基于自适应帧长技术重传次数受限的SW-ARQ系统时延性能

Delay performance of SW-ARQ system with limited number of retransmission based on adaptive frame-size technique

考虑到实际通信中数据帧的重传次数受限,构建重传次数有限的自适应三模式SW-ARQ系统.系统中采用自适应帧长技术,根据连续收到的应答帧ACK或NAK的个数将信道噪声状况区分为低、高和很高3种状态,并考虑不同状态下发送不同帧长的数据帧,用发送相邻两帧间的时延τ和数据率R表示不同状态下发送一帧的等效时延,建立准确描述系统传输机制和原理的Markov模型及其稳态方程,求得用信道错误率表示的系统各状态的稳态概率和不同状态下分组发送次数的条件概率,进而求得准确的系统时延解析式.最后在MATLAB环境下对系统的时延性能进行仿真分析,结果表明该系统能够提供更小的服务时延,尤其是在信道错误率较大的环境中效果更为明显.

Taking into consideration that the number of retransmission of data frames was limited in actual communication, a adaptive three-mode SW-ARQ system with limited retransmission was built. The technique of adaptive frame-size was used in the system, the channel noise state was divided into low, high and very high ones according to the continually received ACK or NAK acknowledgement frames, and the data frames with different size were transmitted for different states. Their equivalent delay was expressed with the delay r between two adjacent frames and data transfer rate R. The Markov model and steady-state equation, with which the system transmission mechanism and principle could be precisely described, were set up, and it was obtained the steady-state probability expressed by channel error rate and conditional probability of transfer times of grouped packet in different conditions were obtained. And further, the more precise analytical expression of system delay was obtained, also. Finally, the delay performance of the system ARQ was simulated and analyzed with MATLAB, and the result showed that a smaller service delay would be provided with this system, especially in the case of higher channel error rate.