Mobile Radio Transmission System -8.Wireless Packet Communication
Data communications by packet switching is a system that sends and receives information by dividing messages into small blocks called packets and adding headers containing address and control information to each packet. As this enables a common channel to simultaneously carry the communications of multiple users, channel usage efficiency is high and the costs can be held down.
"DoPa," which is DOCOMO's dedicated data communications service, offers connections to LAN and Internet service providers by applying this principle of packet switching to the wireless section as well. This makes it possible to realize excellent cost performance as the mobile packet communications system has a network configuration in which the packet communications function is added and integrated into PDC, which is the digital system for portable and automobile telephones.
PDC adopts three-channel TDMA as its wireless transmission system. Packet channels configured this way provide for a common-access system that can be shared by multiple mobile terminals on a random access basis. The ICMA-PE system, which has demonstrated superb performance in the PDC system control channel, has been adopted for random access control.
In order to further increase communicaton speed, multi-slot transmissions that simultaneously use three channels are now possible. The communications speed in this case is as high as 28.8 Kbps.
Network node for wireless packet communication