The Fog-based Home Automation Platform (FOGHA) is a novel Fog-based smart home platform that utilizes real-time containerized service deployment and task-offloading over its computing nodes. Fog is the middle computing layer that is physically near to the Things layer (connected appliances) and is composed of multiple Fog nodes that are orchestrated in a distributed manner. The architecture supports intra-Fog and inter-layer task offloading mechanisms via the real-time deployment of containerized services. The delay-sensitive services are mostly performed among Fog nodes, whereas the resource-demanding tasks are offloaded to the Cloud nodes. FOGHA utilizes software services as Docker containers, which is a novel approach for resource-scarce Fog nodes compared to existing automation platforms. Our experiments proved that resource-demanding tasks such as face recognition could also be collectively performed within the Fog layer, revealing that Fog layer nodes can provide the Cloud layer’s computational power and service variety.

As more complex and distributed applications come into play in today's Internet architecture, the need to have the adequate network architecture to support them with greater speed at lower costs has gained importance. Evolution in the nature of the applications have started to put significant stress on the networks and data centers which have to accommodate the demands of the highly distributed applications. Even though dedicated load balancers for each server can be used, this method is not cost effective and it is vulnerable to congestion and failure. In order to circumvent this problem, dynamic load balancing schemes, which adapt themselves to real-time network traffic, should be adopted. Frequent monitoring of the network traffic allows the load to be distributed fairly over the resources, but since it increases the communication overhead in the network, it deteriorates the system performance in terms of throughput and latency. In this work, our goal is to investigate how fairness and network performance are affected by fine tuning the monitoring and flow rule timeout parameters of an OpenFlow-based dynamic load balancer for data centers which uses real-time network traffic to make traffic-adaptive routing decisions.

Mobile sinks are proposed as a possible solution to the hotspot problem, which leads to the early death of the nodes close to the sink, due to the concentration of data traffic towards the sinks. However, the route updates employed by the source nodes to determine the position of the sinks introduce an overhead in terms of data reporting delays and energy consumptions. On the other hand, decreased frequency of route updates causes stale sink position information to be utilized for data packets which results in suboptimal data dissemination paths. In this paper, we investigate this inherent trade-off and provide an insight on how to fine tune the route update parameters of a mobile sink routing protocol. For this purpose, we define a system employing a simple routing protocol and determine the optimal operating points from the results obtained via simulations, under varying degrees of route updates and sink mobility.

Emerging multimedia applications for sensor networks require the co-existence of different types of traffic with different QoS provisions in terms of latency and throughput. Prioritization-based service differentiation mechanisms are applied in all layers of communication to satisfy the QoS requirements of each traffic class. The prioritization in the contention is one of these differentiation methods applied in the medium access layer. In this article, we propose an analytical model for the contention latencies and energy expenditures of different classes in a prioritized contention structure with uniform backoff scheme. The contention window is divided into three partitions which are allocated for the use of only high-priority, both priorities, and only low-priority classes. We further generalize the model for binary exponential backoff schemes and for more than two priority classes. In the analysis, we explore the optimum sizes of these partitions in terms of contention latency and the total energy expenditure for each priority class. Our model is also useful for the evaluation of various recent contention prioritization schemes in WSNs.

In a typical wireless sensor network, the batteries of the nodes near the sink deplete quicker than other nodes due to the data traffic concentrating towards the sink, leaving it stranded and disrupting the sensor data reporting. To mitigate this problem, mobile sinks are proposed. They implicitly provide load-balanced data delivery and achieve uniform-energy consumption across the network. On the other hand, advertising the position of the mobile sink to the network introduces an overhead in terms of energy consumption and packet delays. In this paper, we propose Ring Routing, a novel, distributed, energy-efficient mobile sink routing protocol, suitable for time-sensitive applications, which aims to minimize this overhead while preserving the advantages of mobile sinks. Furthermore, we evaluate the performance of Ring Routing via extensive simulations.

Congestion is a challenging problem for sensor networks because it causes the waste of communication and reduces energy efficiency. Compared to traditional wireless sensor networks, the probability of congestion occurrence in wireless multimedia sensor networks is higher due to the high volume of data arising from multimedia streaming. In this article, problems for multimedia transmission over wireless multimedia sensor networks are examined and sensor fuzzy-based image transmission (SUIT); a new progressive image transport protocol is proposed as a solution. SUIT provides fuzzy logic-based congestion estimation and an efficient congestion mitigation technique which decreases the image quality on-the-fly to an acceptable level. In case of congestion, SUIT drops some packets of the frames in a smart way and thus transmits frames to the sink with lower, but acceptable quality. In this way, SUIT improves the continuity of the video streaming. We evaluate the performance of SUIT by comparing it with two different competitors. The first one is an example transport protocol, namely Fuzzy Logic-Based Congestion Estimation. The second one is a buffer occupancy-based congestion control mechanism which is commonly used in previous studies. According to the simulation results, SUIT provides better energy consumption, frame delivery, frame loss and frame latency performance than its competitors.

The concentration of data traffic towards the sink in a wireless sensor network causes the nearby nodes to deplete their batteries quicker than other nodes, which leaves the sink stranded and disrupts the sensor data reporting. To mitigate this problem the usage of mobile sinks is proposed. Mobile sinks implicitly provide load-balancing and help achieving uniform energy-consumption across the network. However, the mechanisms to support the sink mobility (e.g., advertising the location of the mobile sink to the network) introduce an overhead in terms of energy consumption and packet delays. With these properties mobile sink routing constitutes an interesting research field with unique requirements. In this paper, we present a survey of the existing distributed mobile sink routing protocols. In order to provide an insight to the rationale and the concerns of a mobile sink routing protocol, design requirements and challenges associated with the problem of mobile sink routing are determined and explained. A definitive and detailed categorization is made and the protocols' advantages and drawbacks are determined with respect to their target applications.

The main objective in a wireless sensor network design is to minimize the energy expenditure for sustaining a long lifetime. Moreover, some recent multimedia applications require the network to satisfy specific throughput and delay constraints for large data sizes. In this paper, we analytically derive the expected throughput and the expected energy expenditure for a synchronized contention-based duty cycled MAC protocol. Our analysis explores the combined effect of contention window size, duty cycle and data size on throughput and energy expenditure for a successful transmission. We show that the performance of the network in terms of both metrics fluctuates with increased duty cycle as opposed to the general intuition that an increase in duty cycle increases the throughput and decreases the energy expenditure in the network. The results, validated by simulations, show that in order to provide an efficient MAC operation, the contention window size and the duty cycle should be optimized together for a given data size.

Forest fires are catastrophes which threaten the natural and human life. Economical, natural and cultural devastation caused by forest fires render the early detection and prevention of forest fires necessary. The success of a forest fire detection system can be assessed in terms of its accurate and quick detection capabilities. It is observed that wireless sensor networks (WSN) have a higher performance in especially early fire detection and high resolution fire monitoring compared to the existing fire detection systems. Temperature and humidity information of particular forest locations can be measured in real-time through the dense deployment of numerous sensors to a particular forest area and these information can be transmitted to the fire-fighting management center quickly. In this study, we evaluate the performance of a heterogeneous WSN-based architecture consisting of various types of devices, which is proposed in the scope of the FP7 FIRESENSE project to increase the capabilities of WSNs, with realistic fire propagation and network simulation experiments. Furthermore, we present a glance at the real life demonstrations.

Forest fires lead to high amount of environmental and economic loss all over the world. Prevention and early detection efforts aim to eliminate or minimize the damage that will be caused by a fire incident. Current surveillance systems for forest fires do not provide dense real-time monitoring and hence they lack prevention or early detection of a fire threat. Wireless sensor networks (WSNs), on the other hand, can collect real-time information such as temperature and humidity from almost all points of a forest and can provide fresh and accurate data for the fire-fighting management center quickly. In this work, we aim to evaluate the reporting performance of a WSN under realistic workload. Since fires are destructive and burning a deployed WSN is not feasible, simulation is the appropriate way to assess the reporting capability of a WSN during a forest fire. We integrate WSN simulator with a realistic fire propagation simulator which is modified to provide time based temperature field information while the fire propagates through the deployment area. Temperature information is used for the generation of realistic workloads and the determination of sensor destruction times that affects the routing decisions in WSN simulations. We present the effects of WSN related factors; such as reporting rate, number of the sinks, and the sink locations together with the effects of environmental factors such as the wind speed and the number of ignition points in terms of temperature reporting performance and freshness of temperature map.

Congestion is a challenging problem in wireless sensor networks, which exacerbates with the high volume of data traffic imposed by video applications such as video surveillance and target tracking. Deployment of multiple sinks is a candidate solution for congestion and is also promising in terms of reliability and energy-efficiency. In order to gain the maximum benefit from multiple sinks, it is essential to distribute the load among them evenly. In this paper, we propose a cross layer geographic forwarding scheme MLBRF (Multi-Sink Load Balanced Reliable Forwarding) which aims to provide reliable and energy efficient video delivery in a multi-sinked sensor network for target tracking. In order to provide load balancing among the sinks, MLBRF proposes a sink selection mechanism based on fuzzy logic for the frame forwarding which evaluates the traffic density in the direction of each sink by combining two dynamic criteria which are the number of contenders and the buffer occupancy levels in the neighborhood with the static distance criterion. The performance of the fuzzy sink selection mechanism is compared using simulation with various sink selection mechanisms. The results show that MLBRF gains the maximum benefit from deploying multiple sinks in terms of reliability, latency and energy efficiency by using the proposed fuzzy sink selection mechanism.

Heterogenous Wireless Sensor Networks (HWSNs) are composed of two or more types of sensor nodes having different capabilities such as transmission power, sensing range, lifetime, computation power. In this work, we define a unique routing protocol for HWSNs which treats each traffic type according to its specific requirements. We are mainly focusing on fire sensing applications and in that case the area is commonly a mountainous region and topology of our example scenario is like a double sided cone. Performance evaluation of our proposed routing protocol show that our protocol delivers each traffic type without violating their constraints while balancing the energy expenditure to prolong the network lifetime. M. Aykut Yigitel Bogazici University Dept. of Computer Engineering, e-mail: aykut.yigitel@boun.edu.tr, H. Birkan Yilmaz Bogazici University Dept. of Computer Engineering, e-mail: birkan.yilmaz@boun.edu.tr, Tuna Tugcu Bogazici University Dept. of Computer Engineering, e-mail: tugcu@boun.edu.tr

Congestion is a challenging problem for sensor networks because it causes the waste of communication and reduces energy efficiency. In this article, problems for multimedia transmission over wireless multimedia sensor networks are examined and Sensor fUzzy-based Image Transmission (SUIT); a new cross-layer progressive image transport protocol is proposed as a solution. SUIT provides a fuzzy logic based congestion estimation and a novel congestion mitigation technique which decreases image quality on-the-fly at an acceptable level. In case of congestion, SUIT drops some packets of the frames in a smart way and thus transmits frames to the sink with lower, but acceptable quality. In this way, SUIT improves the continuity of the video streaming. We evaluate the performance of SUIT by comparing it with two example transport protocols, namely Event- to-Sink Reliable Transport and Fuzzy Logic Based Congestion Estimation, proposed for wireless sensor networks. According to our simulation results, SUIT provides better energy consumption, frame delivery, frame loss and frame latency performance than its competitors.

In this paper, we propose two cross layer geographic forwarding schemes which address congestion in wireless video sensor networks (VSN) to provide reliable video delivery. The first scheme Load Balanced Reliable Forwarding (LBRF) introduces the notion of local load balancing where a sensor dynamically determines the next hop among the alternative neighbors providing positive advancement towards the sink by considering the balance of their buffer occupancy levels at the time of delivery. LBRF utilizes a modified version of SMAC where the packet structure as well as the operation of SMAC is modified for the accurate monitoring of the buffer occupancy conditions of the neighbors. The second scheme Directional Load Balanced Spreading (DLBS) combines local and direction-based (spatial) load balancing approaches to provide more reliable and faster video delivery by benefiting from the advantages of both approaches. The performance of the forwarding schemes are compared using simulation with two geographic routing schemes where one applies no load balancing and the other applies spatial load balancing. The results show that both LBRF and DLBS provide more reliable video delivery as compared to other schemes, whereas DLBS is more reliable and faster as compared to LBRF. In addition, DLBS provides more energy efficient video delivery in terms of energy expenditure per successfully delivered frame to the sink as compared to LBRF and the other two schemes.

Wireless Information Delivery Environment (WIDE) is a distributed data dissemination system, which uses IEEE 802.11b technology. WIDE aims to deliver popular information services to registered mobile clients in WLAN hot spots. Data delivery is based on broadcasting and multicasting to provide scalability and efficient use of the wireless channel. Reliability is assured with a combination of Forward Error Correction (FEC), data carousel, and ARQ techniques. This paper presents the proposed system architecture with the details of reliable and secure data dissemination mechanisms. Functional evaluation of the proposed system and mechanisms on the implemented prototype are also included in this paper.

Publisher UPGRADE is published on behalf of CEPIS (Council of European Professional Informatics Societies, <http://www.cepis.org/>) by NOVÁTICA <http://www.ati.es/novatica/>, journal of the Spanish CEPIS society ATI (Asociación de Técnicos de Informática <http://www.ati.es/>). UPGRADE is also published in Spanish (full issue printed, some articles online) by NOVÁTICA, and in Italian (abstracts and some articles online) by the Italian CEPIS society ALSI <http://www.alsi.it> and the Italian IT portal Tecnoteca <http://www.tecnoteca.it/>. UPGRADE was created in October 2000 by CEPIS and was first published by NOVÁTICA and INFORMATIK/INFORMATIQUE, bimonthly journal of SVI/FSI (Swiss Federation of Professional Informatics Societies, <http://www.svifsi.ch/>).

We developed an information delivery system, namely WIDE (Wireless Information Delivery Environment), in client-server architecture using 802.11b infrastructure. WIDE aims to deliver popular information services to registered mobile clients in WLAN hot spots. We present the proposed system architecture, related delivery mechanism and communication protocols. We also give a brief overview of mechanisms required for secure and reliable communication in WIDE system. Performance evaluation results of the proposed system using the implemented prototype are also included in this paper.

Publisher UP GRADE is published on behalf of CEPIS (Council of European Professional Informatics Societies, <http://www.cepis.org/>) by NOVÁTICA <http://www.ati.es/novatica/>, journal of the Spanish CEPIS society ATI (Asociación de Técnicos de Informática <http://www.ati.es/>). UP GRADE is also published in Spanish (full issue printed, some articles online) by NOVÁTICA, and in Italian (abstracts and some articles online) by the Italian CEPIS society ALSI <http://www.alsi.it> and the Italian IT portal Tecnoteca <http://www.tecnoteca.it/>. UP GRADE was created in October 2000 by CEPIS and was first published by NOVÁTICA and INFORMATIK/INFORMATIQUE, bimonthly journal of SVI/FSI (Swiss Federation of Professional Informatics Societies, <http://www.svifsi.ch/>).

Publisher UPGRADE is published on behalf of CEPIS (Council of European Professional Informatics Societies, <http://www.cepis.org/>) by NOVÁTICA <http://www.ati.es/novatica/>, journal of the Spanish CEPIS society ATI (Asociación de Técnicos de Informática <http://www.ati.es/>). UPGRADE is also published in Spanish (full issue printed, some articles online) by NOVÁTICA, and in Italian (abstracts and some articles online) by the Italian CEPIS society ALSI <http://www.alsi.it> and the Italian IT portal Tecnoteca <http://www.tecnoteca.it/>. UPGRADE was created in October 2000 by CEPIS and was first published by NOVÁTICA and INFORMATIK/INFORMATIQUE, bimonthly journal of SVI/FSI (Swiss Federation of Professional Informatics Societies, <http://www.svifsi.ch/>).