911 research outputs found
A novel non-intrusive objective method to predict voice quality of service in LTE networks.
This research aimed to introduce a novel approach for non-intrusive objective
measurement of voice Quality of Service (QoS) in LTE networks. While achieving this aim, the thesis established a thorough knowledge of how voice traffic is
handled in LTE networks, the LTE network architecture and its similarities and
differences to its predecessors and traditional ground IP networks and most
importantly those QoS affecting parameters which are exclusive to LTE environments. Mean Opinion Score (MOS) is the scoring system used to measure
the QoS of voice traffic which can be measured subjectively (as originally intended). Subjective QoS measurement methods are costly and time-consuming,
therefore, objective methods such as Perceptual Evaluation of Speech Quality
(PESQ) were developed to address these limitations. These objective methods
have a high correlation with subjective MOS scores. However, they either require individual calculation of many network parameters or have an intrusive
nature that requires access to both the reference signal and the degraded signal
for comparison by software. Therefore, the current objective methods are not
suitable for application in real-time measurement and prediction scenarios.
A major contribution of the research was identifying LTE-specific QoS affecting parameters. There is no previous work that combines these parameters to
assess their impacts on QoS.
The experiment was configured in a hardware in the loop environment. This
configuration could serve as a platform for future research which requires simulation of voice traffic in LTE environments.
The key contribution of this research is a novel non-intrusive objective method
for QoS measurement and prediction using neural networks. A comparative
analysis is presented that examines the performance of four neural network
algorithms for non-intrusive measurement and prediction of voice quality over
LTE networks. In conclusion, the Bayesian Regularization algorithm with 4 neurons in the hidden layer and sigmoid symmetric transfer function was identified as the best solution with a Mean Square Error (MSE) rate of 0.001 and
regression value of 0.998 measured for the testing data set
Quality of Service Controlled Multimedia Transport Protocol
PhDThis research looks at the design of an open transport protocol that supports a range of
services including multimedia over low data-rate networks. Low data-rate multimedia
applications require a system that provides quality of service (QoS) assurance and flexibility.
One promising field is the area of content-based coding. Content-based systems use an array
of protocols to select the optimum set of coding algorithms. A content-based transport
protocol integrates a content-based application to a transmission network.
General transport protocols form a bottleneck in low data-rate multimedia
communicationbsy limiting throughpuot r by not maintainingt iming requirementsT. his work
presents an original model of a transport protocol that eliminates the bottleneck by
introducing a flexible yet efficient algorithm that uses an open approach to flexibility and
holistic architectureto promoteQ oS.T he flexibility andt ransparenccyo mesi n the form of a
fixed syntaxt hat providesa seto f transportp rotocols emanticsT. he mediaQ oSi s maintained
by defining a generic descriptor. Overall, the structure of the protocol is based on a single
adaptablea lgorithm that supportsa pplication independencen, etwork independencea nd
quality of service.
The transportp rotocol was evaluatedth rougha set of assessmentos:f f-line; off-line
for a specific application; and on-line for a specific application. Application contexts used
MPEG-4 test material where the on-line assessmenuts eda modified MPEG-4 pl; yer. The
performanceo f the QoSc ontrolledt ransportp rotocoli s often bettert hano thers chemews hen
appropriateQ oS controlledm anagemenatl gorithmsa re selectedT. his is shownf irst for an
off-line assessmenwt here the performancei s compared between the QoS controlled
multiplexer,a n emulatedM PEG-4F lexMux multiplexers chemea, ndt he targetr equirements.
The performanceis also shownt o be better in a real environmentw hen the QoS controlled
multiplexeri s comparedw ith the real MPEG-4F lexMux scheme
Mobile Ad-Hoc Networks
Ad-hoc networks are a key in the evolution of wireless networks. Ad-hoc networks are typically composed of equal nodes, which communicate over wireless links without any central control. Ad-hoc wireless networks inherit the traditional problems of wireless and mobile communications, such as bandwidth optimisation, power control and transmission quality enhancement. In addition, the multi-hop nature and the lack of fixed infrastructure brings new research problems such as configuration advertising, discovery and maintenance, as well as ad-hoc addressing and self-routing. Many different approaches and protocols have been proposed and there are even multiple standardization efforts within the Internet Engineering Task Force, as well as academic and industrial projects. This chapter focuses on the state of the art in mobile ad-hoc networks. It highlights some of the emerging technologies, protocols, and approaches (at different layers) for realizing network services for users on the move in areas with possibly no pre-existing communications infrastructure
EVEREST IST - 2002 - 00185 : D23 : final report
Deliverable públic del projecte europeu EVERESTThis deliverable constitutes the final report of the project IST-2002-001858 EVEREST. After its successful completion, the project presents this document that firstly summarizes the context, goal and the approach objective of the project. Then it presents a concise summary of the major goals and results, as well as highlights the most valuable lessons derived form the project work. A list of deliverables and publications is included in the annex.Postprint (published version
IMPROVING QoS OF VoWLAN VIA CROSS-LAYER BASED ADAPTIVE APPROACH
Voice over Internet Protocol (VoIP) is a technology that allows the transmission of
voice packets over Internet Protocol (IP). Recently, the integration of VoIP and
Wireless Local Area Network (WLAN), and known as Voice over WLAN
(VoWLAN), has become popular driven by the mobility requirements ofusers, as
well as by factor of its tangible cost effectiveness. However, WLAN network
architecture was primarily designed to support the transmission of data, and not for
voice traffic, which makes it lack ofproviding the stringent Quality ofService (QoS)
for VoIP applications. On the other hand, WLAN operates based on IEEE 802.11
standards that support Link Adaptive (LA) technique. However, LA leads to having a
network with multi-rate transmissions that causes network bandwidth variation, which
hence degrades the voice quality. Therefore, it is important to develop an algorithm
that would be able to overcome the negative effect of the multi-rate issue on VoIP
quality. Hence, the main goal ofthis research work is to develop an agent that utilizes
IP protocols by applying a Cross-Layering approach to eliminate the above-mentioned
negative effect. This could be expected from the interaction between Medium Access
Control (MAC) layer and Application layer, where the proposed agent adapts the
voice packet size at the Application layer according to the change of MAC
transmission data rate to avoid network congestion from happening. The agent also
monitors the quality of conversations from the periodically generated Real Time
Control Protocol (RTCP) reports. If voice quality degradation is detected, then the
agent performs further rate adaptation to improve the quality. The agent performance
has been evaluated by carrying out an extensive series ofsimulation using OPNET
Modeler. The obtained results of different performance parameters are presented,
comparing the performance ofVoWLAN that used the proposed agent to that ofthe
standard network without agent. The results ofall measured quality parameters hav
Modelling the IEEE 802.11 wireless MAC layer under heterogeneous VoIP traffic to evaluate and dimension QoE
PhDAs computers become more popular in the home and workplace, sharing resources and
Internet access locally is a necessity. The simplest method of choice is by deploying a
Wireless Local Area Network; they are inexpensive, easy to configure and require
minimal infrastructure. The wireless local area network of choice is the IEEE 802.11
standard; IEEE 802.11, however, is now being implemented on larger scales outside of
the original scope of usage. The realistic usage spans from small scale home solutions to
commercial ‘hot spots,’ providing access within medium size areas such as cafés, and
more recently blanket coverage in metropolitan. Due to increasing Internet availability
and faster network access, in both wireless and wired, the concept of using such
networks for real-time services such as internet telephony is also becoming popular.
IEEE 802.11 wireless access is shared with many clients on a single channel and there are
three non-overlapping channels available. As more stations communicate on a single
channel there is increased contention resulting in longer delays due to the backoff
overhead of the IEEE 802.11 protocol and hence loss and delay variation; not desirable
for time critical traffic.
Simulation of such networks demands super-computing resource, particularly where
there are over a dozen clients on a given. Fortunately, the author has access to the UK’s
super computers and therefore a clear motivation to develop a state of the art analytical
model with the required resources to validate. The goal was to develop an analytical
model to deal with realistic IEEE 802.11 deployments and derive results without the
need for super computers.
A network analytical model is derived to model the characteristics of the IEEE 802.11
protocol from a given scenario, including the number of clients and the traffic load of
each. The model is augmented from an existing published saturated case, where each
client is assumed to always have traffic to transmit. The nature of the analytical model is
to allow stations to have a variable load, which is achieved by modifying the existing
models and then to allow stations to operate with different traffic profiles. The different
traffic profiles, for each station, is achieved by using the augmented model state machine
per station and distributing the probabilities to each station’s state machine accordingly.
To address the gap between the analytical models medium access delay and standard
network metrics which include the effects of buffering traffic, a queueing model is
identified and augmented which transforms the medium access delay into standard
network metrics; delay, loss and jitter. A Quality of Experience framework, for both
computational and analytical results, is investigated to allow the results to be represented
as user perception scores and the acceptable voice call carrying capacity found. To find
the acceptable call carrying capacity, the ITU-T G.107 E-Model is employed which can
be used to give each client a perception rating in terms of user satisfaction.
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QUEEN MARY, UNIVERSITY OF LONDON OLIVER SHEPHERD
With the use of a novel framework, benchmarking results show that there is potential to
maximise the number of calls carried by the network with an acceptable user perception
rating. Dimensioning of the network is undertaken, again compared with simulation
from the super computers, to highlight the usefulness of the analytical model and
framework and provides recommendations for network configurations, particularly for
the latest Wireless Multimedia extensions available in IEEE 802.11.
Dimensioning shows an overall increase of acceptable capacity of 43%; from 7 to 10 bidirectional
calls per Access Point by using a tuned transmission opportunity to allow
each station to send 4 packets per transmission. It is found that, although the accuracy
of the results from the analytical model is not precise, the model achieves a 1 in 13,000
speed up compared to simulation. Results show that the point of maximum calls comes
close to simulation with the analytical model and framework and can be used as a guide
to configure the network. Alternatively, for specific capacity figures, the model can be
used to home-in on the optimal region for further experiments and therefore achievable
with standard computational resource, i.e. desktop machines
Contribution to resource management in cellular access networks with limited backhaul capacity
La interfaz radio de los sistemas de comunicaciones móviles es normalmente considerada como
la única limitación de capacidad en la red de acceso radio. Sin embargo, a medida que se van
desplegando nuevas y más eficientes interfaces radio, y de que el tráfico de datos y multimedia va
en aumento, existe la creciente preocupación de que la infraestructura de transporte (backhaul) de
la red celular pueda convertirse en el cuello de botella en algunos escenarios. En este contexto, la
tesis se centra en el desarrollo de técnicas de gestión de recursos que consideran de manera
conjunta la gestión de recursos en la interfaz radio y el backhaul. Esto conduce a un nuevo
paradigma donde los recursos del backhaul se consideran no sólo en la etapa de dimensionamiento,
sino que además son incluidos en la problemática de gestión de recursos.
Sobre esta base, el primer objetivo de la tesis consiste en evaluar los requerimientos de
capacidad en las redes de acceso radio que usan IP como tecnología de transporte, de acuerdo a las
recientes tendencias de la arquitectura de red. En particular, se analiza el impacto que tiene una
solución de transporte basada en IP sobre la capacidad de transporte necesaria para satisfacer los
requisitos de calidad de servicio en la red de acceso. La evaluación se realiza en el contexto de la
red de acceso radio de UMTS, donde se proporciona una caracterización detallada de la interfaz
Iub. El análisis de requerimientos de capacidad se lleva a cabo para dos diferentes escenarios:
canales dedicados y canales de alta velocidad. Posteriormente, con el objetivo de aprovechar
totalmente los recursos disponibles en el acceso radio y el backhaul, esta tesis propone un marco de
gestión conjunta de recursos donde la idea principal consiste en incorporar las métricas de la red de
transporte dentro del problema de gestión de recursos. A fin de evaluar los beneficios del marco de
gestión de recursos propuesto, esta tesis se centra en la evaluación del problema de asignación de
base, como estrategia para distribuir el tráfico entre las estaciones base en función de los niveles de
carga tanto en la interfaz radio como en el backhaul. Este problema se analiza inicialmente
considerando una red de acceso radio genérica, mediante la definición de un modelo analítico
basado en cadenas de Markov. Dicho modelo permite calcular la ganancia de capacidad que puede
alcanzar la estrategia de asignación de base propuesta. Posteriormente, el análisis de la estrategia
propuesta se extiende considerando tecnologías específicas de acceso radio. En particular, en el
contexto de redes WCDMA se desarrolla un algoritmo de asignación de base basado en simulatedannealing
cuyo objetivo es maximizar una función de utilidad que refleja el grado de satisfacción
de las asignaciones respecto los recursos radio y transporte. Finalmente, esta tesis aborda el diseño
y evaluación de un algoritmo de asignación de base para los futuros sistemas de banda ancha
basados en OFDMA. En este caso, el problema de asignación de base se modela como un problema
de optimización mediante el uso de un marco de funciones de utilidad y funciones de coste de
recursos. El problema planteado, que considera que existen restricciones de recursos tanto en la
interfaz radio como en el backhaul, es mapeado a un problema de optimización conocido como
Multiple-Choice Multidimensional Knapsack Problem (MMKP). Posteriormente, se desarrolla un
algoritmo de asignación de base heurístico, el cual es evaluado y comparado con esquemas de
asignación basados exclusivamente en criterios radio. El algoritmo concebido se basa en el uso de
los multiplicadores de Lagrange y está diseñado para aprovechar de manera simultánea el balanceo
de carga en la intefaz radio y el backhaul.Postprint (published version
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