Understanding the Wireless Application Protocol (WAP) in Mobile Computing

WAP, short for Wireless Application Protocol, was developed by the WAP forum, an organization founded by companies like Ericsson, Motorola, and Nokia. It’s an open standard designed to provide wireless phones, pagers, tablets, and other mobile devices with access to information services, including telephony, internet, and web applications.

Let’s explore the WAP protocol stack, programming model, infrastructure, and applications within the context of mobile computing.

WAP Protocol Stack

WAP is designed to work seamlessly with various wireless technologies, such as GSM and CDMA. It’s built upon existing internet standards like IP, XML, HTTP, and HTML. Figure 1 illustrates the WAP protocol stack. WAP specifications are developed to address the following:

• Adherence to the WWW programming model.
• Use of languages like WML based on XML.
• Lightweight protocol stack for efficiency.
• Wireless telephony application framework.
• Browsers tailored for wireless terminals or mobiles.

WAP Programming Model

WAP programming model

Figure 2 highlights the three core elements of the WAP programming model: the client, the gateway, and the origin server. HTTP is used to transfer content between the server and the gateway.

The gateway acts as a proxy server for the wireless network. It performs protocol conversion between WAP and WWW content. To achieve this, it houses both WAP and WWW protocol stacks. It also provides DNS services.

WAP Infrastructure

WAP infrastructure

Figure 3 shows the key components used in a WAP network.

Let’s examine how a mobile user browses web content while connected to an ordinary web server:

• The web server provides HTML-coded pages using web protocols like HTTP/TCP-IP.
• The HTML content is converted to WML formats using an HTML filter device located with the WAP proxy.
• The WAP proxy converts the WML content into a more compact, binary WML format suitable for small wireless devices such as tablets, palmtops, and mobile phones.

If the mobile device is directly connected to a WML-compliant server, the WML content is carried using HTTP/TCP-IP protocols to the WAP proxy. The WAP proxy then converts it into the binary WML format, which is delivered to the wireless devices using wireless networks such as 2G, 3G, etc.

WML - Wireless Markup Language

WML is a language developed to describe content and format it for presentation on devices with limited screen size, bandwidth, and user input capabilities.