6,073 research outputs found
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
SymbioCity: Smart Cities for Smarter Networks
The "Smart City" (SC) concept revolves around the idea of embodying
cutting-edge ICT solutions in the very fabric of future cities, in order to
offer new and better services to citizens while lowering the city management
costs, both in monetary, social, and environmental terms. In this framework,
communication technologies are perceived as subservient to the SC services,
providing the means to collect and process the data needed to make the services
function. In this paper, we propose a new vision in which technology and SC
services are designed to take advantage of each other in a symbiotic manner.
According to this new paradigm, which we call "SymbioCity", SC services can
indeed be exploited to improve the performance of the same communication
systems that provide them with data. Suggestive examples of this symbiotic
ecosystem are discussed in the paper. The dissertation is then substantiated in
a proof-of-concept case study, where we show how the traffic monitoring service
provided by the London Smart City initiative can be used to predict the density
of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging
Telecommunications Technologie
Real-Time QoS Routing Protocols in Wireless Multimedia Sensor Networks: Study and Analysis
Many routing protocols have been proposed for wireless sensor networks. These routing protocols are almost always based on energy efficiency. However, recent advances in complementary metal-oxide semiconductor (CMOS) cameras and small microphones have led to the development of Wireless Multimedia Sensor Networks (WMSN) as a class of wireless sensor networks which pose additional challenges. The transmission of imaging and video data needs routing protocols with both energy efficiency and Quality of Service (QoS) characteristics in order to guarantee the efficient use of the sensor nodes and effective access to the collected data. Also, with integration of real time applications in Wireless Senor Networks (WSNs), the use of QoS routing protocols is not only becoming a significant topic, but is also gaining the attention of researchers. In designing an efficient QoS routing protocol, the reliability and guarantee of end-to-end delay are critical events while conserving energy. Thus, considerable research has been focused on designing energy efficient and robust QoS routing protocols. In this paper, we present a state of the art research work based on real-time QoS routing protocols for WMSNs that have already been proposed. This paper categorizes the real-time QoS routing protocols into probabilistic and deterministic protocols. In addition, both categories are classified into soft and hard real time protocols by highlighting the QoS issues including the limitations and features of each protocol. Furthermore, we have compared the performance of mobility-aware query based real-time QoS routing protocols from each category using Network Simulator-2 (NS2). This paper also focuses on the design challenges and future research directions as well as highlights the characteristics of each QoS routing protocol.https://doi.org/10.3390/s15092220
A capacity sharing and stealing strategy for open real-time systems
This paper focuses on the scheduling of tasks with hard and soft real-time constraints
in open and dynamic real-time systems. It starts by presenting a capacity
sharing and stealing (CSS) strategy that supports the coexistence of guaranteed
and non-guaranteed bandwidth servers to efficiently handle soft-tasks’ overloads by
making additional capacity available from two sources: (i) reclaiming unused reserved
capacity when jobs complete in less than their budgeted execution time and
(ii) stealing reserved capacity from inactive non-isolated servers used to schedule
best-effort jobs.
CSS is then combined with the concept of bandwidth inheritance to efficiently
exchange reserved bandwidth among sets of inter-dependent tasks which share resources
and exhibit precedence constraints, assuming no previous information on
critical sections and computation times is available. The proposed Capacity Exchange
Protocol (CXP) has a better performance and a lower overhead when compared
against other available solutions and introduces a novel approach to integrate
precedence constraints among tasks of open real-time systems
Fuzzy Logic Control of Adaptive ARQ for Video Distribution over a Bluetooth Wireless Link
Bluetooth's default automatic repeat request (ARQ) scheme is not suited to video distribution resulting in missed display and decoded deadlines. Adaptive ARQ with active discard of expired packets from the send buffer is an alternative approach. However, even with the addition of cross-layer adaptation to picture-type packet importance, ARQ is not ideal in conditions of a deteriorating RF channel. The paper presents fuzzy logic control of ARQ, based on send buffer fullness and the head-of-line packet's deadline. The advantage of the fuzzy logic approach, which also scales its output according to picture type importance, is that the impact of delay can be directly introduced to the model, causing retransmissions to be reduced compared to all other schemes. The scheme considers both the delay constraints of the video stream and at the same time avoids send buffer overflow. Tests explore a variety of Bluetooth send buffer sizes and channel conditions. For adverse channel conditions and buffer size, the tests show an improvement of at least 4 dB in video quality compared to nonfuzzy schemes. The scheme can be applied to any codec with I-, P-, and (possibly) B-slices by inspection of packet headers without the need for encoder intervention.</jats:p
EVEREST IST - 2002 - 00185 : D23 : final report
Deliverable pĂşblic 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
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