Various combining methods have been proposed to utilize multi-satellite-based augmentation system (SBAS) correction to provide accurate position in the global navigation satellite system (GNSS) receiver. However, the proposed methods have not been objectively compared and analyzed, making it difficult to know which ones are effective for multi-GNSS positioning. This paper presents efficient methods of combining multi-SBAS corrections in multi-GNSS positioning by comparing three methods: correction domain integration, measurement domain integration, and position domain integration. The performance of the three methods were analyzed through a covariance analysis that was expanded to multi-GNSS and multi-SBAS. Then, the results were verified by experiments using real measurements and corrections. Furthermore, implementation issues, such as computational complexity, availability, and flexibility, are analyzed. As a result, three methods had the same precision, but different complexity, availability, and flexibility. These results will be important guidelines to design, implement, and analyze navigation systems based on multi-GNSS with multi-SBAS corrections.
This paper presents result of new approach for anti-jamming using a method based on cognitive radio. To detect and get center frequency and bandwidth of jamming, a spectrum sensing based on multi-channel energy detector is implemented on the SDR. The SDR and a universal software radio peripheral is used to support real-time channel reconfiguration. And detected center frequency and bandwidth is used to select LO frequency to avoid jamming and receive GNSS signal. Then the receiver is reconfigured by the selected LO frequency. To verify the feasibility of the proposed anti-jamming process, position, carrier to noise ratio of each channel are measured using a test scenario that is consist of GPS and Beidou with a CW jamming. As a results, by switching of LO frequency, GNSS signal that is not affected by jamming can be received with the same performance as non-jamming.
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