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Passive Mobile Bandwidth Classification Using Short Lived TCP Connections
Get PDFConsumption of multimedia content is moving from a residential environment to mobile phones. Optimizing Quality of Experience—smooth, quick, and high quality playback—is more difficult in this setting, due to the highly dynamic nature of wireless links. A key requirement for achieving this goal is estimating the available bandwidth of mobile devices. Ideally, this should be done quickly and with low overhead. One challenge is that the majority of connections on mobiles are short-lived TCP connections, where a significant portion of data exchange is within the slow start phase. In this paper, we propose a novel method that passively estimates the currently available bandwidth by monitoring the minimal traffic generated by such connections. To the best of our knowledge, no other solution can operate with such constrained input. Our estimation method is able to achieve good precision despite artifacts introduced by the slow start behavior of TCP, mobile scheduler and phone hardware. We evaluate our solution against traces collected in 4 European countries. Furthermore, the small footprint of our algorithm allows its deployment on resource limited devices.TRUEpu
Modeling the Impact of Start-Up Times on the Performance of Resource-on-Demand Schemes in 802.11 WLANs
Get PDFResource on Demand in 802.11 Wireless LANs is receiving an increasing attention, with its feasibility already proved in practice and some initial analytical models available. However, while these models have assumed that access points (APs) start up in zero time, experimentation has showed that this is hardly the case. In this work, we provide a new model to account for this time in the simple case of a WLAN formed by two APs where the second AP is switched on/off dynamically to adapt to the traffic load and reduce the overall power consumption, and show that it significantly alters the results when compared to the zero start-up time case, both qualitatively and quantitatively.TRUEpu
A semi-distributed mechanism for Inter-cell Interference Coordination exploiting the ABSF paradigm
Get PDFInter-Cell Interference Coordination (ICIC) has been identified for LTE as the main instrument for interference control. With ICIC, quality requirements can be guaranteed while avoiding the complexity of coordinated baseband processing approaches. However, most ICIC schemes proposed so far rely on centralized multi-cell scheduling algorithms that involve very heavy signaling overhead and, as a result, cannot be used for dense cellular layouts. In this paper, we propose H2(IC)2, a novel ICIC scheme that, in contrast to previous approaches, incurs very low overhead and is practical for dense deployments. H2(IC)2 is based on the Almost Blank SubFrame (ABSF) approach specified by 3GPP, which controls interference by avoiding data transmission in some subframes. Our scheme follows a two-tier approach, consisting of (i) the local schedulers, which perform the scheduling decisions locally and compute ABSF patterns, and (ii) a central coordinator, which supervises ABSF decisions. As a result of such a two-tier design, the scheme requires very light signaling to drive the local schedulers to globally efficient operating points. We analyze the convergence of distributed ABSF/scheduling decisions by using game theoretical tools and show that H2(IC)2 performs fairly close to the benchmark provided by a centralized omniscient scheduler.TRUEpu
Enhancements in spectrum management techniques for heterogeneous 5G future networks
Get PDFIn the last decade, cellular networks are undergoing with a radical change in their basic design foundations. The huge increase in traffic demand requires a novel design of future cellular networks. Driven by this increase, a network densification phenomena is occurring, which in turns requires to devise efficient and reliable mechanisms to deal with the interference problems resulting from such densification. The architecture and mechanisms resulting from such drastic re-design of the network are commonly referred under the term '5G network'.
In this context, this work unveils that current networking solutions are no longer sufficient to (i) provide the required network spectral efficiency, and (ii) guarantee the desired level of quality of experience from the user side. In order to address this problem, in this thesis we propose a novel SDN-like framework that incorporates the needed mechanisms to improve spectral efficiency while delivering the desired quality of experience to users. In particular, our architecture includes the following three contributions: Our first approach addresses the intercell interference issues resulting from high network densification. To this end, we propose novel mechanisms to mitigate the inter-cell interference problem. We address the design of such schemes from two angles: (i) a controller-aided mechanism, which gathers all the information of the network at a centralized point and, based on this information, optimally schedules the transmission from different users, and (ii) a semi-distributed mechanism, which reduces the signaling overhead involved in sending the information to a centralized point while providing close to optimal performance. One of the key novelties of our scheduling algorithms is that they are based on the Almost Blank SubFrame (ABSF) scheme; this scheme has been standardized only recently and very little work has addressed the design of algorithm to use it.
Our second approach addresses spectral efficiency from a complementary angle: cellular traffic offloading for content update applications. This approach leverages high user mobility to offload the cellular downlink traffic through a device-to-device communication. In this context, we propose an adaptive algorithm to optimally transmit content to base stations while maximizing traffic offload. By relying on control theory techniques, our approach delivers near optimally performance.
A third key contribution of this thesis is the design of a solution that combines the above two approaches. In particular, our solution considers that traffic offload is taking place in the network and addresses the design of an optimal scheduling algorithm that leverages on the Almost Blank SubFrame (ABSF) scheme. The combination of these kind of approaches has received little attention from the literature.
The feasibility and performance of the approaches described above are thoroughly evaluated and compared against state-of-the-art solutions through an exhaustive simulation campaign. Our results show that the proposed approach outperforms conventional eICIC techniques as well as standard offloading mechanisms, respectively, and confirm their feasibility in terms of overhead and computational complexity.
To the best of our knowledge, this thesis is the first attempt to design an unified framework which is able to optimally perform offloading for content-update distribution applications while boosting the network performance in terms of spectral efficiency.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
Analysis and implementation of an Infrastructure-on-Demand scheme for 802.11 WLANs
Get PDFResource on Demand in 802.11 Wireless LANs is receiving an increasing attention, with its feasibility already proved in practice and some initial analytical models available. However, while these models assume that access points (APs) start up in zero time, experimentation shows that this is hardly the case. In this work, we provide a new model to account for this time in the case of a WLAN formed by two APs where an AP is switched on/off dynamically to adapt to the traffic load and reduce the overall power consumption, and show that it significantly alters the results when compared to the zero start-up time case. Finally, we propose an algorithm to optimize the energy consumption of the network while guaranteeing a given performance bound and implement a novel management architecture for mobile networks based on OpenFlow, which supports RoD provisioning in a centralised control plane. The feasibility of the approach is demonstrated by a real-life prototype.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
Challenge: Resolving Data Center Power Bill Disputes: The Energy-Performance Trade-offs of Consolidation
Get PDFIn this paper we challenge the common evaluation practices
used in Virtual Machine (VM) consolidation, such as simulation and small testbeds, which fail to capture the fundamental trade-off between energy consumption and performance. We identify a number of over-simplifying assumptions which are typically made about the energy consumption and performance characteristics of modern networked systems. In response, we describe how more accurate models for data-center systems can be designed and used in order to create an evaluation framework that allows the exploration of the energy-performance trade-off in VM consolidation strategies with enhanced fidelity.TRUEpu
Precise Effectiveness Strategy for analyzing the effectiveness of students with educational resources and activities in MOOCs
Get PDFPresent MOOC and SPOC platforms do not provide teachers with precise metrics that represent the effectiveness of students with educational resources and activities. This work proposes and illustrates the application of the Precise Effectiveness Strategy (PES). PES is a generic methodology for defining precise metrics that enable calculation of the effectiveness of students when interacting with educational resources and activities in MOOCs and SPOCs, taking into account the particular aspects of the learning context. PES has been applied in a case study, calculating the effectiveness of students when watching video lectures and solving parametric exercises in four SPOCs deployed in the Khan Academy platform. Different visualizations within and between courses are presented combining the metrics defined following PES. We show how these visualizations can help teachers make quick and informed decisions in our case study, enabling the whole comparison of a large number of students at a glance, and a quick comparison of the four SPOCs divided by videos and exercises. Also, the metrics can help teachers know the relationship of effectiveness with different behavioral patterns. Results from using PES in the case study revealed that the effectiveness metrics proposed had a moderate negative correlation with some behavioral patterns like recommendation listener or video avoider.pu
Modeling the Throughput of 1-persistent CSMA in Underwater Networks
Get PDFThe aim of this paper is to present a model for the throughput of the 1-persistent CSMA protocol in underwater networks, where the typically large propagation delay with respect to the packet transmission time requires to take into account the spatial distribution of the nodes. Our model is developed based on the analysis carried out in [1] for the non-persistent CSMA protocol. Our results show that the 1-persistent CSMA model developed by Tobagi and Kleinrock is still valid as an approximation, with a few small adjustments, even though it considers an equal propagation delay for all pairs of nodes in the network. The proposed model is validated against simulation results based on the network simulator OMNeT++.TRUEpu
Routes and Interconnectivity: An Internet Trend and an Architectural Proposal
No full textThe Internet is a diverse ecosystem where a multitude of networks interconnect to provide end users with a global reach. Interconnection agreements supply economic incentives for networks to deliver traffic along end-to-end paths. Driven by the rapid Internet adoption, unrelenting traffic growth, and increasing demands for performance and quality, Internet interconnections evolve and affect traffic routing.
In this seminar, we first explore an emerging phenomenon of remote peering, an interconnection where remote networks peer via a layer-2 provider. While our measurements reveal significant presence of remote peering at IXPs (Internet eXchange Points) worldwide and a substantial potential to offload transit traffic, we also discuss implications of remote peering for Internet topology modeling. Then, we propose Route Bazaar, a new architecture for flexible Internet connectivity. Inspired by cryptocurrencies, the use of a block chain in Route Bazaar enables multilateral contracts for end-to-end routing with QoS (Quality of Service), rich private policies, and public accountability.TRUEpu