在無線區域網路中使用頻寬估測技術設計多媒體速率調整控制機制

Abstract

Due to the trend of applying the multimedia service through the wireless environment, IEEE 802.11n, the next generation WLAN technology, is proposed by IEEE 802.11n Task Group (TGn). To improve the throughput efficiency, the 802.11n MAC layer has employed the frame aggregation mechanisms, which has a different behavior on the frame transmission, when compared with the existing WLAN IEEE 802.11 a/ b/ g standards. In this thesis, we improve the bandwidth estimation techniques proposed previously by other researchers to adapt the different wireless LANs. The proposed framework and algorithm has three main features. The first is predicting the actual available bandwidth observed from the upper layer application accurately. The available bandwidth observed from the upper layer will be various according to the different packet sizes of applications. The second feature is predicting the available bandwidth correctly even when the frame aggregation mechanism is activated in the IEEE 802.11n wireless LAN. The latest is to predict the available bandwidth fast and correctly when there exists cross traffic flows in the transmission environment. Finally, we propose an adaptive rate control scheme using bandwidth estimation to adjust the transmission rate of real-time multimedia applications. We setup an experiment environment and verify that the transmission rate of real-time multimedia applications can be adjusted appropriately to avoid the network congestion. By using the adaptive rate control scheme, the quality of multimedia applications can be maintained at a good level.