In response to the explosive increase in the number of mobile subscribers and the ever stronger demand for mobile multimedia services, the authors propose introducing the ATM technique for next-generation mobile network infrastructures in order to handle a high volume of traffic and develop multimedia communications. First, this article clarifies mobile-specific requirements for and advantages of applying ATM to mobile infrastructure networks. However, it is risky for network operators en bloc to replace the conventional STM-based infrastructure by ATM. Therefore, this article shows a smooth evolution path for the mobile network infrastructure to convert from conventional STM to ATM as mobile multimedia services mature. Even in future mobile networks, the main traffic may still be voice communications, whose bit rate is too low for efficient use of the radio frequency band. Applying ATM to such very-low-bit-rate mobile voice streams is inefficient due to the delay in filling out the payload of an ATM cell; this "packetization delay" degrades the quality of service. This problem can be solved by using a layered cell structure for the mobile ATM network. This cell structure enables the efficient transfer of voice signals ranging from very-low-bit-rate signals to high-speed multimedia signals with little delay. Standardization of this cell structure is progressing in ITU-T and the ATM Forum. Transmission efficiency is estimated here by simulation.
