FE - DEM | Dissertações de Mestrado e Teses de Doutoramento
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- Cellular Planning and Optimization for 4G and 5G Mobile NetworksPublication . Ramos, Anderson Rocha; Velez, Fernando José da SilvaCellular planning and optimization of mobile heterogeneous networks has been a topic of study for several decades with a diversity of resources, such as analytical formulations and simulation software being employed to characterize different scenarios with the aim of improving system capacity. Furthermore, the world has now witnessed the birth of the first commercial 5G New Radio networks with a technology that was developed to ensure the delivery of much higher data rates with comparably lower levels of latency. In the challenging scenarios of 4G and beyond, Carrier Aggregation has been proposed as a resource to allow enhancements in coverage and capacity. Another key element to ensure the success of 4G and 5G networks is the deployment of Small Cells to offload Macrocells. In this context, this MSc dissertation explores Small Cells deployment via an analytical formulation, where metrics such as Carrier plus Noise Interference Ratio, and physical and supported throughput are computed to evaluate the system´s capacity under different configurations regarding interferers positioning in a scenario where Spectrum Sharing is explored as a solution to deal with the scarcity of spectrum. One also uses the results of this analyses to propose a cost/revenue optimization where deployment costs are estimated and evaluated as well as the revenue considering the supported throughput obtained for the three frequency bands studied, i.e., 2.6 GHz, 3.5 GHz and 5.62 GHz. Results show that, for a project life time of 5 years, and prices for the traffic of order of 5€ per 1 GB, the system is profitable for all three frequency bands, for distances up to 1335 m. Carrier Aggregation is also investigated, in a scenario where the LTE-Sim packet level simulator is used to evaluate the use of this approach while considering the use of two frequency bands i.e., 2.6 GHz and 800 MHz to perform the aggregation with the scheduling of packets being performed via an integrated common radio resource management used to compute Packet Loss Ratio, delay and goodput under different scenarios of number of users and cell radius. Results of this analysis have been compared to a scenario without Carrier Aggregation and it has been demonstrated that CA is able to enhance capacity by reducing the levels of Packet Loss Ratio and delay, which in turn increases the achievable goodput.
- Efficient Management of Flexible Functional Splits in 5G Second Phase NetworksPublication . Pires, Ivan Micael Vicente; Velez, Fernando José da SilvaThe fifth mobile network generation (5G), which offers better data speeds, reduced latency, and a huge number of network connections, promises to improve the performance of the cellular network in practically every way available. A portion of the network operations are deployed in a centralized unit in the 5G radio access network (RAN) partially centralized design. By centralizing these functions, operational expenses are decreased and coordinating strategies are made possible. To link centralized units (CU) and distributed units (DU), and the DU to remote radio units (RRU), both the midhaul and fronthaul networks must have higher capacity. The necessary fronthaul capacity is also influenced by the fluctuating instantaneous user traffic. Consequently, the 5G RAN must be able to dynamically change its centralization level to the user traffic to maximize its performance. To try to relieve this fronthaul capacity it has been considered a more flexible distribution between the base band unit (BBU) (or CU and DU if enhanced common public radio interface (eCPRI) is considered) and the RRU. It may be challenging to provide high-speed data services in crowded areas, particularly when there is imperfect coverage or significant interference. Because of this, the macrocell deployment is insufficient. This problem for outdoor users could be resolved by the introduction of low-power nodes with a limited coverage area. In this context, this MSc dissertation explores, in an urban micro cell scenario model A (UMi_A) for three frequency bands (2.6 GHz, 3.5 GHz, and 5.62 GHz), the highest data rate achievable when a numerology zero is used. For this, it was necessary the implementation of the UMi_A in the 5G-air-simulator. Allowing the determination of the saturation level using the results for the packet loss ratio (PLR=2%). By assuming Open RAN (O-RAN) and functional splitting, the performance of two schedulers in terms of quality-of-service (QoS) were also studied. The QoS-aware modified largest weighted delay first (M-LWDF) scheduler and the QoS-unaware proportional fair (PF) scheduler. PLR was evaluated for both schedulers, whilst analyzing the impact of break point distance while changing the frequency band. The costs, revenues, profit in percentage terms, and other metrics were also estimated for the PF and M-LWDF schedulers when used video (VID) and video plus best effort (VID+BE), with or without consideration of the functional splits 7.2 and 6, for the three frequency bands. One concluded that the profit in percentage terms with functional split option 7.2 applied is always slightly higher than with functional split option 6. It reaches a maximum profit of 366.92% in the case of the M-LWDF scheduler, and 305.51% in the case of the PF scheduler, at a cell radius of 0.4 km for the 2.6 GHz frequency band, considering a price of the traffic of 0.0002 €/min.
- Measurement-Based Characterization of the 5GPublication . Francisco, Salomão Manuel; Velez, Fernando José da SilvaThe characterization of the wireless medium in indoor small cell networks is essential to obtain appropriate modelling of the propagation environment. This dissertation on ”MeasurementBased Characterization of the 5G New Radio Small Cell Propagation Environment” has been developed in an experimental environment. The underlying tasks are divided into three phases. The first phase took place in the laboratory of the Instituto de Telecomunicações – Covilhã, located in the Departamento de Engenharia Electromecânica of Universidade da Beira Interior. During this part of the research, spectrum measurements and the characterization of the S11 parameter (response in the first port for the signal incident in the first port) have been made experimentally through the printed circuit board antennas in the 2.6 GHz and 3.5 GHz frequency bands operating in the 2.625 GHz and 3.590 GHz center frequency, manufactured by us. The fabrication of the antennas was preceded by the simulation in the student version CST STUDIO software. In this phase, the spectrum measurements and the characterization of Smith Chart have been made to measure gain and impedance using the Rohde & Schwarz Vector Network Analyzer (VNA) from IT laboratory. Based on mathematical calculations and considerations on the conductivity and permeability of the environment, the antennas were built for use in indoor and outdoor environments. The developed antennas are characterized by their bandwidth and their radiation characteristics. The second phase took place in the three rooms adjacent to the laboratory, in which the srsLTE emulation software was applied to the 4G indoor scenario. The experimental setup includes three elements, namely a base station (BS or 4G eNodeB), which transmits the communication signal and which served as a signal source, a user equipment (UE), and an interfering eNodeB. The size of each room is 7.32 × 7.32 square meters. While room 1 is the room of interest, where theoretical and practical measurements took place, BSs that act as wireless interfering nodes are also separately considered either in room 2 or room 3. By varying the UE positions within room 1, it was possible to verify that the highest values of the received power occur close to the central BS. However, the received power does not decrease suddenly because of the reduced gain in the radiation pattern in the back part of the antenna. In addition, it was demonstrated that there is an effect of “wall loss”proven by the path loss increase between room 1 and room 2 (or between room 2 and 3). If we consider an attenuation for each wall of circa 7-9 dB the trend of the WINNER II at 2.625 GHz model for the interference coming across different walls is verified. Future work includes to investigate the 3.5 GHz frequency band. The third phase is being carried out at the facilities of the old aerodrome of Covilhã which, using a temporary license assigned to us by Instituto de Comunicações Português (ICP-ANACOM) as the two first phases. The aim of this phase is to investigate the two-slope behaviour in the UMi scenario. Very initial LTE-Advanced tests have been performed to verify the propagation of the two ray (with a reflection in the asphalt) from BS implemented with USRP B210 and srsLTE system by considering an urban cell with a length of 80 m and an interfering base station at 320 m, at 2500 - 2510 MHz (DL - Downlink) by now, mainly due to the current availability of a directional antenna in this specific band.
- Optimization of Small Cells Deployment and Frequency Assignment using Spectrum SharingPublication . Silva, Bruno Cruz da; Velez, Fernando José da Silva5G New Radio is an ai r-interface technology with the objective of improving performance, flex¬ibility [1], [2],[3] scalability and efficiency of current mobile networks. 5G NR is envisioned to support multipIe services and devices where the heterogeneous networks will be of such im¬portance with the densification of small cells, and different techniques will be used such as carrier aggregation, spectrum sharing or dual connectivity. This dissertation aims to explore the optimization of small cell networks using the spectrum sharing in the UHF, SHF and mil¬limeter wave bands for urban environments. ln the study, different scenarios and topologies have been considered, while frequencies of 2.6 GHz and 3.5 GHz have been considered for the UHFISHF bands, and 28, 38, 60 and 73 GHz for the millimeter wave bands. A linear topol¬ogy has been considered for the millimeter waves that contains a scenario with sharing and another without shared spectrum, while in the UHF and SHF bands a hexagonal topology has been considered, containing both a scenario without spectrum sharing and six spectrum sharing topologies, divided by its region in the cell, as Northeast, East, Southeast and Soutwest. Propa¬gation models are the Urban Micro LoS for UHFISHF, a two-slope model, and the modified Friis equation for the millimeter waves. Different reuse patterns have also been considered, i.e., k = 3 and k = 4. However, for the millimeter wave scenario only k = 3 has been considered. With the established scenario and the considered models, the performance parameters such as the CNIR, PHY throughput, supported throughput, average CNIRISINR have been obtained and discussed. ln the UHFISHF bands, by comparing the curves for the supported throughput and the average CNIR, we can observe that the trend of the values, i.e., the line shapes, are very similar. The 28 GHz frequency band has the highest supported throughput, reaching 45 Mbps. The supported throughput at the 38, 60 and 73 GHz is higher than the one for the UHFISHF bands for the shortest Rs. For longer coverage distances, the supported throughput is clearly higher for the UHF/SHF frequency bands (compared to the 38, 60 and 73 GHz frequency bands). LTE-Sim, a open source framework developed in the University of Bari [4], commonly known as an event-driven simulator written in C + + has been used for packet-level simulations. Results for the goodput, packet loss ratio and delay have been obtained. One scenario with only a small cell cluster, with one picocell and six co-channel pico cells, has been considered in the simu-lations. The goodput and packet loss ratio achieved by simulation are complementary to each other (where achieved goodput is slightly higher at 2.6 GHz, compared to the 3.5 GHz frequency band). By comparing the analytical and simulation results for the supported throughoutigood¬put (without sharing) there are differences, as analytical results do not consider packet errors, and for a number of users higher than 16 -18, the PLR is too high even for distances longer than 100 -150 m, while for 16 or less users the PLR is only high for coverage distances up to circa 100 m. These differences between analytical and simulation results can be mainly explained by the fact that the number of users are not considered in the analytical formulation (saturation conditions are assumed instead), and also because of the high value for the PLR. The maximum delay is 55 ms. Hence, e.g., for gaming applications, latency will be adequate.
- Optimization of Spectrum Management in Massive Array Antenna Systems with MIMOPublication . Andrade, Rooderson Martines de; Velez, Fernando José da SilvaFifth generation (5G), is being considered as a revolutionary technology in the telecommunication domain whose the challenges are mainly to achieve signal quality and great ability to work with free spectrum in the millimetre waves. Besides, other important innovations are the introduction of a more current architecture and the use of multiple antennas in transmission and reception. Digital communication using multiple input and multiple output (MIMO) wireless links has recently emerged as one of the most significant technical advances in modern communications. MIMO technology is able to offer a large increase in the capacity of these systems, without requiring a considerable increase in bandwidth or power required for transmission. This dissertation presents an overview of theoretical concepts of MIMO systems. With such a system a spatial diversity gain can be obtained by using space-time codes, which simultaneously exploit the spatial domain and the time domain. SISO, SIMO and MISO systems are differentiated by their channel capacity and their configuration in relation to the number of antennas in the transmitter/receiver. To verify the effectiveness of the MIMO systems a comparison between the capacity of SISO and MIMO systems has been performed using the Shannon’s principles. In the MIMO system some variations in the number of antennas arrays have been considered, and the superiority of transmission gains of the MIMO systems have been demonstrated. Combined with millimetre waves (mmWaves) technology, massive MIMO systems, where the number of antennas in the base station and the number of users are large, is a promising solution. SDR implementations have been performed considering a platform with Matlab code applied to MIMO 2x2 Radio and Universal Software Peripheral Radio (USRP). A detailed study was initially conducted to analyze the architecture of the USRP. Complex structures of MIMO systems can be simplified by using mathematical methods implemented in Matlab for the synchronization of the USRP in the receiver side. SISO transmission and reception techniques have been considered to refine the synchronization (with 16-QAM), thus facilitating the future implementation of the MIMO system. OpenAirInterface has been considered for 4G and 5G implementations of actual mobile radio communication systems. Together with the practical MIMO, this type of solution is the starting point for future hardware building blocks involving massive MIMO systems.