Performance Analysis of a 5G Transceiver Implementation for Remote Areas Scenarios

The fifth generation of mobile communication networks will support a large set of new services and applications. One important use case is the remote area coverage for broadband Internet access. This use case ha significant social and economic impact, since a considerable percentage of the global population living in low populated area does not have Internet access and the communication infrastructure in rural areas can be used to improve agribusiness productivity. The aim of this paper is to analyze the performance of a 5G for Remote Areas transceiver, implemented on field programmable gate array based hardware for real-time processing. This transceiver employs the latest digital communication techniques, such as generalized frequency division multiplexing waveform combined with 2 by 2 multiple-input multiple-output diversity scheme and polar channel coding. The performance of the prototype is evaluated regarding its out-of-band emissions and bit error rate under AWGN channel.Comment: Presented in 2018 European Conference on Networks and Communications (EuCNC),18-21 June, 2018, Ljubljana, Sloveni

5GNOW: Challenging the LTE Design Paradigms of Orthogonality and Synchronicity

LTE and LTE-Advanced have been optimized to deliver high bandwidth pipes to wireless users. The transport mechanisms have been tailored to maximize single cell performance by enforcing strict synchronism and orthogonality within a single cell and within a single contiguous frequency band. Various emerging trends reveal major shortcomings of those design criteria: 1) The fraction of machine-type-communications (MTC) is growing fast. Transmissions of this kind are suffering from the bulky procedures necessary to ensure strict synchronism. 2) Collaborative schemes have been introduced to boost capacity and coverage (CoMP), and wireless networks are becoming more and more heterogeneous following the non-uniform distribution of users. Tremendous efforts must be spent to collect the gains and to manage such systems under the premise of strict synchronism and orthogonality. 3) The advent of the Digital Agenda and the introduction of carrier aggregation are forcing the transmission systems to deal with fragmented spectrum. 5GNOW is an European research project supported by the European Commission within FP7 ICT Call 8. It will question the design targets of LTE and LTE-Advanced having these shortcomings in mind and the obedience to strict synchronism and orthogonality will be challenged. It will develop new PHY and MAC layer concepts being better suited to meet the upcoming needs with respect to service variety and heterogeneous transmission setups. Wireless transmission networks following the outcomes of 5GNOW will be better suited to meet the manifoldness of services, device classes and transmission setups present in envisioned future scenarios like smart cities. The integration of systems relying heavily on MTC into the communication network will be eased. The per-user experience will be more uniform and satisfying. To ensure this 5GNOW will contribute to upcoming 5G standardization.Comment: Submitted to Workshop on Mobile and Wireless Communication Systems for 2020 and beyond (at IEEE VTC 2013, Spring

Channel estimation techniques for filter bank multicarrier based transceivers for next generation of wireless networks

A dissertation submitted to Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering (Electrical and Information Engineering), August 2017The fourth generation (4G) of wireless communication system is designed based on the principles of cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) where the cyclic prefix (CP) is used to combat inter-symbol interference (ISI) and inter-carrier interference (ICI) in order to achieve higher data rates in comparison to the previous generations of wireless networks. Various filter bank multicarrier systems have been considered as potential waveforms for the fast emerging next generation (xG) of wireless networks (especially the fifth generation (5G) networks). Some examples of the considered waveforms are orthogonal frequency division multiplexing with offset quadrature amplitude modulation based filter bank, universal filtered multicarrier (UFMC), bi-orthogonal frequency division multiplexing (BFDM) and generalized frequency division multiplexing (GFDM). In perfect reconstruction (PR) or near perfect reconstruction (NPR) filter bank designs, these aforementioned FBMC waveforms adopt the use of well-designed prototype filters (which are used for designing the synthesis and analysis filter banks) so as to either replace or minimize the CP usage of the 4G networks in order to provide higher spectral efficiencies for the overall increment in data rates. The accurate designing of the FIR low-pass prototype filter in NPR filter banks results in minimal signal distortions thus, making the analysis filter bank a time-reversed version of the corresponding synthesis filter bank. However, in non-perfect reconstruction (Non-PR) the analysis filter bank is not directly a time-reversed version of the corresponding synthesis filter bank as the prototype filter impulse response for this system is formulated (in this dissertation) by the introduction of randomly generated errors. Hence, aliasing and amplitude distortions are more prominent for Non-PR. Channel estimation (CE) is used to predict the behaviour of the frequency selective channel and is usually adopted to ensure excellent reconstruction of the transmitted symbols. These techniques can be broadly classified as pilot based, semi-blind and blind channel estimation schemes. In this dissertation, two linear pilot based CE techniques namely the least square (LS) and linear minimum mean square error (LMMSE), and three adaptive channel estimation schemes namely least mean square (LMS), normalized least mean square (NLMS) and recursive least square (RLS) are presented, analyzed and documented. These are implemented while exploiting the near orthogonality properties of offset quadrature amplitude modulation (OQAM) to mitigate the effects of interference for two filter bank waveforms (i.e. OFDM/OQAM and GFDM/OQAM) for the next generation of wireless networks assuming conditions of both NPR and Non-PR in slow and fast frequency selective Rayleigh fading channel. Results obtained from the computer simulations carried out showed that the channel estimation schemes performed better in an NPR filter bank system as compared with Non-PR filter banks. The low performance of Non-PR system is due to the amplitude distortion and aliasing introduced from the random errors generated in the system that is used to design its prototype filters. It can be concluded that RLS, NLMS, LMS, LMMSE and LS channel estimation schemes offered the best normalized mean square error (NMSE) and bit error rate (BER) performances (in decreasing order) for both waveforms assuming both NPR and Non-PR filter banks. Keywords: Channel estimation, Filter bank, OFDM/OQAM, GFDM/OQAM, NPR, Non-PR, 5G, Frequency selective channel.CK201

Equalizador híbrido na banda das ondas milimétricas para sistemas GFDM

Wireless communication using very-large multiple-input multiple-output (MIMO) antennas has been regarded as one of the enabling technologies for the future mobile communication. It refers to the idea of equipping cellular base stations (BSs) with a very large number of antennas giving the possibility to focusing the transmitted signal energy into very short-range areas, which will provide huge improvements in the capacity, in addition to the spectral and energy efficiency. Concurrently, this demand for high data rates and capacity led to the necessity of exploiting the enormous amount of spectrum in the millimeter wave (mmWave) bands. However, the combination of millimeter-wave communications arrays with a massive number of antennas has the potential to dramatically enhance the features of wireless communication. This combination implies high cost and power consumption in the conventional full digital architecture, where each RF chain is dedicated to one antenna. The solution is the use of a hybrid architecture, where a small number of RF chains are connected to a large number of antennas through a network of phase shifters. On the other hand, another important factor that affect the transmission quality is the modulation technique, which plays an important role in the performance of the transmission process, for instance, GFDM is a flexible non-orthogonal multicarrier modulation concept, that introduces additional degrees of freedom when compared to other multicarrier techniques. This flexibility makes GFDM a promising solution for the future cellular generations, because it can achieve different requirements, such as higher spectrum efficiency, better control of out-of-band (OOB) emissions, as well as achieving low peak to average power ratio (PAPR). In this work, we present an analog-digital transmitter and receiver structures. Considering a GFDM modulation technique to be implemented in the digital part, while in the analog part, we propose a full connected hybrid multiuser linear equalizer, combined with low complexity hybrid precoder for wideband millimeter-wave massive MIMO systems. The hybrid equalizer is optimized by minimizing the mean square error between the hybrid approach and the full digital counterpart. The results show that the performance of the proposed hybrid scheme is very close to the full digital counterpart and the gap reduces as the number of RF chains increases.O uso de um número elevado de antenas, também designado por MIMO massivo, tem sido considerada uma das tecnologias mais promissoras para os futuros sistemas de comunicação sem fios. Esta tecnologia, refere-se à ideia de equipar as estações base (BSs) com um número muito grande de antenas, dando a possibilidade de focar a energia do sinal transmitido em áreas de alcance muito restritas, o que proporcionará grandes melhorias na capacidade, além das espectrais e eficiência energética. Simultaneamente, a exigência por taxas de dados elevadas e capacidade levou à necessidade de explorar uma enorme quantidade de espectro nas bandas de ondas milimétricas (mmWave). A combinação de comunicação na banda das ondas milimétricas com terminais equipados com um grande número de antenas tem o potencial de melhorar drasticamente os recursos da comunicação sem fios. Considerando no entanto uma arquitetura digital, usada em sistemas MIMO convencionais, em que cada cadeia de RF é dedicada a uma antena, implica um custo e um consumo de energia elevados. A solução é o uso de uma arquitetura híbrida, na qual um pequeno número de cadeias de RF é conectado a um grande número de antenas através de um conjunto de deslocadores de fase. Outro fator importante que afeta a qualidade da transmissão é a técnica de modulação usada, que desempenha um papel importante no desempenho do processo de transmissão. O GFDM é um conceito de modulação de portadora múltipla, não ortogonal e flexível, que introduz graus de liberdade adicionais, quando comparado a outras técnicas de portadora múltipla, como o OFDM. Essa flexibilidade faz do GFDM uma solução promissora para as futuras gerações celulares, pois pode atender a diferentes requisitos, como maior eficiência de espectro, melhor controle das emissões fora de banda (OOB), além de atingir baixo rácio de potência média / pico ( PAPR). Neste trabalho, é assumido uma arquitetura hibrida no transmissor e recetor. Considera-se uma técnica de modulação GFDM a ser implementada na parte digital, enquanto na parte analógica, é proposto um equalizador linear híbrido multiutilizador totalmente conectado, i.e., cada cadeia RF está ligada a todas as antenas, combinado com um pré-codificador híbrido, de baixa complexidade para sistemas MIMO massivo de banda larga. O equalizador híbrido é otimizado, minimizando o erro quadrático médio entre a abordagem híbrida e a contraparte totalmente digital. Os resultados mostram que o desempenho do esquema híbrido proposto está muito próximo do equivalente digital, à medida que o número de cadeias de RF aumenta.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Review of Recent Trends

This work was partially supported by the European Regional Development Fund (FEDER), through the Regional Operational Programme of Centre (CENTRO 2020) of the Portugal 2020 framework, through projects SOCA (CENTRO-01-0145-FEDER-000010) and ORCIP (CENTRO-01-0145-FEDER-022141). Fernando P. Guiomar acknowledges a fellowship from “la Caixa” Foundation (ID100010434), code LCF/BQ/PR20/11770015. Houda Harkat acknowledges the financial support of the Programmatic Financing of the CTS R&D Unit (UIDP/00066/2020).MIMO-OFDM is a key technology and a strong candidate for 5G telecommunication systems. In the literature, there is no convenient survey study that rounds up all the necessary points to be investigated concerning such systems. The current deeper review paper inspects and interprets the state of the art and addresses several research axes related to MIMO-OFDM systems. Two topics have received special attention: MIMO waveforms and MIMO-OFDM channel estimation. The existing MIMO hardware and software innovations, in addition to the MIMO-OFDM equalization techniques, are discussed concisely. In the literature, only a few authors have discussed the MIMO channel estimation and modeling problems for a variety of MIMO systems. However, to the best of our knowledge, there has been until now no review paper specifically discussing the recent works concerning channel estimation and the equalization process for MIMO-OFDM systems. Hence, the current work focuses on analyzing the recently used algorithms in the field, which could be a rich reference for researchers. Moreover, some research perspectives are identified.publishersversionpublishe