A variety of networks are available for mobile communications. But which communications architectures that make the most sense? There are two fundamental ones to look at. One we call a traditional communications architecture. The other we refer to as a mobile communications architecture, an architecture more well-suited for handheld computers and wireless networks.

Traditional Communications Architecture

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In this architecture, a remote computer establishes a dial-up connection to a network. See Figure 7. By going through a remote-access server (RAS), the remote computer can function as a network client with complete access to services such as e-mail and databases. The RAS server functions as a router, allowing standard networking protocols such as TCP/IP to extend from the remote computer to services on the corporate network.

Mobile Communications Architecture
Whereas a traditional communications architecture can be used by handheld computers, there are some issues to consider. One is that client software is not necessarily available for the platform of interest. Another issue is that compared to wireline networks, today's wireless networks operate at lower speeds, have greater latencies and do not always support standard networking protocols. A different approach is required, namely to use an intermediate server that we refer to as a mobile server or a mobile gateway. See Figure 8.

The gateway can perform a variety of functions. One is to use protocols optimized for wireless networks, such as WAP, to communicate with mobile devices, while using standard networking protocols to communicate with back-end services. Another is to format information for the smaller screen sizes of a mobile device.

An interesting question is about the location of the gateway because there are a number of possibilities. In some cases, the wireless carrier themselves will operate the gateway. This is the case today for AT&T's smartphone, the PocketNet. Alternatively, an organization could deploy their own gateway as part of a wireless-middleware solution. Finally, there are third-party organizations beginning to specialize in this kind of service. See the Services section for a list of such providers.

Note that there are security implications of this new architecture. Since the gateway acts as a proxy for the mobile user, the corporate network may need to authenticate the gateway in addition to the mobile system. In certain instances the gateway will communicate with corporate systems across the Internet, in which case, secure tunnels using VPN protocols may need to be employed.