149 research outputs found
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
Performance analysis of handoff resource allocation strategies through the state-dependent rejection scheme
The state-dependent rejection scheme (SRS) provides a common framework for analysing existing handoff schemes and for designing new ones easily. Designing new schemes is made simple by determining the appropriate set of state-dependent probabilities. The Markov analysis of SRS is simple and useful for drawing initial conclusions on handoff strategies. The analysis and simulations carried out here demonstrate the capability of SRS to adapt to different mobility and load scenarios and to achieve good performance while targeting quality of service performance metrics.Peer Reviewe
Queueing Networks for Vertical Handover
PhDIt is widely expected that next-generation wireless communication systems will be
heterogeneous, integrating a wide variety of wireless access networks. Of particular
interest recently is a mix of cellular networks (GSM/GPRS and WCDMA) and
wireless local area networks (WLANs) to provide complementary features in terms
of coverage, capacity and mobility support. If cellular/ WLAN interworking is to be
the basis for a heterogeneous network then the analysis of complex handover traffic
rates in the system (especially vertical handover) is one of the most essential issues to
be considered.
This thesis describes the application of queueing-network theory to the modelling of
this heterogeneous wireless overlay system. A network of queues (or queueing
network) is a powerful mathematical tool in the performance evaluation of many
large-scale engineering systems. It has been used in the modelling of hierarchically
structured cellular wireless networks with much success, including queueing
network modelling in the study of cellular/ WLAN interworking systems. In the
process of queueing network modelling, obtaining the network topology of a system
is usually the first step in the construction of a good model, but this topology
analysis has never before been used in the handover traffic study in heterogeneous
overlay wireless networks. In this thesis, a new topology scheme to facilitate the
analysis of handover traffic is proposed.
The structural similarity between hierarchical cellular structure and heterogeneous
wireless overlay networks is also compared. By replacing the microcells with
WLANs in a hierarchical structure, the interworking system is modelled as an open
network of Erlang loss systems and with the new topology, the performance
measures of blocking probabilities and dropping probabilities can be determined.
Both homogeneous and non-homogeneous traffic have been considered, circuit
switched and packet-switched. Example scenarios have been used to validate the
models, the numerical results showing clear agreement with the known validation
scenarios
An intelligent-agent approach for managing congestion in W-CDMA networks
PhDResource Management is a crucial aspect in the next generation cellular networks
since the use of W-CDMA technology gives an inherent flexibility in managing the
system capacity. The concept of a âService Level Agreementâ (SLA) also plays a
very important role as it is the means to guarantee the quality of service provided to
the customers in response to the level of service to which they have subscribed.
Hence there is a need to introduce effective SLA-based policies as part of the radio
resource management.
This work proposes the application of intelligent agents in SLA-based control in
resource management, especially when congestion occurs. The work demonstrates the
ability of intelligent agents in improving and maintaining the quality of service to
meet the required SLA as the congestion occurs.
A particularly novel aspect of this work is the use of learning (here Case Based
Reasoning) to predict the control strategies to be imposed. As the system environment
changes, the most suitable policy will be implemented. When congestion occurs, the
system either proposes the solution by recalling from experience (if the event is
similar to what has been previously solved) or recalculates the solution from its
knowledge (if the event is new). With this approach, the system performance will be
monitored at all times and a suitable policy can be immediately applied as the system
environment changes, resulting in maintaining the system quality of service
3G migration in Pakistan
The telecommunication industry in Pakistan has come a long way since the country\u27s independence in 1947. The initial era could be fairly termed as the PTCL (Pakistan Telecommunication Company Limited) monopoly, for it was the sole provider of all telecommunication services across the country. It was not until four decades later that the region embarked into the new world of wireless communication, hence ending the decades old PTCL monopoly. By the end of the late 1990\u27s, government support and international investment in the region opened new doors to innovation and better quality, low cost, healthy competition. Wireless licenses for the private sector in the telecommunication industry triggered a promising chain of events that resulted in a drastic change in the telecommunication infrastructure and service profile. The newly introduced wireless (GSM) technology received enormous support from all stakeholders (consumers, regulatory body, and market) and caused a vital boost in Pakistan\u27s economy. Numerous tangential elements had triggered this vital move in the history of telecommunications in Pakistan. Entrepreneurs intended to test the idea of global joint ventures in the East and hence the idea of international business became a reality. The technology had proven to be a great success in the West, while Pakistan\u27s telecom consumer had lived under the shadow of PTCL dominance for decades and needed more flexibility. At last the world was moving from wired to wireless! Analysts termed this move as the beginning of a new era. The investors, telecommunication businesses, and Pakistani treasury prospered. It was a win-win situation for all involved. The learning curve was steep for both operators and consumers but certainly improved over time. In essence, the principle of deploying the right technology in the right market at the right time led to this remarkable success. The industry today stands on the brink of a similar crossroads via transition from second generation to something beyond. With the partial success of 3G in Europe and the USA, the government has announced the release of three 3G licenses by mid 2009. This decision is not yet fully supported by all but still initiated parallel efforts by the operators and the vendors to integrate this next move into their existing infrastructure
Mobile and Wireless Communications
Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies
Interference analysis of and dynamic channel assignment algorithms in TDâCDMA/TDD systems
The radio frequency spectrum for commercial wireless communications has become an expensive
commodity. Consequently, radio access techniques are required which enable the efficient
exploitation of these resources. This, however, is a difficult task due to an increasing diversity
of wireless services. Hence, in order to achieve acceptable spectrum efficiency a flexible airâ
interface is required.
It has been demonstrated that code division multiple access (CDMA) provides flexibility by
enabling efficient multi user access in a cellular environment. In addition, time division duplex
(TDD) as compared to frequency division duplex (FDD) represents an appropriate method to
cater for the asymmetric use of a duplex channel. However, the TDD technique is subject to
additional interference mechanisms in particular if neighbouring cells require different rates of
asymmetry. If TDD is combined with an interference limited multiple access technique such as
CDMA, the additional interference mechanism represents an important issue. This issue poses
the question of whether a CDMA/TDD airâinterface can be used in a cellular environment.
The problems are eased if a hybrid TDMA (time division multiple access) / CDMA interface
(TDâCDMA) is used. The reason for this is that the TDMA component adds another degree
of freedom which can be utilised to avoid interference. This, however, requires special channel
assignment techniques.
This thesis analyses cellular CDMA/TDD systems used in indoor environments. A key parameter
investigated is the interference in such systems. In the interference analysis a special
focus is placed on adjacent channel interference since the jamming entity and victim entity can
be in close proximity. The interference analysis shows that coâlocation of BSâs using adjacent
channels is not feasible for an adjacent channel protection factor that is less than 40 dB
and frame synchronisation errors of more than 10%. Furthermore, it is demonstrated that ideal
frame synchronisation does not necessarily yield the highest capacity. As a consequence, a new
technique termed âTSâopposingâ is introduced. This method is intended to enable a cellular
TDâCDMA/TDD system to apply cell independent channel asymmetry. For this purpose, a
centralised DCA is developed. It is found that this algorithm indeed enables neighbouring cells
to adopt different rates of asymmetry without a significant capacity loss.
Moreover, a decentralised DCA algorithm based on the TSâopposing principle is developed.
In this context, a novel TS assignment concept is proposed which reduces the complexity associated
with the TSâopposing technique. In addition, the TS assignment plan allows for full
spatial coverage. It is shown that the capacity of a TDâCDMA/TDD interface can be greater
than the capacity of an equivalent FDD interface. The performance of the decentralised DCA
algorithm is limited by the interference in the uplink. Therefore, additional methods which assist
in reducing the interference in the uplink are envisaged to further improve the performance
of the decentralised DCA algorithm.
The exploitation of the TSâopposing technique in two different ways demonstrates that this
method can be used to improve the performance of a TDâCDMA/TDD system significantly
D5.2 - Evaluation of Selected Measurement-based Techniques
Deliverable D5.2 del projecte FARAMIRPreprin
Level based sampling techniques for energy conservation in large scale wireless sensor networks
As the size and node density of wireless sensor networks (WSN) increase,the energy conservation problem becomes more critical and the conventional methods become inadequate. This dissertation addresses two different problems in large scale WSNs where all sensors are involved in monitoring,but the traditional practice of periodic transmissions of observations from all sensors would drain excessive amount of energy.
In the first problem,monitoring of the spatial distribution of a two dimensional correlated signal is considered using a large scale WSN. It is assumed that sensor observations are heavily affected by noise. We present an approach that is based on detecting contour lines of the signal distribution to estimate the spatial distribution of the signal without involving all sensors in the network. Energy efficient algorithms are proposed for detecting and tracking the temporal variation of the contours. Optimal contour levels that minimize the estimation error and a practical approach for selection of contour levels are explored. Performance of the proposed algorithm is explored with different types of contour levels and detection parameters.
In the second problem,a WSN is considered that performs health monitoring of equipment from a power substation. The monitoring applications require transmissions of sensor observations from all sensor nodes on a regular basis to the base station,which is very costly in terms of communication cost. To address this problem,an efficient sampling technique using level-crossings (LCS) is proposed. This technique saves communication cost by suppressing transmissions of data samples that do not convey much information. The performance and cost of LCS for several different level-selection schemes are investigated. The number of required levels and the maximum sampling period for practical implementation of LCS are studied. Finally,in an experimental implementation of LCS with MICAzmote,the performance and cost of LCS for temperature sensing with uniform,logarithmic and a combined version of uniform and logarithmically spaced levels are compared with that using periodic sampling
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