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

Approximations of the aggregated interference statistics for outage analysis in massive MTC

This paper presents several analytic closed-form approximations of the aggregated interference statistics within the framework of uplink massive machine-type-communications (mMTC), taking into account the random activity of the sensors. Given its discrete nature and the large number of devices involved, a continuous approximation based on the Gram–Charlier series expansion of a truncated Gaussian kernel is proposed. We use this approximation to derive an analytic closed-form expression for the outage probability, corresponding to the event of the signal-to-interference-and-noise ratio being below a detection threshold. This metric is useful since it can be used for evaluating the performance of mMTC systems. We analyze, as an illustrative application of the previous approximation, a scenario with several multi-antenna collector nodes, each equipped with a set of predefined spatial beams. We consider two setups, namely single- and multiple-resource, in reference to the number of resources that are allocated to each beam. A graph-based approach that minimizes the average outage probability, and that is based on the statistics approximation, is used as allocation strategy. Finally, we describe an access protocol where the resource identifiers are broadcast (distributed) through the beams. Numerical simulations prove the accuracy of the approximations and the benefits of the allocation strategy.Peer ReviewedPostprint (published version

User grouping and resource allocation in multiuser MIMO systems under SWIPT

This paper considers a broadcast multiple-input multiple-output (MIMO) network with multiple users and simultaneous wireless information and power transfer (SWIPT). In this scenario, it is assumed that some users are able to harvest power from radio frequency (RF) signals to recharge batteries through wireless power transfer from the transmitter, while others are served simultaneously with data transmission. The criterion driving the optimization and design of the system is based on the weighted sum rate for the users being served with data. At the same time, constraints stating minimum per-user harvested powers are included in the optimization problem. This paper derives the structure of the optimal transmit covariance matrices in the case where both types of users are present simultaneously in the network, particularizing the results to the cases where either only harvesting nodes or only information users are to be served. The trade-off between the achieved weighted sum rate and the powers harvested by the user terminals is analyzed and evaluated using the rate-power (R-P) region. Finally, we propose a two-stage user grouping mechanism that decides which users should be scheduled to receive information and which users should be configured to harvest energy from the RF signals in each particular scheduling period, this being one of the main contributions of this paper.Peer ReviewedPostprint (published version

Técnicas de encaminamiento en redes ad-hoc basadas en criterios de potencia y batería

Las redes ad hoc están formadas únicamente por terminales móviles que funcionan a partir de baterías, es decir, no hay estaciones base. El consumo de energía es, por lo tanto, un punto muy importante ala hora de diseñar la red. Paramax.imizar el tiempo de vida de una red ad hoc, el consumo de energía tiene que ser distribuido de forma equitati va entre el conjunto de nodos que la forman, y a la vez ha de rIÚnirnizarse el consumo total de energía para cada transmisión. Los algoritmosdeencarninarniento clásicos para ad hoc no tienen en cuenta la energía y por tanto no consiguen maximizar el tiempo de vida de la red. En este artículo se hace un estudio del estado del arte en métricas de encaminamiento que tengan en cuenta la batería al seleccionar las rutas y se proponen nuevas métricas al respecto. Dichas métricas se comparan mediante simulación intentando llegar a un compromiso entre parámetros como el tiempo de vida de la red y la calidad de servicio, entre otros.Peer Reviewe

Técnicas de procesado de señal basadas en múltiples antenas para redes inalámbricas con modulaciones OFDM

Peer Reviewe

Técnicas de encaminamiento en redes ad-hoc basadas en criterios de potencia y batería

Las redes ad hoc están formadas únicamente por terminales móviles que funcionan a partir de baterías, es decir, no hay estaciones base. El consumo de energía es, por lo tanto, un punto muy importante ala hora de diseñar la red. Paramax.imizar el tiempo de vida de una red ad hoc, el consumo de energía tiene que ser distribuido de forma equitati va entre el conjunto de nodos que la forman, y a la vez ha de rIÚnirnizarse el consumo total de energía para cada transmisión. Los algoritmosdeencarninarniento clásicos para ad hoc no tienen en cuenta la energía y por tanto no consiguen maximizar el tiempo de vida de la red. En este artículo se hace un estudio del estado del arte en métricas de encaminamiento que tengan en cuenta la batería al seleccionar las rutas y se proponen nuevas métricas al respecto. Dichas métricas se comparan mediante simulación intentando llegar a un compromiso entre parámetros como el tiempo de vida de la red y la calidad de servicio, entre otros.Peer Reviewe

Técnicas de procesado de señal basadas en múltiples antenas para redes inalámbricas con modulaciones OFDM

Peer Reviewe

Precoding and feedback schemes for a MIMO backhaul link in the presence of interference

Postprint (published version

Trade-off between feedback load for the channel state information and system performance in MIMO communications

Postprint (author’s final draft