109 research outputs found
Small-Packet Flows in Software Defined Networks: Traffic Profile Optimization
This paper proposes a method for optimizing bandwidth usage in Software Defined Networks (SDNs) based on OpenFlow. Flows of small packets presenting a high overhead, as the ones generated by emerging services, can be identified by the SDN controller, in order to remove header fields that are common to any packet in the flow, only during their way through the SDN. At the same time, several packets can be multiplexed together in the same frame, thus reducing the overall number of frames. The method can be useful for providing QoS while the packets are traversing the SDN. Four kinds of small-packet traffic flows are considered (VoIP, UDP and TCP-based online games, and ACKs from TCP flows). Both IPv4 and IPv6 are studied, and significant bandwidth savings (up to 68 % for IPv4 and 78 % for IPv6) can be obtained for the considered kinds of traffic. The optimization method is also applied to different public Internet traffic traces, and significant reductions in terms of packets per second are achieved. Results show that bandwidth consumption is also reduced, especially in those traces where the percentage of small packets is high. Regarding the effect on QoS, the additional delay can be kept very low (below 1 millisecond) when the throughput is high, but it may become significant for low- throughput scenarios. Thus, a trade-off between bandwidth saving and additional delay appears in those cases
Optimization of low-efficiency traffic in OpenFlow Software Defined Networks
Abstract — This paper proposes a method for optimizing bandwidth usage in Software Defined Networks (SDNs) based on OpenFlow. Flows of small packets presenting a high overhead, as the ones generated by emerging services, can be identified by the SDN controller, in order to remove header fields that are common to any packet in the flow, only during their way through the SDN. At the same time, several packets can be multiplexed together in the same frame, thus reducing the number of sent frames. Four kinds of small-packet traffic flows are considered (VoIP, UDP and TCP-based online games, and ACKs from TCP flows). Both IPv4 and IPv6 are tested, and significant bandwidth savings (up to 68 % for IPv4 and 78 % for IPv6) can be obtained for the considered kinds of traffic
The Effect of the Buffer Size in QoS for Multimedia and bursty Traffic: When an Upgrade Becomes a Downgrade
This work presents an analysis of the buffer features of an access router, especially the size, the impact on delay and the packet loss rate. In particular, we study how these features can affect the Quality of Service (QoS) of multimedia applications when generating traffic bursts in local networks. First, we show how in a typical SME (Small and Medium Enterprise) network in which several multimedia flows (VoIP, videoconferencing and video surveillance) share access, the upgrade of the bandwidth of the internal network may cause the appearance of a significant amount of packet loss caused by buffer overflow.
Secondly, the study shows that the bursty nature of the traffic in some applications traffic (video surveillance) may impair their QoS and that of other services (VoIP and videoconferencing), especially when a certain number of bursts overlap. Various tests have been developed with the aim of characterizing the problems that may appear when network capacity is increased in these scenarios. In some cases, especially when applications generating bursty traffic are present, increasing the network speed may lead to a deterioration in the quality. It has been found that the cause of this quality degradation is buffer overflow, which depends on the bandwidth relationship between the access and the internal networks. Besides, it has been necessary to describe the packet loss distribution by means of a histogram since, although most of the communications present good QoS results, a few of them have worse outcomes. Finally, in order to complete the study we present the MOS results for VoIP calculated from the delay and packet loss rate
Quality aspects of Internet telephony
Internet telephony has had a tremendous impact on how people communicate.
Many now maintain contact using some form of Internet telephony.
Therefore the motivation for this work has been to address the quality aspects
of real-world Internet telephony for both fixed and wireless telecommunication.
The focus has been on the quality aspects of voice communication,
since poor quality leads often to user dissatisfaction. The scope of the work
has been broad in order to address the main factors within IP-based voice
communication.
The first four chapters of this dissertation constitute the background
material. The first chapter outlines where Internet telephony is deployed
today. It also motivates the topics and techniques used in this research.
The second chapter provides the background on Internet telephony including
signalling, speech coding and voice Internetworking. The third chapter
focuses solely on quality measures for packetised voice systems and finally
the fourth chapter is devoted to the history of voice research.
The appendix of this dissertation constitutes the research contributions.
It includes an examination of the access network, focusing on how calls are
multiplexed in wired and wireless systems. Subsequently in the wireless
case, we consider how to handover calls from 802.11 networks to the cellular
infrastructure. We then consider the Internet backbone where most of our
work is devoted to measurements specifically for Internet telephony. The
applications of these measurements have been estimating telephony arrival
processes, measuring call quality, and quantifying the trend in Internet telephony
quality over several years. We also consider the end systems, since
they are responsible for reconstructing a voice stream given loss and delay
constraints. Finally we estimate voice quality using the ITU proposal PESQ
and the packet loss process.
The main contribution of this work is a systematic examination of Internet
telephony. We describe several methods to enable adaptable solutions
for maintaining consistent voice quality. We have also found that relatively
small technical changes can lead to substantial user quality improvements.
A second contribution of this work is a suite of software tools designed to
ascertain voice quality in IP networks. Some of these tools are in use within
commercial systems today
On the effectiveness of an optimization method for the traffic of TCP-based multiplayer online games
This paper studies the feasibility of using an optimization method, based on multiplexing and header compression, for the traffic of Massively Multiplayer Online Role Playing Games (MMORPGs) using TCP at the Transport Layer. Different scenarios where a number of flows share a common network path are identified. The adaptation of the multiplexing method is explained, and a formula of the savings is devised. The header compression ratio is obtained using real traces of a popular game and a statistical model of its traffic is used to obtain the bandwidth saving as a function of the number of players and the multiplexing period. The obtained savings can be up to 60 % for IPv4 and 70 % for IPv6. A Mean Opinion Score model from the literature is employed to calculate the limits of the multiplexing period that can be used without harming the user experience. The interactions between multiplexed and non-multiplexed flows, sharing a bottleneck with different kinds of background traffic, are studied through simulations. As a result of the tests, some limits for the multiplexing period are recommended: the unfairness between players can be low if the value of the multiplexing period is kept under 10 or 20 ms. TCP background flows using SACK (Selective Acknowledgment) and Reno yield better results, in terms of fairness, than Tahoe and New Reno. When UDP is used for background traffic, high values of the multiplexing period may stress the unfairness between flows if network congestion is severe
Enhancement of perceived quality of service for voice over internet protocol systems
Voice over Internet Protocol (WIP) applications are becoming more and more popular in
the telecommunication market. Packet switched V61P systems have many technical advantages
over conventional Public Switched Telephone Network (PSTN), including its efficient and flexible
use of the bandwidth, lower cost and enhanced security.
However, due to the IP network's "Best Effort" nature, voice quality are not naturally guaranteed
in the VoIP services. In fact, most current Vol]P services can not provide as good a voice
quality as PSTN. IP Network impairments such as packet loss, delay and jitter affect perceived
speech quality as do application layer impairment factors, such as codec rate and audio features.
Current perceived Quality of Service (QoS) methods are mainly designed to be used
in a PSTN/TDM environment and their performance in V6IP environment is unknown. It is a
challenge to measure perceived speech quality correctly in V61P system and to enhance user
perceived speech quality for VoIP system.
The main goal of this project is to evaluate the accuracy of the existing ITU-T speech quality
measurement method (Perceptual Evaluation of Speech Quality - PESQ) in mobile wireless
systems in the context of V61P, and to develop novel and efficient methods to enhance the user
perceived speech quality for emerging V61P services especially in mobile V61P environment.
The main contributions of the thesis are threefold:
(1) A new discovery of PESQ errors in mobile VoIP environment. A detailed investigation
of PESQ performance in mobile VoIP environment was undertaken and included setting up a
PESQ performance evaluation platform and testing over 1800 mobile-to-mobile and mobileto-
PSTN calls over a period of three months. The accuracy issues of PESQ algorithm was
investigated and main problems causing inaccurate PESQ score (improper time-alignment in
the PESQ algorithm) were discovered
.
Calibration issues for a safe and proper PESQ testing
in mobile environment were also discussed in the thesis.
(2) A new, simple-to-use, V611Pjit ter buffer algorithm. This was developed and implemented
in a commercial mobile handset. The algorithm, called "Play Late Algorithm", adaptively alters
the playout delay inside a speech talkspurt without introducing unnecessary extra end-to-end
delay. It can be used as a front-end to conventional static or adaptive jitter buffer algorithms
to provide improved performance. Results show that the proposed algorithm can increase user
perceived quality without consuming too much processing power when tested in live wireless
VbIP networks.
(3) A new QoS enhancement scheme. The new scheme combines the strengths of adaptive
codec bit rate (i. e. AMR 8-modes bit rate) and speech priority marking (i. e. giving high priority
for the beginning of a voiced segment). The results gathered on a simulation and emulation test
platform shows that the combined method provides a better user perceived speech quality than
separate adaptive sender bit rate or packet priority marking methods
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Quality of service optimization of multimedia traffic in mobile networks
Mobile communication systems have continued to evolve beyond the currently deployed Third
Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G
are expected to cater for a wide variety of services such as speech, data, image transmission,
video, as well as multimedia services consisting of a combination of these. With the air interface
being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed
Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of
3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features
such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions
in the base stations, necessitating buffering of data at the air interface which presents a
bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of
Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient
buffer management schemes are required at the air interface.
The main objective of this thesis is to propose and evaluate solutions that will address the
QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the
thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for
multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent
flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the
real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given
transmission priority; while the non-real-time component, being loss sensitive and delay tolerant,
enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session
of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the
Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow
control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia
session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide
efficient network and radio resource utilization to improve end-to-end multimedia traffic
performance. In order to allow real-time optimization of the QoS control between the real-time
and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management
algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP
incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP
is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the
stringent real-time component’s QoS requirements. The thesis presents results of extensive
performance studies undertaken via analytical modelling and dynamic network-level HSDPA
simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP
based buffer management schemes
Energy efficiency in next generation wireless networks: methodologies, solutions and algorithms
Mobile Broadband Wireless Access (BWA) networks will offer in the forthcoming years multiple and differentiated services to users with high mobility requirements, connecting via portable or wearable devices which rely on the use of batteries by necessity. Since such devices consume a relatively large fraction of energy for transmitting/receiving data over-the-air, mechanisms are needed to reduce power consumption, in order to increase the lifetime of devices and hence improve user’s satisfaction. Next generation wireless network standards define power saving functions at the Medium Access Control (MAC) layer, which allow user terminals to switch off the radio transceiver during open traffic sessions for greatest energy consumption reduction. However, enabling power saving usually increases the transmission latency, which can negatively affect the Quality of Service (QoS) experienced by users. On the other hand, imposing
stringent QoS requirements may limit the amount of energy that can be saved.
The IEEE 802.16e standard defines the sleep mode is power saving mechanism with the purpose of reducing energy consumption. Three different operation classes are provided, each one to serve different class of traffic: class I, best effort traffic, class II real time traffic and class III multicast traffic. Several aspects of the sleep mode are left unspecified, as it is usually done in standards, allowing manufacturers to implement their own proprietary solutions, thus gaining a competitive advantage over the rivals.
The work of this thesis is aimed at verifying, the effectiveness of the power saving mechanism proposed into IEEE 802.16e standard, focusing on the mutual interaction between power saving and QoS support. Two types of delay constrained applications with different requirements are considered, i.e., Web and Voice over IP (VoIP). The performance is assessed via detailed packet-level simulation, with respect to several system parameters. To capture the relative contribution of all the factors on the energy- and QoS-related metrics, part of the evaluation is carried out by means of 2k · r! analysis. Our study shows that the sleep mode can achieve significant power consumption reduction, however,
when real time traffic is considered a wise configuration of the parameters is mandatory in order to avoid unacceptable degradation of the QoS.
Finally, based on the guidelines drawn through the analysis, we extend our contribution beyond a simple evaluation, proposing a power saving aware
scheduling framework aimed at reducing further the energy consumption. Our framework integrates with existing scheduling policies that can pursue their original goals, e.g. maximizing throughput or fairness, while improving the energy efficiency of the user terminals. Its effectiveness is assessed through an extensive packet level simulation campaign
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