Performance of an Onboard Packet Switch for Mobile Satellite Communications in Geostationary Satellite Orbit

Paper number

IAC-08.B2.2.9

Author

Mr. Shinichi Taira, National Institute of Information and Communications Technology (NICT), Japan

Coauthor

Mr. Shinichi Yamamoto, National Institute of Information and Communications Technology, Japan

Coauthor

Mr. Shinichi Kozono, National Institute of Information and Communications Technology, Japan

Coauthor

Mr. Masayoshi Yoneda, NEC Toshiba Space Systems, Ltd., Japan

Year

2008

Abstract

	An onboard switch increases the efficiency of satellite communications systems with multi-beam structures.  The National Institute of Information and Communications Technology has been studying a mobile satellite communications system, and developed an onboard packet switch.  The onboard packet switch has the functions of modulating, demodulating, and routing the packet signals.  It can be used in the mobile satellite communications system with a signal transmission rate of over several hundreds of kbps.  In this communications system, a compact mobile earth station that can be either installed in the mobile systems or easily carried anywhere is assumed.  The experimental geostationary satellite for the communications system is the Engineering Test Satellite Eight (ETS-VIII), which was launched in December 2006.  
	The onboard packet switch is composed of modulators, demodulators, switches, and control circuits.  To utilize the transmission power of the satellite and the earth stations, a forward error correction (FEC) technique is adopted.  An automatic repeat request is applied for error correction in addition to FEC because of the large received signal level degradation due to shadowing effects on mobile satellite channels.  
	The switching system functions as bridges operating at the data link layer of the open systems interconnect networking model.  A satellite communications system using multi-beams has a star topology structure, and the satellite can be regarded as a central hub when the switch is located in it.  One beam of the mobile links corresponds to one segment of the network.  The bridges learning process is carried out between the beams, and the switching system builds and maintains tables with media access control address information.  This function of the bridges is equivalent to the location registration, which is indispensable for a mobile communications system that has a multi-beam structure. 
	The initial performance tests of ETS-VIII in the geostationary orbit have been conducted.  The performance test results for the onboard packet switch showed that the modulation and demodulation characteristics of the onboard packet switch in the communications system are almost the same as that before launching. The degradation from the theoretical bit error rate (BER) in the communications system was less than 3 dB at a BER of 1X10-5 both with and without FEC.  It was determined that the performance of the onboard packet switch functioning as bridges is sufficient to meet the requirements of a mobile satellite communications system.

Abstract document

IAC-08.B2.2.9.pdf

Manuscript document

IAC-08.B2.2.9.pdf (🔒 authorized access only).

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