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基于TCP反馈的主动队列管理算法会无差别地丢弃UDP分组,导致视频质量下降.根据TCP/UDP发送特性和混合流排队机制,推导拥塞窗口、丢弃概率及混合流队列长度的微分方程,通过线性化获得Ad Hoc网络混合流AQM(active queue management)控制模型,提出了一种减少UDP丢弃率的PI-V主动队列管理算法.当视频画质下降时,算法依据视频帧权重与分组长度,动态地调整UDP视频流的丢弃概率.NS(network simulator)仿真表明,PI-V算法优于PI与去尾算法,提高了视频传输质量0.82 d B~2.22 d B的峰值信噪比(PSNR).
The active queue management algorithm based on TCP feedback discards UDP packets without distinction, resulting in the degradation of video quality.According to TCP / UDP transmission characteristics and hybrid flow queuing mechanism, the differential window of congestion window, drop probability and hybrid queue length are deduced, We get a control model of active queue management (AQM) for Ad Hoc networks and propose a PI-V active queue management algorithm to reduce the UDP discard rate.When video quality declines, the algorithm bases on the weight of video frames and packet length, dynamic , The probability of discarding UDP video stream is adjusted.NS (network simulator) simulation shows that the PI-V algorithm outperforms the PI and the tail-end algorithm, and improves the PSNR of the video transmission quality from 0.82 d B to 2.22 d B.