We propose a novel call admission control which makes use of ratio-based traffic measurement to estimate the required bandwidth when a new call is issued. Existing approaches fail to estimate properly the required bandwidth. To alleviate the problem, we calculate the ratio between the measured mean rate and the mean rate declared by UPC parameters. The ratio and the target cell loss rate are used to estimate the required bandwidth to make decision if a new call is accepted or rejected. Because of more accurate estimation of required bandwidth, our method can provide a better control on quality of service.

It is known that to pursuit end-to-end QoS of a class-based traffic flow is inefficient in Differentiated Service Networks. Therefore in this thesis, we propose an effective throughput-recovery mechanism to allow high-priority traffic flow to receive suitable resource allocation, and hence the end-to-end QoS is guaranteed. The proposed throughput-recovery mechanism assures a predefined minimum departure rate of low-latency EF dataflow. It consists of two parts. The first part is referred to as the feedback self-adaptive mechanism, where the egress node measures and monitors throughput of EF dataflow to decide whether to send the control messages to ingress node. When ingress node receives the control messages, it will reallocate the resources to improve EF throughput. The second part is referred to as the dynamic weight adjustment mechanism, which can prevent EF packets from dropping when congestion occurs in the core routers. For the purpose of demonstration, we build a mathematical model and use NS-2 simulator. We have proved our throughput-recovery mechanism is effective in improving the throughput of EF traffic flow. Finally, we modify the traditional WRR such that it can adjust weight based on the delay requirements.

Quality of Service (QoS) is the ability to guarantee that data sent across a network will be recieved by the desination within some constraints. For many advanced applications, such as real-time multimedia QoS is determined by four parameters--end-to-end delay, delay jitter, available bandwidth or throughput, and packet drop or loss rate. It is interesting to study and be able to predict the behavior of end-to-end packet delays in a Wide area network (WAN) because it directly a??ects the QoS of real-time distributed applications. In the current work a time-series representation of end-to-end packet delay dynamics transported over standard IP networks has been considered. As it is of interest to model the open loop delay dynamics of an IP WAN, the UDP is used for transport purposes. This research aims at developing models for single-step-ahead and multi-step-ahead prediction of moving average, one-way end-to-end delays in standard IP WAN??s. The data used in this research has been obtained from simulations performed using the widely used simulator ns-2. Simulation conditions have been tuned to enable some matching of the end-to-end delay profiles with real traffic data. This has been accomplished through the use of delay autocorrelation profiles. The linear system identification models Auto-Regressive eXogenous (AR) and Auto-Regressive Moving Average with eXtra / eXternal (ARMA) and non-linear models like the Feedforwad Multi-layer Perceptron (FMLP) have been found to perform accurate single-step-ahead predictions under varying conditions of cross-traffic flow and source send rates. However as expected, as the multi-step-ahead prediction horizon is increased, the models do not perform as accurately as the single-step-ahead prediction models. Acceptable multi-step-ahead predictions for up to 500 msec horizon have been obtained.

Motivated by the demand of increasing data rate in wireless communication, multiple-antenna communication is becoming a key technology in the next generation wireless system. This dissertation considers three different aspects of multipleantenna communication. The first part is signal detection in the multiple-input multiple-output (MIMO) communication. Some low complexity near optimal detectors are designed based on an improved version of Bell Laboratories Layered Space-Time (BLAST) architecture detection and an iterative space alternating generalized expectation-maximization (SAGE) algorithm. The proposed algorithms can almost achieve the performance of optimal maximum likelihood detection. Signal detections without channel knowledge (noncoherent) and with co-channel interference are also investigated. Novel solutions are proposed with near optimal performance. Secondly, the error exponent of the distributed multiple-antenna communication (relay) in the windband regime is computed. Optimal power allocation between the source and relay node, and geometrical relay node placement are investigated based on the error exponent analysis. Lastly, the quality of service (QoS) of MIMO/single-input single- output(SISO) communication is studied. The tradeoff of the end-to-end distortion and transmission buffer delay is derived. Also, the SNR exponent of the distortion is computed for MIMO communication, which can provide some insights of the interplay among time diversity, space diversity and the spatial multiplex gain.

WiMAX (Worldwide Interoperability for Microwave Access) provides wide transmission range and broadband network services. However, in IEEE 802.16 standard, there is no specific definition for SS (Subscriber Station) to select an optimal route in a mesh-based WiMAX network. In this thesis, we propose an Optimal Route Selection Scheme (ORSS) for SS to select a route to its BS (Base Station). ORSS basically considers three influential factors, the bandwidth SS to be assigned, the number of interference nodes around SS, and the hop counts to BS. We also investigate QoS (Quality of Service) issue in a mesh-based WiMAX network; an SS transferring the rtPS traffic type will share bandwidth with the neighboring SS of the same level that transmit the same traffic type. To ensure the selected route that can meet the bandwidth requirements of rtPS and the delay constraints, we estimate the average transmission delay from SS to BS. For the purpose of evaluation, we establish a mathematical model to analyze the proposed ORSS and discuss the impact of varying network parameters on the successful rate of route selection. Through the Matlab simulation, we validate our mathematical model. The simulation results demonstrate that our ORSS, in comparison to a previous work, is more effective in ensuring the delay constraints when selecting a route to transfer rtPS traffic.

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Diese Diplomarbeit beschäftigt sich mit der "schleichenden Abschaltung" begrenzter Netzzugänge bei Überschreitung eines vorgegebenen Datenvolumens und der Anwendung dieser Technologie im Chemnitzer Studentennetz. Nutzer, die bestimmte Transfervolumina überschreiten, werden schrittweise einer immer schlechter bewerteten Verkehrsklasse zugeordnet, wo ihnen weniger Bandbreite zur Verfügung steht. Dazu werden die Möglichkeiten, die der Linux-Kern hinsichtlich Quality of Service bietet, genutzt.

This thesis presents the research carried out to investigate and achieve highly reliable and accurate navigation system of guidance for visually impaired pedestrians. The main aim with this PhD project has been to identify the limits and insufficiencies in utilising Network Real-Time Kinematic Global Navigation Satellite Systems (NRTK GNSS) and its augmentation techniques within the frame of pedestrian applications in a variety of environments and circumstances. Moreover, the system can be used in many other applications, including unmanned vehicles, military applications, police, etc. NRTK GNSS positioning is considered to be a superior solution in comparison to the conventional standalone Global Positioning System (GPS) technique whose accuracy is highly affected by the distance dependent errors such as satellite orbital and atmospheric biases. Nevertheless, NRTK GNSS positioning is particularly constrained by wireless data link coverage, delays of correction and transmission and completeness, GPS and GLONASS signal availability, etc., which could downgrade the positioning quality of the NRTK results. This research is based on the dual frequency NRTK GNSS (GPS and GLONASS). Additionally, it is incorporated into several positioning and communication methods responsible for data correction while providing the position solutions, in which all identified contextual factors and application requirements are accounted. The positioning model operates through client-server based architecture consisted of a Navigation Service Centre (NSC) and a Mobile Navigation Unit (MNU). Hybrid functional approaches were consisting of several processing procedures allowing the positioning model to operate in position determination modes. NRTK GNSS and augmentation service is used if enough navigation information was available at the MNU using its local positioning device (GPS/GLONASS receiver).The positioning model at MNU was experimentally evaluated and centimetric accuracy was generally attained during both static and kinematic tests in various environments (urban, suburban and rural). This high accuracy was merely affected by some level of unavailability mainly caused by GPS and GLONASS signal blockage. Additionally, the influence of the number of satellites in view, dilution of precision (DOP) and age corrections (AoC) over the accuracy and stability of the NRTK GNSS solution was also investigated during this research and presented in the thesis. This positioning performance has outperformed the existing GPS service. In addition, utilising a simulation evaluation facility the positioning model at MNU performance was quantified with reference to a hybrid positioning service that will be offered by future Galileo Open Service (OS) along with GPS. However, a significant difference in terms of the service availability for the advantage of the hybrid system was experienced in all remaining scenarios and environments more especially the urban areas due to surrounding obstacles and conditions. As an outcome of this research a new and precise positioning model was proposed. The adaptive framework is understood as approaching an integration of the available positioning technology into the context of surrounding wireless communication for a maintainable performance. The positioning model has the capability of delivering indeed accurate, precise and consistent position solutions, and thus is fulfilling the requirements of visually impaired people navigation application, as identified in the adaptive framework.

ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / Network loads close to Ethernet wire speed and latency sensitive data in a Flight Test Instrumentation (FTI) system, represent challenging requirements for FTI network equipment. Loss of data due to network congestion, overflow on the end nodes, as well as packet latency above a few hundred microseconds, can be critical during a flight test. To avoid these problems, several advanced packet filtering and network optimization functions are required in order to achieve best possible performance and thus avoid loss of data. This paper gives insight into how to properly engineer an Ethernet based FTI network and how to use advanced Ethernet switch techniques such as Quality of Service (QoS) and rate shaping.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / Spectrum efficiency is the key challenge in modern telemetry systems. Network telemetry requires moving from a dedicated link structure to a network structure which is a very complex problem and requires spectrum management tools. A mixed network structure has been previously proposed for networked telemetry which employs a combination of cellular and Adhoc networks. Significant improvements in QoS and clustering of the complex aeronautical networks have been observed and published in several venues. However in the earlier work routing within the Ad-hoc clusters has not been addressed and the clustering has been done using an enhanced K-means clustering. In this paper, a well known clustering algorithm is adopted in the mixed network concept and clustering of the Ad-hoc nodes are optimized based on shortest route to the gateway and minimum hop count criteria. The proposed clustering technique in this paper leads to a jointly optimized cluster-topology and gateway-selection solution a complex aeronautical network. Simulation results towards the end of this paper illustrate that with the proposed method, cluster configuration is locally optimized and the best gateway for each cluster is successfully selected. With addition of traffic measures to the consideration in the routing, the proposed solution will leads to efficient spectrum allocation and improved QoS.