無線區域網路環境多媒體影音串流服務效能監測之研究

近年來，隨著IEEE 802.11 無線區域網路技術不斷創新與成熟，在無線區域網路上之各式應用推陳出新，因此無線區域網路之管理也愈來愈重要。無線區域網路之網路架構、通訊方式以及頻寬等特性，皆有別於傳統有線網路。無線區域網路所能提供頻寬有限，訊號與服務品質亦容易受到距離、障礙物、與其它微電波及頻道的干擾，所提供的連線服務容易因訊號不佳，造成客戶端連線品質不穩定。因此，如何有效監測無線區域網路之服務品質，無疑是無線區域網路效能管理重要之研究議題。本論文提出一個無線區域網路環境多媒體影音串流服務效能監測之機制，此機制利用無線區域網路基地台支援的SNMP網管功能，提供網管人員針對基地台通訊範圍內的客戶端，收集各項流量統計資料以及即時監控無線區域網路相關訊務統計網管資訊，藉此分析客戶端使用無線上網時的傳輸速度、訊號強度、連線品質等資料。藉由所提之效能監測機制，本論文將深入探討在無線區域網路環境多媒體影音串流服務特殊的壞蘋果現象，並針對播放器設定、UDP與TCP傳輸模式、以及基地台設定對多媒體影音串流服務品質之影響，以期望在無線區域網路提供優質的多媒體影音串流服務。

關鍵字

無線區域網路；多媒體影音串流；服務品質； SNMP ；壞蘋果；網路管理

並列摘要

Due to the advance of IEEE 802.11 wireless LANs (WLANs) in the recent years, various applications appear in WLANs. Thus, how to effectively manage WLANs is an important issue. There exist inherent differences between WLANs and wired LANs in network infrastructure, signal transmission, and bandwidth resource. The bandwidth offered by WLANs is shared and limited. The quality of wireless transmission service is subject to distance, obstacles, and interference. That is why many WLAN users suffer instable wireless QoS. Therefore, How to effectively monitor the QoS of a WLAN is an important issue for performance management of WLANs. In this thesis, we shall propose a performance monitoring scheme for multimedia streaming services over WLANs. Based on the inherent SNMP support in WLAN access points (APs), the proposed scheme provides traffic statistics per client and gathers traffic performance data of the managed WLAN. Thus, the network manager can realize the speed, signal strength, signal quality of each wireless association. With the aid of the proposed monitoring scheme, we shall also investigate the bad apple phenomenon found when there are multimedia streaming services over WLANs. We shall discuss possible factors affecting the performance of WLAN multimedia streaming services, including media player settings, TCP/UDP transmission, and AP configurations. It is expected that better QoS can be achieved for multimedia streaming services over WLANs.