A method of DCF (Distributed Coordination Function) optimization-Stop and Wait DCF integrated with the rate control and its performance analysis model are proposed in order to increase the effective throughput.SNR (Signal to Noise Ratio) thresholds of rate control are determined by tuning the BER (Bit Error Rate) of frame with the help of AMC (Adaptive Modulation and Coding) technology. When the SNR is below the lowest threshold, the DCF backoff process stops and waits till the channel SNR becomes big enough again. Therefore the transmission error could be decreased.Meanwhile, the access collision could be reduced either. Since the channel time, collision probability and frame error rate are changed differently as tuning BER,maximized throughput can be get at the tradeoff point of these parameters. The analysis and simulation indicate that the proposed model is accurate. The problem without packet loss differentiation is overcome and the cross layer optimization is implemented.%针对IEEE 802.11的DCF(Distributed Coordination Function)效率较低的问题,提出了一种结合速率控制的 改进方案——停等DCF及其性能分析模型.速率控制使用自适应调制编码技术给出了可调节业务BER(Bit Error Rate)的SNR(Signal to Noise Ratio)门限确定算法;设置暂停信道接入的最低SNR门限,可减少传输错误,并降低接入冲突;调节BER,可在信道时间、冲突概率和误帧率间达到优化折中,使系统吞吐率最大.分析和仿真说明了模式是准确的,停等DCF有效地克服了DCF缺乏丢包区分机制的问题,实现了跨层的性能优化.
展开▼
