Research On Dynamic Resource Allocation Schemes For IEEE 802.16e-based Cooperative Networks

To satisfy the demand for broadband wireless access, IEEE established 802.16 WG (Work Group) to develop the standard for Wireless Metropolitan Area Networks, i.e., WiMAX (Worldwide Interoperability for Microwave Access), which includes a fixed version (802.16d) and a mobile version (802.16e). The main problem is that high data rates can not cover all the areas if traditional cellular networking architecture is adopted. Especially, the low quality of the received signal in the boundary of a cell results in low throughput and unfairness among users in the throughput; Cooperative diversity is a new diversity method that can conquer the effect of multi-path in mobile communication systems. It can realize cooperation among users with single antenna, and make users share antenna each other to perform virtual MIMO (Multiple Input Multiple Outputs) arrays, and benefit from spatial diversity. Cooperative diversity can increase the capacity of the system significantly. In this thesis, we studied how to integrate the cooperative diversity to 802.16e networks to improve the performance and fairness of broadband wireless access system.There are mainly two contributions in the thesis. Firstly, we proposed an 802.16e-based cooperative network model. To make the operation of proposed network efficient, we further designed a new OFMDA frame structure based on the existing 802.16e OFDMA/TDD frame structure. Another contribution is that we proposed dynamic resource allocation schemes and algorithms for the IEEE 802.16e-based cooperative network. The resource allocations include cooperation partner selection and OFMDA subcarrier allocation. We select cooperation partner node according to SNR (Signal to Noise Ratio) between users and SNR between BS (Base Station) and user. Users are divided into two groups: set of cooperation users and set of non-cooperation users through partner selection. The proposed algorithm for OFMDA subcarrier allocation is implemented on every subframes, and assigns subcarriers to users based on channel state of subcarriers. We allocate the subcarriers to the users who have the best SNR on this subcarrier. Therefore, the overall capacity of the system is maximized.In the end, we evaluated and analyzed the proposed the network model and resource allocation algorithms through simulation. The overall research work and the related performance analysis showed that our proposed IEEE 802.16e-based cooperative network model, OFDMA frame structure and its resource allocation scheme can integrate the cooperative diversity technique into traditional 802.16e network efficiently, and can improve not only the overall capacity of the system significantly but also the fairness among users.