高密度IEEE 802.11ac網路使用多點協調技術的下行傳輸資源配置

Abstract

IEEE 802.11ac是一個針對無線區域網路服務的標準，隨著人們對於網路需求的提高，它提出了有效的解決方式，並且持續在持續制定中。此標準不只使Wi-Fi系統在6 GHz以下頻段朝向非常高吞吐量(VHT)的操作。隨著更高的資料傳輸速率在實體層中支持和新採用的下行鏈路多使用者多輸入多輸出機制在標準中，一個非常高吞吐量的存取點可以改善區域網路系統的效能。我們藉由在3GPP LTE-A標準下之共同合作(CoMP)傳輸的概念提出了兩個不同模式的合作傳輸機制:聯合傳送(JP)和協調排程/協調指向(CS/CB)，嘗試在一個充非常高吞吐量同操作頻道的存取點的環境中減少重疊基本服務區的環境。同時透過合作群的概念，將三個存取點視為一個虛擬大的存取點，在與傳統的IEEE 802.11媒介存取控制協定之下，我們提出了三種不同模式的通道探聽程序以及使用者排程演算法，藉此提高CoMP傳輸機制的效能。透過NS-3模擬軟體的模擬結果中顯示，將CoMP機制中的CS/CB導入IEEE802.11ac中可提高至少一倍的平均吞吐量，其中JP的效能又高於CS/CB一倍以上，並且在我們所提的資源配置演算法下，可再增加約11%~13%的吞吐量。因此，合作式傳輸機制可以在一個有許多非常高吞吐量的重疊基本服務區網路帶來相當大的優點。

The ongoing Wireless Local Area Network (WLAN) IEEE 802.11ac standard proposed an effective solution to meet people’s internet needs. This standard enhances Wi-Fi system toward very high throughput (VHT) operation in bands below 6 GHz. With the supports of higher data rate in PHY layer and a newly adopted downlink multi-user multiple-input and multiple-output (DL MU-MIMO) scheme optional in the standard, a VHT AP could improve WLAN system performance. In this thesis, we borrow the concepts of coordinated multi-point transmission (CoMP) from 3GPP LTE-Advanced standard to propose two classes of CoMP transmission schemes, named Joint Processing (JP) and Coordinated Scheduling/Coordinated Beamforming (CS/CB) to mitigate the overlapping BSS (OBSS) scenario in a VHT WLAN environment where VHT APs operate on the same channel. More than that the concepts of clustering containing three APs can be regarded as a virtual AP. These proposed schemes are being compatible with legacy IEEE 802.11 MAC protocol. In addition, we proposed the resource allocation algorithm to enhance the performance of CoMP transmission. Through the result of network simulator-3, CS/CB transmission in VHT WLAN environment increase nearly twice the throughput. The performance of JP is more than twice of CS/CB. Furthermore, CoMP user scheduling algorithm can further increase throughput about 11% to 13%. Therefore, CoMP transmission and resource allocation algorithm bring considerable advantages in the overlapping BSS (OBSS) scenario in the VHT WLAN environment.