IMDEA Networks Institute Digital Repository
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1915 research outputs found
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On the Experimental Assessment of QUIC and Congestion Control Schemes in Cellular Networks
Get PDFWith the growth of the internet, current transport protocols are being re-evaluated to deal with traffic growth. QUIC is an evolving transport-layer protocol that has been developed to reduce Web latency, integrate security features, and enable a high-quality experience for mobile users. However, few systematic experimental studies have been carried out to evaluate users’ service in a realistic mobile environment. In this work, we describe the design of experiments with QUIC and HTTP/3, which is based on QUIC, also considering benchmarks and variants in QUIC’s implementations. We report our measurements collected from real mobile networks with the pan-European MONROE platform. Using data from the application, transport, and network layers in different wireless environments, we experimentally investigate and compare the performance of QUIC and HTTP/3 for static and mobile cellular users of several networks across Europe. Initial results show that QUIC-based operations are advantageous in case of users that move, and they are also strongly affected by the congestion control algorithm chosen for QUIC.TRUEpu
Efficiency of Virtualization over MEC plus Cloud
Get PDFWe study average performance and costs for routing service requests in a virtualized environment, where either the MEC or the Cloud can serve user's requests. Employing a simple yet precise analytical model validated via simulation, we focus on latency, service request losses, energy consumption, and provider utility. The model is very effective in providing insight and guidelines for setting up server selection strategies with different characteristics (e.g., energy consumption, penalties, etc.) and performance requirements. In particular, our results show that the MEC is latency-efficient but incurs higher costs than Cloud, and then, to make its use sustainable, it is desirable that
the MEC server is powered with renewable source energy.TRUEpu
Nuberu: Reliable RAN virtualization in shared platforms
Get PDFRAN virtualization will become a key technology for the last mile of next-generation mobile networks driven by initiatives such as the O-RAN alliance. However, due to the computing fluctuations inherent to wireless dynamics and resource contention in shared computing infrastructure, the price to migrate from dedicated to shared platforms may be too high. Indeed, we show in this paper that the baseline architecture of a base station’s distributed unit (DU) collapses upon moments of deficit in computing capacity. Recent solutions to accelerate some signal processing tasks certainly help but do not tackle the core problem: a DU pipeline that requires predictable computing to provide carrier-grade reliability. We present Nuberu, a novel pipeline architecture for 4G/5G DUs specifically engineered for non-deterministic computing platforms. Our design has one key objective to attain reliability: to guarantee a minimum set of signals that preserve synchronization between the DU and its users during computing capacity shortages and, provided this, maximize network throughput. To this end, we use techniques such as tight deadline control, jitter-absorbing buffers, predictive HARQ, and congestion control. Using an experimental prototype, we show that Nuberu attains >95% of the theoretical spectrum efficiency in hostile environments, where state-of-art approaches lose connectivity, and at least 80% resource savings.TRUEpu
Lights and shadows: A comprehensive survey on cooperative and precoding schemes to overcome LOS blockage and interference in indoor VLC
Get PDFVisible light communications (VLC) have received significant attention as a way of moving
part of the saturated indoor wireless traffic to the wide and unregulated visible optical spectrum.
Nowadays, VLC are considered as a suitable technology, for several applications such as high-
rate data transmission, supporting internet of things communications or positioning. The signal
processing originally derived from radio-frequency (RF) systems such as cooperative or precoding
schemes can be applied to VLC. However, its implementation is not straightforward. Furthermore,
unlike RF transmission, VLC present a predominant line-of-sight link, although a weak non-LoS
component may appear due to the reflection of the light on walls, floor, ceiling and nearby objects.
Blocking effects may compromise the performance of the aforementioned transmission schemes.
There exist several surveys in the literature focused on VLC and its applications, but the management
of the shadowing and interference in VLC requires a comprehensive study. To fill this gap, this
work introduces the implementation of cooperative and precoding schemes to VLC, while remarking
their benefits and drawbacks for overcoming the shadowing effects. After that, the combination of
both cooperative and precoding schemes is analyzed as a way of providing resilient VLC networks.
Finally, we propose several open issues that the cooperative and precoding schemes must face in
order to provide satisfactory VLC performance in indoor scenarios.TRUEpu
Energy-Aware Scheduling Based on Marginal Cost and Task Classification in Heterogeneous Data Centers
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Serving HTC and Critical MTC in a RAN Slice
Get PDFWe consider a slice of a radio access network where human and machine users access services with either high throughput or low latency requirements. The slice offers both eMBB and URLLC service categories to serve HTC (Human- Type Communication) and MTC (Machine-Type Communication) traffic. We propose to use eMBB for both HTC and MTC, transferring machine traffic to URLLC only when eMBB is not able to meet the low latency requirements of MTC. We show that by so doing the slice is capable of providing very good performance to about one hundred MTC users under high HTC traffic conditions. Instead, running time-critical MTC over only eMBB is not doable at all, whereas using URLLC suffices for at most a few tens of devices. Therefore, our approach improves the number of users served by the slice by one order of magnitude, without requiring extra resources or compromising performance. To study system performance we develop a novel analytical model of uplink packet transmissions, which covers both legacy eMBB- or URLLC-based MTC, as well as our compound approach. Our model allows to tune slice parameters so as to achieve the desired balance between HTC and MTC service guarantees. We validate the model against detailed simulations using as an example an autonomous driving scenario.TRUEpu
CloudLSTM: A Recurrent Neural Model for Spatiotemporal Point-cloud Stream Forecasting
Get PDFThis paper introduces CloudLSTM, a new branch of recurrentneural models tailored to forecasting over data streams generated by geospatial point-cloud sources. We design a Dynamic Point-cloud Convolution (DConv) operator as the core component of CloudLSTMs, which performs convolution directly over point-clouds and extracts local spatial features from sets of neighboring points that surround different elements of the input. This operator maintains the permutation invariance of sequence-to-sequence learning frameworks, while representing neighboring correlations at each time step - an important aspect in spatiotemporal predictive learning. The DConv operator resolves the grid-structural data requirements of existing spatiotemporal forecasting models and can be easily plugged into traditional LSTM architectures with sequence-to-sequence learning and attention mechanisms. We apply our proposed architecture to two representative, practical use cases that involve point-cloud streams, i.e., mobile service traffic forecasting and air quality indicator forecasting. Our results,obtained with real-world datasets collected in diverse scenarios for each use case, show that CloudLSTM delivers accurate long-term predictions, outperforming a variety of competitor neural network models.TRUEpu
Minimum Achievable Peak Age of Information Under Service Preemptions and Request Delay
Get PDFThere is a growing interest in analysing freshness of
data in networked systems. Age of Information (AoI) has emerged as a relevant metric to quantify this freshness at a receiver, and minimizing this metric for different system models has received significant research attention. However, a fundamental question remains: what is the minimum achievable AoI in any single-server-single-source queuing system for a given service-time
distribution? We address this question for the average peak AoI (PAoI) statistic by considering generate-at-will source model, service preemptions, and request delays. Our main result is on the characterization of the minimum achievable average PAoI, and we show that it is achieved by a fixed-threshold policy among the set of all causal policies. We use the characterization to provide necessary and sufficient condition for preemptions to be beneficial for a given service-time distribution. Our numerical results, obtained using well-known distributions, demonstrate that the heavier the tail of a distribution the higher the performance gains of using preemptions.pu
Integration of 5G Experimentation Infrastructures into a Multi-Site NFV Ecosystem
Get PDFNetwork Function Virtualization (NFV) has been regarded as one of the key enablers for the 5 th Generation of mobile networks, or 5G. This paradigm allows to reduce the dependence on specialized hardware to deploy telecommunications and vertical services. To this purpose, it relies on virtualization techniques to softwarize network functions, simplifying their development and reducing deployment time and costs. In this context, Universidad Carlos III de Madrid, Telefónica, and IMDEA Networks Institute have developed an NFV ecosystem inside 5TONIC, an open network innovation center focused on 5G technologies, enabling the creation of complex, close to reality experimentation scenarios across a distributed set of NFV infrastructures, which can be made available by stakeholders at different geographic locations. This article presents the protocol that has been defined to incorporate new remote NFV sites into the multi-site NFV ecosystem based on 5TONIC, describing the requirements for both the existing and the newly incorporated infrastructures, their connectivity through an overlay network architecture, and the steps necessary for the inclusion of new sites. The protocol is exemplified through the incorporation of an external site to the 5TONIC NFV ecosystem. Afterwards, the protocol details the verification steps required to validate a successful site integration. These include the deployment of a multi-site vertical service using a remote NFV infrastructure with Small Unmanned Aerial Vehicles (SUAVs). This serves to showcase the potential of the protocol to enable distributed experimentation scenarios.pu