WiMAX Performance Optimization Technique Based On Content Adaptation Approach

The growing demand on multimedia contents and the rapid development of small wireless devices equipped with Internet access have made Broadband Wireless Access (BWA) one of the important future trends. To meet the needs of the development of BWA and solve the problem of the"last mile"access, IEEE has elaborated 802.16 WMAN standards, namely WiMAX.WiMAX and its related technologies have become a focus of today's researches. Although WiMAX demonstrates quite a few advantages, such as high access bandwidth, high system capacity, QoS support, it is meeting huge challenges in terms of bandwidth and system capacity when more and more multimedia services occur in the network. This means WiMAX base stations have to operate under heavy traffic load and some of them even operate at full capacity. This will incur, in consequence, the network congestion and packet loss and affect the overall performance of WiMAX network. In this regard, how to improve the performance of WiMAX network and the efficiency of bandwidth usage has become an important topic to discuss.To answer this question, this dissertation has proposed a WiMAX Performance Optimization Model based on Content Adaptation Approach. This is an adaptive content delivery model which plays a role of performance optimization in WiMAX network. This model is intended for WiMAX network consisting mainly of devices with small screen size, and can be applied to image or video delivery. After doing some analysis and researches on content adaptation technique, we have proposed of applying content adaptation approach to WiMAX in order to obtain better network performance.To set up the model, we have defined an important parameter-User Satisfaction, based on which we set up the optimization problem within the key algorithm of the model. By solving the optimization problem mathematically, we have obtained the performance improvement index in two scenarios: best satisfaction and best performance. This result has proved theoretically the effectiveness of this model in terms of WiMAX network performance optimization.After the theoretic analysis of the model, we have validated the feasibility and the effectiveness of this model through network simulations. We used NS-2 and the WiMAX module provided by NIST as simulation tool, and carried out three simulation scenarios: content delivery without adaptation, best satisfaction scenario, and best performance scenario. We then compared and analyzed the simulation results of three performance metrics: throughput, packet loss, system capacity/request capacity. Finally, we come to the conclusion that the application of content adaptation technique is able to improve the overall performance of WiMAX network.The research work of this dissertation is in an early stage, and there still remain a few problems to solve. Future research work includes: 1. Analyze the performance improvement problem of the WiMAX network composed of several base stations; 2. Involve other types of networks into the system (such as 802.11) and discuss the content adaptation approach in heterogeneous networks; 3. Consider the content adaptation scenario when mobility and network handoff occurs; 4. Extend the types of the multimedia content supported in the model, such as audio and text.