News

Talk by Georgios Kollias

06-03-2017
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Georgios Kollias who is currently a PhD candidate at the Technical University of Catalonia (UPC) will present part of his work on Tuesday, March 7th , on the 9th floor (901 room) of the Evelpidon Str. building (graduate program building) of the Athens University of Economics and Business (AUEB).

Title: Self-Organized Solutions in Future Heterogeneous Cellular Networks

Abstract: The ever increasing demands of cellular users for seamless connectivity anytime and anywhere forced network operators to search for solutions that would increase their capacity, expand the coverage of their networks, improve the offered quality of theirs services and simultaneously ensure high profits for them. The answer is the large scale deployment of low power nodes (i.e small cells), that can offer high rates in limited areas and therefore boost networks' capacity by covering areas with increased traffic, or areas with limited macro coverage. The result will be the transformation of traditional macro only networks to heterogeneous (HetNets) due to the existence of multiple tiers consisting of cells with different characteristics (e.g micro, pico, metro, femto, etc.).
The need for more efficient and flexible management of future HetNets as well as the necessity for continuous monitoring of the performance and optimization of their operation, is the reason for the integration of Self-Organized solutions under the Self-Organized Network (SON) concept. The aim of SONs is to replace the human factor with functions that will have the ability to handle dynamics, meaning variations in traffic or in network conditions, immediately.
Motivated by the aforementioned changes in cellular networks, the aim of this presentation is to propose novel schemes and algorithms under the SON umbrella and is divided in three parts:

Ph.D. defense by Xenofon Vasilakos

27-02-2017
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Xenofon Vasilakos will present his Ph.D. thesis on Wednesday, March 1st, 11:00AM EET, at Teleconference & e-learning room, 4th floor, Antoniadou section, central building complex of the Athens University of Economics and Business. Title and abstract follow.

Title: Mobility-based Proactive Caching Models for Addressing Niche Mobile Demand and Scalable ICN Name Resolution Designs

Abstract: Since its original conception, the Internet has undergone a series of radical technological breakthroughs and usage expansions. From the perspective of its users, it is a global framework for sharing information among millions of fixed and mobile users. However, its legacy architecture poses serious functionality limitations or inefficiencies to information sharing & retrieval. At the same time, the patched mobility support over the legacy architecture and even the intrinsic mobility support of Future Internet architectures that adapt the Information-Centric Networking (ICN) paradigm are not enough to sufficiently address the Quality-of-Service (QoS) requirements and the desired user-perceived Quality-of-Experience (QoE) levels in contemporary mobile application scenarios. The former problems get further aggravated by the unprecedented and continuously increasing numbers of the different Information Objects (IOs) and mobile devices in the Internet, as well as the corresponding high content resolution traffic and mobile traffic volumes.
The main contribution of this thesis lies in the design of efficient proactive caching models for enhancing seamless mobility that run at the application layer of any underlying network architecture or within the network layer of ICN architectures. Our main model regards an Efficient Mobility-based Caching (EMC) scheme for addressing niche mobile demand along with popularity-based and legacy caching model extensions.
Opposite to other proactive solutions, which focus exclusively on popular content, our proposed distributed design targets less popular or personalised content requests by prefetching and caching the desired information locally in small cells based on aggregated user mobility prediction information and a local cache congestion pricing scheme. Such niche demand, particularly for video content, represents a significant 20–40% of demand in the Internet and follows a growing trend. Due to its novel design, EMC can directly address niche demand and get easily extended to make a joint use of content popularity information with the novelty of dynamically balancing the influence of mobility prediction and content popularity information on local cache actions. Based on thorough performance evaluation simulations for exploring different demand levels, video catalogues and mobility scenarios, including human walking and automobile mobility, we show that the gains from mobility prediction can be high and able to adapt well to temporal locality due to the localised and short timescale character of the exploited mobility prediction measurements, exceeding cache gains from popularity-only caching. Moreover, the performance of our model can be further improved by adapting cache replacements at the cost of an added computational overhead.
Additionally, this thesis makes a contribution towards a feasible and globally scalable ICN Name Resolution System (NRS) to facilitate information sharing & retrieval in ICN. The contribution lies in certain design and performance aspects related to the structure of the underlying inter-domain topology in the Internet and specifically to a) the design of the hierarchical overlay routing mechanism that underlies the Distributed Hash Table-based Name Resolution System (DHT-NRS) and b) a thorough performance quantification study of DHT-NRS and other cutting-edge ICN NRSs with respect to load distribution and routing policy compliance across the Internet topology.

Vaggelis Douros will visit MMLab

01-02-2017
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Dr. Vaggelis Douros, a post-doctoral researcher of the Institute for Networked Systems, RWTH Aachen University (and a Ph.D. alumnus of MMLab), will visit us from 03 February till 07 February. He will give us a seminar on Tuesday 07 February, room: 901, time: 9:30-11:00. The title and the abstract of the seminar follows:

Caching Games between Content Providers and Internet Service Providers

Abstract
We consider a scenario where an Internet Service Provider (ISP) serves users that choose digital content among M Content Providers (CP). In the status quo, these users pay both access fees to the ISP and content fees to each chosen CP; however, neither the ISP nor the CPs share their profit. We revisit this model by introducing a different business model where the ISP and the CP may have motivation to collaborate in the framework of caching. The key idea is that the ISP deploys a cache for a CP provided that they share both the deployment cost and the additional profit that arises due to caching. Under the prism of coalitional games, our contributions include the application of the Shapley value for a fair splitting of the profit, the stability analysis of the coalition and the derivation of closed-form formulas for the optimal caching policy. Our model captures not only the case of non-overlapping contents among the CPs, but also the more challenging case of overlapping contents; for the latter case, a non-cooperative game among the CPs is introduced and analyzed to capture the negative externality on the demand of a particular CP when caches for other CPs are deployed
This is a joint work with S. Elayoubi, E. Altman, and Y. Hayel.