3G网络下视频传输自适应控制的研究

Video transmission adaptive control research over 3G

介绍了一种应用在应急通信设备的3G视频通话系统。不同应用环境的3G,网络的带宽时变快慢以及链路误码大小变化较大,对此提出了一种自适应传输控制策略,以达到在不同网络环境都能有较高的带宽占用和较好的拥塞控制。本文以丢包率,往返延迟和时延抖动为依据将网络细分为为4种状态,并分别做相应的码率调节。为避免高误码引起的不必要的码率降低,利用累计抖动区分丢包。并通过对网络判断参数做加权预测,对不同质量网络应用不同码率上调条件,来减少码率的抖动。实验证明,此系统在不通环境中,均能较好地运行,达到较高的带宽占用。

This paper introduces a 3G video phone system used in emergency communication equipment . Because the bandwidth varying speed and link error rate of the 3G network change in different environment, an adaptive transmission control strategy is proposed to achieve higher bandwidth utilization rate and well congestion control in different network environment . Based on the packet loss rate, round-trip-time （RTT） and delay jitter the network is divided into four kind of states, and codec rate adjusts according to current network state. To avoid unnecessary code rate decreasing caused by high error , the cumulative jitter is used to distinguish the packet loss .For reduce rate jitter, calculate loss rate and RTT with a weighted prediction algorithm, and differ rate raising conditions in different quality network .Experiments show that this system can run well and achieve high bandwidth usage in each environments.