Receive Spatial Modulation for Massive MIMO Systems

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 throughput. 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 showing that a simple threshold can be obtained at high SNR and its performance approaches the exact threshold. 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

Retrospective Interference Alignment for the MIMO Interference Broadcast Channel

The degrees of freedom (DoF) of the multiple-input multiple-output (MIMO) Interference Broadcast Channel (IBC) with 2 cells and 2 users per cell are investigated when only delayed channel state information is available at the transmitter side (delayed CSIT). Retrospective Interference Alignment has shown the benefits in terms of DoF of exploiting delayed CSIT for interference, broadcast and also for the IBC. However, previous works studying the IBC with delayed CSIT do not exploit the fact that the users of each cell are served by a common transmitter. This work presents a four-phase precoding strategy taking this into consideration. Assuming that transmitters and receivers are equipped with $M,N$ antennas, respectively, new DoF inner bounds are proposed, outperforming the existing ones for $\rho = \frac{M}{N} > 2.6413$.Comment: 1 copyright page + 5 paper pages + 3 appendix pages, Submitted to IEEE ISIT 201

Retrospective Interference Alignment for the 3-user MIMO Interference Channel with delayed CSIT

The degrees of freedom (DoF) of the 3-user multiple input multiple output interference channel (3-user MIMO IC) are investigated where there is delayed channel state information at the transmitters (dCSIT). We generalize the ideas of Maleki et al. about {\it Retrospective Interference Alignment (RIA)} to be applied to the MIMO IC, where transmitters and receivers are equipped with $(M,N)$ antennas, respectively. We propose a two-phase transmission scheme where the number of slots per phase and number of transmitted symbols are optimized by solving a maximization problem. Finally, we review the existing achievable DoF results in the literature as a function of the ratio between transmitting and receiving antennas $\rho=M/N$. The proposed scheme improves all other strategies when $\rho \in \left(\frac{1}{2}, \frac{31}{32} \right]$.Comment: Draft version of the accepted manuscript at IEEE ICASSP 1

On the Degrees of freedom of the K-user MISO Interference Channel with imperfect delayed CSIT

This work investigates the degrees of freedom (DoF) of the K-user multiple-input single-output (MISO) interference channel (IC) with imperfect delayed channel state information at the transmitters (dCSIT). For this setting, new DoF inner bonds are provided, and benchmarked with cooperation-based outer bounds. The achievability result is based on a precoding scheme that aligns the interfering received signals through time, exploiting the concept of Retrospective Interference Alignment (RIA). The proposed approach outperforms all previous known schemes. Furthermore, we study the proposed scheme under channel estimation errors (CEE) on the reported dCSIT, and derive a closed-form expression for the achievable DoF with imperfect dCSIT.Comment: Draft version of the accepted manuscript at IEEE ICASSP 1

Teoría de la Decisión: Proceso de interacciones u organizaciones como sistemas de decisiones

We present a theoretical discussion of the sociological contribution concerning decisions in organizations.Two theories stand. The first, based on the decision process from a critical theory of the traditional linear multirational by Lucien Sfez, argues that the decision is a process of interactions and treats it as an institutional process based on the freedom of the subject. The second theory based on self-referentialsystems by Niklas Luhmann, interprets organizations as systems-making, and understands the concept of decision as purely epistemological specificity, abstracted from the decision of all the elements and organizational variables associated with it.Se expone un debate teórico sobre la aportación sociológica referente a las decisiones en las organizaciones. Sobresalen dos teorías de las decisiones. La primera, basada en el proceso de decisión a partir una teoría crítica de la multirracionalidad lineal elaborado por Lucien Sfez, al plantear que con la decisión se trata de un proceso de interacciones, al ser considerada como un proceso institucional fundamentado en la libertad del sujeto. La segunda fundamentada en la teoría de sistemas autorreferenciales, interpreta las organizaciones como sistemas de decisiones y entiende el concepto de decisión en su especificidad puramente epistemológica, al abstraer de la decisión de todos los elementos y variables organizacionales relacionados con ella (Niklas Luhmann

Optimization of Radio and Computational Resources for Energy Efficiency in Latency-Constrained Application Offloading

Providing femto-access points (FAPs) with computational capabilities will allow (either total or partial) offloading of highly demanding applications from smart-phones to the so called femto-cloud. Such offloading promises to be beneficial in terms of battery saving at the mobile terminal (MT) and/or latency reduction in the execution of applications, whenever the energy and/or time required for the communication process are compensated by the energy and/or time savings that result from the remote computation at the FAPs. For this problem, we provide in this paper a framework for the joint optimization of the radio and computational resource usage exploiting the tradeoff between energy consumption and latency, and assuming that multiple antennas are available at the MT and the serving FAP. As a result of the optimization, the optimal communication strategy (e.g., transmission power, rate, precoder) is obtained, as well as the optimal distribution of the computational load between the handset and the serving FAP. The paper also establishes the conditions under which total or no offloading are optimal, determines which is the minimum affordable latency in the execution of the application, and analyzes as a particular case the minimization of the total consumed energy without latency constraints.Comment: Accepted to be published at IEEE Transactions on Vehicular Technology (acceptance: November 2014

La búsqueda de la realidad o de la verdad: una aproximación a partir de la teoría sociológica

El objetivo de este artículo es pensar el nexo de la búsqueda de la realidad o de la verdad con la metodología, al plantear preguntas a diversas corrientes teóricas y analizar las respuestas de cada autor o corriente al respecto. Desde la perspectiva teórica sociológica, se abordan dos niveles de reflexión con implicaciones metodológicas. El primero, hace referencia a las implicaciones metodológicas derivadas de la búsqueda de la realidad o de la verdad. El segundo, de carácter epistemológico, hace referencia a la dualidad teórica y paradigmática existente entre la capacidad subjetiva de decisión frente a la constricción de los sujetos por parte de las estructuras. The aim of this article is to think the relationship between the search for reality or the truth with methodology, by asking some questions to different theoretical perspectives and by analyzing different answers given by the authors and theories. From the sociological theoretical perspective, it deals with two levels of thought with methodological implications. The first refers to the methodological implications arising from the search for reality or truth. The second, epistemological, refers to the theoretical and paradigmatic duality between subjective capacity decisions against the constriction of the subjects by the structures