Low earth orbit satellite systems for communications

Abstract

It may be that we are now entering the era of LEO constellation satellite communications after thirty years of domination by the GEO systems. This paper heralds the coming of the new era with a tutorial approach to the system design and trade‐offs of LEO constellation system design. It discusses orbital configurations, network topologies and routeing considerations, multiple access schemes and link performance design. In so doing it brings out the major design parameters and how they interact with each other. Also considered are the service applications for the LEO constellation systems, and the important difference between real‐time and delayed communication systems is highlighted. Examples of single and multi‐beam (cellular) coverage system link designs are presented for L‐Ka frequency bands. Future papers will consider aspects of the LEO spacecraft and launchers.

Efficient dynamic channel allocation techniques with handover queuing for mobile satellite networks

“…In particular, the IRIDIUM system proposed by Motorola [3] is considered. The IRIDIUM system uses 66 satellites over six polar circular orbits at about 780 km of altitude: Verb = 26600 km/h.…”

“…In this case, a new channel must be assigned to the call in the new cell (destination cell), to avoid a forced call termination. This procedure is called (interbeams) handover [3].…”

Different queuing policies for handover requests in low Earth orbit mobile satellite systems

“…In particular, the system may evaluate (with a sufficient accuracy) the time for a queued handover request as follows: 1) the MS position is determined at the beginning of the call, as described below; 2) the MS position can be easily tracked during the call 3 ; 3) the time can be obtained by using (25), 4 since the system knows both the MS motion and the cellular coverage geometry and then can estimate the distance crossed in the overlap area. The efficiency of this version of the LUI scheme suitable for implementation in LEO-MSS's depends on the accuracy of the MS position estimation.…”

“…Moreover, in an integrated scenario, MSS's will also support terrestrial cellular networks when these will be congested or malfunctioning [1]- [3]. This paper is focused on low earth orbit (LEO) satellites [4]. The analysis here presented is kept general and illustrated numerically in the case of the IRIDIUM system [5].…”

Design of LEO Constellations Providing Internet Services Based on SOC Method

“…However, the variation of altitude brings about a higher requirement for the on-board components when satellites fly across the Van Allen radiation belt. Circular low earth orbit consequently becomes the most popularly used in communication constellations [4].…”