Performance analysis of multi-frequency receiver to reconstruct ionospheric TEC using combinations of GPS L1, L2, and L5 frequencies

Abstract:

We focus on the GPS L1, L2, and L5 data analysis at the standpoint of its performance for ionospheric TEC studies. The introduction of the unencrypted GPS L2C and L5 signals has the great potential to improve measurements quality of the TEC. However in implementing a multi-frequency receiver, it is necessary to select a combination of frequencies leading to an optimum performance of the existing civilian and encrypted signals taking in account GPS receiver features. In is important to understand an issue regarding the tracking of the L2P(Y) and L2C signals as probable L1-aided observables. Due to the proprietary nature of GPS equipment, we cannot be sure about the receiver tracking features and that is an unfortunate fact for the ionospheric research community.

We analyze the performance of multi-frequency receiver in terms of inter-frequency noise, sensitivity and robustness using both analytical models and experiment by taking the combination of L1, L2 and L5 signals. This result is verified by comparing the behavior of the L1, L2 and L5 carrier phase observables. Comparison between GPS receivers of several types shows that the L2P(Y) and L2C signals tracking process as probable L1-aided technique product. The JAVAD, TRIMPLE, SEPTENTRIO and LEIKA types of GPS receivers were considered for this analysis. It was found that the inter-frequency observation noise significantly differ from one type of GPS receiver to another. To provide high quality of the GPS measurements the particular specification of GPS receiver should be offered for the ionospheric studies. Such a specification means that the narrowband code delay discriminator, the large code rate for the open-access GNSS signals, the expanded front-end bandpass of the radio-frequency chain, the low-noise pre-amplifier and the specific pattern antenna should be specified for the ionospheric study.