| 1. |
- Chavez, Karina, et al.
(författare)
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The Evolutionary Role of Communication Technologies in Public Safety Networks
- 2015. - 1
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Ingår i: Wireless Public Safety Networks 1: Overview and Challenges. - : Elsevier. - 9781785480225 ; , s. 21-48
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Existing networks for public safety communications are mostly based on systems such as terrestrial trunked radio (TETRA), TETRAPOL and Project 25. These systems are mainly designed to support voice services. However, public safety communication networks are challenged to expand their scope way beyond their original functions toward more sophisticated devices and support new services including packet data communications. Therefore, governments, public safety agencies and research communities are continuously working together and are making significant progresses toward improving public safety communications capabilities. Next-generation mobile technologies are the enablers for meeting the new requirements of the public safety community. Public safety and commercial systems are typically designed and deployed to fulfill different needs and have different requirements, which are directly affecting the quality of service of the communications. The unique and vital nature of public safety affects the technical decisions that are necessary to guarantee connectivity for everyone, anywhere and anytime. For this reason, recent enhancements of the 4G long term evolution (LTE) in the field of public safety communications, such as device-to-device and group communications for mobiles in physical proximity, accrue a great opportunity to bring new services and a high-level of technological innovation to the public safety workers or first responders. We describe and analyze the evolution of public safety communication systems from the technical standpoint providing a complete overview of what is available in the market and a glimpse of future trends. Furthermore, we discuss the challenges to efficiently deploy, operate and interoperate present and future technologies for public safety communication networks and describe how these technologies can help public safety agencies to meet their expectations.
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| 2. |
- Gomez, Karina, et al.
(författare)
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Measurement-based modelling of power consumption at wireless access network gateways
- 2012
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Ingår i: Computer Networks. - : Elsevier. - 1389-1286 .- 1872-7069. ; 56:10, s. 2506-2521
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Tidskriftsartikel (refereegranskat)abstract
- Improving the energy efficiency of the ICT sector is becoming an ambitious challenge for industries and research communities alike. Understanding how the energy is consumed in each part of an ICT system becomes fundamental in order to minimize the overall energy consumed by the system itself. In this paper, we propose an experimentally-driven approach to (i) characterize typical wireless access network gateways from an energy consumption standpoint and (ii) develop simple and accurate power consumption models for such gateways. In this work we focused our attention on the monitoring, measurement and analysis of the energy consumption patterns of WiFi and WiMAX gateways. Our measurements show that the power consumption of such gateways exhibits a linear dependence on the traffic until a saturation point is reached.
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| 3. |
- Oljira, Dejene Boru, et al.
(författare)
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A Model for QoS-Aware VNF Placement and Provisioning
- 2017
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Ingår i: Network Function Virtualization and Software Defined Networks (NFV-SDN), 2017 IEEE Conference on. - : IEEE. - 9781538632857 - 9781538632864
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Konferensbidrag (refereegranskat)abstract
- Network Function Virtualization (NFV) is a promising solution for telecom operators and service providers to improve business agility, by enabling a fast deployment of new services, and by making it possible for them to cope with the increasing traffic volume and service demand. NFV enables virtualization of network functions that can be deployed as virtual machines on general purpose server hardware in cloud environments, effectively reducing deployment and operational costs. To benefit from the advantages of NFV, virtual network functions (VNFs) need to be provisioned with sufficient resources and perform without impacting network quality of service (QoS). To this end, this paper proposes a model for VNFs placement and provisioning optimization while guaranteeing the latency requirements of the service chains. Our goal is to optimize resource utilization in order to reduce cost satisfying the QoS such as end- to-end latency. We extend a related VNFs placement optimization with a fine-grained latency model including virtualization overhead. The model is evaluated with a simulated network and it provides placement solutions ensuring the required QoS guarantees.
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| 4. |
- Oljira, Dejene Boru, et al.
(författare)
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Analysis of Network Latency in Virtualized Environments
- 2016
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Ingår i: Global Communications Conference (GLOBECOM), 2016 IEEE. - : IEEE. - 9781509013289
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Konferensbidrag (refereegranskat)abstract
- Virtualization is central to cloud computing systems. It abstracts computing resources to be shared among multiple virtual machines (VMs) that can be easily managed to run multiple applications and services. To benefit from the advantages of cloud computing, and to cope with increasing traffic demands, telecom operators have adopted cloud computing. Telecom services and applications are, however, characterized by real-time responsiveness, strict end-to-end latency, and high reliability. Due to the inherent overhead of virtualization, the network performance of applications and services can be degraded. To improve the performance of emerging applications and services that demand stringent end-to-end latency, and to understand the network performance bottleneck of virtualization, a comprehensive performance measurement and analysis is required. To this end, we conducted controlled and detailed experiments to understand the impact of virtualization on end-to-end latency and the performance of transport protocols in a virtualized environment. We also provide a packet delay breakdown in the virtualization layer which helps in the optimization of hypervisor components. Our experimental results indicate that the end-to-end latency and packet delay in the virtualization layer are increased with co-located VMs.
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| 5. |
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| 6. |
- Oljira, Dejene Boru, et al.
(författare)
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Energy-Efficient Data Replication in Cloud Computing Datacenters
- 2013
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Ingår i: 2013 IEEE GLOBECOM WORKSHOPS (GC WKSHPS). - : IEEE. - 9781479928514 ; , s. 446-451
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Konferensbidrag (refereegranskat)abstract
- Cloud computing is an emerging paradigm that provides computing resources as a service over a network. Communication resources often become a bottleneck in service provisioning for many cloud applications. Therefore, data replication, which brings data (e.g., databases) closer to data consumers (e.g., cloud applications), is seen as a promising solution. It allows minimizing network delays and bandwidth usage. In this paper we study data replication in cloud computing data centers. Unlike other approaches available in the literature, we consider both energy efficiency and bandwidth consumption of the system, in addition to the improved Quality of Service (QoS) as a result of the reduced communication delays. The evaluation results obtained during extensive simulations help to unveil performance and energy efficiency tradeoffs and guide the design of future data replication solutions.
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| 7. |
- Oljira, Dejene Boru
(författare)
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Low Latency Communication in Virtualized and Multipath Networks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand from customers for high-quality and customized network services has increased. Telecom service providers have adopted a Network Functions Virtualization (NFV) based service delivery model, in response to the unprecedented traffic growth and increasing customer demand. However, in virtualized systems, achieving carrier-grade network performance such as low latency to guarantee the quality of experience (QoE) of customers is challenging. Moreover, queuing delays that may occur both in the datacenter networks and the IP network infrastructure inhibit the deployment of emerging low-latency services.In this thesis, we focus on addressing the problem of network latency. We study the delay overhead of virtualization by comprehensive network performance measurements and analysis, in a controlled virtualized environment. The study of virtualization delay provides a break-down of the latency imposed by the virtualization and the impact of the consolidation of virtualized applications of different workloads on the end-to-end latency. On the basis of our study, we developed an optimization model for the placement and provisioning of virtualized telecom applications subject to both the latency and cost-efficiency requirements.To mitigate network latency that results from queuing delays as well as to improve multipath network capacity utilization of a datacenter network, we propose a multipath congestion control, Multipath Datacenter TCP (MDTCP), that leverages Explicit Congestion Notification (ECN) to detect and react to queuing delays caused by incipient congestion. Furthermore, we extend MDTCP with the Low Latency Low Loss and Scalable Throughput (L4S) Internet service architecture support so that it can also be used in the Internet. This ensures the low-latency demand of delay-sensitive applications and improves QoE of Internet users by exploiting the multi-access or multi-connectivity technologies of user devices.
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| 8. |
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| 9. |
- Oljira, Dejene Boru, et al.
(författare)
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MDTCP: Practical Latency-Aware Multipath Con- gestion Control for Datacenter Networks
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Datacenter applications generate a mix of short and long flows, which have often contrasting network performance requirements. While short flows are typically sensitive to their completion time, long flows are more or less deadline agnostic but demand high throughput. Despite the availability of multiple, parallel high-capacity paths inside a datacenter network, the achievable transport-layer performance for both latency-sensitive and capacity-demanding applications is far from optimal. The reason is partly due to the inefficiency of transport protocols deployed inside datacenters. Existing transport protocols are either not capable of utilizing multiple paths offered by datacenter topologies, e.g., Datacenter TCP (DCTCP) or unsuitable for latency-sensitive applications, e.g., Multipath TCP (MPTCP), due to the employed congestion detection schemes. To address this problem, we have designed a coupled multipath congestion control algorithm called Multipath Datacenter TCP (MDTCP). MDTCP builds upon MPTCP and uses Explicit Congestion Notification (ECN) signals to detect and react to congestion before queues overflow as in DCTCP, offering both reduced latency and higher network utilization. The MDTCP congestion control has been implemented in the Linux kernel and in a packet- level network simulator. We evaluate MDTCP’s performance extensively both in a programmable datacenter network testbed andin large-scale simulations. The obtained results show that MDTCP outperforms DCTCP by reducing the average Flow Completion Time (FCT) by more than 1.6× at high load, and achieves similar performance as DCTCP at moderate network load. Moreover, it outperforms MPTCP by always achieving a lower average FCT. MDTCP also improves network utilization by 7% and 12% compared to MPTCP and DCTCP, respectively.
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