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- GACN: Self-clustering genetic algorithm for constrained networksPublication . A. Martins, J.; Mazayev, Andriy; Correia, Noélia; Schutz, G.; Barradas, A.Extending the lifespan of a wireless sensor network is a complex problem that involves several factors, ranging from device hardware capacity (batteries, processing capabilities, and radio efficiency) to the chosen software stack, which is often unaccounted for by the previous approaches. This letter proposes a genetic algorithm-based clustering optimization method for constrained networks that significantly improves the previous state-of-the-art results, while accounting for the specificities of the Internet engineering task force, Constrained RESTful Environment (CoRE), standards for data transmission and specifically relying on CoRE interfaces, which fit this purpose very well.
- Resource design in constrained networks for network lifetime increasePublication . Correia, Noélia; Mazayev, Andriy; Schutz, G.; A. Martins, J.; Barradas, A.As constrained "things" become increasingly integrated with the Internet and accessible for interactive communication, energy efficient ways to collect, aggregate, and share data over such constrained networks are needed. In this paper, we propose the use of constrained RESTful environments interfaces to build resource collections having a network lifetime increase in mind. More specifically, based on existing atomic resources, collections are created/designed to become available as new resources, which can be observed. Such resource design should not only match client's interests, but also increase network lifetime as much as possible. For this to happen, energy consumption should be balanced/fair among nodes so that node depletion is delayed. When compared with previous approaches, results show that energy efficiency and network lifetime can be increased while reducing control/registration messages, which are used to set up or change observations.
- Quality of service in optical burst switching networksPublication . Barradas, Álvaro; Medeiros, Maria Carmo
- Planning the reassignment of frequencies in fiber-wireless access networksPublication . Correia, N.; Sabino, S.; Schutz, G.; Barradas, A.FiWi architectures have been proposed as efficient solutions to provide high bandwidth and ubiquity at access network areas. In multi-radio and multi-channel FiWi scenarios an effective frequency assignment should be done to radios so that higher throughput and low delay can be obtained and the best of such architectures is achieved. However, traffic conditions change over time meaning that radio channel reconfigurations can be done to improve network performance. In this article a methodology for FiWi frequency reassignment planning is proposed, together with two algorithms, that avoids service disruption and attempts to increase throughput, reduce delay and increase the overall QoS perceived by users. Results show that the RBR algorithm is the one able to better exploit channel reconfigurations, increasing parallel transmissions and reducing time division required by nodes at the transmission area of each other.
- Design of network coding based reliable sensor networksPublication . Al-hawri, Eman; Correia, Noélia; Barradas, A.Network coding can be very useful in achieving a balance between energy efficiency and end-to-end packet error in sensor networks, particularly if only a subset of the nodes act as encoding nodes. In this article, a mathematical model and a heuristic algorithm are proposed to plan for the best placement of encoding nodes while ensuring reliability. These approaches are also able to address scenarios where sensor networks, using different gateways, are federated. In this case a distributed storage system is required to ensure the recovery of packets when related coded packets arrive to the different gateways. The experimental results show that the adequate number and placement of encoding nodes can be effectively determined, significantly enhancing the performance of constrained sensor networks using network coding. (C) 2019 Elsevier B.V. All rights reserved.
- An energy-aware resource design model for constrained networksPublication . Correia, N.; Schütz, Gabriela; Mazayev, A.; Martins, J.; Barradas, A.The Internet of Things is expected to incorporate objects and sensor networks of all kinds, and in particular, constrained sensor networks where energy consumption is a critical issue. In order to increase the lifetime of such networks, intelligent and standard-based solutions should be used. Here, we address this challenge through the use of CoRE interfaces for the resource design. These interfaces allow the server side to compose/organize resources and the client side to discover and determine how to consume such resources, besides allowing decisions to be easily integrated into the operation of the network. An energy-aware resource design model is proposed, based on CoRE interfaces, for the design of resources matching client needs. Based on this model, we develop an algorithm that proved to be energy efficient.
- RELOAD/CoAP P2P Overlays for Network Coding Based Constrained EnvironmentsPublication . Al-hawri, Eman; Correia, Noélia; Barradas, Álvaro; Camarinha-Matos, L. M.; Parreira-Rocha, M.; Ramezani, J.The Internet of Things will bring into the Internet all kinds of smart systems, which will be able to interact with each other. Therefore, applications relying on data sharing for collaboration will increase, and effective distributed solutions for data storage become necessary. This need led to the proposal of a CoAP Usage for RELOAD, a generic P2P protocol that accepts pluggable application layers (Usages). This allows P2P overlay networks to be built where constrained systems store their data and clients are able to retrieve it. Since many smart systems rely on wireless networks to communicate, where network coding can be used to reduce packet error rate, P2P overlays should be prepared to store data from network coding based networks. More specifically, encoding vectors and encoded data must be stored, and a decoding service is required. In this article, we propose a CoAP Usage extension so that network coding based constrained networks can use RELOAD/CoAP P2P distributed storage.
- A bounded heuristic for collection-based routing in wireless sensor networksPublication . Schütz, Gabriela; Correia, Noélia; Martins, Jaime; Mazayev, Andriy; Barradas, ÁlvaroWireless sensor networks are used to monitor and control physical phenomena and to provide interaction between clients and the physical environment. Clients have been typically users or user applications, but next generation wireless sensor networks will also work in machine-to-machine scenarios where some nodes can be interested in some other nodes' data. These scenarios may run the risk of becoming overloaded with messaging, a pernicious fact in particular for constrained networks where both bandwidth and power supply are limited. Resource collections can be used in wireless sensor networks to improve bandwidth usage and to reduce energy consumption, reducing the overall number of notification packets and wrapping overhead, required for the delivery of sensor data. This article proposes a heuristic algorithm for the planning of both routing and collections, in wireless sensor networks. Results show that collections are always worthwhile, and that the heuristic is able to find feasible and cost effective solutions, approaching its lower bound.