Giannis Kazdaridis

Online energy consumption monitoring of wireless testbed infrastructure through the NITOS EMF framework

Development of energy-efficient protocols and algorithms requires in-depth understanding of the power consumption characteristics of real world devices. To this aim, energy efficiency analysis is performed by the research community, mainly focusing on the development of power consumption models. However, recent studies [1] have highlighted the inability of existing models to accurately estimate energy consumption even in non-composite scenarios, where the operation of a single device is analyzed. The inability of such models is further highlighted under real life scenarios, where the impact induced by the simultaneous operation of several devices renders the application of traditional models completely inappropriate. As a result, energy efficiency evaluation under complex configurations and topologies, needs to be experimentally investigated through the application of online monitoring solutions. In this work, we propose the innovative NITOS Energy consumption Monitoring Framework (EMF) able to support online monitoring of energy expenditure, along with the experiment execution. The developed framework is built on a distributed network of low-cost, but highly accurate devices and is fully integrated with the large-scale wireless NITOS testbed. Framework evaluation is performed under both low-level experiments that demonstrate the platforms high-level accuracy, as well as through high-level experiments that showcase how online and distributed monitoring can facilitate energy performance assessment of realistic testbed experiments.

Experimental evaluation and comparative study on energy efficiency of the evolving IEEE 802.11 standards

Over the last decade, the IEEE 802.11 has emerged as the most popular protocol in the wireless domain. Since the release of the first standard version, several amendments have been introduced in an effort to improve its throughput performance, with the most recent one being the IEEE 802.11n extension. In this paper, we present experimentally obtained results that evaluate the energy efficiency of the base standard in comparison with the latest 802.11n version, under a wide range of settings. To the best of our knowledge, our work is the first to provide such a detailed comparative analysis on the performance of both standards. The followed power measurement methodology is based on custom-built hardware that enables online energy consumption evaluation at both the wireless transceiver and the total node levels. Based on in-depth interpretation of the collected results, we remark that the latest standard enables significant improvement of energy efficiency, when combined with standard compliant frame aggregation mechanisms. Our detailed findings can act as guidelines for researchers working on the design of energy efficient wireless protocols.

Novel metrics and experimentation insights for dynamic frequency selection in wireless LANs

The rapidly increasing popularity of IEEE 802.11 WLANs has created unprecedented levels of congestion in the unlicensed frequency bands, especially in densely populated urban areas. Performance experienced by end-users in such deployments is significantly degraded due to contention and interference among adjacent cells. In this paper, we develop novel metrics and insights that we use for dynamic frequency selection, incorporating the various features that affect interference. The proposed scheme features a novel client feedback mechanism, which enables nodes of the cell, as well as nodes belonging to different cells, to contribute to interference measurements. Furthermore, we incorporate a traffic monitoring scheme that makes the system aware of prevailing traffic conditions. We design a distributed protocol, through which messages containing the information above are passed by the stations to the access-points, where the frequency selection is performed in a dynamic form. The proposed algorithm is implemented in the Mad-WiFi open source driver and is validated through extensive testbed experiments in both an indoor RF-Isolated environment, as well as in a interference-rich, large-scale wireless testbed. Results obtained under a wide range of settings, indicate that our algorithm improves total network throughput, up to a factor of 7.5, compared to state-of-the-art static approaches.

NITOS energy monitoring framework: real time power monitoring in experimental wireless network deployments

Development of energy-efficient protocols and algorithms requires in-depth understanding of the power consumption characteristics of real world devices. To this aim, energy efficiency analysis is performed by the research community, mainly focusing on the development of power consumption models. However, recent studies [1] have highlighted the inability of existing models to accurately estimate energy consumption even in non-composite scenarios, where the operation of a single device is analyzed. The inability of such models is further highlighted under real life scenarios, where the impact induced by the simultaneous operation of several devices renders the application of traditional models completely inappropriate. As a result, energy efficiency evaluation under complex configurations and topologies, needs to be experimentally investigated through the application of online monitoring solutions. In this work, we propose the innovative NITOS Energy consumption Monitoring Framework (EMF) able to support online monitoring of energy expenditure, along with the experiment execution. The developed framework is built on a distributed network of low-cost, but highly accurate devices and is fully integrated with the large-scale wireless NITOS testbed. The framework evaluation is performed under both low-level experiments that demonstrate the platforms high-level accuracy, as well as through high-level experiments that showcase how online and distributed monitoring can facilitate energy performance assessment of realistic testbed experiments.

Demonstration of a Vehicle-to-Infrastructure (V2I) Communication Network Featuring Heterogeneous Sensors and Delay Tolerant Network Capabilities

The development of applications based over vehicular networks, such as road safety, environmental information etc. require a complete testbed platform for research and evaluation. Such a platform will be provided by NITOS[1] testbed, that will include nodes mounted on cars and fixed nodes of the testbed operating as road side units (RSU). Besides the wireless infrastructure, there will be several sensors regarding the environmental conditions and the vehicle. These will gather measurements about air conditions and GPS data such as position and speed and will be collected in a central database, where the experimenter will be able to depict them in a Google map.

NITOS BikesNet: Enabling Mobile Sensing Experiments through the OMF Framework in a City-Wide Environment

In this paper we present the NITOS Bikes Net platform, a city-scale mobile sensing infrastructure that relies on bicycles of volunteer users. NITOS Bikes Net employs a custom-built embedded node that can be equipped with different types of sensors, and which can be easily mounted on a bicycle in order to opportunistically collect environmental and WiFi measurements in different parts of the city. Experimenters can remotely reserve and control the sensor nodes on bicycles as well as collect/visualize their measurements via the OMF/OML framework, which was extended in order to handle the intermittent connectivity and disconnected operation of the mobile nodes. We also provide a performance analysis of our node prototype in terms of sensing latency, end-to-end data transmission capability and power consumption, and report on a first experiment that was performed using NITOS Bikes Net in the city of Volos, Greece.

Enabling mobile sensing through a DTN framework

Participatory Sensing is the concept of distributed data collection by self-selected participants. By exploiting latest technologys smart devices, a large number of valuable information can be collected through embedded sensors and also be uploaded using provided services. Environmental measurements such as temperature or pollution, while also real-time data considering products information (i.e. prices, availability, offers), can be provided through such a framework. In this paper we present the NITOS mobile framework for data collection, that exploits vehicles moving around in a city. The proposed framework consists of low-sized wireless devices mounted on volunteers vehicles, as well as of static deployed Road Side Units (RSUs) providing the backbone connection for data acquisition. The extracted measurements concern air temperature and humidity plus the available WiFi networks operating in each area.

The TREND experimental activities on “green” communication networks

Aimed at answering important questions about the energy demand of current telecom infrastructure and the design of sustainable and energy-efficient future networks, the research of a number of European partners is brought together in the TREND project. In this paper we present the achievements of the Work Package coordinating the experimental activities of the project - WP4. Although not presenting a completely finished portrait yet, the results shown help building a better global view on the “big picture” in the field of energy-efficient networking.

A Demonstration of a Relaying Selection Scheme for Maximizing a Diamond Network’s Throughput

We demonstrate a queue-aware algorithm studied in a diamond network topology. This algorithm’s decisions are obtained from an analytical optimization framework relying on our technical work [4] and we devise an implementation part by modifying the features of ath9k driver [3] and click modular router [5]. Performance evaluation is conducted through experimentation on the NITOS Wireless Testbed and it reveals a significant rise in total throughput considering a particular networking scenario while also it maintains stability of backlog queues when schedules indicated by Lyapunov-based technique as throughput optimal are selected.

Enabling experimentation in mobile sensing scenarios through 4G networks: The NITOS approach

Wireless technologies have evolved rapidly over the past years, directly affecting our everyday living with the wide penetration of smart mobile devices. As such, the research community has placed major efforts in shaping and forming the future wireless technologies for enhanced end-user experience. Nevertheless, protocols and algorithms over wireless networks are better evaluated in real world scenarios, where simulations and complex theoretical models fail to characterize and emulate their behavior. Networking experimental facilities (testbeds) fill this gap by allowing experimental network measurements to serve as a basis for extracting valuable findings. In this paper, we present the extensions to the NITOS testbed for supporting experimentation in mobile sensing scenarios, by employing smartphones in vehicular environments, communicating using WiFi and 4G networks. We emphasize on the ease of configuration, execution and reproducibility of these experiments, leveraging the hardware and software tools provided by the NITOS testbed.