| 1. |
- AT, Andersen, et al.
(författare)
-
A partially-blocking queueing system with CBR/VBR and ABR/UBR arrival streams
- 2002
-
Ingår i: Telecommunications Systems. - : Baltzer Academic Publisher. - 1018-4864 .- 1572-9451. ; 19:1, s. 75-99
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we consider an ATM transmission link., to which CBR or VBR and ABR or UBR calls arrive according to independent Poisson processes. CBR/VBR calls (characterized by their equivalent bandwidth) are blocked and leave the system if the available link capacity is less than required at the time of arrival. ABR/UBR calls, however, accept partial blocking, meaning that they may enter service even if the available capacity is less than the specified required peak bandwidth, but greater than the so called minimal accepted bandwidth. Partially blocked ABR/UBR calls instead experience longer service time, since smaller given bandwidth entails proportionally longer time spent in the system, as first suggested in [3] and analyzed in details herein. Throughout the life time of an ABR/UBR connection, its bandwidth consumption fluctuates in accordance with the current load on the link but always at the highest possible value up to their peak bandwidth (greedy sources). Additionally, if this minimal accepted bandwidth is unavailable at the time of arrival, ABR/UBR calls are allowed to wait in a finite queue. This system is modeled by a Continuous Time Markov Chain (CTMC) and the CBR/VBR and ABR/UBR blocking probabilities and the mean ABR/UBR waiting- and service times are derived.
|
|
| 2. |
- Brostrom, Peter, et al.
(författare)
-
Design of OSPF networks using subpath consistent routing patterns
- 2009
-
Ingår i: TELECOMMUNICATION SYSTEMS. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 41:4, s. 293-309
-
Tidskriftsartikel (refereegranskat)abstract
- We address the problem of designing IP networks where the traffic is routed using the OSPF protocol. Routers in OSPF networks use link weights set by an administrator for determining how to route the traffic. The routers use all shortest paths when traffic is routed to a destination, and the traffic is evenly balanced by the routers when several paths are equally short. We present a new model for the OSPF network design problem. The model is based on routing patterns and does not explicitly include OSPF weights. The OSPF protocol is modeled by ensuring that all pairs of routing patterns are subpath consistent, which is a necessary condition for the existence of weights. A Lagrangean heuristic is proposed as solution method, and feasible solutions to the problem are generated using a tabu search method. Computational results are reported for random instances and for real-life instances.
|
|
| 3. |
- Chen, Lei, 1981-, et al.
(författare)
-
Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover
- 2012
-
Ingår i: Telecommunications Systems. - : Springer. - 1018-4864 .- 1572-9451. ; 51:1, s. 53-64
-
Tidskriftsartikel (refereegranskat)abstract
- Coverage planning is an important engineering task in deploying UMTSnetworks implementing both high speed downlink packet access (HSDPA)and Release 99 (R99) services. Coverage planning amounts todetermining the cell coverage pattern by means of setting the commonpilot channel (CPICH) power of the cells. A conventional strategy isto uniformly allocate a proportion of the total power to CPICH. Inthis paper, we develop mathematical modeling and optimizationapproaches to bring the benefit of power saving enabled by optimizingnon-uniform CPICH to enhance HSDPA performance, while preserving adesired degree of soft handover (SHO) for R99. The studyfocuses on HSDPA performance at cell edges, where data throughput istypically low. An integer linear programming model is developed forthe resulting optimization problem. The model admits optimal ornear-optimal planning solutions for relatively small networks.Solution algorithms based on local search and repeated localsearch are developed. These algorithms are able to perform theoptimization for large-scale networks time-efficiently. Experimentalresults for both synthesized networks as well as instances originatingfrom real planning scenarios demonstrate the benefit of ouroptimization approach.
|
|
| 4. |
- Ciszkowski, Tomasz, et al.
(författare)
-
Towards Quality of Experience-based reputation models for future web service provisioning
- 2012
-
Ingår i: Telecommunications Systems. - : Springer. - 1018-4864 .- 1572-9451. ; 51:4, s. 283-295
-
Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of Future Internet. Parameters being under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users’ satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users’ opinions. The goal of this paper it to present a novel framework of web services where a reputation system is incorporated for users satisfaction tracking and prediction. This approach is a beneficial tool, which enables providers to facilitate service adaptation according to users’ expectations and maintain QoE on a satisfying level. Presented reputation system operates in an environment of composite services running on a client and server side. It makes this approach highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles even the service and network resources are shared.
|
|
| 5. |
- Dán, György, et al.
(författare)
-
On the effects of the packet size distribution on the packet loss process
- 2006
-
Ingår i: Telecommunications Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 32:1, s. 31-53
-
Tidskriftsartikel (refereegranskat)abstract
- Real-time multimedia applications have to use forward error correction (FEC) anderror concealment techniques to cope with losses in today's best-effort Internet. The efficiency of these solutions is known however to depend on the correlation between losses in the media stream. In this paper we investigate how the packet size distribution affects the packet loss process, that is, the distribution of the number of lost packets in a block, the related FEC performance and the average loss run length. We present mathematical models for the loss process of the MMPP+M/D/1/K and the MMPP+M/M/1/K queues; we validate the models via simulations, and compare the results to simulation results with an MPEG-4 coded video trace. We conclude that the deterministic packet size distribution (PSD) not only results in lower stationary loss probability than the exponential one, but also gives a less correlated loss process, both at a particular average link load and at a particular stationary loss probability as seen by the media stream.Our results show that for applications that can only measure the packet loss probability, the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior. Our results show that the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior and thus can improve the queuing performance by decreasing the variance of its PSD.
|
|
| 6. |
- De Andrade, Marilet, et al.
(författare)
-
Enhanced IPACT : solving the over-granting problem in long-reach EPON
- 2013
-
Ingår i: Telecommunications Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 54:2, s. 137-146
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we address an issue referred to as "over-granting problem", which is inherent in the existing dynamic bandwidth allocation algorithms for Ethernet-based Passive Optical Networks (EPON), in particular when deployed for multi-threaded scheme in long-reach scenario. In order to solve this problem we design a scheme for the algorithm of Interleaved Polling with Adapted Cycle Time (IPACT) with the limited service discipline. We evaluate the proposed scheme through simulations for single-thread and double-thread cases and demonstrate that, the network performance can be significantly improved by our solution in terms of average delay, jitter, and throughput.
|
|
| 7. |
- Erman, David, et al.
(författare)
-
Validating BitTorrent Models
- 2008
-
Ingår i: Telecommunications Systems. - : Springer. - 1018-4864 .- 1572-9451. ; 39:2, s. 103-116
-
Tidskriftsartikel (refereegranskat)abstract
- BitTorrent (bt), a Peer-to-Peer (p2p) distribution system, is a major bandwidth consumer in the current Internet. This paper reports on a measurement study of bt traffic intended to identify potential traffic invariants. To this end, we employ high-accuracy packet capture hardware together with specialized parsing software. Important characteristics regarding bt sessions and messages as well as general system characteristics are reported. The results indicate that characteristics such as session inter-arrival times are corroborated to be exponentially distributed, while other characteristics are shown to differ from previously reported results. These differences are attributed to changes in the core bt algorithms. Further, it is observed that long- and heavy-tailed distributions can be used to model several characteristics. The log-normal, Pareto and mixtures of these distributions are used to model session sizes and durations, while the Weibull distribution has been observed to model message inter-arrival and inter-departure times for bandwidth-limited clients.
|
|
| 8. |
- Fitzgerald, Emma, et al.
(författare)
-
An analytic model for Throughput Optimal Distributed Coordination Function (TO-DCF)
- 2017
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 66:2, s. 197-215
-
Tidskriftsartikel (refereegranskat)abstract
- TO-DCF, a new backoff scheme for 802.11, has the potential to significantly increase throughput in dense wireless LANs while also opportunistically favouring nodes with heavier traffic loads and/or better channel conditions. In this paper we present an analytical model to investigate the behaviour and performance of the TO-DCF protocol with regards to operating parameters such as the number of nodes, the contention window size and the backoff countdown probabilities. We then compare numerical results from an implementation of our model with simulations. Our model shows a high level of accuracy, even when the model assumptions are relaxed, and provides guidance for network operators to correctly configure the weight functions for nodes running TO-DCF given the network’s operating conditions.
|
|
| 9. |
- Franco, Antonio, et al.
(författare)
-
Statistical guarantee of timeliness in networks of IoT devices
- 2022
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451.
-
Tidskriftsartikel (refereegranskat)abstract
- The Internet of Things (IoT) paradigm, has opened up the possibility of using the ubiquity of small devices to route information without the necessity of being connected to a Wide Area Network (WAN). Use cases of IoT devices sending updates that are routed and delivered by other IoT devices have been proposed in the literature. In this paper we focus on receivers only interested in the freshest updates from the sending device. In particular, the dynamic network created by routing/gossiping through small devices creates the possibility of delivering updates out of order. Thus, the entire process can be studied well through a queueing system with infinitely many servers, all serving updates with a random service time. Age of Information (AoI) was proposed as the main metric to measure information freshness. We study the amount of time that the AoI is over a certain threshold at the receiver end as a Quality of Service (QoS) measure, called update outage probability. Particularly, given the recent interest in the literature for time domain analysis of the AoI, we obtain the exact expressions for the AoI, peak AoI (pAoI), effective service time and effective departure time distributions for an M/M/∞ queuing system from a time domain perspective, and study the interdependence between the various parameters involved in order to satisfy a given statistical constraint on timeliness.
|
|
| 10. |
- Galbally, Javier, et al.
(författare)
-
Evaluation of Direct Attacks to Fingerprint Verification Systems
- 2011
-
Ingår i: Telecommunications Systems. - New York : Springer-Verlag New York. - 1018-4864 .- 1572-9451. ; 47:3, s. 243-254
-
Tidskriftsartikel (refereegranskat)abstract
- The vulnerabilities of fingerprint-based recognition systems to direct attacks with and without the cooperation of the user are studied. Two different systems, one minutiae-based and one ridge feature-based, are evaluated on a database of real and fake fingerprints. Based on the fingerprint images quality and on the results achieved on different operational scenarios, we obtain a number of statistically significant observations regarding the robustness of the systems. © 2010 Springer Science+Business Media, LLC.
|
|
