54 research outputs found
A fully integrated 24-GHz phased-array transmitter in CMOS
This paper presents the first fully integrated 24-GHz phased-array transmitter designed using 0.18-/spl mu/m CMOS transistors. The four-element array includes four on-chip CMOS power amplifiers, with outputs matched to 50 /spl Omega/, that are each capable of generating up to 14.5 dBm of output power at 24 GHz. The heterodyne transmitter has a two-step quadrature up-conversion architecture with local oscillator (LO) frequencies of 4.8 and 19.2 GHz, which are generated by an on-chip frequency synthesizer. Four-bit LO path phase shifting is implemented in each element at 19.2 GHz, and the transmitter achieves a peak-to-null ratio of 23 dB with raw beam-steering resolution of 7/spl deg/ for radiation normal to the array. The transmitter can support data rates of 500 Mb/s on each channel (with BPSK modulation) and occupies 6.8 mm /spl times/ 2.1 mm of die area
Optimization of Spectrum Management in Massive Array Antenna Systems with MIMO
Fifth 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.A quinta geração (5G) está sendo considerada uma tecnologia revolucionária no setor de telecomunicações,
cujos desafios são principalmente a obtenção de qualidade de sinal e grande capacidade
de trabalhar com espectro livre nas ondas milimétricas. Além disso, outras inovações
importantes são a introdução de uma arquitetura mais atual e o uso de múltiplas antenas em
transmissão e recepção. A comunicação digital usando ligaçõe sem fio de múltiplas entradas e
mĂşltiplas saĂdas (MIMO) emergiu recentemente como um dos avanços tĂ©cnicos mais significativos
nas comunicações modernas. A tecnologia MIMO é capaz de oferecer um elevado aumento na
capacidade, sem exigir um aumento considerável na largura de banda ou potência transmitida.
Esta dissertação apresenta uma visão geral dos conceitos teóricos dos sistemas MIMO. Com esses
sistemas, um ganho de diversidade espacial pode ser obtido utilizando códigos espaço-tempo
reais. Os sistemas SISO, SIMO e MISO sĂŁo diferenciados pela capacidade de seus canais e a sua
configuração em relação ao número de antenas no emissor/receptor. Para verificar a eficiência
dos sistemas MIMO, realizou-se uma comparação entre a capacidade dos sistemas SISO e MIMO
utilizado os princĂpios de Shannon. Nos sistemas MIMO condecideraram-se algumas variações no
nĂşmero de agregados de antenas, e a superioridade dos ganhos de transmissĂŁo dos sistemas MIMO
foi demonstrada. Combinado com a tecnologia de ondas milimétricas (mmWaves), os sistemas
massivos MIMO, onde o número de antenas na estação base e o número de usuários são grandes,
são uma solução promissora.
As implementações do SDR foram realizadas considerando uma plataforma com código Matlab
aplicado aos rádios MIMO 2x2 e Universal Software Peripheral Radio (USRP). Um estudo detalhado
foi inicialmente conduzido para analisar a arquitetura da USRP. Estruturas complexas de sistemas
MIMO podem ser simplificadas usando métodos matemáticos implementados no Matlab para a
sincronização do USRP no lado do receptor. Consideraram-se técnicas de transmissão e recepção
SISO para refinar a sincronização (com 16-QAM), facilitando assim a implementação futura do
sistema MIMO . Considerou-se o OpenAirInterface para implementações 4G e 5G de sistemas
reais de comunicações móveis. Juntamente com o MIMO na pratica, este tipo de solução é
o ponto de partida para futuros blocos de construção de hardware envolvendo sistemas MIMO
massivos
Mobile and Wireless Communications
Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies
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Enhancement and performance analysis for 3D beamforming systems
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThis thesis is about the researching for 5th generation (5G) communication system, which focus on the improvement of 3D beamforming technology in the antenna array using in the Full Dimension Multiple-Input Multiple-Output (FD-MIMO) system and Millimeter-wave (mm-wave) system. When the 3D beamforming technology has been used in 5G communication system, the beam needs a weighting matrix to direct the beam to cover the UEs, but some compromises should be considered. If the narrow beams are used to transmit signals, then more energy is focused in the desired direction, but this has a restricted coverage area to a single or few User Equipments (UEs). If the BS covers multiple UEs, then multiple beams need to be steered towards more groups of UEs, but there is more interference between these beams from their side lobes when they are transmitted at same time. These challenges are waiting to be solved, which are about interference between each beam when the 3D beamforming technology is used. Therefore, there needs to be one method to decrease the generated interference between each beam through directing the side lobe beams and nulls to minimize interference in the 3D beamforming system. Simultaneously, energy needs to be directed towards the desired direction. If it has been decided that one beam should covera cluster of UEs, then there will be a range of received Signal to Interference plus Noise Ratio (SINR) depending on the location of the UEs relative to the direction of the main beam. If the beam is directed towards a group of UEs then there needs be a clustering method to cluster the UEs. In order to cover multiple UEs, an improved K-means clustering algorithm is used to cluster the multiple UEs into different groups, which is based on the cosine distance. Itcan decrease the number of beams when multiple UEs need be covered by multiple beams at same time. Moreover, a new method has been developed to calculate the weighting matrix for beamforming. It can adjust the values of weighting matrix according to the UEs’ location and direct the main beam in a desired direction whilst minimizing its side lobes in other undesired directions. Then the minimum side lobe beamforming system only needs to know the UEs’ location and can be used to estimate the Channel State Information (CSI) of UEs. Therefore, the scheme also shows lower complexity when compared to the beamforming methods with pre-coding. In order to test the improved K-means clustering algorithm and the new weighting method that can enhance the performance for 3D beamforming system, the two simulation systems are simulated to show the results such as 3D beamforming LTE system and mm-wave system
TĂ©cnicas de equalização iterativa para arquiteturas hĂbridas sub-conectadas na banda de ondas milimĂ©tricas
Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe millimeter wave communications and the use of a massive number of antennas are two promising technologies that being combined allow to achieve the multi Gb/s required by future 5G wireless systems. As this type of systems has a high number of antennas it is impossible to use a fully digital architecture, due to hardware limitations. Therefore, the design of signal processing techniques for hybrid analog-digital architectures is a requirement.
Depending on the structure of the analog part the hybrid analog-digital architectures may be fully connected or sub-connected. Although the fully connected hybrid architectures allow to connect all RF chains to any antenna element, they involve a high cost due to its structural and computational complexity. As such, the sub-connected hybrid architectures become more attractive, since either at the hardware level or from the computational point of view they are less demanding.
In this dissertation, we propose a hybrid iterative block multiuser equalizer for sub-connected millimeter wave massive MIMO systems. The user terminal transceiver has low-complexity and as such employ a pure analog random precoder, with a single RF chain. For the base station, a sub-connected hybrid analog-digital equalizer is designed to remove the multiuser interference.
The hybrid equalizer is optimized using the average bit-error-rate as a metric. Due to the coupling between the RF chains in the optimization problem the computation of the optimal solution is way too complex. To address this problem, we compute the analog part of the equalizer sequentially over the RF chains using a dictionary built from the array response vectors. The proposed sub-connected hybrid iterative multiuser equalizer is compared with a recently proposed fully connected hybrid analog-digital approach and with the fully digital architecture. The results show that the performance of the proposed scheme is close to the fully connected hybrid approach after just a few iterations.As comunicações na banda das ondas milimĂ©tricas e o uso massivo de antenas sĂŁo duas tecnologias promissoras que, sendo combinadas permitem alcançar elevadas taxas de transmissĂŁo, na ordem dos multi Gb/s, exigidas pelos futuros sistemas sem fios da 5G. Como estes sistemas possuem um nĂşmero elevado de antenas, torna-se impossĂvel o uso de uma arquitetura totalmente digital devido Ă s limitações de hardware. Desta forma, Ă© necessário projetar tĂ©cnicas de processamento de sinal para arquiteturas hĂbridas analĂłgico-digitais.
Dentro das arquiteturas hĂbridas, foram propostas duas formas de lidar com a parte analĂłgica, que sĂŁo, a forma totalmente conectada e a forma sub-conectada. Embora as arquiteturas hĂbridas totalmente conectadas permitam interligar todas as cadeias RF a qualquer elemento de antena, estas envolvem um elevado custo devido Ă sua complexidade estrutural e computacional. Assim sendo, as arquiteturas hĂbridas sub-conectadas tornam-se mais atraentes pois sĂŁo menos exigentes do ponto de vista computacional, bem como ao nĂvel do hardware.
Nesta dissertação, Ă© proposto um equalizador iterativo para um sistema com uma arquitetura hibrida sub-conectada, com mĂşltiplos utilizadores e um nĂşmero massivo de antenas a operar na banda das ondas milimĂ©tricas. Os terminais dos utilizadores tĂŞm baixa complexidade e utilizam prĂ©-codificadores aleatĂłrios analĂłgicos puros, cada um com uma Ăşnica cadeia RF. Para a estação base, projetou-se um equalizador hĂbrido analĂłgico-digital de arquitectura sub-conectada, para remover a interferĂŞncia multiutilizador.
O equalizador hĂbrido Ă© otimizado usando a taxa mĂ©dia de erro de bit como mĂ©trica. Devido ao acoplamento entre as cadeias de RF no problema de otimização, o cálculo das soluções Ăłtimas possui elevada complexidade. Para ultrapassar este problema, calculou-se a parte analĂłgica de cada cadeia de RF do equalizador de forma sequencial, usando um dicionário construĂdo a partir da resposta do agregado de antenas. Compara-se o equalizador iterativo hĂbrido para sistemas multiutilizador de arquitectura sub-conectada proposto com uma abordagem hĂbrida analĂłgica/digital totalmente conectada, recentemente proposta na literatura e com uma arquitetura totalmente digital. Os resultados mostram que o desempenho do esquema proposto aproximasse da abordagem hĂbrida totalmente conectada apĂłs apenas algumas iterações
Multi-Panel Sparse Base Station Design with Physical Antenna Effects in Massive MU-MIMO
A novel base station antenna (BSA) configuration is presented to mitigate degrading physical antenna effects in massive multiple-input multiple-output (MIMO) systems, while minimizing implementation complexities. Instead of using a commonly considered single antenna panel comprising of many elements covering a wide field-of-view (FOV) of 120 degrees, L tilted panels are used employing L times fewer elements and L times smaller FOV per panel. The spatial resolution of each panel is enhanced by employing sparse arrays with suppressed (grating-lobe) radiation outside its corresponding FOV. Therefore, more directive antenna elements can be deployed in each panel to compensate for the effective isotropic radiated power (EIRP) reduction. While sectorisation reduces the antenna gain variation in 120 degrees FOV, cooperation among multiple panels in downlink beamforming is seen to be capable of inter-panel interference suppression for sum-rate enhancement. A network model is used as a multi-user (MU) MIMO simulator incorporating both antenna and channel effects. It is shown that when the number of base station antennas is ten times the number of users, the average downlink sum-rate in pure line-of-sight (LOS), rich and poor multipath environments is increased up to 60.2%, 23% and 11.1%, respectively, by multi-panel sparse arrays applying zero-forcing (ZF) precoding
Radio Frequency Interference Impact Assessment on Global Navigation Satellite Systems
The Institute for the Protection and Security of the Citizen of the EC Joint Research Centre (IPSC-JRC) has been mandated to perform a study on the Radio Frequency (RF) threat against telecommunications and ICT control systems. This study is divided into two parts. The rst part concerns the assessment of high energy radio frequency (HERF) threats, where the focus is on the generation of electromagnetic pulses (EMP), the development of corresponding devices and the possible impact on ICT and power distribution systems. The second part of the study concerns radio frequency interference (RFI) with regard to global navigation satellite systems (GNSS). This document contributes to the second part and contains a detailed literature study disclosing the weaknesses of GNSS systems. Whereas the HERF analysis only concerns intentional interference issues, this study on GNSS also takes into account unintentional interference, enlarging the spectrum of plausible interference scenarios.JRC.DG.G.6-Security technology assessmen
System capacity enhancement for 5G network and beyond
A thesis submitted to the University of Bedfordshire, in fulfilment of the requirements for the degree of Doctor of PhilosophyThe demand for wireless digital data is dramatically increasing year over year. Wireless communication systems like Laptops, Smart phones, Tablets, Smart watch, Virtual Reality devices and so on are becoming an important part of people’s daily life. The number of mobile devices is increasing at a very fast speed as well as the requirements for mobile devices such as super high-resolution image/video, fast download speed, very short latency and high reliability, which raise challenges to the existing wireless communication networks. Unlike the previous four generation communication networks, the fifth-generation (5G) wireless communication network includes many technologies such as millimetre-wave communication, massive multiple-input multiple-output (MIMO), visual light communication (VLC), heterogeneous network (HetNet) and so forth. Although 5G has not been standardised yet, these above technologies have been studied in both academia and industry and the goal of the research is to enhance and improve the system capacity for 5G networks and beyond by studying some key problems and providing some effective solutions existing in the above technologies from system implementation and hardware impairments’ perspective.
The key problems studied in this thesis include interference cancellation in HetNet, impairments calibration for massive MIMO, channel state estimation for VLC, and low latency parallel Turbo decoding technique. Firstly, inter-cell interference in HetNet is studied and a cell specific reference signal (CRS) interference cancellation method is proposed to mitigate the performance degrade in enhanced inter-cell interference coordination (eICIC). This method takes carrier frequency offset (CFO) and timing offset (TO) of the user’s received signal into account. By reconstructing the interfering signal and cancelling it afterwards, the capacity of HetNet is enhanced.
Secondly, for massive MIMO systems, the radio frequency (RF) impairments of the hardware will degrade the beamforming performance. When operated in time duplex division (TDD) mode, a massive MIMO system relies on the reciprocity of the channel which can be broken by the transmitter and receiver RF impairments. Impairments calibration has been studied and a closed-loop reciprocity calibration method is proposed in this thesis. A test device (TD) is introduced in this calibration method that can estimate the transmitters’ impairments over-the-air and feed the results back to the base station via the Internet. The uplink pilots sent by the TD can assist the BS receivers’ impairment estimation. With both the uplink and downlink impairments estimates, the reciprocity calibration coefficients can be obtained. By computer simulation and lab experiment, the performance of the proposed method is evaluated.
Channel coding is an essential part of a wireless communication system which helps fight with noise and get correct information delivery. Turbo codes is one of the most reliable codes that has been used in many standards such as WiMAX and LTE. However, the decoding process of turbo codes is time-consuming and the decoding latency should be improved to meet the requirement of the future network. A reverse interleave address generator is proposed that can reduce the decoding time and a low latency parallel turbo decoder has been implemented on a FPGA platform. The simulation and experiment results prove the effectiveness of the address generator and show that there is a trade-off between latency and throughput with a limited hardware resource.
Apart from the above contributions, this thesis also investigated multi-user precoding for MIMO VLC systems. As a green and secure technology, VLC is achieving more and more attention and could become a part of 5G network especially for indoor communication. For indoor scenario, the MIMO VLC channel could be easily ill-conditioned. Hence, it is important to study the impact of the channel state to the precoding performance. A channel state estimation method is proposed based on the signal to interference noise ratio (SINR) of the users’ received signal. Simulation results show that it can enhance the capacity of the indoor MIMO VLC system
A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future
A High Altitude Platform Station (HAPS) is a network node that operates in
the stratosphere at an of altitude around 20 km and is instrumental for
providing communication services. Precipitated by technological innovations in
the areas of autonomous avionics, array antennas, solar panel efficiency
levels, and battery energy densities, and fueled by flourishing industry
ecosystems, the HAPS has emerged as an indispensable component of
next-generations of wireless networks. In this article, we provide a vision and
framework for the HAPS networks of the future supported by a comprehensive and
state-of-the-art literature review. We highlight the unrealized potential of
HAPS systems and elaborate on their unique ability to serve metropolitan areas.
The latest advancements and promising technologies in the HAPS energy and
payload systems are discussed. The integration of the emerging Reconfigurable
Smart Surface (RSS) technology in the communications payload of HAPS systems
for providing a cost-effective deployment is proposed. A detailed overview of
the radio resource management in HAPS systems is presented along with
synergistic physical layer techniques, including Faster-Than-Nyquist (FTN)
signaling. Numerous aspects of handoff management in HAPS systems are
described. The notable contributions of Artificial Intelligence (AI) in HAPS,
including machine learning in the design, topology management, handoff, and
resource allocation aspects are emphasized. The extensive overview of the
literature we provide is crucial for substantiating our vision that depicts the
expected deployment opportunities and challenges in the next 10 years
(next-generation networks), as well as in the subsequent 10 years
(next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial
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