What is WAP?

WAP (Wireless Application Protocol) is a protocol stack designed in 1998-2001 to view small pages (decks) on mobile terminals. The constraints of mobile terminals include small display and limited user input facilities, narrowband network connection and limited memory and computational resources.

The most of Internet-capable mobile phones support WAP stack version 1.3. The specification defines a protocol for the connection of mobile terminals with Internet. This protocol (WTP/WSP) is based on UDP and it is adapted for narrowband connections. In particular, the most of HTTP-headers and XML-tokens are compressed into the binary form. The conversion between WTP/WSP and HTTP protocols is performed by a WAP gateway.

Besides the network protocol, the WAP Forum designed a markup language to write content for mobile phones. WML (Wireless Markup Language) is an XML language, it includes some HTML tags, but it also contains tags specific for mobile devices. The WML file (or deck) consists of several cards. Each card contains text, images, input fields, etc. To view WML-pages, the mobile phone must be equipped by a WML-browser.

The current version of WAP is 2.0. The WAP 2.0 specification allows mobile devices to access Internet directly (without WAP gateway). Since the connection bandwidth of modern bearers (EDGE or 3G) much exceeds the bandwidth of traditional GPRS or CSD bearers, direct access to the Internet becomes more and more popular.

The markup language of WAP 2.0 is XHTML Mobile Profile 1.0 which is a subset of XHTML and may be viewed by an ordinary web browser. The most mobile browsers supporting XHTML may also view simple HTML documents.