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CAVALCANTI, DAVE ALBERTO TAVARESINTEGRATED ARCHITECTURE AND ROUTING PROTOCOLS FOR HETEROGENEOUS WIRELESS NETWORKS
PhD, University of Cincinnati, 2006, Engineering : Computer Science and Engineering
One of the main challenges in next generation wireless networks is to integrate heterogeneous wireless technologies to provide seamless connectivity, with guaranteed Quality of Service (QoS), to mobile users “anytime, anywhere and with any device”. In this dissertation, we investigate the problem of integrating cellular networks and Wireless Local Area Networks (WLANs) with the multi-hop communication paradigm used in Mobile Ad hoc Networks (MANETs) to exploit all the connectivity alternatives available to different types of Mobile Stations (MSs). We propose an integrated architecture based on three basic functionalities, namely, topology discovery, gateway discovery, and link quality estimation. We combine these three functionalities into an integrated routing mechanism that exploits all connectivity alternatives available in a generic heterogeneous scenario. Then, we provide a simulation-based analysis of our architecture and integrated routing mechanism in different heterogeneous networking scenarios. Our results show improvements in network’s capacity and coverage achieved by our architecture as compared to isolated networks. The results also highlight the importance of the link quality estimation in providing QoS to users, as well as indicate that multi-hop links can be exploited in a controlled network configuration, but the QoS in multi-hop routes cannot be always guaranteed. Furthermore, we address the problem of selecting the best connectivity opportunity for a given service type based on the applications’ QoS requirements, as well as on the network condition and user mobility profile. We propose the Connectivity opportunity Selection Algorithm (CSA) that allows MSs to select the connectivity opportunity most appropriate for a given type of service and mobility profile. Furthermore, we describe how our proposed selection algorithm can be introduced into the IEEE 802.21 standard for Media Independent Handover services.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks.; Routing Protocols for Heterogeneous Wireless Networks; Multi-hop communications in integrated wireless networks; network selection; always best connectivity

Haldar, Kuheli LEfficient Quality of Service Provision Techniques in Next Generation Wireless Networks
PhD, University of Cincinnati, 2014, Engineering and Applied Science: Computer Science and Engineering
Recent evolution of communication networks comprises of different segments and technologies, where each segment maybe implemented using different QoS. Further, the proposed all-IP core infrastructure of the future networks will offer varying QoS level multimedia services to the users. However, IP being a best effort service, seamless provision of end-to-end QoS guarantees is extremely important. In today's world, devices with multiple networking capabilities is quite common. The traditional approach in networking includes grouping identical traffic and allocating them to the network that has the maximum available data rate. This creates unbalanced traffic load in the network, leading to poor utilization of the associated resources. This problem can be greatly alleviated if the traffic can be allocated intelligently to the networks. For fair traffic distribution, we modeled the AP of each network as a single queuing server. Then, suitable equations and algorithms are designed to divide the incoming traffic flow into multiple subflows and allocated to the APs based on their available data rates. Network Selection in a Heterogeneous Cognitive Radio Wireless Network is a challenging task, since the users need to select the appropriate channels of the network in addition to the network itself. The varying levels of interference experienced by the secondary user (SUs) is due to the presence of primary user (PU)s in the adjacent channels. Hence, SUs transmitting highly sensitive data must find a channel that is interference free. In this dissertation, we develop a novel network and channel selection scheme that categorizes both the user applications and the network channels depending on their sensitivity level for interference and select them using a bipartite graph matching algorithm. The effectiveness of Cognitive Radios is based on opportunistic access of the licensed channels by SUs while protecting the PU transmission. But channel sensing incurs cost in terms of time overhead and energy consumption. However, infrequent sensing also results in loss of transmission opportunity for the SUs. Hence, an interesting and challenging question arise: when should the SU sense the channel, sleep or transmit, to minimize the total cost? In this dissertation, we developed a novel scheme for deriving the optimal inter-sensing duration in a Cognitive Radio network, on the requirement of protecting the PUs' communications while minimizing the cost for the SUs. The scheme has been presented for both non-erroneous and erroneous channel sensing conditions. Handling the "mobile data tsunami" in the future and providing indoor coverage is a significant challenge for the operators. The answer is LTE femtocells. However, limited spectrum availability in the cellular networks causes severe interference in the neighboring femtocell users that are transmitting in the same radio band. In densely deployed environments, interference problems in co-channel femtocells causes significant degradation in performance. In this dissertation, we proposed a CASFR scheme, that assigns distinct set of PRBs to each interfering femtocells in the downlink. In the uplink we proposed a PSE algorithm to further reduce any interference that may remain after performing CASFR. Finally, the topics for future work have been clearly identified.

Committee:

Dharma Agrawal, D.Sc. (Committee Chair); Raj Bhatnagar, Ph.D. (Committee Member); Yizong Cheng, Ph.D. (Committee Member); Chia Han, Ph.D. (Committee Member); Yiming Hu, Ph.D. (Committee Member)

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks;Next Generation Wireless Networks;Cognitive Radio;Inter-cellular Interference;Femtocells;4G

Wang, XiaoyuanNetwork Selection and Rate Allocation in Heterogeneous Wireless Networks and Systems
MS, University of Cincinnati, 2009, Engineering : Computer Science

Heterogeneous wireless network (HWN) technology has emerged in the next generation mobile networks, which enables mobile client (MC) to simultaneously communicate with multiple heterogeneous access networks for better quality of services (QoS) and lower service cost. By the context of conventional network protocols, separately and independently operating network interfaces cannot fully utilize the potential of a HWN.

In this thesis, we model and analyze a HWN and system. The issues are identified as the multi-MAC management between MCs and access networks, and the multi-network (multi-NET) management between application servers and access networks. We propose a multi-MAC management scheme over multiple heterogeneous interface MACs to optimize multi-application performance with network selection and rate allocation for uplink traffic. We also propose a multi-NET management scheme for multi-user performance optimization in the downlink traffic, which is network-centric and distributes traffic into multiple access networks by supporting the inter-networking operations. Besides necessary optimization algorithms, procedures to implement our schemes are also provided.

Committee:

Dharma Agrawal, DSc (Committee Chair); Wen-Ben Jone, PhD (Committee Member); Chia-Yung Han, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks;Network Selection;Optimization;Rate Allocation

Oliveira, Talmai B.Dealing with Uncertainty and Conflicting Information in Heterogeneous Wireless Networks
PhD, University of Cincinnati, 2012, Engineering and Applied Science: Computer Science and Engineering

Inspired by challenges of multi-constraint path selection and the need for providing a desired QoS, this dissertation focuses on devising an efficient network selection algorithm that satisfies multiple user constraints with uncertainty in a heterogeneous wireless network (HWN), while under imprecise and dynamic network conditions. We start by determining the impact of the partial network knowledge on the optimal solution. We introduce a Dynamic Programming (DP) solution approach to the routing problem using a well established routing metric. We then compare the impact of using a more realistic scenario with stochastic metrics and formulate an approximate optimal strategy for routing between mobile devices (MD). A fuzzy logic model is then proposed which aims at translating the uncertainty of the network conditions to accurate values. We perform a thorough analysis of the metric values offered by various wireless technologies, and derive crisp values for imprecise network parameters. A sensitivity analysis is performed that reflects the performance and relative importance of the metrics on each network. These results are shown to impact user’s decision in handing data over to an appropriate interface.

While earlier works focused on multi-constrained routing or handover decision in a HWN, we consider dynamically changing network conditions. This is expected in a realistic deployment where a user is uncertain about what exactly is required under a given circumstance, indicates their preference in vague terms, and expects multiple deployments, with scenarios that are prone to failures, reliability strategies are considered in order to try to determine when to stop retransmitting a message in order to ensure proper delivery while still being energy efficient. A simple effective link-attribute estimator is presented that is capable of identifying the quality of communication between neighboring mobile devices while maintaining scalability. By relying on this link-quality estimator, a maximum number of attempts is computed which (probabilistically) ensures delivery while maintaining an energy-efficient network. Simulations show that our estimator maintains acceptable message delivery ratio while increasing the overall energy efficiency.

Finally, a study is made regarding dealing with conflicting information, and how devices can cope with data that may overlap or even conflict with each other through a localized protocol. Specifically, this dissertation looks at the impact of transient and permanent failures on the accuracy of decision making. The behavior of a wireless network is analyzed with respect to the detection of an event by increasing the number of failures. We compare four different schemes: simple majority between neighboring MDs, a more adaptive reputation-based protocol, fuzzy logic to quantify the MDs’ uncertainty and a combination of fuzzy logic and the Transferable Belief Model (TBM) framework. Through simulations, we show that our proposed TBM-based solution has the lowest number of incorrect decisions, even when used in deciding and detecting anomalies under an extremely large percentage of faulty MDs.

Committee:

Dharma Agrawal, DSc (Committee Chair); Kenneth Berman, PhD (Committee Member); Raj Bhatnagar, PhD (Committee Member); Chia Han, PhD (Committee Member); Mara Helmuth, DMA (Committee Member)

Subjects:

Computer Science

Keywords:

uncertainty; conflicting information; heterogeneous wireless networks; multiple user constraints; partial knowledge; reliability