Study On Scheduling Algorithm With QoS For The Ultra High Throughput Wlan

The research subject of this thesis is supported by the National Science and Technology Major Project (No.2012ZX03004005-003), which is named as Study on International Standardization and Technology Validation for Ultra High Throughput Wireless Local Area Network (UHT-WLAN). The UHT-WLAN can provide high data rate services with diverse quality of service (QoS) requirements through the system-level enhancements of physical layer transmission and media access control (MAC). A study on QoS-based scheduling algorithm for the UHT-WLAN is considered in this thesis, focusing on the frame length optimization and the resource allocation. A frame length optimization algorithm is proposed to guarantee delay-bound violation probability constraints, while a joint user scheduling and power allocation scheme is designed under overloaded scenarios.This thesis includes five chapters, organized as follows.Chapter 1 introduces the background and significance of this thesis, along with the chapter arrangement.Chapter 2 introduces the involved theories and methods for the frame length optimization and resource allocation research. First, a brief description of MAC-layer function components and physical layer frame structure for the UHT-WLAN is given, before an introduction of its traffic category with different QoS parameters. Second, an overview of wireless resource management is presented, including the optimization theory and the link-layer channel modeling method. Finally, a cross-layer scheduling scheme for the UHT-WLAN is described, compared with several classic scheduling algorithms.In Chapter 3, a frame length optimization algorithm for downlink is proposed based on delay-bound violation probability constraints. First, the link-layer models called effective bandwidth (EB) and effective capacity (EC) are applied to statistically characterize the source traffic pattern and the channel service dynamics. Second, the sufficient conditions of delay-bound violation probability constraints are derived by link-layer modeling method. Then the frame length optimization problem with delay-bound violation probability constraints is formulated for single-user MIMO systems and multi-user MIMO systems respectively. With the assumption of block-fading Rayleigh channels, the optimal frame lengths are calculated by numerical iterative methods. Last, the delay-QoS performance of the proposed algorithm is evaluated with respect to traffic source parameters, QoS requirements and the received signal-to-noise ratio. Theoretical analyses and simulation results show that the given delay-bound violation probability constraints are well satisfied with the optimal frame length.In Chapter 4, a joint user scheduling and power allocation scheme is presented with delay-bound violation probability constraints. First, precoding matrices are designed to cancel multi-user interference for MIMO systems under overloaded scenarios. Second, the user access control and the total transmit power restrictions are analyzed, before a weighted value is introduced to denote the level of user’s QoS satisfaction. And then the delay-bound violation probability constraint is converted into minimum data rate constraint by using EB and EC models. Thus the joint user scheduling and power allocation problem is formulated into combination optimization problem with multiple related constraints, aiming to maximize the system weighted throughput. Last, steps of searching for the optimal user selection and the corresponding power allocation are presented by Lagrange multiplier method.Chapter 5 summarizes this thesis and gives an outlook on further research.