For the ATM over WiMax sublayer, traffic of each ATM connection is conveyed by a single WiMax connection. The number of WiMax connections increases along with the ATM connections. Resource allocation overhead and computation complexity also increase as the number of WiMax connections increases. This study discusses the accommodation of multiple ATM connections in one WiMax connection while preserving the original convergence sublayer and packet header suppression characteristics. This paper proposes a multiplexing control scheme to minimize the transmission overhead. The proposed scheme also provides a re-synchronization mechanism after the occurrence of consecutive empty cells during multiplexing. The simulation results show that the proposed scheme has much lower overhead when comparing to the traditional round robin scheme.