Abstract-The ionosphere, if not modeled sufficiently well, is the largest contributor of error in single frequency GNSS receivers. Modeling ionospheric effects is a major concern for a number of GNSS applications. Ionospheric disturbances induce rapid fluctuations in the phase and the amplitude of received GNSS signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. GNSS signals, although vulnerable, themselves provide an excellent way to measure the ionospheric effect continuously worldwide. Until now, ionospheric monitoring was performed using receivers such as the GSV4004B receiver, which was largely based on GPS only dual frequency receivers. Semi-codeless tracking of the GPS L2 signal greatly limited the accuracy, robustness and utility of the ionospheric TEC measurements and was useless for scintillation measurements on L2. The GPS modernization program, the restored GLONASS, and the upcoming GNSS constellations (Galileo and Compass) bring forth huge benefits for ionospheric monitoring. This paper introduces the NovAtel's next generation GNSS ionospheric scintillation and TEC monitor, the GPStation-6. By incorporating the proven GSV4004B receiver design with the ability to track multi-constellation, multi-frequency, GNSS measurements, the new receiver engine provides robust and less noisy ionospheric measurements.

Detection of global navigation satellite systems (GNSS) signals is limited in indoor environments due to signal attenuation and multipath fading. Longer signal integration intervals are traditionally used to overcome fading losses. Another possibility, explored herein, is to use spatial combining of multiple antenna elements to provide both array and diversity gain. Physical constraints of handheld device implementation limit the practical number of antennas to two. Consequently in this paper, the diversity gain achievable through spatial combining of a pair of antennas is considered from a theoretical perspective, demonstrating gains in excess of 6 dB for typical cases. Experimental verification of the theoretical predictions of the processing gain is provided based on a two-element antenna configuration. Indoor GPS signal measurements were made to determine the statistics of the diversity gain of the two-antenna system relative to the equivalent single antenna system. These measurements corroborate the relative diversity gains determined theoretically.

No abstract

The prolific growth in civilian GNSS market initiated the modernization of GPS and the GLONASS systems in addition to the potential deployment of Galileo and Compass GNSS system. The modernization efforts include numerous signal structure innovations to ensure better performances over legacy GNSS system. The adoption of secondary short synchronization codes is one among these innovations that play an important role in spectral separation, bit synchronization, and narrowband interference protection. In this paper, we present a short synchronization code design based on the optimization of judiciously selected performance criteria. The new synchronization codes were obtained for lengths up to 30 bits through exhaustive search and are characterized by optimal periodic correlation. More importantly, the presence of better synchronization codes over standardized GPS and Galileo codes corroborates the benefits and the need for short synchronization code design.

No abstract