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Satellite networks provide an alternative to terrestrial networks where cost and lack of infrastructure are driving parameters. For a satellite network to be cost effective one needs to be able to increase the efficiency of the network: this is accomplished by focusing on the parameters that affect the performance of the system and improving on them where possible. The factors affecting the network performance include the capacity, the propagation delay, the protocol used, and the channel error rate, among others. There are various ways to implement a satellite network depending on the satellite orbit, the architecture used, the access technique used, the radio interfaces used, etc. This thesis work describes the chosen satellite standard, Digital Video Broadcasting – Return Channel via Satellite (DVB-RCS) and the associated Medium Access Control (MAC) protocols. Two protocols were designed and investigated under ideal channel conditions, these being the Combined Free/Demand Assigned Multiple Access with Piggy Backing – Packet Dropping (CF/DAMA-PB-PD) protocol; and the Combined Free/Demand Assigned Multiple Access with Piggy Backing – Prioritised Earliest Deadline First (CF/DAMA-PB-PEDF) protocol, both derived from the Combined Free/Demand Assigned Multiple Access with Piggy Backing (CF/DAMA-PB) protocol. The multimedia traffic models for voice, video and web classes are described, validated through simulations and presented; these provide the heterogeneous vi traffic required for evaluating the performance of the satellite system implemented and the designed protocols. Under the multimedia traffic, CF/DAMA-PB-PD was shown to excel in average packet delay reduction while reducing the overall system throughput. The CF/DAMA-PB-PEDF does not contribute to an improvement over the CF/DAMA-PB-PD protocol. The effects of a non-ideal channel on the CF/DAMA-PB-PD protocol was investigated and presented along with the design of three MAC protocols that take the channel characteristics into account to improve on the system performance. The cross-layer interactions, more specifically the interaction between the physical and data–link layers, were used, investigated and presented. The channel state information in terms of signal-to-noise ratio (SNR) was used to improve the system performance. The five protocols evaluated under non-ideal channel conditions were the CF/DAMA-PB, CF/DAMA-PB-PD, CF/DAMA-PB-BSNRF, CF/DAMA-PB-DD and the CF/DAMA-PB-BSNRF+DD. The best overall performance, both in average packet delay while maintaining good QoS levels and throughput was shown to be that of the CF/DAMA-PB-DD protocol. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Over the last years the demand for satellite communication services has been increased. Global and domestic regulatory developments and support, as well as the emerge of new services, have facilitated launcMng capabilities and reduced the costs of manufacturing, launching and operating the satellites. Financing the telecommunication satellite systems is one of the most relevant issues that prospective satellite operators face on these days. Mstitutional lenders require adequate legal advise in order to properly instrument multimillion transactions where securitization is not enough clear and risks are extremely Mgh. TMs work analyzes the most important sources of financing of telecommunication satellites and the most adequate legal structures and methods based in legislation, legal cases, jurisprudence, doctrine, and legal practice.

Governments have funded the development and production of advanced technology in order to establish supply security and/or to achieve economic growth. The policy of government funding includes three alternatives: the two basic options of maintaining a national project or participating in international collaboration involving a number of sovereign states, and the third option of doing both in parallel. The study examines international collaboration in such a way as to assist in the selection of the appropriate policy option. Particular attention is paid to the perspective of small and large, advanced and less advanced European countries. The research problem is addressed by focusing exclusively on those results which distinguish international collaboration from a national project, summarised under the concepts of collaborative sharing and collaborative efficiency. The former identifies the sharing of funding and technology not to be found in a national project. The latter identifies the difference in efficiency between international collaboration and a national project. Efficiency, indicated by cost, quality and time, is examined under the headings of policy-making, executive management, industrial rationalisation and production volume. Furthermore, collaborative sharing and efficiency are examined in the context of parallel national projects. This focus on the differences between the policy options provides the basis for selecting the appropriate one. Previous studies fail to give convincing answers to the research problem: they concentrate on collaborative efficiency while neglecting collaborative sharing, and they disagree over whether international collaboration or a national project is more efficient. This study attempts to overcome these shortcomings by examining a major case study of international collaboration, namely the European Communication Satellite Programme. The following conclusions are established. To achieve supply security, the collaborative option is considered appropriate for the large, advanced European country, and the parallel option for the large, less advanced countries. To achieve economic growth, the national option is appropriate for the advanced European countries. The smaller, less advanced countries are seen to play only a limited role in government funding of advanced technology.

This thesis investigates the modelling of fade countermeasures (FCMs) for the design of geostationary Ka band digital satellite communication systems. The analysis focuses on a typical low-power low-rate very small aperture terminal application using adaptive forward error correction as a way of counteracting the high level of detected dynamic atmospheric fading. The management and performance of such systems is conditioned greatly by the ability of practical controllers at detecting the actual level of total signal attenuation. At 20 or 30 GHz, rain attenuation and tropospheric scintillation are the two major propagation effects of interest. Part of the solution relies on the consideration and integration of their random and dynamic nature in the design process. The finite response time of practical countermeasure systems is a source of performance degradation which can be minimised by the implementation of predictive control strategies. This is the focal point of this thesis. A novel on-line short-term predictor matched to the Ka band fading process is proposed. While the rain attenuation component is efficiently predicted, tropospheric scintillation is the source of the estimation error. To take this into account, a statistical model, based on an extension of the global fading model for rain and scintillation, is then developed so that long term performance of predictive countermeasures can be drawn. Two possible ways to compensate for scintillation-induced prediction errors, namely the fixed and variable detection margin approaches, are proposed, analysed and then compared. This is achieved by calculating the FCM utilisation factor, as well as the throughput and bit error rate performance of a typical Ka band system in the presence of dynamic fading within the context of predictive fade countermeasure control operations. In the last part of this thesis, the inclusion of instantaneous frequency scaling in the design of efficient FCM control schemes is investigated. This is applicable to systems using fade detection at a base frequency. In particular, a new statistical model, accounting for the impact of the stochastic temporal variations of rain drop size distribution on rain attenuation, is presented. This thesis further confirms that countermeasure systems are technologically viable. The consideration of more specific design problems does not change the overall validity of this statement. In this thesis, it is shown that a predictive FCM technique, based on readily available punctured convolutional codes, with their relatively modest coding gain, is sufficient to provide high link availability and user data throughput on a low-power low-rate in-bound VSAT link.

GPS has become very popular in recent years. It is used in wide range of applications including aircraft navigation, search and rescue, space borne attitude and position determination and cellular network synchronization. Each application places demands on GPS for various levels of accuracy, integrity, system availability and continuity of service. Radio frequency interference (RFI) which results from many sources such as TV/FM harmonics, radar or mobile satellite systems, presents a challenge to the use of GPS. It can affect all the service performance indices mentioned above. To improve the accuracy of GPS positioning, a continuously operating reference station (CORS) network can be used. A CORS network provides all the enabled GPS users in an area with corrections to the fundamental measurements, producing more precise positioning. A threat to these networks is a threat to all high-accuracy GPS users. It is therefore necessary to monitor the quality of the received signal with the objective of promptly detecting the presence of RFI and providing a timely warning of the degradation of system accuracy, thereby boosting the integrity of GPS. This research was focused on four main tasks: a) Detection. The focus here is on a power spectral density fluctuation detection technique, in which statistical inference is used to detect narrowband continuous-wave (CW) interference in the GPS signal band after being captured by the RF front-end. An optimal detector algorithm is proposed. At this optimal point, for a fixed Detection Threshold (DT), probability of false alarm becomes minimal and for a fixed probability of false alarm, we can achieve the minimum value for the detection threshold. Experiments show that at this point we have the minimum computational load. This theoretical result is supported by real experiments. Finally this algorithm is employed to detect a real GPS interference signal generated by a TV transmitter in Sydney. b) Characterization. In the characterization section, using the GNSS signal structure and the baseband signal processing inside the GNSS receiver, a closed formula is derived for the received signal quality in terms of effective carrier to noise ratio ( ). This formula is tested and proved by calculating the C/No using the I and Q data from a software GPS receiver. For pulsed CW, a similar analysis is done to characterize the effect of parameters such as pulse repetition period (PRP) and also duty cycle on the received signal quality. Considering this characterization and the commonality between the GPS C/A code and Galileo signal as a basis to build up a common term for satellite availability, the probability of satellite availability in the presence of CW interference is defined and for the two currently available satellite navigation systems (GPS L1 signal and Galileo signal (GIOVE-A BOC(1, 1) in the E1/L1 band)) it is shown that they can be considered as alternatives to each other in the presence of different RFI frequencies as their availability in the presence of CW RFI is different in terms of RFI frequency. c) Mitigation. The last section of the research presents a new concept of ?Satellite Exclusion Zone?. In this technique, using our previously developed characterization techniques, and considering the fact that RFI has different effects on different satellite signals at different times depending on satellite Doppler frequency, the idea of excluding the most vulnerable satellite signal from positioning calculations is proposed. Using real data and real interference, the effectiveness of this technique is proven and its performance analyzed. d) Hardware implementation. The above detection technique is implemented using the UNSW FPGA receiver board called NAMURU.

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 2000. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.