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The hierarchical real-time scheduling framework is a widely accepted model to facilitate the design and analysis of the increasingly complex real-time systems. Interface abstraction and composition are the key issues in the hierarchical scheduling framework analysis. Schedulability is essential to guarantee that the timing requirements of all components are satisfied. In order for the design to be...
Traveling-wave tubes (TWTs), used in civil and defence applications, require high power and multi-octave bandwidth rather than high efficiency and hence just a single stage depressed collector is sufficient. However, TWT used in space applications necessarily has to have very high efficiency rather than wide bandwidth. A user friendly multi-stage depressed (MDC) collector design code in MATLAB for...
The large-signal code TESLA (Telegraphist's Equations Solution for Linear-beam Amplifiers) was originally developed for the analysis and design of klystrons. It has now been applied to the simulations of an extended interaction klystron (EIK) for the first time. Results for the power transfer curve and bandwidth curves computed for a G-band EIK compare well to their measured values. TESLA obtains...
In the provisioning of Broadband Television (BTV) services, user call blocking probability (CBP) denotes the ratio of failed user requests, which is one of the most important metrics on BTV quality of experience (QoE). This paper aims to evaluate and further to decrease the CBP of BTV services in networks with tree topology. At first, we analyze a currently typical BTV delivery network architecture,...
Peer to Peer (P2P) live streaming is relatively new paradigm that aims for streaming live video to large number of clients with low cost. Many such applications allready exist in the market, but, prior to creating such system it is necessary to analyze its performance via representative model that can provide good insight in system's behavior. Modeling and performance analysis of P2P live video streaming...
Mode conversion can be achieved in multimode waveguides using optical analogy of stimulated Raman adiabatic passage. The coupled mode equations (CMEs) for adiabatic mode conversion via an intermediate mode with wavelength detunings are derived for an engineered step-index multimode waveguide. It is shown that the detunings cause diabatic coupling of adiabatic modes and result in lowered conversion...
A myriad of Vertical Handoff Algorithms (VHA) have been proposed by researchers and networks practitioners. These algorithms allow mobile terminals (MT) to maintain the network connection when they switch from one wireless network to another one. Given the amount of proposed VHA and the need for an objective assessment of these solutions different evaluation methodologies have been proposed, becoming...
Network virtualization has been propounded as a key diversifying attribute of the future inter-networking paradigm. Although exciting progresses have been made in this area, understanding the performance of end-to-end service delivery in network virtualization is still a significant opening topic that requires analytical modeling and analysis. Heterogeneity of the network infrastructures coexisting...
This paper presents a Matlab model for the signal path within a DVB-T receiver, along with a new method for analyzing the effects various block nonidealities have on the receiver, when considering unwanted signals such as the adjacent channels and out-of-band blockers. The models for amplifier-type blocks cover not only the basic parameters - gain, bandwidth - but also the noise - though the noise...
The paper presents a new analytical model for performance evaluation of multi-service communication systems. The paper considers for the first time multi-service systems in which each single traffic source can generate calls of different traffic classes, i.e. the multi-service systems with multi-service sources. To date only the models assuming that a single source of given class generates always...
This paper presents an analytical model for evaluating the performance of streaming and elastic traffic integration in a multiservice network with dynamic channel allocation scheme (DCAS). Different classes of traffic have different quality of service (QoS) requirements. Therefore at the model analysis it is important to consider this feature. Formulae for performance characteristics e.g. blocking...
The current trend of network convergence has been best exemplified by the recent emergence of new services such as Broadband TV (BTV) offered by Telcos around the world. A very relevant research topic is to improve the quality of experience (QoE). This paper focuses on decreasing the user call blocking probability (CBP), which is one of the most important BTV QoE metrics. At first, we analyze a currently...
This paper presents analytical models to dimension the transport bandwidths for the S1 interface in the Long Term Evolution (LTE) Network. In this paper, we consider two major traffic types: elastic traffic and real time traffic. For each type of traffic, individual dimensioning models are proposed. For validating these analytical dimensioning models, a developed LTE system simulation model is used...
In less than two decades, computer viruses and worms have grown from an anomaly to an everyday occurrence. In response to such a threat, the academic community has started a set of research projects seeking to understand worm behavior through creation of models. Staniford created a model to explain the propagation behaviors of worms in computer network environments. Liljenstam added a spatial perspective...
A new generation of high-performance engines now combine graphics-oriented parallel processors with a cache architecture. In order to meet this new trend, new highly-parallel workloads are being developed. However, it is often difficult to predict how a given application would perform on a given architecture. This paper provides a new model capturing the behavior of such parallel workloads on different...
This paper proposes the framework to find the optimal selection of heterogeneous wireless network. Reinforcement learning (RL) model is used to find the best strategy to maximise the reward function expressed in terms of call blocking and call dropping probabilities. The reward-evaluation model is based on the well-established macroscopic cell transmission model (CTM), which has the advantage in computational...
The IEEE 802.16 is a well known set of standards, which have been developed for global deployment of Metropolitan Area Networks (MANs) in order to provide broadband wireless accesses supporting the integrated transmission of multimedia applications with different Quality of Service (QoS) requirements. In order to achieve the QoS requirements of multimedia applications, the IEEE 802.16 standards offers...
The worm experimental environment is the pivotal foundation for the worm research. Existing methods to build the environment can be classified into three categories: mathematical modeling, simulation and emulation. However, almost all of the existing methods inherently face a rigid fidelity-scalability tradeoff problem. Aming at this issue, this paper proposes a novel virtual-reality hybrid worm emulation...
A challenging issue in performance evaluation of parallel storage systems through trace-driven simulation is to accurately characterize and emulate I/O behaviors in real applications. The correlation study of inter-arrival times between I/O requests, with an emphasis on I/O-intensive scientific applications, shows the necessity to further study the self-similarity of parallel I/O arrivals. This paper...
Peer-to-Peer (P2P) networks are distributed systems where no central authority rules the behavior of the individual peers. A typical application is the sharing of files of some class (movies, music, ...), our object of interest here. These systems relay on the voluntary participation of the peers to help each other. However, it is not uncommon to find users that have initiated a file transfer and...
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