Abstract
Low Earth Orbit (LEO) is of great benefit for the positioning performance of Global Navigation Satellite System (GNSS). To realize the system of LEO-augmented GNSS, three methods to integrate communication and navigation signal for LEO communication system with the least influence on the communication performance are analyzed. The analysis adopts the parameters of IRIDIUM signal as restrictions. This paper gives quantitative comparison of these methods considering CN0(carrier noise power spectral density rate) margin, pseudorange accuracy, Doppler accuracy, and communication loss. For method 1, a low-power navigation signal is added to the communication signal. For method 2, the navigation signal is launched in one or more frames. For method 3, the navigation signal is launched in the frequency band separated to the communication signal. The result shows that the pseudorange accuracy of method 2 is far below method 1 and method 3. However, the difference of Doppler accuracy among the three methods can be emitted. Detailed analysis shows that method 1 is practicable when the communication and navigation signal power rate is 15 dB. It achieves the balance of pseudorange accuracy and bit error rate (BER) performance under this condition. Comprehensive comparison of these methods is given in the last. The result shows that the CN0 margin of the navigation signal for method 3 can be 13.04 dB higher than method 1, based on the accuracy threshold considered in this paper. Methods 1 and 3 have the advantage of high accuracy and high CN0 margin respectively. However, method 3 causes high communication capacity loss. Considering that the main disadvantage of GNSS signals is low CN0, method 3 is a good choice for the LEO-augmented GNSS system. Methods 1 and 3 can be combined to realize both high accuracy and high CN0 margin if possible.
Highlights
A Low Earth Orbit (LEO) constellation has been adopted in satellite communication systems.Considering the high CN0 of the signal received on the ground and high moving velocity of the satellite, Global Navigation Satellite System (GNSS) can be augmented by LEO in many aspects
If the signal is burst, which is true for method 2, only open loop estimation is possible for the the signal is burst, which is including true for pseudorange method 2, only loop estimation is possible for the corresponding measurements andopen corresponding measurements including pseudorange and Doppler
P0nav is equal to the accumulated power in the occupied bandwidth of the communication signal and the highest value is obtained when the communication band locates at the central of the power spectral density (PSD) of the navigation signal
Summary
A Low Earth Orbit (LEO) constellation has been adopted in satellite communication systems. Joerger et al [6] and Rabinowitz et al [7] analyzed the performance of LEO-augmented GPS These analyses are based on the constellation of IRIDIUM, and they show that LEO-augmented GPS shows great improvement in float carrier phase positioning and carrier cycle ambiguity resolution comparing to GPS only. The disadvantage of these analyses is that they are based on simulated measurements They assume that the pseudorange and carrier phase measurements can be got and they did not consider the signal modulation that LEO satellite system adopts. He et al [10] proposes the combination of OFDM and PSK or BOC for the signal modulation of future GNSS This only considers the transmission of navigation messages, and it cannot be used in satellite communication systems.
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