IP theory and applications in satellite communication

Abstract

İnternetin uydu teknolojisine doğru hızla yayılması ve gelişmesi sayesinde, geniş bantlı uydu servisleri pazarı gelecek on yılda kayda değer bir büyüme için dengeleniyor. Şu anki uydu haberleşme sistemlerinde genel olarak, ses ve düşük hızlı data işlemleri küçük terminaller, yüksek hızlı data ve diğer geniş bantlı için büyük terminaller kullanılıyordu. Teknolojik gelişmeler geniş band data hızlarını, ufak terminallerle birleştirmeye başlamasıyla son teknolojiyi kullanarak ev ve iş kullanıcılarına erişim sağlanabiliyor. Özel olarak iki tip geniş band uydu sistemi geliştirilmekte : (i) GEO yörüngesinde olan ve yüksek güç gerektiren uydular, (ii) LEO yörüngesinde uydu ağı oluşturan uydular. Geniş band LEO ağları ve halen geliştirilmekte olan dizaynları, GEO benzerlerinden sonra yayılmaya başlamıştır. Tezin içeriğini tam olarak anlayabilmek için dijital uydu haberleşmesi, TCP/IP ve DVB gibi temel konularda birleştirici bilgiler verilmiş olup, bunun yanında VSAT teorisi açıklanarak eski ve yeni teknolojiler arasındaki farkların karşılaştırılması sağlanmıştır. Bu büyük gelişmelerin yanında, DVB teknlojisinin geliştirilmesiyle, İP paketlerinin DVB/MPEG-2 enkapsülasyonuna adaptasyon sağlandı. Bu methodlarla tek yönlü ve çift yönlü internet erişimleri verimli birşekilde gerçeklenebilir duruma gelmiştir. Buna ek olarak tezde belirtildiği gibi bazı kodlama teknikleri (ör.Turbo Kodlama) ile daha fazla band ve enerji verimliliği elde etmek mümkündür. Bu uygulama methodları ve örnekleri ayrıca tezde verilmiştir.

Thanks to both the rapid deployment of the Internet and advances in satellite technology, the market for broadband satellite services is poised for substantial growth in the coming decade. Current communications satellite systems have generally been designed to provide either voice or data transaction (low data rate) services through small terminals, or trunking (high data rate, or broadband) services through large terminals. However, technological advances are enabling new systems that combine broadband data rates with small terminals, thereby providing more affordable "last-mile" network access to home and small business users worldwide. In particular, two types of broadband satellite systems are under development: high-power satellites deployed at traditional geostationary (GEO) orbits, and large constellations of satellites deployed at much lower (LEO) orbits. To undertstand the full concept of this thesis, it is also given some fundemental informations about like Digital Communication used in Satellite, TCP/IP, DVB to combine them easily in reader mind. Besides these VSAT theory also explained to give an idea to compare old and new technologies. When using GEO satellites to provide Internet access service, the performance of the Internet's Transmission Control Protocol (TCP) is degraded by the high latency and high degree of bandwidth asymmetry present in such systems. We therefore undertook a comprehensive study of TCP performance in the context of broadband satellite systems used for network access. In contrast to research on GEO systems, research on LEO systems is still in its infancy. While LEO systems are being designed specifically to avoid the high latencies found in GEO systems, their design is challenging from a packet routing perspective due to the highly time-varying nature of the LEO network topology. These give full global or targeted coverage of the Earth. Constellations make possible more reuse of limited available ground-space communication frequencies, providing higher overall network capacity as a result of this frequency reuse. Broadband satellite networks are likely to become an important niche of the future Internet because of their unique ability to provide network access from almost any point on the globe, particularly those underserved by terrestrial infrastructure. However, because the design of Internet protocols is driven by the performance of the wired Internet, satellite network engineers must be vigilant in assisting in the design and deployment of satellite-friendly protocols and in considering how satellite networks interwork with the wired Internet. Broadband LEO networks are likely to be deployed later than their GEO counterparts, and the design of these networks is still in its infancy, particularly since such networks are significantly more ambitious technically than anything that has been previously attempted. Besides these tremendeus improvements, DVB technology is also developed and adapted to the IP technology by DVB/MPEG-2 encapsulation. By this methods, one- xiv way and two-way satellite accesses can be implemented at now. And also by using some coding techniques (ex. Turbo Coding ) it is possible to get so much bandwidth and energy efficiency. Also these application methods and examples is given in this thesis.