Heterogeneous Wireless Networks (HWNs) are composite networks made of different wireless access technologies, possibly with overlapping coverage. Users with multi-mode terminals in HWNs will be able to initiate connectivity in the access technology that best suits their attributes and the requirements of their applications. The true potential of HWNs, however, is only realized through allowing users to maintain their sessions when toggling from one access technology to another. Such inter-technology handoffs, called vertical handoffs, will enable users to persistently select the most appropriate network, and not just at session initiation. For operators, HWNs pave the road to higher profitability through more capable networks where the complementary advantages of individual access technologies are combined. However, the characteristics of HWNs challenge traditional arguments for designing Radio Resource Management (RRM) frameworks. Managing the resources of an access technology in an HWN independently of other networks with which its overlaid risks underutilization and resource mismanagement. The dynamic nature of user demands in HWNs also calls for RRM modules with controlled operational cost. More importantly, the unique characteristics of HWNs call for non-traditional solutions that exploit the ``complementarity" of the individual networks. In this thesis, we address these issues through proposing a framework for RRM in HWNs. Our framework comprises three key components. The first component is aimed at improving allocation policies in HWNs through joint allocation policies involving provisioning and admission control. In addition, we outline the basis for achieving robust provisioning that accommodates variability in user demands, but also in network capabilities. The second component is concerned with controlling the operational cost of RRM modules. As a case study, we choose bandwidth adaptation algorithms and optimize their performance. We also introduce the notion of stochastic triggers which enables operators to direct the operation of a RRM module based on the operator's objectives and network conditions. In the third component, we introduce a new module that exploits vertical handoffs to the benefit of network operators. Such operator motivated vertical handoffs can be utilized in instances of congestion control. They can also be used proactively to achieve long-term objectives such as load balancing or service delivery cost reduction. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2007-09-28 04:54:46.819

No / The complementary features of various wireless access technologies in heterogeneous wireless networks make it attractive and challenging to offer users an always best connected (ABC) service. To achieve this goal, the dynamic network selection has received many research efforts. However, most of the existing work have focused on the network layer performance and ignored the consideration of energy efficiency. To fill this gap, an energy-efficient network selection scheme is proposed in this paper to improve the energy efficiency of wireless network access in heterogeneous wireless networks environment. The dynamics of network selection is formulated as the process of an evolutionary game. The users in different service areas complete for the data rate from different wireless networks (i.e., WMAN, cellular networks, and WLAN), and the network selection made by a user is based on its payoff that is a function of the data rate and power consumption. The addressed problem is then modelled by the replicator dynamics. Simulation results are presented to demonstrate the significant performance improvement compared to the existing scheme.

The integration of heterogeneous access networks is becoming a possible feature of 4G wireless networks. It is challenging to deliver the multimedia services over such integrated networks because of the discrepancy in the bandwidth of different networks. This thesis presents an adaptive approach that combines source rate adaptation and buffering to achieve high quality VBR video streaming with less quality variation over an integrated two-tier network. Statistical information of the residence time in each network or localization information are utilized to anticipate the handoff occurrence. The performance of this approach is analyzed under the CBR case using a Markov reward model. Simulation under the CBR and VBR cases is conducted for different types of network models. The results are compared with a dynamic programming algorithm as well as other naive or intuitive algorithms, and proved to be promising.

The integration of heterogeneous access networks is becoming a possible feature of 4G wireless networks. It is challenging to deliver the multimedia services over such integrated networks because of the discrepancy in the bandwidth of different networks. This thesis presents an adaptive approach that combines source rate adaptation and buffering to achieve high quality VBR video streaming with less quality variation over an integrated two-tier network. Statistical information of the residence time in each network or localization information are utilized to anticipate the handoff occurrence. The performance of this approach is analyzed under the CBR case using a Markov reward model. Simulation under the CBR and VBR cases is conducted for different types of network models. The results are compared with a dynamic programming algorithm as well as other naive or intuitive algorithms, and proved to be promising.

The next-generation wireless communications have been envisioned to be supported by heterogeneous networks using various wireless access technologies. The popular cellular networks and wireless local area networks (WLANs) present perfectly complementary characteristics in terms of service capacity, mobility support, and quality-of-service (QoS) provisioning. The cellular/WLAN interworking is thus an effective way to promote the evolution of wireless networks. As an essential aspect of the interworking, resource allocation is vital for efficient utilization of the overall resources. Specially, multi-service provisioning can be enhanced with cellular/WLAN interworking by taking advantage of the complementary network strength and an overlay structure. Call assignment/reassignment strategies and admission control policies are effective resource allocation mechanisms for the cellular/WLAN integrated network. Initially, the incoming calls are distributed to the overlay cell or WLAN according to call assignment strategies, which are enhanced with admission control policies in the target network. Further, call reassignment can be enabled to dynamically transfer the traffic load between the overlay cell and WLAN via vertical handoff. By these means, the multi-service traffic load can be properly shared between the interworked systems. In this thesis, we investigate the load sharing problem for this heterogeneous wireless overlay network. Three load sharing schemes with different call assignment/reassignment strategies and admission control policies are proposed and analyzed. Effective analytical models are developed to evaluate the QoS performance and determine the call admission and assignment parameters. First, an admission control scheme with service-differentiated call assignment is studied to gain insights on the effects of load sharing on interworking effectiveness. Then, the admission scheme is extended by using randomized call assignment to enable distributed implementation. Also, we analyze the impact of user mobility and data traffic variability. Further, an enhanced call assignment strategy is developed to exploit the heavy-tailedness of data call size. Last, the study is extended to a multi-service scenario. The overall resource utilization and QoS satisfaction are improved substantially by taking into account the multi-service traffic characteristics, such as the delay-sensitivity of voice traffic, elasticity and heavy-tailedness of data traffic, and rate-adaptiveness of video streaming traffic.

The next-generation wireless communications have been envisioned to be supported by heterogeneous networks using various wireless access technologies. The popular cellular networks and wireless local area networks (WLANs) present perfectly complementary characteristics in terms of service capacity, mobility support, and quality-of-service (QoS) provisioning. The cellular/WLAN interworking is thus an effective way to promote the evolution of wireless networks. As an essential aspect of the interworking, resource allocation is vital for efficient utilization of the overall resources. Specially, multi-service provisioning can be enhanced with cellular/WLAN interworking by taking advantage of the complementary network strength and an overlay structure. Call assignment/reassignment strategies and admission control policies are effective resource allocation mechanisms for the cellular/WLAN integrated network. Initially, the incoming calls are distributed to the overlay cell or WLAN according to call assignment strategies, which are enhanced with admission control policies in the target network. Further, call reassignment can be enabled to dynamically transfer the traffic load between the overlay cell and WLAN via vertical handoff. By these means, the multi-service traffic load can be properly shared between the interworked systems. In this thesis, we investigate the load sharing problem for this heterogeneous wireless overlay network. Three load sharing schemes with different call assignment/reassignment strategies and admission control policies are proposed and analyzed. Effective analytical models are developed to evaluate the QoS performance and determine the call admission and assignment parameters. First, an admission control scheme with service-differentiated call assignment is studied to gain insights on the effects of load sharing on interworking effectiveness. Then, the admission scheme is extended by using randomized call assignment to enable distributed implementation. Also, we analyze the impact of user mobility and data traffic variability. Further, an enhanced call assignment strategy is developed to exploit the heavy-tailedness of data call size. Last, the study is extended to a multi-service scenario. The overall resource utilization and QoS satisfaction are improved substantially by taking into account the multi-service traffic characteristics, such as the delay-sensitivity of voice traffic, elasticity and heavy-tailedness of data traffic, and rate-adaptiveness of video streaming traffic.

In recent years, there has been a rapid evolution and deployment of wireless networks. In populated areas, high-rate data access is enabled anywhere and anytime with the pervasive wireless infrastructure such as the fourth-generation (4G) cellular systems, IEEE 802.11-based wireless local area networks (WLANs), and IEEE 802.16-based wireless metropolitan area networks (WMANs). In such a heterogeneous wireless access medium, multi-radio devices become a trend for users to conveniently explore various services offered by different wireless systems. This thesis presents radio resource management mechanisms, for bandwidth allocation, call admission control (CAC), and mobile terminal (MT) energy management, that can efficiently exploit the available resources in the heterogeneous wireless medium and enhance the user perceived quality-of-service (QoS). Almost all existing studies on heterogeneous networking are limited to the traditional centralized infrastructure, which is inflexible in dealing with practical scenarios, especially when different networks are operated by different service providers. In addition, in most current wireless networks, mobile users are simply viewed as service recipients in network operation, with passive transceivers completely or partially under the control of base stations or access points. In this thesis, we present efficient decentralized bandwidth allocation and CAC mechanisms that can support single-network and multi-homing calls. The decentralized architecture gives an active role to the MT in the resource management operation. Specifically, an MT with single-network call can select the best wireless network available at its location, while an MT with multi-homing call can determine a required bandwidth share from each network to satisfy its total required bandwidth. The proposed mechanisms rely on cooperative networking and offer a desirable flexibility between performance measures (in terms of the allocated bandwidth per call and the call blocking probability), and between the performance and the implementation complexity. With the increasing gap between the MT demand for energy and the offered battery capacity, service degradation is expected if the MT cannot efficiently manage its energy consumption. Specifically, for an uplink multi-homing video transmission, the existing studies do not guarantee that the MT available energy can support the entire call, given the battery energy limitation. In addition, the energy management mechanism should take account of video packet characteristics, in terms of packet distortion impact, delay deadline, and precedence constraint, and employ the available resources in the heterogeneous wireless medium. In this thesis, we present MT energy management mechanisms that can support a target call duration, with a video quality subject to the MT battery energy limitation. In addition, we present a statistical guarantee framework that can support a consistent video quality for the target call duration with minimum power consumption.

Global connectivity, for anyone, at anyplace, at anytime, to provide high-speed, high-quality, and reliable communication channels for mobile devices, is now becoming a reality. The credit mainly goes to the recent technological advances in wireless communications comprised of a wide range of technologies, services, and applications to fulfill the particular needs of end-users in different deployment scenarios (Wi-Fi, WiMAX, and 3G/4G cellular systems). In such a heterogeneous wireless environment, one of the key ingredients to provide efficient ubiquitous computing with guaranteed quality and continuity of service is the design of intelligent handoff algorithms. Traditional single-metric handoff decision algorithms, such as Received Signal Strength (RSS) based, are not efficient and intelligent enough to minimize the number of unnecessary handoffs, decision delays, and call-dropping and/or blocking probabilities. This research presented a novel approach for the design and implementation of a multi-criteria vertical handoff algorithm for heterogeneous wireless networks. Several parallel Fuzzy Logic Controllers were utilized in combination with different types of ranking algorithms and metric weighting schemes to implement two major modules: the first module estimated the necessity of handoff, and the other module was developed to select the best network as the target of handoff. Simulations based on different traffic classes, utilizing various types of wireless networks were carried out by implementing a wireless test-bed inspired by the concept of Rudimentary Network Emulator (RUNE). Simulation results indicated that the proposed scheme provided better performance in terms of minimizing the unnecessary handoffs, call dropping, and call blocking and handoff blocking probabilities. When subjected to Conversational traffic and compared against the RSS-based reference algorithm, the proposed scheme, utilizing the FTOPSIS ranking algorithm, was able to reduce the average outage probability of MSs moving with high speeds by 17%, new call blocking probability by 22%, the handoff blocking probability by 16%, and the average handoff rate by 40%. The significant reduction in the resulted handoff rate provides MS with efficient power consumption, and more available battery life. These percentages indicated a higher probability of guaranteed session continuity and quality of the currently utilized service, resulting in higher user satisfaction levels.

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