WAP and WML
One of the most important aspects of wireless communications is standardization. In 1997, the Wireless Application Protocol (WAP) was developed by dominant cell-phone manufacturers Nokia, Ericsson, Motorola and others to facilitate the introduction and standardization of wireless Internet access. WAP is a set of communications protocols that are designed to enable wireless devices to access the Internet. WAP applications can be used on Palm OS, Windows CE, Mac OS and Java 2 Micro Edition devices.
Although WAP communications involve many components, we focus on three—a
WAP-enabled mobile device, a WAP gateway and a Web server. When a user of a WAP-enabled device requests information from the Internet, the device sends the request to a WAP gateway. WAP gateways serve as links between mobile devices and the Internet. WAP gateways are designed to convert Web content from WML to HTTP, which is the standard protocol used to transfer and view information in Web transactions. The WAP gateway communicates with the Web server (i.e., the server that has a connection to the Internet). The Web server processes the mobile-device request by searching through existing databases and information resources, such as Web pages. The Web server then transmits the requested information back to the WAP gateway, using HTTP. The gateway translates the information into WML and sends it to the mobile device for use.
The Wireless Markup Language (WML), which is based on XML, is the markup lan-guage used to create Web content delivered to wireless handheld devices. WML tags are the markup commands that specify how a Web page should be formatted for viewing on a wire-less device. Microbrowsers, browsers designed with limited bandwidth and memory requirements, can access the Web via the wireless Internet. WAP supports WML to deliver the content.
A WML document is called a deck; each contains one or more pages, called cards. Cards are renderable units of WML documents useful for WAP clients (a WAP client being any WAP-enabled device) that generally use the devices with limited screen sizes. Each card can contain both text content and navigational controls to facilitate user interaction. Though only one card can be viewed at a time, navigation between cards is rapid, because the entire deck is stored by the microbrowser.
Although WAP and WML provide many advantages, they also have many opponents. Those who favor WAP technology see it as a short-term solution for the delivery of wire-less Internet access. WAP opponents cite various disadvantages that are associated with the protocol, including possible security breaches, limited bandwidth and unreliability.
The limited bandwidth capabilities of WAP-enabled devices cause a host of problems. Not only are WAP-enabled devices unable to handle the transmission of multimedia, but they can also become overloaded during peak hours, the busiest hours of the day for con-ducting wireless communications.23 This limitation causes business-to-business (B2B) and business-to-consumer (B2C) application developers to anticipate the release of faster 3G technologies and a new WAP specification that supports increased functionality.
When learning about mobile communications, it is vital to understand the process by which mobile devices connect to and interact with the Internet, because this process is orga-nized differently for each protocol and programming language. However, no protocol cur-rently existing allows a wireless device to communicate directly with the Internet. Each system (i.e., WAP and WML, i-mode and Java and J2ME) employs its own method of sending and receiving information to and from the Internet.
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