17 research outputs found
Concurrent, Tunable, Multi-band, Single Chain Radio Receivers for 5G RANs
A concurrent, tunable, tri-band, single chain radio receiver for 5G radio access networks is evaluated. The three concurrent bands are independently tunable over a frequency range from 600 MHz to 2.7 GHz. A hardware-in-the-loop test-bed provides a system level evaluation of the proposed receiver using direct RF digitization. The test-bed emulates a 5G heterogeneous network supporting three wideband, simultaneous connections. By measuring the receiver EVM, we demonstrate sufficient isolation between concurrent bands achieving 60 MHz of aggregated bandwidth as well as strong resilience to adjacent blockers
Tunable, Concurrent Multiband, Single Chain Radio Architecture for Low Energy 5G-RANs
This invited paper considers a key next step in the design of radio architectures aimed at supporting low energy consumption in 5G heterogeneous radio access networks. State-of-the-art mobile radios usually require one RF transceiver per standard, each working separately at any given time. Software defined radios, while spanning a wide range of standards and frequency bands, also work separately at any specific time. In 5G radio access networks, where continuous, multiband connectivity is envisaged, this conventional radio architecture results in high network power consumption. In this paper, we propose the novel concept of a concurrent multiband frequency-agile radio (CM-FARAD) architecture, which simultaneously supports multiple standards and frequency bands using a single, tunable transceiver. We discuss the subsystem radio design approaches for enabling the CM-FARAD architecture, including antennas, power amplifiers, low noise amplifiers and analogue to digital converters. A working prototype of a dual-band CM-FARAD test-bed is also presented together with measured salient performance characteristics
Low-profile independently- and concurrently-tunable quad-band antenna for single chain sub-6GHz 5G new radio applications
This paper presents a quad-band frequency agile antenna, with independent and concurrent frequency tunability in each band, for a tunable, concurrent, quad-band single chain radio receiver for 5G New Radio (NR). More specifically, the antenna comprises of four planar slots etched in a ground plane and fed through a single microstrip feedline, without any impedance matching network. The structure is optimized to maximize isolation between the individual slots and their respective resonant frequencies. Furthermore, a novel high order harmonic suppression method is demonstrated, which controls the current distribution via creating a fictitious short circuit in the slot antenna-enabling the antenna to achieve a much wider tuning range. Numerical simulations are verified using experimental implementation and measurements, with good agreement observed. The four slots resonate around the 830 MHz, 1.8 GHz, 2.4 GHz and 3.4 GHz frequency bands, which are independently tuned (using a varactor diode in each slot) to achieve tuning ranges of approximately 64%, 66%, 27% and 33%, respectively. More importantly, the contiguous four bands covers a total frequency tuning from 0.6 to 3.6 GHz i.e. a tuning range of approximately 143%. Finally, far-field measurements are performed and the antenna is evaluated in over-the-air testbed (quad-band radio receiver), which measures the Error Vector Magnitude performance for the individual channels. Good performance is observed, confirming acceptable isolation performance between the four bands. The data reported in this paper is available, from ORDA-The University of Sheffield Research Data Catalogue and Repository, at https://doi.org/10.15131/shef.data.11219000.v1
An Independently Tunable Tri-band Antenna Design for Concurrent Multi-band Single Chain Radio Receivers
In this paper, a novel tunable tri-band antenna
is presented for concurrent, multi-band, single chain radio
receivers. The antenna is manufactured on a 50×100 mm FR4
printed circuit board (PCB), and is able to provide three concurrent,
independently tunable operating bands covering a frequency
range from 600 MHz to 2.7 GHz. The antenna performance
is investigated for both numerical and experimental methods
when using, first, varactor diodes and, second, digitally tunable
capacitors (DTCs) to tune frequencies, which shows the antenna
gain can be improved by up to 2.6 dBi by using DTCs. A
hardware-in-the-loop test-bed provides a system level evaluation
of the proposed antenna in a direct RF digitized, concurrent,
tri-band radio receiver. By measuring the receiver’s error vector
magnitude, we demonstrate sufficient isolation between concurrent
bands achieving 30 MHz of aggregated bandwidth as well
as strong resilience to adjacent blockers next to each band. The
data reported in this article are available from the ORDA digital
repository (https://doi.org/10.15131/shef.data.5346295)
Direct IF sampling receivers for 5G millimeter-wave communications systems
Reducing receiver complexity and power consumption are important design goals in fifth-generation (5G) millimeter-wave (mm-wave) communications systems. One approach for achieving these goals is to employ direct intermediate frequency (IF) sampling at sub-Nyquist rates in a superheterodyne receiver architecture using digital downconversion of the IF signal. This paper presents original measured results characterizing in detail the signal-to-noise-ratio (SNR), error vector magnitude (EVM), and block error rate (BLER) performances of a direct IF subsampling mm-wave receiver with subsampling rate as a parameter. A software-defined radio (SDR) receiver using direct IF subsampling was implemented in a 28GHz, beamforming, over-the-air (OTA), hardware-in-the-loop (HWIL), SDR testbed using a 2.52 GHz IF. For a quadrature phase shift keying (QPSK) modulated long-term evolution (LTE) signal subsampled at 500 MHz, a small SNR penalty of ˜3dB at 5% BLER was obtained over a 10 GHz Nyquist sampling benchmark
The effect of ADC resolution on concurrent, multiband, direct RF sampling receivers
Connectivity using interband frequencies in 4G and 5G radio access networks, for example, carrier aggregation or dual-connectivity, incurs high receiver complexity and power consumption, in particular, when implemented using multiple radio units. Employing concurrent, multiband, direct RF sampling in a single radio chain architecture reduces the RF component count, leading to lower receiver complexity and power consumption. For this architecture, as the composite signal from multiple concurrent bands is digitized by a common analog-to-digital converter (ADC), the bit resolution critically affects system performance. In this paper, the effect of ADC resolution on the error vector magnitude (EVM) and Block Error Rate (BLER) performance of a concurrent, multiband, direct RF sampling receiver is investigated. Simulation and hardware measurement of a tri-band Long Term Evolution (LTE) system supporting three simultaneously active channels at 888 MHz, 1.92 GHz and 2.52 GHz is evaluated when reducing the ADC resolution from 8 to 3 bits. Interband interference measurements demonstrate that the multiband, direct RF sampling, wideband LTE receiver remains 3GPP compliant at 4-bit ADC resolution with the signal-to-noise-ratio (SNR) desensitization over a single-band receiver limited to 9 dB in the 888 MHz band
Otimização do fronthaul ótico para redes de acesso de rádio (baseadas) em computação em nuvem (CC-RANs)
Doutoramento conjunto (MAP-Tele) em Engenharia Eletrotécnica/TelecomunicaçõesA proliferação de diversos tipos de dispositivos moveis, aplicações e serviços
com grande necessidade de largura de banda têm contribuído para o aumento
de ligações de banda larga e ao aumento do volume de trafego das
redes de telecomunicações moveis. Este aumento exponencial tem posto
uma enorme pressão nos mobile operadores de redes móveis (MNOs). Um
dos aspetos principais deste recente desenvolvimento, é a necessidade que as
redes têm de oferecer baixa complexidade nas ligações, como também baixo
consumo energético, muito baixa latência e ao mesmo tempo uma grande
capacidade por baixo usto. De maneira a resolver estas questões, os MNOs
têm focado a sua atenção na redes de acesso por rádio em nuvem (C-RAN)
principalmente devido aos seus benefícios em termos de otimização de performance
e relação qualidade preço. O standard para a distribuição de sinais
sem fios por um fronthaul C-RAN é o common public radio interface (CPRI).
No entanto, ligações óticas baseadas em interfaces CPRI necessitam de uma
grande largura de banda. Estes requerimentos podem também ser atingidos
com uma implementação em ligação free space optical (FSO) que é um sistema
ótico que usa comunicação sem fios. O FSO tem sido uma alternativa
muito apelativa aos sistemas de comunicação rádio (RF) pois combinam a
flexibilidade e mobilidade das redes RF ao mesmo tempo que permitem a
elevada largura de banda permitida pelo sistema ótico. No entanto, as ligações
FSO são suscetíveis a alterações atmosféricas que podem prejudicar
o desempenho do sistema de comunicação. Estas limitações têm evitado o
FSO de ser tornar uma excelente solução para o fronthaul. Uma caracterização
precisa do canal e tecnologias mais avançadas são então necessárias
para uma implementação pratica de ligações FSO. Nesta tese, vamos estudar
uma implementação eficiente para fronthaul baseada em tecnologia
á rádio-sobre-FSO (RoFSO). Propomos expressões em forma fechada para
mitigação das perdas de propagação e para a estimação da capacidade do
canal de maneira a aliviar a complexidade do sistema de comunicação. Simulações
numéricas são também apresentadas para formatos de modulação
adaptativas. São também considerados esquemas como um sistema hibrido
RF/FSO e tecnologias de transmissão apoiadas por retransmissores
que ajudam a alivar os requerimentos impostos por um backhaul/fronthaul
de C-RAN. Os modelos propostos não só reduzem o esforço computacional,
como também têm outros méritos, tais como, uma elevada precisão na estimação
do canal e desempenho, baixo requisitos na capacidade de memória
e uma rápida e estável operação comparativamente com o estado da arte
em sistemas analíticos (PON)-FSO. Este sistema é implementado num recetor
em tempo real que é emulado através de uma field-programmable gate
array (FPGA) comercial. Permitindo assim um sistema aberto, interoperabilidade,
portabilidade e também obedecer a standards de software aberto.
Os esquemas híbridos têm a habilidade de suportar diferentes aplicações,
serviços e múltiplos operadores a partilharem a mesma infraestrutura de
fibra ótica.The proliferation of different mobile devices, bandwidth-intensive applications
and services contribute to the increase in the broadband connections
and the volume of traffic on the mobile networks. This exponential growth
has put considerable pressure on the mobile network operators (MNOs). In
principal, there is a need for networks that not only offer low-complexity,
low-energy consumption, and extremely low-latency but also high-capacity
at relatively low cost. In order to address the demand, MNOs have given significant
attention to the cloud radio access network (C-RAN) due to its beneficial
features in terms of performance optimization and cost-effectiveness.
The de facto standard for distributing wireless signal over the C-RAN fronthaul
is the common public radio interface (CPRI). However, optical links
based on CPRI interfaces requires large bandwidth. Also, the aforementioned
requirements can be realized with the implementation of free space
optical (FSO) link, which is an optical wireless system. The FSO is an appealing
alternative to the radio frequency (RF) communication system that
combines the flexibility and mobility offered by the RF networks with the
high-data rates provided by the optical systems. However, the FSO links are
susceptible to atmospheric impairments which eventually hinder the system
performance. Consequently, these limitations prevent FSO from being an
efficient standalone fronthaul solution. So, precise channel characterizations
and advanced technologies are required for practical FSO link deployment
and operation. In this thesis, we study an efficient fronthaul implementation
that is based on radio-on-FSO (RoFSO) technologies. We propose closedform
expressions for fading-mitigation and for the estimation of channel
capacity so as to alleviate the system complexity. Numerical simulations
are presented for adaptive modulation scheme using advanced modulation
formats. We also consider schemes like hybrid RF/FSO and relay-assisted
transmission technologies that can help in alleviating the stringent requirements
by the C-RAN backhaul/fronthaul. The propose models not only
reduce the computational requirements/efforts, but also have a number of
diverse merits such as high-accuracy, low-memory requirements, fast and
stable operation compared to the current state-of-the-art analytical based
approaches. In addition to the FSO channel characterization, we present
a proof-of-concept experiment in which we study the transmission capabilities
of a hybrid passive optical network (PON)-FSO system. This is
implemented with the real-time receiver that is emulated by a commercial
field-programmable gate array (FPGA). This helps in facilitating an
open system and hence enables interoperability, portability, and open software
standards. The hybrid schemes have the ability to support different
applications, services, and multiple operators over a shared optical fiber
infrastructure
Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies, and Future Directions
Future wireless systems are envisioned to create an endogenously
holography-capable, intelligent, and programmable radio propagation
environment, that will offer unprecedented capabilities for high spectral and
energy efficiency, low latency, and massive connectivity. A potential and
promising technology for supporting the expected extreme requirements of the
sixth-generation (6G) communication systems is the concept of the holographic
multiple-input multiple-output (HMIMO), which will actualize holographic radios
with reasonable power consumption and fabrication cost. The HMIMO is
facilitated by ultra-thin, extremely large, and nearly continuous surfaces that
incorporate reconfigurable and sub-wavelength-spaced antennas and/or
metamaterials. Such surfaces comprising dense electromagnetic (EM) excited
elements are capable of recording and manipulating impinging fields with utmost
flexibility and precision, as well as with reduced cost and power consumption,
thereby shaping arbitrary-intended EM waves with high energy efficiency. The
powerful EM processing capability of HMIMO opens up the possibility of wireless
communications of holographic imaging level, paving the way for signal
processing techniques realized in the EM-domain, possibly in conjunction with
their digital-domain counterparts. However, in spite of the significant
potential, the studies on HMIMO communications are still at an initial stage,
its fundamental limits remain to be unveiled, and a certain number of critical
technical challenges need to be addressed. In this survey, we present a
comprehensive overview of the latest advances in the HMIMO communications
paradigm, with a special focus on their physical aspects, their theoretical
foundations, as well as the enabling technologies for HMIMO systems. We also
compare the HMIMO with existing multi-antenna technologies, especially the
massive MIMO, present various...Comment: double column, 58 page
Telecommunication Systems
This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study
Software Defined Applications in Cellular and Optical Networks
abstract: Small wireless cells have the potential to overcome bottlenecks in wireless access through the sharing of spectrum resources. A novel access backhaul network architecture based on a Smart Gateway (Sm-GW) between the small cell base stations, e.g., LTE eNBs, and the conventional backhaul gateways, e.g., LTE Servicing/Packet Gateways (S/P-GWs) has been introduced to address the bottleneck. The Sm-GW flexibly schedules uplink transmissions for the eNBs. Based on software defined networking (SDN) a management mechanism that allows multiple operator to flexibly inter-operate via multiple Sm-GWs with a multitude of small cells has been proposed. This dissertation also comprehensively survey the studies that examine the SDN paradigm in optical networks. Along with the PHY functional split improvements, the performance of Distributed Converged Cable Access Platform (DCCAP) in the cable architectures especially for the Remote-PHY and Remote-MACPHY nodes has been evaluated. In the PHY functional split, in addition to the re-use of infrastructure with a common FFT module for multiple technologies, a novel cross functional split interaction to cache the repetitive QAM symbols across time at the remote node to reduce the transmission rate requirement of the fronthaul link has been proposed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201