Call admission control for interactive multimedia satellite networks.

Master of Science in Engineering (Electronic). University of KwaZulu-Natal, Durban 2015.Satellite communication has become an integral component of global access communication network due mainly to its ubiquitous coverage, large bandwidth and ability to support for large numbers of users over fixed and mobile devices. However, the multiplicity of multimedia applications with diverse requirements in terms of quality of service (QoS) poses new challenges in managing the limited and expensive resources. Furthermore, the time-varying nature of the propagation channel due to atmospheric and environmental effects also poses great challenges to effective utilization of resources and the satisfaction of users’ QoS requirements. Efficient radio resource management (RRM) techniques such as call admission control (CAC) and adaptive modulation and coding (AMC) are required in order to guarantee QoS satisfaction for user established connections and realize maximum and efficient utilization of network resources. In this work, we propose two CAC policies for interactive satellite multimedia networks. The two policies are based on efficient adaptation of transmission parameters to the dynamic link characteristics. In the first policy which we refer to as Gaussian Call Admission Control with Link Adaptation (GCAC-LA), we invoke the central limit theorem to statistically multiplex rate based dynamic capacity (RBDC) connections and obtain an aggregate bandwidth and required capacity for the multiplex. Adaptive Modulation and Coding (AMC) is employed for transmission over the time-varying wireless channel of the return link of an interactive satellite network. By associating users’ channel states to particular transmission parameters, the amount of resources required to satisfy user connection requirements in each state is determined. Thus the admission control policy considers in its decision, the channel states of all existing and new connections. The performance of the system is investigated by simulation and the results show that AMC significantly improves the utilization and call blocking performance by more than twice that of a system without link adaptation. In the second policy, a Game Theory based CAC policy with link adaptation (GTCAC-LA) is proposed. The admission of a new user connection under the GTCAC-LA policy is based on a non-cooperative game that is played between the network (existing user connections) and the new connection. A channel prediction scheme that predicts the rain attenuation on the link in successive intervals of time is also proposed. This determines the current resource allocation for every source at any point in time. The proposed game is played each time a new connection arrives and the strategies adopted by players are based on utility function, which is estimated based on the required capacity and the actual resources allocated. The performance of the CAC policy is investigated for different prediction intervals and the results show that multiple interval prediction scheme shows better performance than the single interval scheme. Performance of the proposed CAC policies indicates their suitability for QoS provisioning for traffic of multimedia connections in future 5G networks

A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future

A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature review. We highlight the unrealized potential of HAPS systems and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a cost-effective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are described. The notable contributions of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The extensive overview of the literature we provide is crucial for substantiating our vision that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial

Queueing Networks for Vertical Handover

PhDIt is widely expected that next-generation wireless communication systems will be heterogeneous, integrating a wide variety of wireless access networks. Of particular interest recently is a mix of cellular networks (GSM/GPRS and WCDMA) and wireless local area networks (WLANs) to provide complementary features in terms of coverage, capacity and mobility support. If cellular/ WLAN interworking is to be the basis for a heterogeneous network then the analysis of complex handover traffic rates in the system (especially vertical handover) is one of the most essential issues to be considered. This thesis describes the application of queueing-network theory to the modelling of this heterogeneous wireless overlay system. A network of queues (or queueing network) is a powerful mathematical tool in the performance evaluation of many large-scale engineering systems. It has been used in the modelling of hierarchically structured cellular wireless networks with much success, including queueing network modelling in the study of cellular/ WLAN interworking systems. In the process of queueing network modelling, obtaining the network topology of a system is usually the first step in the construction of a good model, but this topology analysis has never before been used in the handover traffic study in heterogeneous overlay wireless networks. In this thesis, a new topology scheme to facilitate the analysis of handover traffic is proposed. The structural similarity between hierarchical cellular structure and heterogeneous wireless overlay networks is also compared. By replacing the microcells with WLANs in a hierarchical structure, the interworking system is modelled as an open network of Erlang loss systems and with the new topology, the performance measures of blocking probabilities and dropping probabilities can be determined. Both homogeneous and non-homogeneous traffic have been considered, circuit switched and packet-switched. Example scenarios have been used to validate the models, the numerical results showing clear agreement with the known validation scenarios

A Connection Admission Control Framework for UMTS based Satellite Systems.An Adaptive Admission Control algorithm with pre-emption control mechanism for unicast and multicast communications in satellite UMTS.

In recent years, there has been an exponential growth in the use of multimedia applications. A satellite system offers great potential for multimedia applications with its ability to broadcast and multicast a large amount of data over a very large area as compared to a terrestrial system. However, the limited transmission capacity along with the dynamically varying channel conditions impedes the delivery of good quality multimedia service in a satellite system which has resulted 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 CAC framework which maximizes the utilization of the scarce radio resources available in the satellite and at the same time increases the performance of the system for a UMTS based satellite system supporting unicast and multicast traffic. The design of the system architecture for a UMTS based satellite system is presented. Based on this architecture, a CAC framework is designed consisting of three different functionalities: the admission control procedure, the retune procedure and the pre-emption procedure. The joint use of these functionalities is proposed to allow the performance of the system to be maintained under congestion. Different algorithms are proposed for different functionalities; an adaptive admission control algorithm, a greedy retune algorithm and three pre-emption algorithms (Greedy, SubSetSum, and Fuzzy). A MATLAB simulation model is developed to study the performance of the proposed CAC framework. A GUI is created to provide the user with the flexibility to configure the system settings before starting a simulation. The configuration settings allow the system to be analysed under different conditions. The performance of the system is measured under different simulation settings such as enabling and disabling of the two functionalities of the CAC framework; retune procedure and the pre-emption procedure. The simulation results indicate the CAC framework as a whole with all the functionalities performs better than the other simulation settings

A Handover Strategy in the LEO Satellite-Based Constellation Networks with ISLs

Abstract A new handover strategy named minimal-hops handover (MHH) Received 2003-06-05 Due to various economic and technical constraints, terrestrial mobile networks can only provide communication services with a limited coverage. Recently, in response to increasing demand of real-time multimedia services and the truly global coverage required by personal communication services (PCS), there is a vast research on non-geostationary orbit (NGSO) satellites systems, especially on low earth orbit (LEO) satellite constellations with an altitude between 700 km and 1 500 km. LEO satellite constellations equipped with inter-satellite links (ISLs), such as Iridium, Teledesic, Courier and so on, usually have onboard switching (OBS) and onboard routing (OBR) facilities and form an independent network in space. Direct connectivity between any pair of satellite mobile users can be achieved through the satellites and ISLs without any essential usage of the terrestrial core network. For the wide application prospect, they have already been the focus of the research on the satellite communication systems Key words low earth orbit(LEO) satellite-based constellation networks; time propagation delay; quality of services (QoS); inter-satellite link (ISL); inter-satellite handover In the LEO constellations, although handover procedure is closely correlated with rerouting, almost all the existing strategies pay more attention to the handovers themselves and ignore the rerouting. In this way, this paper proposes a new strategy name

Integrating LEO Satellite Constellations into Internet Backbone

Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures.Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures

A Threshold Based Handover Triggering Scheme in Heterogeneous Wireless Networks

The widespread popularity of Wireless Local Area Network (WLAN) is recognized as an effective approach to complementing cellular networks for the high data rate and cost effective connectivity delivered to mobile users. Efficient handover and offloading schemes for integrated WLAN and cellular networks, referred to as Heterogeneous Wireless Networks, have thus attracted lots of attentions from both academia and industry. This paper proposes a novel Multiple-Threshold based Triggering (MTT) scheme for Cellular-to-WLAN handover control. Aiming at minimizing the probability of handover failures and unnecessary handovers, three thresholds are calculated based on a variety of network parameters such as system performance requirements, radius of the WLAN coverage, user mobility and handover delays. The thresholds are then compared against the predicted user residence time and estimated channel holding time inside WLAN to make vertical handover decisions (VHDs). Simulations were carried out to evaluate the effectiveness of MTT and results show that MTT minimizes handover failures and avoids unnecessary handovers in integrated cellular and WLAN networks, thus providing satisfactory Quality of Service (QoS) to users and improving system resource utilization

Radio Resource Management for Satellite UMTS. Dynamic scheduling algorithm for a UMTS-compatible satellite network.

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