Extending the Energy Framework for Network Simulator 3 (ns-3)

The problem of designing and simulating optimal transmission protocols for energy harvesting wireless networks has recently received considerable attention, thus requiring for an accurate modeling of the energy harvesting process and a consequent redesign of the simulation framework to include it. While the current ns-3 energy framework allows the definition of new energy sources that incorporate the contribution of an energy harvester, the integration of an energy harvester component into an existing energy source is not straightforward using the existing energy framework. In this poster, we propose an extension of the energy framework currently released with ns-3 in order to explicitly introduce the concept of an energy harvester. Starting from the definition of the general interface, we then provide the implementation of two simple models for the energy harvester. In addition, we extend the set of implementations of the current energy framework to include a model for a supercapacitor energy source and a device energy model for the energy consumption of a sensor. Finally, we introduce the concept of an energy predictor, that gathers information from the energy source and harvester and use this information to predict the amount of energy that will be available in the future, and we provide an example implementation. As a result of these efforts, we believe that our contributions to the ns-3 energy framework will provide a useful tool to enhance the quality of simulations of energy-aware wireless networks.Comment: 2 pages, 4 figures. Poster presented at WNS3 2014, Atlanta, G

The impact of the access point power model on the energy-efficient management of infrastructured wireless LANs

The reduction of the energy footprint of large and mid-sized IEEE 802.11 access networks is gaining momentum. When operating at the network management level, the availability of an accurate power model of the APs becomes of paramount importance, because different detail levels have a non-negligible impact on the performance of the optimisation algorithms. The literature is plentiful of AP power models, and choosing the right one is not an easy task. In this paper we report the outcome of a thorough study on the impact that various inflections of the AP power model have when minimising the energy consumption of the infrastructure side of an enterprise wireless LAN. Our study, performed on several network scenarios and for various device energy profiles, reveals that simple one- and two-component models can provide excellent results in practically all cases. Conversely, employing accurate and detailed power models rarely offers substantial advantages in terms of power reduction, but, on the other hand, makes the solving algorithms much slower to execute

Buffering Technique for Optimizing Energy Consumption in the Transmission of MultimediaTraffic in Ad-Hoc Networks

Energy constraints on wireless nodes represent a current field of research. Such restrictions are particularly significant because of the great amount of features and applications currently available on devices, which contribute to dramatically increase energy consumption. However, when transmitting delay-sensitive data, such as multimedia streaming, a balance between energy optimization and quality of service is required. In this sense, there are many works that address this issue from different layers of network architecture separately; however, a more efficient solution could be achieved by combining the management capabilities of the different layers and the joint use of such information, which is called a crosslayer mechanism. Moreover, despite the fact that the IEEE 802.11 standard defines an energy management mechanism at MAC level, it is envisaged only for structured networks, leaving just general guidelines for other kind of networks, such as Ad- Hoc networks. Therefore, as a first step towards the design of a cross-layer scheme, this paper analyzes the flaws of IEEE 802.11 standard as regards the infrastructureless mode and proposes an optimization mechanism for energy management in Ad-Hoc networks. The proposed approach is based on a buffering mechanism, which is able to increase power-saving periods of time in Ad-Hoc nodes. Simulations using NS3 indicate that it is possible to obtain higher levels of residual energy at the end of a transmission using the proposed scheme.Gonzalez, S.; Arce Vila, P.; Guerri Cebollada, JC. (2015). Buffering Technique for Optimizing Energy Consumption in the Transmission of MultimediaTraffic in Ad-Hoc Networks. IEEE Latin America Transactions. 13(1):250-258. doi:10.1109/TLA.2015.7040655S25025813

Contributions to satellite subsystem models and communications link emulation

During last years, space missions have evolved from monolithic spacecrafts architectures, to distributed ones, which are known as Distribute Satellite Systems (DSS). This spacecraft architecture has changed the space paradigm, as it has appeared the need of establishing communications between satellites to achieve the mission objectives. Despite this the need of simulating and emulating the communications between satellites, none of the available tools have complete inter-satellite communications capabilities. This final degree thesis presents contributions to the already existing simulator developed by NanoSat Lab. The contributions consist in the implementation of the Electric Power Supply (EPS) subsystem. Moreover, this thesis also contributes to the development of a Satellite Contact Emulator, developed by i2Cat, focusing on the development of the central PC that orchestrates the emulation.Recentment, les missions espacials han evolucionat d'una arquitectura basada en un sol satèl·lit, a una arquitectura distribuïda. Aquest tipus d'arquitectura és coneguda com a Distribute Satellite Systems" (DSS). L'aparició d'aquesta nova estructura ha provocat un canvi en el paradigma de l'espai, ja que ha sorgit la necessitat d'establir comunicació entre els satèl·lits per assolir els objectiu marcats de les missions. Tot i haver la necessitat d'emular i simular les comunicacions enter satèl·lits, cap de les eines actuals té suficients funcionalitats implementades per assolir aquesta emulació i simulació. Aquest treball de fi de grau presenta les contribucions fetes a un simulador ja existent, el qual ha estat desenvolupat pel NanoSat Lab de la UPC. La contribució feta consisteix en la implementació d'un subsistema que modeli una EPS. A més a més, aquest treball de fi de grau també contribueix en el desenvolupament d'un Satellite Contact Emulator, el qual ha estat desenvolupat per i2Cat. En aquesta contribució es farà menció especial en l'ordinador central que executa l'emulació.Recientemente, las misiones espaciales han evolucionado de una arquitectura basada en un solo satélite, a una arquitectura distribuida. Este tipo de arquitectura es conocida como Distribute Satellite Systems" (DSS). La aparición de esta nueva estructura ha provocado un cambio en el paradigma espacial, ya que ha surgido la necesidad de establecer comunicación entre los satélites para conseguir los objetivos de las misiones. Aunque exista la necesidad de emular y simular las comunicaciones entre satélites, ninguna de las actuales herramientas tiene las funcionalidades suficientes para conseguir dicha emulación y simulación. Este trabajo de fin de grado presenta las contribuciones hechas a un simulador ya existente, el cual ha sido desarrollado por el NanoSat Lab de la UPC. La contribución hecha consiste en la implementación de un subsistema que modela una EPS. Además, este trabajo de fin de grado también contribuye al desarrollo de un Satellite Contact Emulator, el cual ha sido desarrollado por i2Cat. Esta contribución pone un énfasis especial en el ordenador central que ejecuta la emulación

A Priority Rate-Based Routing Protocol for wireless multimedia sensor networks

The development of affordable hardware has made it possible to transmit multimedia data over a wireless medium using sensor devices. Deployed sensors span larger geographical areas, generating different kinds of traffic that need to be communicated either in real-time or non-real-time mode to the sink. The tiny sized design of sensor nodes has made them even more attractive in various environments as they can be left unattended for longer periods. Since sensor nodes are equipped with limited resources, newer energy-efficient protocols and architectures are required in order to meet requirements within their limited capabilities when dealing with multimedia data. This is because multimedia applications are characterized by strict quality of service requirements that distinctively differentiate them from other data types during transmission. However, the large volume of data produced by the sensor nodes can easily cause traffic congestion making it difficult to meet these requirements. Congestion has negative impacts on the data transmitted as well as the sensor network at large. Failure to control congestion will affect the quality of multimedia data received at the sink and further shorten the system lifetime. Next generation wireless sensor networks are predicted to deploy a different model where service is allocated to multimedia while bearing congestion in mind. Applying traditional wireless sensor routing algorithms to wireless multimedia sensor networks may lead to high delay and poor visual quality for multimedia applications. In this research, a Priority Rate-Based Routing Protocol (PRRP) that assigns priorities to traffic depending on their service requirements is proposed. PRRP detects congestion by using adaptive random early detection (A-RED) and a priority rate-based adjustment technique to control congestion. We study the performance of our proposed multi-path routing algorithm for real-time traffic when mixed with three non real-time traffic each with a different priority: high, medium or low. Simulation results show that the proposed algorithm performs better when compared to two existing algorithms, PCCP and PBRC-SD, in terms of queueing delay, packet loss and throughput

Transmission Power and Effects on Energy Consumption and Performance in MANET

This paper explores the effect that transmission power has on the performance of a Mobile Ad hoc Network (MANET). The goal of this research is to determine if the lifetime of the network can be prolongated by using less energy and thus, resulting in a more energy efficient ‘greener’ architecture. A total of 72 unique simulations are conducted of various configurations covering a large variety of possible scenarios: we examined configurations with a different number of nodes, number of traffic flows, mobility model, transmission power and geographical areas. Results show that there is an optimal transmission power, which enhances greater network performance: moreover, this optimal transmission setting makes the network more energy efficient in terms of depletion of the finite energy sources of the nodes. Our overall findings also confirm that higher transmission power results in less energy consumptio

Energy-aware Gossip Protocol for Wireless Sensor Networks

Dissertação de mestrado em Engenharia InformáticaIn Wireless Sensor Networks (WSNs), typically composed of nodes with resource constraints, leveraging efficient processes is crucial to enhance the network longevity and consequently the sustainability in ultra-dense and heterogeneous environments, such as smart cities. Epidemic algorithms are usually efficient in delivering packets to a sink or to all it’s peers but have poor energy efficiency due to the amount of packet redundancy. Directional algorithms, such as Minimum Cost Forward Algorithm (MCFA) or Directed Diffusion, yield high energy efficiency but fail to handle mobile environments, and have poor network coverage. This work proposes a new epidemic algorithm that uses the current energy state of the network to create a topology that is cyclically updated, fault tolerant, whilst being able to handle the challenges of a static or mobile heterogeneous network. Depending on the application, tuning in the protocol settings can be made to prioritise desired characteristics. The proposed protocol has a small computational footprint and the required memory is proportional not to the size of the network, but to the number of neighbours of a node, enabling high scalability. The proposed protocol was tested, using a ESP8266 as an energy model reference, in a simulated environment with ad-hoc wireless nodes. It was implemented at the application level with UDP sockets, and resulted in a highly energy efficient protocol, capable of leveraging extended network longevity with different static or mobile topologies, with results comparable to a static directional algorithm in delivery efficiency.Em Redes de Sensores sem Fios (RSF), tipicamente compostas por nós com recursos lim-itados, alavancar processos eficientes é crucial para aumentar o tempo de vida da rede e consequentemente a sustentabilidade em ambientes heterogéneos e ultra densos, como cidades inteligentes por exemplo. Algoritmos epidêmicos são geralmente eficientes em en-tregar pacotes para um sink ou para todos os nós da rede, no entanto têm baixa eficiência energética devido a alta taxa de duplicação de pacotes. Algoritmos direcionais, como o MCFA ou de Difusão Direta, rendem alta eficiência energética mas não conseguem lidar com ambientes móveis, e alcançam baixa cobertura da rede. Este trabalho propõe um novo protocolo epidêmico que faz uso do estado energético atual da rede para criar uma topologia que por sua vez atualizada ciclicamente, tolerante a falhas, ao mesmo tempo que é capaz de lidar com os desafios de uma rede heterogênea estática ou móvel. A depender da aplicação, ajustes podem ser feitos às configurações do protocolo para que o mesmo priorize determinadas características. O protocolo proposto tem um pequeno impacto computacional e a memória requerida é proporcional somente à quantidade de vizinhos do nó, não ao tamanho da rede inteira, permitindo assim alta escalabilidade. O algoritmo proposto foi testado fazendo uso do modelo energético de uma ESP8266, em um ambiente simulado com uma rede sem fios ad-hoc. Foi implementado à nível aplicacional com sockets UDP, e resultou em um protocol energeticamente eficiente, capaz de disponibilizar alta longevidade da rede mesmo com diferentes topologias estáticas ou móveis com resultados comparáveis à um protocolo direcional em termos de eficiência na entrega de pacotes

Energy-Aware Mobile Learning:Opportunities and Challenges

As mobile devices are becoming more powerful and affordable they are increasingly used for mobile learning activities. By enabling learners' access to educational content anywhere and anytime, mobile learning has both the potential to provide online learners with new opportunities, and to reach less privileged categories of learners that lack access to traditional e-learning services. Among the many challenges with mobile learning, the battery-powered nature of mobile devices and in particular their limited battery life, stands out as one issue that can significantly limit learners' access to educational content while on the move. Adaptation and personalisation solutions have widely been considered for overcoming the differences between learners and between the characteristics of their mobile devices. However, while various energy saving solutions have been proposed in order to provide mobile users with extended device usage time, the areas of adaptive mobile learning and energy conservation in wireless communications failed to meet under the same umbrella. This paper bridges the two areas by presenting an overview of adaptive mobile learning systems as well as how these can be extended to make them energy-aware. Furthermore, the paper surveys various approaches for energy measurement, modelling and adaptation, three major aspects that have to be considered in order to deploy energy-aware mobile learning systems. Discussions on the applicability and limitations of these approaches for mobile learning are also provided