Do NGAN Economics Allow for Network Competition?

This article analyses whether the economics of Next Generation Access Networks for broadband services allow for the market to be competitive in Europe in absence of ex ante regulation of wholesale network access. This is done by two methods: cost modelling of operators with different technologies and market shares, and the review of market entry decisions by European operators. Both methods arrive to the same conclusions: a) network economics allow competition in most geographic areas between two to four operators; b) the economics of NGANs will lead to different industry structures in different geographic areas; c) even where there is not a pre-existing cable operator, other entrants can successfully deploy their networks and challenge the incumbent telecommunications operator; and d) price levels and availability of ducts greatly increase the degree of potential competition.regulation, competition, broadband, access networks, fibre optic.

Many Voices. Intertextualities as an Underlying Cultural Theory of ‘Escola do Porto’

Several pedagogical experiences in architecture bring literary inputs to teaching, through a multidisciplinary curriculum with courses explicitly focusing on these relationships. Other pedagogical scenarios, even if admitting the relevance of literature references into design, have blended these semantic and structural translations implicitly in their teaching processes. The main goal of this article is to acknowledge the many voices of an implicit transfer between literature and architecture within a learning scenario at the Escola Superior de Belas-Artes do Porto (Fine Arts School in Porto) along with practice.Here, a process of modern acculturation was key, while aiming at modernity filtered by the local culture and tradition, and vice versa. One of its essential figures, Fernando Távora (1923-2005), recurrently quoted Fernando Pessoa while sharing his ideas with students. Reflecting on life and architecture, space and the world, Távora’s discourse was intuitively pedagogical. Fernando Távora embedded literature in his learning and teaching, while being highly engaged with everyday experience and practice. Távora integrated in his lifelong learning the writings of Fernando Pessoa, which among others implicitly contributed to the School of Porto.  The article reflects on written essays of Fernando Távora and Alexandre Alves Costa and on architectural works by Álvaro Siza and Eduardo Souto de Moura. For the first, we will consider a specific period in the school, when architects had to complete written and designed pieces to become professors, while for the latter we will pick few architectural examples that illustrate the main argument of this paper

A Practical Cooperative Multicell MIMO-OFDMA Network Based on Rank Coordination

An important challenge of wireless networks is to boost the cell edge performance and enable multi-stream transmissions to cell edge users. Interference mitigation techniques relying on multiple antennas and coordination among cells are nowadays heavily studied in the literature. Typical strategies in OFDMA networks include coordinated scheduling, beamforming and power control. In this paper, we propose a novel and practical type of coordination for OFDMA downlink networks relying on multiple antennas at the transmitter and the receiver. The transmission ranks, i.e.\ the number of transmitted streams, and the user scheduling in all cells are jointly optimized in order to maximize a network utility function accounting for fairness among users. A distributed coordinated scheduler motivated by an interference pricing mechanism and relying on a master-slave architecture is introduced. The proposed scheme is operated based on the user report of a recommended rank for the interfering cells accounting for the receiver interference suppression capability. It incurs a very low feedback and backhaul overhead and enables efficient link adaptation. It is moreover robust to channel measurement errors and applicable to both open-loop and closed-loop MIMO operations. A 20% cell edge performance gain over uncoordinated LTE-A system is shown through system level simulations.Comment: IEEE Transactions or Wireless Communications, Accepted for Publicatio

Data driven spatio-temporal analysis of e-cargo bike network in Lisbon and its expansion: The Yoob case study

The adoption of more environmentally friendly and sustainable fleets for last-mile parcel delivery within large urban centers has been on the rise. Cargo bikes have been the most common alternative. The implementation of this type of fleet has proven to bring benefits, but has evidenced some limitations. The infrastructure network, which supports urban logistics, had to adapt to respond to the requirements of this new type of fleet. The implementation of micro-hubs and nano-hubs was the solution. Our study has two main objectives. The first objective is to perform a spatiotemporal characterization of fleet behavior, by conducting a case study where we explored the data from YOOB (a last mile delivery logistics start-up that operates in the Lisbon area and outskirts) e-cargo bike fleet. And the second is to identify potential expansion locations to the establishment of new hubs. The work procedures followed the CRIPS-DM methodology and the collected data was based on a 4-month period (January to April 2022). By adopting data science and machine learning techniques, five types of performances of YOOB fleet were identified, with variations in distances traveled, times, volumes transported and speeds. In the perspective of expanding YOOB's e-cargo bike network, three new locations in Lisbon were signaled for potential new hub installation.A adoção de frotas mais ecológicas e sustentáveis para a distribuição das encomendas na última milha dentro dos grandes centros urbanos tem vindo a crescer. As bicicletas de carga têm sido a alternativa mais comum. A implementação deste tipo de frotas, demonstrou trazer benefícios, mas evidenciou algumas limitações. A rede de infraestruturas, que serve de suporte á logística urbana, teve de se adaptar para poder responder às necessidades deste novo tipo de frotas. A implementação de microhubs e nano-hubs foram a alternativa. O nosso estudo tem dois objetivos principais. O primeiro objetivo é o de fazer uma caracterização espácio temporal dos comportamentos da frota, através de um estudo de caso onde efetuámos a exploração dos dados da frota de e-cargo bike da YOOB (start-up logística de entregas na última milha que atua na área de Lisboa e na periferia). E o segundo consiste em identificar potenciais locais de expansão para a instalação de novos hubs no mesmo estudo de caso. Nos processos de trabalho foi seguida a metodologia CRISP-DM e os dados recolhidos foram referentes a um período de 4 meses (Janeiro a Abril de 2022). Com recurso a técnicas de ciência dos dados e aprendizagem automática, foram identificados cinco tipos de desempenhos da frota da YOOB, com variações em distâncias percorridas, tempos efetuados, volumes transportados e velocidades praticadas. Numa perspetiva de expansão da rede de e-cargo bike da YOOB, forma identificados três novos locais na cidade de Lisboa para a instalação potencial de novos hubs

A biophysical model explains the spontaneous bursting behavior in the developing retina

During early development, waves of activity propagate across the retina and play a key role in the proper wiring of the early visual system. During the stage II these waves are triggered by a transient network of neurons, called Starburst Amacrine Cells (SACs), showing a bursting activity which disappears upon further maturation. While several models have attempted to reproduce retinal waves, none of them is able to mimic the rhythmic autonomous bursting of individual SACs and reveal how these cells change their intrinsic properties during development. Here, we introduce a mathematical model, grounded on biophysics, which enables us to reproduce the bursting activity of SACs and to propose a plausible, generic and robust, mechanism that generates it. The core parameters controlling repetitive firing are fast depolarizing $V$-gated calcium channels and hyperpolarizing $V$-gated potassium channels. The quiescent phase of bursting is controlled by a slow after hyperpolarization (sAHP), mediated by calcium-dependent potassium channels. Based on a bifurcation analysis we show how biophysical parameters, regulating calcium and potassium activity, control the spontaneously occurring fast oscillatory activity followed by long refractory periods in individual SACs. We make a testable experimental prediction on the role of voltage-dependent potassium channels on the excitability properties of SACs and on the evolution of this excitability along development. We also propose an explanation on how SACs can exhibit a large variability in their bursting periods, as observed experimentally within a SACs network as well as across different species, yet based on a simple, unique, mechanism. As we discuss, these observations at the cellular level have a deep impact on the retinal waves description.Comment: 25 pages, 13 figures, submitte

Controller and actuator of three independent DC motors In closed loop

This article describes a solution for a high power controller and actuator of three DC motors in closed loop. This controller can be applied to omnidirectional platform solutions using three motorised Swedish wheels as used by several RobCup MSL robots and Minho omnidirectional Wheelchair. Some existing controllers in the market are reviewed pointing out their characteristics and comparing them with the proposed solution. Operational characteristics and developed algorithms of the proposed system are fully disclosed

A Rational Approach to Cryptographic Protocols

This work initiates an analysis of several cryptographic protocols from a rational point of view using a game-theoretical approach, which allows us to represent not only the protocols but also possible misbehaviours of parties. Concretely, several concepts of two-person games and of two-party cryptographic protocols are here combined in order to model the latters as the formers. One of the main advantages of analysing a cryptographic protocol in the game-theory setting is the possibility of describing improved and stronger cryptographic solutions because possible adversarial behaviours may be taken into account directly. With those tools, protocols can be studied in a malicious model in order to find equilibrium conditions that make possible to protect honest parties against all possible strategies of adversaries

Portuguese Architecture in Transit(ion)

In the final years of the Estado Novo regime (1933–1974), the Amsterdam Town Hall International Competition of 1967 presents the opportunity for seven teams of Portuguese architects to confront their own reality and rehearse distinct visions of building and city. From a national context, politically and geographically distant from the heart of the disciplinary debate of the 1960s, the proposals submitted set the terms on which Portugal competes in Amsterdam, revealing in the diversity of approaches and experiences forwarded by this new generation of architects the vitality of Portuguese architecture on its path to internationalisation. This article retraces the Portuguese participation in the Amsterdam Town Hall Competition to refute the generalised idea of cultural mismatch with the European scene of the time and assesses the impact of this particular event on the transition of Portuguese architecture to international recognition, an impact that Portuguese architecture historiography has to this day completely ignored