Most wireless applications consist of a user wishing to communicate with a server at some
remote location. The user's terminal is connected to the wireless network via a radio link to a base station. The server is connected to a network, be it the Internet or some corporate
Intranet. Now, each base station is connected to something called a serving node. The terminology differs depending on which mobile network you look at, but the idea is almost always the same. Note that one serving node can be attached to several base stations. On the
other side of the diagram we have the network attached to some gateway. Finally, tying the
pieces together we have the backbone network to which both the gateway and the serving
node are connected. Note that the backbone can be connected to several serving nodes and
several gateways. Using this network a wireless user can communicate with a remote server.
Other things are also attached to the network backbone. For example, there is some kind of
subscription register to store information on the mobile users. There is also some operations
and maintenance equipment to allow network monitoring, charging etc.