Introduction to Wireless Application Protocol

WAP has become the de facto global industry standard for providing data to wireless hand-held mobile devices [4 � 10] . WAP takes a client/server approach and incorporates
a relatively simple microbrowser into the mobile phone, requiring only limited resources
on mobile phones. WAP puts the intelligence in the WAP Gateways while adding just
a microbrowser to the mobile phones themselves. Microbrowser-based services and
applications reside temporarily on servers, not permanently in phones. The WAP is aimed
at turning mass-market phones into a network-based smart phone. The philosophy behind
WAP�s approach is to use as few resources as possible on the hand-held device and compensate for the constraints of the device by enriching the functionality of the network.
WAP specifi es a thin-client microbrowser using a new standard called wireless markup
language ( WML ) that is optimized for wireless hand-held mobile devices. WML is a stripped down version of HTML.

WAP specifies a proxy server that acts as a gateway between the wireless network and the wire line Internet, providing protocol translation and optimizing data transfer for the wireless handset. WAP also specifies a computer-telephony integration application programming interface ( API ), called wireless telephony application interface ( WTAI ), between data and voice. This enables applications to take full advantage of the fact that this wireless mobile device is most often a phone and a mobile user�s constant companion. On-board memory on a WAP phone can be used for off-line content, enhanced address books, bookmarks, and text input methods.

The importance of WAP can be found in the fact that it provides an evolutionary path for application developers and network operators to offer their services on different network
types, bearers, and terminal capabilities. The design of the WAP standard separates the
application elements from the bearer being used. This helps in the migration of some
applications from short message service (SMS) or circuit-switched (CS) data to general
packet radio service (GPRS), for example. WAP 1.0 was optimized for early WAP-phones.

The WAP cascading style sheet (WAP CSS) is the mobile version of a cascading style sheet. It is a subset of CSS2 (the cascading style sheet language of the WWW) plus some
WAP-specific extensions. CSS2 features and properties that are not useful for mobile Internet applications are not included in WAP CSS. WAP CSS is the companion of XHTML Mobile Profi le (XHTML MP). Both of them are defined in the WAP 2.0 specification, which was created by the WAP forum. XHTML MP is a subset of XHTML, which is the combination of HTML and XML. There are many WAP 2.0-enabled cell phones on the market currently. Before creating WAP 2.0, developers used WML to build WAP sites and HTML/XHTML/CSS to build web sites. Now with WAP 2.0 they can make use of the same technologies to create both web sites and WAP sites. Documents written in XHTML MP/WAP CSS are viewable on ordinary PC web browsers, since XHTML MP and WAP CSS are just the subsets of XHTML and CSS.

The following are the goals of WAP:
? Independent of wireless network standards;

? Interoperability: Terminals from different manufacturers must be able to communicate with services in the mobile network;

? Adaptation to bounds of wireless networks: Low bandwidth, high latency, less connection stability;

? Adaptation to bounds of wireless devices: Small display, limited input facilities, limited memory and CPU, limited battery power;

? Efficient: Provide quality of service (QoS) suitable to the behavior and characteristics of the mobile world;

? Reliable: Provide a consistent and predictable platform for deploying services;

? Secure: Enable services to be extended over potentially unprotected mobile networks while preserving the integrity of data;

? Applications scale across transport options;

? Applications scale across device types;

? Extensible over time to new networks and transport. WAP is envisaged as a comprehensive and scalable protocol designed for use with:

? Any mobile device from those with a one-line display to a smart phone;

? Any existing or planned wireless service such as the SMS, CS data, unstructured
supplementary services data (USSD) and GPRS;

? Any mobile network standard such as code division multiple access (CDMA), global system of mobile communications (GSM), or universal mobile telephone system (UMTS); WAP has been designed to work with all cellular standards and is supported by major worldwide wireless leaders such as AT & T wireless and NTT DoCoMo;

? Multiple input terminals such as keypads, keyboards, touch-screens, etc.

Source of Information : Elsevier Wireless Networking Complete 2010