Abstract:It is significant to explore the Multi-access(MAC) protocol of HF due to the poor bandwidth of HF. In this study，the protocol of Multi-access for 3G-Automatic Link Establishment(ALE) was researched. Then based on OPNET Modeler, the networks model, node model and process model of the 3G-High Frequency(HF) were designed. The process of automatic link establishment was simulated. Simulations for successful ratio of link establishment were executed under different conditions. The results show that the Bit Error Rate(BER) has the most important effect on the ratio，while the number of channels and network nodes are following, and the traffic of nodes has the least impact.