利用OFDMA做動態頻寬分配及多媒體訊號排程

Abstract

本篇論文主要探討如何提升802.16 OFDMA（Orthogonal Frequency Division Multiplexing Access）系統的傳輸效能。由於802.16提供了多種服務類型來配合多媒體資料中不同等級的即時性，因此我們會利用一個時間函數來標示資料的傳輸優先度，而此優先度和這個訊號的即時性及在緩衝區等待傳送的時間有關，並且設計了一套排程機制來規範多媒體資料的傳送順序，目標即為減少即時性資料的延遲。由於multi-cell的網路架構中，使用者會受到鄰近基地台的干擾，也就是所謂的CCI（Co-Channel Interference）。而CCI會造成使用者的SINR降低，傳輸效能也隨CCI的增加而降低。因此本論文探討利用FFR（Fractional Frequency Reuse）來降低CCI，以提升SINR（Signal to Interference plus Noise Ratio），進而增加傳輸量並且減少即時性資料的延遲。同時也探討使用STBC來降低訊號錯誤率，以提升實質SINR，減少資料延遲。最後我們將探討多媒體資料在802.16動態競爭訊框中傳輸基底，並且比較上述兩種提高傳輸量的方法對於減少即時性資料延遲的特性。

This thesis is focused on how to improve the transmission performance on 802.16 OFDMA systems. There are several service types that can be chose for the different real-time of multimedia communications on 802.16 systems. Therefore we use a time-function to mark the priority of the packet. Moreover, the priority is depended on real-time from the QoS of data and waiting-time with data in the queue. And we design a scheduling algorithm to manage multimedia communications for reducing delay of real-time data. Since the multi-cell structure of wireless networks systems will bring CCI (co-channel interference), it will decrease the user’s SINR (Signal to interference plus noise ratio). Therefore we analyze the FFR (fractional frequency reuse) for decrease CCI and increase SINR. Moreover, the delay of real-time data also will be decreased. At the same time, we will be discussing the use of STBC to decrease SER (symbol error rate), which will significantly improve effective and decrease delay of real-time data. Finally, we will analyze the dynamical competition with transmission slot and compare these methods for decreasing the real-time data.