IEEE802.16鏈結調整演算法之設計

Abstract

隨著科技的進步, 多媒體應用所需的傳輸速率愈來愈高。為了滿足各種多媒體應用的品質,通訊系統必須能夠動態調整傳輸速率。我們使用鏈結調整機制來訂定各種傳輸速率改變的依據。本篇論文的主旨在設計WiMAX 系統的鏈結調整機制。WiMAX 系統在burst profile 中設定多種編碼和調變的組合來提供各種傳輸的需求。我們以封包錯誤率的限制為基礎設計其鏈結調整機制。 論文首先介紹WiMAX 系統之實體層架構以及模擬WiMAX 系統封包錯誤率之參數。我們使用二段式曲線擬合近似此模擬之結果。接著,我們使用Lagrangian 方法設計鏈結調整機制。透過此設計, 我們可以找到切換burst profile的SNR 門檻值。同時, 我們更設計了使用自動重傳請求(ARQ) 和混合式自動重傳請求(HARQ) 的鏈結調整機制。我們發現使用重傳機制確實可將切換burst profile的SNR門檻值降低,進而有效提昇throughput。

As technology evolves, the development of multimedia applications demands high speed transmission. To satisfy various quality of services for multimedia applications, communication systems must dynamically adjust the transmission rate. Link adaptation is applied to determine the transmission rate. The motivation of this thesis is to design link adaptation algorithm for WiMAX systems. WiMAX support various coding and modulation settings in different burst profiles that provide defferent transmission rates. We design the link adaptation algorithm to maximize the average throughput under the constraint of packet error rate threshold. In this thesis, we first introduce the physical layer of WiMAX system and the setup for WiMAX packet error rate simulation. We use double curve fitting to approximate the result of simulation. We can find the optimal SNR thresholds that maximize the average throughput. We also design the link adapatation for WiMAX with ARQ or HARQ. The resulting SNR thresholds of switching burst profiles are decreased which increase the average throughput.