The proposed paper presents a novel multimedia multiplexing protocol that enables the transmission of multimedia data over several wireless networks at the same time. The multiplexer system has been designed to be adaptive, maximizing the performance. Traffic control and congestion reactive techniques, based on channel parameter estimations, are provided. Data error protection mechanisms are illustrated and performance/efficiency issues are discussed using the simulation results. The frame structure of the protocol, the advantages, and the flexibility that can be provided to future wireless systems are highlighted. Additionally, the performance of multimedia multiplexing and transmission in noisy environments is presented and improvements compared with existing systems and the ITU H.223 standard, are highlighted.