New architectural and design approaches for radio access networks have appeared with the introduction of network virtualization in the wireless domain. One of these approaches splits the wireless network infrastructure into isolated virtual slices under their own management, requirements, and characteristics. Despite the advances in wireless virtualization, there are still many open issues regarding the resource allocation and isolation of wireless slices. Because of the dynamics and shared nature of the wireless medium, guaranteeing that the traffic on one slice will not affect the traffic on the others has proven to be difficult. In this paper, we focus on the detailed definition of the problem, discussing its challenges. We also provide a review of existing works that deal with the problem, analyzing how new trends such as software defined networking and network function virtualization can assist in the slicing. We will finally describe some research challenges on this topic.

Network slicing has recently been proposed as one of the main enablers for 5G networks. The slicing concept consists of the partition of a physical network into several self-contained logical networks (slices) that can be tailored to offer different functional or performance requirements. In the context of 5G networks, we argue that existing ubiquitous WiFi technology can be exploited to cope with new requirements. Therefore, in this paper, we propose a novel mechanism to implement network slicing in WiFi Access Points. We formulate the resource allocation problem to the different slices as a stochastic optimization problem, where each slice can have bit rate, delay, and capacity requirements. We devise a solution to the problem above using the Lyapunov drift optimization theory, and we develop a novel queuing and scheduling algorithm. We have used Matlab and Simulink to build a prototype of the proposed solution, whose performance has been evaluated in a typical slicing scenario.

Massive scale data centers (MSDC) have become a key component of current content-centric Internet architecture. With scales of up to hundreds of thousands servers, conveying traffic inside these infrastructures requires much greater connectivity resources than traditional broadband Internet transit networks. MSDCs use Fat-Tree type topologies, which ensure multipath connectivity and constant bisection bandwidth between servers. To properly use the potential advantages of these topologies, specific routing protocols are needed, with multipath support and low control messaging load. These infrastructures are enormously expensive, and therefore it is not possible to use them to experiment with new protocols; that is why scalable and realistic emulation/simulation environments are needed. Based on previous experiences, in this paper we present extensions to the ns-3 network simulator that allow executing the Free Range Routing (FRR) protocol suite, which support some of the specific MSDC routing protocols. Focused on the Border Gateway Protocol (BGP), we run a comprehensive set of control plane experiments over Fat-Tree topologies, achieving competitive scalability running on a single-host environment, which demonstrates that the modified ns-3 simulator can be effectively used for experimenting in the MSDC. Moreover, the validation was complemented with a theoretical analysis of BGP behavior over selected scenarios. The whole project is available to the community and fully reproducible.

We propose a method for colorizing photos, this is, providing a color version of a given gray scale image. The method does not depend on human input, and is completely automatic. It does not depend on segmentation, scribbling or sophisticated image processing techniques. It is based on training a simple classifier using back propagation over a training set of color and corresponding gray scale pictures. The classifier predicts the color of a pixel based on the gray level of the pixels surrounding it. This small patch captures a local texture. To keep the domain for the predictor small, the colors are reduced using Self Organizing Maps. This reduction produces a small set of chroma values with enough variation as to generate good approximations for all colors in the training set.

Several countries such as Uruguay and Brazil are implementing the well-known One Laptop Per Child Program (OLPC) by which every child that assists to the primary school obtains in property a laptop with wireless capabilities. They carry their laptops from home to school and back every day and, as seen in the experience, they also carry their laptops to parks, community centers etc. This provides a wide platform for the deployment of Disruption Tolerant network applications. This paper presents a self-managed, opportunistic and content-based routing protocol that supports a network of environmental sensors implemented using consumer-grade wireless routers working together with OLPC laptops. We evaluate the impact of the density, diversity and connectivity of the mobile network on the performance of the protocol and we show how it self-configures it parameters to adapt to changing network conditions.