A   , multiple-access schemes based on spread-spectrum techniques, especially CDMA, are promising candidates for future LEO satellite communications systems. As already mentioned, the reason that the wide bandwidth of spread-spectrum waveforms introduces frequency diversity, which can mitigate multipath and interference [1–6]. In addition, with CDMA it is possible to use the same car...

A new routing algorithm for Low-earth orbit (LEO) satellite networks is designed in this study. For this reason genetic algorithms are used. A new objective function is obtained to find the suitable path according to the criteria of the delay and an aging factor. Also Call Blocking Probabilities (CBPs) are considered due to the dynamic nature of the satellite systems. This dynamic routing type ...

In this paper, we survey techniques for routing and performance analysis of Low Earth Orbit (LEO) systems. We first review the basic structure of LEO satellite communications and present the main characteristics of LEO systems. The dynamic characteristics of LEO systems make the performance analysis and routing problem quite complicated. In this study, we review some of the proposed solutions t...

Mobile satellite systems (MSSs) are expected to play a significant role in providing users with communication services worldwide. In such context, low earth orbit (LEO) satellite constellations seem to be a good solution to attain a global coverage and to allow the use of low-power lightweight mobile terminals. This paper analyzes the performance of a novel medium access control (MAC) scheme su...

In this paper we propose a serial-parallel correlator (SPC) for the purpose of PN code acquisition in a low earth orbit (LEO) satellite environment. To reduce the effect of severe Doppler in a LEO satellite channel, we combine the SPC with an FFT technique to combat the carrier frequency offset due to Doppler shift. By using the FFT technique we omit the need for an additional search over the f...

Due to the high mobility of low earth orbit (LEO) satellites, there is a significant number of handover attempts in a LEO satellite mobile communication system, causing a high handover failure rate. This paper proposes an Adaptive Channel Reservation Scheme (ACRS) which gives an overall optimal success rate for both handover and new call initialisation. ACRS is able to adapt to the local traffi...

In a Low Earth Orbit (LEO) satellite mobile multimedia system, the multiple access scheme should be capable of supporting the necessary features that would facilitate the provision of multimedia services. Wideband Code Division Multiple Access (WCDMA) is an attractive multiple access scheme for mobile multimedia communications based on LEO satellites. In this paper, the performance of WCDMA sys...

This master thesis presents a preliminary investigation into the impact of TCP’s advertised receive buffer size and timer granularity on TCP performance over an erroneous link in a low earth orbit (LEO) satellite environment. Conducted simulations include over 200 different combinations of TCP flavor, advertised receive buffer size, timer granularity, and bit error rates. Results show that TCP ...

satellite thermal control ensures safe operating temperature ranges for satellite components throughout the mission life. effects of altitude, spin, and position of satellite radiator(s) on the thermal control of a small low earth orbit (leo) satellite have been studied. results show that change in satellite altitude, in the range considered here, does not produce critical thermal conditions. h...

1 0-7803-7651-X/03/$17.00 © 2003 IEEE 2 IEEEAC paper #1197, Updated December 10, 2002 Abstract—Proposed satellite constellation networks, based on Geostationary Earth Orbit (GEO) satellites, Medium Earth Orbit (MEO), and Low Earth Orbit (LEO) systems, will be required to transport IP traffic and to provide quality of service (QoS). This paper proposes a new Diffserv-based scheme of IP bandwidth...