On Spectral Coexistence of CP-OFDM and FB-MC Waveforms in 5G Networks

Future 5G networks will serve a variety of applications that will coexist on the same spectral band and geographical area, in an uncoordinated and asynchronous manner. It is widely accepted that using CP-OFDM, the waveform used by most current communication systems, will make it difficult to achieve this paradigm. Especially, CP-OFDM is not adapted for spectral coexistence because of its poor spectral localization. Therefore, it has been widely suggested to use filter bank based multi carrier (FB-MC) waveforms with enhanced spectral localization to replace CP-OFDM. Especially, FB-MC waveforms are expected to facilitate coexistence with legacy CP-OFDM based systems. However, this idea is based on the observation of the PSD of FB-MC waveforms only. In this paper, we demonstrate that this approach is flawed and show what metric should be used to rate interference between FB-MC and CP-OFDM systems. Finally, our results show that using FB-MC waveforms does not facilitate coexistence with CP-OFDM based systems to a high extent.Comment: Manuscript submitted for review to IEEE Transactions on Wireless Communication

Experimental demonstration of multi-Gbps multi sub-bands FBMC transmission in mm-wave radio over a fiber system

The filter bank multicarrier (FBMC) modulation format is considered as a potential candidate for future wireless 5G due to its feature of high suppression for out-of-band emissions, which allows combining multiple sub-bands with very narrow band-gaps, and hence increases the overall wireless transmission capacity. In this paper, we experimentally demonstrate the generation of multi sub-bands FBMC signals at millimeter-wave (mm-wave) for radio-over-fiber (RoF) systems. The designed multi sub-bands FBMC system consists of 5 sub-bands of 800 MHz with inter sub-band gaps of 781.25 kHz. The composite 5 sub-bands FBMC signal is generated with no band-gap between dc to the first sub-band to preserve the bandwidth of the system. Each FBMC sub-band consists of 1024 sub-carriers and is modulated with uncorrelated data sequences. The aggregate FBMC signal is carried optically by externally modulating a free running laser and is converted to millimeter waves (mm-waves) by photomixing with another free running laser at a frequency offset of 53 GHz. At the receiver, the received electrical mm-wave signal is down-converted to an intermediate frequency (IF) and then post-processed using digital signal processing (DSP) techniques. With the use of the simple recursive least square (RLS) equalizer in the DSP receiver, the achieved aggregate data rate is 8 Gbps and 12 Gbps for 16 quadrature amplitude modulation (QAM), and 64 QAM, respectively with a total bandwidth of 4.2 GHz. The system performance is evaluated by measuring error vector magnitude (EVM) and bit error rate (BER) calculations

Generalized Fast-Convolution-based Filtered-OFDM: Techniques and Application to 5G New Radio

This paper proposes a generalized model and methods for fast-convolution (FC)-based waveform generation and processing with specific applications to fifth generation new radio (5G-NR). Following the progress of 5G-NR standardization in 3rd generation partnership project (3GPP), the main focus is on subband-filtered cyclic prefix (CP) orthogonal frequency-division multiplexing (OFDM) processing with specific emphasis on spectrally well localized transmitter processing. Subband filtering is able to suppress the interference leakage between adjacent subbands, thus supporting different numerologies for so-called bandwidth parts as well as asynchronous multiple access. The proposed generalized FC scheme effectively combines overlapped block processing with time- and frequency-domain windowing to provide highly selective subband filtering with very low intrinsic interference level. Jointly optimized multi-window designs with different allocation sizes and design parameters are compared in terms of interference levels and implementation complexity. The proposed methods are shown to clearly outperform the existing state-of-the-art windowing and filtering-based methods.Comment: To appear in IEEE Transactions on Signal Processin

Doctor of Philosophy

dissertationWireless communications pervade all avenues of modern life. The rapid expansion of wireless services has increased the need for transmission schemes that are more spectrally efficient. Dynamic spectrum access (DSA) systems attempt to address this need by building a network where the spectrum is used opportunistically by all users based on local and regional measurements of its availability. One of the principal requirements in DSA systems is to initialize and maintain a control channel to link the nodes together. This should be done even before a complete spectral usage map is available. Additionally, with more users accessing the spectrum, it is important to maintain a stable link in the presence of significant interference in emergency first-responders, rescue, and defense applications. In this thesis, a new multicarrier spread spectrum (MC-SS) technique based on filter banks is presented. The new technique is called filter bank multicarrier spread spectrum (FB-MC-SS). A detailed theory of the underlying properties of this signal are given, with emphasis on the properties that lend themselves to synchronization at the receiver. Proposed algorithms for synchronization, channel estimation, and detection are implemented on a software-defined radio platform to complete an FB-MC-SS transceiver and to prove the practicality of the technique. FB-MC-SS is shown through physical experimentation to be significantly more robust to partial band interference compared to direct sequence spread spectrum. With a higher power interfering signal occupying 90% of its band, FB-MC-SS maintains a low bit error rate. Under the same interference conditions, DS-SS fails completely. This experimentation leads to a theoretical analysis that shows in a frequency selective channel with additive white noise, the FB-MC-SS system has performance that equals that obtained by a DS-SS system employing an optimal rake receiver. This thesis contains a detailed chapter on implementation and design, including lessons learned while prototyping the system. This is to assist future system designers to quickly gain proficiency in further development of this technology

Performance of a filterBank multiCarrier (FBMC) physical layer in the WiMAX context

This paper describes some of the outcome of the FP7 project PHYDYAS, whose main objective was to propose a new physical layer that will enable introduction of cognitive radios and dynamic access spectrum management. During the project both a software simulator and a demonstrator have been developed. A description of the demonstrator and some simulation results that show the differences in spectral efficiency and the sensititvity to synchronisation errors between OFDM and FBMC are given. The simulator, which is written in Matlab, was used to evaluate the performance of both OFDM and FBMC in a WiMAX context, i.e. the frame format is kept as close as possible to WiMAX. From the simulation results it has been possible to analyze the performance differences between the two systems. In addition to that the simulator was used as a reference in the validation of the demonstrator. The transmitter in the demonstrator is implemented in hardware and operates in real time. The channel emulation and up-conversion to RF is done using commercially available instruments from Agilent which have been modified to fit to the task. In the demonstrator receiver the hardware front-end converts the signal to baseband and digitizes it. The OFDM/FBMC signal processing is done in near real time on a general purpose computer connected to the front- end hardware.Postprint (published version

NOVEL OFDM SYSTEM BASED ON DUAL-TREE COMPLEX WAVELET TRANSFORM

The demand for higher and higher capacity in wireless networks, such as cellular, mobile and local area network etc, is driving the development of new signaling techniques with improved spectral and power efficiencies. At all stages of a transceiver, from the bandwidth efficiency of the modulation schemes through highly nonlinear power amplifier of the transmitters to the channel sharing between different users, the problems relating to power usage and spectrum are aplenty. In the coming future, orthogonal frequency division multiplexing (OFDM) technology promises to be a ready solution to achieving the high data capacity and better spectral efficiency in wireless communication systems by virtue of its well-known and desirable characteristics. Towards these ends, this dissertation investigates a novel OFDM system based on dual-tree complex wavelet transform (D

Study on Air Interface Variants and their Harmonization for Beyond 5G Systems

[ES] La estandarización de la Quinta Generación de redes móviles o 5G, ha concluido este año 2020. No obstante, en el año 2014 cuando la ITU empezó el proceso de estandarización IMT-2020, una de las principales interrogantes era cuál sería la forma de onda sobre la cual se construiría la capa física de esta nueva generación de tecnologías. El 3GPP se comprometió a entregar una tecnología candidata al proceso IMT-2020, y es así como dentro de este proceso de deliberación se presentaron varias formas de onda candidatas, las cuales fueron evaluadas en varios aspectos hasta que en el año 2016 el 3GPP tomó una decisión, continuar con CP-OFDM (utilizada en 4G) con numerología flexible. Una vez decidida la forma de onda, el proceso de estandarización continuó afinando la estructura de la trama, y todos los aspectos intrínsecos de la misma. Esta tesis acompañó y participó de todo este proceso. Para empezar, en esta disertación se evaluaron las principales formas de onda candidatas al 5G. Es así que se realizó un análisis teórico de cada forma de onda, destacando sus fortalezas y debilidades, tanto a nivel de implementación como de rendimiento. Posteriormente, se llevó a cabo una implementación real en una plataforma Software Defined Radio de tres de las formas de onda más prometedoras (CP-OFDM, UFMC y OQAM-FBMC), lo que permitió evaluar su rendimiento en términos de la tasa de error por bit, así como la complejidad de su implementación. Esta tesis ha propuesto también el uso de una solución armonizada como forma de onda para el 5G y sostiene que sigue siendo una opción viable para sistemas beyond 5G. Dado que ninguna de las forma de onda candidatas era capaz de cumplir por sí misma con todos los requisitos del 5G, en lugar de elegir una única forma de onda se propuso construir un transceptor que fuese capaz de construir todas las principales formas de onda candidatas (CP-OFDM, P-OFDM, UFMC, QAM-FBMC, OQAM-FBMC). Esto se consiguió identificando los bloques comunes entre las formas de onda, para luego integrarlos junto con el resto de bloques indispensables para cada forma de onda. La motivación para esta solución era tener una capa física que fuese capaz de cumplir con todos los aspectos del 5G, seleccionando siempre la mejor forma de onda según el escenario. Esta propuesta fue evaluada en términos de complejidad, y los resultados se compararon con la complejidad de cada forma de onda. La decisión de continuar con CP-OFDM con numerología flexible como forma de onda para el 5G se puede considerar también como una solución armonizada, ya que al cambiar el prefijo cíclico y el número de subportadoras, cambian también las prestaciones del sistema. En esta tesis se evaluaron todas las numerologías propuestas por el 3GPP sobre cada uno de los modelos de canal descritos para el 5G (y considerados válidos para sistemas beyond 5G), teniendo en cuenta factores como la movilidad de los equipos de usuario y la frecuencia de operación; para esto se utilizó un simulador de capa física del 3GPP, al que se hicieron las debidas adaptaciones con el fin de evaluar el rendimiento de las numerologías en términos de la tasa de error por bloque. Finalmente, se presenta un bosquejo de lo que podría llegar a ser la Sexta Generación de redes móviles o 6G, con el objetivo de entender las nuevas aplicaciones que podrían ser utilizadas en un futuro, así como sus necesidades. Completado el estudio llevado a cabo en esta tesis, se puede afirmar que como se propuso desde un principio la solución, tanto para el 5G como para beyond 5G, la solución es la armonización de las formas de onda. De los resultados obtenidos se puede corroborar que una solución armonizada permite alcanzar un ahorro computacional entre el 25-40% para el transmisor y del 15-25% para el receptor. Además, fue posible identificar qué numerología CP-OFDM es la más adecuada para cada escenario, lo que permitiría optimizar el diseño y despliegue de las redes 5G. Esto abriría la puerta a hacer lo mismo con el 6G, ya que en esta tesis se considera que será necesario abrir nuevamente el debate sobre cuál es la forma de onda adecuada para esta nueva generación de tecnologías, y se plantea que el camino a seguir es optar por una solución armonizada con distintas formas de onda, en lugar de solo una como sucede con el 5G.[CA] L'estandardització de la Quinta Generació de xarxes mòbils o 5G, ha conclòs enguany 2020. No obstant això, l'any 2014 quan la ITU va començar el procés d'estandardització IMT-2020, uns dels principals interrogants era quina seria la forma d'onda sobre la qual es construiria la capa física d'esta nova generació de tecnologies. El 3GPP es va comprometre a entregar una tecnologia candidata al procés IMT-2020, i és així com dins d'este procés de deliberació es van presentar diverses formes d'onda candidates, les quals van ser avaluades en diversos aspectes fins que l'any 2016 el 3GPP va prendre una decisió, continuar amb CP-OFDM (utilitzada en 4G) amb numerología flexible. Una vegada decidida la forma d'onda, el procés d'estandardització va continuar afinant la frame structure (no se m'ocorre nom en espanyol), i tots els aspectes intrínsecs de la mateixa. Esta tesi va acompanyar i va participar de tot este procés. Per a començar, en esta dissertació es van avaluar les principals formes d'onda candidates al 5G. És així que es va realitzar una anàlisi teòrica de cada forma d'onda, destacant les seues fortaleses i debilitats, tant a nivell d'implementació com de rendiment. Posteriorment, es va dur a terme una implementació real en una plataforma Software Defined Radio de tres de les formes d'onda més prometedores (CP-OFDM, UFMC i OQAM-FBMC), la qual cosa va permetre avaluar el seu rendiment en termes de la taxa d'error per bit, així com la complexitat de la seua implementació. Esta tesi ha proposat també l'ús d'una solució harmonitzada com a forma d'onda per al 5G i sosté que continua sent una opció viable per a sistemes beyond 5G. Atés que cap de les forma d'onda candidates era capaç de complir per si mateixa amb tots els requeriments del 5G, en compte de triar una única forma d'onda es va proposar construir un transceptor que fóra capaç de construir totes les principals formes d'onda candidates (CP-OFDM, P-OFDM, UFMC, QAM-FBMC, OQAM-FBMC). Açò es va aconseguir identificant els blocs comuns entre les formes d'onda, per a després integrar-los junt amb la resta de blocs indispensables per a cada forma d'onda. La motivació per a esta solució era tindre una capa física que fóra capaç de complir amb tots els aspectes del 5G, seleccionant sempre la millor forma d'onda segons l'escenari. Esta proposta va ser avaluada en termes de complexitat, i els resultats es van comparar amb la complexitat de cada forma d'onda. La decisió de continuar amb CP-OFDM amb numerología flexible com a forma d'onda per al 5G es pot considerar també com una solució harmonitzada, ja que al canviar el prefix cíclic i el número de subportadores, canvien també les prestacions del sistema. En esta tesi es van avaluar totes les numerologías propostes pel 3GPP sobre cada un dels models de canal descrits per al 5G (i considerats vàlids per a sistemes beyond 5G), tenint en compte factors com la mobilitat dels equips d'usuari i la freqüència d'operació; per a açò es va utilitzar un simulador de capa física del 3GPP, a què es van fer les degudes adaptacions a fi d'avaluar el rendiment de les numerologías en termes de la taxa d'error per bloc. Finalment, es presenta un esbós del que podria arribar a ser la Sexta Generació de xarxes mòbils o 6G, amb l'objectiu d'entendre les noves aplicacions que podrien ser utilitzades en un futur, així com les seues necessitats. Completat l'estudi dut a terme en esta tesi, es pot afirmar que com es va proposar des d'un principi la solució, tant per al 5G com per a beyond 5G, la solució és l'harmonització de les formes d'onda. dels resultats obtinguts es pot corroborar que una solució harmonitzada permet aconseguir un estalvi computacional entre el 25-40% per al transmissor i del 15-25% per al receptor. A més, va ser possible identificar què numerología CP-OFDM és la més adequada per a cada escenari, la qual cosa permetria optimitzar el disseny i desplegament de les xarxes 5G. Açò obriria la porta a fer el mateix amb el 6G, ja que en esta tesi es considera que serà necessari obrir novament el debat sobre quina és la forma d’onda adequada per a esta nova generació de tecnologies, i es planteja que el camí que s’ha de seguir és optar per una solució harmonitzada amb distintes formes d’onda, en compte de només una com succeïx amb el 5G.[EN] The standardization of the Fifth Generation of mobile networks or 5G is still ongoing, although the first releases of the standard were completed two years ago and several 5G networks are up and running in several countries around the globe. However, in 2014 when the ITU began the IMT-2020 standardization process, one of the main questions was which would be the waveform to be used on the physical layer of this new generation of technologies. The 3GPP committed to submit a candidate technology to the IMT-2020 process, and that is how within this deliberation process several candidate waveforms were presented. After a thorough evaluation regarding several aspects, in 2016 the 3GPP decided to continue with CP-OFDM (used in 4G) but including, as a novelty, the use of a flexible numerology. Once the waveform was decided, the standardization process continued to fine-tune the frame structure and all the intrinsic aspects of it. This thesis accompanied and participated in this entire process. To begin with, this dissertation evaluates the main 5G candidate waveforms. Therefore, a theoretical analysis of each waveform is carried out, highlighting its strengths and weaknesses, both at the implementation and performance levels. Subsequently, a real implementation on a Software Defined Radio platform of three of the most promising waveforms (CP-OFDM, UFMC, and OQAM-FBMC) is presented, which allows evaluating their performance in terms of bit error rate, as well as the complexity of its implementation. This thesis also proposes the use of a harmonized solution as a waveform for 5G and argues that it remains a viable option for systems beyond 5G. Since none of the candidate waveforms was capable of meeting on its own with all the requirements for 5G, instead of choosing a single waveform, this thesis proposes to build a transceiver capable of building all the main waveforms candidates (CP-OFDM, P-OFDM, UFMC, QAM-FBMC, OQAM-FBMC). This is achieved by identifying the common blocks between the waveforms and then integrating them with the rest of the essential blocks for each waveform. The motivation for this solution is to have a physical layer that is capable of complying with all aspects of beyond 5G technologies, always selecting the best waveform according to the scenario. This proposal is evaluated in terms of complexity, and the results are compared with the complexity of each waveform. The decision to continue with CP-OFDM with flexible numerology as a waveform for 5G can also be considered as a harmonized solution, since changing the cyclic prefix and the number of subcarriers, changes also the performance of the system. In this thesis, all the numerologies proposed by the 3GPP are evaluated on each of the channel models described for 5G (and considered valid for beyond 5G systems), taking into account factors such as the mobility of the user equipment and the operating frequency. For this, a 3GPP physical layer simulator is used, and proper adaptations are made in order to evaluate the performance of the numerologies in terms of the block error rate. Finally, a sketch of what could become the Sixth Generation of mobile networks or 6G is presented, with the aim of understanding the new applications that could be used in the future, as well as their needs. After the completion of the study carried out in this thesis, it can be said that, as stated from the beginning, for both 5G and beyond 5G systems, the solution is the waveform harmonization. From the results obtained, it can be corroborated that a harmonized solution allows achieving computational savings between 25-40% for the transmitter and 15-25% for the receiver. In addition, it is possible to identify which CP-OFDM numerology is the most appropriate for each scenario, which would allow optimizing the design and deployment of 5G networks. This would open the door to doing the same with 6G, i.e., a harmonized solution with different waveforms, instead of just one as in 5G.Flores De Valgas Torres, FJ. (2020). Study on Air Interface Variants and their Harmonization for Beyond 5G Systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/164442TESI