Duality of antennas and subcarriers in massive MIMO-OFDM downlink system

Massive multiple-input-multiple-output (MIMO) can significantly outperform conventional MIMO in terms of spectrum efficiency and link reliability. For massive MIMO, there are still theoretical and practical issues that have to be addressed. The capacity of the massive MIMO-orthogonal frequency division multiplexing (OFDM) downlink system is derived and analysed and the duality of antennas and subcarriers in such system is demonstrated analytically and by simulation. A detailed comparison between massive MIMO, massive MIMO-OFDM and MIMO-OFDM with large subcarriers is presented.Peer reviewe

MIMO-OFDM Based Energy Harvesting Cooperative Communications Using Coalitional Game Algorithm

This document is the Accepted Manuscript version. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, we consider the problem of cooperative communication between relays and base station in an advanced MIMO-OFDM framework, under the assumption that the relays are supplied by electric power drawn from energy harvesting (EH) sources. In particular, we focus on the relay selection, with the goal to guarantee the required performance in terms of capacity. In order to maximize the data throughput under the EH constraint, we model the transmission scheme as a non-transferable coalition formation game, with characteristic function based on an approximated capacity expression. Then, we introduce a powerful mathematical tool inherent to coalitional game theory, namely: the Shapley value (Sv) to provide a reliable solution concept to the game. The selected relays will form a virtual dynamically-configuredMIMO network that is able to transmit data to destination using efficient space-time coding techniques. Numerical results, obtained by simulating the EH-powered cooperativeMIMO-OFDMtransmission with Algebraic Space-Time Coding (ASTC), prove that the proposed coalitional game-based relay selection allows to achieve performance very close to that obtained by the same system operated by guaranteed power supply. The proposed methodology is finally compared with some recent related state-of-the-art techniques showing clear advantages in terms of link performance and goodput.Peer reviewe

Detection and decoding algorithms of multi-antenna diversity techniques for terrestrial DVB systems

This PhD dissertation analyzes the behavior of multi-antenna diversity techniques in broadcasting scenarios of TDT (terrestrial digital television) systems and proposes a low-complexity detection and decoding design for their practical implementation. For that purpose, the transmission-reception chains of the European DVB-T (Digital Video Broadcasting - Terrestrial) and DVB-T2 standards have been implemented over which diversity and MIMO (multiple-input multiple-output) techniques have been assessed through Monte Carlo simulations. On one hand, the most important multi-antenna diversity techniques such as CDD (cyclic delay diversity), Alamouti code-based SFBC (space-frequency block coding) and MRC (maximum ratio combining), have been evaluated in a DVB-T system over both fixed and mobile Rayleigh and Ricean channels. With the DVB-T2 standard release, multi-antenna processing has actually been introduced in digital television systems. The distributed SFBC configuration proposed in DVB-T2 is analyzed from a performance point of view considering different propagation conditions in an SFN (single frequency network). On the other hand, error-performance and detection complexity analyses of 2x2 FRFD (full-rate full-diversity) SFBCs are carried out for last-generation DTV (digital television) systems. The use of channel coding based on LDPC (low-density parity check) codes in new standards such as DVB-T2, involves a soft-output MAP (maximum a posteriori ) detection which results in an increase of the detection complexity. In order to study the FRFD codes behavior in such a BICM (bit-interleaved coded modulation) scheme, the Golden code, which achieves the maximum coding gain, and the Sezginer-Sari code, which has a lower inherent detection complexity as an expense of sacrificing performance gain, have been chosen. Using LSD (list sphere decoder) detection, BER (bit error rate) performance and computational cost results are provided for TDT scenarios. In order to overcome the variable complexity of the LSD, LFSD (list fixed-complexity sphere decoder) detection is proposed for practical implementations. A redesign of the previously proposed LFSD algorithm for spatial multiplexing MIMO systems has been performed for FRFD SFBCs with close-to-LSD performance. Furthermore, an analysis of the number of candidates is carried out in order to maximize the eficiency of the algorithm. Due to its fixed complexity, the novel algorithm can be fully pipelined making feasible a realistic implementation in chip.Esta tesis analiza el comportamiento de las técnicas de diversidad multiantena en escenarios de radiodifusión TDT (televisión digital terrestre) y propone un diseño de baja complejidad para la detección de códigos SFBC (space-frequency block coding ) que facilita una posible implementación práctica. Para ello, se ha implementado la cadena de transmisión-recepción de los estándares europeos DVB-T (Digital Video Broadcasting - Terrestrial ) y DVB-T2 como entorno de trabajo donde se han incluido y simulado diferentes técnicas de diversidad MIMO (multiple-input multiple-output ). Por un lado, se evalúan las técnicas de diversidad multiantena CDD ( cyclic delay diversity), SFBC con codi cación Alamouti y MRC (maximum ratio combining ) en escenarios fijos y móviles de canales tanto Rayleigh como Ricean para el sistema DVB-T. En DVB-T2, se analiza la tecnología multiantena propuesta por el estándar para diferentes escenarios de propagación dentro de redes SFN (single frequency network ). Por otro lado, se realiza un estudio sobre códigos FRFD (full-rate full-diversity ) SFBC para su posible inclusión en futuros estándares de televisión digital. El uso de codificaciones de canal más potentes, como los códigos LDPC (low-density parity check ), implica la utilización de una detección MAP (maximum a posteriori ) con salida soft, incrementando considerablemente la complejidad de la detección. Para realizar el correspondiente análisis de complejidad y rendimiento, se han escogidos dos códigos FRFD. Por un lado, el código Golden, que ofrece la máxima ganancia de código y, por otro, el código propuesto por Sezginer y Sari, que consigue reducir la complejidad de detección a costa de perder cierta ganancia de código. Se presentan resultados basados en curvas de BER (bit error rate) y número de operaciones sobre un sistema BICM (bit-interleaved coded modulation ) equivalente a DVB-T2 en escenarios TDT utilizando una detección LSD (list sphere decoder ). Para resolver el problema de la complejidad variable del algoritmo LSD, se realiza un rediseño del ya propuesto LFSD (list fixed-complexity sphere decoder ) para técnicas de multiplexación espacial considerando la estructura de los códigos FRFD SFBC. Asimismo, se evalúa el número de candidatos que ofrece un funcionamiento más eficiente con menor coste computacional. Los resultados de simulación basados en curvas de BER muestran rendimientos cercanos al detector LSD manteniendo el número de operaciones constante. Por lo tanto, este nuevo diseño permite su eficiente y práctica implementación en dispositivos reales.Doktoretza-tesi honen gai nagusia Lurreko Telebista Digitalerako antena anitzeko dibertsitate tekniken portaera ikertzea da, hartzailerako konplexutasun baxuko algoritmoen diseinua oinarri hartuta. Horretarako, Europako DVB-T eta DVB-T2 telebista digitaleko estandarren igorle-hartzaile kateen simulagailua inplementatzeaz gain, dibertsitate eta MIMO ( multipleinput multiple-output ) algoritmoak garatu eta aztertu dira. Lehenengo helburu gisa, CDD (cyclic delay diversity ), Alamouti kodean oinarritutako SFBC (space-frequency block coding ) eta MRC (maximum ratio combining ) teknikak ebaluatu dira Rayleigh eta Ricean ingurunetan, bai komunikazio nko zein mugikorretarako. Argitaratu berri den DVB-T2 estandarrak antena anitzeko prozesaketa telebista sistema digitalean sartu duenez, teknologia honen analisia egin da maiztasun bakarreko telebista sareetarako SFN (single frequency network ). Tesiaren helburu nagusia FRFD (full-rate full-diversity ) SFBC kodigoen ikerketa eta hauek telebista digitalaren estandar berrietan sartzea ahalbidetuko dituzten detekzio sistemen diseinua izan da. Kanalen kodi kazio indartsuagoak erabiltzeak, LDPC ( low-density parity check ) kodeak esaterako, MAP (maximum a posteriori ) algoritmoan oinarritutako soft irteeradun detektoreen erabilera dakar berekin, detekzioaren konplexutasuna areagotuz. Bi FRFD kode aukeratu dira errendimendu eta konplexutasun analisiak DVB-T2 bezalako BICM (bit-interleaved coded modulation ) sistemetan egiteko. Alde batetik, irabazi maximoa lortzen duen Golden kodea eta, bestetik, konplexutasun txikiagoa duen Sezginer eta Sarik proposatutako kodea erabili dira. Bit errore edo BER (bit error rate) tasan eta konputazio kostuan oinarrituta, emaitzak aurkeztu dira zerrenda dekodeatzaile esferikoa ( list sphere decoder, LSD) erabiliz. LSD-aren konplexutasun aldakorraren arazoa konpontzeko, ezpazio-multiplexazioko teknikarako LFSD (list xed-complexity sphere decoder ) algoritmoaren berdiseinua garatu da, FRFD SFBC kodeen egitura berezia kontuan hartuta. Algoritmoaren eraginkortasuna maximizatzeko kandidatuen zenbakia ebaluatzen da baita ere. LSD-en antzeko errendimendua duten BER gra ketan oinarritutako simulazio emaitzak aurkezten dira, eragiketa kopurua konstante eta LSD-arenaren baino murritzagoa mantenduz. Beraz, proposatutako diseinu eraginkorrak, FRFD SFBC antena anitzeko dibertsitatean oinarritutako eskemen inplementazioa ahalbidetu dezakete telebista digitalaren estandar berrietarako

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

Channel estimation and prediction in a pilot-less massive MIMO TDD using non-coherent DMPSK

A novel time division duplex massive MIMO technique is proposed based on performing a pilot-less channel estimation in the uplink (UL) utilizing reconstructed differentially encoded data. Spatial multiplexing and differentially encoded data is applied both in the UL and in the downlink (DL). In this system, a reference signal is the first one of the differentially encoded streams in the UL and DL, and the pilots for data estimation are avoided while maintaining spatial multiplexing capabilities. To improve the channel estimation we propose to use a linear Wiener filter and we also propose different symbols placing strategies in an OFDM grid. We also propose a detection improvement of the UL data utilizing the predicted channels. We perform an analysis of the MSE of the blind channel estimation using the differentially encoded data and analyze the symbol-error-rate for both the UL and the DL when channel aging is considered. The analysis is corroborated via numerical results and the proposed scheme is shown to outperform its pilot-based counterpart.This work was supported in part by the European Union Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie European Training Network (ETN) TeamUp5G under Grant 813391, and in part by the Spanish National Project IRENE-EARTH (MINECO/AEI/FEDER/UE) under Grant PID2020-115323RB-C33

Analysis and Design of Algorithms for the Improvement of Non-coherent Massive MIMO based on DMPSK for beyond 5G systems

Mención Internacional en el título de doctorNowadays, it is nearly impossible to think of a service that does not rely on wireless communications. By the end of 2022, mobile internet represented a 60% of the total global online traffic. There is an increasing trend both in the number of subscribers and in the traffic handled by each subscriber. Larger data rates, smaller extreme-to-extreme (E2E) delays and greater number of devices are current interests for the development of mobile communications. Furthermore, it is foreseen that these demands should also be fulfilled in scenarios with stringent conditions, such as very fast varying wireless communications channels (either in time or frequency) or scenarios with power constraints, mainly found when the equipment is battery powered. Since most of the wireless communications techniques and standards rely on the fact that the wireless channel is somehow characterized or estimated to be pre or post-compensated in transmission (TX) or reception (RX), there is a clear problem when the channels vary rapidly or the available power is constrained. To estimate the wireless channel and obtain the so-called channel state information (CSI), some of the available resources (either in time, frequency or any other dimension), are utilized by including known signals in the TX and RX typically known as pilots, thus avoiding their use for data transmission. If the channels vary rapidly, they must be estimated many times, which results in a very low data efficiency of the communications link. Also, in case the power is limited or the wireless link distance is large, the resulting signal-tointerference- plus-noise ratio (SINR) will be low, which is a parameter that is directly related to the quality of the channel estimation and the performance of the data reception. This problem is aggravated in massive multiple-input multiple-output (massive MIMO), which is a promising technique for future wireless communications since it can increase the data rates, increase the reliability and cope with a larger number of simultaneous devices. In massive MIMO, the base station (BS) is typically equipped with a large number of antennas that are coordinated. In these scenarios, the channels must be estimated for each antenna (or at least for each user), and thus, the aforementioned problem of channel estimation aggravates. In this context, algorithms and techniques for massive MIMO without CSI are of interest. This thesis main topic is non-coherent massive multiple-input multiple-output (NC-mMIMO) which relies on the use of differential M-ary phase shift keying (DMPSK) and the spatial diversity of the antenna arrays to be able to detect the useful transmitted data without CSI knowledge. On the one hand, hybrid schemes that combine the coherent and non-coherent schemes allowing to get the best of both worlds are proposed. These schemes are based on distributing the resources between non-coherent (NC) and coherent data, utilizing the NC data to estimate the channel without using pilots and use the estimated channel for the coherent data. On the other hand, new constellations and user allocation strategies for the multi-user scenario of NC-mMIMO are proposed. The new constellations are better than the ones in the literature and obtained using artificial intelligence techniques, more concretely evolutionary computation.This work has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie ETN TeamUp5G, grant agreement No. 813391. The PhD student was the Early Stage Researcher (ESR) number 2 of the project. This work has also received funding from the Spanish National Project IRENE-EARTH (PID2020-115323RB-C33) (MINECO/AEI/FEDER, UE), which funded the work of some coauthors.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidente: Luis Castedo Ribas.- Secretario: Matilde Pilar Sánchez Fernández.- Vocal: Eva Lagunas Targaron

Development and verification of semi-blind receiver structures for broadband wireless communication systems

The increasingly high demands for high data rate wireless communication services require spectrum- and energy-efficient solutions. In this thesis, a number of energy-efficient semi-blind receiver structures are proposed to perform Doppler spread estimation, channel estimation and equalisation for broadband wireless orthogonal frequency division multiplexing (OFDM) systems. A real-time wireless communication testbed is developed to verify the proposed semi-blind receiver structures. In the first contribution, a semi-blind Doppler spread estimation and Kalman filtering based channel estimation approach is proposed for wireless OFDM systems. A short sequence of reference data is carefully designed and applied as pilot symbols for Doppler spread estimation and channel estimation initialisation of the Kalman filter. Then the estimates of inter-carrier interference (ICI) caused by Doppler spread are gathered into the equivalent channel model and compensated for through channel equalisation, which dramatically reduces the computational complexity. The simulation results show that the proposed approach outperforms the conventional pilot aided Doppler spread and channel estimation schemes. In the second contribution, a semi-blind Doppler spread estimation and independent component analysis (ICA) based equalisation scheme aided by non-redundant precoding is proposed for wireless multiple-input multiple-output (MIMO) OFDM systems. A number of reference data sequences are selected from a pool of orthogonal sequences for two purposes. First, the reference data sequences are superimposed in the source data sequences through non-redundant linear precoding to enable the Doppler spread estimation by minimising the sum cross-correlation between the compensated signals and the rest of the orthogonal sequences in the pool. Second, the same reference data sequences are applied to eliminate the phase and permutation ambiguity in the ICA equalised signals. Simulation results show that the proposed semi-blind MIMO OFDM system can achieve a bit error rate (BER) performance which is close to the ideal case with perfect channel state information (CSI). In the third contribution, a real-time wireless communication testbed is developed with a vector signal generator, a vector signal analyser and a pair of antennas, to verify the effectiveness of the proposed receiver structures over the air in different environments such as Reverberation chamber and office area. Measurement results show a good match with simulation results. Also, a pilot is employed for three purposes at a semi-blind receiver: time synchronisation, Doppler spread estimation and Kalman filtering initialisation, which is an extension of the work in the first contribution

Single-Frequency Network Terrestrial Broadcasting with 5GNR Numerology

L'abstract è presente nell'allegato / the abstract is in the attachmen