Browsing by Author "Cardoso, Filipe"
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- Adaptive Allocation of Virtual Radio Resources overHeterogeneous Wireless NetworksPublication . Caeiro, Luísa; Cardoso, Filipe; Correia, LuísVirtual Networks and cloud services are hot topics nowadays, being considered, together with the information centric approach, key elements for the Future Internet. In this paper, an adaptive radio resource allocation mechanism for virtual resources sharing a common heterogeneous wireless infrastructure is presented and evaluated. The Virtual Network Radio Resource Allocation (VRRA) strategy being proposed takes advantage of the set of shared resources available within a cluster of wireless resources from different Radio Access Technologies (RATs), optimising their utilisation in order to maintain the contracted capacity. Simulation results show that the introduction of VRRA allows supporting the minimum bandwidth requirement in a wireless cluster, composed of several physical base stations from different RATs. For the Virtual Network providing high data rates and guaranteed services as presented in this paper, the Virtual Network Operator Satisfaction Level can be improved by 40% with the introduction of VRRA mechanisms.
- Addressing Multiple Virtual Resources in the Same Geographical AreaPublication . Caeiro, Luísa; Cardoso, Filipe; Correia, LuísThis paper addresses the virtualisation of wireless access in order to provide the required capacity (data rate) to a Virtual Base Station (VBS). The approach is based on a Virtual Radio Resource Allocation algorithm, OnDemandVRRA, which manages the allocation of the physical radio resources to VBSs’ end-users, in order to follow the contract and maintaining isolation among VBSs, according to the type of guarantees of the VBSs, the amount of contracted capacity, and VBSs’ utilisation. Taking the variability of the wireless medium into account, the algorithm continuously influences the RRM mechanisms, namely admission control and MAC scheduling, to be aware of the VBSs’ state relative to the service level agreement, in order to compensate for this variability. The algorithm has been tested to evaluate its behaviour, concerning the amount of VBSs created over a given geographical area served by a set of base stations. It can be concluded that changing the quantity of created VBSs as well as the contracted data rate in the cluster, GRT VBSs get their minimum contracted data rate. It is also verified that the best Radio resource Unit (RU) efficiency is achieved when the strategy for the overall capacity provision is to limit the capacity contracted by GRT VNets, overbooking the capacity contracted by BE VNets. In this case, the RU efficiency increases 30% comparing to the situation where the overbooking is done by GRT VBSs.
- Beamforming Strategies for Energy Efficient Transmission in LTEPublication . Cardoso, Filipe; Correia, Luís; Petersson, Sven; Boldi, MauroThe actual internet traffic growth is challenging the sustainability of mobile networks, therefore, the energy efficiency of the mobile communication infrastructure becomes a topic of particular relevance. Decreasing CO2 emissions and energy demands while expanding the mobile infrastructure to satisfy traffic demands is essential. In this paper the energy efficient use of beamforming techniques and active antennas, in which an advanced antenna is utilized to direct the transmitted signal in a narrow direction, is evaluated. Slow beamforming based on reconfigurable antennas, exploits medium/long term variations of traffic in order to save energy. Fast beamforming, on the contrary, is immediately following the traffic distribution and can even allow saving more energy. From simulations it is observed that, when compared to existing state-of-art bases base stations, in a dense urban environment reconfigurable beamforming allows a maximum gain of about 8%. Adaptive beamforming, allows an additional consumed power reduction of up to 40%. Hence, the overall power consumption reduction that can be achieved by combining these techniques can be as high as 50%.
- Energy Efficiency using Beamforming at the Base Station in UMTS and LTEPublication . Gonçalves, Tiago; Correia, Luís; Cardoso, FilipeThe race for energy aware systems is motivating the development of solutions that reduce the overall power consumption in telecommunication systems. In this paper, one studies the use of beamforming from an energy efficiency viewpoint in UMTS and LTE. Several user scenarios, with different users’ arrangements, were studied. Models were implemented to evaluate the potential impact that adaptive antennas can have to reduce the radiated power, compared to the current use of base station static sector antennas. With the use of beamforming, UMTS has a lot of interference suppression potential, besides signal improvement, enabling quite an increase in energy efficiency; LTE, due to the different multiple access technique, presents a different behaviour, coming from signal improvement. Through a statistical analysis, a model for UMTS that describes the achievable energy improvement as a function of the number of users and antennas is derived. For UMTS with carriers near top capacity, an energy reduction of 90% is achieved. For LTE, significant energy improvements are reached, 65% saving being obtained with 8 antennas.
- Energy Efficient TransmissionTechniques for LTEPublication . Cardoso, Filipe; Petersson, Sven; Boldi, Mauro; Mizuta, Shinji; Dietl, Guido; Torrea-Duran, Rodolfo; Desset, Claude; Leinonen, Jouko; Correia, LuísThe goal of the European ICT ProjectEARTH is to enhance energy efficiency of cur-rent LTE cellular networks by 50 percent,enabling operators to provide more extensivecoverage, namely to less densely populatedareas, while ensuring high levels of efficiency,hence, reducing the carbon footprint. In order toachieve this objective, different strategies, at dif-ferent levels, are being addressed. Energy effi-cient transmission techniques for LTE, proposedwithin the framework of EARTH, are addressedand discussed, with an emphasis on beamform-ing and MIMO. It is concluded that the strategicobjective of EARTH is achievable. CombinedMIMO mode selection, resource allocation,scheduling and precoding strategies will allow anenergy consumption reduction of more than 50percent in macro-cells. A reduction in MIMOpower consumption of 91.7 percent (factor of12) can be achieved in pico-cells
- Management of Resources in Virtual Radio NetworksPublication . Correia, Luís; Caeiro, Luísa; Cardoso, Filipe
- MIMO Gain and Energy Efficiency in LTEPublication . Cardoso, Filipe; Correia, LuísCurrent 3GPP specifications for LTE include the use of MIMO as a key technology. MIMO can be seen from two different perspectives: if increased data rates are targeted, for a given value of SNR, one gets improved data transmission; however, from an energy efficiency viewpoint, lower values of SNR are needed for the same reference data rate, therefore,allowing the reduction of the transmitted power, while providing the same data rate as the one for SISO. In this paper, a framework for evaluating the possible benefit of using MIMO instead of SISO, from the expected SNR improvement viewpoint is proposed, and results for different environments are presented and discussed. The proposed evaluation methodology allows one to properly assess the expected benefits of MIMO, therefore, providing guidelines to enable a proper SISO/MIMO mode selection according to the required service data rate. The analysis being presented is based on existing 3GPP models for data rateversus SNR in LTE. Simulation results for the ETU70 3GPP channel model are provided. It is observed that, for given reference data rates, significant SNR improvements can be obtained. Maximum values of 7.1, 15.7 and 18.0 dB SNR reduction are obtained for 2×2, 4×4 and 8×8 MIMO configurations, compared to the SISO case, therefore, allowing a significant reduction of the transmitted power, while providing the same target data rate as the one for SISO.
- MIMO Strategies for Energy Efficient Transmission in LTE Pico-cell EnvironmentsPublication . Cardoso, Filipe; Torrea-Duran, Rodolfo; Desset, Claude; Correia, LuísMobile data traffic is increasing at an unprecedented rate. To cope with this, operators are deploying small base station sites to cover hot spots. However, this also increases the total network energy expenditure and carbon footprint. As a consequence, improving the energy efficiency of small base stations remains a hot topic. In this paper energy efficient transmission in LTE pico-cell environments is addressed aiming at providing a basis for LTE networks optimization and carbon footprint reduction. MIMO is studied from an energy efficiency point of view rather than from an increased datarates perspective as usually found in literature. Additionally, duty-cycling in time and frequency is also considered, hence, improving the amount of power reduction that can be achieved. Globally, a factor of twelve times variation between the worst-case power consumption and the optimally selected MIMO mode is observed in pico-cells.
- Modelling of Statistical Fading Parameters in Maritime Container Terminal EnvironmentsPublication . Ferreira, Manuel; Ambroziak, Slawomir; Cardoso, Filipe; Sadowski, Jaroslaw; Correia, Luís
- OConS Supported On Demand Radio Resource Allocation for Virtual ConnectivityPublication . Caeiro, Luísa; Cardoso, Filipe; Correia, LuísWith the increase of mobile network utilisation, the virtualisation of wireless resources becomes an important issue in the overall Virtual Networks (VNets) process. In this paper, the On Demand Virtual Network Radio Resource Allocation (OnDemand VRRA) mechanism is proposed to take advantage of the set of shared resources available within a cluster of wireless resources from different Radio Access Technologies (RATs) for wireless virtualisation. Optimising resource utilisation satisfying the VNet contracted capacity is its main objective. Furthermore, the mechanism is modelled according to the Open Connectivity Services (OConS) architecture, in order to demonstrate the advantages of its use within the OConS framework. Simulation results show that the introduction of OnDemand VRRA allows supporting the minimum bandwidth requirement in a wireless cluster, composed of several physical base stations from different RATs. The percentage of operation out of contract (i.e., below the virtual operator’s contracted capacity) for a VNet with guaranteed minimum service is zero for a number of end users in the VNet up to 80% of the total, which is higher than in other circumstances. One also observes that VNets providing guaranteed services can achieve the contracted data rate independently of the number of end users in other VNets.