Medium Access Control for Wireless Sensor Networks based on Impulse Radio Ultra Wideband

This paper describes a detailed performance evaluation of distributed Medium Access Control (MAC) protocols for Wireless Sensor Networks based on Impulse Radio Ultra Wideband (IR-UWB) Physical layer (PHY). Two main classes of Medium Access Control protocol have been considered: Slotted and UnSlotted with reliability. The reliability is based on Automatic Repeat ReQuest (ARQ). The performance evaluation is performed using a complete Wireless Sensor Networks (WSN) simulator built on the Global Mobile Information System Simulator (GloMoSim). The optimal operating parameters are first discussed for IR-UWB in terms of slot size, retransmission delay and the number of retransmission, then a comparison between IR-UWB and other transmission techniques in terms of reliability latency and power efficiency

ASPECTS CONCERNING FINANCIAL PROFITABLENESS ANALYSIS AND ITS PURPOSE IN SUBSTANTIATION OF FIRM’S STRATEGIC FINANCING DECISIONS

Financial profitableness, relevant indicator in enterprises performance appreciation and of its position on the market, depends on the commercial policy (commercial profitableness), on the engaged capital’s efficiency (economic profitableness), on the policy and financial structure of enterprise (debt degree) offering information both to investors and managers, orienting the enterprise in financing strategic decisions

CLASSICAL CALCULATION METHODS OF COSTS AND THEIR LIMITS IN ACTUAL FRAME OF ROMANIAN ECONOMY. PRESENT TENDENCIES IN COSTS ACCOUNTANCY

Classical accountancy shaped and coagulated in an informational system grafted on traditional production systems, characterized by mass productions, planning etc. The powerful concentrations and grouping, economies globalization, both as offer and as demand, the new restrictions and economical opportunities and global environment technologies lead to a redefining of enterprises’ objectives. From the well-known “quantity and productivity”, the enterprise faced a new system of objectives: quality’s increase; terms and costs decrease; productivity; flexibility. In such conditions the need of “defining new methods” appeared, the need of adapting the fundamental calculation methods, their improvement – respective the appearance of modern methods of costs calculation

Simulation Platform for Wireless Sensor Networks Based on Impulse Radio Ultra Wide Band

Impulse Radio Ultra Wide Band (IR-UWB) is a promising technology to address Wireless Sensor Network (WSN) constraints. However, existing network simulation tools do not provide a complete WSN simulation architecture, with the IR-UWB specificities at the PHYsical (PHY) and the Medium Access Control (MAC) layers. In this paper, we propose a WSN simulation architecture based on the IR-UWB technique. At the PHY layer, we take into account the pulse collision by dealing with the pulse propagation delay. We also modelled MAC protocols specific to IRUWB, for WSN applications. To completely fit the WSN simulation requirements, we propose a generic and reusable sensor and sensing channel model. Most of the WSN application performances can be evaluated thanks to the proposed simulation architecture. The proposed models are implemented on a scalable and well known network simulator: Global Mobile Information System Simulator (GloMoSim). However, they can be reused for all other packet based simulation platforms

UVA Method – innovative approach in economic and strategic management of an enterprise

UVA method has developed starting from the principle “measuring the entire activity of an enterprise with a single unit measure”, announced by Georges Perrin at the beginning of the ‘50’s. The followed aim is that the method would be simple and, respectively, would avoid the global costs treating. As consequence, a minute analysis is needed for every unit of the process. Also, a fundamental principle is imposed: the costs of these activities will generally remain established in relative values at least for the period when major changes in technology do not occur

Channel Capacity Limitations versus Hardware Implementation for UWB Impulse Radio Communications

Starting from the Shannon channel capacity, we propose an IR-UWB channel capacity based on the delay spread for multipath time variant channels. This IR-UWB channel capacity is obtained from the no ISI (Inter Symbol Interference) assumption and for binary modulations. The impact of the kind of implementation is considered on the IR-UWB channel capacity. This study is lead for mixed and mostly digital implementation. The key parameters and theirs impacts on the channel capacity are exposed in each case: the data converters for mostly digital implementations and the pulse generator capabilities for mixed implementations. Finally, these two implementations are compared from a data rate point of view. Their behaviors regarding an increase of the operating frequency are also studied