APPLYING ATM TO MOBILE INFRASTRUCTURE NETWORKS

In response to the explosive increase in the number of mobile subscrib ers and the ever stronger demand for mobile multimedia services, the a uthors propose introducing the ATM technique for next-generation mobil e network infrastructures in order to handle a high volume of traffic and develop multimedia communications. First, this article clarifies m obile-specific requirements for and advantages of applying ATM to mobi le 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 n etwork infrastructure to convert from conventional STM to ATM as mobil e 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 ve ry-low-bit-rate mobile voice streams is inefficient due to the delay i n 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 structu re enables the efficient transfer of voice signals ranging from very-l ow-bit-rate signals to high-speed multimedia signals with little delay . Standardization of this cell structure is progressing in ITU-T and t he ATM Forum. Transmission efficiency is estimated here by simulation.