Through non-authorized network, UMA technology from traditional GSM cellular network or a local mobile phone and GPRS mobile services automatically switch to UMA access point, make the phone without interruption to detect the fastest and most economical network, which enables mobile phone users The most flexible way to access to advanced mobile services. UMA phone to leave after the coverage of access points, then seamlessly switch back to the cellular network. Figure 1 is a UMA network topology: In the UMA architecture, the existing cellular network and there is no adjustment, but in the network to introduce a new network components - UMA controller. The role of UNC equivalent of GSM / GPRS access network in the original base station controller, UMA network responsible for radio resource management and link management, in addition to UNC through IP network and mobile terminal to establish a connection end to end, and with the MSC / GPRS exchange information.
802.11a standard has now been approved, the use of spectrum in the 5GHz band 12, the signal stronger, 802.11b transmission speed is about five times. But while the 802.11a chip already on the market more than a year, now the network is still very small quantities. Another 802.11g still in development stage, has not yet permitted by standards bodies, but with better security, speed, and 802.11a is the same. WiFi Metro is the first U.S. network to provide two combined company. Prior to Orange County, California, with only two Baltimore police car was equipped with this feature. Police have adopted two Padcom software, when the patrol car parked near the police station, the police can directly log in 802.11 networks, but if it is out duty, then the switch provided by the Verizon wireless Internet services.