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Intra-operator spectrum sharing concepts for energy efficiency and throughput enhancement

Publication . Holland, Oliver; Attar, Alireza; Cabral, Orlando Manuel Brito; Velez, Fernando J.; Aghvami, A. Hamid

Cognitive radio and other dynamic spectrum sharing paradigms have enjoyed the limelight recently for their potential to realize a number of benefits for communications systems. The majority of investigated solutions thus far have looked at primary/secondary access and sharing of spectrum among different spectrum owners. In contrast, this paper investigates solutions for spectrum sharing among different bands owned by the same entity, such as a mobile operator, and demonstrates considerable potential for such solutions to improve power efficiency for the network and to increase throughput. The paper utilizes four means to achieve this potential: spectrum sharing through the opportunistic movement of users between bands allowing radio network equipment in other bands to be switched off when possible, spectrum sharing to opportunistically improve links’ propagation characteristics therefore reducing necessary transmission power, better interference management in spectrum sharing to reduce necessary transmission power, and the opportunistic aggregation of spectrum bands to increase achievable throughput. Power consumption reductions of over 50%, both in terms of mains power draw and in terms of necessary transmission power, are demonstrated. Moreover, throughput enhancements of up to 20% are achieved.

2010-11Conference object

Open access

Survey on the Characterization and Classification of Wireless Sensor Network Applications

Publication . Borges, Luís M.; Velez, Fernando J.; Lebres, António S.

Nowadays, wireless sensor network (WSN) users are demanding more and more in terms of choice and diversity of applications. Hence, as the diversity of applications is increasing, it is worthwhile to propose a structure for the set of characterization parameters that allows sketching a taxonomy for WSN applications. This taxonomy is established via an application-oriented approach, identifying the specific services offered by each application. In this survey, we fill this gap in the WSN literature by describing the characterization parameters, organized into six different categories. Our taxonomy for application classification is centered on the different sets of parameters that have high impact on a given future WSN application. Typical attributes and values from related research works are considered as a reference, but in this survey, we propose inter- and intra-connections among the considered application groups. Based on these connections, new application groups have been proposed for applications that share common characterization parameters, along with a holistic overview of WSN application taxonomy and the discussion of the three generations of WSNs toward communication between things and the Internet of Things , as well as future trends for the development of WSN applications. Moreover, detailed parameters from different projects and authors in the field of WSNs are joined together for comparison purposes.

2014Journal article

Open access

Combined Hop Count and Received Signal Strength Routing Protocol for Mobility-Enabled WSNs

Publication . Ferro, João M.; Velez, Fernando J.

In this paper, a new routing protocol is proposed for Wireless Sensor Networks (WSNs). The scenario taken is a WSN to be deployed non-intrusively in moving vehicles. WSNs are a class of wireless networks that require specific protocols, whose execution occurs in resource-constrained nodes. As a consequence, the protocol that calculates the optimal path for the packets to reach the sink must be lightweight. In this context, not only the mobility of nodes is challenging, but also the energy consumption. The innovation introduced by this protocol is its combination of the Received Signal Strength Indicator (RSSI) and number of hops to find the best path for the packets, allowing to have the benefits in terms of end-to-end delay and packet delivery ratio. Simulation results show that, when compared with approaches that only take into account the number of hops or RSSI, the protocol increases the number of delivered packets, whilst decreasing the end-to-end delay and the energy consumption. It can also deliver up to 271% more packets, while using less 71% of energy than Flooding.

2012-09Conference object

Open access

Supporting unified distributed management and autonomic decisions: design, implementation and deployment

Publication . Ferreira, Carlos; Guardalben, Lucas; Gomes, Tomé; Sargento, Susana; Salvador, Paulo; Robalo, Daniel; Velez, Fernando

Nowadays, the prevailing use of networks based on traditional centralized management systems reflects on a fast increase of the management costs. The growth in the number of network equipments and services reinforces the need to distribute the management responsibilities throughout the network devices. In this approach, each device executes common network management functionalities, being part of the overall network management platform. In this paper, we present a Unified Distributed Network Management (UDNM) framework that provides a unified (wired and wireless) management network solution, where further different network services can take part of this infrastructure, e.g., flow monitoring, accurate routing decisions, distributed policies dissemination, etc. This framework is divided in two main components: (A) Situation awareness, which sets up initial information through bootstrapping, discovery, fault-management process and exchange of management information; (B) Autonomic Decision System (ADS) that performs distributed decisions in the network with incomplete information. We deploy the UDNM framework in a testbed which involves two cities ( ≈ ≈ 250 km between), different standards (IEEE 802.3, IEEE 802.11 and IEEE 802.16e) and network technologies, such as, wired virtual grid, wireless ad-hoc gateways, ad-hoc mobile access devices. The UDNM framework integrates management functionalities into the managed devices, proving to be a lightweight and easy-respond framework. The performance analysis shows that the UDNM framework is feasible to unify devices management functionalities and to take accurate decisions on top of a real network.

2017Journal article

Open access