Design and Analysis of Phased Array Antenna Beam Steering For Satellite Tracking

Nowadays achievements on mobile satellite system (MSS) communication give a great concern for research in global wireless communication fields. This has prompted the development of several Non Geostationary Earth Orbit (Non-GEO) satellite systems that promises worldwide connectivity for real-time communications. The mobility of Non-GEO satellite systems require a high directivity satellite tracking technique and a reliable inter satellite handover algorithm to ensure that connectivity between two end users are not interrupted as a result of satellite movement. In this thesis, phased array antenna has been proposed to obtain high directivity beam for satellite tracking. In order to do this, the phased array antenna mathematical model has been developed. This mathematical model has demonstrated that a narrow beam with high directivity could be generated. By changing the phase of the exciting currents in each element of antenna array, the radiation pattern could be varied through space. Thus, the generation of multiple and steerable beams also could be depicted by varying the phase shift of phase shifter with appropriate spacing between each elements to be sufficiently large. It is also shown here that the generated radiation beamwidth can be controlled by varying the number of antenna elements. It was found that the beamwidth reduces exponentially with the increment of the number of antenna elements

Routing algorithm for provision of end-to-end delay QoS for low earth orbit satellite networks

Master'sMASTER OF ENGINEERIN

Proactive TCP mechanism to improve Handover performance in Mobile Satellite and Terrestrial Networks

Emerging standardization of Geo Mobile Radio (GMR-1) for satellite system is having strong resemblance to terrestrial GSM (Global System for Mobile communications) at the upper protocol layers and TCP (Transmission Control Protocol) is one of them. This space segment technology as well as terrestrial technology, is characterized by periodic variations in communication properties and coverage causing the termination of ongoing call as connections of Mobile Nodes (MN) alter stochastically. Although provisions are made to provide efficient communication infrastructure this hybrid space and terrestrial networks must ensure the end-to-end network performance so that MN can move seamlessly among these networks. However from connectivity point of view current TCP performance has not been engineered for mobility events in multi-radio MN. Traditionally, TCP has applied a set of congestion control algorithms (slow-start, congestion avoidance, fast retransmit, fast recovery) to probe the currently available bandwidth on the connection path. These algorithms need several round-trip times to find the correct transmission rate (i.e. congestion window), and adapt to sudden changes connectivity due to handover. While there are protocols to maintain the connection continuity on mobility events, such as Mobile IP (MIP) and Host Identity Protocol (HIP), TCP performance engineering has had less attention. TCP is implemented as a separate component in an operating system, and is therefore often unaware of the mobility events or the nature of multi-radios' communication. This paper aims to improve TCP communication performance in Mobile satellite and terrestrial networks.Comment: 5 pages, 2 figure

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

Handover Management In Mobile Satellite Communications

Mobile satellite communication offers vast coverage area with moderate bandwidth demands. However, in mobile satellite communication using Low Earth Orbits (LEO) satellite service, handover frequently occurs due to high velocity and large number of mobile satellites. With increase demand of multimedia traffic, an optimum utilization of network resources has been investigated. To accommodate and maintain Quality of Service (QoS) of handover calls in mobile satellite communication, priority for handover calls are applied. Traffic parameters of traffic arrival rate, traffic duration and priority among traffic applications are introduced. Traffic applications of type voice, video and data are observed and analysis of traffic behavior on handover has been done. An optimum set of channels to serve the different traffic types is proposed after considering the handover initiation and handover execution criteria. The algorithm proposes a more accurate measurement of handover initiation angle, introduced as look-up angle, which further reduces handover rate and successfully conserve the network resources

Inter-Satellite Link Channel Management For Mobile Satellite Systems

Low Earth Orbit (LEO) satellite constellations are foreseen as appropriate alternatives to the geostationary satellite systems for providing global personal communications services (PCS). Compared to geostationary satellites, these constellations offer a significantly smaller round trip delay between earth and space segments. Furthermore, the use of inter-satellite links (ISLs) has been identified as a means to provide global connectivity in space, thereby enhancing system autonomy and flexibility, and has been retained in the design of systems like Teledesic and SkyBridge. From a network point of view, a major benefit of a ISL subnetwork in space lies in the possibility to transport long distance traffic over reliable and high capacity connections, thus forming a good base for ATM (asynchronous transfer mode) operation. With the development of the third generation (3G) and fourth generation (4G) wireless networks, ATM is regarded as one of the potential promising candidates for providing QoS guaranteed broadband telecommunication services. It is possible to integrate the mobile satellite and A TM by applying the inter/intra satellite links (ISLs) as the physical layer of WATM and considering a connection between two satellites as a virtual path connection (VPC) in ATM

Adaptation of the IEEE 802.11 protocol for inter-satellite links in LEO satellite networks

Knowledge of the coefficient of thermal expansion (CTE) of a ceramic material is important in many application areas. Whilst the CTE can be measured, it would be useful to be able to predict the expansion behaviour of multiphase materials.. There are several models for the CTE, however, most require a knowledge of the elastic properties of the constituent phases and do not take account ofthe microstructural features of the material. If the CTE could be predicted on the basis of microstructural information, this would then lead to the ability to engineer the microstructure of multiphase ceramic materials to produce acceptable thermal expansion behaviour. To investigate this possibility, magnesia-magnesium aluminate sp~el (MMAS) composites, consisting of a magnesia matrix and magnesium aluminate s~ne'l (MAS) particles, were studied. Having determined a procedure to produce MAS fr alumina and magnesia, via solid state sintering, magnesia-rich compositions wit ~ various magnesia contents were prepared to make the MMAS composites. Further, the l\.1MAS composites prepared from different powders (i.e. from an alumina-magnesia mixture ahd from a magnesia-spinel powder) were compared. Com starch was added into the powder mixtures before sintering to make porous microstructures. Microstructural development and thermal expansion behaviour ofthe MMAS composites were investigated. Microstructures of the MAS and the MMAS composites as well as their porous bodies were quaritified from backscattered electron micrographs in terms of the connectivity of solids i.e. solid contiguity by means of linear intercept counting. Solid contiguity decreased with increasing pore content and varied with pore size, pore shape and pore distribution whereas the phase contiguity depended strongly on the chemical composition and was less influenced by porosity. ' The thermal expansion behaviour of the MAS and the MMAS composites between 100 and 1000 °C was determined experimentally. Variation in the CTE ofthe MAS relates to the degree of spinel formation while the thermal expansion of the MMAS composites depends strongly on phase content. However, the MMAS composites with similar phase compositions but made from different manufacturing processes showed differences in microstructural features and thermal expansion behaviour. Predictions of the CTE values for composites based on a simple rule-of-mixtures (ROM) using volume fraction were compared with the measured data. A conventional ROM accurately predicted the effective CTE of a range of dense alumina-silicon carbide particulate composites but was not very accurate for porous multiphase structures. It provided an upper bound prediction as all experimental values were lower. Hence, the conventional ROM was modified to take account of quantitative microstructural parameters obtained from solid contiguity. The modified ROM predicted lower values and gave a good agreement with the experimental data. Thus, it has been shown that quantitative microstructural information can be used to predict the CTE of multiphase ceramic materials with complex microstructures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo