Abstract: Most of existing multicast congestion control mechanisms transmit multimedia services by simulating TCP windows mechanism.Although these mechanisms are friendly to TCP flows，the sending rate fluctuates sharply，which can not satisfy the demands that multimedia flow needs smooth transmitting rate and stable bandwidth.Based on fuzzy control theory，a multicast rate adjusting algorithm（FC-MRAA） is proposed for smoothness and TCP-friendliness.In the new algorithm，two fuzzy controllers are designed，one of which calculates the control parameter based on the feedback information from multicast receivers to keep TCP-friendly，and the other one computes the control gain to adjust sending rate further for smoothness based on the possession of router buffer.Simulation results show that the new algorithm has well smoothness and TCP-friendliness.

摘要： 目前多数组播拥塞控制机制采用模拟TCP窗口机制传输流媒体业务，尽管保证了TCP友好性，但是速率不够平滑，不能很好地满足流媒体组播业务服务质量的要求。针对这一问题，提出了一种模糊控制的组播速率调节算法（FC-MRAA）。该算法基于模糊控制理论设计了两个模糊控制器，一个根据接收端的反馈信息计算速率增量，保证TCP友好性；另一个根据路由器缓冲区占有率计算控制增益，平滑发送速率。仿真结果表明，该算法具有良好的速率平滑性和TCP友好性。