| Summary: | 碩士 === 崑山科技大學 === 電子工程研究所 === 94 === Wireless networks are inherently nonlinear, uncertain, and dynamic. To realize quality of service (QoS) for IEEE 802.11e wireless ad-hoc networks, we adopt fuzzy feedback control which is widely used in dealing with nonlieararity and uncertainties. Via the cross-layer interface, the fuzzy controller at the MAC receives the Traffic Specifications (TSPEC) from upper protocol layers as the reference input, and performs control to the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) function. Dynamically adaptating the Contention Window (CW) parameters, traffics’ control systems real-time aquire adequate bandwidths according to their respective traffic classes.
We regard the wireless network as the control plant and model its behavior with the Generalized Fuzzy Automata (GFA). Anzlyaing the GFA model, we design the membership functions of the premise parts in the rule base. Moreover, we design the algorithm that the upper layers adapt the conclusion parts according to network dynamics. That is upper layers also regards the MAC layer as its plant to achieve Hierarchical Cross-Layer Control (HCLC). Therefore, the HCLC controller possesses properties of objective (non-empirical), adaptive, and with cross-layer interface, which is not common in traditional fuzzy controllers.
We implement the MAC layer fuzzy controller with the Field Programmable Gate Array (FPGA). Through, implementation in host computer software is easy, the host CPU load increases due to necessity of computation for each packet transmission. Moreover, since porting of system software and modification of original MAC driver are also required the portability and reusability are reduced. After, minimization according to the characteristics of wireless networks, the controller achieve small area, high speed, and low power objectives. Finally, we integrate the FPGA prototype with the network simulator, NS2, and accomplish system level simulation and verification. From the experiments, the proposed network communication fuzzy controller distributed in wireless stations real-time allocate bandwidths for traffics that provides very food functionality, convenience, and reusability for the SoC integration.
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