Compromis efficacité énergétique et spectrale dans les réseaux sans fil limités par les interférences

One of the used strategies to increase the spectral efficiency (SE) of cellular network is to reuse the frequency bandwidth over relatively small areas. The major issue in this case is higher interference, decreasing the energy efficiency (EE). In addition to the higher bandwidth, densification of the networks (e.g. small cells or multi-user multiple input single output, MU-MISO) potentially increases the area spectral efficiency (ASE). The total energy consumption of the wireless networks increases due to the large amount of circuit power consumed by the dense network structures, leading to the decrease of EE. In this thesis, the EE-SE achievable region is characterized in a hexagonal cellular network considering several frequency reuse factors (FRF), as well as shadowing. The EE-ASE region is also studied using Poisson point processes (PPP) to model the MU-MISO network with signal-to-leakage-and-noise ratio (SLNR) precoder. Different base station (BS) densities and different number of BS antennas with static power consumption are considered.The EE-SE region in a hexagonal cellular network for different FRF, both with and without shadowing is first characterized. When shadowing is considered in addition to the path loss, the ε-SE-EE tradeoff is proposed as an outage measure for performance evaluation. The EE-SE curves have a large linear part, due to the static power consumption, followed by a sharp decreasing EE, since the network is homogeneous and interference-limited. The results show that FRF of 1 for regions close to BS and higher FRF for regions closer to the cell edge improve the EE-SE optimal point. Moreover, better EE-SE tradeoff can be achieved with higher outage values. Besides, FRF of 1 is the best choice for very high outage value due to the significant signal-to-interference-plus-noise ratio (SINR) decrease.In downlink, precoders are used in space division multiple access (SDMA) MU-MISO cellular networks to improve the SINR. Stochastic geometry has been intensively used to analyse such a complex system. A closed-form expression for ASE in asymptotic regime, i.e. number of antennas and number of users grow to infinity, has been derived using random matrix theory and stochastic geometry. BSs and users are modeled by two independent PPP and SLNR precoder is used at BS. EE is then derived from a linear power consumption model. Monte Carlo simulations show that the analytical expressions are tight even for moderate number of antennas and users. Moreover, the EE-ASE curves have a large linear part before a sharply decreasing EE, as observed for hexagonal network. The results also show that SLNR outperforms the zero-foring (ZF) precoder, which is typically used in literature. Numerical results for SLNR show that deploying more BS or a large number of BS antennas increase ASE, but the gain depends on the BS-user density ratio and on the number of antennas when user density is fixed. EE increases only when the increase in ASE dominates the increase of the power consumption per unit area. On the other hand, when the user density increases, ASE in interference-limited region can be improved by deploying more BS without sacrificing EE and the ergodic rate of the users.L'une des stratégies utilisée pour augmenter l'efficacité spectrale (ES) des réseaux cellulaires est de réutiliser la bande de fréquences sur des zones relativement petites. Le problème majeur dans ce cas est un plus grand niveau d'interférence, diminuant l'efficacité énergétique (EE). En plus d'une plus grande largeur de bande, la densification des réseaux (cellules de petite taille ou multi-utilisateur à entrées multiples et sortie unique, MU-EMSO), peut augmenter l'efficacité spectrale par unité de surface (ESuS). La consommation totale d'énergie des réseaux sans fil augmente en raison de la grande quantité de puissance de circuit consommée par les structures de réseau denses, réduisant l'EE. Dans cette thèse, la région EE-SE est caractérisé dans un réseau cellulaire hexagonal en considérant plusieurs facteurs de réutilisation de fréquences (FRF), ainsi que l'effet de masquage. La région EE-ESuS est étudiée avec des processus de Poisson ponctuels (PPP) pour modéliser un réseau MU-EMSO avec un précodeur à rapport signal sur fuite plus bruit (RSFB). Différentes densités de station de base (SB) et nombre d'antennes aux SB avec une consommation d'énergie statique sont considérées.Nous caractérisons d'abord la région EE-SE dans le réseau cellulaire hexagonal pour différentes FRF, avec et sans masquage. Avec le masquage en plus de la perte de propagation, la mesure de coupure ε-EE-ES est proposée pour évaluer les performances. Les courbes EE-ES présentent une grande partie linéaire, due à la consommation de puissance statique, suivie d'une forte diminution de l'EE, puisque le réseau est homogène et limité par les interférences. Les résultats montrent qu'un FRF de 1 pour les régions proches de la SB et des FRF plus élevés dans la région plus proche du bord de la cellule améliorent le point optimal du EE-ES. De plus, un meilleur compromis EE-ES peut être obtenu avec une valeur plus élevée de coupure. En outre, un FRF de 1 est le meilleur choix pour une valeur élevée de coupure en raison d'une réduction du rapport signal sur interférence plus bruit (RSIB).Les précodeurs sont utilisés en liaison descendante des réseaux cellulaires MU-EMSO à accès multiple par division spatiale (AMDS) pour améliorer le RSIB. La géométrie stochastique a été utilisée intensivement pour analyser de tels systèmes complexes. Nous obtenons une expression analytique de l'ESuS en régime asymptotique, c.-à-d. nombre d'antennes et d'utilisateurs infinis, en utilisant des résultats de matrices aléatoires et de géométrie stochastique. Les SBs et les utilisateurs sont modélisés par deux PPP indépendants et le précodage RSFB est utilisé. L'EE est dérivée d'un modèle de consommation de puissance linéaire. Les simulations de Monte Carlo montrent que les expressions analytiques sont précises même pour un nombre faible d'antennes et d'utilisateurs. De plus, les courbes d'EE-ESuS ont une grande partie linéaire avant une forte décroissante de l'EE, comme pour les réseaux hexagonaux. Les résultats montrent également que le précodeur RSFB offre de meilleurs performances que le précodeur forçage à zéro (FZ), qui est typiquement utilisé dans la literature. Les résultats numériques pour le précodeur RSFB montrent que déployer plus de SBs ou d'antennes aux BSs augmente l'ESuS, mais que le gain dépend du rapport des densités SB-utilisateurs et du nombre d'antennes lorsque la densité de l'utilisateur est fixe. L'EE augmente seulement lorsque l'augmentation de l'ESuS est plus importante que l'augmentation de la consommation d'énergie par unité de surface. D'autre part, lorsque la densité d'utilisateur augmente, l'ESuS dans la région limitée par les interférences peut être améliorée en déployant davantage de SB sans sacrifier l'EE et le débit ergodique des utilisateurs

Energy Efficiency-Spectral Efficiency Trade-off in Interference-Limited Wireless Networks with Shadowing

Séminaire des jeudis de la com' de l'équipe SCNThis presentation deals with the energy-efficiency spectral-efficiency (EE-SE) tradeoff in regular hexagonal interference-limited networks. We aim to characterize the EE-SE region when non negligible static circuitry power consumption is assumed and when several frequency reuse factors as well as shadowing are taken into account. Our contribution is three-fold: i) a parametric expression of the interference to signal ratio, a.k.a. f-parameter, obtained with a curve fitting approach is proposed, ii) the epsilon-EE-SE tradeoff is then studied when several frequency reuse factors are considered and iii) a new characterization, called the EE-SE tradeoff, is proposed when shadowing is considered. This definition relies on the outage capacity achievable and its corresponding EE and remains particularly useful when long-term fading is present

Clustering for High Accuracy Coverage Mapping

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Performance Evaluation of Covariance Tapering for Coverage Mapping

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Compromis efficacités énergétique et spectrale du précodeur SLNR dans un réseau cellulaire aléatoire

National audienceThe performance of the precoder maximizing the signal-to-leakage-plus-noise ratio (SLNR) is investigated in terms of tradeoff between energy and area spectral efficiencies (EE-ASE) in random networks. The comparison between the well known zero-forcing precoder and SLNR precoder is considered with static power consumption of base stations. Moreover, an upper-bound on ASE is proposed based on the large random matrix theory.Les performances du précodeur maximisant le rapport signal sur bruit plus fuite (SLNR) sont étudiées d'un point de vue du compromis entre les efficacités energétique (EE) et spectrale par unité de surface (ASE) dans les réseaux aléatoires. La comparaison avec le précodeur de forçage à zéro est traitée en prenant en compte la puissance statique consommée par les stations de base. De plus, nous proposons une borne supérieure analytique de l'ASE issue d'une étude asymptotique avec les grandes matrices aléatoires

Energy Efficiency-Area Spectral Efficiency Tradeoff in PPP Network with SLNR Precoder

International audienceSignal-to-leakage-and-noise ratio (SLNR) is a pro\-mising criterion for linear precoder design in multiuser multiple-input multiple-output systems. In this paper, an expression of a precoder maximizing the SLNR based on the generalized Rayleigh quotient theorem is derived for cellular networks. Compared with the conventional SLNR precoders, we consider the non-homogeneous average received signal-to-noise ratio (SNR) condition due to the random network geometry and the leakage to other cells. We aim at characterizing the energy efficiency-area spectral efficiency (EE-ASE) region for a Poisson point process (PPP) network using this precoder for different base station (BS) densities and number of BS antennas when static power consumption is considered. Simulation results demonstrate the superiority of the SLNR precoder over zero-forcing (ZF) precoder in terms of EE-ASE tradeoff. Our contribution lies in the analysis of the performance of SLNR precoder in PPP networks in terms of tradeoff between EE and SE, and in the comparison between the well known ZF precoder and SLNR precoder, when static power consumption is considered

Energy Efficiency-Spectral Efficiency Tradeoff in Interference-Limited Wireless Networks with Shadowing

International audienceThis paper deals with the energy-efficiency spectral-efficiency (EE-SE) tradeoff in regular hexagonal interference-limited networks. We aim to characterize the EE-SE region when non negligible static circuitry power consumption is assumed and when several frequency reuse factors as well as shadowing are taken into account. Our contribution is three-fold: i) a parametric expression of the interference to signal ratio, a.k.a. f-parameter, obtained with a curve fitting approach is proposed, ii) the EE-SE tradeoff is then studied when several frequency reuse factors are considered and iii) a new characterization, called the $\epsilon$-EE-SE tradeoff, is proposed when shadowing is considered. This definition relies on the outage capacity achievable and its corresponding EE and remains particularly useful when long-term fading is present

The knowledge level of rheumatoid arthritis patients about their disease in a developing country: A study in 168 Bangladeshi RA patients

Objectives To assess disease-related knowledge of rheumatoid arthritis (RA) patients Patients and methods Consecutive RA patients were invited from the rheumatology departments of BSMM University, Dhaka, Bangladesh. The Bangla version of the Patient Knowledge Questionnaire (B-PKQ) was used. Correlations between the B-PKQ scores and clinical-demographic data were measured using Pearson’s correlation coefficient. Impact of independent variables on the level of knowledge about RA was analyzed through multiple regression analysis. Possible explanatory variables included the following: age, disease duration, formal education level, and Bangla Health Assessment Questionnaire (B-HAQ) score. Analysis of variance (ANOVA) was used to test the difference between demographical, clinical, and socioeconomic variables. For statistical analysis, SPSS statistics version 20 was used. Results A total of 168 RA patients could be included. The mean B-PKQ score was 9.84 (range 1–20) from a possible maximum of 30. The mean time for answering the questionnaire was 24.3 min (range 15–34). Low scores were observed in all domains but the lowest were in medications and joint protection/energy conservation. Knowledge level was higher (15.5) in 6 patients who had RA education before enrollment. B-PKQ showed positive correlation with education level (r = 0.338) and negative correlation with HAQ (r = −0.169). The B-PKQ showed no correlation with age, disease duration, having first degree family member with RA, education from other sources (neighbor, RA patient, nurses), or information from mass media. Conclusions Disease-related knowledge of Bangladeshi RA patients was poor in all domains. Using these findings, improved education and knowledge will result in better disease control