Nobody’s perfect: interactive synthesis from parametrized real-time scenarios

ABSTRACT As technical systems keep growing more complex and sophisticated, designing software for the safety-critical coordination between their components becomes increasingly difficult. Verifying and correcting these components already represents a significant part of the development process both with respect to time and cost. Scenario-based synthesis has been put forward as an approach to accelerate the transition from requirements to a correct, verified model. I

Department of Computer Science Activity 1998-2004

This report summarizes much of the research and teaching activity of the Department of Computer Science at Dartmouth College between late 1998 and late 2004. The material for this report was collected as part of the final report for NSF Institutional Infrastructure award EIA-9802068, which funded equipment and technical staff during that six-year period. This equipment and staff supported essentially all of the department\u27s research activity during that period

Modelling and Analysis of Resource Management Schemes in Wireless Networks. Analytical Models and Performance Evaluation of Handoff Schemes and Resource Re-Allocation in Homogeneous and Heterogeneous Wireless Cellular Networks.

Over recent years, wireless communication systems have been experiencing a dramatic and continuous growth in the number of subscribers, thus placing extra demands on system capacity. At the same time, keeping Quality of Service (QoS) at an acceptable level is a critical concern and a challenge to the wireless network designer. In this sense, performance analysis must be the first step in designing or improving a network. Thus, powerful mathematical tools for analysing most of the performance metrics in the network are required. A good modelling and analysis of the wireless cellular networks will lead to a high level of QoS. In this thesis, different analytical models of various handoff schemes and resource re-allocation in homogeneous and heterogeneous wireless cellular networks are developed and investigated. The sustained increase in users and the request for advanced services are some of the key motivations for considering the designing of Hierarchical Cellular Networks (HCN). In this type of system, calls can be blocked in a microcell flow over to an overlay macrocell. Microcells in the HCN can be replaced by WLANs as this can provide high bandwidth and its users have limited mobility features. Efficient sharing of resources between wireless cellular networks and WLANs will improve the capacity as well as QoS metrics. This thesis first presents an analytical model for priority handoff mechanisms, where new calls and handoff calls are captured by two different traffic arrival processes, respectively. Using this analytical model, the optimised number of channels assigned to II handover calls, with the aim of minimising the drop probability under given network scenarios, has been investigated. Also, an analytical model of a network containing two cells has been developed to measure the different performance parameters for each of the cells in the network, as well as altogether as one network system. Secondly, a new solution is proposed to manage the bandwidth and re-allocate it in a proper way to maintain the QoS for all types of calls. Thirdly, performance models for microcells and macrocells in hierarchical cellular networks have been developed by using a combination of different handoff schemes. Finally, the microcell in HCN is replaced by WLANs and a prioritised vertical handoff scheme in an integrated UMTS/WLAN network has been developed. Simulation experiments have been conducted to validate the accuracy of these analytical models. The models have then been used to investigate the performance of the networks under different scenarios

Modeling and acceleration of content delivery in world wide web

Ph.DDOCTOR OF PHILOSOPH

Improving resource management in multi-protocol label switched traffic engineered networks

Over the years, the Internet has emerged as an indispensable platform for information exchange. As availability increases, development of new applications generate enormous volumes of tra c. Such growth continually taxes service provider resources. A common and e ective resource management option deployed by several service providers is Multi-Protocol Label Switched (MPLS) based Tra c Engineering (TE).This dissertation proposes new MPLS based TE mechanisms capable of dealing with tra c changes, such as growth and shifts. Speci cally, new techniques for dynamic bandwidth allocation and routing are proposed and developed through simulations under failure and non-failure scenarios. Issues related to inter-domain deployment are also studied and nally, an experimental testbed setup is proposed and implemented for realistic small scale testing.A new tra c engineering technique involving the coupling of dynamic bandwidth allocation with rerouting to nd the best path for the current tra c is proposed. Realistic topologies and tra c pro les are used for detailed analysis and comparisons with existing techniques. Performance analysis is also undertaken in an International network scenario carrying a mix of voice and data tra c across several timezones. Several key issues are highlighted after studying underlying network dynamics such as signaling overhead, router load, tra c path quality, etc. Keeping these issues in mind, a new trend-based bandwidth reservation mechanism is proposed. The problem of inter-domain TE is analyzed next. Existing inter-domain path computation approaches, signaling and path setup issues are studied, quanti ed and compared. Lastly, the functional prototype of a testbed architecture consisting of Cisco routers and Linux boxes is presented. A new Java based API that has been developed to con gure the testbed and deploy new mechanisms is also discussed.Ph.D., Computer Engineering -- Drexel University, 200

Proceedings of the Conference on Production Systems and Logistics: CPSL 2022

[no abstract available