Abstract: In order to minimize the oscillations of sending rate for multimedia streaming, Smooth Transmission Control Protocol（STCP） is proposed. The receiver of STCP detects packets loss online. When there are some packets lost, the receiver estimates the capacity of the link between sender and receiver by the loss rate and sending rate currently. The sender uses the estimated capacity to adjust the sending smoothly. If there is no packet lost, the sending rate will increase by emulating “additive increase” of TCP. Instead of cutting sending rate half when loss occurs, STCP decreases it according to the loss rate, which can guarantee the smoothness. Simulation results show that STCP has smooth sending rate and little delay jitter, and it has fine TCP-friendliness as well. STCP can be used for transmitting multimedia streaming.

Key words: transmission control, streaming media, smoothness, TCP-friendliness

摘要： 为减小传输流媒体业务时的速率抖动，提出一种平滑传输控制协议（Smooth Transmission Control Protocol）。该协议的速率控制主要在接收端实现：接收端不断检测丢包，如果发生丢包，就通过丢包率和当前的发送速率估算端到端的实际传输能力，依据纯属能力减小发送速率；如果没有发生丢包，则模拟TCP的和式增加策略以提高发送速率。使用丢失率降低发送速率，避免了TCP中积式减小的过激行为，减小了速率抖动，获得平滑的发送速率。仿真实验表明，STCP发送速率平滑，时延抖动小，具有TCP友好性，适用于流媒体的传输控制。

关键词: 传输控制, 流媒体, 平滑性, TCP友好性