Distributed multi-user MIMO transmission using real-time sigma-delta-over-fiber for next generation fronthaul interface

To achieve the massive device connectivity and high data rate demanded by 5G, wireless transmission with wider signal bandwidths and higher-order multiple-input multiple-output (MIMO) is inevitable. This work demonstrates a possible function split option for the next generation fronthaul interface (NGFI). The proof-of-concept downlink architecture consists of real-time sigma-delta modulated signal over fiber (SDoF) links in combination with distributed multi-user (MU) MIMO transmission. The setup is fully implemented using off-the-shelf and in-house developed components. A single SDoF link achieves an error vector magnitude (EVM) of 3.14% for a 163.84 MHz-bandwidth 256-QAM OFDM signal (958.64 Mbps) with a carrier frequency around 3.5 GHz transmitted over 100 m OM4 multi-mode fiber at 850 nm using a commercial QSFP module. The centralized architecture of the proposed setup introduces no frequency asynchronism among remote radio units. For most cases, the 2 x 2 MU-MIMO transmission has little performance degradation compared to SISO, 0.8 dB EVM degradation for 40.96 MHz-bandwidth signals and 1.4 dB for 163.84 MHz-bandwidth on average, implying that the wireless spectral efficiency almost doubles by exploiting spatial multiplexing. A 1.4 Gbps data rate (720 Mbps per user, 163.84 MHz-bandwidth, 64-QAM) is reached with an average EVM of 6.66%. The performance shows that this approach is feasible for the high-capacity hot-spot scenario

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

包絡線パルス幅変調によるOFDM信号の光ファイバ無線伝送に関する研究

In this thesis, an Envelop Pulse-Width Modulation-RoF (EPWM-RoF) transmission scheme is proposed to solve the RoF nonlinearity and echo effect issues. Through the theoretical analysis, simulation and experimental results, it can be concluded that EPWM-RoF transmission is effective in dealing with E/O nonlinearity and echo effect in RoF channel.電気通信大学201

Radio-over-fibre technologies arising from the Building the future Optical Network in Europe (BONE) project

[EN] This study describes a wide range of salient radio-over-fibre system issues. Impulse radio and multiband ultra-wideband signal distribution over both single-mode fibre and multi-mode fibre (MMF) implementations are considered. Carrier frequencies ranging from 3.1 to 10.6 GHz, up to 60 GHz, are featured, and the use of microring laser transmitters is discussed. A cost-performance comparative analysis of competing distributed antenna system topologies is presented, and a theoretical approach to understanding the factors underlying radio-over-MMF performance for within-building applications is discussed. Finally, techniques to minimise thermal impacts on performance are described and novel energy-efficient schemes are introduced. Overall, this study provides a snap-shot of research being undertaken by European institutes involved in the Building the future Optical Network in Europe (BONE) project.The work described in this paper was carried out with the support of the EU-FP7 Network of Excellence BONE project.Parker, M.; Walker, SD.; Llorente, R.; Morant, M.; Beltrán, M.; Möllers, I.; Jäger, D.... (2010). Radio-over-fibre technologies arising from the Building the future Optical Network in Europe (BONE) project. IET Optoelectronics. 4(6):247-259. https://doi.org/10.1049/iet-opt.2009.0062S24725946http://www.ftthcouncil.euGomes, N. J., Morant, M., Alphones, A., Cabon, B., Mitchell, J. E., Lethien, C., … Iezekiel, S. (2009). Radio-over-fiber transport for the support of wireless broadband services [Invited]. Journal of Optical Networking, 8(2), 156. doi:10.1364/jon.8.000156Thakur, M. P., Quinlan, T. J., Bock, C., Walker, S. D., Toycan, M., Dudley, S. E. M., … Ben-Ezra, Y. (2009). 480-Mbps, Bi-Directional, Ultra-Wideband Radio-Over-Fiber Transmission Using a 1308/1564-nm Reflective Electro-Absorption Transducer and Commercially Available VCSELs. Journal of Lightwave Technology, 27(3), 266-272. doi:10.1109/jlt.2008.2005644ECMA-368 International Standard: ‘High rate ultra wideband PHY and MAC standard’, December 2008FCC 02-48: ‘Revision of part 15 of the commission's rules regarding ultra-wideband transmission systems’, April 2002ECC∕DEC∕(06)04: ‘On the harmonised conditions for devices using ultra-wideband (UWB) technology in bands below 10.6 GHz’, March 2006ETSI EN 302 065 V1.1.1 (2008-02): ‘Electromagnetic compatibility and radio spectrum matters (ERM); ultra wideband (UWB) technologies for communication purposes; harmonized EN covering the essential requirements of article 3.2 of the R&TTE Directive’, February 2008WiMedia Alliance: Worldwide regulatory status [online]. Available at: http://www.wimedia.orgMikroulis, S., Simos, H., Roditi, E., & Syvridis, D. (2005). Ultrafast all-optical AND logic operation based on four-wave mixing in a passive InGaAsP-InP microring resonator. IEEE Photonics Technology Letters, 17(9), 1878-1880. doi:10.1109/lpt.2005.853260Argyris, A., Hamacher, M., Chlouverakis, K. E., Bogris, A., & Syvridis, D. (2008). Photonic Integrated Device for Chaos Applications in Communications. Physical Review Letters, 100(19). doi:10.1103/physrevlett.100.194101Win, M. Z., & Scholtz, R. A. (1998). On the robustness of ultra-wide bandwidth signals in dense multipath environments. IEEE Communications Letters, 2(2), 51-53. doi:10.1109/4234.660801Flatman, A.: In-premises optical fibre installed base analysis to 2007. Presented at the IEEE 802.3 10GbE over FDDI Grade Fibre Study Group, Orlando, FL, March 2004Raddatz, L., & White, I. H. (1999). Overcoming the modal bandwidth limitation of multimode fiber by using passband modulation. IEEE Photonics Technology Letters, 11(2), 266-268. doi:10.1109/68.740725Hartmann, P., Xin Qian, Wonfor, A., Penty, R. V., & White, I. H. (2005). 1-20 GHz Directly Modulated Radio over MMF Link. 2005 International Topical Meeting on Microwave Photonics. doi:10.1109/mwp.2005.203548Kanprachar, S., & Jacobs, I. (2003). Diversity coding for subcarrier multiplexing on multimode fibers. IEEE Transactions on Communications, 51(9), 1546-1553. doi:10.1109/tcomm.2003.816981Gasulla, I., & Capmany, J. (2006). Transfer function of multimode fiber links using an electric field propagation model: Application to Radio over Fibre Systems. Optics Express, 14(20), 9051. doi:10.1364/oe.14.009051Al-Raweshidy, H., and Komaki, S.: ‘Radio over fiber technologies for mobile communication networks’, (Artech House 2002)Sauer, M., Kobyakov, A., & George, J. (2007). Radio Over Fiber for Picocellular Network Architectures. Journal of Lightwave Technology, 25(11), 3301-3320. doi:10.1109/jlt.2007.906822Gomes, N. J., Nkansah, A., & Wake, D. (2008). Radio-Over-MMF Techniques—Part I: RF to Microwave Frequency Systems. Journal of Lightwave Technology, 26(15), 2388-2395. doi:10.1109/jlt.2008.925624Rajan, G., Semenova, Y., Pengfei Wang, & Farrell, G. (2009). Temperature-Induced Instabilities in Macro-Bend Fiber Based Wavelength Measurement Systems. Journal of Lightwave Technology, 27(10), 1355-1361. doi:10.1109/jlt.2009.2014081Montalvo, J., Vázquez, C., & Montero, D. S. (2006). CWDM self-referencing sensor network based on ring resonators in reflective configuration. Optics Express, 14(11), 4601. doi:10.1364/oe.14.00460

Coherent terabit communications with microresonator Kerr frequency combs

Optical frequency combs enable coherent data transmission on hundreds of wavelength channels and have the potential to revolutionize terabit communications. Generation of Kerr combs in nonlinear integrated microcavities represents a particularly promising option enabling line spacings of tens of GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr combs may exhibit strong phase noise and multiplet spectral lines, and this has made high-speed data transmission impossible up to now. Recent work has shown that systematic adjustment of pump conditions enables low phase-noise Kerr combs with singlet spectral lines. Here we demonstrate that Kerr combs are suited for coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the optical source. In a first experiment, we encode a data stream of 392 Gbit/s on subsequent lines of a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment shows feedback-stabilization of a Kerr comb and transmission of a 1.44 Tbit/s data stream over a distance of up to 300 km. The results demonstrate that Kerr combs can meet the highly demanding requirements of multi-terabit/s coherent communications and thus offer a solution towards chip-scale terabit/s transceivers

Analog radio over fiber solutions for multi-band 5g systems

This study presents radio over fiber (RoF) solutions for the fifth-generation (5G) of wireless networks. After the state of the art and a technical background review, four main contributions are reported. The first one is proposing and investigating a RoF technique based on a dual-drive Mach-Zehnder modulator (DD-MZM) for multi-band mobile fronthauls, in which two radiofrequency (RF) signals in the predicted 5G bands individually feed an arm of the optical modulator. Experimental results demonstrate the approach enhances the RF interference mitigation and can prevail over traditional methods. The second contribution comprises the integration of a 5G transceiver, previously developed by our group, in a passive optical network (PON) using RoF technology and wavelength division multiplexing (WDM) overlay. The proposed architecture innovates by employing DD-MZM and enables to simultaneously transport baseband and 5G candidate RF signals in the same PON infrastructure. The proof-of-concept includes the transmission of a generalized frequency division multiplexing (GFDM) signal generated by the 5G transceiver in the 700 MHz band, a 26 GHz digitally modulated signal as a millimeter-waves 5G band, and a baseband signal from an gigabit PON (GPON). Experimental results demonstrate the 5G transceiver digital performance when using RoF technology for distributing the GFDM signal, as well as Gbit/s throughput at 26 GHz. The third contribution is the implementation of a flexible-waveform and multi-application fiber-wireless (FiWi) system toward 5G. Such system includes the FiWi transmission of the GFDM and filtered orthogonal frequency division multiplexing (F-OFDM) signals at 788 MHz, toward long-range cells for remote or rural mobile access, as well as the recently launched 5G NR standard in microwave and mm-waves, aiming enhanced mobile broadband indoor and outdoor applications. Digital signal processing (DSP) is used for selecting the waveform and linearizing the RoF link. Experimental results demonstrate the suitability of the proposed solution to address 5G scenarios and requirements, besides the applicability of using existent fiber-to-the-home (FTTH) networks from Internet service providers for implementing 5G systems. Finally, the fourth contribution is the implementation of a multi-band 5G NR system with photonic-assisted RF amplification (PAA). The approach takes advantage of a novel PAA technique, based on RoF technology and four-wave mixing effect, that allows straightforward integration to the transport networks. Experimental results demonstrate iv uniform and stable 15 dB wideband gain for Long Term Evolution (LTE) and three 5G signals, distributed in the frequency range from 780 MHz to 26 GHz and coexisting in the mobile fronthaul. The obtained digital performance has efficiently met the Third-Generation Partnership Project (3GPP) requirements, demonstrating the applicability of the proposed approach for using fiber-optic links to distribute and jointly amplify LTE and 5G signals in the optical domain.Agência 1Este trabalho apresenta soluções de rádio sobre fibra (RoF) para aplicações em redes sem fio de quinta geração (5G), e inclui quatro contribuições principais. A primeira delas refere-se à proposta e investigação de uma técnica de RoF baseada no modulador eletroóptico de braço duplo, dual-drive Mach-Zehnder (DD-MZM), para a transmissão simultânea de sinais de radiofrequência (RF) em bandas previstas para redes 5G. Resultados experimentais demonstram que o uso do DD-MZM favorece a ausência de interferência entre os sinais de RF transmitidos. A segunda contribuição trata da integração de um transceptor de RF, desenvolvido para aplicações 5G e apto a prover a forma de onda conhecida como generalized frequency division multiplexing (GFDM), em uma rede óptica passiva (PON) ao utilizar RoF e multiplexação por divisão de comprimento de onda (WDM). A arquitetura proposta permite transportar, na mesma infraestrutura de rede, sinais em banda base e de radiofrequência nas faixas do espectro candidatas para 5G. A prova de conceito inclui a distribuição conjunta de três tipos de sinais: um sinal GFDM na banda de 700 MHz, proveniente do transceptor desenvolvido; um sinal digital na frequência de 26 GHz, assumindo a faixa de ondas milimétricas; sinais em banda base provenientes de uma PON dedicada ao serviço de Internet. Resultados experimentais demonstram o desempenho do transceptor de RF ao utilizar a referida arquitetura para distribuir sinais GFDM, além de taxas de transmissão de dados da ordem de Gbit/s na faixa de 26 GHz. A terceira contribuição corresponde à implementação de um sistema fibra/rádio potencial para redes 5G, operando inclusive com o padrão ―5G New Radio (5G NR)‖ nas faixas de micro-ondas e ondas milimétricas. Tal sistema é capaz de prover macro células na banda de 700 MHz para aplicações de longo alcance e/ou rurais, utilizando sinais GFDM ou filtered orthogonal frequency division multiplexing (F-OFDM), assim como femto células na banda de 26 GHz, destinada a altas taxas de transmissão de dados para comunicações de curto alcance. Resultados experimentais demonstram a aplicabilidade da solução proposta para redes 5G, além da viabilidade de utilizar redes ópticas pertencentes a provedores de Internet para favorecer sistemas de nova geração. Por fim, a quarta contribuição trata da implementação de um sistema 5G NR multibanda, assistido por amplificação de RF no domínio óptico. Esse sistema faz uso de um novo método de amplificação, baseado no efeito não linear da mistura de quatro ondas, que vi permite integração direta em redes de transporte envolvendo rádio sobre fibra. Resultados experimentais demonstram ganho de RF igual a 15 dB em uma ampla faixa de frequências (700 MHz até 26 GHz), atendendo simultaneamente tecnologias de quarta e quinta geração. O desempenho digital obtido atendeu aos requisitos estabelecidos pela 3GPP (Third-Generation Partnership Project), indicando a aplicabilidade da solução em questão para distribuir e conjuntamente amplificar sinais de RF em enlaces de fibra óptica

Digital predistortion of RF amplifiers using baseband injection for mobile broadband communications

Radio frequency (RF) power amplifiers (PAs) represent the most challenging design parts of wireless transmitters. In order to be more energy efficient, PAs should operate in nonlinear region where they produce distortion that significantly degrades the quality of signal at transmitter’s output. With the aim of reducing this distortion and improve signal quality, digital predistortion (DPD) techniques are widely used. This work focuses on improving the performances of DPDs in modern, next-generation wireless transmitters. A new adaptive DPD based on an iterative injection approach is developed and experimentally verified using a 4G signal. The signal performances at transmitter output are notably improved, while the proposed DPD does not require large digital signal processing memory resources and computational complexity. Moreover, the injection-based DPD theory is extended to be applicable in concurrent dual-band wireless transmitters. A cross-modulation problem specific to concurrent dual-band transmitters is investigated in detail and novel DPD based on simultaneous injection of intermodulation and cross-modulation distortion products is proposed. In order to mitigate distortion compensation limit phenomena and memory effects in highly nonlinear RF PAs, this DPD is further extended and complete generalised DPD system for concurrent dual-band transmitters is developed. It is clearly proved in experiments that the proposed predistorter remarkably improves the in-band and out-of-band performances of both signals. Furthermore, it does not depend on frequency separation between frequency bands and has significantly lower complexity in comparison with previously reported concurrent dual-band DPDs

Digital Pre-distortion for Interference Reduction in Dynamic Spectrum Access Networks

Given the ever increasing reliance of today’s society on ubiquitous wireless access, the paradigm of dynamic spectrum access (DSA) as been proposed and implemented for utilizing the limited wireless spectrum more efficiently. Orthogonal frequency division multiplexing (OFDM) is growing in popularity for adoption into wireless services employing DSA frame- work, due to its high bandwidth efficiency and resiliency to multipath fading. While these advantages have been proven for many wireless applications, including LTE-Advanced and numerous IEEE wireless standards, one potential drawback of OFDM or its non-contiguous variant, NC-OFDM, is that it exhibits high peak-to-average power ratios (PAPR), which can induce in-band and out-of-band (OOB) distortions when the peaks of the waveform enter the compression region of the transmitter power amplifier (PA). Such OOB emissions can interfere with existing neighboring transmissions, and thereby severely deteriorate the reliability of the DSA network. A performance-enhancing digital pre-distortion (DPD) technique compensating for PA and in-phase/quadrature (I/Q) modulator distortions is proposed in this dissertation. Al- though substantial research efforts into designing DPD schemes have already been presented in the open literature, there still exists numerous opportunities to further improve upon the performance of OOB suppression for NC-OFDM transmission in the presence of RF front-end impairments. A set of orthogonal polynomial basis functions is proposed in this dissertation together with a simplified joint DPD structure. A performance analysis is presented to show that the OOB emissions is reduced to approximately 50 dBc with proposed algorithms employed during NC-OFDM transmission. Furthermore, a novel and intuitive DPD solution that can minimize the power regrowth at any pre-specified frequency in the spurious domain is proposed in this dissertation. Conventional DPD methods have been proven to be able to effectively reduce the OOB emissions that fall on top of adjacent channels. However more spectral emissions in more distant frequency ranges are generated by employing such DPD solutions, which are potentially in violation of the spurious emission limit. At the same time, the emissions in adjacent channel must be kept under the OOB limit. To the best of the author’s knowledge, there has not been extensive research conducted on this topic. Mathematical derivation procedures of the proposed algorithm are provided for both memoryless nonlinear model and memory-based nonlinear model. Simulation results show that the proposed method is able to provide a good balance of OOB emissions and emissions in the far out spurious domain, by reducing the spurious emissions by 4-5 dB while maintaining the adjacent channel leakage ratio (ACLR) improvement by at least 10 dB, comparing to the PA output spectrum without any DPD

Design of linear transmitters for wireless applications

Wireless standards for high data-rate communications typically employ complex modulation schemes that have large peak-to-average power ratios (PAPR), along with a significant bandwidth requirement. Transmitters for such applications often employ off-chip power amplifiers (PAs), that are typically operated in back-off, such that the peak output power is less than the output 1-dB compression point (P1dB), in order to minimize distortion. In mobile systems, architectures that can enhance the linearity of the transmit chain are highly attractive since these can reduce the PA's back-off requirement, which helps to enhance efficiency. In this dissertation, linearization techniques for mobile transmitters are explored. A Cartesian feedback-feedforward transmitter is proposed for linearity enhancement. The transmit path in the architecture is placed in a Cartesian feedback loop. The feedback error signal is applied to a Cartesian feedforward path for further linearity improvement. Linearity of the feedback-feedforward system is analyzed by using a Volterra series representation. System simulations using two-tone signals and modulated signals are also presented and are used to verify the linearity enhancement provided by the proposed architecture. A prototype transmitter IC that employs the Cartesian feedback-feedforward approach is implemented in a 0.13 μm CMOS process. Design considerations for critical transmitter circuits are discussed. A proof-of-concept Cartesian feedback-feedforward architecture that includes the prototype IC and external components is demonstrated. The implementation allows for a 8.7 dB improvement in the adjacent channel leakage ratio (ACLR), compared to an open-loop transmitter, for an output power of 16.6 dBm at 2.4 GHz while employing a 16-QAM LTE signal with 1.4 MHz bandwidth. The linearity of the Cartesian feedback-feedforward system is found to depend primarily on the loop gain of the Cartesian feedback and the linearity of the Cartesian feedforward path, which introduces a trade-off with power consumption. To enhance the linearity of the Cartesian feedback-feedforward transmitter even further within the Cartesian feedback loop, two modified Cartesian feedback-feedforward architectures are explored. System simulations show that both modified configurations can help to enhance linearity compared to the above Cartesian feedback-feedforward transmitter.Electrical and Computer Engineerin