802.11n媒體存取控制層之效能分析與研究

最新一代無線區域網路標準:802.11n，帶來了重大的技術挑戰。由於透過多天線支援多頻寬，符合802.11n標準的WLAN元件也必須在輸出功率、尺寸大小等方面進行最佳化。對於設計802.11n無線電電路的工程師而言，需要考量的因素包括整合性、功率、性能、濾波、隔離和吞吐量。無線網路的一個關鍵設計和部署原則就是監視、控制和指配功能的集中化。實驗證明，集中化是對大量網路設備制訂和實施統一政策的最佳方式，無論這些設備集中於同一實體地點還是分散在不同的地理區域。一個集中式無線網路架構要想有成效，相關的資訊必須不斷地傳送給管理該網路的中心設備(如無線網路交換機/設備)。如果沒有整體、精確及更新速度達到毫秒級的無線環境狀態資訊，中心設備就無法做出準確的決策。與此同時，如果中心控制器參與所有的接取點作業，它可能會影響那些對時序特別感應的功能。因此，必須在其中尋求一種平衡。 MAC提供兩種傳送服務:分散式協調功能使用CSMA/CA，適合傳輸非即時資訊。集中式協調功能由網路協調者掌控並且以輪詢的方式安排工作站傳送訊框的時機及順序。由於工作站傳送的時間可事先安排，因此可提供保証傳送延遲的服務。訊框連結是裡面必要也是關鍵的技術，所謂訊框連結就是將很多小的封包結合成為一個大封包，因此本來需要經過很多次MAC控制封包交換的步驟，現在只要一次就可以將大量的資料傳送過去，所以MAC的overhead 可以被降低而傳輸效率就可以提升了。訊框連結可以在MAC層做，在接收端只要根據檔頭的資料，利用對應的方式將收到的大封包拆開成原來的小封包。

關鍵字

訊框連結；多媒體存取控制層

並列摘要

The latest generation of wireless LAN standards: 802.11n, a major technical challenges. With the participation of the multi-antenna multi-bandwidth, in line with the 802.11n standard WLAN components must also be in the output power, size and other aspects of optimization. The 802.11n wireless circuit design engineers, to consider factors such as integrity, power, performance, filtering, isolation and throughput. Wireless network design and deployment of a key principle is to monitor, control and centralization of assigned functions. The experiments show that concentration of a large number of network equipment development and implementation of the harmonization of policies the best way, whether they focus on the same physical equipment location or scattered in different geographical regions. A centralized wireless network architecture in order to be effective, relevant information must be continuously transmitted to the central management of the network equipment (such as the wireless network switches / equipment). If there is no overall, precision and update rate of millisecond-level status information of the wireless environment, the center equipment will not be able to make accurate decisions. At the same time, if the central controller in all of the access point operation, which may affect the timing of those on the function of special sensors. Therefore, we must find a balance in which. MAC transmission offers two services: a distribution coordination function using CSMA / CA, non-real-time information for transmission. Coordination function controlled by the network coordinator and a way to polling station to send the time frame and sequence. Transmission as a result of the workstation can be pre-arranged time, the transmission delay can provide a guarantee of service. Frame aggregation is the key to the necessary technology, the so-called Frame aggregation is combined with many small packets into a big packet, it would have to go through many times of packet-switching MAC control steps, and now can be as long as a large number of data of the past, so the MAC can be reduced overhead transmission efficiency can be improved. Link frame can be done in the MAC layer, as long as the receiving end in accordance with header information, using the corresponding methods will receive a large packet of the small opening into the original packet.

並列關鍵字

802.11n ； frame aggregation

參考文獻

[2] Seungbeom Lee and Sin-Chong Park, “Rotating Priority Queue based Scheduling Algorithm for IEEE 802.11n WLAN” ICACT., vol 3, pp. 1702-1706, Feb. 2007.

[3] Josip Lorincz and Dinko Begusic, “Physical layer analysis of emerging IEEE 802.11n WLAN standard” ICACT., vol1, pp.-194, Feb. 2006.

[4] David Tung Chong Wong, Mangalam Ramakrishnan Shajan and Ying-Chang Liang and Francois Po Shin Chin” Performance Analysis of Cooperative MAC in IEEE 802.11n for Multiclass Traffic” VETECF pp., 205-209 Sep. 2007.

[5] Roger Pierre and Fabris Hoefel “IEEE 802.11n MAC Improvements: A MAC and PHY Cross-Layer Model to Estimate the Throughput” IEEE VTC’08, pp., 1-5. Sep. 2008

[6] D. Skordoulis, Qlang Ni, H.H. CHEN, Adrian P. Stephens, C.G. LIU and Abbas Jamalipour “IEEE 802.11n MAC frame aggregation mechanisms for next-generation high-throughput WLANs” IEEE Wireless Communications, Feb. 2008.

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802.11n媒體存取控制層之效能分析與研究

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