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Instituto de Telecomunicações
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A Novel Packet End-to-End Delay Estimation Method for Heterogeneous Networks
Publication . Fadhil, Diyar; Oliveira, Rodolfo; DEE - Departamento de Engenharia Electrotécnica e de Computadores; DEE2010-A1 Telecomunicações; Institute of Electrical and Electronics Engineers (IEEE)
The estimation of the end-to-end delay in modern communication networks is of high importance to support multiple services but also for the management of the network resources. In this paper, we propose an end-to-end delay model and estimation methodology for heterogeneous networks. The estimation method allows the computation of the end-to-end delay distribution parameters when a small number of end-to-end delay samples is available through probe packets. The proposed technique is evaluated for different datasets, including networks operating with multiple access technologies and different upper-layer protocols, so the heterogeneity of the networks and protocols can be taken into account. The evaluation results show that the Generalized Extreme Value distribution can be used to approximate the end-to-end delay and high accuracy is achieved even when only a small number of probe packets is available. Finally, the estimation error confirms the effectiveness of the proposed method for a broad range of network scenarios.
Interference Distribution for Directional Beamforming Mobile Networks
Publication . Abusabah, Ayman T.; Oliveira, Rodolfo; DEE - Departamento de Engenharia Electrotécnica e de Computadores; Institute of Electrical and Electronics Engineers (IEEE)
In this paper, we model the aggregate interference power in directional beamforming mobile networks. The work considers the random waypoint model to describe the mobility of the nodes and adopts directional beamforming for communication. The major contribution of this paper is the statistical characterization of the aggregate interference caused by directional beamforming transmissions of mobile interferers to a given node positioned at a reference point. The analysis assumes Rayleigh and Rician small-scale fading channels, a distance-based path-loss large-scale fading model, and a three gain levels sectored antenna model. The quality of the proposed approximations has been confirmed through various simulations for different mobility scenarios, channel conditions, and beamforming parameters, highlighting the effect of directional communications along with mobility on aggregate interference. To demonstrate the practical application of the work, we use two different estimators for the interference characterization. The results confirm the effectiveness of the estimators even when adopting a small set of samples.
Physical Layer Security with Near-field Beamforming
Publication . Ferreira, João; Guerreiro, João; Dinis, Rui; DEE - Departamento de Engenharia Electrotécnica e de Computadores; Institute of Electrical and Electronics Engineers (IEEE)
Extremely large antenna arrays (ELAAs) are being proposed for sixth-generation (6G) systems as an evolution of massive multiple-input, multiple-output (mMIMO). Besides having a large number of antennas, ELAAs can be physically large, which makes communication in the radiative near-field very likely. This means the plane wave approximation does not hold and channel models that accurately capture the propagation effects in the near-field are required. Recent works have highlighted the beam-focusing effect available in the near-field region, where antenna arrays can generate beams not only limited in width but also limited in depth. This work leverages a precise channel model for ELAAs with the aim of exploring the inherent physical layer security (PLS) features in the radiative near-field. For that purpose, it is presented a study on the power ratio between a legitimate and a malicious user, considering the effects of the field region, relative distance, and beamforming direction. By taking advantage of that analysis, it is shown that both the jamming rejection and the secrecy rate can be substantially improved when communicating in the near field, demonstrating that beam-focusing constitutes an interesting PLS technique for upcoming 6G communications.
Capacity and Energy Efficiency Trade-off in Multi-Packet Reception Wireless Systems
Publication . Abusabah, Ayman T.; Oliveira, Rodolfo; DEE - Departamento de Engenharia Electrotécnica e de Computadores
The radio access in Internet-of-Things (IoT) networks requires minimizing the energy consumption while achieving the capacity requirements especially for high density deployment. The Multi-Packet Reception (MPR) systems can potentially increase the capacity of devices due to the capability of decoding multiple transmitted packets at the receiver. However, the aggregate interference in such scenarios can lead to unfair distribution of the resources and eventually waste of energy. Therefore, this work provides an analytical characterization of the trade-off between capacity and energy consumption while regulating the channel access of multiple transmitters to a single-MPR receiver. The theoretical modeling considers different densities of spatially distributed nodes and their channel propagation conditions, in addition to different capture sensitivity thresholds at the receiver. The model is validated through simulation and it is shown to be an effective tool to identify the optimal channel access probability that maximizes the capacity per energy consumption.
Bi-Objective Power Optimization of Radio Stripe Uplink Communications
Publication . Conceição, Filipe; Gomes, Marco; Silva, Vitor; Dinis, Rui; Antunes, Carlos Henggeler; DEE - Departamento de Engenharia Electrotécnica e de Computadores; MDPI - Multidisciplinary Digital Publishing Institute
The radio stripe (RS) system is a practical implementation of cell-free mMIMO, in which a set of multi-antenna access points (APs) serves at the same time-frequency resources the user equipment (UE) in the network. The APs are sequentially connected in a stripe, sharing the same fronthaul link to the central processing unit. This work considers an uplink power optimization problem that aims to enhance the network spectral efficiency (SE) by considering two metrics—the max–min fairness and the max–sum rate. We employ a meta-heuristic based on the differential evolution algorithm to solve the bi-objective optimization problem. The SE performances of the full power along with the single-objective and multiple-objective scenarios are analyzed and compared for the optimal sequential linear processing detection scheme. The bi-objective approach is able to unveil the trade-offs to identify solution balancing the SE distribution resulting from the optimization of the max–min fairness and the max–sum rate objective functions.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDB/50008/2020