Planning Solar in Energy-managed Cellular Networks

There has been a lot of interest recently on the energy efficiency and environmental impact of wireless networks. Given that the base stations are the network elements that use most of this energy, much research has dealt with ways to reduce the energy used by the base stations by turning them off during periods of low load. In addition to this, installing a solar harvesting sys- tem composed of solar panels, batteries, charge con- trollers and inverters is another way to further reduce the network environmental impact and some research has been dealing with this for individual base stations. In this paper, we show that both techniques are tightly coupled. We propose a mathematical model that captures the synergy between solar installation over a network and the dynamic operation of energy-managed base stations. We study the interactions between the two methods for networks of hundreds of base stations and show that the order in which each method is intro- duced into the system does make a difference in terms of cost and performance. We also show that installing solar is not always the best solution even when the unit cost of the solar energy is smaller than the grid cost. We conclude that planning the solar installation and energy management of the base stations have to be done jointly

Efficient Heuristic for Resource Allocation in Zero-forcing OFDMA-SDMA Systems with Minimum Rate Constraints

4G wireless access systems require high spectral efficiency to support the ever increasing number of users and data rates for real time applications. Multi-antenna OFDM-SDMA systems can provide the required high spectral efficiency and dynamic usage of the channel, but the resource allocation process becomes extremely complex because of the augmented degrees of freedom. In this paper, we propose two heuristics to solve the resource allocation problem that have very low computational complexity and give performances not far from the optimal. The proposed heuristics select a set of users for each subchannel, but contrary to the reported methods that solve the throughput maximization problem, our heuristics consider the set of real-time (RT) users to ensure that their minimum rate requirements are met. We compare the heuristics' performance against an upper bound and other methods proposed in the literature and find that they give a somewhat lower performance, but support a wider range of minimum rates while reducing the computational complexity. The gap between the objective achieved by the heuristics and the upper bound is not large. In our experiments this gap is 10.7% averaging over all performed numerical evaluations for all system configurations. The increase in the range of the supported minimum rates when compared with a method reported in the literature is 14.6% on average.Comment: 8 figure

Le statut professionnel des éducateurs physiques à la Commission des écoles catholiques de Montréal de 1938 à 1965

Cette recherche présente, à partir d'un cadre sociologique, l'évolution du statut professionnel des enseignants en éducation physique à la Commission des écoles catholiques de Montréal pour la période de 1938 à 1965. S'appuyant sur les principales caractéristiques des professions et analysant le processus de professionnalisation, les auteurs montrent que le statut professionnel de ces enseignants a peu évolué au cours de cette période.It is within a sociological framework that the authors present a study of the evolution of physical education teachers in the Montreal Catholic School Board during the period 1938 to 1965. The authors base their work on the principal characteristics of professions and on an analysis of the professionalization process. Findings show that the professional status of these teachers has changed little over this period.Partiendo de un marco sociológico, este estudio présenta la evolución del nivel profesional de los profesores de educación fïsica en la Comisiôn de escuelas católicas de Montréal durante el período 1938 a 1965. Apoyándose en las principales características de las profesiones y analizando el proceso de profesionalización, los autores muestran que el nivel profesional de estos profesores ha evolucionado poco durante este periodo.Diëse Untersuchung stellt, ausgehend von einem soziologischen Rahmen, die Entwicklung des Berufsstatus der Lehrkràfte fur Kërpererziehung an der Montrealer zentralen Schulbehörde fur die Zeit von 1938 bis 1965 dar. Die Autoren stützen sich auf die wichtigsten Merkmale der Berufe und untersuchen den Prozess der akademischen Anerkennung; dabei zeigen sie auf, dass sich der Berufsstatus dieser Lehrkräfte im Lauf der gegebenen Zeitspanne wenig verbessert hat

Pour une cartographie des parties prenantes fondée sur leur engagement : une application aux sociétaires d'une banque mutualiste française

The aim of this article is to propose a new classification of stakeholders based on the concept of commitment. Commitment is analysed as a social and organisational learning process shared between managers and their stakeholders. This commitment is a necessary condition - even if it is not sufficient - to the corporate social responsibility of the business. Applied to the membership of a French mutual bank in order to identify the members' varying levels of commitment, this new mapping technique can help managers to adapt their practices to the degree of commitment of each identified group of members, and to modify their financial products and communications to foster commitment among as many of these groups as possible.L'objectif de cet article est de proposer une nouvelle classification des parties prenantes fondée sur le concept d'engagement. L'engagement est analysé comme un processus d'apprentissage organisationnel et social entre les dirigeants et leurs parties prenantes. Cet engagement est une condition nécessaire -­ même si elle n'est pas suffisante -­ à la responsabilité globale de l'entreprise. Appliqué au sociétariat d'une banque mutualiste française pour lui permettre d'identifier leurs sociétaires plus ou moins engagés, cette nouvelle cartographie peut aider ses dirigeants, d'une part à adapter leurs relations au degré d'engagement de chaque groupe de sociétaires identifiés, et d'autre part à adapter leurs produits financiers et leur communication pour favoriser cet engagement auprès du plus grand nombre de ces groupes

An analytical model for jitter in IP networks

ABSTRACT: Traditionally, IP network planning and design is mostly based on the average delay or loss constraints which can often be easily calculated. Jitter, on the other hand, is much more difficult to evaluate, but it is particularly important to manage the QoS of real-time and interactive services such as VoIP and streaming video. In this paper, we present simple formulas for the jitter of Poisson traffic in a single queue that can be quickly calculated . It takes into account the packets delay correlation and also the correlation of tandem queues that have a significant impact on the end-to-end jitter. We then extend them to the end-to-end jitter of a tagged stream based on a tandem queueing network. The results given by the model are then compared with event-driven simulations. We find that they are very accurate for Poisson traffic over a wide range of traffic loads and more importantly that they yield conservative values for the jitter so that they can be used in network design procedures. We also find some very counter-intuitive results. We show that jitter actually decreases with increasing load and the total jitter on a path depends on the position of congested links on that path. We finally point out some consequences of these results for network design procedures