Abstract
The short spreading code used by the BeiDou Navigation Satellite System (BDS) B1-I or GPS Coarse/Acquistiion (C/A) can cause aggregately undesirable cross-correlation between signals within each single constellation. This GPS-to-GPS or BDS-to-BDS correlation is referred to as self-interference. A GPS C/A code self-interference model is extended to propose a self-interference model for BDS B1, taking into account the unique feature of the B1-I signal transmitted by BDS medium Earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites—an extra Neumann-Hoffmann (NH) code. Currently there is no analytical model for BDS self-interference and a simple three parameter analytical model is proposed. The model is developed by calculating the spectral separation coefficient (SSC), converting SSC to equivalent white noise power level, and then using this to calculate effective carrier-to-noise density ratio. Cyclostationarity embedded in the signal offers the proposed model additional accuracy in predicting B1-I self-interference. Hardware simulator data are used to validate the model. Software simulator data are used to show the impact of self-interference on a typical BDS receiver including the finding that self-interference effect is most significant when the differential Doppler between desired and undesired signal is zero. Simulation results show the aggregate noise caused by just two undesirable spreading codes on a single desirable signal could lift the receiver noise floor by 3.83 dB under extreme C/N0 (carrier to noise density ratio) conditions (around 20 dB-Hz). This aggregate noise has the potential to increase code tracking standard deviation by 11.65 m under low C/N0 (15–19 dB-Hz) conditions and should therefore, be avoided for high-sensitivity applications. Although the findings refer to Beidou system, the principle weakness of the short codes illuminated here are valid for other satellite navigation systems.
Highlights
The BeiDou Navigation Satellite System (BDS) is a relatively new member of the Global NavigationSatellite System (GNSS) family
The results from UNIversal COmmunications and Radio Navigation receiver (UNICORN) and the analytical model are compared to see if the predicted values agree with measured values according
Based on the validity themodel, model,we we apply apply this model totoshow some insights intointo thethe typical behaviour of self-interference in Firstly, we try to find when the equivalent typical behaviour of self-interference in Firstly, we try to find when the equivalent typical behaviour of self-interference in BDS B1-I signals
Summary
The BeiDou Navigation Satellite System (BDS) is a relatively new member of the Global Navigation. To evaluate BDS self-interference, a simple analytical model is developed from an existing model for GPS self-interference [12] to predict the impact of B1-I code self-interference on BDS receiver functions that are dependent primarily on the sum of the correlations (e.g., carrier phase tracking and data demodulation). Noise Level” derives analytical models for the variance at the correlator output for three situations: the bits of the and undesired signalssignals are (1)are aligned or (2) or misaligned by anby integer number of data bitsdesired of the desired and undesired (1) aligned (2) misaligned an integer number code chipschips or (3)ormisaligned by aby fraction of aofcode chip.
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