Olga Muñoz Medina | Universitat Politecnica de Catalunya (original) (raw)

Papers by Olga Muñoz Medina

Interference statistics approximations for data rate analysis in uplink massive MTC

Machine-type-communications have attracted a lot of interest in the past years. They rely on inte... more Machine-type-communications have attracted a lot of interest in the past years. They rely on interactions between devices with no human supervision. This will help to the advent of a plethora of applications such as the Internet-of-Things. Part of the research within this field deals with coordinating the access of a large number of devices to the network, the so-called \textit{massive} machine-type-communications. In this paper, we focus on the evaluation of the data rate for that scenario, based on an approximation of the statistics of the aggregated interference that depends on the sensors activity. We will consider that the sensors can be in either active or sleep mode, modeled as a Bernoulli random variable. This results in an aggregated interference that follows a discrete distribution whose computation becomes unfeasible with the number of devices. That is why two alternatives are presented to replace the original magnitude and work with an analytic closed form expression app...

Applebaum adaptative beamformer with steering vector estimation for ciclostationary signals

1996 8th European Signal Processing Conference (EUSIPCO 1996), 1996

This paper presents a novel technique to globally estimate and track the direction of arrival (DO... more This paper presents a novel technique to globally estimate and track the direction of arrival (DOA) of different users in an asynchronous CDMA system. The estimates are obtained exploiting the temporal structure of CDMA signals. No training signal nor a priori spatial information is required. The necessary information is extracted directly from the received signals. The proper combining of the overall information present at the receiver after the despreading, jointly with an Eigenvalue Decomposition (EVD), let as estimate the generalized steering vector for each user. Furthermore, a direct iteration method is introduced in our scheme in order to make the array robust to channel variations and to reduce the computational load of the EVD required for each user.

Antenas inteligentes para sistemas de comunicaciones moviles cdma

La tesis doctoral versa sobre el uso de frontales Multi-Antena (Array de Antenas) para la detecci... more La tesis doctoral versa sobre el uso de frontales Multi-Antena (Array de Antenas) para la deteccion Multi-Usuario en comunicaciones moviles con acceso CDMA. Se estudian los modelos de senal en entornos Multi-Usuario y Multi-Antena en canales con desvanecimiento no selectivo y selectivo en frecuencia, para acceso sincrono y asincrono. En cada uno de los cuatro escenarios anteriores, se propone el algoritmo de estimacion de la firma espacial y de deteccion. Se estudia, ademas, la problematica de la presencia de interferentes C-canal en la estiimacion del canal y la deteccion.

2020 IEEE 21st International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2020

Machine-type-communications (MTC) are being crucial in the development of next generation mobile ... more Machine-type-communications (MTC) are being crucial in the development of next generation mobile networks. Given that MTC devices are usually battery constrained, wireless power transfer (WPT) and energy harvesting (EH) have emerged as feasible options to enlarge the lifetime of the devices, leading to wireless powered networks. In that sense, we consider a setup where groups of sensors are served by a base station (BS), which is responsible for the WPT. Additionally, EH is used to collect energy from the wireless signals transmitted by other sensors. To characterize the energy obtained from both procedures, we model the sporadic activity of sensors as Bernoulli random variables and their positions with repulsive Matérn cluster processes. This way, the random activity and spatial distribution of sensors are introduced in the analysis of the energy statistics. This analysis can be useful for system design aspects such as energy allocation schemes or optimization of idle-active period...

Joint allocation of radio and computational resources in wireless application offloading

Providing femto-access points (FAPs) with computational capabilities will allow (either totally o... more Providing femto-access points (FAPs) with computational capabilities will allow (either totally or partially) 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 executing applications, if the energy and/or time required for the communication process are compensated by the energy and/or time savings that result from remote computation. For this scenario, we provide a general framework that allows the joint allocation of radio and computational resources resulting in an optimized trade-off between energy consumption and latency. Such energy ansumption includes contributions from both communication and computation segments. Complex communication models (e.g. multi-input multi-output (MIMO) transmission) can be encompassed within the proposed framework. Moreover, practical constraints can be included, such as energy constra...

Estudio comparativo de las matrices de correlación clásica y cíclica en arrays de banda estrecha

The aim of this communication is to study the differences and similarities between the classic an... more The aim of this communication is to study the differences and similarities between the classic and cyclic correlation matrices of the data snapshots sensed by an array. We will focus our study in the comparison of the eigenvalues decomposition for each matrix. Special attention will be paid on topics like rank and nature of eigenvectors and eigenvalues. Other aspects involved in the estimation of both matrices, such as number of data snapshots required and sensitivity to deviations of the cyclic parameter will be also treated. Finally, we will carry out simulations in order to confirm the previously obtained theoretical results.

The lighting is going through revolution. The use of Light Emitting Diodes (LEDs) has greatly inc... more The lighting is going through revolution. The use of Light Emitting Diodes (LEDs) has greatly increased during the last few years, meanwhile incandescent and fluorescent lamps have become obsolete. The LEDs, apart from being extremely high energy efficient, are able to switch to different light intensities at very high speed. This fact, along with the looming crisis of Radio Frequency (RF) spectrum, has given rise to an attractive communication technology known as Visible Light Communication (VLC) that uses the huge licensefree spectrum of approximately 400 THz, which is more than 1,000 larger than the RF spectrum. This technology offers a novel alternative to RF, enabling the development of wireless communications that make use of existing lighting infrastructure. This thesis studies multi-user multiple-input single-output (MU-MISO) visible light communications techniques for indoor broadcast systems. Particularly, we have proposed a railway wagon as scenario. Transmitters, configu...

INTERNATIONAL JOURNAL OF ADVANCED SCIENTIFIC AND TECHNICAL RESEARCH, 2019

This research work addressed the major concern of signal distortion in a Telecommunication networ... more This research work addressed the major concern of signal distortion in a Telecommunication networks which result in poor signal strength reception. Data communication has become increasingly in high demand in carrying out day to day activities. The need for reliable data communication-system for internet access cannot be over emphasized in networks users' still experience poor network services such as poor internet access and weak signal reception. This research work characterizes transmission networksof telecommunication systemand developed a model to equalize the phase amplitude signal of a transmission network using the Least Mean Square (LMS) adaptive equalizer algorithms. The simulation was carried out using MATLAB SIMULINK. The result obtained from the Simulations carried out in this work shows that the algorithms implemented in this research work are powerful as regards the negation of the effect of channel distortions. Thus, considering simulations carried out on both the SIMULINK model without an adaptive equalizer and that with an adaptive equalizer at the receiver, it shows that the transmission model with an adaptive equalizer enhanced the signal reception by 20%.This has proved that an adaptive equalizer helps in enhancing or improving signal reception in transmission network.

Long-term provisioning of radio resources based on their utilization in dense OFDMA networks

2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2016

This paper presents long-term resource provisioning schemes for dense multi-cell OFDMA-based netw... more This paper presents long-term resource provisioning schemes for dense multi-cell OFDMA-based networks, where multiple cells with possibly overlapping coverage areas compete for the same set of resources. The optimization is done over the long term, being independent of the specific users connected to each cell but dynamic enough to follow significant variations of the traffic load. In this sense, we focus on the average resource utilization (RU) and propose schemes to minimize the maximum RU of all cells. Firstly, we consider orthogonal resource usage among cells. Optimal closed-form expressions for the long-term resource provisioning are derived for this case. Secondly, we assume that resources can be reused at non-overlapping cells. In this case, the resource provisioning is solved in two steps: i) the number of resources required per cell is obtained by discretizing the optimal solution of a convex problem, and then ii) the specific resources to be utilized by each cell are determined by using graph coloring. In contrast to previous works, graph coloring can be applied to get an implementable solution for any condition of the cell loads. Simulation results show a significant reduction of the maximum RU, which translates into an increase of the served traffic and a reduction of the packet delay, as compared to static resource provisioning schemes.

Fundamentos tecnológicos II

2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), 2014

We consider a system where multiple users are connected to a small cell base station enhanced wit... more We consider a system where multiple users are connected to a small cell base station enhanced with computational capabilities. Instead of doing the computation locally at the handset, the users offload the computation of full applications or pieces of code to the small cell base station. In this scenario, this paper provides a strategy to allocate the uplink, downlink, and remote computational resources. The goal is to improve the quality of experience of the users, while achieving energy savings with respect to the case in which the applications run locally at the mobile terminals. More specifically, we focus on minimizing a cost function that depends on the latencies experienced by the users and provide an algorithm to minimize the latency experienced by the worst case user, under a target energy saving constraint per user.

2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications, 2011

This paper addresses the problem of resource allocation and quality of service (QoS) management i... more This paper addresses the problem of resource allocation and quality of service (QoS) management in a downlink communication system where the users are allowed to be attached to and receive data from one or several cooperating base stations (BSs) under orthogonal frequency division multiple access (OFDMA). Under the assumption that only information regarding the link path loss is available at each transmitter, the problem of power and bandwidth allocation to minimize transmission power subject to minimum rate (i.e., QoS) constraints is written as a convex optimization problem. Considering that the transmission power per BS is limited, the Lagrange multipliers of the optimization problem are exploited either to efficiently identify which are the candidates to be preempted whenever unaffordable power consumption arises, or to relax the target rate constraints for the ongoing connections. In the second case, the Lagrange multipliers are used in combination with the Newton-Raphson algorithm to adjust the QoS of the users in the system according to the available BS power.

This deliverable intends to provide an analysis of the network architecture required for smallcel... more This deliverable intends to provide an analysis of the network architecture required for smallcell-cloud computing. The architectural framework considered in this document refers to LTE small cell architecture options outlined in the 3GPP standard.The individual elements for radio, cloud and backhaul are described and various possibilities are considered and compared in order to bring them all together for the operation of a small cell cluster to take place in an LTE environment, taking into account the differences between residential and corporate environments. The inter-cluster scenario, for greater computing capabilities, is also analysed. Finally, several solutions are provided for different problems encountered during the analysis, such as Over the Air Communication and distributed cluster management, among others. This document can be used as a recommendation for operators adopting the small-cell-cloud paradigm. The architectural choices are recommendations that telecom operators may study and evaluate according to their requirements and preferences.

The implementation of femtocells introduces many technical challenges that must be solved in orde... more The implementation of femtocells introduces many technical challenges that must be solved in order to fully exploit their potentials. This deliverable primarily focuses on control procedures for radio resource management addressing the most critical issues. To utilize radio resources of femtocell efficiently, a novel routing of data among users served by the same femtocell is proposed. Furthermore, spectrum-efficient technique for power control, scheduling (both at radio side and backhaul side and multicast/broadcast services transmissions are designed. Additionally, novel authorization approaches and femtocells' identification technique are proposed while taking in consideration the scalability of the system. Besides the optimization of radio resource management procedures, this document designs and specifies the control plane procedures to ensure effective coordination among femtocells and macrocell designed in WP3. Finally, cross-layer optimization issues are addressed here by means of optimal femtocells' power allocation derivation using the Game Theory framework.

FREEDOM is organized in six technical work-packages (WP), as described below, aimed at solving as... more FREEDOM is organized in six technical work-packages (WP), as described below, aimed at solving as many research challenges, plus a management WP. WP2: The goals of this WP are to identify the scenarios of interest, establish requirements and performance metrics, to ensure that the project offsprings are consistent with reference organizations (e.g. IETF, 3GPP/LTE-A, Femto Forum), and disseminate the results. WP3: WP3 is primarily concentrated on Physical Layer (PHY) issues. Its goals are: 1) to examine decentralized strategies for radio resource management; 2) to evaluate the spectral/energy efficiency improvement resulting from local coordination of femto access points (FAP), through the backhaul (wired) link; 3) to explore the gain obtainable through cooperation, based on the exchange of data among FAPs;

FREEDOM D3. 2 Interference Coordination Protocols in Femto-based Networks

This document looks into coordinated radio resource allocation algorithms in deployments of huge ... more This document looks into coordinated radio resource allocation algorithms in deployments of huge number of femto-access points (FAP) by exploiting the message exchange at control-plane level through the wired ISP backhaul link.