A Framework for Radio Resource Management in Heterogeneous Wireless Networks
Taha, Abd-Elhamid Mohamed Abd-Elhamid
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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.