Proactive Caching for Energy-Efficiency in Wireless Networks: A Markov Decision Process Approach

Content caching in wireless networks provides a substantial opportunity to trade off low cost memory storage with energy consumption, yet finding the optimal causal policy with low computational complexity remains a challenge. This paper models the Joint Pushing and Caching (JPC) problem as a Markov Decision Process (MDP) and provides a solution to determine the optimal randomized policy. A novel approach to decouple the influence from buffer occupancy and user requests is proposed to turn the high-dimensional optimization problem into three low-dimensional ones. Furthermore, a non-iterative algorithm to solve one of the sub-problems is presented, exploiting a structural property we found as \textit{generalized monotonicity}, and hence significantly reduces the computational complexity. The result attains close performance in comparison with theoretical bounds from non-practical policies, while benefiting from higher time efficiency than the unadapted MDP solution.Comment: 6 pages, 6 figures, submitted to IEEE International Conference on Communications 201

Evaluativist Accounts of Pain's Unpleasantness

Evaluativism is best thought of as a way of enriching a perceptual view of pain to account for pain’s unpleasantness or painfulness. Once it was common for philosophers to contrast pains with perceptual experiences (McGinn 1982; Rorty 1980). It was thought that perceptual experiences were intentional (or content-bearing, or about something), whereas pains were representationally blank. But today many of us reject this contrast. For us, your having a pain in your toe is a matter not of your sensing “pain-ly” or encountering a sense-datum, but of your having an interoceptive experience representing (accurately or inaccurately) that your toe is in a particular experience-independent condition, such as undergoing a certain “disturbance” or being damaged or in danger (Armstrong 1962; Tye 1995). But even if such representational content makes an experience a pain, a further ingredient seems required to make the pain unpleasant. According to evaluativism, the further ingredient is the experience’s possession of evaluative content: its representing the bodily condition as bad for the subject. In this chapter, I elaborate evaluativism, locate it among alternatives, and explain its attractions and challenges

Cross Layer Resource Allocation in H-CRAN with Spectrum and Energy Cooperation

5G and beyond wireless networks are the upcoming evolution for the current cellular networks to provide the essential requirement of future demands such as high data rate, low energy consumption, and low latency to provide seamless communication for the emerging applications. Heterogeneous cloud radio access network (H-CRAN) is envisioned as a new trend of 5G that uses the advantages of heterogeneous and cloud radio access networks to enhance both the spectral and energy efficiency. In this paper, building on the notion of effective capacity (EC), we propose a framework in non-orthogonal multiple access (NOMA)-based H-CRAN to meet these demands simultaneously. Our proposed approach is to maximize the effective energy efficiency (EEE) while considering spectrum and power cooperation between macro base station (MBS) and radio remote heads (RRHs). To solve the formulated problem and to make it more tractable, we transform the original problem into an equivalent subtractive form via Dinkelbach algorithm. Afterwards, the combinational framework of distributed stable matching and successive convex algorithm (SCA) is then adopted to obtain the solution of the equivalent problem. Hereby, we propose an efficient resource allocation scheme to maximize energy efficiency while maintaining the delay quality of service (QoS) requirements for the all users. The simulation results show that the proposed algorithm can provide a non-trivial trade-off between delay and energy efficiency in NOMA H-CRAN systems in terms of EC and EEE and the spectrum and power cooperation improves EEE of the proposed network. Moreover, our proposed solution complexity is much lower than the optimal solution and it suffers a very limited gap compared to the optimal method

Μελέτη Σύγχρονων Τεχνολογιών Επικοινωνίας Πελάτη-Εξυπηρέτη

Η διπλωματική αυτή εργασία έχει ως στόχο τη μελέτη των διαφόρων τεχνολογιών επικοινωνίας που έχουν αναπτυχθεί για το μοντέλο πελάτη-εξυπηρέτη. Στο αρχικό μοντέλο την επικοινωνία ξεκινούσε ο πελάτης κάνοντας ρητές αιτήσεις και ο εξυπηρέτης έστελνε, εν συνεχεία, τις απαντήσεις του. Αυτός ο τρόπος επικοινωνίας είναι ξεκάθαρος και στο HTTP πρωτόκολλο το οποίο αποτελεί μέχρι και σήμερα το βασικό τρόπο επικοινωνίας ανάμεσα σε πελάτη και εξυπηρέτη. Η ανάγκη για πιο δυναμικές ιστοσελίδες, οι οποίες θα ενημερώνονταν σε πραγματικό χρόνο, έδωσε ώθηση σε νέες τεχνολογίες και πρωτόκολλα, τα οποία δουλεύουν πάνω από το HTTP ή το αναβαθμίζουν. Κατ’ αρχήν, μια πολύ σημαντική εξέλιξη ήταν η ανάπτυξη του AJAX. Η προσέγγιση αυτή αν και δεν άλλαξε την κατεύθυνση της επικοινωνίας πελάτη-εξυπηρέτη, βελτίωσε πολύ τον τρόπο που παρουσιάζονται οι σελίδες στο χρήστη - πλέον τα δεδομένα μοιάζουν να είναι πραγματικού χρόνου. Οι εφαρμογές, όμως, καθώς και η ανάγκη υποστήριξης πολλών ταυτόχρονων χρηστών, απαιτούσαν κάτι περισσότερο, μια τεχνολογία η οποία θα κάνει αυτόματη προώθηση των δεδομένων από τον εξυπηρέτη στον πελάτη. Οι δύο βασικότεροι πρωταγωνιστές σήμερα σε αυτή την προσπάθεια είναι η προσέγγιση COMET και τα API Server Sent Events και WebSocket της HTML5. Στην παρούσα εργασία γίνεται μια επισκόπηση των σημαντικότερων τεχνολογιών όπως αυτές προτάθηκαν στο πέρασμα του χρόνου. Πιο συγκεκριμένα, ελέγχεται τι υποστήριξη υπάρχει στην πλευρά του πελάτη-φυλλομετρητή, ποια είναι τα πλεονεκτήματα και τα μειονεκτήματα της κάθε τεχνολογίας και πώς υποστηρίζονται από τους διάφορους εξυπηρέτες εφαρμογών. Στην πλευρά του εξυπηρέτη έγινε ένα πείραμα ελέγχου φόρτου το οποίο επιβεβαιώνει το γεγονός ότι το πιο σύγχρονο API, το WebSocket, έχει χαμηλότερη καθυστέρηση και κλιμακώνεται πολύ καλύτερα από το COMET.This diploma thesis aims at studying the various communication technologies that have been developed to support the client-server model. In the original model, the communication was initiated explicitly by a client request, and the server responded with an answer. This way of communication is clear in the HTTP protocol, which remains the main way of communication between a client and a webserver until today. The need for more dynamic websites, which will be updated in real time, gave impetus to new technologies and protocols, which work over HTTP or upgrade it. Firstly, a very important step was the development of AJAX. This approach, although it did not change the direction of the client-server communication, it greatly improved the way webpages are presented to the user - data seem to be real time. Current applications, however, and the need to support multiple concurrent users, required something more, a technology that will automatically forward data from the server to the client. The two main protagonists today in this effort are the COMET approach and two APIs introduced in HTML5, Server Sent Events and WebSocket API. This thesis presents an overview of the major technologies presented through the years to support the client-server communication. More specifically, it studies the support given on the client-side (browser), the advantages and disadvantages of each technology, and how they it is implemented by different servers, application and dedicated ones. On the server side, a load test experiment was conducted which confirms the fact that the latest API, the WebSocket, has lower delay and scales much better than the COMET, which makes it the most promising technology for RIA

Estratégias de design de camada intermédia e cooperativa para redes sem fios energeticamente eficientes

Doutoramento conjunto MAP-i em InformáticaThe promise of a truly mobile experience is to have the freedom to roam around anywhere and not be bound to a single location. However, the energy required to keep mobile devices connected to the network over extended periods of time quickly dissipates. In fact, energy is a critical resource in the design of wireless networks since wireless devices are usually powered by batteries. Furthermore, multi-standard mobile devices are allowing users to enjoy higher data rates with ubiquitous connectivity. However, the bene ts gained from multiple interfaces come at a cost in terms of energy consumption having profound e ect on the mobile battery lifetime and standby time. This concern is rea rmed by the fact that battery lifetime is one of the top reasons why consumers are deterred from using advanced multimedia services on their mobile on a frequent basis. In order to secure market penetration for next generation services energy e ciency needs to be placed at the forefront of system design. However, despite recent e orts, energy compliant features in legacy technologies are still in its infancy, and new disruptive architectures coupled with interdisciplinary design approaches are required in order to not only promote the energy gain within a single protocol layer, but to enhance the energy gain from a holistic perspective. A promising approach is cooperative smart systems, that in addition to exploiting context information, are entities that are able to form a coalition and cooperate in order to achieve a common goal. Migrating from this baseline, this thesis investigates how these technology paradigm can be applied towards reducing the energy consumption in mobile networks. In addition, we introduce an additional energy saving dimension by adopting an interlayer design so that protocol layers are designed to work in synergy with the host system, rather than independently, for harnessing energy. In this work, we exploit context information, cooperation and inter-layer design for developing new energy e cient and technology agnostic building blocks for mobile networks. These technology enablers include energy e cient node discovery and short-range cooperation for energy saving in mobile handsets, complemented by energy-aware smart scheduling for promoting energy saving on the network side. Analytical and simulations results were obtained, and veri ed in the lab on a real hardware testbed. Results have shown that up to 50% energy saving could be obtained.A promessa de uma experiência realmente móvel é de ter a liberdade de deambular por qualquer sítio e não estar preso a um único local. No entanto, a energia requerida para manter dispositivos móveis conectados à rede, num período extenso de tempo, o mesmo rapidamente se dissipa. Na realidade, a energia é um recurso crítico no design de redes sem fios, uma vez que esses dispositivos são alimentados por baterias. Para além disso, dispositivos móveis multi-standard permitem que os utilizadores desfrutem de elevadas taxas de dados com conectividade omnipresente. No entanto, as vantagens adquiridas pelas múltiplas interfaces, imputa uma despesa, sendo essa um consumo maior de energia, numa era onde os dispositivos móveis têm de ser energicamente complacentes. Esta preocupação é reafirmada pelo facto de que a vida da bateria é uma das principais razões que impede os utilizadores de usufruir e utilizar de serviços de multimédia mais avançados nos seus dispositivos, numa base frequente. De forma a assegurar a entrada no mercado para serviços da próxima geração, eficiência energética tem de ser colocada na vanguarda do design de sistemas. No entanto, apesar de esforços recentes, funcionalidades que cumpram os requisitos energéticos em tecnologias "legacy" ainda estão nos seus primórdios e novas abordagens disruptivas são requeridas, juntamente com abordagem de design interdisciplinar, de forma a aproveitar a poupança energética das diversas camadas protocolares. Uma bordagem promissora são os sistemas de cooperação inteligente, que exploram não são contexto da informação, mas também as entidades que são igualmente capazes de formar uma coligação e cooperam de forma a atingir um objectivo comum. Migrar a partir destas referências, esta tese investiga como é que este paradigma tecnológico pode ser aplicado para reduzir a potência e consumo de energia em redes móveis. Para além disso, introduzimos uma dimensão de poupança energética adicional, para adopção de design de camadas intermédias, de forma a que as camadas de protocolos sejam concebidas para trabalhar em sinergia com o sistema anfitrião, ao invés de independentemente, para aproveitamento de energia. Neste trabalho, nós exploramos o contexto da informação, cooperação e design de camadas intermédias para desenvolver blocos de construção energicamente eficientes e tecnologias agnósticas para redes móveis. Estes habilitadores (enablers) tecnológicos incluem um nó de descoberta de energia eficiente e cooperação de curto alcance para poupança energética em aparelhos móveis, complementado com agendamento inteligente, energicamente consciente, de forma a promover a poupança de energia do lado da rede. Analiticamente e simultaneamente, foram obtidos resultados e verificados em laboratório, num modelo de hardware protótipo. Resultados demonstram que pode ser obtido uma poupança energética acima dos 50%