Dissertations / Theses on the topic 'Satellite-terrestrial networks'

When the Internet of Things (IoT) was introduced, it causes an immense change in human life. Recently, different IoT emerging use cases, which will involve an even higher number of connected devices aimed at collecting and sending data with different purposes and over different application scenarios, such as smart city, smart factory, and smart agriculture. In some cases, the terrestrial infrastructure is not enough to guarantee the typical performance indicators due to its design and intrinsic limitations. Coverage is an example, where the terrestrial infrastructure is not able to cover certain areas such as remote and rural areas. Flying technologies, such as communication satellites and Unmanned Aerial Vehicles (UAVs), can contribute to overcome the limitations of the terrestrial infrastructure, offering wider coverage, higher resilience and availability, and improving user’s Quality of Experience (QoE). IoT can benefit from the UAVs and satellite integration in many ways, also beyond the coverage extension and the increase of the available bandwidth that these objects can offer. This thesis proposes the integration of both IoT and UAVs to guarantee the increased coverage in hard to reach and out of coverage areas. Its core focus addresses the development of the IoT flying gateway and data mule and testing both approaches to show their feasibility. The first approach for the integration of IoT and UAV results in the implementing of LoRa flying gateway with the aim of increasing the IoT communication protocols’ coverage area to reach remote and rural areas. This flying gateway examines the feasibility for extending the coverage in a remote area and transmitting the data to the IoT cloud in real-time. Moreover, it considers the presence of a satellite between the gateway and the final destination for areas with no Internet connectivity and communication means such as WiFi, Ethernet, 4G, or LTE. The experimental results have shown that deploying a LoRa gateway on board a flying drone is an ideal option for the extension of the IoT network coverage in rural and remote areas. The second approach for the integration of the aforementioned technologies is the deployment of IoT data mule concept for LoRa networks. The difference here is the storage of the data on board of the gateway and not transmitting the data to the IoT cloud in real time. The aim of this approach is to receive the data from the LoRa sensors installed in a remote area, store them in the gateway up until this flying gateway is connected to the Internet. The experimental results have shown the feasibility of our flying data mule in terms of signal quality, data delivery, power consumption and gateway status. The third approach considers the security aspect in LoRa networks. The possible physical attacks that can be performed on any LoRa device can be performed once its location is revealed. Position estimation was carried out using one of the LoRa signal features: RSSI. The values of RSSI are fed to the Trilateration localization algorithm to estimate the device’s position. Different outdoor tests were done with and without the drone, and the results have shown that RSSI is a low cost option for position estimation that can result in a slight error due to different environmental conditions that affect the signal quality. In conclusion, by adopting both IoT technology and UAV, this thesis advances the development of flying LoRa gateway and LoRa data mule for the aim of increasing the coverage of LoRa networks to reach rural and remote areas. Moreover, this research could be considered as the first step towards the development of high quality and performance LoRa flying gateway to be tested and used in massive LoRa IoT networks in rural and remote areas.

Heterogeneous wireless networking technologies such as satellite, UMTS, WiMax and WLAN are being used to provide network access for both voice and data services. In big cities, the densely populated areas like town centres, shopping centres and train stations may have coverage of multiple wireless networks. Traditional Radio Access Technology (RAT) selection algorithms are mainly based on the 'Always Best Connected' paradigm whereby the mobile nodes are always directed towards the available network which has the strongest and fastest link. Hence a large number of mobile users may be connected to the more common UMTS while the other networks like WiMax and WLAN would be underutilised, thereby creating an unbalanced load across these different wireless networks. This high variation among the load across different co-located networks may cause congestion on overloaded network leading to high call blocking and call dropping probabilities. This can be alleviated by moving mobile users from heavily loaded networks to least loaded networks. This thesis presents a novel framework for load balancing in heterogeneous wireless networks incorporating the IEEE 802.21 Media Independent Handover (MIH). The framework comprises of novel load-aware RAT selection techniques and novel network load balancing mechanism. Three new different load balancing algorithms i.e. baseline, fuzzy and neural-fuzzy algorithms have also been presented in this thesis that are used by the framework for efficient load balancing across the different co-located wireless networks. A simulation model developed in NS2 validates the performance of the proposed load balancing framework. Different attributes like load distribution in all wireless networks, handover latencies, packet drops, throughput at mobile nodes and network utilization have been observed to evaluate the effects of load balancing using different scenarios. The simulation results indicate that with load balancing the performance efficiency improves as the overloaded situation is avoided by load balancing.

Il presente lavoro di testi descrive le attività di ricerca relative all'integrazione di reti terrestri e satellitari. Gli aspetti architetturali, protocollari e di sistema sono analizzati, seguiti da proposte di migliorie e nuovi approcci che sono discussi e validati per mezzo di simulazioni, test su piattaforma di emulazione basata su Linux e sistemi veri.<br>This Ph.D. thesis represents the outcomes of the research activities performed on the integration of satellite and terrestrial networks. After a deep analysis on architectures, protocols, scenarios and existing projects several new proposals are introduced and discussed, validated by means of simulation, emulation over a Linux based platform or using real hardware.

The goal of non-terrestrial networks (NTN) is to complement terrestrial 5G networks by providing enhanced coverage and service continuity for unserved areas of 5G terrestrial networks. One of the pivotal factors in the effective deployment of mobile satellite systems in the 5G network is to maximize the utilization of the current technology in terrestrial systems, to lower the implementation costs. The efficient design and integration of NTN to 5G systems depend on the consideration of some unique features of satellite communication systems, such as large propagation delays and large Doppler frequency shifts. Specifically, geostationary earth orbit (GEO) communication satellites experience large propagation delays, while low earth orbit (LEO) communication satellites are prone to large Doppler frequency shifts due to the fast mobility of LEO satellites and/or user equipment (UE). These factors affect some of the currently used algorithms of the radio access network (RAN) of terrestrial 5G systems. Specifically affected is the random access channel (RACH). This work will focus on the analysis, assessment and improvement of Physical Random Access Channel (PRACH) in (5G) to be adopted for (NTN), the implemented work is comprising of AWGN channel, RACH transmitter, which doesn't have a big challenge as the case of RACH receiver regarding the detection with the satellite impairments. Hence, the work focused on the receiver performance in two different scenarios: Near GEO Sat and LEO Sat.

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.<br>Master of Science

To meet an ever-growing demand for advanced multimedia services and to support electronic connectivity anywhere on the planet, development of ubiquitous broadband multimedia systems is gaining a huge interest at both academic and industry levels. Satellite networks in general and LEO satellite constellations in particular will play an essential role in the deployment of such systems. Therefore, as LEO satellite constellations like Iridium or IridiumNEXT are extremely expensive to deploy and maintain, extending their service lifetimes is of crucial importance. In the main part of this thesis, we propose different techniques for extending satellite service life in LEO satellite constellations. Satellites in such constellations can spend over 30% of their time under the earth’s umbra, time during which they are powered by batteries. While the batteries are recharged by solar energy, the Depth of Discharge (DoD) they reach during eclipse significantly affects their lifetime – and by extension, the service life of the satellites themselves. For batteries of the type that power Iridium and Iridium-NEXT satellites, a 15% increase to the DoD can practically cut their service lives in half. We first focus on routing and propose two new routing metrics – LASER and SLIM – that try to strike a balance between performance and battery DoD in LEO satellite constellations. Our basic approach is to leverage the deterministic movement of satellites for favoring routing traffic over satellites exposed to the sun as opposed to the eclipsed satellites, thereby decreasing the average battery DoD– all without taking a significant penalty in performance. Then, we deal with resource consolidation – a new paradigm for the reduction of the power consumption. It consists in having a carefully selected subset of network links entering a sleep state, and use the rest to transport the required amount of traffic. This possible without causing major disruptions to network activities. Since communication networks are designed over the peak traffic periods, and with redundancy and over-provisioned in mind. As a remedy to these issues, we propose two different methods to perform resource consolidation in LEO networks. First, we propose trafficaware metric for quantifiying the quality of a frugal topology, the Maximum Link Utilization (MLU). With the problem being NP-hard subject to a given MLU threshold, we introduce two heuristics, BASIC and SNAP, which represent different tradeoffs in terms of performance and simplicity. Second, we propose a new lightweight traffic-agnostic metric for quantifiying the quality of a frugal topology, the Adequacy Index (ADI). After showing that the problem of minimizing the power consumption of a LEO network subject to a given ADI threshold is NP-hard, we propose a heuristc named AvOId to solve it. We evaluate both forms of resource consolidation using realistic LEO topologies and traffic requests. The results show that the simple schemes we develop are almost double the satellite batteries lifetime. Following the green networking in LEO systems, the second part of this thesis focuses on extending the resource consolidation schemes to current wired networks. Indeed, the energy consumption of wired networks has been traditionally overlooked. Several studies exhibit that the traffic load of the routers only has a small influence on their energy consumption. Hence, the power consumption in networks is strongly related to the number of active network elements. In this context, we extend the traffic-agnostic metric, ADI, to the wired networks. We model the problem subject to ADI threshold as NP-hard. Then, we propose two polynomial time heuristics – ABStAIn and CuTBAck. Although ABStAIn and CuTBAck are traffic unaware, we assess their behavior under real traffic loads from 3 networks, demonstrating that their performance are comparable to the more complex traffic-aware solutions proposed in the literature.

The recent technological advances in the satellite domain such as the use of High Throughput Satellites (HTS) with throughput rates that are magnitudes higher than with previous ones, or the use of large non- Geostationary Earth Orbit (GEO) satellites constellations, etc, are reducing the price per bit and enhancing the Quality of Service (QoS) metrics such as latency, etc., changing the way that the capacity is being brought to the market and making it more attractive for other services such as satellite broadband communications. These new capabilities coupled with the advantages offered by satellite communications such as the unique wide-scale geographical coverage, inherent broadcast/multicast capabilities and highly reliable connectivity, anticipate new opportunities for the integration of the satellite component into the 5G ecosystem. One of the most compelling scenarios is mobile backhauling, where satellite capacity can be used to complement the terrestrial backhauling infrastructure, not only in hard to reach areas, but also for more efficient traffic delivery to Radio Access Network (RAN) nodes, increased resiliency and better support for fast, temporary cell deployments and moving cells. In this context, this thesis work focuses on achieving better satellite-terrestrial backhaul network integration through the development of Traffic Engineering (TE) strategies to manage in a better way the dynamically steerable satellite provisioned capacity. To do this, this thesis work first takes the steps in the definition of an architectural framework that enables a better satellite-terrestrial mobile backhaul network integration, managing the satellite capacity as a constituent part of a Software Defined Networking (SDN) -based TE for mobile backhaul network. Under this basis, this thesis work first proposes and assesses a model for the analysis of capacity and traffic management strategies for hybrid satellite-terrestrial mobile backhauling networks that rely on SDN for fine-grained traffic steering. The performance analysis is carried out in terms of capacity gains that can be achieved when the satellite backhaul capacity is used for traffic overflow, taking into account the placement of the satellite capacity at different traffic aggregation levels and considering a spatial correlation of the traffic demand. Later, the thesis work presents the development of SDN-based TE strategies and algorithms that exploits the dynamically steerable satellite capacity provisioned for resilience purposes to better utilize the satellite capacity by maximizing the network utility under both failure and non-failure conditions in some terrestrial links, under the consideration of elastic, inelastic and unicast and multicast traffic. The performance analysis is carried out in terms of global network utility, fairness and connexion rejection rates compared to non SDN-based TE applications. Finally, sustained in the defined architectural framework designs, the thesis work presents an experimental Proof of Concept (PoC) and validation of a satellite-terrestrial backhaul links integration solution that builts upon SDN technologies for the realization of End-to-End (E2E) TE applications in mobile backhauling networks with a satellite component, assessing the feasibility of the proposed SDN-based integration solution under a practical laboratory setting that combines the use of commercial, experimentation-oriented and emulation equipment and software.<br>Los recientes avances tecnológicos en el dominio de los satélites, como el uso de satélites de alto rendimiento (HTS) con tasas de rendimiento que son magnitudes más altas que los anteriores, o el uso de grandes constelaciones de satélites de órbita no geoestacionaria (GEO), etc. están reduciendo el precio por bit y mejorando las métricas de Calidad de Servicio (QoS) como la latencia, etc., cambiando la forma en que la capacidad se está llevando al mercado, y haciéndola más atractiva para otros servicios como las comunicaciones de banda ancha por satélite. Estas nuevas capacidades, junto con las ventajas ofrecidas por las comunicaciones por satélite, como la cobertura geográfica a gran escala, las inherentes capacidades de difusión / multidifusión y la conectividad altamente confiable, anticipan nuevas oportunidades para la integración de la componente satelital al ecosistema 5G. Uno de los escenarios más atractivos es el backhauling móvil, donde la capacidad del satélite se puede usar para complementar la infraestructura de backhauling terrestre, no solo en áreas de difícil acceso, sino también para la entrega de tráfico de manera más eficiente a los nodos de la Red de Acceso (RAN), una mayor resiliencia y mejor soporte para implementaciones rápidas y temporales de células, así como células en movimiento. En este contexto, este trabajo de tesis se centra en lograr una mejor integración de la red híbrida de backhaul satélital-terrestre, a través del desarrollo de estrategias de ingeniería de tráfico (TE) para gestionar de una mejor manera la capacidad dinámicamente orientable del satélite. Para hacer esto, este trabajo de tesis primero toma los pasos en la definición de un marco de arquitectura que permite una mejor integración de una red híbrida satelital-terrestre de backhaul móvil, gestionando la capacidad del satélite como parte constitutiva de un TE basado en Software Defined Networking (SDN). Bajo esta base, este trabajo de tesis primero propone y evalúa un modelo para el análisis de la capacidad y las estrategias de gestión del tráfico para redes híbridas satelital-terrestre de backhaul móvil basadas en SDN para la dirección de tráfico. El análisis de rendimiento se lleva a cabo en términos de aumento de capacidad que se puede lograr cuando la capacidad de la red de backhaul por satélite se utiliza para el desborde de tráfico, teniendo en cuenta la ubicación de la capacidad del satélite en diferentes niveles de agregación de tráfico y considerando una correlación espacial de la demanda de tráfico. Posteriormente, el trabajo de tesis presenta el desarrollo de estrategias y algoritmos de TE basados en SDN que explotan la capacidad dinámicamente orientable del satelite, provista con fines de resiliencia para utilizar de mejor manera la capacidad satelital al maximizar la utilidad de red en condiciones de falla y no falla en algunos enlaces terrestres, y bajo la consideración de tráfico elástico, inelástico y de unidifusión y multidifusión. El análisis de rendimiento se lleva a cabo en términos de tasas de rechazo, de utilidad, y equidad en comparación con las aplicaciones de TE no basadas en SDN. Finalmente, basado en la definición del diseño de marco de arquitectura, el trabajo de tesis presenta una Prueba de concepto (PoC) experimental y la validación de una solución de integración de enlaces de backhaul satelital-terrestre que se basa en las tecnologías SDN para la realización de aplicaciones de TE de extremo a extremo (E2E) en redes de backhaul móviles, evaluando la viabilidad de la solución propuesta de integración basada en SDN en un entorno práctico de laboratorio que combina el uso de equipos y software comerciales, orientados a la experimentación y emulación.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>This paper presents the results of a feasibility study undertaken by the University of Salzburg (Austria), investigating the autonomous acquisition of environmental data in a global network. A suggested application which is used as the basis of this paper is a volcano monitoring system which would be able to track the activity of a volcano and act as a disaster warning system. The background Volcano observation data required for such a system is covered, before discussing the concepts for sensor data acquisition, storage and processing. A final analysis is then presented of the opportunities for the transmission by packet radio (both terrestrial and satellite).

L’augmentation et le renforcement des usages d’Internet rend nécessaire l’évolution des réseaux existants. Cependant, on constate de fortes inégalités entre les zones urbaines, bien desservies et qui concentrent l’essentiel des investissements, et les zones rurales, mal desservies etdélaissées. Face à cette situation, les utilisateurs de ces zones se tournent vers d’autres moyensd’accès, et notamment vers les accès Internet par satellite. Cependant, ces derniers souffrentd’une limitation qui est le délai important induit par le temps de propagation du signal entre la terre et l’orbite géostationnaire. Dans cette thèse, nous nous intéressons à l’utilisation simultanée d’un réseau d’accès terrestre, caractérisé par un faible débit et un faible délai, et d’un réseau d’accès satellite, caractérisé par une forte latence et un débit plus important. D’autre part, les réseaux dediffusion de contenus ou CDNs, constitués d’un grand nombre de serveurs de cache, apportentune réponse à l’augmentation du trafic et des besoins en termes de latence et de débit.Cependant, localisés dans les réseaux de cœur, les caches restent éloignés des utilisateurs etn’atteignent pas les réseaux d’accès. Ainsi, les fournisseurs d’accès Internet (FAI) se sontintéressés au déploiement de ces serveurs au sein de leur propre réseau, que l’on appelle alorsTelCo CDN. La diffusion des contenus nécessite idéalement l’interconnexion des opérateurs CDNavec les TelCo CDNs, permettant ainsi la délégation de la diffusion à ces derniers. Ils sont alorsen mesure d’optimiser la diffusion des contenus sur leur réseau dont ils ont une meilleureconnaissance. Ainsi, nous nous intéresserons à l’optimisation de la livraison de contenus sur unréseau hybride satellite / terrestre intégré à une chaîne de livraison CDN. Nous nous attacheronsdans un premier temps à décrire une architecture permettant, grâce à l’interconnexion de CDNs,de prendre en charge la diffusion des contenus sur le réseau hybride. Dans un second temps,nous étudierons l’intérêt de la connaissance des informations apportées par le contexte CDN pour le routage sur une telle architecture. Dans ce cadre, nous proposerons un mécanisme de routage fondé sur la taille des contenus. Finalement, nous montrerons la supériorité de notre approche sur l’utilisation du protocole de transport multichemin MP-TCP<br>The increase and reinforcement of Internet uses make necessary to improve existing networks.However, we observe strong inequalities between urban areas, well served and which concentratethe major part of investments, and rural areas, underserved and forkasen. To face this situation,users in underserved areas are moving to others Internet access, and in particular satellite Internetaccess. However, the latter suffer from a limitation which is the long delay induced by thepropagation time between the earth and the geostationnary orbit. In this thesis, we are interresedin the simultaneous use of a terrestrial access network, characterized by a low delay and a lowthroughput, and a satellite access network, characterized by a high throughput and an long delay.Elsewhere, Content Delivery Networks (CDNs), consisting of a large number of cache servers,bring an answer to the increase in trafic and needs in terms of latency and throughput. However,located in core networks, cache servers stay far from end users and do not reach accessnetworks. Thus, Internet Service Providers (ISPs) have taken an interest in deploying their ownCDNs, which will be referred to as TelCo CDNs. The content delivery ideally needs theinterconnection between CDN operators and TelCo CDNS, allowing the delegation of the contentdelivery to the TelCo CDNs. The latter are then able to optimize the content delivery on theirnetwork, for which they have a better knowledge. Thus, we will study the optimization of thecontents delivery on a hybrid satellite / terrestrial network, integrated in a CDN delivery chain. Wewill initially focus on the description of a architecture allowing, thanks to a CDN interconnection,handling contents delivery on the hybrid network. In a second stage, we will study the value of theinformation provided by the CDN context in the routing on such architecture. In this framework, wewill propose a routing mechanism based on contents size. Finally, we will show the superiority ofour approach over the multipath transport protocol MP-TCP

博士<br>國立中央大學<br>資訊工程研究所<br>92<br>The rapid proliferation of Internet over recent years has extremely impacted the service offering. Issues of limited capacity, non-global coverage, routing and congestion challenged the availability of desired services. Particularly, burst and tremendous mass of multimedia traffic might unexpectedly congest the terrestrial network to restrict the provisions of services with desired Quality of Services (QoS). The resource utilization is then degraded. Furthermore, this unexpected congestion together with limited network bandwidth would severely challenge the provision of multicasting services that most applications adopt such as video conferencing and distance learning, especially in the case that the multicast subscribers are widely scattered. These issues have roused the research community’s interest in the integration of new satellite technologies with terrestrial multimedia networks. The satellite inherent distance insensitive network could extend the terrestrial capacity and achieve the global coverage. In addition, the terrestrial burst traffic could further detour the congestion areas by delivered to destinations over satellite networks. The unexpected congestion is then managed and the resource utilization is promoted as well. Therefore, in this dissertation, we introduce a global Satellite-Terrestrial network (ST network) configuration that integrates the broadband satellite network with the conventional terrestrial network by gateway points. Based on this platform, a resource-aware routing scheme, the Smart Hierarchical Routing Protocol (SHRP), is proposed to provide connections that detours the congestion areas. These congestion-avoided routing paths are provided for the emergent delivery or the alternatives once the terrestrial routes fail (fault tolerance). A novel proposed Spoofing RSVP Protocol (SRP) is further applied to guarantee the end-to-end QoS. In addition, in order to provide the multicast services, an Adaptive Multicast Routing (AMRST) protocol was proposed. Besides, a Spoofing Re-configurable Reliable Multicast Routing Protocol (SReRM) was further proposed to provide congestion-avoided reliable multicast services. The experimental results validate that these protocols provide excellent throughput, scalability and flexibility to this convergent network.

博士<br>國立中正大學<br>電機工程研究所<br>101<br>Multimedia Broadcast Multicast Service (MBMS) will be an important service in future mobile communication systems. Since satellite system has large coverage area and capability for broadcasting, satellite-terrestrial wireless network, satellite system combined with terrestrial network, will be an efficient way to support MBMS. With the aid of simpler transmitter and receiver, cooperative communication assisted by relay node can achieve diversity gain similar to multiple input multiple output (MIMO) technique. This dissertation focused on system performance of cooperative communication over satellite-terrestrial wireless network. First, it discussed system performance of cooperative communications using selective decode-and-forward protocol. The system model includes one source node, multiple relay nodes, and one destination node. Here three channel models were considered: both satellite-terrestrial link and relay-destination link modeled as Rayleigh fading channels, satellite-terrestrial link modeled as Rician fading channel and relay-destination link modeled as Rayleigh fading channel, and satellite-terrestrial link modeled as (Rayleigh+Nakagami) fading channel and relay-destination link modeled as Rayleigh fading channel. The probability density function (PDF) of the maximum ratio combining signal-to-noise ratio (SNR) in destination node was carried out for these three channel models, and then moment generating function (MGF) was derived. According to the MGF, the average symbol error probability of MPSK signals was acquired. Besides, the system performance with power sharing issue among relay nodes was further investigated. Second, based on the numerical results of the previous chapter, it was found that the average symbol error probability decreases as the number of relay node increases; however, more system resource was needed to complete a symbol transmission. The system resource was referred to the transmission time-slot in time-division multiple access systems and transmission frequency band in frequency-division multiple access systems. Increase of the transmission time-slots led to more transmission delay, while more transceivers in the destination would be required if the signals were to be received from several transmission frequency bands.. To save system resource, the performance analyses under best-relay selection was carried out using order statistic method. Third, system performance of cooperative communications using amplify-and-forward relaying protocol was analyzed. In this chapter, two channel models were considered: both satellite-terrestrial link and relay-destination link modeled as Rayleigh fading channels as well as satellite-terrestrial link modeled as Rician fading channel and relay-destination link modeled as Rayleigh fading channel. It was rather complicated to analyze the system performance with the latter channel model. Instead of deriving the exact expression of average symbol error probability, this research carried out the lower bound of average symbol error probability. Finally, this research discussed relay location selection in satellite-terrestrial wireless networks. The relaying protocol adopted was amplify-and-forward. It is assumed that the destination was unable to receive the signal from the satellite directly. By figuring out maximum capacity of this system, this research figured out the relationship between the relay location, the altitude of satellite, and the path-loss exponents.

碩士<br>國立暨南國際大學<br>通訊工程研究所<br>99<br>Cooperative communication uses the concept of space diversity to follow the multiple-input multiple-output communication system. The uses of relay stations make the transmission more reliable and higher data rate. Compared with the multi-input multi-output system, cooperative communication can reduce the hardware design complexity and cost. In recent years the development of wireless communication, the cooperative multi-hop relay station assisted technologies improve the performance and services range of wireless systems, and the use of relay stations a virtual antenna for diversity gain improve the link reliability. In this thesis, we study the downlink cooperative communication systems of hybrid satellite-terrestrial networks. The system architecture includes a source, a relay station with Amplify-and-Forward (AF) strategy and a destination. According to the proposed channel environment, we derive analytical expressions for the probability density function (PDF) and the moment generating function (MGF) of receiver's signal-to-noise ratio (SNR) at the destination, to obtain the average symbol error probability (Average Symbol Error Probability, ASEP) of M-QAM. Finally, we extend the issue to the environment with a single source, multiple relay stations and single destination. To maximum the SNR at the destination, the selection the best relay stations for amplify-and-forward (S-AF) is explored for multiple relay stations. The formula derived for each of the issues in this thesis are verified by using the computer simulation.

碩士<br>國立暨南國際大學<br>通訊工程研究所<br>99<br>Hybrid Satellite-Terrestrial Network (HSTN) is the integration of the Satellite Communication System (SCS) and the Ground Communication Network (GCN). It can provide a communication platform without dead zone for Multimedia Broadcast and Multicast Service (MBMS) by using the advantages of the SCS and the GCN. The cooperative relaying strategies for terrestrial stations make it possible to achieve the diversity gain similar to the Multiple Input Multiple Output (MIMO) technique with less complexity of transmitters and receivers. The Space-time Coding (STC) technique can also use the time diversity and the spatial diversity simply. In the thesis, we took the Rayleigh Fading channel model as the transmitting channel of the satellite and the terrestrial first. And then we took the Ricean Fading channel model as the transmitting channel of the satellite. Because the signals transmitted by the satellite have a strong Line of Sight (LOS) property. Then we applied two relaying strategies, Amply-and-Forward (AF) and Decode -and-Forward (DF), separately on the terrestrial relay stations with Distributed Space-time Coding (DSTC). And at the receiver of the destination, we used the Selective Combining (SC) method and the Maximum Ratio Combining (MRC) method separately. We compared the effect of Diversity Gain caused by the two signal combining methods with the Symbol v Error Rate (SER). We also did the power allocation of the satellite and the relays. By the simulations, we found out that the system has the better bandwidth efficiency and the SER is lower. The system performance was improved.

Despite air travel has not grown as predicted, air travel is still expected to rise to just less than doubling the current figure by 2030. This creates an urging need to develop more efficient Air Traffic Management (ATM) solutions. Around the globe, research and development initiatives have been launched to modernize the air traffic control infrastructures. These modernized infrastructures will be built around continuous information gathering, sharing and transferring of data between aircraft and air navigation service providers and airports ground infrastructure, which will be difficult for current aeronautical communications systems to handle. As a result, new communication infrastructures are required to manage future aeronautical communication traffic demand. This paper proposes an integrated aeronautical communication architecture consisting of four radio access technologies for communications between aircrafts and ground Aeronautical Telecommunication Network (ATN). The design and implementation of a Joint Radio Resource Management (JRRM) framework to manage these radio resources are discussed. The design is verified by a proof-of-concept JRRM prototype which is developed for the management of radio resource between the Inmarsat Broadband Global Area Network (BGAN) and the Aeronautical Mobile Airport Communication System (AeroMACS).

No<br>In the telecommunication networks the introduction of Next Generation Wireless Networks (NGWN) has been described as the most significant change in wireless communication. The convergence of different access networks in NGWN allows generalized mobility, consistency and ubiquitous provision of services to mobile users. The general target of NGWN is to transport different types of information like voice, data, and other media like video in packets form like IP. The NGWNs offer significant savings in costs to the operators along with new and interesting services to the consumers. Major challenges in NGWN are efficient resource utilization, maintaining service quality, reliability and the security. This paper proposes a solution for seamless load aware Radio Access Technology (RAT) selection based on interworking of different RATs in NGWN. In this paper novel load balancing algorithms have been proposed which have been simulated on the target network architecture for TCP data services. The IEEE 802.21 Media Independent Handover (MIH) is utilized in load balancing specifically for mobility management, which enable low handover latency by reducing the target network detection time. The proposed method considers the network type, signal strength, data rate and network load as primary decision parameters for RAT selection process and consists of two different algorithms, one located in the mobile terminal and the other at the network side. The network architecture, the proposed load balancing framework and RAT selection algorithms were simulated using NS2. Different attributes like load distribution in the wireless networks and average throughput to evaluate the effects of load balancing in considered scenarios.

No<br>The ever increasing user QoS demands and emergence of new user applications make job of network operators and manufacturers more challenging for efficiently optimisation and managing radio resources in radio the radio resources pools of different wireless networks. A group of strategies or mechanisms which are collectively responsible for efficient utilisation of radio resources available within the Radio Access Technologies (RAT) are termed as Radio Resource Management (RRM). The traditional RRM strategies are implemented independently in each RAT, as each RRM strategy considers attributes of a particular access technology. Therefore traditional RRM strategies are not suitable for heterogeneous wireless networks. Common Radio Resource Management (CRRM) or joint radio resource management (JRRM) strategies are proposed for coordinating radio resource management between multiple RATs in an improved manner. In this paper a fuzzy algorithm based CRRM strategy is presented to efficiently utilise the available radio resources in heterogeneous wireless networks. The proposed CRRM strategy balances the load in heterogeneous wireless networks and avoids the unwanted congestion situation. The results such as load distribution, packet drop rate and average throughput at mobile nodes are used to demonstrate the benefits of load balancing in heterogeneous wireless networks using proposed strategy.

博士<br>國立中正大學<br>電機工程研究所<br>102<br>In this thesis, we have made an analysis of the previous research on terrestrial station grouping method in satellite-terrestrial cooperative wireless network, and proposed a new grouping method for the network. The proposed method not only increases the total system channel capacity but also saves unnecessary power wastage in the terrestrial stations. The new method focuses on finding out the best two terrestrial stations and on adjusting appropriate frequencies so that the subsequent process of the Space-Time Coding could improve the effect of channel fading. Factors that helped improve the overall system channel capacity were also discussed in the article. The results of different grouping algorithms were compared as well. The alternative grouping method proposed in this thesis is suitable for the Multimedia Broadcast Multicast Service (MBMS). It can easily be combined with the OFDM technique to improve the total system capacity and to increase the variety of the content channels as well, thus making the MBMS more attractive to the customers.

No<br>For decades, the development of the Internet was driven by the purpose of providing applications to non-mobile users. No specific Quality of Service (QoS) requirement is necessary, other than ensuring reliability in the end-to-end data transfers. As such, best effort service model was deemed more than appropriate to satisfy the users' needs. Nevertheless, the scenario has changed in the last few years. A new population of nomadic users, who requires access to Internet services regardless of their location and mode of transportation is growing, while new typologies of Internet applications are being continuously developed, in which best effort service level may no longer be adequate. The SUITED project has been devised to address the emerging issues generated by this new and challenging scenario. SUITED aims at contributing towards the design and deployment of the Global Mobile Broadband System (GMBS), a unique satellite/terrestrial infrastructure, which will ensure that nomadic users have access to Internet services with a negotiated QoS. An overview of the main results achieved in the SUITED project is provided in this article. Some of the most innovative solutions developed by the SUITED team for the joint management of global mobility and end-to-end QoS support are presented. The SUITED demonstrator platform, which was developed to validate the system specifications, is also described. Finally, the results of the experimental measurement campaigns carried out with this platform are reported.

No<br>This paper presents a Master/Slave redundancy mechanism for the airborne Integrated Modular Radio to improve the reliability of the joint radio resource management (JRRM) system. The proposed mechanism adopts keep-alive heart beat messages and real time information synchronization to ensure a smooth switchover in the event of a platform failure. To enhance the scalability and decoupling of the system, the proposed hot swap solution makes the JRRM switchover transparent to both the higher layers and the lower layers. The experiment results and the performance obtained from the test-bed has proved the validity of the solution.

This work investigates the relationship of urbanization, population density and meteorological variables (temperature & precipitation) on groundwater storage for the selected study regions in India. Variations in groundwater storage are analyzed using Gravity Recovery and Climate Experiment (GRACE) derived variations of Terrestrial Water Storage (ΔTWS). In the first part of the thesis, we have examined and established the correspondence between GRACE ΔTWS and groundwater level for selected study sites across different geographic regions in India using Linear regression, Support Vector Regression and Artificial Neural Network models. It has been observed in our study that ΔTWS is a highly significant predictor of GWL and the amount of variation in GWL that could be explained with the help of ΔTWS varies from 36.48% to 74.28%. Next, we have studied changes in ΔTWS across India from January 2003 to January 2017 and have found evidence of its significant declining trend (−0.912 ± 0.455 cm/year) in the northern part of India encompassing Ganga-Brahmaputra river basin and North-West India. As ΔTWS serves as a strong indicator for groundwater storage, its declining trend implies significant depletion of groundwater in this belt during this period. Interestingly, for the same time period, this particular belt with declining ΔTWS has observed a significant positive trend in precipitation and no significant trend for temperature. Also, for the mentioned time period, we’ve observed a higher growth rate in agricultural electricity consumption and population density in this region compared to the rest of India. These observations strongly suggest that the depletion of TWS in this region could be primarily attributed to anthropogenic activities rather than to changes in meteorological variables. Motivated by this observation, we investigate further the relationship between ΔTWS & urbanization. To measure the temporal changes in urbanization, we’ve developed an index PB1BI (Powered B1 Built Up Index) to classify pixels from Landsat7 images. We have compared the performance of PB1BI with existing indices and machine learning methods (SVM & ANN). Validation with manually verified test pixels and qualitative assessments indicate that PB1BI outperforms existing indices and it’s performance matches with that of ML methods. In addition to the existing Otsu thresholding method, this study has proposed a thresholding method using bootstrapping. For all the indices compared test pixel, accuracy measures show that the bootstrapping method works better than the Otsu method. Further, the multi-temporal analysis conducted in this study has demonstrated consistent performance of PB1BI. To reduce misclassification of “river sand” pixels as “built-up” ones while classifying “built-up” pixels from Landsat7 satellite imagery, we’ve developed another index-based methodology BRSSI (Built-Up & River Sand Separation Index) to separate these two land cover types. The performance of this index which is computationally inexpensive is comparable to that of the support vector machine. Both quantitative & qualitative assessment for the effectiveness of the developed methodology confirms a significant reduction of the misclassification. Finally, to understand the relationship of the urbanization & population density with ΔTWS, panel data regression analysis was conducted for 9 selected study sites across different geographic locations in India for the period 2003-2017. The newly developed algorithms (PB1BI & BRSSI) have been applied jointly to compute the percentage of urbanization from Landsat7 imagery. Population density, precipitation and temperature along with urbanization, have been used as explanatory variables in the panel data regression for understanding the variations in ΔTWS. Results suggest that precipitation & urbanization exhibit significant positive & negative effects respectively with ΔTWS and together they could explain 66.93% of the variability in the data. Similarly, it has been observed that interaction effect of urbanization & population density exhibit a significant negative association with GRACE ΔTWS and 77.76% of the variation in ΔTWS could be explained with the help of the same along with precipitation. This indicates the significant effect of an increase in anthropogenic indicators like urbanization & population density on the groundwater storage.