Wireless Power Transfer in Massive MIMO Aided HetNets with User Association

This paper explores the potential of wireless power transfer (WPT) in massive multiple input multiple output (MIMO) aided heterogeneous networks (HetNets), where massive MIMO is applied in the macrocells, and users aim to harvest as much energy as possible and reduce the uplink path loss for enhancing their information transfer. By addressing the impact of massive MIMO on the user association, we compare and analyze two user association schemes. We adopt the linear maximal ratio transmission beam-forming for massive MIMO power transfer to recharge users. By deriving new statistical properties, we obtain the exact and asymptotic expressions for the average harvested energy. Then we derive the average uplink achievable rate under the harvested energy constraint.Comment: 36 pages, 11 figures, to appear in IEEE Transactions on Communication

Uplink Interference Management in Massive MIMO Enabled Heterogeneous Cellular Networks

In this letter, we exploit the implementation of uplink power control and cell range extension for interference coordination in a two-tier massive multiple input multiple output (MIMO) enabled heterogeneous cellular network. Our results show that the uplink performance in the massive MIMO macrocells can be significantly improved through uplink power control in the small cells, while more uplink transmissions in the macrocells have mild adverse effect on the uplink performance of the small cells. In addition, the uplink performance of the massive MIMO macrocells can be improved by expanding the small cell range when dozens of users are served in the macrocells

User Association in 5G Networks: A Survey and an Outlook

26 pages; accepted to appear in IEEE Communications Surveys and Tutorial

Harmonized Cellular and Distributed Massive MIMO: Load Balancing and Scheduling

Multi-tier networks with large-array base stations (BSs) that are able to operate in the "massive MIMO" regime are envisioned to play a key role in meeting the exploding wireless traffic demands. Operated over small cells with reciprocity-based training, massive MIMO promises large spectral efficiencies per unit area with low overheads. Also, near-optimal user-BS association and resource allocation are possible in cellular massive MIMO HetNets using simple admission control mechanisms and rudimentary BS schedulers, since scheduled user rates can be predicted a priori with massive MIMO. Reciprocity-based training naturally enables coordinated multi-point transmission (CoMP), as each uplink pilot inherently trains antenna arrays at all nearby BSs. In this paper we consider a distributed-MIMO form of CoMP, which improves cell-edge performance without requiring channel state information exchanges among cooperating BSs. We present methods for harmonized operation of distributed and cellular massive MIMO in the downlink that optimize resource allocation at a coarser time scale across the network. We also present scheduling policies at the resource block level which target approaching the optimal allocations. Simulations reveal that the proposed methods can significantly outperform the network-optimized cellular-only massive MIMO operation (i.e., operation without CoMP), especially at the cell edge

Evolution Toward 5G Mobile Networks - A Survey on Enabling Technologies

In this paper, an extensive review has been carried out on the trends of existing as well as proposed potential enabling technologies that are expected to shape the fifth generation (5G) mobile wireless networks. Based on the classification of the trends, we develop a 5G network architectural evolution framework that comprises three evolutionary directions, namely, (1) radio access network node and performance enabler, (2) network control programming platform, and (3) backhaul network platform and synchronization. In (1), we discuss node classification including low power nodes in emerging machine-type communications, and network capacity enablers, e.g., millimeter wave communications and massive multiple-input multiple-output. In (2), both logically distributed cell/device-centric platforms, and logically centralized conventional/wireless software defined networking control programming approaches are discussed. In (3), backhaul networks and network synchronization are discussed. A comparative analysis for each direction as well as future evolutionary directions and challenges toward 5G networks are discussed. This survey will be helpful for further research exploitations and network operators for a smooth evolution of their existing networks toward 5G networks

Fast converging robust beamforming for downlink massive MIMO systems in heterogenous networks

Massive multiple-input multiple-output (MIMO) is an emerging technology, which is an enabler for future broadband wireless networks that support high speed connection of densely populated areas. Application of massive MIMO at the macrocell base stations in heterogeneous networks (HetNets) offers an increase in throughput without increasing the bandwidth, but with reduced power consumption. This research investigated the optimisation problem of signal-to-interference-plus-noise ratio (SINR) balancing for macrocell users in a typical HetNet scenario with massive MIMO at the base station. The aim was to present an efficient beamforming solution that would enhance inter-tier interference mitigation in heterogeneous networks. The system model considered the case of perfect channel state information (CSI) acquisition at the transmitter, as well as the case of imperfect CSI at the transmitter. A fast converging beamforming solution, which is applicable to both channel models, is presented. The proposed beamforming solution method applies the matrix stuffing technique and the alternative direction method of multipliers, in a two-stage fashion, to give a modestly accurate and efficient solution. In the first stage, the original optimisation problem is transformed into standard second-order conic program (SOCP) form using the Smith form reformulation and applying the matrix stuffing technique for fast transformation. The second stage uses the alternative direction method of multipliers to solve the SOCP-based optimisation problem. Simulations to evaluate the SINR performance of the proposed solution method were carried out with supporting software-based simulations using relevant MATLAB toolboxes. The simulation results of a typical single cell in a HetNet show that the proposed solution gives performance with modest accuracy, while converging in an efficient manner, compared to optimal solutions achieved by state-of-the-art modelling languages and interior-point solvers. This is particularly for cases when the number of antennas at the base station increases to large values, for both models of perfect CSI and imperfect CSI. This makes the solution method attractive for practical implementation in heterogeneous networks with large scale antenna arrays at the macrocell base station.Dissertation (MEng)--University of Pretoria, 2018.Electrical, Electronic and Computer EngineeringMEngUnrestricte

Implementação e avaliação no system generator de um sistema cooperativo para os futuros sistemas 5G

With the arrival of 5G it is expected the proliferation of services in the different fields such as healthcare, utility applications, industrial automation, 4K streaming, that the former networks can not provide. Additionally, the total number of wireless communication devices will escalate in such a manner that the already scarce available frequency bandwidth won’t be enough to pack the intended objectives. Cisco’s Annual Internet Report from 2018 predicts that by 2023 there will be nearly 30 billion devices capable of wireless communication. Due to the exponential expiation of both services and devices, the challenges upon both network data capacity and efficient radio resourse use will be greater than ever, thus the urgency for solutions is grand. Both the capacity for wireless communications and spectral efficiency are related to cell size and its users proximity to the access point. Thus, shortening the distance between the transmitter and the receiver improves both aspects of the network. This concept is what motivates the implementation of heterogeneous networks, HetNets, that are composed of many different small-cells, SCs, overlaid across the same coexisting area of a conventional macro-cell, shortening the distance between the cell users and its access point transceivers, granting a better coverage and higher data rates. However, the HetNets potential does not come without any challenges, as these networks suffer considerably from communication interference between cells. Although some interference management algorithms that allow coexistence between cells have been proposed in recent years, most of them were evaluated by software simulations and not implemented in real-time platforms. Therefore, this master thesis aims to give the first step on the implementation and evaluation of an interference mitigation technique in hardware. Specifically, it is assumed a downlink scenario composed by a macro-cell base station, a macro-cell primary user and a small cell user, with the aim of implementing an algorithm that eliminates the downlink interference that the base station may cause to the secondary users. The study was carried out using the System Generator DSP tool, which is a tool that generates code for hardware from schematics created in it. This tool also offers a wide range of blocks that help the creation, and fundamentally, the simulation and study of the system to be implemented, before being translated into hardware. The results obtained in this work are a faithful representation of the behavior of the implemented system, which can be used for a future application for FPGA.Com a chegada do 5G, espera-se a proliferação de serviços nas mais diversas áreas tal como assistência médica, automação industrial, transmissão em 4k, que não eram possíveis nas redes das gerações anteriores. Além deste fenómeno, o número total de dispositivos capazes de conexões wireless aumentará de tal maneira que a escassa largura de banda disponível não será suficiente para abranger os objetivos pretendidos. O Relatório Anual de 2018 sobre a Internet da Cisco prevê que até 2023 haverá quase 30 bilhões de dispositivos capazes de comunicação sem fio. Devido ao aumento exponencial de serviços e dispositivos, os desafios sobre a capacidade de dados da rede e o udo eficiente dos recursos de rádio serão maiores que nunca. Por estes motivos, a necessidade de soluções para estas lacunas é enorme. Tanto a capacidade da rede e o uso eficiente do espectro de frequências estão relacionados ao tamanho da célula e à proximidade dos usuários com o ponto de acesso da célula. Ao encurtar a distância entre o transmissor e o recetor ocorre um melhoramento destes dois aspetos da rede. Este é o principal conceito na implementação de redes heterogéneas, HetNets, que são compostas por diversas células pequenas que coexistem na área de uma macro célula convencional, diminuído a distância entre os utilizadores da célula e os pontos de acesso, garantindo uma melhor cobertura e taxa de dados mais elevadas. No entanto, o potencial das HatNets não vem sem nenhum custo, pois estas redes sofrem consideravelmente de interferência entre as células. Embora nos últimos anos foram propostos alguns algoritmos que permitem a coexistência das células, a maioria destes foi só testado em simulações de software e não em plataformas em tempo real. Por esse motivo, esta dissertação de mestrado visa dar o primeiro passo na implementação e a avaliação de uma técnica de mitigação de interferência em hardware. Mais especificamente no cenário de downlink entre uma estação base de uma macro célula, um utilizador primário da macro célula e um utilizador secundário de uma célula pequena, com o principal objetivo de cancelar a interferência que a estação base possa fazer ao utilizador secundário. O estudo foi realizado utilizando a ferramenta System Generator DSP, que é uma ferramenta que gera código para hardware a partir de esquemáticos criados na mesma. Esta ferramenta também oferece uma vasta gama de blocos que ajudam a criação, e fundamentalmente, a simulação e o estudo do sistema a implementar antes de ser traduzido para hardware. Os resultados obtidos neste trabalho são uma fiel representação do comportamento do sistema implementado. O quais podem ser utilizados para uma futura aplicação para FPGA.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

User Association and Enabling Technologies in Next Generation 5G Ultra-Dense Networks – A Review

Embedding small cells and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to traditional macro only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we review various techniques for user association and interference mitigation which are required to meet increased data demand in next generation 5G ultra-dense networ

Performance Evaluation and Enhancement in 5G Networks : A Stochastic Geometry Approach

PhDThe deployment of heterogeneous networks (HetNets), in which low power nodes (LPNs) and high power nodes (HPNs) coexist, has become a promising solution for extending coverage and increasing capacity in wireless networks. Meanwhile, several advanced technologies such as massive multi-input multi-output (MIMO), cloud radio access networks (C-RAN) and device-to-device (D2D) communications have been proposed as competent candidates for supporting the next generation (5G) network. Since single technology cannot solely achieve the envisioned 5G requirements, the e ect of integrating multiple technologies in one system is worth to be investigated. In this thesis, a thoroughly theoretical analysis is conducted to evaluate the network performance in di erent scenarios, where two or more 5G techniques are employed. First, the downlink performance of massive MIMO enabled HetNets is fully evaluated. The exact and asymptotic expressions for the probability of a user being associated with a macro cell or a small cell are presented. The analytical expressions for the spectrum e ciency (SE) and energy e ciency (EE) in the K-tier network are also derived. The analysis reveals that the implementation of massive MIMO in the macro cell can considerably improve the network performance and decrease the demands for small cells in HetNets, which simpli es the network deployment. Then, the downlink performance of a massive MIMO enabled heterogeneous C-RAN is investigated. The exact expressions for the SE and EE of the remote radio heads (RRHs) tier and a tractable approximation approach for evaluating the SE and EE of the macrocell tier are obtained. Numerical results collaborate the analysis and prove that massive MIMO with dense deployment of RRHs can signi cantly enhance the performance of heterogeneous C-RAN theoretically. Next, the uplink performance of massive MIMO enabled HetNets is exploited with interference management via derived SE and EE expressions. The numerical results show that the uplink performance in the massive MIMO macrocells can be signi cantly improved through uplink power control in the small cells, while more uplink transmissions in the macrocells have mild adverse e ect on the uplink performance of the small cells. In addition, the SE and EE of the massive MIMO macrocells with heavier load can be improved by expanding the small cell range. Lastly, the uplink performance of the D2D underlaid massive MIMO network is investigated and a novel D2D power control scheme is proposed. The average uplink achievable SE and EE expressions for the cellular and D2D are derived and results demonstrate that the proposed power control can e ciently mitigate the interference from the D2D. Moreover, the D2D scale properties are obtained, which provide the su cient conditions for achieving the anticipated SE. The results demonstrate that there exists the optimal D2D density for maximizing the area SE of D2D tier. In addition, the achievable EE of a cellular user can be comparable to that of a D2D user. Stochastic geometry is applied to model all of the systems mentioned above. Monte Carlo simulations are also developed and conducted to validate the derived expressions and the theoretical analysis