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Most existing multicast protocols adopt a static retransmission scheme (unicastor multicast) to retransmit lost packets. In the mobile multicast environment, static multicast re-transmission mode may lead to congestion in the receivers’ wireless interfaces, while static unicastmode may result in great network load. Both static unicast and multicast retransmission modeswill cause a performance loss. This paper logically divides the mobile multicast network into fixedand mobile parts, and focuses on the mobile part. Then this paper analyzes the retransmissioncosts when multicast or unicast mode is chosen. Two main parameters are used to compare theirefficiencies: the average air-interface utilization of each receiver and the average network load.Based on the results of analysis, two new algorithms, called NLPA (Network Load Priority Algo-rithm) and AUPA (Air-interface Utilization Priority Algorithm) are presented. Finally, simulationresults conclude that, with proper parameters, both NLPA and AUPA can dynamically altatebetween unicast and multicast retransmission modes according to the conditions of network andreceiver, and avoid congestion in receivers’ wireless interfaces as well as great network load, witha better use of network and terminal resources.