16 research outputs found
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Investigation of efficient resource allocation schemes for WiMAX networks
This thesis was submitted for the degree of Master of Philosophy and was awarded by Brunel University on 9 July 2008.WiMax (Worldwide Interoperability for Microwave Access) is a promising wireless technology with the aim of providing the last mile wireless broadband access designed for both fixed and mobile consumers as an alternative solution to the wired DSL and cable access schemes. The purpose of this research project is to investigate efficient resource allocation algorithms for WiMax. To achieve this goal, we investigate efficient PHY layer Partial Usage of SubCarriers (PUSC) allocation as well as MAC layer piggyback bandwidth request mechanisms. At the PHY layer we proposed improvements on the Uplink and Downlink PUSC subcarrier allocation scheme. For the Uplink PUSC we suggested a method by allocating different frequencies to neighbouring cells in combination with the Integer Frequency Reuse (IFR) and Fractional Frequency Reuse (FFR) in order to reduce interferences and collisions. The simulation results exhibit that collision rates can be reduced to zero for both IFR and FFR patterns with the proposed improvement by assuming that perfect power control is used in the system. In addition, there is no collision at cell edges. The results also show that FFR patterns achieve lower inter-cell interference and higher capacities as compared to the IFR patterns. For the Downlink PUSC we introduced an offset scheme with the purpose of increasing the number of users in the system. At the MAC layer we propose an improvement on the piggyback bandwidth request mechanism by increasing the size of the piggyback bandwidth request in order to reduce the number of bandwidth requests and hence improve the resource utilisation. The simulation results demonstrate that our improved scheme achieves higher throughput, less delay and packet loss rates as compared to the standardised piggyback bandwidth request mechanism
Acesso banda larga sem fios em ambientes heterogéneos de próxima geração
Doutoramento em Engenharia InformĂĄticaO acesso ubĂquo Ă Internet Ă© um dos principais desafios para os operadores
de telecomunicaçÔes na prĂłxima dĂ©cada. O nĂșmero de utilizadores da Internet
estĂĄ a crescer exponencialmente e o paradigma de acesso "always connected,
anytime, anywhere" Ă© um requisito fundamental para as redes mĂłveis de
próxima geração. A tecnologia WiMAX, juntamente com o LTE, foi
recentemente reconhecida pelo ITU como uma das tecnologias de acesso
compatĂveis com os requisitos do 4G. Ainda assim, esta tecnologia de acesso
não estå completamente preparada para ambientes de próxima geração,
principalmente devido à falta de mecanismos de cross-layer para integração de
QoS e mobilidade. Adicionalmente, para além das tecnologias WiMAX e LTE,
as tecnologias de acesso rĂĄdio UMTS/HSPA e Wi-Fi continuarĂŁo a ter um
impacto significativo nas comunicaçÔes móveis durante os próximos anos.
Deste modo, Ă© fundamental garantir a coexistĂȘncia das vĂĄrias tecnologias de
acesso rĂĄdio em termos de QoS e mobilidade, permitindo assim a entrega de
serviços multimédia de tempo real em redes móveis.
Para garantir a entrega de serviços multimédia a utilizadores WiMAX, esta
Tese propÔe um gestor cross-layer WiMAX integrado com uma arquitectura de
QoS fim-a-fim. A arquitectura apresentada permite o controlo de QoS e a
comunicação bidireccional entre o sistema WiMAX e as entidades das
camadas superiores. Para além disso, o gestor de cross-layer proposto é
estendido com eventos e comandos genéricos e independentes da tecnologia
para optimizar os procedimentos de mobilidade em ambientes WiMAX. Foram
realizados testes para avaliar o desempenho dos procedimentos de QoS e
mobilidade da arquitectura WiMAX definida, demonstrando que esta Ă©
perfeitamente capaz de entregar serviços de tempo real sem introduzir custos
excessivos na rede.
No seguimento das extensÔes de QoS e mobilidade apresentadas para a
tecnologia WiMAX, o Ăąmbito desta Tese foi alargado para ambientes de
acesso sem-fios heterogéneos. Neste sentido, é proposta uma arquitectura de
mobilidade transparente com suporte de QoS para redes de acesso multitecnologia.
A arquitectura apresentada integra uma versĂŁo estendida do IEEE
802.21 com suporte de QoS, bem como um gestor de mobilidade avançado
integrado com os protocolos de gestĂŁo de mobilidade do nĂvel IP. Finalmente,
para completar o trabalho desenvolvido no Ăąmbito desta Tese, Ă© proposta uma
extensĂŁo aos procedimentos de decisĂŁo de mobilidade em ambientes
heterogéneos para incorporar a informação de contexto da rede e do terminal.
Para validar e avaliar as optimizaçÔes propostas, foram desenvolvidos testes
de desempenho num demonstrador inter-tecnologia, composta pelas redes de
acesso WiMAX, Wi-Fi e UMTS/HSPA.Ubiquitous Internet access is one of the main challenges for the
telecommunications industry in the next decade. The number of users
accessing the Internet is growing exponentially and the network access
paradigm of âalways connected, anytime, anywhereâ is a central requirement
for the so-called Next Generation Mobile Networks (NGMN). WiMAX, together
with LTE, was recently recognized by ITU as one of the compliant access
technologies for 4G. Nevertheless, WiMAX is not yet fully prepared for next
generation environments, mainly due to the lack of QoS and mobility crosslayer
procedures to support real-time multimedia services delivery.
Furthermore, besides the 4G compliant WiMAX and LTE radio access
technologies, UMTS/HSPA and Wi-Fi will also have a significant impact in the
mobile communications during the next years. Therefore, it is fundamental to
ensure the coexistence of multiple radio access technologies in what QoS and
mobility procedures are concerned, thereby allowing the delivery of real-time
services in mobile networks.
In order to provide the WiMAX mobile users with the demanded multimedia
services, it is proposed in this Thesis a WiMAX cross-layer manager integrated
in an end-to-end all-IP QoS enabled architecture. The presented framework
enables the QoS control and bidirectional communication between WiMAX and
the upper layer network entities. Furthermore, the proposed cross-layer
framework is extended with media independent events and commands to
optimize the mobility procedures in WiMAX environments. Tests were made to
evaluate the QoS and mobility performance of the defined architecture,
demonstrating that it is perfectly capable of handling and supporting real time
services without introducing an excessive cost in the network.
Following the QoS and mobility extensions provided for WiMAX, the scope of
this Thesis is broaden and a seamless mobility architecture with QoS support in
heterogeneous wireless access environments is proposed. The presented
architecture integrates an extended version of the IEEE 802.21 framework with
QoS support, as well as an advanced mobility manager integrated with the IP
level mobility management protocols. Finally, to complete the work within the
framework of this Thesis, it is proposed an extension to the handover decisionmaking
processes in heterogeneous access environments through the
integration of context information from both the network entities and the enduser.
Performance tests were developed in a real testbed to validate the
proposed optimizations in an inter-technology handover scenario involving
WiMAX, Wi-Fi and UMTS/HSPA
Quality of service and resource management in IP and wireless networks
A common theme in the publications included in this thesis is the quality of service and resource management in IP and wireless networks. This thesis presents novel algorithms and implementations for admission control in IP and IEEE 802.16e networks, active queue management in EGPRS, WCDMA, and IEEE 802.16e networks, and scheduling in IEEE 802.16e networks. The performance of different algorithms and mechanisms is compared with the prior art through extensive ns-2 simulations.
We show that similar active queue management mechanisms, such as TTLRED, can be successfully used to reduce the downlink delay (and in some cases even improve the TCP goodput) in different bottlenecks of IP, EGPRS, WCDMA, and IEEE 802.16e access networks. Moreover, almost identical connection admission control algorithms can be applied both in IP access networks and at IEEE 802.16e base stations. In the former case, one just has to first gather the link load information from the IP routers.
We also note that DiffServ can be used to avoid costly overprovisioning of the backhaul in IEEE 802.16e networks. We present a simple mapping between IEEE 802.16e data delivery services and DiffServ traffic classes, and we propose that IEEE 802.16e base stations should take the backhaul traffic load into account in their admission control decisions.
Moreover, different IEEE 802.16e base station scheduling algorithms and uplink channel access mechanisms are studied. In the former study, we show that proportional fair scheduling offers superior spectral efficiency when compared to deficit round-robin, though in some cases at the cost of increased delay. Additionally, we introduce a variant of deficit round-robin (WDRR), where the quantum value depends on the modulation and coding scheme.
We also show that there are several ways to implement ertPS in an efficient manner, so that during the silence periods of a VoIP call no uplink slots are granted. The problem here, however, is how to implement the resumption after the silence period while introducing as little delay as possible
An assessment of quality, class and grade of service (QoS, CoS and GoS) over worldwide interoperability for microwave access (WiMax) networks through performance evaluation of bandwidth
The Dwesa WiMAX network provides broadband communications over wireless connectivity for various types of multimedia traffic, such as emailing, browsing, VoIP, file transfer, etc. to the community members. The community members of Dwesa use schoolsâ computer labs to access the network and generate the aforementioned multimedia packets on dedicated timeslots and thus cause network congestion during such timeslots. Against this background, WiMAX implementation has faced several challenges in living up to its objectives in RMAs. Quality of Service (QoS) degradation as a result of high traffic demands remains one of the challenges thwarting WiMAX implementation. The GoS is also bound to get compromised as connectivity demands arise consistently with more subscribers connecting to the network, making it difficult to measure the success a subscriber is expected to have in accessing the network. The CoS and SchedType play a significant role in the redistribution of the available bandwidth to all bandwidth requests. This research project exploits this avenue to assess the resultant degradation of QoS and GoS caused by the inconsistent availability of bandwidth as redistributed by the CoS combination with a SchedType. The four CoS which are, namely, the UGS, rtPS, nrtPS and BE were implemented with the different SchedTypes, namely, MBQOS, FCFS and rtPS. Although the implementation process was conducted in a simulated environment using NS-3, the simulated network emulated the network setup implemented in Dwesa. The outcomes of the implementation suggests that certain combinations of the CoSâs with SchedTypes can lead to degradation of QoS whilst some combinations can redistribute the available bandwidth to ensure the provisioning of guaranteed QoS
Cooperative positioning studies based on WLANs
Location information and location-based service have gained importance in recent years because, based on their concept, a new business market has been opened which encompass emergency services, security, monitoring, tracking, logistics, etc. Nowadays, the most developed positioning systems, namely the Global Navigation Satellite Systems (GNSS), are meant for outdoor use. In order to integrate outdoor and indoor localization in the same mobile application, several lines of research have been created for the purpose of investigating the possibility of wireless network technologies and of overcoming the challenges faced by GNSS in performing localization and navigation in indoor environments. The benefit in using wireless networks is that they provide a minimally invasive solution which is based on software algorithms that can be implemented and executed in the Mobile Station (MS) or in a Location Server connected to the network.
This thesis focuses on the development of localization approaches based on Received Signal Strength (RSS) and applied in WLANs. Such approaches demonstrated in recent research advances that RSS-based localization algorithms are the simplest existing approaches due to the fact that the RSSs are most accessible existing measurements. RSS measurements can be used with two main algorithms, which are addressed in this thesis: Fingerprinting method (FP) and Pathloss method (PL). These two methods can be applied in both cooperative and non-cooperative algorithms. Such algorithms are evaluated here in terms of Root Mean Square Error (RMSE) for both simulated and real-field data
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ReSCon '09, Research Student Conference: Book of Abstracts
The second SED Research Student Conference (ReSCon2009) was hosted over three days, 22-24 June 2009, in the Lecture Centre at Brunel University. The conference consisted of technical presentations, a poster session and social events. The abstracts and presentations were the result of ongoing research by postgraduate research students from the School of Engineering and Design at Brunel University. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School
Wireless Network Communications Overview for Space Mission Operations
The mission of the On-Board Wireless Working Group (WWG) is to serve as a general CCSDS focus group for intra-vehicle wireless technologies. The WWG investigates and makes recommendations pursuant to standardization of applicable wireless network protocols, ensuring the interoperability of independently developed wireless communication assets. This document presents technical background information concerning uses and applicability of wireless networking technologies for space missions. Agency-relevant driving scenarios, for which wireless network communications will provide a significant return-on-investment benefiting the participating international agencies, are used to focus the scope of the enclosed technical information
Performance analysis of 4G wireless networks using system level simulator
Doutoramento em Engenharia ElectrotécnicaIn the last decade, mobile wireless communications have witnessed an explosive
growth in the userâs penetration rate and their widespread deployment around the
globe. In particular, a research topic of particular relevance in telecommunications
nowadays is related to the design and implementation of mobile communication
systems of 4th generation (4G). 4G networks will be characterized by the support
of multiple radio access technologies in a core network fully compliant with the
Internet Protocol (all IP paradigms). Such networks will sustain the stringent
quality of service (QoS) requirements and the expected high data rates from the
type of multimedia applications (i.e. YouTube and Skype) to be available in the
near future. Therefore, 4G wireless communications system will be of paramount
importance on the development of the information society in the near future.
As 4G wireless services will continue to increase, this will put more and more
pressure on the spectrum availability. There is a worldwide recognition that
methods of spectrum managements have reached their limit and are no longer
optimal, therefore new paradigms must be sought. Studies show that most of the
assigned spectrum is under-utilized, thus the problem in most cases is inefficient
spectrum management rather spectrum shortage. There are currently trends
towards a more liberalized approach of spectrum management, which are tightly
linked to what is commonly termed as Cognitive Radio (CR).
Furthermore, conventional deployment of 4G wireless systems (one BS in cell and
mobile deploy around it) are known to have problems in providing fairness (users
closer to the BS are more benefited relatively to the cell edge users) and in
covering some zones affected by shadowing, therefore the use of relays has been
proposed as a solution.
To evaluate and analyse the performances of 4G wireless systems software tools
are normally used. Software tools have become more and more mature in recent
years and their need to provide a high level evaluation of proposed algorithms and
protocols is now more important. The system level simulation (SLS) tools provide
a fundamental and flexible way to test all the envisioned algorithms and protocols
under realistic conditions, without the need to deal with the problems of live
networks or reduced scope prototypes. Furthermore, the tools allow network
designers a rapid collection of a wide range of performance metrics that are useful
for the analysis and optimization of different algorithms.
This dissertation proposes the design and implementation of conventional system
level simulator (SLS), which afterwards enhances for the 4G wireless technologies
namely cognitive Radios (IEEE802.22) and Relays (IEEE802.16j). SLS is then
used for the analysis of proposed algorithms and protocols.FC
Compilation of thesis abstracts, June 2007
NPS Class of June 2007This quarterâs Compilation of Abstracts summarizes cutting-edge, security-related research conducted by NPS students and presented as theses, dissertations, and capstone reports. Each expands knowledge in its field.http://archive.org/details/compilationofsis109452750