蔡志宏臺灣大學:電信工程學研究所鄭凱元Cheng, Kai-YuenKai-YuenCheng2010-07-012018-07-052010-07-012018-07-052008U0001-2907200816045100http://ntur.lib.ntu.edu.tw//handle/246246/188236Due 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.n 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.Contenthapter 1 Introduction 1.1 Background ...………………………………………….………..... 1.2 Related works …………………………………….……………… 2.3 Motivation and research goal …………………………….……… 7hapter 2 Mathematical and theoretical framework for bandwidth estimation in IEEE 802.11n wireless LAN 92.1 An overview of IEEE 802.11n Draft …………………………… 9 2.1.1 The MAC function of IEEE 802.11n ….………………………….….. 92.1.2 The PHY function of IEEE 802.11n …………………………..……. 132.2 The corrected mathematical formula for the major methods of bandwidth estimation……………………………………………… 142.2.1 The corrected mathematical formula for the PPTD method……..…. 142.2.2 The corrected mathematical formula for the TTOP method …….…. 20.2.3 The bandwidth estimation in IEEE 802.11n wireless LAN ……..….. 25.2.4 The generic mathematical formulas of the PPTD / TTOP method for the wireless network………………………………………………… 32hapter 3 Measurement techniques for available bandwidth in wireless LANs ……………………………………………………………………. 35.1 Calculating the gaps of packet pairs for the PPTD method ..….... 35.2 Calculating the probing rate for the TTOP method …………….. 37.3 The analysis of the system internal time deviation……………... 39hapter 4 An adaptive rate control scheme using the bandwidth estimation for multimedia transmission in wireless LANs 47.1 The algorithm of adaptive rate control using bandwidth estimation ……………………………………………...………………….47.2 The implementation of rate control scheme on the streaming server and client ……………………………………………………….. 55hapter 5 Simulation and experiment result 57.1 Experiment of bandwidth estimation in IEEE 802.11 wireless LAN ………………………………………………………………... 57.1.1 The setup of experiment environment for bandwidth estimation ….…. 57.1.2 Experiment results of bandwidth estimation using the PPTD method … ……………………………………………………………………….63.1.3 Experiment results of bandwidth estimation using the TTOP method ……………………………………………………………………...…. 70.2 Experiment of the rate control scheme using bandwidth estimation in wireless LAN ………………………………………………… 765.2.1 The setup of experiment environment for the rate control scheme …….…. 76.2.2 Experiment results of adaptive rate control scheme using bandwidth estimation …………………………………………………………………..77 hapter 6 Conclusion 81.1 Conclusion ……………………………………………………… 81.2 Future work …..………………………………………….……... 83eferenceist of Figures.1 Gap incurred in the bottleneck link [11] ………..……………………. 4.2 Available bandwidth over measured bandwidth in TOPP for a single-hop path …………………………………………..…………... 6.1 A-MSDU frame structure [17] ……….…………………………….. 11.2 A-MPDU frame format [17] ………………..………………………. 12.3 Transmitting probe packets in 802.11 wireless LAN ………..……... 16.4 Transmitting probe packets in 802.11 wireless LAN (Simplified) .... 16.5 The proportion that the overhead of MAC/PHY layers occupies in the transmitting time of the probe packet/ACK pair in the 802.11 LAN ….……………………………………………………………………..19.6 The ratio D between sending rate Rs and receiving rate Rr. …...….... 22.7 The ratio D between sending rate Rs and receiving rate Rr …….…... 24.8 The ratio D between sending rate Rs and receiving rate Rr with different probe packet size and the cross traffic ………………...…. 25.9 The estimated available bandwidth by TTOP in IEEE 802.11g WLAN ………………………………...………………………………….… 25.10 The frame format with A-MSDU aggregation in IEEE 802,11n .….. 27.11 The estimated available bandwidth by PPTD with the capacity 144 Mbps (2 X 1 antenna array) of PHY layer in IEEE 802.11n WLAN ….…………………………………………………………………….... 28.12 The estimated available bandwidth by TTOP with the capacity 144 Mbps (2 X 1 antenna array) of PHY layer in IEEE 802.11n WLAN ….……………………………………………………………………… 29.13 The frame format without aggregation and fragment in IEEE 802,11n …………………………………………………………………... 30.14 The frame format with fragment in IEEE 802,11n …………….…... 31.1 The transmitting process of the probe packets sending from the sender to the receiver in PPTD measuring process ……...……………….. 41.2 The transmitting process of the probe packets sending from the sender to the receiver in TTOP measuring process .……………………….. 45.1 The network architecture of adaptive rate control scheme …...…….. 49.2 The relationship among the capacity, AvailableBW, and ReserveBW when there are the streaming flow and cross traffic flow in the transmission path …………………………………………………… 51.3 The complete flow chart of the adaptive rate control algorithm using the bandwidth estimation technique ………………………………... 54.4 The system architecture of the streaming server and client in the wireless LAN …………………………..…………………………… 55.1 The architecture of experiment environment for bandwidth estimation …………………………….…………………………….. 58.2 The measurement steps of PPTD method in the experiments …..….. 61.3 The measurement steps of TTOP method in the experiments …..….. 62.4 The estimated results of first experiment using the PPTD method…. 67.5 The diagram of setting the field “number of TX buffer” on the wireless network interface card on the client ………………………………... 68.6 The estimating results of second experiment using PPTD method ... 69.7 The estimating results of second experiment using PPTD method ... 70 .8 The plot of ratio which equals to sending rate divided by receiving rate V.S. Sending rate of probe packets ……………………………….… 72.9 The estimated values of available bandwidth using the TTOP method in first experiment ………………….....…………………….………. 74.10 The estimated results of second experiment using TTOP method ………………..…………………………………………..... 75.11 The estimated results of third experiment using TTOP method ……………….…………………………………………….. 76.12 The architecture of experiment environment for adaptive rate control scheme using bandwidth estimation ……………………………….. 78.13 The estimating results of adaptive rate control scheme using bandwidth estimation …………………………..…………………... 81ist of Tables.1 Address fields for unicast MPDU containing A-MSDU [17] …....… 12.2 The values of headers and frames in IEEE 802.11a …..……………. 19.1 The detailed specifications of all devices in the experiment environment ………………………………………………….……... 58.2 Key parameters of the cross traffic in the second experiment …….....60.3 Key parameters of the cross traffic in the third experiment ……..…. 63.4 The flow chart of rate control scheme in our experiment ………….. 79.1 The summaries of the PPTD and TTOP methods using Cisco Aironet 1250 series access point in the different wireless LAN ….…………. 83.2 The summaries of the PPTD and TTOP methods for the generic case in the different wireless LAN …………………………...….…………. 833532363 bytesapplication/pdfen-US頻寬估測傳輸速率調整bandwidth estimationrate controlthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/188236/1/ntu-97-R95942120-1.pdf