In a Mobile Network, several constraints are used to deliver wireless data. For wireless, the handheld devices should be portable, have limited size and weight, which results in reduced memory capacity, less power CPU and reduced user interface. Wireless networks also have limited bandwidth, longer coverage and a degree of reliability. The wireless handheld devices can access Internet applications only if all these constraints are carefully addressed.
To address these constraints carefully, In June 1997, the Wireless Application Protocol (WAP) forum was founded. The development of this forum was important in wireless industry.
WAP forum has developed a set of wireless protocol specifications and offer these protocols to many industry groups. The result is that many mobile operators and handset manufacturers have joined the WAP-enabled devices. Before WAP-enabled devices, wireless data services were not successful. So, to improve wireless data market, WAP is introduced with limited computing and memory capacities, WAP allows a Web browser in handheld devices to access Internet.
WAP Architecture
WAP architecture consists of three operational units.
The WAP handset or handheld and origin server communicates with each other through Mobile Network. WAP handset received the contents and these contents are encoded in binary format of Wireless Markup Language (WML) for efficient transmission. A WAP Gateway, which is located between Internet/server and mobile/WAP handset, receives these contents and decodes them from binary format to text format. This text format is then forward to origin server. The origin server decides what to retrieve from the text format. The Uniform Resource Locator (URL) of the server specifies the files and these files are transferred to WAP Gateway through Hypertext Transfer Protocol (HTTP). The WAP Gateway encodes the HTTP header into WML byte code and then this result is transferred to WAP handset. A Hypertext Markup Language (HTML) filter is also located between origin server and WAP Gateway. It acts like a translator and translates the HTML format into Wireless Markup Language (WML) format, which is used in wireless applications.
WAP Models
For handset devices WAP defines a user-interface model. In WAP handset devices up and down scroll keys are used for navigation. For menu option selection and context-specific functions Soft Keys are used. Some examples of WAP phone models are following.
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Nokia 7110
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Ericsson R320
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Ericsson MC 218
GSM 900/1800 dual-band supports these models as well. These models are equipped with large display, micro browser, Voice memo, full graphics, calendars, contact manager and a complete Chinese interface.
WAP Protocols
WAP Protocols are defined in terms of WAP Protocol stack.
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Wireless Datagram Protocol (WDP)
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Wireless Transport Layer Security (WTLS)
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Wireless Transaction Protocol (WTP)
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Wireless Session Protocol (WSP)
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Wireless Application Environment (WAE)
1. Wireless Datagram Protocol (WDP): The WAP transport layer is defined by the WDP. To the upper-layer protocols of the WAP, the WDP offers consistent services and with it these layers can function independently of the underlying layers.
2. Wireless Transport Layer Security (WTLS): The WAP security layer is defined by the WTLS. By using encryption and decryption techniques, the WTLS provides unchanged and uncorrupted data integrity.
3. Wireless Transaction Protocol (WTP): The WAP transaction layer is defined by the WTP. WTP is similar to Transmission Control Protocol (TCP), which controls that traffic of data and also saves processing and memory costs in WAP handset. By using retransmission and acknowledgments techniques it provides reliability.
4. Wireless Session Protocol (WSP): The WAP session layer is defined by the WSP. WSP supports client and server for exchange of contents, by establishing a session from client to server and releases the session and saves the power of WAP handset, when it is idle.
5. Wireless Application Environment (WAE): The WAP application layer is defined by the WAE. To efficiently built applications it provides an environment for mobile operators. It also defines a set of formats, images, phone book records and calendar information.
Advantages of WAP
WAP Protocols are specially designed to reduce the amount of information, which is delivered through wireless network of limited bandwidth. To deliver the same information WAP uses 50 percent less packets as compare to HTTP/TCP.
