Dynamic Time-domain Duplexing for Self-backhauled Millimeter Wave Cellular Networks

Millimeter wave (mmW) bands between 30 and 300 GHz have attracted considerable attention for next-generation cellular networks due to vast quantities of available spectrum and the possibility of very high-dimensional antenna ar-rays. However, a key issue in these systems is range: mmW signals are extremely vulnerable to shadowing and poor high-frequency propagation. Multi-hop relaying is therefore a natural technology for such systems to improve cell range and cell edge rates without the addition of wired access points. This paper studies the problem of scheduling for a simple infrastructure cellular relay system where communication between wired base stations and User Equipment follow a hierarchical tree structure through fixed relay nodes. Such a systems builds naturally on existing cellular mmW backhaul by adding mmW in the access links. A key feature of the proposed system is that TDD duplexing selections can be made on a link-by-link basis due to directional isolation from other links. We devise an efficient, greedy algorithm for centralized scheduling that maximizes network utility by jointly optimizing the duplexing schedule and resources allocation for dense, relay-enhanced OFDMA/TDD mmW networks. The proposed algorithm can dynamically adapt to loading, channel conditions and traffic demands. Significant throughput gains and improved resource utilization offered by our algorithm over the static, globally-synchronized TDD patterns are demonstrated through simulations based on empirically-derived channel models at 28 GHz.Comment: IEEE Workshop on Next Generation Backhaul/Fronthaul Networks - BackNets 201

In-situ measurement methodology for the assessment of 5G NR massive MIMO base station exposure at sub-6 GHz frequencies

As the roll-out of the fifth generation (5G) of mobile telecommunications is well underway, standardized methods to assess the human exposure to radiofrequency electromagnetic fields from 5G base station radios are needed in addition to existing numerical models and preliminary measurement studies. Challenges following the introduction of 5G New Radio (NR) include the utilization of new spectrum bands and the widespread use of technological advances such as Massive MIMO (Multiple-Input Multiple-Output) and beamforming. We propose a comprehensive and ready-to-use exposure assessment methodology for use with common spectrum analyzer equipment to measure or calculate in-situ the time-averaged instantaneous exposure and the theoretical maximum exposure from 5G NR base stations. Besides providing the correct method and equipment settings to capture the instantaneous exposure, the procedure also comprises a number of steps that involve the identification of the Synchronization Signal Block, which is the only 5G NR component that is transmitted periodically and at constant power, the assessment of the power density carried by its resources, and the subsequent extrapolation to the theoretical maximum exposure level. The procedure was validated on site for a 5G NR base station operating at 3.5 GHz, but it should be generally applicable to any 5G NR signal, i.e., as is for any sub-6 GHz signal and after adjustment of the proposed measurement settings for signals in the millimeter-wave range

Desenvolvimento em VHDL da camada física de um transmissor 4G

The LTE and LTE-Advanced technologies are standards to the fourth mobile generation, or 4G. The planned successor of this mobile generation is 5G, which will be based on 5G-New Radio (5G-NR) standard. The 5G technology is on an initial phase of deployment. One of its features that are essential in this initial phase is the support for 4G communications, because many of the mobile devices currently in use do not have support for 5G communications. This support is made possible if there is an implementation where 4G and 5G networks both coexist with each other. In the future, with the increasing usage of mobile devices with 5G support, there will be a gradual migration of 4G networks to 5G, releasing frequency spectrums currently reserved for 4G so that those can be occupied by 5G. The data transmissions in 4G require quite a lot of the processing capacity of all systems within the mobile network. For 5G, the data transmissions, in terms of traffic volume and speed, are larger than 4G transmissions, requiring new systems to be implemented, to allow the processing of larger quantities of data. Implementation in hardware of a 4G Uplink transmission chain, at the physical layer level PHY-Low, will allow the optimization of certain processes that a CPU could handle, reducing CPU usage and time spent on processing. The use of FPGAs makes this possible, as FPGAs can perform parallel tasks simultaneously and perform digital signal processing. The purpose of this dissertation is the modelling of a 4G LTE Uplink transmitter, at the physical layer level. Then, synthesizable VHDL code is generated from the modeled system, which can be eventually implemented in FPGAs. The modelling of the system is made in Simulink, a tool inside the MATLAB software, which allows for modelling, simulating and analyzing systems in a graphic environment and has applications in control systems and digital signal processing. The VHDL code is generated from HDL Coder, another tool in MATLAB software, generating synthesizable Verilog and VHDL code, from the MATLAB functions and Simulink models. The results obtained of processed data from the system are analyzed and validated, comparing the reference data generated from Wireless Waveform Generator toolbox in MATLAB.A tecnologia LTE e LTE-Advanced são standards da quarta geração de comunicações moveis atuais, ou 4G. Futuramente, o 5G marca a próxima geração de comunicações moveis, segundo o standard 5G-New Radio (5GNR). A tecnologia 5G encontra-se numa fase inicial de implementação, sendo que nessa fase uma das suas características fundamentais é o suporte para comunicações 4G, pois muitos dos dispositivos moveis usados atualmente não possuem suporte para comunicações 5G. Este suporte para 4G é tornado possível, se for feita uma implementação onde as redes 4G e 5G se encontrem em coexistência. No futuro, com o aumento do uso de dispositivos moveis com suporte para 5G, haverá uma migração gradual de redes 4G para 5G, libertando os espectros de frequências reservados atualmente para o 4G para serem ocupados pelo 5G. As transmissões de dados no 4G exigem bastante da capacidade de processamento de todos os sistemas da rede movel. Para o 5G, as transmissões de dados tem volumes de tráfego e velocidades maiores do que as transmissões de dados 4G, fazendo com que novos sistemas tenham de ser implementados para poder processar maiores quantidades de dados. A implementação em hardware da cadeia de transmissão 4G Uplink, ao nível da camada física PHY-Low, permitirá a otimização de certos processos que um CPU poderia lidar, diminuindo o uso do CPU e o tempo gasto em processamento. O uso de FPGAs torna isto possível, tendo em conta que podem realizar tarefas em paralelo, em modo simultâneo, e fazer processamento digital de sinal. O objetivo desta dissertação assenta na modelação de um transmissor 4G LTE Uplink, ao nível da camada física. Depois, é gerado código VHDL sintetizável a partir do sistema modelado, que eventualmente será implementada em FPGAs. A modelação do sistema é feito em Simulink, uma ferramenta no software do MATLAB, que permite modelar, simular e analisar sistemas num ambiente gráfico e tem aplicações para sistemas de controlo e processamento digital de sinal. O código VHDL é gerado a partir do HDL Coder, uma outra ferramenta no software do MATLAB, que gera Verilog e VHDL sintetizáveis, a partir de funções MATLAB e de modelos Simulink. Os resultados obtidos dos dados processados pelo sistema são analisados e validados, comparando com os dados de referência obtidos a partir da toolbox Wireless Waveform Generator do MATLAB.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Multicast broadcast services support in OFDMA-based WiMAX systems [Advances in mobile multimedia]

Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide'differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency

Control-data separation architecture for cellular radio access networks: a survey and outlook

Conventional cellular systems are designed to ensure ubiquitous coverage with an always present wireless channel irrespective of the spatial and temporal demand of service. This approach raises several problems due to the tight coupling between network and data access points, as well as the paradigm shift towards data-oriented services, heterogeneous deployments and network densification. A logical separation between control and data planes is seen as a promising solution that could overcome these issues, by providing data services under the umbrella of a coverage layer. This article presents a holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks. As a starting point, we discuss the fundamentals, concepts, and general structure of the CDSA. Then, we point out limitations of the conventional architecture in futuristic deployment scenarios. In addition, we present and critically discuss the work that has been done to investigate potential benefits of the CDSA, as well as its technical challenges and enabling technologies. Finally, an overview of standardisation proposals related to this research vision is provided

Uplink Sounding Reference Signal Coordination to Combat Pilot Contamination in 5G Massive MIMO

To guarantee the success of massive multiple-input multiple-output (MIMO), one of the main challenges to solve is the efficient management of pilot contamination. Allocation of fully orthogonal pilot sequences across the network would provide a solution to the problem, but the associated overhead would make this approach infeasible in practical systems. Ongoing fifth-generation (5G) standardisation activities are debating the amount of resources to be dedicated to the transmission of pilot sequences, focussing on uplink sounding reference signals (UL SRSs) design. In this paper, we extensively evaluate the performance of various UL SRS allocation strategies in practical deployments, shedding light on their strengths and weaknesses. Furthermore, we introduce a novel UL SRS fractional reuse (FR) scheme, denoted neighbour-aware FR (FR-NA). The proposed FR-NA generalizes the fixed reuse paradigm, and entails a tradeoff between i) aggressively sharing some UL SRS resources, and ii) protecting other UL SRS resources with the aim of relieving neighbouring BSs from pilot contamination. Said features result in a cell throughput improvement over both fixed reuse and state-of-the-art FR based on a cell-centric perspective