Abstract
The objective of this work is to investigate the performances of orthogonal frequency division multiplexing (OFDM) and minimum frequency shift keying (MSK) modulations as potential future global navigation satellite systems (GNSS) signal modulation schemes. MSK is used in global system for mobile communications because of its spectral efficiency, while OFDM is used in WLAN and digital video broadcast-terrestrial because of its multipath mitigation capability. These advantages of MSK and OFDM modulations render them as promising modulation candidates for future GNSS signals to offer enhanced performances in challenging environments. Gabor bandwidth and multipath error envelopes of these two modulations were computed and compared with those of the current global positioning system (GPS), Galileo, and Beidou signal modulations. The results show that OFDM modulation demonstrated promises as a viable future GNSS modulation, especially for signals that require pre-filtering bandwidths larger than 2 MHz, while MSK modulation is more desirable for pre-filtering bandwidth below 2 MHz where it exhibits the largest Gabor bandwidth.
Highlights
Binary phase shift keying (BPSK) modulation is the legacy modulation scheme used in satellite navigation signals such as the global positioning system (GPS)
minimum frequency shift keying (MSK) is used in global system for mobile communications because of its spectral efficiency, while orthogonal frequency division multiplexing (OFDM) is used in WLAN and digital video broadcast-terrestrial because of its multipath mitigation capability
Both MSK and OFDM modulations are often applied to satellite and mobile communication systems due to their superior performance compared with the traditional BPSK modulation in terms of larger out-of-band attenuation
Summary
Binary phase shift keying (BPSK) modulation is the legacy modulation scheme used in satellite navigation signals such as the global positioning system (GPS). It is widely used in communication systems despite its relatively low spectral efficiency. Together with various regional navigation satellite systems and space-based augmentation systems, there will be more than 160 satellites and over 400 signals in space by the year 2030 (Betz 2013). Such a large number of signals will further exacerbate an already crowded radio spectrum and negatively impact the performance of all navigation systems sharing the limited resources. Improving the signal spectral efficiency to minimize mutual interference is a critical issue in future GNSS signal design
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