Scientific Posters | workshop 2014

Scientific Posters

Scientific posters authored by PhD Students from IMDEA Networks and their supervisors will be exhibited during the workshop.

Communication architecture of a next generation RPAS: design, deployment and campaigns

Miguel A. Diaz^1&2, Francisco Valera², Ivan Vidal², Marcelo Bagnulo²

¹IMDEA networks Institute, ²Universidad Carlos III de Madrid

Abstract

• Remotely Piloted Aircraft Systems (RPAS) comprise a number of unmanned aircrafts that carry payloads, Ground Control Stations (GCS) that allow the operator to control the system, communication systems to send commands to the planes and supplementary equipment like remote video terminals (RVT).
• Integration of RPAS as part of the network centric warfare is a very important milestone because of the huge amount of data they control.
• This poster presents a recent practical experience deploying an all-IP communications architecture into one of the most relevant Spanish tactical RPAS, the SIVA, property of the INTA.

Increasing Opportunistic Gain in Small Cells Through Base Station-Driven Traffic Spreading

Qing Wang^1&2, Balaji Rengarajan¹, Joerg Widmer¹

¹IMDEA networks Institute, ²Universidad Carlos III de Madrid

Abstract

• Future wireless networks:
- - Dense layouts of small cells
- - Dynamic traffic load
• Problem: Gain from Opportunistic Scheduling is Diminished (the number of “active” users is low)
• Question: Can we find a BS-Driven method to improve User Performance in small-cell networks?

Opportunistic Beamforming for Finite Horizon Multicast

Gek Hong Sim^1&2, Joerg Widmer¹, Balaji Rengarajan¹

¹IMDEA networks Institute, ²Universidad Carlos III de Madrid

Abstract

WIRELESS MULTICASTING & BEAMFORMING:

• Wireless multicast is limited by the receiver with the worst channel.
• Composite multicast beamforming distributes more power towards the weaker receivers' beams and equalizes the SNRs of the receivers.

FINITE HORIZON PROBLEM:

• Objective: Transmit a rateless coded block (consisting of many packets) to all receivers within the least amount of time (minimum completion time).
• Application: Multicast video streaming that requires strict delay constraints and reliable delivery.

The rate maximization algorithm exploits opportunistic gain aggressively thus it causes the weak receivers to lag behind. Note: the rate maximization algorithm is only optimal for the infinite horizon homogeneous scenario.

Reputation-based Machanisms for Evolutionary Master-Worker Computing

Evgenia Christoforou^1,2, Antonio Fernández Anta¹, Chryssis Georgiou³, Miguel A. Mosteiro^4,5, Angel (Anxo) Sánchez^2,6

¹IMDEA Networks Institute, ²Univ. Carlos III de Madrid, ³University of Cyprus, ⁴Kean University, ⁵Universidad Rey Juan Carlos,⁶BIFI Institute

Abstract

We consider Internet-based Master-Worker task computing systems, such as SETI@home, where a master sends tasks to potentially unreliable workers, and the workers execute and report back the result. We model such computations using evolutionary dynamics and consider three type of workers: altruistic, malicious and rational.

Altruistic workers always compute and return the correct result, malicious workers always return an incorrect result, and rational (selfish) workers decide to be truthful or to cheat, based on the strategy that increases their benefit. The goal of the master is to reach eventual correctness, that is, reach a state of the computation that always receives the correct results. To this respect, we propose a mechanism that uses reinforcement learning to induce a correct behavior to rational workers; to cope with malice we employ reputation schemes.

We analyze our reputation-based mechanism modeling it as a Markov chain and we give provable guarantees under which truthful behavior can be ensured. Simulation results, obtained using parameter values that are likely to occur in practice, reveal interesting trade-offs between various metrics, parameters and reputation types, affecting cost, time of convergence to a truthful behavior and tolerance to cheaters.

Modelling D2D Communications in Cellular Access Networks via Coupled Processors

Christian Vitale^1,2, Vincenzo Mancuso^1,2, Gianluca Rizzo³

¹IMDEA Networks Institute,²Universidad Carlos III de Madrid,³HES SO Valais

Abstract

Device-to-Device (D2D) is a raising paradigm for spectrum efficiency in dense cellular networks.

• Performance evaluation of D2D in-band schemes (underlay/overlay) is usually based on simulations or on the conservative assumption that the system is in saturation.

Through worst case analysis, we present the first analytical study of D2D system performances focusing on in-band underlay D2D communication schemes, such as the commercial Qualcomm FlashLinQ™. We derive:

• sufficient conditions for stability, i.e., for guaranteeing bounded delay;
• saturation throughput of cellular transmitters given the demands of the D2D pairs;
• a new method to achieve proportional fairness among D2D transmissions.

MIND THE TIES

Arash Asadi^♯♭, Peter Jacko^§, and Vincenzo Mancuso^♭♯

IMDEA Networks Institute^♯, University Carlos III, Madrid^♭, Lancaster University^§

Abstract

Opportunistic schedulers are known for trading off throughput and fairness of users in cellular networks. We believe that the user fairness can be improved by leveraging the channel correlation between cellular users. We provide the mathematical foundations for the design of a smart tie-breaking mechanism which enhances the fairness achieved by a MaxRate scheduler.

Problem: MaxRate with Maximal fairness.

Solution: We propose a Weighted Round Robin (WRR) tie-breaking method in which the weights α_n, for all n in N , are determined analytically (n = 2) or heuristically (n > 2). We also propose to form D2D clusters among nearby mobile users to increase the probability of tie among users.

Mobile Resource Estimation/Optimization

Nicola Bui¹², Foivos Michelinakis¹², Joerg Widmer¹

¹IMDEA networks Institute, ²Universidad Carlos III de Madrid

Abstract

Mobile network spectrum is becoming everyday a scarcer resource, the importance of efficiently exploiting it is always increasing. Our activity addresses that by focusing on three main topics:

- Lightweight capacity measurement on mobile phones (active and passive)

- Modelling the accuracy of prediction technique for bandwidth availability

- Study the impact of uncertainties on prediction-based resource allocation optimization

Experimental performance evaluation of context-aware application using floating content

Shahzad Ali*†, Gianluca Rizzo‡, Vincenzo Mancuso*†, and Marco Ajmone Marsan*Δ

*IMDEA Networks Institute, Spain; †University Carlos III of Madrid, Spain; ΔPolitecnico di Torino, Italy and ‡HES SO Valais, Switzerland

Abstract

• Context-aware applications make use of a combination of restricted spatio-temporal locality and mobile communications
• Opportunistic communications are a suitable candidate for such applications because they naturally incorporate context
• Floating Content (FC) is a communication service based on opportunistic communications and it aims at ensuring the availability of data within a certain geographic area called Anchor Zone (AZ) for a given duration in time

Deseeding energy consumption of network stacks

Iñaki Ucar¹, Arturo Azcorra¹², Albert Banchs¹²

¹Universidad Carlos III de Madrid, ²IMDEA networks Institute

Abstract

• A recent study unveils that a substantial part of the energy consumption of 802.11 WLAN communication may be ascribed to the frame crossing the OS (i.e., app. to protocol stack to driver to NIC)
• As reported, this energy toll (called cross-factor) may account up to 97% of the total energy consumption per frame in some devices
• This poses doubts on prior works that propose energy efficiency strategies taking into account the network interface card (NIC) only
• The present work is intended to deepen into the roots of the cross-factor, deseed its components, analyze its causes and, finally, propose and design an energy- efficient stack

On The Inter-domain Topology of Africa

Roderick Fanou^1,2, Pierre Francois¹, Emile Aben³

¹IMDEA Networks Institute, ²Universidad Carlos III de Madrid, ³RIPE NCC

Abstract

No knowledge of African ISP transits habits

• A few previous studies for some specific countries

Some knowledge of physical infrastructure 

• Satellite links, submarine cables, fragmented terrestrial optical infrastructures, a few (24) IXPs not well spread in Africa

Perceived QoS is poor

• High latency & low bandwidth

Our goal

• Map the current African Internet topology
• Observe its evolution as more and more local interconnections are  established thanks to initiatives promoting IXPs

You can access last year’s posters here.