A time dependent performance model for multihop wireless networks with CBR traffic

In this paper, we develop a performance modeling technique for analyzing the time varying network layer queueing behavior of multihop wireless networks with constant bit rate traffic. Our approach is a hybrid of fluid flow queueing modeling and a time varying connectivity matrix. Network queues are modeled using fluid-flow based differential equation models which are solved using numerical methods, while node mobility is modeled using deterministic or stochastic modeling of adjacency matrix elements. Numerical and simulation experiments show that the new approach can provide reasonably accurate results with significant improvements in the computation time compared to standard simulation tools. © 2010 IEEE

The impact of wakeup schedule distribution in synchronous power save protocols on the performance of multihop wireless networks

By definition, the operation of an asynchronous power save protocol permits an arbitrary distribution of nodes' wakeup schedules. This wakeup schedule distribution creates an uncoordinated pattern of times at which nodes will attempt to transmit. Intuitively, we would expect that some patterns will be more (or less) favorable than others for a given traffic pattern. We investigate the impact of this wakeup pattern on network capacity and present simulation data showing that the capacity associated with the best wakeup patterns is significantly larger than that of the worst. This result not only gives insight to the behavior of such protocols, but also acts as a feasibility study showing the potential benefit of mechanisms by which nodes adapt their wakeup schedules to obtain improved performance

An efficient hybrid model and dynamic performance analysis for multihop wireless networks

Multihop wireless networks can be subjected to nonstationary phenomena due to a dynamic network topology and time varying traffic. However, the simulation techniques used to study multihop wireless networks focus on the steady-state performance even though transient or nonstationary periods will often occur. Moreover, the majority of the simulators suffer from poor scalability. In this paper, we develop an efficient performance modeling technique for analyzing the time varying queueing behavior of multihop wireless networks. The one-hop packet transmission (service) time is assumed to be deterministic, which could be achieved by contention-free transmission, or approximated in sparse or lightly loaded multihop wireless networks. Our model is a hybrid of time varying adjacency matrix and fluid flow based differential equations, which represent dynamic topology changes and nonstationary network queues, respectively. Numerical experiments show that the hybrid fluid based model can provide reasonably accurate results much more efficiently than standard simulators. Also an example application of the modeling technique is given showing the nonstationary network performance as a function of node mobility, traffic load and wireless link quality. © 2013 IEEE

Service differentiation in multihop wireless packet networks

This work explores the potential of link layer scheduling combined with MAC layer prioritization for providing service differentiation in multihop wireless packet networks. As a result of limited power, multihop characteristic and mobility, packet loss ratio in wireless ad hoc networks tends to be high compared to wireline and one-hop mobile data networks. Therefore, for wireless ad hoc networks, DiffServ-like distributed service differentiation schemes are more viable than hard QoS solutions, which are mainly designed for wireline networks. The choice and implementation of proper queuing and scheduling methods, which determine how packets will use the channel when bandwidth becomes available, contributes significantly to this differentiation. Due to the broadcast nature of wireless communication, media access is one of the main resources that needs to be shared among different flows. Thus, one can design and implement algorithms also at MAC level for service differentiation. In this study, in addition to the scheduling discipline, IEEE 802.11 Distributed Coordination Function is used to increase the media access probability of a specific class of traffic. It is shown that the service requirements of a class can be better met using this two level approach compared to the cases where either of these schemes used alone

Time-varying performance analysis of multihop wireless networks with CBR traffic

In this paper, we develop a performance modeling technique for analyzing the time-varying network layer queuing behavior of multihop wireless networks with constant bit rate (CBR) traffic. Our approach is a hybrid of a time-varying adjacency matrix and a fluid flow queuing network model. The mobile network topology is modeled using a time-varying adjacency matrix, whereas node queues are modeled using fluid-flow-based differential equations that are solved using numerical methods. Numerical and simulation experiments show that this new approach can provide reasonably accurate results. Moreover, when compared with the computation time required in a standard discrete event simulator, the fluid-flow-based model is shown to be a more scalable tool. Finally, an illustrative example of our modeling technique application is given to show its capability of capturing the time-varying network performance as a function of traffic load, node mobility, and wireless link quality

Performance and energy efficiency in wireless self-organized networks

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BOB-RED queue management for IEEE 802.15.4 wireless sensor networks

This study is aimed at exploring why many economists propose a transfer scheme and debt mutualisation for the Eurozone. This would equip the Eurozone with better tools to deal with an economic shock, like the 2010-2012 sovereign debt crisis, thus making it more financially stable. After the theoretical presentation, the study presents a unique institutional design with an EU Treasury that manages debt mutualisation and a transfer scheme as well as other competences that address other present economic challenges. Crucial to the study are the issues of moral hazard and adverse selection that arise when thinking of European economic integration.L’objectiu del treball és explorar la raó per la qual molts economistes proposen un sistema de transferències fiscals i la mutualització del deute a l’Eurozona. Així se la dotaria amb eines més efectives per pal·liar un xoc econòmic, com la crisi del deute sobirà del 2010-2012. A continuació, es presenta un disseny institucional únic d’un Tresor de l’Euro que gestionaria les competències esmentades (i d’altres) per combatre alguns dels reptes econòmics actuals. El risc moral i de selecció adversa, qüestions que sorgeixen en pensar la drecera que ha de prendre la integració econòmica Europea, són cabdals per aquest estudi