID), a Location Area Code (LAC), a Radio Network Controller ID (RNC-ID), and a Mobile Country Code (MCC).
21 . The method of claim 1 , wherein the region of interest is defined by a wireless network cell ID (CID) associated with a mobile GPS receiver.