WAP protocol in mobile computing
WAP is the short form of Wireless Application Protocol. It is developed by WAP forum which was established by companies which include Erisson, Motorola and Nokia. It is the open standard developed to provide wireless phones, pagers, tablets and other mobile devices access for information services. The services include telephony, internet and web applications. Let us explore wap protocol stack, WAP programming model, WAP infrastructure and wap application in mobile computing.
WAP is designed to interoperate and work with all the wireless technologies such as GSM, CDMA etc. It is developed based on existing internet standards viz. IP, XML, HTTP, HTML etc.
Figure-1 diagram depicts WAP protocol stack. WAP specifications are developed to take care of following:
• Follows WWW programming model.
• Language such as WML as per XML.
• Lightweight stack
• Wireless telephony application framework.
• Browser suitable fo wireless terminal or mobile.
WAP Programming Model
Figure-2 mentions three basic elements of WAP programming model. It includes client, gateway and original server. HTTP is used to transfer the connects between server and gateway. Gateway acts as proxy server for the wireless part. It acts as protocol converter between WAP contents and WWW contents. It houses both WAP and WWW protocol stacks to do this. It also provides DNS services.
WAP Infrastructure
Figure-3 depicts key components used in WAP network.
Let us examine how mobile user browse web contents while connected on ordinary web server.
• As shown web server provides HTML coded pages using web protocols such as HTTP/TCP-IP.
• The HTML contents are converted to WML formats using HTML filter device co-located with WAP proxy.
• The WAP proxy converts WML contents to more compact binary WML contents suitable for small wireless devices such as
tablet, palmtop and mobile subscribers.
If the mobile device is directly connected with WML compliant server than the WML contents are carried using HTTP/TCP-Ip protocols
first to the WAP proxy.
The WAP proxy converts the same into binary WML formats which is delivered to the wireless devices using wireless networks such as 2G, 3G etc.
WML-Wireless Markup Language
WML language is developed to describe content as well as format for presenting data on devices with limited screen size, bandwidth and user input capabilities.