Suchergebnisse

In this paper, an energy harvesting transmitter operating in a point-to-point link through a discrete-time fading channel is considered, where symbols can be transmitted through several parallel independent streams. Taking into account the different sources of energy consumption at the transmitter, the resource allocation (in terms of power allocation and selection of the active streams and channel accesses) that asymptotically maximizes the mutual information is derived by assuming that the transmitter has non-causal knowledge of the harvested energy and channel state (offline approach). The Boxed Water-Flowing graphical interpretation is presented, which intuitively depicts the asymptotically optimal offline resource allocation. Moreover, an online algorithm is proposed for the case in which the transmitter only has causal (past and present) knowledge of the harvested energy and channel state. Finally, the performance of the proposed offline and online solutions is numerically evaluated and the associated computational complexities are assessed and compared. ; Grant number: The Catalan Government under grant 2014 SGR 1551 and the Spanish Ministry of Economy and Competitiveness under project TEC2011-29006-C03-01 (GRE3N-PHY). © 2014 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 considers a network of energy harvesting wireless nodes transmitting simultaneously in a Gaussian interference channel and investigates a distributed power allocation algorithm that maximizes the sum-rate. The power consumption model is based on a series of step functions that allow to model, among others, radio frequency circuits being on/off and the startup power consumption of the transmitter. After showing that the sum-rate maximization problem is nonsmooth, nonconvex, and NP-hard, the Iterative Smooth and Convex approximation Algorithm (ISCA) is proposed, which successively approximates the step functions by proper smooth functions to obtain a sequence of smooth nonconvex problems that can be solved by means of the successive convex approximation method. It is demonstrated that the ISCA distributedly converges to a stationary solution of the sum-rate maximization problem. For the particular case of point to point communications, the numerical results show that the ISCA is able to avoid bad stationary solutions, performing close to the globally optimal solution. The performance of the ISCA is also evaluated in the interference channel and with real solar energy harvesting data. ; Grant numbers : This work is partially supported by the Spanish Government through the projects INTENSYV (TEC2013-44591-P), AEThER (TEC2014-58341-C4-4-R), and E-CROPs (PCIN-2013-027) by the Catalan Government (2014 SGR 1567 and 2014 SGR 1551).© 2016 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 presents the experimental evaluation of an interference-mitigation scheme tailored for heterogeneous multi-cell LTE-based systems. The real-time FPGA-based system implementation was evaluated under realistic operating conditions using the GEDOMIS® testbed. An intensive measurement campaign was conducted to assess the performance-gains of the proposed scheme, considering mobile channels and various levels of noise and interference. ; Grant numbers : This work was partially supported by: the Spanish Government under projects TEC2011-29006-C03-01 (GRE3N-PHY).© 2014 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 proceeding at: 3rd International Workshop on Cognitive Information Processing (CIP 2012), took place 2012, May 28-30, in Baiona, España. The event Web site at http://cip2012.tsc.uc3m.es/ ; In this work we consider the optimization of the power assigned to the user streams in a coordinated base station downlink environment with Orthogonal Frequency Division Modulation (OFDM). In this scenario the base stations perform distributed cooperative processing with a block diagonalization scheme to remove interference among users. Two schemes based on the waterfilling technique are proposed and compared to the optimal solution, which can be obtained numerically, by using convex optimization. We show that the proposed schemes achieve a performance, in terms of weighted sum rate, very close to the optimal, without the heavy computational complexity required by the numerical solution. These sum rates are compared in a simplified scenario consisting of two-user and two-cell. Other more realistic multicell scenario and some examples of achievable rates are presented too. ; The research leading to these results has received funding from the Spanish Government under coordinated projects TEC2008-06327-C03-01/02/03 (MULTI-ADAPTIVE) and TEC2011-29006-C03-01/02/03 (GRE3N) and from EU FP7 project INFSO-ICT-247223 ARTIST 4G. ; Publicado

Interference is a major obstacle in radio communications, especially when opportunistic frequency reuse is an inherent requirement for maximising spectral efficiency in heterogeneous networks. A typical example is encountered in cellular communications where macrocell-edge users receive interference from small cell transmissions that use the same radio frequency band. Innovating interference management algorithms are employed towards this end, which because of their interdependencies with numerous parameters of the target operating scenario and various low-level implementation aspects, need to be prototyped in real-time signal processing platforms in order to be credibly verified. In this paper, we present the development and experimental validation of a macrocell/femtocell coexistence scenario in close to real-life conditions. The inclusion of an agile interference management scheme increased the signal processing complexity at the physical layer. This overhead was appropriately addressed by engaging advanced parallel processing techniques, optimisations of the arithmetic operations and intelligent reuse of logic and memory resources in the field programmable gate array (FPGA)-based baseband processing architecture. ; Grant number : Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad) under projects and TEC2011-29006-C03-01 (GRE3N-PHY), and from the Catalan Government under grant 2009 SGR 1046 (SGR-RC).

The virtualization of mobile network functions constitutes one of the main blocks for addressing the high flexibility requirements of fifth generation (5G) communication systems. Reconfigurable hotspots are expected to be massively deployed to enable on-demand services and dynamically adapt the network capacity according to traffic requirements. In this paper, we present the extensions and modifications of the long term evolution (LTE) module of the ns-3 simulator (LENA) to include a software defined radio (SDR) physical layer implementation. These extensions combine the native flexibility of the simulator with the SDR features of a real-time prototype. Moreover, the framework was designed to distribute the communication functions across different elements of the network with the possibility of adjusting several transmission parameters as in a network function virtualization (NFV) paradigm. Thanks to an emulated full network protocol stack, the prototype allows the experimentation of novel 5G solutions and the evaluation of relevant key performance indicators (KPIs) from the lower layer protocols up to application level. To this aim, we present the experimental evaluation of the KPIs of energy, latency, throughput and reconfiguration time in relevant scenarios. ; Grant numbers : projects partially supported by the Generalitat de Catalunya (2014 SGR 1551 and 2014 SGR 1397) and by the Spanish Government under project TEC2014-58341-C4-4-R and TEC2017-88373-R. © 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.

Characterizing the energy cost of different physical (PHY) layer building blocks is becoming increasingly important in modern cellular-based communications, considering the cross sector requirements for performance enhancements and energy savings. This paper presents energy profiling metrics of different PHY-layer FPGA implementations encountered in modern wireless communication systems. The results give an insight of the distribution of the consumed energy in different baseband building blocks or configurations before and after applying power optimizations in the FPGA design and implementation. ; Grant numbers : This work was partially supported by: the Spanish Government under projects TEC2011-29006-C03-01 (GRE3N-PHY).© 2014 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 presents the Flex5Gware project, whose goal is to deliver highly reconfigurable hardware (HW) platforms and HW-agnostic software (SW) platforms for 5G network elements and terminal devices. Flex5Gware will enable 5G HW/SW platforms to meet the requirements imposed by the growth in mobile traffic and the diversity of applications by increasing their capacity, reducing their energy footprint and enhancing their scalability and modularity. To put in place this vision in this early stage of 5G PPP research, Flex5Gware is designing and prototyping key building blocks of 5G HW/SW platforms. In particular, the developed technologies will be evaluated and demonstrated with proofs-of-concept by the end of the project. ; Grant numbers : The first and fourth authors would also like to acknowledge the support from the Catalan government to their research group 2014 SGR 1551.

Cloud-based radio access networks (C-RAN) are expected to face important challenges in the forthcoming fifth generation (5G) communication systems. For this reason, more flexible C-RAN architectures have recently been proposed in the literature, where the radio communication stack is partitioned and placed across different RAN nodes to tackle the 5G capacity and latency requirements. In this paper, we show that this functional split also supports energy efficiency, especially when it is combined with bandwidth adaptation. To this aim, we have built a dynamic hotspot prototype, where the hardware-accelerated physical-layer is placed in the remote radio head, and higher software-based layers are placed in a server (either directly connected or remotely accessible). This setup allowed us to experimentally evaluate the power consumption of key hardware modules when adapting the bandwidth and the modulation and coding scheme. The real-time operation of the testbed allows further experimentation with different 5G use cases and the evaluation of other key performance indicators. ; Grant numbers : The work of CTTC was also partially supported by the Generalitat de Catalunya (2014 SGR-1551) and by the Spanish Government under project AETHER (TEC2014-58341-C4-4-R).© 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.

Flexibility and energy efficiency are considered two principal requirements of future fifth generation (5G) systems. From an architectural point of view, centralized processing and a dense deployment of small cells will play a vital role in enabling the efficient and dynamic operation of 5G networks. In this context, reconfigurable hotspots will provide on-demand services and adapt their operation in accordance to traffic re quirements, constituting a vital element of the heterogeneous 5G network infrastructure. In this paper we present a reconfigurable hotspot which is able to flexibly distribute its underlying communication functions across the network, as well as to adapt various parameters affecting the generation of the transmitted signal. The reconfiguration of the hotspot focuses on minimizing its energy footprint, while accounting for the current operative requirements. A real-time hotspot prototype has been developed to facilitate the realistic evaluation of the energy saving gains of the proposed scheme. The development flexibly combines software (SW) and hardware (HW) accelerated (HWA) functions in order to enable the agile reconfiguration of the hotspot. Actual power consumption measurements are presented for various relevant 5G networking scenarios and hotspot configurations. This thorough characterization of the energy footprint of the different subsystems of the prototype allows to map reconfiguration strategies to different use cases. Finally, the energy-aware design and implementation of the hotspot prototype is widely detailed in an effort to underline its importance to the provision of the flexibility and energy efficiency to future 5G systems. ; This work was supported by the European Commission in the framework of the H2020-ICT-2014-2 project Flex5Gware (Grant agreement no. 671563). The work of CTTC was also partially supported by the Generalitat de Catalunya (2017 SGR 891) and by the Spanish Government under project TEC2014-58341-C4-4-R.

5G has a main requirement of highly flexible, ultralow latency and ultra-high bandwidth virtualized infrastructure in order to deliver end-to-end services. This requirement can be met by efficiently integrating all network segments (radio access, aggregation and core) with heterogeneous wireless and optical technologies (5G, mmWave, LTE/LTE-A, Wi-Fi, Ethernet, MPLS, WDM, software-defined optical transmission, etc.), and massive computing and storage cloud services (offered in edge/core data centers). This paper introduces the preliminary architecture aiming at integrating three consolidated and standalone experimental infrastructures at CTTC, in order to deploy the required end-to-end top-to-bottom converged infrastructure pointed out above for testing and developing advanced 5G services. ; Grant numbers : This work has been supported by the Catalan Government under grants 2014 SGR 1567, 2014 SGR 1551.© 2015 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.