Tham khảo tài liệu 'wireless mesh networks part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Trends and Challenges for Quality of Service and Quality of Experience for Wireless Mesh Networks 139 The simulation experiments comprised 3 VoIP Voice over IP calls that on simulations are characterized by two flows . 6 UDP flows 5 TCP-Reno flows and 3 video traffic. The video traffics were evaluated from the experience that the user obtained through the QoE evaluation metric. The UDP flows have a bit rate of 8Kb s and 40 bytes RTP UDP Payload of packet size in order to represent the codec Balam Gibson 2007 . The TCP flows were characterized as FTP applications following the Pareto model with a rate of 200k 210 bytes of packet size and 500 ms burst duration. Flow Source Destiny Begin End Traffic 1 1 8 10 40 TCP - Reno 2 9 2 11 41 TCP Reno 3 7 4 12 42 TCP Reno 4 5 0 13 43 TCP Reno 5 6 4 14 44 TCP Reno 6 0 5 10 45 Video Paris 7 3 6 14 29 Video Foreman 8 3 6 30 45 Video News 9 2 9 6 46 UDP - CBR 10 9 2 6 46 UDP - CBR 11 1 8 7 47 UDP - CBR 12 8 1 7 47 UDP - CBR 13 4 7 8 48 UDP - CBR 14 7 4 8 48 UDP - CBR Table 3. Flow Configuration The video traffic was simulated through the Evalvid tool Evalvid 2010 that allows the control of the video quality in a simulation environment. Well-know real videos sequences were used namely Paris Foreman and News . These videos have frames in YUV format which are compressed by MPEG-4 codec and sent at a rate of 30 frame s. Each frame was fragmented into blocks of 1024 bytes where the packet has a size of 1052 bytes. Well-know objective and subjective QoE metrics are used in the experiments following the tests proposed by ITU-R ITU-R 1995 . The subjective QoE metrics evaluate the quality of multimedia applications based on the receiver s opinion where the MOS was used. The videos were analyzed using the MSU Video Quality Measurement Tool Software MSU 2010 . The value of PSNR is expressed in dB decibels . For a video to be considered with good quality it should have an average PSNR of at least 30dB. The following tables and .
