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© 2020 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. We address the evaluation of dynamic (estimation-based) user-decoding order in successive interference cancellation (SIC) in a proof-of-concept multiple access satellite setting in which many code-division multiple access users employ non-orthogonal spreading codes and the same encoder. We consider the practical setting where user symbol energies, unknown to the receiver, are estimated by preamble cross-correlations. Thereafter, SIC proceeds in non-increasing order of the former estimates. In contrast with small networks evaluated in the literature, we analyze the large-user regime and derive a simple system model to analyze the asymptotic network performance. Monte Carlo simulations validate our infinite-user analysis for hundreds of users and report the benefits of their application. Work supported in part by Agencia Estatal de Investigación (AEI, Spain) and by European Regional Development Fund (ERDF) through project WIN-TER (TEC2016-76409-C2-1-R) and project RODIN (PID2019-105717RB-C22), and in part by the Catalan administration (AGAUR) under Grant 2017SGR 578 and predoctoral Fellowship 2019FIB1 00085

The Gaussian multiple access channel under asymptotically many code-division-multiple-access users and successive interference cancellation (SIC) is investigated in this work. Users transmit n-symbol packets and select their encoding rate as a function of their perfectly known channel gains. We address a theoretical study whereby the performance of employed encoding schemes is described by achievable second-order coding rates at blocklength n. Our contribution is twofold. Firstly, we formulate and solve an optimal control problem to maximize the asymptotic user-aggregate spectral efficiency (SE) for a one-iteration SIC. Secondly, we analyze the user-limit behavior of two-iteration SIC and propose a complexity-affordable vector optimization to maximize the user-aggregate SE. Reported results quantify the benefit of adopting a two-iteration SIC versus the blocklength. This work has been supported by the Spanish Ministry of Science and Innovation through projects WINTER (TEC2016-76409-C2-1-R / AEI / FEDER, UE) and RODIN (PID2019-105717RB-C22 / AEI / 10.13039/501100011033) and by the Catalan Government (AGAUR) under grant 2017 SGR 578. F. Molina is also supported by Fellowship 2020FI_B2 00062 (Secretary for Universities and Research of the Generalitat de Catalunya and the European Social Fund).

The energy allocation problem in a massive access setting under iterative successive interference cancellation (SIC) is undertaken in this work. The classic one-iteration SIC still has room for improvement when the channel coding schemes adopted are non-error free. In this work, we investigate a satellite return link in which transmitters employ the same physical layer and transmission protocol: a given encoder, and spreading-based nonorthogonal multiple access. Leveraging iterative SIC, the gateway is endowed with strong interference suppression potential to deal with many uncoordinated transmissions. We elaborate on the interplay between energy and reliability for all users by designing an energy allocation with minimum energy expenditure when the iterative SIC receiver performs two decoding attempts per user. We resort to the user-asymptotic regime to address the randomness in the multi-feature system model of two-iteration SIC, which has turned the analysis into a deterministic one. We formulate our final design as a vector optimization aided by tools from the calculus of variations. We show the competitive performance achieved by the designed allocation, specially under encoders associated with short-length codes. We also assess our analysis by simulating a low-level SIC implementation. Work supported in part by Agencia Estatal de Investigacion (AEI, Spain) and by European Regional Development Fund (ERDF) through project RODIN (PID2019-105717RB-C22), and in part by the Catalan administration (AGAUR) under Grant 2017 SGR 578 and Fellowship 2020FI B2 00062.

The energy-aware design of fully analog precoders and combiners is investigated in this paper. To that aim, we consider a millimeter-wave short-packet communication scenario where power consumption and hardware complexity constitute relevant factors. User terminals employ a single channel encoder and, at hardware level, they implement analog architectures that combine phase shifters and switches. Additionally, transmitting terminals also leverage a power control system. An energy efficiency figure of merit is considered, and its optimization subject to finite packet-length constraints is tackled cyclically over disconnected feasible sets. Numerical results are reported firstly, to illustrate the advantages of the proposed short-packet fully analog design, secondly, to compare its performance to that of on-off beamforming, and finally, to discuss the optimality of proposed optimization algorithm. J. Borras, F. Molina and J. Sala-Álvarez are supported in part by Agencia Estatal de Investigación (AEI, Spain) and by European Regional Development Fund (ERDF) under projects WINTER (TEC2016-76409-C2-1-R) and RODIN (PID2019-105717RB-C22), and in part by the Catalan Government (AGAUR) through Grant 2017 SGR 578. J. Borras is also supported by Fellowship FPI BES-2017-080071 (Spanish Government and ERDF). F. Molina is also supported by Fellowship 2019FI_B1 00085 (Catalan Government, AGAUR). R. López-Valcarce is supported in part by AEI (Spain) and by ERDF under projects WINTER (TEC2016-76409-C2-2-R) and RODIN (PID2019- 105717RB-C21), and in part by Xunta de Galicia (Agrupación Estratéxica Consolidada de Galicia accreditation 2016-2019). All authors are also supported by the AEI and ERDF through the research network COMONSENS Network (RED2018-102668-T).

© 2020 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. An optimum energy allocation for massive user networks operating under iterative successive interference cancellation (I-SIC) is derived in this work. We analyze an uplink setting where a large network of cost-effective low-power users employ a practical transmission scheme consisting of the same channel encoder followed by spread spectrum modulation. Variational calculus (VC) is utilized to derive the asymptotic large-user energy distribution that favors I-SIC’s performance, in terms of spectral efficiency (SE), when at most two decoding attempts per user are performed. The capacity region under random spreading and SIC operating in the infinite blocklength regime is evaluated and contrasted with the maximized SE using short packets. This work is supported in part by the Spanish Government through project TEC2016-76409-C2-1-R (AEI/FEDER, UE) (WINTER), in part by the Catalan administration (AGAUR) under Grant 2017 SGR 578, and in part by the Secretary for Universities and Research of the Generalitat de Catalunya and by the European Social Fund under Fellowship 2019FI B1 00085.

Most gender-based violence victims who sought help in Spain did so through health services. Training on gender-based violence with active learning methodologies promotes the management of knowledge, reflection, and adaptation to change. Nurses, along with an educator, can construct knowledge with the same strategies they will use professionally.To evaluate the knowledge, skills, and attitudes associated of postgraduate nurses on gender-based violence before and after a reflection-based training program with dramatized problem-videos. The secondary objectives were to evaluate the knowledge in the activation of protocols, skills, and attitudes in the management of women who are victims of gender-based violence, the consolidation of learning, and the applicability to the workplace.Pre-post quasi-experimental study without a control group. A specifically validated and designed instrument was utilized to evaluate the dimensions of knowledge, skills, and attitudes when facing gender-based violence, before and after the training sessions, along with additional questions to assess if the participants possessed better tools to address gender-based violence.The difference between the pre and post-tests was statistically significant for the dimensions knowledge, skills, and attitude (p 0.05), with a smaller effect size in the dimensions skills and attitude. Also, high scores were observed in the consolidation of learning and applicability to the workplace.Reflection-based training with dramatized problem-videos improved the acquisition of tools necessary for the detection and management of gender-based violence of nurses.

© 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. This work studies the spectral efficiency achievable when a very large number of terminals are connected simultaneously to a central node (uplink) through independent and identically-distributed flat-fading channels. Assuming that terminals only have statistical channel state information (CSI), the optimum random transmitted-energy allocation is formulated considering a non-orthogonal direct-sequence code-division multiple access (DS-CDMA) where all users transmit using the same modulation and error correcting code and the receiver implements successive interference cancellation (SIC). Focusing on low-power terminals, optimization is carried out by imposing constraints on both the average and peak peruser transmitted energy. Simulations have revealed that a limited number of random energy levels, whose number is determined by the channel power gain variance, is sufficient to achieve approximately the maximum spectral efficiency that would be obtained under direct optimization of the received energy profile.

© 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. A multiple access (MA) optimization technique for massive low-rate direct-sequence spread spectrum communications is analyzed in this work. A dense network of users transmitting at the same rate to a common central node under channelaware energy allocation is evaluated. At reception, successive interference cancellation (SIC) aided by channel decoding is adopted. Our contribution focuses on wireless scenarios involving a vast number of users for which the provided user-asymptotic model holds. Variational calculus (VC) is employed to derive the energy allocation function that, via user-power imbalance, maximizes the network spectral efficiency (SE) when perfect channel state information at transmission (CSIT) is available and both average and maximum per-user energy constraints are set. Monte Carlo simulations at chip-level of a SIC receiver using a real decoder assess the proposed optimization method.

© 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. This work addresses the optimization of the network spectral efficiency (SE) under successive interference cancellation (SIC) at a given blocklength n. We adopt a proof-of-concept satellite scenario where network users can vary their transmission power and select their transmission rate from a set of encoders, for which decoding is characterized by a known packet error rate (PER) function. In the large-system limit, we apply variational calculus (VC) to obtain the user-energy distribution, the assigned per-user rate and the SIC decoding order maximizing the network SE under a sum-power constraint at the SIC input. We analyze two encoder sets: (i) an infinite set of encoders achieving information-theoretic finite blocklength PER results over a continuum of code rates, where the large-n second order expansion of the maximal channel coding rate is used; (ii) a feasible finite set of encoders. Simulations quantify the performance gap between the two schemes.

© 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. Interference may pose a severe limitation to massive wireless multiple access unless the central receiver is endowed with strong multipacket reception capabilities. In that respect, Interference Cancellation (IC) has been extensively studied [1]–[3]. Such systems have been proposed for satellite communications, combining Direct Sequence (DS) Code Division Multiple Access (CDMA) with a SIC receiver [4]–[6] or using multipacket transmission as in Contention Resolution Diversity Slotted ALOHA (CRDSA) [7] [8]. The use of powerful encoders coupled with power imbalance at reception favours IC and has considerably improved the throughput of such random access protocols [4] [9]. In a context characterized by high user activity and spectrum/orbit congestion [10], it is of interest to develop schemes for space assets that optimize the aggregate spectral efficiency of the user population.

[ES] En las últimas décadas muchos autores han centrado su interés en el concepto de distrito industrial, configuración alternativa al modelo de gran empresa que soporta actualmente una gran presión competitiva debido a los fenómenos de globalización. La presente investigación estudia la evolución de la configuración interna de los distritos industriales, en particular lo referido a la dispersión del tamaño de las empresas localizadas dentro y fuera de estas aglomeraciones territoriales. Mediante un estudio exploratorio basado en el uso de fuentes secundarias de información y a partir de una medida de dispersión dimensional de las empresas como indicador del grado de homogeneidad interna, se analiza una muestra de 120 distritos industriales españoles con un total de 12.293 empresas para el período 1997-2009. Los resultados obtenidos sugieren una variabilidad interna cada vez mayor en las características estructurales de las empresas de los distritos, en donde las pequeñas y medianas empresas tienden a ser cada vez más pequeñas, mientras que las grandes están aumentando su tamaño para ajustarse al nuevo entorno competitivo. Del mismo modo, los niveles de homogeneidad permanecen más estables en empresas de fuera del distrito. Estos resultados pueden cuestionar algunas de las premisas de la literatura tradicional sobre distritos industriales., [EN] In recent decades many authors have paid particular attention to the concept of industrial district, an alternative configuration of the model of large company that is currently supporting a huge competitive pressure due to the phenomenon of globalization. This research studies the evolution of the internal configuration of the industrial districts, particularly in what refers to the size dispersion of the companies located inside and outside of these territorial agglomerations. Through an explorative study based on secondary information sources and by means of the use of a measure of firms’ dimensional dispersion as an indicator of the degree of internal homogeneity, a sample of 120 Spanish industrial districts with a total of 12.293 companies for the period 1997-2009 has been analyzed. Findings suggest a growing internal variability in the structural characteristics of companies in industrial districts in which small and medium sized companies are tending to be smaller while large companies are increasing their size to fit the new competitive environment. Also, levels of homogeneity are remaining more stable in non-district companies. These results can question some of the premises of the traditional literature on industrial districts.

©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. This paper studies the throughput maximization of a dense multiple access network of low-rate subscribers that share the same practical Forward Error Correction (FEC) code and modulation scheme, and transmit to a central node that implements a Successive Soft Interference Cancellation (soft SIC) strategy in order to mitigate Multiple Access Interference (MAI). In the user-asymptotic case, we make use of Variational Calculus (VC) tools to derive, in terms of the Packet Error Rate (PER) of the shared encoder and the Residual Energy (RE) from imperfect cancellation, the optimum energy profile that maximizes the network spectral efficiency, when a sum power constraint at the SIC input is enforced. Comparative performance analyses using a representative encoder are carried out. Simulation results show the benefit of the adopted soft SIC scheme in front of other SIC strategies, obtaining relevant throughput gains under high traffic loads.

© 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. The average packet error rate (PER) and user-PER profiles of iterative successive interference cancellation (I-SIC) are analyzed for a proof-of-concept scenario where asymptotically many code-division-multiple-access users share the same channel encoder. To characterize the iterative decoding receiver, we propose a novel multivariate PER function evaluated over the consecutive signal-to-interference-plus-noise ratios (SINRs) experienced by each undecoded user. Analytic expressions for the user-energy and user-SINR profiles at every iteration are derived via warping operators on the user ordering that relate the asymptotic distribution of undecoded users at different iterations. Monte Carlo simulations using a chip-level I-SIC implementation assess the accuracy of the proposed user-limit analysis.

© 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. This paper deals with the design of a hybrid precoder for millimeter-wave MIMO systems. For the sake of concreteness, we consider an analog processing stage composed of a switching network with analog combining. The main contribution of this work consists on the proposal and evaluation of an optimization procedure based on a smart relaxation. The optimal hybrid precoder under a transmit power constraint is derived, after which, the analog precoding matrix is binarized. After an intuitive reasoning, we note that multiple solutions exist. Nevertheless, the (very) reduced computational complexity of the proposed optimization scheme makes it feasible for realistic implementations. Numerical results are reported to assess the performance of proposed hybrid precoder design.