802.11ac網路下行鏈路多使用者多輸入多輸出科技之研究

Abstract

IEEE 802.11ac是一個持續制定中的無線區域網路標準，它加強了Wi-Fi系統在6 GHz以下頻段朝向非常高吞吐量的操作。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擷取點可以改善區域網路系統的效能。在本篇論文中，我們藉由在LTE-A標準下之共同合作傳輸的概念提出了兩個種類的合作傳輸機制: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擷取點的環境中減輕重疊基本服務區的情境。這些提出的機制延伸至一個簡單的多使用者多輸入輸出機制[10]，而且與傳統的IEEE 802.11媒介存取控制協定兼容。此外我們在考慮的環境下也提供了一個找出共同傳輸對的演算法，並且透過模擬找出最大可合作傳輸之距離。我們在多使用者多輸入輸出和提出的共同傳輸機制之間做吞吐量評估，仿真模擬的結果顯示JP機制的效能優於CS/CB和多使用者多輸入輸出機制。因此，JP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好處。

The ongoing Wireless Local Area Network (WLAN) IEEE 802.11ac 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 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. These proposed schemes are extending from a simple DL MU-MIMO scheme [10] and being compatible with legacy IEEE 802.11 MAC protocol. Also we propose an algorithm which finds CoMP transmission pairs in considered network topology, and find out the maximum CoMP transmission distance through simulations. We make throughput evaluations between DL MU-MIMO and our proposed CoMP transmission schemes where simulation results indicate that the performance of JP outperforms those of CS/CB and DL MU-MIMO. Thus the JP scheme can bring benefits in a network with many VHT OBSSs.