正交分頻多重擷取系統之無線資源管理

Abstract

本篇論文成功地將允入控制、封包排程、通道重新分配、功率指定、通道分配、功率控制及換手轉換等無線資源管理演算法給合在所建立的正交分頻多重擷取系統模擬平台上，並觀察不同的演算法對系統整體效能的影響。在無線資源管理方面，為了改善系統的效能，我們分別提出子通道重新分配及填充水位之功率指定法。由於通道會隨著時間改變，使用者從開始使用一直到結束為止，可能需要一段時間，所以在通道還未變動很激烈之前，就重新分配子通道來改善系統效能。傳統功率指定方式是維持所有的次載波為相同的連線品質，但這種簡單的方式需要比較高的功率消耗，填充水位之功率指定法就是為了克服傳統功率效率差的缺點。從電腦模擬所得到平均所需傳送功率、封包遺失率、系統運輸量及平均封包延遲等數據結果來顯示所提出的演算法都有較佳之效能。

A generic simulation platform for studying radio resource management (RRM) such as admission control, packet scheduling, sub-channel assignment and reassignment, power allocation, power control and handover is developed in this thesis for orthogonal frequency division multiple access (OFDMA) systems. New methods for sub-channel reassignment and water-filling for power allocation are proposed to improve system capacity. The purpose of sub-channel reassignment is to monitoring the channel in a way that the sub-channel that appears to be the best to a user can be reassigned to that user, and therefore the overall system capacity can be increased. On the issue of power allocation, on the other hand, the conventional approach is to maintain the same link quality for all sub-carriers. This simple scheme however requires high power consumption. To overcome this drawback, a water-filling based power allocation scheme is proposed. Numerical results show that both the proposed methods outperform the traditional ones in terms of averaged power consumption, packet loss rate, throughput and averaged packet delay.