Adaptability Analysis of IP Routing Protocol in Broadband LEO Constellation Systems

doi:10.12142/ZTECOM.202004006

Abstract

Abstract:

With the inclusion of satellite Internet as the information infrastructure in China’s “new infrastructure” category, relevant domestic industries and scientific research institutes have successively carried out the design of broadband low earth orbit (LEO) constellation systems and key technical research. As the core technology for the satellite-to-ground network communications of a broadband LEO constellation system, routing technology is extremely important for the efficient and reliable transmission of various service data. Focusing on the two important broadband LEO constellation systems in China, in-depth analysis and simulation of the high dynamics of the satellite-to-ground satellites are conducted in this paper to obtain more accurate network topology changes and characteristics; then the adaptability of the ground standard IP routing protocol to the broadband LEO constellation system is analyzed, and an LEO constellation simulation scenario is built with the Opnet software. The simulation results of the convergence performance of the standard IP routing protocol are produced. The results show that the IP protocol does not perform well for LEO satellite constellation networks. Based on the studies, some solutions are proposed to take full advantages of the characteristics of LEO satellite systems. These can also provide a reference for the choice of inter-satellite routing architecture and protocol technology for broadband LEO constellation in the future development.

Key words: satellite Internet, IP routing protocol, high dynamic networking

SUN Chenhua, YIN Bo, LI Xudong, TIAN Xing, PANG Ce. Adaptability Analysis of IP Routing Protocol in Broadband LEO Constellation Systems[J]. ZTE Communications, 2020, 18(4): 34-44.

Figures/Tables 26

Table 1 Overview of typical broadband low earth orbit (LEO) satellite constellation systems

TypicalSatelliteSystem	OneWeb	Starlink	Domestic Satellite System 1	Domestic Satellite System 2
Number of satellites	720	Tens of thousands (4 000 at early stage)	60–240	100–2 000
Frequency	Ku, Ka	Ku, Ka	L, Ka	Ka
Inter-satellite link	No	Plan to have	Yes	Plan to have
Inter-satellite routing	No	No (plan to have)	Yes	No (plan to have for some of the satellites)
Satellite capacity	–	More than 10 Gbit/s	More than 10 Gbit/s	More than 10 Gbit/s
Progress	The test satellites are in orbit.	The test satellites are in orbit (without inter-satellite links).	The test satellites are in orbit (with inter-satellite links).	The test satellites are in orbit (without inter-satellite links).

Figure 2 Reachable coverage of a single satellite (10 spot beams).

Figure 3 Multiple footprints of hybrid orbit constellation (consist of 220 polar orbit satellites and 360 inclined orbit satellites).

Figure 4 The number of visible polar orbit satellites under different ground elevation angles.

Figure 5 The number of visible satellites from the gateway station within 1 hour (polar orbit constellation).

Figure 6 The number of visible satellites from the gateway station within 1 hour (inclined orbit constellation).

Figure 7 The number of visible satellites from the gateway station within 1 hour (hybrid orbit constellation).

Figure 8 The number of visible satellites from the terminal within 1 hour (polar orbit constellation).

Figure 9 The number of visible satellites from the terminal within 1 hour (inclined orbit constellation).

Figure 10 The number of visible satellites from the terminal within 1 hour (hybrid orbit constellation).

Table 2 The number of visible satellites from ground nodes

Constellation	Number of visible satellites
	Gateway station		Terminal
	Max.	Min.	Max.	Min.
Polar orbit	8	4	3	1
Inclined orbit	17	12	7	4
Hybrid orbit	24	17	9	5

Figure 11 Visible durations of satellites from the gateway station (polar orbit constellation).

Figure 12 Visible durations of satellites from the terminal (polar orbit constellation).

Figure 13 Direction changes of hetero-orbital inter-satellite links.

Figure 14 Variation of hetero-orbital inter-satellite links.

Figure 15 Variation of the number of visible polar orbit satellites from the area beyond ±65° (60 minutes).

Figure 16 Variation of the number of visible inclined orbit satellites from the area beyond ±55° (60 minutes).

Figure 17 Variation of the number of visible inclined orbit satellites from the area beyond ±55° (5 minutes).

Figure 18 Working principle of Routing Information Protocol (RIP).

Figure 19 The number of hops between satellites in low earth orbit (LEO) constellation system.

Figure 20 Routing Information Protocol (RIP) routing update when inter-satellite switching occurs.

Figure 21 Working principle of Open Shortest Path First (OSPF) protocol.

Figure 22 Open Shortest Path First (OSPF) routing update when inter-satellite switching occurs.

Figure 23 High dynamic routing reconvergence of satellite-to-earth link in polar orbit constellation.

Figure 24 High dynamic routing reconvergence of inter-satellite link in polar orbit constellation.

Figure 25 SDN-based routing control architecture of broadband low earth orbit (LEO) constellation system.

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