Philosophiae Doctor - PhD / The objective of the thesis research is to design such vertical handoff decision algorithms in order for mobile field workers and other mobile users equipped with contemporary multimode mobile devices to communicate seamlessly in the NGWN. In order to tackle this research objective, we used fuzzy logic and fuzzy inference systems to design a suitable handoff initiation algorithm that can handle imprecision and uncertainties in data and process multiple vertical handoff initiation parameters (criteria); used the fuzzy multiple attributes decision making method and context awareness to design a suitable access network selection function that can handle a tradeoff among many handoff metrics including quality of service requirements (such as network conditions and system performance), mobile terminal conditions, power requirements, application types, user preferences, and a price model; used genetic algorithms and simulated annealing to optimise the access network selection function in order to dynamically select the optimal available access network for handoff; and we focused in particular on an interesting use case: vertical handoff decision between mobile WiMAX and UMTS access networks. The implementation of our handoff decision algorithm will provide a network selection mechanism to help mobile users select the best wireless access network among all available wireless access networks, that is, one that provides always best connected services to users. / South Africa

Philosophiae Doctor - PhD / Seamless mobility is the missing ingredient needed to address the inefficient communication problems faced by the field workforces of service companies that are using field workforce automation solutions to streamline and optimise the operations of their field workforces in an increasingly competitive market place. The key enabling function for achieving seamless mobility and seamless service continuity is seamless handoffs across heterogeneous wireless access networks. A challenging issue in the multi-service next generation wireless network (NGWN) is to design intelligent and optimal vertical handoff decision algorithms, beyond traditional ones that are based on only signal strength, to determine when to perform a handoff and to provide optimal choice of access network technology among all available access networks for users equipped with multimode mobile terminals. The objective of the thesis research is to design such vertical handoff decision algorithms in order for mobile field workers and other mobile users equipped with contemporary multimode mobile devices to communicate seamlessly in the NGWN. In order to tackle this research objective, we used fuzzy logic and fuzzy inference systems to design a suitable handoff initiation algorithm that can handle imprecision and uncertainties in data and process multiple vertical handoff initiation parameters (criteria); used the fuzzy multiple attributes decision making method and context awareness to design a suitable access network selection function that can handle a tradeoff among many handoff metrics including quality of service requirements (such as network conditions and system performance), mobile terminal conditions, power requirements, application types, user preferences, and a price model; used genetic algorithms and simulated annealing to optimise the access network selection function in order to dynamically select the optimal available access network for handoff; and we focused in particular on an interesting use case: vertical handoff decision between mobile WiMAX and UMTS access networks. The implementation of our handoff decision algorithm will provide a network selection mechanism to help mobile users select the best wireless access network among all available wireless access networks, that is, one that provides always best connected services to users

Submitted by Kamila Costa (kamilavasconceloscosta@gmail.com) on 2015-06-11T19:32:18Z No. of bitstreams: 1 Dissertação-Alex F D Monteiro.pdf: 2575711 bytes, checksum: b0ebf6137549e07b5c23b0bb5d4a8632 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-06-15T18:00:46Z (GMT) No. of bitstreams: 1 Dissertação-Alex F D Monteiro.pdf: 2575711 bytes, checksum: b0ebf6137549e07b5c23b0bb5d4a8632 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-06-15T18:04:56Z (GMT) No. of bitstreams: 1 Dissertação-Alex F D Monteiro.pdf: 2575711 bytes, checksum: b0ebf6137549e07b5c23b0bb5d4a8632 (MD5) / Made available in DSpace on 2015-06-15T18:04:57Z (GMT). No. of bitstreams: 1 Dissertação-Alex F D Monteiro.pdf: 2575711 bytes, checksum: b0ebf6137549e07b5c23b0bb5d4a8632 (MD5) Previous issue date: 2015-02-20 / Não Informada / The demand for different applications and services on the Internet has grown dramatically in recent years. To meet this demand, various wireless communication technologies with different characteristics have been used to provide access these services. However, not always technology wireless access used is the most appropriate to the requirements of the applications and services or even the user's interest in issues such as access speed, financial cost and power consumption. The main issue is how to identify the best network and access interface that offers the best value for money, meeting user expectations and operating autonomously. In order to propose a solution to address this issue, this paper describes a new interface selection mechanism based on analysis of contextual information obtained from the user and the device. This mechanism, called CANS (Context-Aware Network Selection), is composed of an acquisition module of context information and selection strategies and management interfaces specific to each type of access technology. The CANS is designed to operate on computers that support the Linux operating system. The evaluation of the proposed mechanism is held in the real environment. The results show that the adoption of the proposed selection strategies enables the user to better exploit the advantages of access technologies in an environment, achieving a reduction in device power consumption and financial cost. / A demanda por diferentes aplicações e serviços na Internet tem crescido drasticamente nos últimos anos. Para atender esta demanda, diversas tecnologias de comunicação sem fio com diferentes características têm sido utilizadas para fornecer acesso estes serviços. Contudo, nem sempre a tecnologia de acesso sem fio utilizada é a mais adequada aos requisitos exigidos pelas aplicações e serviços ou mesmo a questões de interesse do usuário como velocidade de acesso, custo financeiro e consumo de energia. A questão principal é como identificar a melhor rede e interface de acesso que ofereça a melhor relação custo benefício, atendendo as expectativas do usuário e que opere de forma autônoma. Com o intuito de propor uma solução para tratar essa questão, este trabalho descreve um novo mecanismo de seleção de interfaces baseado em análise de informações contextuais obtidas a partir do usuário e do dispositivo. Este mecanismo, denominado CANS (Context-Aware Network Selection), é composto por um módulo de aquisição de informações de contexto e por estratégias de seleção e gerenciamento de interfaces específicas a cada tipo de tecnologia de acesso. O CANS é projetado para operar em computadores que suportem o sistema operacional Linux. A avaliação do mecanismo proposto é realizada em ambiente real. Os resultados mostram que a adoção das estratégias de seleção propostas possibilita ao usuário explorar melhor as vantagens das tecnologias de acesso em um ambiente, obtendo uma redução no consumo de energia do dispositivo e do custo financeiro.

Wireless communication systems have evolved substantially over the last two decades. The explosive growth of the wireless communications market is expected to continue in the future, as the demand for all types of wireless services is increasing. Beside providing higher data rates, next generation wireless networks (NGWN) are expected to have advanced capabilities such as interoperability, efficient spectrum utilization along with a wide variety of applications over different domains (e.g., public safety and military, aeronautical networks, femtocells, and so on) to the mobile users while serving as many users as possible. However, these advanced capabilities and services must be achieved under the constraint of limited available resources such as electromagnetic spectrum and power. In addition, NGWNs (and nodes within) need to modify themselves under rapidly changing conditions such as wireless propagation channel characteristics, traffic load, and so on. Moreover, NGWNs are expected to optimize their parameters by evaluating their experiences in the past. All of these characteristics imply that NGWNs should be equipped with cognitive capabilities including sensing, awareness, adaptation and responding to changing conditions along with learning about the past experiences. In this dissertation, environment, channel, and interference awareness are investigated in detail for NGWN. Methods for being aware of environment, channel, and interference are provided along with some possible ways of adapting several design parameters of NGWNs. In addition, cross-layer optimization issues are addressed from the perspective of both recently emerging technology called cognitive radio (CR) and NGWN.

The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This thesis focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user's velocity and location information are also considered when making the handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user's velocity, user's budget, traffic type, signaling cost, and monetary access cost.

The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This thesis focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user's velocity and location information are also considered when making the handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user's velocity, user's budget, traffic type, signaling cost, and monetary access cost.

The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This thesis focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user's velocity and location information are also considered when making the handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user's velocity, user's budget, traffic type, signaling cost, and monetary access cost. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Nomadic computing aims to be a leading short term revolution in the Internet, however to succeed in this the infrastructure, the protocols, the handoff mechanisms have to be designed and implemented to provide mobile computing with both reliability and transparency. A good deal of the work is addressed by mobile IP itself, but addressing wireless diversity is perhaps the most important next step. Many different wireless technologies are available; while one technology might provide wide coverage, another provides higher bandwidth, but can only be deployed locally, even uni-directional ad-hoc links can be used to carry IP traffic. To take full advantage of the potential infrastructure, a mobile device, with multiple network interfaces, should be able to dynamically switch from one link technology to another; hopefully totally transparently to the user. Moreover, having multiple interfaces allows the device to choose, each time a new connection is established, which interface to select to route the datagrams through, based on the type of service desired. In this thesis a possible solution is presented, involving both vertical handoff optimization and policy management. Our testing device is the the SmartBadge v4, provided with a GPRS link and a 802.11b WLAN interface. / Nomadic Computing har för avsikt att revolutionera dagens Internet tillämpningar. För att lyckas måste dock infrastrukturen, IT protokollen och handoff procedurer utformas och implementeras med intentionen att förse mobilt dataöverföring med både driftsäkerhet och autonoma processer. En stor del av de nödvändiga förutsättningarna är tillgängliga tack vare Mobile IP, men mångfalden inom de befintliga Wireless teknologierna utgör fortfarande ett problem. Det stora antalet disponibla Wireless tekniker varierar från teknologierer som förser användaren med en stor täckningsgrad, till sådana som förser användaren med högre bandbredd, begränsad till lokala anv ändningområden. Även Uni-directional ad-hoc links kan läggas i denna lista av mångfald. För att förverkliga fördelarna med den tänkta infrastrukturen fullt ut måste den mobila enheten kunna utföra omkopplingar från den ena wireless teknologin till den andra, med syftet att vara osynlig för användaren. Utöver detta är det meningen att en apparat med många anslutningar ska kunna välja den anslutning som passar bäst, var gång en ny koppling ska göras, beroende på den tjänst som efterfrågas. Det här examensarbetet presenterar en möjlig lösning, som utnyttjar både Vertical Handoff optimering och Policy Management. Prototyp-enheten vi anv änder oss av för att genomföra undersökningen är Smart Badge v4, utrustad med GPRS och 802.11b Wireless LAN anslutningar.

Abstract The contemporary information age is equipped with rich and affordable telecommunication services. In the future, people have even more flexibility when true wireless Internet and real-time multimedia are provided seamlessly over heterogeneous wireless networks. Optimally combining the capacity and services of the current and emerging networks requires a holistic view of mobility, resource and service management. This thesis contributes to the research and development of these hybrid systems with three main contributions. Firstly, a system architecture for vertical handoff in location-aware heterogeneous wireless networks is proposed. The proposed architecture enables the mobile node to prepare for approaching vertical handoffs and wake-up a hotspot interface. The needed communication procedures are discussed, and inter-related issues of mobility and geolocation information are considered in proportion to usability, advantages and limitations. Secondly, a framework for the analysis of vertical handoff algorithm sensitivity to various mobility parameters including velocity, handoff delay and dwell time is introduced. Handoff smoothing with a dwell-timer is analyzed as one potential scheme for optimizing vertical handoff locally. It is compared to a power based algorithm to find out its sensitivity to the changes in effective data rates, velocity of the terminal and the amount of handoff delay. The analysis focuses on the transition region, having case studies on both moving-in and moving-out scenarios. An optimal value for dwell-timer is found through simulations, showing a performance gain over power based algorithm as a function of mean throughput. The analysis is extended also to a multiple network scenario. Thirdly, experimental results on the behaviour of protocols used in wireless IP networks are presented. Prototype systems demonstrate results of using Mobile IP with a fuzzy logic algorithm for vertical handoff in a heterogeneous network environment and the role of IPv6 when using a voice application in a wireless LAN environment. Latest contributions include developing plug-and-play middleware functionalities for Symbian mobile devices, extending the use of the earlier results to state-of-the-art mobile devices.