Spatial modulation schemes and modem architectures for millimeter wave radio systems

The rapid growth of wireless industry opens the door to several use cases such as internet of things and device-to-device communications, which require boosting the reliability and the spectral efficiency of the wireless access network, while reducing the energy consumption at the terminals. The vast spectrum available in millimeter-wave (mmWave) frequency band is one of the most promising candidates to achieve high-speed communications. However, the propagation of the radio signals at high carrier frequencies suffers from severe path-loss which reduces the coverage area. Fortunately, the small wavelengths of the mmWave signals allow packing a large number of antennas not only at the base station (BS) but also at the user terminal (UT). These massive antenna arrays can be exploited to attain high beamforming and combining gains and overcome the path-loss associated with the mmWave propagation. In conventional (fully digital) multiple-input-multiple-output (MIMO) transceivers, each antenna is connected to a specific radio-frequency (RF) chain and high resolution analog-to-digital-converter. Unfortunately, these devices are expensive and power hungry especially at mmWave frequency band and when operating in large bandwidths. Having this in mind, several MIMO transceiver architectures have been proposed with the purpose of reducing the hardware cost and the energy consumption. Fully connected hybrid analog and digital precoding schemes were proposed in with the aim of replacing some of the conventional RF chains by energy efficient analog devices. These fully connected mapping requires many analog devices that leads to non-negligible energy consumption. Partially connected hybrid architectures have been proposed to improve the energy efficiency of the fully connected transceivers by reducing the number of analog devices. Simplifying the transceiver’s architecture to reduce the power consumption results in a degradation of the attained spectral efficiency. In this PhD dissertation, we propose novel modulation schemes and massive MIMO transceiver design to combat the challenges at the mmWave cellular systems. The structure of the doctoral manuscript can be expressed as In Chapter 1, we introduce the transceiver design challenges at mmWave cellular communications. Then, we illustrate several state of the art architectures and highlight their limitations. After that, we propose scheme that attains high-energy efficiency and spectrum efficiency. In chapter 2, first, we mathematically describe the state of the art of the SM and highlight the main challenges with these schemes when applied at mmWave frequency band. In order to combat these challenges (for example, high cost and high power consumption), we propose novel SM schemes specifically designed for mmWave massive MIMO systems. After that, we explain how these schemes can be exploited in attaining energy efficient UT architecture. Finally, we present the channel model, systems assumptions and the transceiver devices power consumption models. In chapter 3, we consider single user SM system. First, we propose downlink (DL) receive SM (RSM) scheme where the UT can be implemented with single or multiple radio-frequency chains and the BS can be fully digital or hybrid architecture. Moreover, we consider different precoders at the BS and propose low complexity and efficient antenna selection schemes for narrowband and wideband transmissions. After that, we propose joint uplink-downlink SM scheme where we consider RSM in the DL and transmit SM (TSM) in the UL based on energy efficient hybrid UT architecture. In chapter 4, we extend the SM system to the multi-user case. Specifically, we develop joint multi-user power allocation, user selection and antenna selection algorithms for the broadcast and the multiple access channels. Chapter 5 is presented for concluding the thesis and proposing future research directions.Considerando los altos requerimientos de los servicios de nueva generación, las infraestructuras de red actual se han visto obligadas a evolucionar en la forma de manejar los diferentes recursos de red y computación. Con este fin, nuevas tecnologías han surgido para soportar las funcionalidades necesarias para esta evolución, significando también un gran cambio de paradigma en el diseño de arquitecturas para la futura implementación de redes.En este sentido, este documento de tesis doctoral presenta un análisis sobre estas tecnologías, enfocado en el caso de redes inter/intra Data Centre. Por consiguiente, la introducción de tecnologías basadas en redes ópticas ha sido estudiada, con el fin de identificar problemas actuales que puedan llegar a ser solucionados mediante el diseño y aplicación de nuevas técnicas, asimismo como a través del desarrollo o la extensión de los componentes de arquitectura de red.Con este propósito, se han definido una serie de propuestas relacionadas con aspectos cruciales, así como el control de dispositivos ópticos por SDN para habilitar el manejo de redes híbridas, la necesidad de definir un mecanismo de descubrimiento de topologías ópticas capaz de exponer información precisa, y el analizar las brechas existentes para la definición de una arquitectura común en fin de soportar las comunicaciones 5G.Para validar estas propuestas, se han presentado una serie de validaciones experimentales por medio de escenarios de prueba específicos, demostrando los avances en control, orquestación, virtualización y manejo de recursos con el fin de optimizar su utilización. Los resultados expuestos, además de corroborar la correcta operación de los métodos y componentes propuestos, abre el camino hacia nuevas formas de adaptar los actuales despliegues de red respecto a los desafíos definidos en el inicio de una nueva era de las telecomunicaciones.Postprint (published version

Receive antenna selection and hybrid precoding for receive spatial modulation in massive MIMO systems

©2018 IEEE. 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.Recently, a receive spatial modulation (RSM) for massive multiple-input-multiple-output operating in millimeter wave (mmWave) was introduced with the purpose of simplifying user terminal circuit by employing only one radio-frequency chain and attaining high spectral efficiency by exploiting the receive spatial dimension. However, when RSM is applied in a mmWave channel, it demands a challenging receive antenna selection (RAS) procedure. On the other hand, the power consumption at the transmitter side is high when a full digital (FD) precoder is envisioned. We consider the joint problem of RAS and precoder designs based low complexity hybrid architecture. For the sake of simplicity, we divide this problem into two subproblems. First, we design the RAS assuming FD precoder, and then, we design the hybrid precoder. We propose two novel and efficient RAS methods. First, we formulate the RAS as non-convex optimization problem. Then, we convert it into a convex optimization problem by introducing novel lower bounds and relaxing non-convex constraints. Second, we provide sequential algorithms that approach the optimal selection where we (add/remove) one (good/poor) antenna per iteration. We propose novel zero forcing hybrid precoder based convex optimization that maximizes the received power. We prove that the proposed precoder is optimal when the channel is highly spatially sparse. The proposed designs have been compared with the best known methods in terms of average mutual information and energy efficiency showing significant improvements.Peer ReviewedPostprint (author's final draft

MMSE precoding for receive spatial modulation in large MIMO systems

©2018 IEEE. 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.Receive spatial modulation (RSM) schemes enable simple and energy efficient multiple-input-multiple-output (MIMO) transceivers and yet attain high spectral efficiency, which renders them promising schemes for millimeter wave (mmWave) communication in massive MIMO systems. When these schemes are designed to include zero forcing (ZF) precoders, performance can be impaired in the presence of highly spatially correlated channels. Extending these schemes for minimum mean square error (MMSE) precoding is not trivial due to the hardware constraints of the energy efficient user terminal architecture. In this paper, we adapt the MMSE precoder to the low complexity RSM architecture and develop detection methods for the spatial and modulation symbols. The proposed MMSE RSM scheme with total and per-antenna power constraints have been compared with ZF RSM in terms of average and outage mutual information by simulations showing superior gain for mmWave channels.Peer ReviewedPostprint (author's final draft

Receive spatial modulation for massive MIMO systems

©2017 IEEE. 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 downlink of a massive multiple-input-multiple-output (MIMO) single user transmission system operating in the millimeter wave outdoor narrowband channel environment. We propose a novel receive spatial modulation architecture aimed to reduce the power consumption at the user terminal, while attaining a significant spectral efficiency and low bit error rate. The energy consumption reduction is obtained through the use of analog devices (amplitude detector), which reduces the number of radio frequency chains and analog to- digital-converters (ADCs). The base station transmits spatial and modulation symbols per channel use. We show that the optimal spatial symbol detector is a threshold detector that can be implemented by using one bit ADC. We derive closed form expressions for the detection threshold at different signal-to noise-ratio (SNR) regions. We derive expressions for the average bit error probability in the presence and absence of the threshold estimation error showing that a small number of pilot symbols is needed. A performance comparison is done between the proposed system and fully digital MIMO showing that a suitable constellation selection can reduce the performance gap.Peer ReviewedPostprint (author's final draft

Wideband receive spatial modulation with time domain pre-equalizer for large MIMO systems

© 2018 IEEE. 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 worksReceive spatial modulation (RSM) schemes are promising for massive multiple-input-multiple-output (MIMO) systems at millimeter wave (mmWave) bands because they require reduced complexity and low consumption hardware at the user terminal and exploit the receive spatial dimension to attain high spectral efficiency. To the best of our knowledge, these schemes have been developed for narrowband transmission. In this paper, we adapt RSM schemes for outdoor wideband mmWave massive MIMO systems. We consider the downlink of a single user system operating with single carrier RSM and design a low complexity time-domain finite impulse response pre-equalizer to combat the intersymbol interference caused by the wideband transmission, assuming imperfect channel knowledge. We show that receive antenna selection (RAS) is necessary for attaining high spectral efficiency and we suggest fast and efficient RAS algorithm. Simulation results show that the proposed RSM scheme achieves comparable spectral efficiency to the fully digital orthogonal frequency division multiplexing MIMO system with superior energy efficiency.Peer ReviewedPostprint (author's final draft

Energy efficient transmit-receive spatial modulation for uplink-downlink large-scale MIMO systems

© 2019 IEEE. 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.Energy efficient spatial modulation-aided uplink and downlink designs for future millimeterwave (mmWave) large-scale multiple-input multiple-output (MIMO) systems are considered. Two novel uplink transceivers are proposed with the aim of considerably reducing the energy consumption at the user terminal, while achieving high spectral efficiency both in uplink and downlink transmissions. System performance is investigated using both stochastic and deterministic channels emulating real world urban scenarios.Peer ReviewedPostprint (published version

Downlink multi-user massive MIMO transmission using receive spatial modulation

In this paper, we consider the downlink of a multi-user multiple-input-multiple-output system operating at the millimeter wave band in an outdoor environment. In this band, receive spatial modulation (RSM) schemes have been shown to achieve good spectral efficiency-energy consumption trade-off for the single-user case by exploiting new transceiver architectures that use a single radio-frequency (RF) chain at the user terminal (UT). In this work, we propose a novel RSM scheme for multiple RF chains at the UT. With the goal of maximizing the spectral efficiency (SE), we consider analog switches at the UT that select which antennas are active. To minimize the power consumption at the BS, we include analog switches that control the ON/OFF status of RF chains such that the SE is higher than a given threshold. Moreover, we extend the RSM concept to multiple users transmission. Specifically, we propose an algorithm that jointly optimizes the number of users, set of antennas and transmit power allocated to each user to maximize the sum SE. Simulation results show that RSM outperforms conventional modulation (no spatial symbols are transmitted) in terms of spectral and energy efficiency. Moreover, the proposed algorithms tightly approach the exhaustive search and outperform the prior art in terms of performance and convergence.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Programme through the Marie Sklodowzka-Curie under Grant 641985, in part by the Project 5G&B RUNNER-UPC (AEI/FEDER, UE) under Grant TEC2016-77148-C2-1-R, and in part by the Catalan Government under Grant 2017 SGR 578-AGAUR.Peer ReviewedPostprint (author's final draft

Receive antenna selection and hybrid precoding for receive spatial modulation in massive MIMO systems

©2018 IEEE. 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.Recently, a receive spatial modulation (RSM) for massive multiple-input-multiple-output operating in millimeter wave (mmWave) was introduced with the purpose of simplifying user terminal circuit by employing only one radio-frequency chain and attaining high spectral efficiency by exploiting the receive spatial dimension. However, when RSM is applied in a mmWave channel, it demands a challenging receive antenna selection (RAS) procedure. On the other hand, the power consumption at the transmitter side is high when a full digital (FD) precoder is envisioned. We consider the joint problem of RAS and precoder designs based low complexity hybrid architecture. For the sake of simplicity, we divide this problem into two subproblems. First, we design the RAS assuming FD precoder, and then, we design the hybrid precoder. We propose two novel and efficient RAS methods. First, we formulate the RAS as non-convex optimization problem. Then, we convert it into a convex optimization problem by introducing novel lower bounds and relaxing non-convex constraints. Second, we provide sequential algorithms that approach the optimal selection where we (add/remove) one (good/poor) antenna per iteration. We propose novel zero forcing hybrid precoder based convex optimization that maximizes the received power. We prove that the proposed precoder is optimal when the channel is highly spatially sparse. The proposed designs have been compared with the best known methods in terms of average mutual information and energy efficiency showing significant improvements.Peer Reviewe

MMSE precoding for receive spatial modulation in large MIMO systems

©2018 IEEE. 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.Receive spatial modulation (RSM) schemes enable simple and energy efficient multiple-input-multiple-output (MIMO) transceivers and yet attain high spectral efficiency, which renders them promising schemes for millimeter wave (mmWave) communication in massive MIMO systems. When these schemes are designed to include zero forcing (ZF) precoders, performance can be impaired in the presence of highly spatially correlated channels. Extending these schemes for minimum mean square error (MMSE) precoding is not trivial due to the hardware constraints of the energy efficient user terminal architecture. In this paper, we adapt the MMSE precoder to the low complexity RSM architecture and develop detection methods for the spatial and modulation symbols. The proposed MMSE RSM scheme with total and per-antenna power constraints have been compared with ZF RSM in terms of average and outage mutual information by simulations showing superior gain for mmWave channels.Peer Reviewe

Wideband receive spatial modulation with time domain pre-equalizer for large MIMO systems

© 2018 IEEE. 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 worksReceive spatial modulation (RSM) schemes are promising for massive multiple-input-multiple-output (MIMO) systems at millimeter wave (mmWave) bands because they require reduced complexity and low consumption hardware at the user terminal and exploit the receive spatial dimension to attain high spectral efficiency. To the best of our knowledge, these schemes have been developed for narrowband transmission. In this paper, we adapt RSM schemes for outdoor wideband mmWave massive MIMO systems. We consider the downlink of a single user system operating with single carrier RSM and design a low complexity time-domain finite impulse response pre-equalizer to combat the intersymbol interference caused by the wideband transmission, assuming imperfect channel knowledge. We show that receive antenna selection (RAS) is necessary for attaining high spectral efficiency and we suggest fast and efficient RAS algorithm. Simulation results show that the proposed RSM scheme achieves comparable spectral efficiency to the fully digital orthogonal frequency division multiplexing MIMO system with superior energy efficiency.Peer Reviewe