The third generation of mobile communication systems introduce interactive Multicast and Unicast multimedia services at a fast data rate of up to 2 Mbps and is expected to complete the globalization of the mobile telecommunication systems. The implementation of these services on satellite systems, particularly for broadcast and multicast applications to complement terrestrial services is ideal since satellite systems are capable of providing global coverage in areas not served by terrestrial telecommunication services. However, the main bottleneck of such systems is the scarcity of radio resources for supporting multimedia applications which has resulted in the rapid growth in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a dynamic scheduling framework and algorithm that can improve the overall performance of the radio resource management strategy of a UMTS compatible satellite network, taking into account the unique characteristics of wireless channel conditions. This thesis will initially be focused on the design of the network and functional architecture of a UMTS -compatible satellite network. Based on this architecture, an effective scheduling framework is designed, which can provide different types of resource assigning strategies. A functional model of scheduler is defined to describe the behaviours and interactions between different functional entities. An OPNET simulation model with a complete network protocol stack is developed to validate the performance of the scheduling algorithms implemented in the satellite network. Different types of traffic are considered for the OPNET simulation, such as the Poisson Process, ONOFF Source and Self Similar Process, so that the performance of scheduling algorithm can be analyzed for different types of services. A novel scheduling algorithm is proposed to optimise the channel utilisation by considering the characteristics of the wireless channel, which are bursty and location dependent. In order to overcome the channel errors, different code rates are applied for the user under different channel conditions. The proposed scheduling algorithm is designed to give higher priority to users with higher code rate, so that the throughput of network is optimized and at the same time, maintaining the end users¿ service level agreements. The fairness of the proposed scheduling algorithm is validated using OPNET simulation. The simulation results show that the algorithm can fairly allocate resource to different connections not only among different service classes but also within the same service class depending on their QoS attributes. / Inmarsat Global Ltd. BGAN and the European Space Agency (ESA)

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No / The last decade has seen an exponential rise in the use of wireless sensor networks (WSNs) in various applications. While these have been primarily used on their own, researchers are now looking into ways of integrating these WSNs with other existing communication technologies. One such network is the satellite network which provides significant advantage in providing communication access to remote locations due to their inherent large coverage areas. Combining WSNs and satellite will enable us to perform efficient remotely monitoring in areas where terrestrial networks may not be present. However in such a scenario, the placement of sensor nodes is crucial in order to ensure efficient routing and energy-efficiency. This paper presents four network architectures for sensor-satellite hybrid networks, sensor-satellite direct communication, connections via a gateway node employing random node layout, grid-based node layout and cluster-based node layout with data aggregation. These architectures were simulated using network simulator 2 (ns-2) and then their packet loss rate, average end-to-end packet delay, and overall energy consumption were compared. The paper concludes by proposing a suitable network topology for environmental monitoring applications.

Satellite systems have the advantage of global coverage and offer a solution for providing broadband access to end users. Local terrestrial networks and terminals can be connected to the rest of the world over Low Earth Orbit (LEO) satellite networks simply by installing small satellite interfaces. With these properties, satellite systems play a crucial role in the global Internet to support real-time and non-real-time applications. Routing in satellite networks, and the integration of satellite networks and the terrestrial Internet are the key issues to support these services. Furthermore, the developments in space technologies enable the realization of deep-space missions such as Mars exploration. The Interplanetary Internet is envisioned to provide communication services for scientific data delivery and navigation services for the explorer spacecrafts and orbiters of future deep-space missions. The unique characteristics posed by deep-space communications call for different research approaches from those in terrestrial networks. The objective of this research is to develop advanced architectures and efficient routing protocols for satellite and space networks to support applications with different traffic types and heterogeneous quality-of-service (QoS) requirements. Specifically, a new QoS-based routing algorithm (QRA) is proposed as a connection-oriented routing scheme to support real-time multimedia applications in satellite networks. Next, the satellite grouping and routing protocol (SGRP) is presented as a unicast routing protocol in a two-layer satellite IP network architecture. The border gateway protocol - satellite version (BGP-S) is then proposed as a unified routing protocol to accomplish the integration of the terrestrial and satellite IP networks at the network layer. Finally, a new routing framework, called the space backbone routing (SBR), is introduced for routing through different autonomous regions in the Interplanetary Internet. SBR provides a self-contained and scalable solution to support different traffic types through the Interplanetary Internet.

This thesis introduces a framework for enhancing DTN (Delay-/Disruption-Tolerant Networking) routing in dynamic LEO satellite constellations based on the prediction of contacts. The solution is developed with a clear focus on the requirements imposed by the 'Ring Road' use case, mandating a concept for dynamic contact prediction and its integration into a state-of-the-art routing approach. The resulting system does not restrict possible applications to the 'Ring Road,' but allows for flexible adaptation to further use cases. A thorough evaluation shows that employing proactive routing in concert with a prediction mechanism offers significantly improved performance when compared to alternative opportunistic routing techniques.

Low Earth Orbit (LEO) satellite networks have revolutionized space internet access, offering better network performance than previous alternatives. While being the best option for space internet access, it does not yet compete with terrestrial networks in latency and bandwidth. The QUIC transport protocol was developed for Hypertext Transfer Protocol (HTTP) to reduce page load times and work better in low-bandwidth and high-loss networks than the Transmission Control Protocol (TCP). Studies have shown that QUIC performs well for small file sizes, which can be achieved by using compression. This thesis investigates whether combining QUIC as a general data transfer protocol with lossless compression enhances encrypted data transmission in a LEO satellite network. To test this, a program consisting of a client and server deployed on a LEO satellite network emulator is developed, where files with increasing sizes are compressed and sent using both QUIC and TCP in various network conditions. Results indicate that QUIC should be paired with lossless compression for file sizes up to 1MB. It should not be implemented for file sizes above 1MB in low-loss and high-bandwidth conditions, while it can be implemented in medium to poor conditions.

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.

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.