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Opportunistic Beamforming for Finite Horizon Multicast
Get PDFWireless multicasting suffers from the problem that the transmit rate is usually determined by the receiver with the worst channel. Composite or adaptive beamforming allows using beamforming patterns that trade off antenna gains between receivers. A common solution for wireless multicast with beamforming is to select the pattern that maximizes the minimum rate among all receivers (for a given transmit power). However, when using opportunistic multicast to transmit a finite number of packets to all receivers – the finite horizon problem – this is no longer optimal. Instead, the optimum beamforming pattern depends on instantaneous channel conditions as well as the number of received packets at each receiver. We formulate the finite horizon multicast beamforming problem as a dynamic programming problem to obtain the optimal solution. We further design a heuristic that has sufficiently low complexity to be implementable in practice and show through extensive simulations that our algorithm significantly outperforms prior solutions.TRUEpu
Learning Analytics for the Precise Evaluation of Student Effectiveness with Educational Resources and Activities
Get PDFIn current online courses, most learning analytics techniques collect, analyze and display low-level data about the interactions of students with educational activities and resources. These data are used to detect students with difficulties in the course, as well as educational activities and resources which might be problematic. This paper presents the Precise Effectiveness Strategy (PES) which enables to calculate the effectiveness of students with educational activities and resources in online courses from low-level events in a quantitative way, taking into account different aspects of the learning context. The PES is particularized for specific educational activities and resources, which are video resources and parametric exercises. Finally, we propose some visualizations related to video and exercise effectiveness in a real course in physics.TRUEpu
Understanding the Reachability of IPv6 Limited Visibility Prefixes
Get PDFRIPE Academic Cooperation Initiative (RACI) Scholarship – Travel GrantFALSEpu
Increasing Opportunistic Gain in Small Cells Through Base Station-Driven Traffic Spreading
Get PDFDense deployment of small cells is an important, emerging trend to enable future cellular networks to cope with growing traffic demand. However, this reduces the number of users per cell and thus opportunistic scheduling gain. We propose a base station-driven energy-aware approach to exploit user-user communication to increase the opportunistic gain. We use tools from stochastic Lyapunov optimization to determine the optimal scheduling policy subject to a constraint on energy consumption for user-user communication. Our simulation results show that with a large energy budget, packet transfer delay is reduced by up to 70%. The bulk of the performance improvement can be achieved with only a small increase in energy consumption, where 60% of the improvement is achieved at only 20% of the additional energy consumption. Further, we evaluate our algorithm using realistic video traffic traces and show that frame loss ratio is reduced by 90% and PSNR is improved by 4dB.TRUEpu
ADD-PATH limit capability
No full textNetwork Working Group
Internet-Draft
Expires: August 11, 2014
http://tools.ietf.org/html/draft-francois-idr-addpath-limit-00In this draft, we propose a new capability that allows BGP speakers supporting ADD-PATH to announce a limit on the number of paths they want to receive from their peers.pu
VoIPiggy: Analysis and Implementation of a Mechanism to Boost Capacity in IEEE 802.11 WLANs Carrying VoIP traffic
Get PDFHandling voice traffic in existing WLANs is extremely inefficient, due to the large overhead of the protocol operation as well as the time spent in contention. In this paper, we propose a simple scheme (VoIPiggy) to improve the efficiency of WLANs with voice traffic. The key idea of the mechanism is to piggyback voice frames onto the MAC layer acknowledgments, which reduces both the frame overhead and the time wasted in contention. To quantify the gains of our proposal, we first study its performance by means of a capacity and delay analysis of a WLAN operating under the VoIPiggy mechanism. Then, we present an implementation of the mechanism using commercial off-the-shelf devices, which involves programming at the driver and firmware levels. The performance of the proposed scheme is evaluated in a large-scale testbed consisting on 30 devices. Our extensive measurements, which comprise different network conditions in terms of number of active nodes, traffic load and transmission rates, confirm that the experimental results match the analytical ones, and show a dramatic performance improvement for both "voice only" and "voice and data" scenarios.pu
Modeling Multimode D2D Communications in LTE
Get PDFIn this work we propose a roadmap towards the analytical understanding of Device-to-Device (D2D) communications in LTE-A networks. Various D2D solutions have been proposed, which include inband and outband D2D transmission modes, each of which exhibits different pros and cons in terms of complexity, interference, and spectral efficiency achieved. We go beyond traditional mode optimization and mode-selection schemes. Specifically, we formulate a general problem for the joint per-user mode selection, connection activation and resource scheduling of connections.TRUEpu
Use-cases for Resiliency in SPRING
No full textThis document describes the use cases for resiliency in SPRING networks.pu