A method of DCF (Distributed Coordination Function) optimizationStop 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.