Improving Third-Party Relaying for LTE-A: A Realistic Simulation Approach

In this article we propose solutions to diverse conflicts that result from the deployment of the (still immature) relay node (RN) technology in LTE-A networks. These conflicts and their possible solutions have been observed by implementing standard-compliant relay functionalities on the Vienna simulator. As an original experimental approach, we model realistic RN operation, taking into account that transmitters are not active all the time due to half-duplex RN operation. We have rearranged existing elements in the simulator in a manner that emulates RN behavior, rather than implementing a standalone brand-new component for the simulator. We also study analytically some of the issues observed in the interaction between the network and the RNs, to draw conclusions beyond simulation observation. The main observations of this paper are that: $i$) Additional time-varying interference management steps are needed, because the LTE-A standard employs a fixed time division between eNB-RN and RN-UE transmissions (typical relay capacity or throughput research models balance them optimally, which is unrealistic nowadays); $ii$) There is a trade-off between the time-division constraints of relaying and multi-user diversity; the stricter the constraints on relay scheduling are, the less flexibility schedulers have to exploit channel variation; and $iii$) Thee standard contains a variety of parameters for relaying configuration, but not all cases of interest are covered.Comment: 17 one-column pages, 9 figures, accepted for publication in IEEE ICC 2014 MW

CFD modeling of a fixed-bed biofilm reactor coupling hydrodynamics and biokinetics

Peer ReviewedPostprint (author's final draft

Youth-culture or student-culture? The internet use intensity divide among university students and the consequences for academic performance

The effects of Internet use on the academic performance of university students is usually analyzed from a deterministic perspective that gives this technology an immanently positive or negative role. In this paper we consider the problem from an alternative point of view. We analyze the actual Internet uses the students engage in and the differences in these according to the students’ characteristics. We aim to explain when spending more time on the Internet has a positive and a negative effect on academic performance and explain why usually a high usage time of internet is correlated with a lower academic achievement

Conicoid Mirrors

The first order equation relating object and image location for a mirror of arbitrary conic-sectional shape is derived. It is also shown that the parabolic reflecting surface is the only one free of aberration and only in the limiting case of distant sources.Comment: 9 page