This paper presents an outdoor IoT-based air quality monitoring testbed deployed in the city of Uppsala, Sweden. Our IoT sensing unit is designed and developed using low-cost hardware components and open source software, which makes it easy to replicate. We demonstrate that it can serve as an affordable solution for real-time measurements and has potentials to complement traditional monitoring to cover larger areas. We use low-power communication based on IEEE 802.15.4, RPL, and MQTT, and achieve high end-to-end delivery ratio (>98%) in an outdoor setting. Moreover, we carry out network analysis of our testbed and provide detailed insights into its characteristics.

Energy efficiency has become a major concern in the design and operation of fixed networks. Energy-Efficient Ethernet (EEE) came as a response to reduce the energy consumption of Ethernet technology. The performance of EEE depends on the link utilization and may degrade when the utilization increases. This is especially true when an energy-aware routing (EAR) protocol is deployed on top of EEE as it tends to aggregate traffic over a subset of links, thereby increasing their utilization. This behavior introduces a tradeoff between EEE and EAR. As network traffic patterns change frequently, it requires a significant effort to configure the EAR protocol on an EEE network in order to reduce the downside effects of the tradeoff, thus benefiting from both the EEE and EAR energy efficiency. In this work, we propose a network matching and reconfiguration algorithm (NetRec), which dynamically adapts the topology control (ESTOP) settings of an EEE network to increase energy savings. Our reasoning is that larger energy savings can be obtained if the network topology is dynamically reconfigured according to traffic demand. NetRec is designed in the context of Software-Defined Networking (SDN). We evaluate NetRec's energy performance in networks of different sizes under varying traffic conditions.

Wired IP networks handle the bulk of today's communication. These networks are built with over-provisioning and redundancy of devices to support critical activities. However, the activities can vary significantly, resulting in unused network online waste of power. In this study, we examine two existing power-saving approaches for wired IP networks: i) uncoordinated sleeping and (ii) coordinated sleeping. The uncoordinated and coordinated sleeping algorithms investigated are respectively Energy Efficient Ethernet (EEE) and Energy-Aware Routing (EAR) for green OSPF. In addition, we investigate the combination of coordinated and uncoordinated sleeping algorithms, EEE and EAR for green OSPF. The energy performance of the two algorithms and their combination is evaluated in two networks of different dimensions under varying traffic loads. The investigation shows that EEE, EAR for green OSPF and the combination significantly reduce the energy consumption of a network. However, the highest peak of energy conservation is achieved when EAR for green OSPF is activated in an EEE network during lower traffic load periods and deactivated during high traffic load periods. © 2015 University of Split, FESB.

Wired IP networks handle the bulk of today’scommunication. These networks are built with over-provisioningand redundancy of devices to support critical activities. However,the activities can vary significantly, resulting in unused networkonline waste of power. In this study, we examine two existingpower-saving approaches for wired IP networks: i) uncoordinatedsleeping and (ii) coordinated sleeping. The uncoordinated andcoordinated sleeping algorithms investigated are respectively En-ergy Efficient Ethernet (EEE) and Energy-Aware Routing (EAR)for green OSPF. In addition, we investigate the combination ofcoordinated and uncoordinated sleeping algorithms, EEE andEAR for green OSPF. The energy performance of the twoalgorithms and their combination is evaluated in two networksof different dimensions under varying traffic loads.The investigation shows that EEE, EAR for green OSPF andthe combination significantly reduce the energy consumption ofa network. However, the highest peak of energy conservationis achieved when EAR for green OSPF is activated in an EEEnetwork during lower traffic load periods and deactivated duringhigh traffic load periods.

Limited memory capacity is one of the major constraints in Delay Tolerant Wireless Sensor Networks. Efficient management of the memory is critical to the performance of the network. This paper proposes a novel buffer management algorithm, SmartGap, a Quality of Information (QoI) targeted buffer management algorithm. That is, in a wireless sensor network that continuously measures a parameter which changes over time, such as temperature, the value of a single packet is governed by an estimation of its contribution to the recreation of the original signal. Attractive features of SmartGap include a low computational complexity and a simplified reconstruction of the original signal. An analysis and simulations in which the performance of SmartGap is compared with the performance of several commonly used buffer management algorithms in wireless sensor networks are provided in the paper. The simulations suggest that SmartGap indeed provides significantly improved QoI compared the other evaluated algorithms.

This paper investigates OpenFlow performance, focusing on how the delay between switch and OpenFlow controller can impact the performance of a network. We use open-source controllers that support network virtualization to evaluate how such delay impacts ICMP, TCP and UDP traffic. We compare the controllers’ flow set-up strategies and we conduct several experiments to compare their TCP and UDP performance. In ad-dition, we introduce a new metric to measure UDP packet losses at the beginning of the flow. The results of the measurements indicate that there are large differences in performance between controllers, and that performance depends on switch-controller delay and flow set-up strategy.

Doctor shortage is a universal problem. Technologies can be used to address the issue by extending the healthcare services over the data network to virtually anywhere. In this paper, we propose Carenet architecture to extend healthcare services to the home of a patient in a robust, secure, and cost-effective manner. The prototype architecture is developed using a residential gateway (RG). The RG is built using open source software on Commodity-Off-The-Shelf (COTS) hardware. It uses low-power components with multiple power sources to provide robustness. The healthcare services are offered over a private overlay network. Linux containers are used to provide service isolation on the RG. The data is encrypted at the application level for each service to ensure confidentiality. Resilient communication is realized based on physical redundant links from two Internet connections from different ISPs. The failover time within sub-seconds time frame is achieved using our prototype RG.

In line with the shift towards renewable energy, small-scale solar panels have become commonly available. Solar panels are intermittent energy sources producing direct current, and DC-DC converters are needed to convert between different voltage levels, both for different power loads and for storing energy. DC-DC converters typically have a very limited functionality and are statically configured for specific voltage levels. In this paper, we propose a new generation of flexible DC-DC converters with software and communication support (through Contiki and CoAP) for remote power monitoring and control. We present a prototype design and implementation of a DC-DC converter including a microprocessor, a lean operating system, and networking support. With such a DC-DC converter, controlled over the Internet, we can address various types of power and energy related issues and advance the state-of-the-art of green networked applications.

Today commodity mobile devices are equipped withmultiple wireless access technologies. To enable continuous connectivityit is vital that these terminals provide for vertical handover between different technologies. Particularly, they should provide a vertical handover that complies with the timeliness requirements of soft real-time applications. Considering aspects such as cost- and ease-of-deployment, application neutrality, and, not least, the emergence of transport protocols that support multi-homing such as mobile SCTP and multi-path TCP, we think it would be beneficial to handle vertical handover in thetransport layer of the mobile terminal. This paper demonstrates through several real-world experiments, the feasibility of using a lightweight vertical handover scheme in smart mobile terminals for live video streaming. The vertical handover criteria is basedon the received signal strength. Our experiments suggest that thescheme indeed provides for seamless vertical handover at walking speed – our target scenario. However, the experiments also suggest that the scheme gives significant reductions in handovertime, as compared to mobile SCTP without improvements, at higher speeds.