Directional Cell Breathing - A Framework for Congestion Control and Load Balancing in Broadband Wireless Networks
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Despite the tremendous bandwidth increase in 3rd generation (3G) Broadband Wireless Networks (BWNs) such as Universal Mobile Telecommunication System (UMTS), maintaining the mobile users’ Quality of Service (QoS) requirements while maximizing the network operators’ revenues is still a challenging issue. Moreover, spatial distribution of network traffic has a negative impact on the overall network performance where network resources are overutilized in parts of the network coverage area while such resources are underutilized in other network coverage areas. Therefore, network congestion and traffic imbalance become inevitable. Hence, efficient Radio Resource Management (RRM) techniques which release congestion and balance network traffic are of utmost need for the success of such wireless cellular systems. Congestion control and load balancing in BWNs are, however, challenging tasks due to the complexity of these systems and the multiple dimensions that need to be taken into consideration. Examples of such issues include the diverse QoS requirements of the supported multimedia services, the interference level in the system, which vary the mobile users and base stations allocated transmission powers and transmission rates to guarantee certain QoS levels during the lifetime of mobile users connections. In this thesis, we address the problem of congestion control and load balancing in BWNs and propose efficient network coverage adaptation solution in order to deal with these issues, and hence enhance the QoS support in these systems. Specifically, we propose a directional coverage adaptation framework for BWNs. The framework is designed to dynamically vary the coverage level of network cells to release system congestion and balance traffic load by forcing mobile users handoff from a loaded cell to its nearby lightly loaded cell. The framework consists of three related components, namely directional coverage adaptation module, congestion control and load balancing protocol, and QoS provisioning module. These components interact with each other to release system congestion, balance network load, maximize network resource utilization, while maintaining the required QoS parameters for individual mobile users.