針對可靠的高畫質視訊傳輸的適應性技術

Abstract

重傳對於無線傳輸高畫質電視串流是很重要的，特別是強調於控制每個Video Frame抵達的時間，避免延遲超過上限造成畫面無法即時解碼。論文主要是對於即時高畫質電視傳輸提出一個MAC層系統架構及演算法。我們不僅考慮了單一天線終端到終端的無線傳輸，也考慮了多天線終端到終端的無線傳輸和多使用者多天線的無線傳輸。儘管文獻已廣泛探討過最佳化Throughput的過程，但是對Throughput變化量的研究則相對缺乏。我們考慮了平均的Throughput及Throughput的標準差，來用以保證每個Video Frame能夠即時的到達接收端。為了達到上述目的，此數學方法用來最小化每個Video Frame所需的傳輸時間，利用調整modulation coding scheme (MCS)以及每個封包的長度來滿足嚴謹的frame error rate條件。每個Video Frame所需的傳輸時間定義為能夠將一個Video Frame完全傳送到接收端(包含重傳)且滿足錯誤率條件的最小時間。modulation coding scheme以及每個封包的長度可以根據即時的SNR和每個Video Frame的大小做動態的調整，MCS的選擇及封包長度的計算可完全被MAC層所決定用來做即時高畫質電視的無線傳輸。模擬結果顯示出我們提出了一個快速可靠的方法對求出傳送video frame所需的時間，這些發現對於系統商建置無線傳輸即時高畫質電視系統有很大的啟發。

Retransmission is necessary for the transmission of high-definition (HD) video streaming. It is essential to control the arrival time of each frame before the deadline. In this thesis, we present system architecture and a related algorithm for real-time HD video transmission. The research focuses on not only single antenna end-to-end wireless transmission but also consider MIMO (Multi input multi output) end-to-end wireless transmission and MU-MIMO (Multi-user MIMO) wireless transmission. While the process of throughput optimization has been extensively investigated, the variation of throughput is relatively unexplored. The average and variation of throughput are considered together to guarantee the transmission of each frame. For this purpose, the mathematical framework of this algorithm minimizes the required transmission time under the strict frame error constraint by adjusting payload length of each packet and modulation coding scheme. The required transmission time is defined as a minimal period in which the transmission could be completed and makes the error constraint satisfied. The parameters, payload length and modulation coding scheme, can be adapted dynamically based on instant signal-to-noise ratio and the data size of a video frame. This calculation can be completed punctually in the MAC layer for the HD video transmission. The simulation result shows that our proposed methodology can provide a quick, reliable way to calculate the delay bound before transmission. These finding have implications for operator developing a reliable wireless real-time HD video system.