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Generalized LUI Propagation Model for UAVs Communications Using Terrestrial Cellular Networks

Publication . Tavares, Tiago; Sebastião, Pedro; Souto, N.; Velez, Fernando J.; Cercas, Francisco; Ribeiro, Marco; Correia, Americo

This work proposes an empirical propagation model to obtain the path loss, and therefore determine the average received power, of a signal for a specific outdoor urban scenario with UAVs. The proposed 3D propagation model for terrestrial cellular networks generalizes the LUI model and is valid in the frequency ranges from GSM, UMTS and LTE technologies. We report experimental work in 3D space, considering the height, the antennas base station tilt, sectorization, angle and distances profile. The experimental work included in this study appropriately agrees with the proposed theoretical model; hence, the proposed model is adequate for cellular planning tools.

2015-09Conference object

Open access

Extending the LTE-Sim Simulator with Multi-Band Scheduling Algorithms for Carrier Aggregation in LTE-Advanced Scenarios

Publication . Robalo, Daniel; Velez, Fernando J.; Paulo, Rui R.; Piro, Giuseppe

Carrier Aggregation (CA) has been proposed by 3GPP LTE-Advanced to meet or even exceed IMT-Advanced systems enhanced peak data rates requirements. In its rationale, multiple Component Carriers (CC) can be flexibly aggregated so that user equipment can access a total bandwidth of up to 100 MHz. As each CC has the same structure as the one from LTE R8, CA does not require notable changes in the LTE physical layer structure. Nevertheless, the way radio resources are allocated to mobile users in CA scenarios is still an hot research topic and the availability of an open source tool modelling such kind of feature is highly demanded in both academia and industry contexts. The present contribution is three-folded. First, it presents an open source and freeware extension of the well-known LTE-Sim simulator, which implements CA functionalities. Second, it also proposes an implementation of multi-band scheduling strategies able to optimally distribute radio resource among mobile users in the presence of multiple CCs and strict Quality of Service (QoS) constraints. Third, computer simulations have been also carried out to demonstrate the effectiveness of the aforementioned contributions. In particular, simulation results show the capacity improvements achieved by the proposed Enhanced Multi Scheduler against systems without CA, considering values of the bandwidth per component carrier of 5 and 20 MHz, in terms of average cell packet loss, delay, goodput and spectral efficiency.

2015-05Conference object

Open access

Wireless Sensor and Networking Technologies for Swarms of Aquatic Surface Drones

Publication . Velez, Fernando J.; Nadziejko, Aleksandra; Christensen, Anders Lyhne; Oliveira, Sancho; Rodrigues, Tiago; Costa, Vasco; Duarte, Miguel; Silva, Fernando; Gomes, Jorge

In this paper, we discuss wireless sensor and networking technologies for swarms of inexpensive aquatic surface drones in the context of the HANCAD project. The goal is to enable the swarm to perform maritime tasks such as sea-border patrolling and environmental monitoring, while keeping the cost of each drone low. Communication between drones is essential for the success of the project. Preliminary experiments show that XBee modules are promising for energy efficient multi-hop drone-to-drone communication.

2015-09Conference object

Open access

LTE-Advanced Radio and Network Optimization: Basic Coverage and Interference Constraints

Publication . Velez, Fernando J.; Sousa, Sofia; Acevedo Flores, Jessica; Robalo, Daniel; Mihovska, Albena; Prasad, Ramjee

In cellular optimization, the UL and DL the values from carrier-to-noise-plus-interference ratio (CNIR) from/at the mobile station are very important parameters. From a detailed analysis of its variation with the coverage and reuse distances for different values of the Channel Quality Indicator (CQI) and given ITU-R propagation models, an evaluation of the possible range for the reuse factor of LTE-A is performed for the DL. By considering CQI and reference CNIR requirements recommended by 3GPP, DL peak bit rates along with the Transport Block Size assumed for single stream and bandwidths of 10 and 20 MHz, PHY and supported throughputs are analysed. HetNets with Carrier Aggregation are considered, where macro cells operating at 800 MHz provide coverage and small cells (SCs) operating at 2.6 GHz provide throughput enhancement at hotspots. A clear decrease is shown for the supported throughput for the longest coverage distances in NLoS propagation conditions. In the given range of coverage distances, the same maximum value occurs for the supported throughput for K=3 and 7, both for macro and SCs.

2015-12Conference object

Open access

Basic limits for LTE-Advanced radio and HetNet optimization in the outdoor-to-indoor scenario

Publication . Velez, Fernando J.; Sousa, Sofia; Mihovska, Albena; Prasad, Ramjee

The unplanned deployment of small cells is leading to high levels of intra- and inter-tier interference. An insight on how to manage the interference is vital to reach a significant capacity improvement through ultra-dense networks. This paper considers heterogeneous networks with carrier aggregation, where the macro cells operate at 800 MHz to provide coverage and the small cells operate at 2.6 GHz to provide throughput enhancement at hotspots, including an outdoor-to-indoor scenario. We analyze in detail the values of the carrier-to-noise-plus-interference ratio (CNIR) from/at the user equipment (UE) for bandwidths of 10 and 20 MHz. A rapid decay is observed in the throughput for the small cells at a distance <; 300m. Broader bandwidths allow for doubling the capacity only for R>dBP/rcc. For R>250m, the capacity is similar for reuse pattern, K=3 and 7, showing no advantages for higher K. A clear decrease of the supported throughput is verified for the highest coverage distances in non-line-of-sight propagation conditions. Besides, one concludes that outdoor-to-indoor coverage corresponds to slightly worst coverage with less interference.

2016-06Conference object

Open access