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Mondragon University | Mu · Signal Theory and Communications

This work introduces the design and assessment of a voice-controlled elevator system aimed at facilitating touchless interaction between users and hardware, thereby minimising contact and improving accessibility for individuals with disabilities. The research distinguishes three distinct deployment scenarios – on cloud, on edge and embedded – with...

Reconfigurable Intelligent Surfaces can change their reflective response to adapt to changes in the communication channel, where such response is obtained by modifying the reflection coefficient of each of the unit cells that make up the surface. The paper analyzes, through electromagnetic simulations and actual PCB designs, the viability and perfo...

Train-to-train (T2T) communication is proposed as an auxiliary safety-guaranteed measure for railway communications. Vehicular communication standards have been supporting railway use cases and T2T communications. It is essential to consider the propagation characteristics of railway environments with dedicated T2T channel models for simulation and...

Communications in the mmWave spectrum are gaining relevance in the last years as they are a promising candidate to cope with the increasing demand of throughput and latency in different use cases. Nowadays several efforts have been carried out to characterize the propagation medium of these signals with the aim of designing their corresponding comm...

Power cables are critical assets for the reliable operation of the grid. The cable lifetime is generally estimated from the conductor temperature and associated lifetime reduction. However, these tasks are intricate due to the complex physics-of-failure (PoF) degradation mechanism of the cable. This is further complicated with the different sources...

The emergence of new electricity and energy systems opens the way to novel reliability monitoring and maintenance planning strategies. In smart grids, the increased connection between various power systems enables a resilient grid operation. Similarly, the proliferation of data sources across the grid creates opportunities for a more accurate maint...

The use of deterministic lifetime models may be appropriate for transformer lifetime planning if they are operated with regular power and temperature profiles. However, if the application context includes dynamic operation profiles and stochastic phenomena, the transformer health state estimation is no longer deterministic and new health state esti...

Stochastic Activity Network (SAN) is a flexible formalism that permits performing reliability and prognostics analysis of complex degrading systems. However, their use for the analysis of high reliability equipment including fast evolving and degrading mechanisms requires long simulation times and large hardware resources. This paper presents a Fie...

Wireless communications offer significant benefits over wired communications, which has increased their popularity in industrial applications. Nevertheless, the existing wireless standard technologies do not satisfy the requirements demanded by the most critical industrial applications and, thus, wired communications cannot be directly replaced by...

The online RUL estimation of underground cables and their reliability analysis requires obtaining the cable failure time probability distribution. MC simulations of complex thermal heating and electro-thermal degradation models can be employed for this analysis, but uncertainties need to be considered in the simulations, to produce accurate RUL exp...

A spectrum handoff or channel switching mechanism for Industrial Wireless Sensor and Actuator Networks (IWSAN) which is capable of detecting interference and hopping to another channel (in the same or other band) in a deterministic time is proposed. This is possible because the spectrum handoff strategy detects interference in the MAC layer, and ca...

Industrial control applications require real-time communication systems with time-critical and safety-critical features, as well as the ability to operate in harsh propagation environments. This means that data communications need to be bounded both in time and reliability domains, while dealing with severe interference coming from other wireless c...

We analyse some of the candidates for modulations for 5G: FBMC-OQAM, GFDM-OQAM, and WCP-COQAM. Unlike most of the related bibliographies, which are oriented to mobile communications, our research is focused on 5G in cognitive radio based industrial wireless communications. According to the ultrareliability and low-latency requirements of industrial...

The main challenges for current industrial wireless solutions are the stringent real-time requirements of industrial automation applications and the harsh propagation channel conditions in this kind of scenarios. Most of the current industrial wireless communications are based on existing standards like IEEE 802.11, IEEE 802.15.1 or IEEE 802.15.4 a...

In this paper a low-complexity cyclostationary-based modulation classifier is presented, which is capable of distinguishing between OFDM, GFSK and QPSK modulations. The classifier computes and analyses the cyclic autocorrelation of the received signals in an implementation-efficient manner. Instead of computing a high number of values of the cyclic...

This chapter presents an FPGA-based SDR platform which serves as a proof-of-concept for cognitive radio techniques. The platform is based on a fully reconfigurable hardware and operates as a 12.8 Mbps RF-to-Ethernet bridge in the Industrial, Scientific, and Medical (ISM) bands of 868 MHz and 2.45 GHz. The data-processing algorithms of the platform...

In this paper the integration of a Dynamic Spectrum Access (DSA) technique in a wideband cognitive RF-Ethernet bridge for industrial control applications is presented. The proposed DSA scheme is based on two spectrum sensing algorithms and it allows avoiding any possible interference due to external communication systems or industrial equipments. T...

The evaluation of Cognitive Radio (CR) for Wireless Sensor and Actuator Networks (WSANs) in industrial wireless automation applications is presented in this contribution. Current wireless solutions do not ensure enough performance for hard real-time and reliability requirements, based on time-critical data traffic. These industrial applications are...

Designing energy-efficient cognitive radio transceivers requires joint optimization of medium access control and the physical layer implementation. In this paper we show an energy efficiency optimization strategy for IEEE 802.11n compliant transceivers in terms of energy consumed by the receiver per successfully received bit. To this end, we propos...

The multiuser MIMO environment enables the communication between a base-station and multiple users with several antennas. In such a scenario, the use of precoding techniques is required in order to detect the signal at the users' terminals without any cooperation between them. This contribution presents various designs and hardware implementations...

The multiuser MIMO environment enables the communication between a base-station and multiple users with several antennas. In such a scenario, the use of precoding techniques is required in order to detect the signal at the users' terminals without any cooperation between them. This contribution presents various designs and hardware implementations...

A new statistical model for describing indoor wideband MIMO channels in train carriages is presented in this paper. Starting from a 3D ray tracing model, the most important parameters to obtain the wideband MIMO channel are investigated. The results are then used following WINNER methodology to create the channel model. To justify and validate this...

The nonlinear vector precoding (VP) technique has been proven to achieve close-to-capacity performance in multiuser multiple-input multiple-output (MIMO) downlink channels. The performance benefit with respect to its linear counterparts stems from the incorporation of a perturbation signal that reduces the power of the precoded signal. The computat...

Vector precoding enables non-cooperative signal acquisition in the multi-user broadcast channel. The performance advantage with respect to the more straightforward linear precoding algorithms comes as a consequence of an added perturbation vector, which enhances the properties of the precoded signal. Nevertheless, the computation of the perturbatio...

In this article, a novel detector design is proposed for orthogonal frequency division multiplexing (OFDM) systems over frequency selective and time varying channels. Namely, we focus on systems with large OFDM symbol lengths where design and complexity constraints have to be taken into account and many of the existing ICI reduction techniques can...

Modern terrestrial television broadcasting, which is based on orthogonal frequency division multiplexing (OFDM) transmission, suffers from inter-carrier interference (ICI) in time-varying channels, due to the loss of orthogonality among subcarriers. This ICI term, which cannot be neglected in middle and high mobility scenarios, can even offer incre...

A two-hop non-regenerative multiuser multiple input multiple output (MIMO) relaying scenario is analysed in this paper, where the main design challenge resides in the selection of the interdependent precoding and relaying matrices. Several linear and non-linear approaches have been proposed for amplify-and-forward (AF) relaying, the best performanc...

Last-generation and future wireless communication standards, such as DVB-T2 or DVB-NGH, are including multi-antenna transmission and reception in order to increase bandwidth efficiency and receiver robustness. The main goal is to combine diversity and spatial multiplexing in order to fully exploit the multiple-input multiple-output (MIMO) channel c...

Precoding techniques are used in the downlink of multiuser multiple-input multiple-output (MIMO) systems in order to separate the information data streams aimed at scattered user terminals. Vector precoding (VP) is one of the most promising non-linear precoding schemes, which achieves a performance close to the optimum albeit impractical dirty pape...

In this paper we consider the design of minimum mean square error (MMSE) transceivers for non-regenerative multiuser multiple-input multiple-output (MIMO) relay systems, where the main challenge resides in the joint optimal design of the precoder to be used at the base station and the relaying algorithms. We propose the use of non-linear precoding...

A two-hop multiuser multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay scenario is analyzed in this paper, where the main design challenge resides on the selection of the interdependent precoding and relaying matrices. After analyzing the optimal joint iterative linear design of the precoding and relaying matrices, two simpler non...

In recent years the interest in developing efficient algorithms for the multiple-input multiple-output (MIMO) broadcast channel has arisen. Vector precoding (VP) techniques have shown very promis-ing performance results, but the perturbation process inherent in these type of non-linear systems hinders their efficient implemen-tation. The key to ach...

Recent and next-generation wireless broadcasting standards, such as DVB-T2 or DVB-NGH, are considering distributed multi-antenna transmission in order to increase bandwidth efficiency and signal quality. Full-rate full-diversity (FRFD) space-time codes (STC), such as the Golden code, have been reported to be excellent candidates, being their main d...

This contribution analyzes the architecture design and FPGA implementation of high-throughput multiuser vector precoders. The most complex task of such precoders, i.e. the search of the perturbing vector over an infinite lattice, has been carried out by means of two tree search algorithms: a novel fully-pipelined complex-valued K-Best scheme and a...

This paper proposes a novel framework for reducing the inter-carrier interference (ICI) caused by time-varying channels in mobile OFDM systems. The proposed ICI suppressing scheme is based on the application of the sum-product (SP) algorithm to a factor graph (FG) representing the joint a posteriori probability (APP) of the transmitted symbols. Sim...

We propose a new pilot structure for inter-carrier interference (ICI) estimation and compensation in order to improve the performance of the forthcoming Digital Video Broadcasting-Next Generation Handheld (DVB-NGH) standard in mobile environments. Although classical pilot patterns and channel estimation techniques achieve good performance in fixed...

Besides the optimal but impractically complex dirty paper coding (DPC), linear precoding and vector precoding (VP) have been proposed for the vector broadcast channel (BC). Linear precoding is simple, as only a linear transform is applied to the data signals, whereas VP necessitates a closest-point search in a lattice to find the perturbation signa...

This paper focuses on the challenging problem of signal re-ception for orthogonal frequency division (OFDM) systems in high mobility environments. A novel framework based on the well-known belief propagation (BP) algorithm is pro-posed for joint inter-carrier interference (ICI) cancellation, signal detection and channel decoding. The performance of...

In the multiuser MIMO broadcast channel, the use of precoding techniques is required in order to detect the signal at the users' terminals without any cooperation between them. This contribution presents the design and hardware implementation of a high-capacity precoder based on vector perturbation. The most challenging part of the vector precoding...

This paper analyzes the impact of inter-carrier interference (ICI) compensation on the physical layer of DVB-T2, the new digital terrestrial television standard. We compare the performance of a well-known low complexity soft demapper for different time-interleaving depths and code rates in several realistic mobile scenarios. This paper further pres...

The goal of the future terrestrial and mobile digital video broad-casting standards is to combine diversity and spatial multiplexing in order to fully exploit the multiple-input multiple-output (MIMO) channel capacity. Full-rate full-diversity (FR-FD) space-time codes (STC) such as the Golden code, that maximize the rate preserving the diversity ga...

As most state-of-the-art terrestrial transmissions standards, DVB-T2 uses orthogonal frequency division multiplexing (OFDM) as modulation scheme. For performing channel estimation and equalization normally so-called frequency domain pilots are employed. As pilots are known information to the receiver, they do not carry any information and are thus...

The authors would like to thank the Spanish Government for the funding received through the research projects FURIA and FURIA2, as well as to all the partners of the FURIA consortium.

Focusing on densely deployed wireless sensor networks, this paper presents a novel method for joint source-channel-network coding of distributed correlated sources through multiple access relay channels. In such networks, the role of intermediate sensors as relay nodes permits to achieve enhanced end-to-end error performance and increased spatial d...

This paper presents the design, simulation and performance of a low-cost echo canceler for its application to on-channel repeaters in single frequency DVB-T networks. In these devices an echo canceler is required in order to avoid the coupling echoes produced between transmission and reception antennas. The designed echo canceler is based on an ada...

A fixed-throughput Wiener filter vector precoding (VP) approach specially suitable for hardware implementation in field programable gate array (FPGA) devices is introduced in this paper. The lattice decoding algorithm, which is based on the sphere decoder (SD) lattice search, performs in its first stage a reordering of the matrix to be used for the...

The development of a fingerprint verification system on a low-cost embedded platform still remains an open issue in nowadays biometrics. In order to shed light on this field, the contribution shown in this manuscript describes a lowcost fingerprint minutiae extraction and matching system based on a Spartan3 field-programmable gate array (FPGA) with...

A fixed-throughput vector precoding (VP) approach specially suit-able for hardware implementation in field programmable gate array (FPGA) devices is presented in this paper. The algorithm, which is based on the sphere encoder (SE), is divided into two main stages: at the preprocessing stage, the columns of the precoding matrix are ordered following...

This article describes the design and implementation of a channel equalizer for a terrestrial digital television (digital video broadcasting-terrestrial, DVB-T) on-channel repeater, namely gap-filler. Two are the benefits of including this equalizer in a repeater setup: on one hand, the transmitted signal requires a lower dynamic range and its degr...

Analytical extrinsic information transfer (EXIT) func-tions provide an accurate and flexible method to analyze and calculate the performance of iterative linear multiple input-multiple output (MIMO) receivers through their decomposi-tion into independent elementary blocks, such as the linear combiner or the demapper. These analytical functions have...

This contribution analyzes the integration of the sphere decoder (SD) in a complete field-programmable gate array (FPGA)-based real-time multiple input-multiple output (MIMO) platform. The algorithm achieves the performance of the maximum likelihood detector (MLD) with reduced complexity. However, its non-deterministic complexity, de-pending on the...

This contribution describes a MIMO simulation and validation platform suitable for a progressive implementation of real-time signal processing algorithms. We describe a platform that allows sharing Matlab, simulated VHDL and hardware designs while transmitting through a real MIMO channel. The applicability and first results of this platform are sho...

Multiple-input multiple-output (MIMO) signal processing combined with orthogonal frequency division multiplexing (OFDM) is a widely accepted solution to achieve the high bit rates that new communication standards require in frequency-selective wireless channels. In recent years, a new frequency-domain equalized (FDE) cyclic-prefixed single-carrier...