Optimization of IEEE 802.11e MAC protocol performance is done by modifying several parameters left open in the standard, like buffer size and acknowledgement policies. By using the developed event-driven simulator, results were extracted with single and multi-service. With only a single service, higher values for the goodput are obtained for video and background (BK) traffics in comparison with the voice (VO) application. Besides, the number of supported user is higher for voice. With mixtures of traffic, when the number of station is small the goodput is lower for VO. However, for higher number of station, the lowest values for the goodput occur for background traffic. By using the Block Acknowledgement (ACK) procedure, for video and BK traffics, the capacity is improved when the number of station is equal or higher than 16 and 12, respectively. From a detailed analysis of the video application, a reduction of more than 40% was achieved in the delay. However, a clear trend is not identified for the optimum block size.

This work provides the specification of a MAC layer simulator that evaluates the service quality in WiFi, and presents initial results as a stand-alone simulator. The simulator will account for inter-working with WiMAX and HSDPA in the context of the IT-MOTION tool. Higher throughputs are found for the FTP service and for the video service, mainly because the frames transmitted in these services are longer than the ones for the voice application. However, the number of supported users is higher for voice. This simulator will allow for tuning-up several parameters like the ones related to how to use BlockACK, normal ACK, and NO ACK policies.

A multi-service traffic model is briefly presented, and its validation is achieved by using event-based simulation results which consider the burstiness of traffic. A simulator was produced to extract conclusions about blocking and handover failure probabilities in a multi-service bursty traffic context. Simulations, were performed for different cases, from single- to multi-service situations, and from absence to presence of mobility. Besides quality of service results in the air interface, including blocking and handover failure probabilities, the simulator allows for extracting conclusions about the validation of the Bernoulli-Poisson-Pascal model for the computation of the on/off blocking probability, the ratio between the number of call rejected at the beginning of an on period and the total number of bursts generated during a session. In the single-service case, the theoretical and the experimental values of on/off blocking probability are close to each other, and there is an almost perfect concordance between theoretical and simulation values when the average sojourn time in cells is equal to the average holding time. In the multi-service case, the behaviour is not exactly the same but a coherent behaviour is achieved for an average traffic per user up to 0.10 Erl.

The main purpose of this paper is to study fuel cell performance using an interdigitated flow field with intermediate channel blocks on the cathode side. Application of an intermediate block in the middle of the interdigitated flow channel is a very new idea aimed at increasing the performance of polymer membrane fuel cells, which in practice result in novel arrangements of interdigitated flow channels. A middle block is desirable because the change in flow channel is minimal, the cost of fabricating bipolar plates does not increase, and it leads to an increase in the transfer rate of reactants into the gas diffusion layer due to enhanced over-rib flow pattern and direction. In this work, a three-dimensional, isothermal, and two-phase model is used to simulate the performance of such fuel cells. The polarization curves, the distribution of reactants on the cathode side, the distribution of liquid water, and the induced transverse flow were analyzed for three type of interdigitated flow fields along with parallel flow fields at reference conditions. The results showed that interdigitated flow fields with middle blocks lead to an increase in reactant transfer to the catalyst layer, an increase in reaction rate, and better removal of the resulting liquid water within the fuel cell. In the reference condition, in terms of maximum power density, the type I interdigitated flow field (without intermediate block) increased the net power by 8.2% compared to the parallel flow field, and the type II and III interdigitated flow fields also increased the power by 12.58% and 9.03%, respectively. At high current density, the type II interdigital flow field had the best performance in terms of enhancing the transfer of reactants to the catalyst layer and the expulsion of liquid water from that layer.

This paper provides a complete specification of the packet based cellular wireless system level simulator that addresses a beyond 3G scenario involving heterogeneous wireless systems interconnected via an IP backbone network. Important aspects as the Link layer design (including the MAC layer) are specified, as well as the C++ object oriented simulation architecture. Since the IP level and the physical layer aspects should be avoided, interfaces representing these layers are proposed for different type of radio access systems. The concept is showcased by a multi-RAT system composed of HSDPA and a Wi-Fi system using load balancing techniques.

Optimisation of IEEE 802.11e MAC protocol performance can be performed by modifying several parameters left open in the standard, like buffer size and acknowledgement policies. In this work, an event driven simulator was developed, and a comparison of the results between the case of standalone services and several services supported simultaneously was addressed. With only a single service, higher values for the goodput are obtained for video and background (BK) traffics, while the lowest ones are found for the voice application. Besides, the number of supported users is higher for voice. With mixtures of traffic, when the number of station is small the goodput is lower for voice. However, for higher number of station, the lowest values of the goodput occur for background traffic. By using the Block Acknowledgement procedure, for video and background traffics in a single service situation, the capacity was improved in the case when the number of stations is equal or higher than 16 and 12, respectively. However, for lower values of the number of stations, the use of Block Acknowledgements leads to a slightly worst system performance. In a scenario with mixture of services the most advised block size is 12 (less delay in a highly loaded scenario). The total number of supported user increases from 30 to 35.

This paper presents a new algorithm for finding the parameters that characterize a photovoltaic panel by using the Glowworm Swarm Optimization algorithm. This new algorithm shows great simplicity, flexibility and precision, being able to precisely locate the global optimum point or multiple global optimum points, independently of the initial conditions. The approach here adopted allows the utilization of the algorithm in several existing models to characterize a photovoltaic panel in the current literature.

Autonomous Guided Vehicles (AGV) are currently being used in industry to move materials efficiently. Simulators may be used to help calculate the right number of AGVs needed for a particular task and also which types better suit the necessity of a company. This paper analyzes the characteristics of many of the most used simulators and focus on evaluating an environment using Stage and Robot Operating System (ROS), to find experimentally if one AGV may complete a specific task taking into account eventual path blockages by random events.

A multi-service traffic model is proposed, and its validation is achieved by using event-based simulation results. In the single-service case, theoretical and experimental results for ON-OFF blocking probability are close to each other, and there is an almost perfect concordance between theoretical and simulation values when the average sojourn time in cells is equal to the average holding time. In the multi-service case, the behaviour is not exactly the same but a coherent behaviour is achieved for an average traffic per user up to 0.10 Erl.

A multi-service traffic model is presented, and its validation is achieved in a vehicular scenario by using event-based simulation results. In the single-service case, theoretical and experimental results for ON-OFF blocking probability are close to each other, and there is an almost perfect concordance between theoretical and simulation values when the average sojourn time in cells is equal to the average holding time. The challenges presented by the multi-service case are identified, and a question related with a possible correspondence between blocking/handover failure probabilities and ON-OFF blocking probability are presented.