The formula for distance between the observer and the satellite involves satellite coordinates as function of time and observer coordinates. D-STAR is an amateur-radio (ham) digital communication. Doppler effect can reduce the orthogonality and independence of the spatial paths by introducing frequency-dependent fading and correlation. Calculation of the Doppler shift by receiving on the earth and the use of a transmitter placed in a satellite having a known orbit is a rather long and tedious process. Models for Frequency Doppler Shift Prediction for LEO Satellites at L-Band Abstract: In low-earth-orbit (LEO) satellite communications, frequency Doppler shift (FDS) results in lower or higher received frequency than the signal initially transmitted from the satellite. The doppler frequency shiftof an echo signal reflected from a moving target is (Eq. The main payload of the OUFTI-1 nanosatellite is a homemade D-STAR radiocommunication system. Third, it can reduce the spatial diversity and multiplexing gains of MIMO systems, which depend on the orthogonality and independence of the spatial paths. Channel estimation errors occur when the channel state information (CSI), which describes the characteristics of the wireless channel, becomes outdated or inaccurate due to the Doppler-induced channel variations. Second, it can cause channel estimation errors, which are essential for MIMO signal processing and decoding. ICI occurs when the frequency shift caused by Doppler effect makes the subcarriers of the OFDM signal overlap and interfere with each other, degrading the SNR and the bit error rate (BER). Universal mathematic models of Doppler frequency-shift were deduced using geometric vector. First, it can cause inter-carrier interference (ICI) in orthogonal frequency-division multiplexing (OFDM) systems, which are widely used in MIMO communications. 1 (a) shows the change in link distance caused by orbital motion during the 24 h orbital period when the LEO-I satellite and GEO satellite establish a laser link, and the corresponding Doppler shift is shown in Fig. Research on Doppler frequency-shift in satellite communications based on ephemeris of satellite Abstract: The satellite orbit parameters in the ephemeris and location of land receiver were studied. We can perform this correction manually, but an automated system is preferable. This paper analyzes Doppler frequency effects in various satellite orbits. the motion of the satellite with respect to the observer (Doppler shift). Doppler effect can affect MIMO performance in several ways. One of the most important parameters in satellite communication links, particularly in low earth orbits (LEO) and elliptical orbits is Doppler frequency shift (DFS) and Doppler frequency rate (DFR) at communication channels.
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