المؤلفون: Wang, Zhiyu, Wang, Liang, Li, Zishen, Hoque, Mainul, Wang, Ningbo, Wei, Dongyan, Yuan, Hong

المصدر: IET Radar, Sonar & Navigation (Wiley-Blackwell); Aug2023, Vol. 17 Issue 8, p1213-1229, 17p

مصطلحات موضوعية: ORBIT determination, ORBITS of artificial satellites, GLOBAL Positioning System, ORBITS (Astronomy), ARTIFICIAL satellites in navigation

مستخلص: The code multipath error associated with elevation in BDS‐2 is one of the main factors whose impact on the precision of real‐time reduced‐dynamic precise orbit determination (POD) using spaceborne multi‐global navigation satellite systems (GNSS) observation data for FengYun‐3C (FY‐3C) and FengYun‐3D (FY‐3D) satellites. The aim is to construct a code multipath piece‐wise linear error model and analyse the contribution of BDS‐2 to the performance of low earth orbit POD. Conclusions are drawn out from the experimental results: (1) the real‐time POD average precision of FY‐3C and FY‐3D is improved by about 11% and 12% after the correction of BDS‐2 code multipath error; (2) Due to the small number of available BDS‐2 satellites and the limited accuracy of geostationary earth orbit (GEO) satellite real‐time orbit products, the precision of the real‐time overlapping comparison for FY‐3C/FY‐3D by using the BDS‐2 onboard observation data can only reach the decimetre level. However, with the BDS‐2 signal capture capability of the FY‐3D onboard GNSS Occultation Sounder upgraded, the average precision of the BDS‐2‐based POD for FY‐3D is better than that of FY‐3C in each direction and with 10% improvement in the average 3 dimensional‐root mean square (3D‐RMS); (3) Cases of onboard global positioning system (GPS), GPS + BDS‐2 (with GEO), and GPS + BDS‐2 (without GEO) for real‐time POD can meet 5–8 cm precision requirement. The average 3D‐RMS of the real‐time POD for FY‐3C/FY‐3D, which utilises onboard GPS + BDS‐2 data is inferior only to GPS data, owing to the influence of the orbit accuracy of GEO satellites. However, after excluding the influence of GEO satellites, the average result (3D‐RMS) of the real‐time POD for FY‐3C (6.11 cm) and FY‐3D (5.95 cm) is better than those of other cases. [ABSTRACT FROM AUTHOR]

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المؤلفون: Wei, Dongyan¹ (AUTHOR) weidongyan.cn@gmail.com, Wang, Wenbo¹ (AUTHOR), Peng, Mugen¹ (AUTHOR), Liang, Dong¹ (AUTHOR), Liu, Yang¹ (AUTHOR)

المصدر: International Journal of Communication Systems. Jul2011, Vol. 24 Issue 7, p911-924. 14p. 1 Diagram, 1 Chart, 6 Graphs.

مصطلحات موضوعية: *BROADCASTING industry, *WIRELESS communications, *QUALITY of service, *DISTRIBUTION (Probability theory), *DATA transmission systems, *MULTIMEDIA communications, *SUPERPOSITION principle (Physics)

مستخلص: In wireless broadcast system, where feedback is limited and channel state information is only available at the receiver side, layered broadcasting approach has been proposed to fully utilize the channel resources by providing different levels of service quality to users with different channel conditions. However, no upper bound has been given yet to show how the layered broadcast scheme will outperform the conventional broadcast (CB) scheme. In this paper, system average achievable rate (SAAR) is defined as the mean achievable rate of all users within the coverage. Based on continuum superposition coding (SC) with infinite layers, the upper bound of the SAAR of layered broadcasting is given by the derivation of the optimal power distribution function among the superposed layers. The results show that, by promoting the experience of stronger users (users with better channel conditions) without seriously degrading the performance of weaker users (users with worse channel conditions), layered broadcasting approach greatly increases the average system performance. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]