This work deals with the description of the communication using the VSAT satellite network. A used network topology, frequency bands, satellite orbits and also an access technology are defined. The next part is focused on the VSAT terminal, where the block diagram is shown. A model of the indoor unit IDU is designed in the system background of Ansoft Designer. Individual parts of the system model are analyzed in terms of input variables. The results of the simulation are shown. The curves of BER before Viterbi decoding and after Viterbi decoding are shown too.

This thesis provides the reader with an overview of the many elements that are involved in geosynchronous satellite point-to-multipoint Internet Protocol (IP)-based multimedia communications design and also takes a deep dive into the analysis of a real-life scenario, using the TDM / MF-SCPC and TDM / MF-TDMA media access techniques. This thesis starts with a discussion of satellite network topologies utilized within point-to-multipoint satellite communications followed by an overview of the satellite communications channel. A discussion on the intelligent and proper selection of modulation and coding follows. Descriptions and characteristics of the satellite access technologies chosen to be analyzed are next followed by a detailed description of Forward Error Correction (FEC) techniques and a discussion on network-wide tradeoffs so selecting different options. The thesis then presents the results of a real-life scenario, investigating both TDM / MF-SCPC and TDM / MF-TDMA media access technique options, pointing out the tradeoffs brought to the forefront earlier in the study. The major takeaway is that there does not exist a one-size-fits-all solution that works for each and every scenario. / Master of Science

Verksamheten ombord på fartyg blir mer beroende av datakommunikation och många av arbetsuppgifterna ombord underlättas genom att besättningen kan nå information lagrad på annan plats. Fartygens bredbandsanslutning sker till största delen via satellitkommunikation där långa avstånd och begränsad datahastighet resulterar i att datakommunikationen blir ineffektiv. I denna studie undersöks vilken prestandaförbättring som utrustning för nätverksoptimering kan innebära för långsamma WAN-förbindelser via satellit. Undersökningen visade att det största problemet med anslutningar via satellit är den signalfördröjning som uppkommer vid långa sändningsavstånd. Detta medför att det blir prestandaproblem för datatrafiken och användare upplever anslutningen som långsam. För att åtgärda detta finns utrustning som hanterar datatrafiken och genom olika tekniker kan öka prestandan på anslutningen. För att undersöka hur stor prestandaförbättringen kan vara genomfördes ett antal olika experiment med utrustning för nätverksoptimering. Experimenten genomfördes genom att utvärdera filöverföringar med och utan nätverksoptimering. Resultaten visar att utrustningen för nätverksoptimering ger en stor prestandaförbättring vid filöverföringar. / Shipboard operations have become more reliant of data communication and many of the duties on board may be facilitated if the crew can access information stored elsewhere. The broadband connection between ship and shore is mostly done via satellite communication where long distances and limited data rate results in inefficient data communication. This study examines network optimization and the performance improvement this can have regarding slow WAN connections via satellite. The survey showed that the biggest issue with data communication via satellite is the signal delay caused by the long transmission distance which means that there will be performance degradation for data traffic and users will experience the data communication as slow. To solve this there is equipment that enhances the performance of the connection and handles the data communication by implementing various techniques. To investigate how much the performance improvement can be this study carried out a number of experiments with network optimization equipment.  The experiments evaluated file transfer with and without network optimization. The results show that the network optimization gives a major performance improvement regarding file transfer.

Målsättningen med examensarbetet är att utvärdera en metod för att upprätta en kommunikationslänk från en mobil satellitterminal till en geostationär kommunikationssatellit utan kännedom om satellitterminalens position på jordytan. Målsättningen är intressant då GNSS-operatörer (främst i det allmänna USA-drivna GPS-systemet men möjligen även i de tillkommande franska, kinesiska, ryska och europeiska systemen) begränsar den allmänna tillgängligheten av taktiska/strategiska skäl vid konflikter och kriser. Därtill att allmänna globala navigationssatellittjänster, GNSS-system, ofta bygger på mottagningsantenner med låg riktverkan vilka kan störas ut av lokala störningskällor. En mobil satellitterminal blir därmed beroende av manuell inmatning av riktningsvinklar för att upprätta nya satellitkommunikationslänkar. Systemet blir då mycket sårbart. I denna rapport återges resultat från mätserier inhämtade vid satellitterminalinstallationer utförda i Frankrike, Indonesien, Kanada, Polen, Sverige och USA. / The objective of the thesis is to evaluate a method for establishing a communication link from a mobile earth station to a geostationary communication satellite without prior knowledge of the position of the earth station. The objective is interesting as the GNSS-operators (mainly in the United States-run GPS-system, but possibly also in the French, Chinese, Russian and European systems) limits the general availability of tactical/strategic reasons during conflicts and crises. Furthermore, general GNSS-systems are based on receiving antennas with low directivity which can be disrupted by a local opponent or by other local sources of interference. A mobile earth station, lacking proper positioning information, depends on manual entry of directional angles to establish new satellite communication links. The system then becomes very vulnerable. This report evaluates measurement data gathered from deployed satellite terminal installations in Canada, France, Indonesia, Poland, Sweden and the U.S.

Thesis (M.M. (ICT Policy and Regulation))--University of the Witwatersrand, Faculty of Commerce, Law and Management, Graduate School of Public and Development Management, 2014. / The research aimed to investigate the supply and demand side factors that enables or hinders the effectiveness of rural connectivity provided through public access points such as the Thusong Service Centres (TSCs). The lack of broadband and terrestrial infrastructure is often cited as the main reason why rural people are not able to participate in the information society. The status of the Mopani District rural connectivity indicates that the digital divide is not always due to the lack of infrastructure, but due to the etic approach towards the deployment of connectivity and the failure to locate rural connectivity within the broader community development goals. The failure to understand the user requirements contributes to the misconception that Very Small Apparatus Terminals (VSAT) satellite technology is an inadequate solution which must be replaced by fixed broadband. On the other hand, the failure of the Department of Public Service and Administration (DPSA) blueprint indicates the poor level of e-government readiness within the public service sector. The status of the Mopani TSCs also shows that there is a lack of accountability, cooperation and collaboration across the three spheres of government and that there is a misuse of public funds in cases where connectivity resources are duplicated and not optimally used. The separation of the public service connectivity from the public connectivity creates the digital inequality in the targeted communities. The separation has resulted in connectivity being available to some and not to all, because accessibility is based on personal relationships. In other cases there is constructed denied access due to local politics. 16 years later since the establishment of the Universal Service and Access Agency of South Africa (USAASA), the South African Community Informatics (CI) sector is struggling to achieve outputs that produce the desired impact in the targeted communities.

In natural and manmade disasters, inadequate strategies to recover from satellite communication (SATCOM) failures can affect the ability of humanitarian organizations to provide timely assistance to the affected populations. This single case study explored strategies used by network administrators (NAs) to recover from SATCOM failures in humanitarian operations. The study population were NAs in Asia, the Middle East, Central Africa, East Africa, and West Africa. Data were collected from semistructured interviews with 9 NAs and an analysis of network statistics for their locations. The resource-based view was used as the conceptual framework for the study. Using inductive analysis, 3 themes emerged from coding and triangulation: redundancy of equipment, knowledge transfer, and the use of spare parts to service the SATCOM infrastructure. The findings showed that the organization's use of knowledge, and collaboration among NAs and nontechnical staff improved the organization's ability to recover from SATCOM failures. The implication of this study for social change was the reduced cost of satellite services due to the efficient use of the bandwidth. These savings can be channeled into the purchase of vaccines, shelter, and the improvement in the quality of water and sanitation for displaced persons in humanitarian disasters, which improve the organization's delivery of humanitarian services to the affected populations in the disaster.

This thesis describes a possible integrated terrestrial-satellite network system for disaster recovery and response. The motivation of this thesis was based on the adjacent spectrum allocations between the Virginia Tech terrestrial Local Multiple Distribution Service (LMDS) system and a Ka-band satellite system, and potentially being able to provide as an additional Ka-band satellite network backbone to the Virginia Tech terrestrial LMDS system for better and faster communications deployments. The Spaceway satellite system's design parameters were adopted typically for a Ka-band satellite system. The LMDS system was assumed to use IEEE 802.16 standard protocols although it currently uses its own proprietary protocols. Four possible topologies integrating both terrestrial and satellite network were investigated. The study showed that the task was more problematic and complicated than anticipated due to incompatible network protocols, limitations of available hardware components, the high path loss at Ka-band, and the high cost of the equipment, although the adjacent frequency bands do suggest a possible integrated network. In this thesis, the final selected topology was proposed and designed. The technical characteristics of the earth station used for coupling both terrestrial and satellite networks were determined by a link budget analysis and a consideration of network implementations. The reflector antenna used by the earth station was designed. In addition, other system design concerns and engineering tradeoffs, including adjacent satellite interference, rain attenuation, antenna pointing error, noise temperature, and modulation and multiple access selection, were addressed. / Master of Science

Rural telephony has historically been a recurring subject of concern for most large developing countries. It is generally considered that rural telephone users do not generate the same level of telephone traffic and, thus, revenue as urban users, lowering the incentives to invest in rural telecommunications. The financial implications of wiring a vast area for low telephone traffic causes most telephone service providers to ignore or delay offering telephone service to those regions. Still, it is known that telecommunications are essential to the economic development of a region, and that traffic increases rapidly as soon as the service is available. A satellite-based telephone network can provide efficient long distance telephone service to remote rural communities at a lower cost than land-based wired networks in most cases. Mobile satellite systems already provide this service, but are limited in capacity and charge high per- minute fees for the satellite link. Small earth stations and GEO satellites can provide this service more efficiently and at lower cost. A methodology to optimize the network performance has been developed. A set of economic models to evaluate different combinations of network topologies and multiple access techniques have been implemented, and a technical-economic assessment has been performed for the different technologies under different traffic scenarios. Traffic intensity, network size and per-minute user costs have been optimized to achieve the network's economic break-even point under different conditions and constraints. The general behavior of fixed-assignment Single Channel per Carrier SCPC), fixed-assignment Multiple Channel per Carrier (MCPC) and demand-assignment SCPC star networks, as well as demand-assignment SCPC mesh networks has been analyzed. Important parameters have been identified in order to improve the process of effective and cost-efficient satellite rural telephone network design. / Ph. D.

Very small aperture terminal (VSA T) networks offer great opportunities to combine satellite technology and the needs of education in Thailand. An educational VSAT network for Thailand needs a central hub station in Bangkok and seven remote sites with VSAT equipment. The network supports two way compressed video, voice and data links between the central hub and VSAT sites. This thesis examines rain margin, system availability, VSAT antenna size and transponder power utilization in an educational VSAT system using Ku-band. Demand assignment multiple access (DAMA) and single channel per carrier (SCPC) transmission techniques work well for multiple access purposes and minimizes the cost of the space segment. The moving picture expert group-2 (MPEG-2) system is the best choice of compression system in this design. The final performance analysis shows that with the THAICOM-l satellite and 2-Watt VSAT transmitters, and 1.8m or 2.4m VSAT antennas, VSAT-to-hub links can be established using the full transponder power with significant rain margins. Typical outage times for this system are 98.5% for the hub-to-VSAT links and 95.0% for the VSAT-to-hub links. / Master of Science