針對空間多工在行動WiMAX之無線資源管理之研究

Abstract

隨著使用者對於高速無線資料傳輸的需求增加，行動 WiMAX 系統不僅僅能滿足此需求並且已經成為未來3.5代、第4代行動通訊系統的候選人之一。但是在多媒體應用的持續發展下，高傳輸速率、高頻寬的無線通訊服務已經是必需的條件，因此多輸出多輸入 (MIMO)、智慧型天線 (AAS) 勢必會成為下一代行動通訊開發的基本技術。在本論文中，將針對在有智慧型天線的支援並且使用空間多工(SDMA)的情況下，對於離基地台較遠或是傳輸通道情況較差的使用者能否給予一定程度上的傳輸服務品質保證進而增加系統使用者容量與涵蓋範圍。更進一步地，我們同時也考慮了在即時與非即時混和式服務下的傳輸品質要求。因此我們發展了一個行動WiMAX模擬平台，並且建立了包含基礎無線資源管理以及可以支援智慧型天線運作的MAC層。在我們的模擬當中，我們套用了一個簡單的兩階層式排程演算法，在滿足使用者傳輸品質要求的前提下，有效的分配無線傳輸資源。根據模擬數據的分析，我們可以得知，在有智慧型天線以及空間多工的支援以及不增加傳輸功率的情況下下，能夠有效地減少同頻干擾進而提升傳輸品質及系統的使用者容量。即使在系統所有基地台都使用同一頻率的情況下，系統效能也有顯著的改善。

The mobile WiMAX based on IEEE 802.16e standard which provides high speed transmission over large area has been adopted as one of the candidates of next generation communication systems. But, with higher demand of multi-media application, high date rates and high bandwidth are necessary for wireless transmission. Consequently, the Multiple Input Multiple Output (MIMO) and Adaptive Antenna System (AAS) will be the solutions of future wireless system. In this thesis, we apply Spatial Division Multiple Access (SDMA) mechanism enabled by AAS on mobile WiMAX to investigate the system level performance analysis when poor RF condition users are served with beamforming. Besides support poor users, we also consider the Quality of Service (QoS) requirements of mixed traffic services. As a result, we build a simulation platform for mobile WiMAX with basic Radio Resource Management (RRM) and SDMA-enabled MAC layer. We adopt a simple two stages scheduling algorithm for QoS guarantee and SINR enhancement for poor users. In the simulation result, the cell capacity can be increase significantly because of the reduction of outage probability. With beamforming, the co-channel interference is suppressed and SINR is enhanced under the same power budget so that the transmission quality is promoted. The simulation results also shows that when two stage scheduling algorithm for SDMA is applied, the system performance is still improved significantly under serious co-channel interference.