Abstract:
WAP is an open specification that offers a standard method to access
Internet based content and services from wireless devices such as mobile
phones. The WAP model is very similar to the traditional desktop
Internet. The independent nature of WAP has proved to be a breath of
fresh air for an industry riddled with multiple proprietary standards
that have suffocated the new
wave of mobile-Internet communications. WAP is an enabling technology that willbridge the gap between the mobile world and the Internet, bringing sophisticated solutions to mobile users, independent of the user and network. Backed by 75 percent of the companies behind the world's mobile telephone market and the huge development potential of WAP, the future for WAP looks bright Introduction The Wireless Application Protocol (WAP) is a hot topic that has been widely hyped in the mobile industry and outside of it. WAP is simply a protocol- a standardized way that a mobile phone talks to a server installed in the mobile phone network. WAP is hot for several reasons:
• It provides a standardized way of linking the Internet to mobile phones, thereby linking two of the hottest industries anywhere. • Its founder members include the major wireless vendors of Nokia, Ericsson and Motorola, plus a newcomer Phone.com. • Mobile information services, a key application for WAP, have not been as successful as many network operators expected. WAP is seen as a way to rectify this situation. 1. Motivation WAP is positioned at the convergence of two rapidly evolving network technologies, wireless data and the Internet. The explosive growth of the Internet has fuelled the creation of new and exciting information services. Most of the technology developed for the Internet has been designed for desktop and larger computers and medium to high bandwidth, generally reliable data networks. Mass-market, hand-held wireless devices present a more constrained computing environment compared to desktop computers. Because of fundamental limitations of power and form-factor, mass-market handheld devices tend to have: •Less powerful CPUs, •Less memory (ROM and RAM), •Restricted power consumption, •Smaller displays, and •Different input devices (eg, a phone keypad). Similarly, wireless data networks present a more constrained communication environment compared to wired networks. Because of fundamental limitations of power, available spectrum, and mobility, wireless data networks tend to have: •Less bandwidth, •More latency, •Less connection stability, and •Less predictable availability. Mobile networks are growing in complexity and the cost of all aspects for provisioning of more value added services is increasing. In order to meet the requirements of mobile network operators, solutions must be: •Interoperable – terminals from different manufacturers communicate with services in the mobile network; •Scaleable – mobile network operators are able to scale services to customer needs; •Efficient – provides quality of service suited to the behaviour and characteristics of the mobile network; •Reliable – provides a consistent and predictable platform for deploying services; and •Secure – enables services to be extended over potentially unprotected mobile networks while still preserving the integrity of user data; protects the devices and services from security problems such as denial of service. 2. The WAP Model The WAP programming model (Figure 2) is similar to the WWW programming model. This provides several benefits to the application developer community, including a familiar programming model, a proven architecture,and the ability to leverage existing tools (eg, Web servers, XML tools, etc.). Optimisations and extensions have been made in order to match the characteristics of the wireless environment. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology. WAP defines a set of standard components that enable communication between mobile terminals and network servers, including: •Standard naming model – WWW-standard URLs are used to identify WAP content on origin servers. WWW-standard URIs are used to identify local resources in a device, eg call control functions. •Content typing – All WAP content is given a specific type consistent with WWW typing. This allows WAP user agents to correctly process the content based on its type. •Standard content formats – WAP content formats are based on WWW technology and include display markup, calendar information, electronic business card objects, images and scripting language. •Standard communication protocols – WAP communication protocols enable the communication of browserrequests from the mobile terminal to the network web server. The WAP content types and protocols have been optimised for mass market, hand-held wireless devices. WAP utilises proxy technology to connect between the wireless domain and the WWW. The WAP proxy typically is comprised of the following functionality: •Protocol Gateway – The protocol gateway translates requests from the WAP protocol stack (WSP, WTP, WTLS, and WDP) to the WWW protocol stack (HTTP and TCP/IP). •Content Encoders and Decoders – The content encoders translate WAP content into compact encoded formats to reduce the size of data over the network. 3. Example WAP Network In the example, the WAP client communicates with two servers in the wireless network : • The WAP proxy translates WAP requests to WWW requests thereby allowing the WAP client to submit requests to the web server. The proxy also encodes the responses from the web server into the compact binary format understood by the client. If the web server provides WAP content (e.g., WML), the WAP proxy retrieves it directly from the web server. However, if the web server provides WWW content (such as HTML), a filter is used to translate the WWW content into WAP content. • The Wireless Telephony Application (WTA) server is an example origin or gateway server that responds to requests from the WAP client directly. The WTA server is used to provide WAP access to features of the wireless network provider’s telecommunications infrastructure. 4. Components of the WAP Architecture The WAP architecture provides a scaleable and extensible environment for application development for mobile communication devices. This is achieved through a layered design of the entire protocol stack (Figure 4). Each of the layers of the architecture is accessible by the layers above, as well as by other services and applications. The WAP layered architecture enables other services and applications to utilise the features of the WAP stack through a set of well-defined interfaces. External applications may access the session, transaction, security and transport layers directly. The following sections provide a description of the various elements of the protocol stack architecture. 5.1. Wireless Application Environment (WAE) The Wireless Application Environment (WAE) is a general-purpose application environment based on a combination of World Wide Web (WWW) and Mobile Telephony technologies. The primary objective of the WAE effort is to establish an interoperable environment that will allow operators and service providers to build applications and services that can reach a wide variety of different wireless platforms in an efficient and useful manner. WAE includes a micro-browser environment containing the following functionality: •Wireless Markup Language (WML) – a lightweight markup language, similar to HTML, but optimised for use in hand-held mobile terminals; •WMLScript – a lightweight scripting language, similar to JavaScript™; •Wireless Telephony Application (WTA, WTAI) – telephony services and programming interfaces; and •Content Formats – a set of well-defined data formats, including images, phone book records and calendar information. 5.2. Wireless Session Protocol (WSP) The Wireless Session Protocol (WSP) provides the application layer of WAP with a consistent interface for two session services. The first is a connection-oriented service that operates above the transaction layer protocol WTP. The second is a connectionless service that operates above a secure or non-secure datagram service (WDP). The Wireless Session Protocols currently consist of services suited for browsing applications (WSP/B). WSP/B provides the following functionality: •HTTP/1.1 functionality and semantics in a compact over-the-air encoding, •Long-lived session state, •Session suspend and resume with session migration, •A common facility for reliable and unreliable data push, and •Protocol feature negotiation. The protocols in the WSP family are optimised for low-bandwidth bearer networks with relatively long latency. WSP/B is designed to allow a WAP proxy to connect a WSP/B client to a standard HTTP server. 5.3. Wireless Transaction Protocol (WTP) The Wireless Transaction Protocol (WTP) runs on top of a datagram service and provides as a light-weight transaction-oriented protocol that is suitable for implementation in “thin” clients (mobile stations). WTP operates efficiently over secure or non-secure wireless datagram networks and provides the following features: •Three classes of transaction service: •Unreliable one-way requests, •Reliable one-way requests, and •Reliable two-way request-reply transactions; •Optional user-to-user reliability - WTP user triggers the confirmation of each received message; •Optional out-of-band data on acknowledgements; •PDU concatenation and delayed acknowledgement to reduce the number of messages sent; and •Asynchronous transactions. 5.4. Wireless Transport Layer Security (WTLS) WTLS is a security protocol based upon the industry-standard Transport Layer Security (TLS) protocol, formerly known as Secure Sockets Layer (SSL). WTLS is intended for use with the WAP transport protocols and has been optimised for use over narrow-band communication channels. WTLS provides the following features: •Data integrity – WTLS contains facilities to ensure that data sent between the terminal and an application server is unchanged and uncorrupted. •Privacy – WTLS contains facilities to ensures that data transmitted between the terminal and an application server is private and cannot be understood by any intermediate parties that may have intercepted the data stream. •Authentication – WTLS contains facilities to establish the authenticity of the terminal and application server. •Denial-of-service protection – WTLS contains facilities for detecting and rejecting data that is replayed or not successfully verified. WTLS makes many typical denial-of-service attacks harder to accomplish and protects the upper protocol layers. WTLS may also be used for secure communication between terminals, eg, for authentication of electronic business card exchange. Applications are able to selectively enable or disable WTLS features depending on their security requirements and the characteristics of the underlying network (eg, privacy may be disabled on networks already providing this service at a lower layer). 5.5. Wireless Datagram Protocol (WDP) The Transport layer protocol in the WAP architecture is referred to as the Wireless Datagram Protocol (WDP). The WDP layer operates above the data capable bearer services supported by the various network types. As a general transport service, WDP offers a consistent service to the upper layer protocols of WAP and communicate transparently over one of the available bearer services. Since the WDP protocols provide a common interface to the upper layer protocols the Security, Session and Application layers are able to function independently of the underlying wireless network. This is accomplished by adapting the transport layer to specific features of the underlying bearer. By keeping the transport layer interface and the basic features consistent, global interoperability can be achieved using mediating gateways. 5.6. Bearers The WAP protocols are designed to operate over a variety of different bearer services, including short message, circuit-switched data, and packet data. The bearers offer differing levels of quality of service with respect to throughput, error rate, and delays. The WAP protocols are designed to compensate for or tolerate these varying level of service. Short Message Service Given its limited length of 160 characters per short message, SMS may not be an adequate bearer for WAP because of the weight protocol of the protocol. The overhead of the WAP protocol that would be required to be transmitted in an SMS message would mean that even for the simplest of transactions several SMS messages may in fact have to be sent. This means that using SMS as a bearer can be a time consuming and expensive exercise. Only one network operator- SBC of the US- is known to be developing WAP services based on SMS. Circuit Switched Data Most of the trial WAP based services use CSD as the underlying bearer. Since CSD has relatively few users currently, WAP could kickstart usage of and traffic generated by this bearer. However, CSD lacks immediacy- a dial up connection taking about 10 seconds is required to connect the WAP client to the WAP Gateway, and this is the best case scenario when there is an complete end to end digital call- in the case of the need for analog modem handshaking (because the WAP phone does not support V.110 the digital protocol, or the WAP Gateway does not have a digital direct connection such as ISDN into the mobile network), the connect time is increased to about 30 seconds. Unstructured Supplementary Services Data USSD has some advantages and disadvantages as a tool for deploying services on mobile networks: • Turnaround response times for interactive applications are shorter for USSD than SMS because of the session-based feature of USSD, and because it is NOT a store and forward service. According to Nokia, USSD can be up to seven times faster than SMS to carry out the same two-way transaction. • Users do not need to access any particular phone menu to access services with USSD - they can enter the Unstructured Supplementary Services Data (USSD) command direct from the initial mobile phone screen. • Unstructured Supplementary Services Data (USSD) works on all existing GSM mobile phones. • USSD strings are typically complicated for the user to remember, involving the use of the "*" and "#" characters to denote the start and finish of the USSD string. However, USSD strings for regularly used services can be stored in the phonebook, reducing the need to remember and reenter them. As such, USSD could be am ideal bearer for WAP on GSM networks. General Packet Radio Service The General Packet Radio Service (GPRS) is a new packet-based bearer that is being introduced on many GSM and TDMA mobile networks from the year 2000 onwards. It is an exciting new bearer because it is immediate (there is no dial up connection), relatively fast (up to 177.2 kbps in the very best theoretical extreme) and supports virtual connectivity, allowing relevant information to be sent from the network as and when it is generated. Since all but the early WAP enabled phones will also support the General Packet Radio Service, WAP and GPRS could well be synergistic and be used widely together. For the kinds of interactive, menu based information exchanges that WAP anticipates, Circuit Switched Data is not immediate enough because of the need to set up a call. Early prototypes of WAP services based on Circuit Switched Data were therefore close to unusable. SMS on the other hand is immediate but is ALWAYS store and forward, such that even when a subscriber has just requested information from their microbrowser, the SMS Center resources are used in the information transfer. As such, GPRS and WAP are ideal bearers for each other. 5.7. Other Services and Applications The WAP layered architecture enables other services and applications to utilise the features of the WAP stack through a set of well-defined interfaces. External applications may access the session, transaction, security and transport layers directly. This allows the WAP stack to be used for applications and services not currently specified by WAP, but deemed to be valuable for the wireless market. For example, applications, such as electronic mail, calendar, phone book, notepad, and electronic commerce, or services, such as white and yellow pages, may be developed to use the WAP protocols. 5.8. Sample Configurations of WAP Technology WAP technology is expected to be useful for applications and services beyond those specified by the WAP Forum. Figure 5 depicts several possible protocol stacks using WAP technology. These are for illustrative purposes only and do not constitute a statement of conformance or interoperability. The leftmost stack represents a typical example of a WAP application, i.e., WAE user agent, running over the complete portfolio of WAP technology. The middle stack is intended for applications and services that require transaction services with or without security. The rightmost stack is intended for applications and services that only require datagram transport with or without security. 6. Comparison WAP is based on existing Internet standards. The WAP architecture was designed to enable standard off-the-shelf Internet servers to provide services to wireless devices. While communicating with wireless devices, WAP uses many Internet standards such as XML, UDP, and IP. The WAP wireless protocols are based on Internet standards such as HTTP and TLS, but have been optimized for the unique constraints of the wireless environment. networks like intermittent coverage, long latencies and limited bandwidth, which, with wireless transmission latencies, results in a very slow response for the user. WAP uses binary transmission for greater compression of data and is hence optimized for long latency and low to medium bandwidth. WAP sessions cope with intermittent coverage and can operate over a wide variety of wireless transports using IP where possible and other optimized protocols where IP is impossible. The WML language used for WAP content makes optimum use of small screens and allows easy navigation with one hand. It also includes a built-in salability from two-line text displays to the full graphic screens on smart phones and communicators. 7. Future Outlook For WAP The point brought about by many analysts against WAP is that with the emergence of next generations networks (including GPRS), as the data capabilities of these networks evolve, it will make possible the delivery of full-motion video images and high-fidelity sound over mobile networks. On the other hand many believe that with the introduction of packet-switched data networks will kick-start the take-up of WAP services. Japan and South Korea are forging ahead, having already introduced packet data on their networks. What should be understood is that the limitations in mobile Internet access are not just the low bandwidths available. The very nature of mobile devices presents limitations like display etc. Internet access via WAP should infact become much easier with WAP. Currently, WAP access needs a specific connection via an Internet service provider (ISP) in much the same way as a PC accesses. But the system will come into its own with the introduction of another enabling technology, general packet radio services (GPRS), a method of sending Internet information to mobile telephones at high speed. At present, services such as BT Cell net’s Genie deliver information at a speed of 9,600 bits of information a second. With GPRS the speed will rise to 100,000 bits. Mobile commerce is one such application that can open up lots of opportunities for WAP. By 2004, there could be more than 700m mobile commerce users. M-commerce is emerging more rapidly in Europe and in Asia, where mobile services are relatively advanced, than in the US where mobile telephony has only just begun to take off. WAP is one of the families of technologies that have the potential of bringing about the convergence of mobile communications and the Internet. Technologies like Bluetooth will connect the mobile to the personal computers. GPRS has the potential to deliver Internet information to mobile phones many times faster than conventional GSM technology. By allowing mobile to be in always connected state GPRS (or other services like CDPD) will bring Internet more closely to mobile. Conclusion: Some critics and second-guessers have pondered the need for a technology such as WAP in the marketplace. With the widespread proliferation of HTML, is yet another markup language really required? As we’ve discussed here, in a word, YES! WAP’s use of the deck of cards “pattern” and use of binary file distribution meshes well with the display size and bandwidth constraints of typical wireless devices. Scripting support gives us support for client-side user validation and interaction with the portable device again helping to eliminate round trips to remote servers. WAP is a young technology that is certain to mature as the wireless data industry as a whole matures; however, even as it exists today, it can be used as an extremely powerful tool in every software developer’s toolbox Bibliography: http://www.wirelessdevnet.com/ http://www.altavista.com/ http://www.wapforum.org/ http://www.wap.net/ Reference books: Professional Wap (Programmer to Programmer) (Paperback) by Charles Arehart (Author),
wave of mobile-Internet communications. WAP is an enabling technology that willbridge the gap between the mobile world and the Internet, bringing sophisticated solutions to mobile users, independent of the user and network. Backed by 75 percent of the companies behind the world's mobile telephone market and the huge development potential of WAP, the future for WAP looks bright Introduction The Wireless Application Protocol (WAP) is a hot topic that has been widely hyped in the mobile industry and outside of it. WAP is simply a protocol- a standardized way that a mobile phone talks to a server installed in the mobile phone network. WAP is hot for several reasons:
• It provides a standardized way of linking the Internet to mobile phones, thereby linking two of the hottest industries anywhere. • Its founder members include the major wireless vendors of Nokia, Ericsson and Motorola, plus a newcomer Phone.com. • Mobile information services, a key application for WAP, have not been as successful as many network operators expected. WAP is seen as a way to rectify this situation. 1. Motivation WAP is positioned at the convergence of two rapidly evolving network technologies, wireless data and the Internet. The explosive growth of the Internet has fuelled the creation of new and exciting information services. Most of the technology developed for the Internet has been designed for desktop and larger computers and medium to high bandwidth, generally reliable data networks. Mass-market, hand-held wireless devices present a more constrained computing environment compared to desktop computers. Because of fundamental limitations of power and form-factor, mass-market handheld devices tend to have: •Less powerful CPUs, •Less memory (ROM and RAM), •Restricted power consumption, •Smaller displays, and •Different input devices (eg, a phone keypad). Similarly, wireless data networks present a more constrained communication environment compared to wired networks. Because of fundamental limitations of power, available spectrum, and mobility, wireless data networks tend to have: •Less bandwidth, •More latency, •Less connection stability, and •Less predictable availability. Mobile networks are growing in complexity and the cost of all aspects for provisioning of more value added services is increasing. In order to meet the requirements of mobile network operators, solutions must be: •Interoperable – terminals from different manufacturers communicate with services in the mobile network; •Scaleable – mobile network operators are able to scale services to customer needs; •Efficient – provides quality of service suited to the behaviour and characteristics of the mobile network; •Reliable – provides a consistent and predictable platform for deploying services; and •Secure – enables services to be extended over potentially unprotected mobile networks while still preserving the integrity of user data; protects the devices and services from security problems such as denial of service. 2. The WAP Model The WAP programming model (Figure 2) is similar to the WWW programming model. This provides several benefits to the application developer community, including a familiar programming model, a proven architecture,and the ability to leverage existing tools (eg, Web servers, XML tools, etc.). Optimisations and extensions have been made in order to match the characteristics of the wireless environment. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology. WAP defines a set of standard components that enable communication between mobile terminals and network servers, including: •Standard naming model – WWW-standard URLs are used to identify WAP content on origin servers. WWW-standard URIs are used to identify local resources in a device, eg call control functions. •Content typing – All WAP content is given a specific type consistent with WWW typing. This allows WAP user agents to correctly process the content based on its type. •Standard content formats – WAP content formats are based on WWW technology and include display markup, calendar information, electronic business card objects, images and scripting language. •Standard communication protocols – WAP communication protocols enable the communication of browserrequests from the mobile terminal to the network web server. The WAP content types and protocols have been optimised for mass market, hand-held wireless devices. WAP utilises proxy technology to connect between the wireless domain and the WWW. The WAP proxy typically is comprised of the following functionality: •Protocol Gateway – The protocol gateway translates requests from the WAP protocol stack (WSP, WTP, WTLS, and WDP) to the WWW protocol stack (HTTP and TCP/IP). •Content Encoders and Decoders – The content encoders translate WAP content into compact encoded formats to reduce the size of data over the network. 3. Example WAP Network In the example, the WAP client communicates with two servers in the wireless network : • The WAP proxy translates WAP requests to WWW requests thereby allowing the WAP client to submit requests to the web server. The proxy also encodes the responses from the web server into the compact binary format understood by the client. If the web server provides WAP content (e.g., WML), the WAP proxy retrieves it directly from the web server. However, if the web server provides WWW content (such as HTML), a filter is used to translate the WWW content into WAP content. • The Wireless Telephony Application (WTA) server is an example origin or gateway server that responds to requests from the WAP client directly. The WTA server is used to provide WAP access to features of the wireless network provider’s telecommunications infrastructure. 4. Components of the WAP Architecture The WAP architecture provides a scaleable and extensible environment for application development for mobile communication devices. This is achieved through a layered design of the entire protocol stack (Figure 4). Each of the layers of the architecture is accessible by the layers above, as well as by other services and applications. The WAP layered architecture enables other services and applications to utilise the features of the WAP stack through a set of well-defined interfaces. External applications may access the session, transaction, security and transport layers directly. The following sections provide a description of the various elements of the protocol stack architecture. 5.1. Wireless Application Environment (WAE) The Wireless Application Environment (WAE) is a general-purpose application environment based on a combination of World Wide Web (WWW) and Mobile Telephony technologies. The primary objective of the WAE effort is to establish an interoperable environment that will allow operators and service providers to build applications and services that can reach a wide variety of different wireless platforms in an efficient and useful manner. WAE includes a micro-browser environment containing the following functionality: •Wireless Markup Language (WML) – a lightweight markup language, similar to HTML, but optimised for use in hand-held mobile terminals; •WMLScript – a lightweight scripting language, similar to JavaScript™; •Wireless Telephony Application (WTA, WTAI) – telephony services and programming interfaces; and •Content Formats – a set of well-defined data formats, including images, phone book records and calendar information. 5.2. Wireless Session Protocol (WSP) The Wireless Session Protocol (WSP) provides the application layer of WAP with a consistent interface for two session services. The first is a connection-oriented service that operates above the transaction layer protocol WTP. The second is a connectionless service that operates above a secure or non-secure datagram service (WDP). The Wireless Session Protocols currently consist of services suited for browsing applications (WSP/B). WSP/B provides the following functionality: •HTTP/1.1 functionality and semantics in a compact over-the-air encoding, •Long-lived session state, •Session suspend and resume with session migration, •A common facility for reliable and unreliable data push, and •Protocol feature negotiation. The protocols in the WSP family are optimised for low-bandwidth bearer networks with relatively long latency. WSP/B is designed to allow a WAP proxy to connect a WSP/B client to a standard HTTP server. 5.3. Wireless Transaction Protocol (WTP) The Wireless Transaction Protocol (WTP) runs on top of a datagram service and provides as a light-weight transaction-oriented protocol that is suitable for implementation in “thin” clients (mobile stations). WTP operates efficiently over secure or non-secure wireless datagram networks and provides the following features: •Three classes of transaction service: •Unreliable one-way requests, •Reliable one-way requests, and •Reliable two-way request-reply transactions; •Optional user-to-user reliability - WTP user triggers the confirmation of each received message; •Optional out-of-band data on acknowledgements; •PDU concatenation and delayed acknowledgement to reduce the number of messages sent; and •Asynchronous transactions. 5.4. Wireless Transport Layer Security (WTLS) WTLS is a security protocol based upon the industry-standard Transport Layer Security (TLS) protocol, formerly known as Secure Sockets Layer (SSL). WTLS is intended for use with the WAP transport protocols and has been optimised for use over narrow-band communication channels. WTLS provides the following features: •Data integrity – WTLS contains facilities to ensure that data sent between the terminal and an application server is unchanged and uncorrupted. •Privacy – WTLS contains facilities to ensures that data transmitted between the terminal and an application server is private and cannot be understood by any intermediate parties that may have intercepted the data stream. •Authentication – WTLS contains facilities to establish the authenticity of the terminal and application server. •Denial-of-service protection – WTLS contains facilities for detecting and rejecting data that is replayed or not successfully verified. WTLS makes many typical denial-of-service attacks harder to accomplish and protects the upper protocol layers. WTLS may also be used for secure communication between terminals, eg, for authentication of electronic business card exchange. Applications are able to selectively enable or disable WTLS features depending on their security requirements and the characteristics of the underlying network (eg, privacy may be disabled on networks already providing this service at a lower layer). 5.5. Wireless Datagram Protocol (WDP) The Transport layer protocol in the WAP architecture is referred to as the Wireless Datagram Protocol (WDP). The WDP layer operates above the data capable bearer services supported by the various network types. As a general transport service, WDP offers a consistent service to the upper layer protocols of WAP and communicate transparently over one of the available bearer services. Since the WDP protocols provide a common interface to the upper layer protocols the Security, Session and Application layers are able to function independently of the underlying wireless network. This is accomplished by adapting the transport layer to specific features of the underlying bearer. By keeping the transport layer interface and the basic features consistent, global interoperability can be achieved using mediating gateways. 5.6. Bearers The WAP protocols are designed to operate over a variety of different bearer services, including short message, circuit-switched data, and packet data. The bearers offer differing levels of quality of service with respect to throughput, error rate, and delays. The WAP protocols are designed to compensate for or tolerate these varying level of service. Short Message Service Given its limited length of 160 characters per short message, SMS may not be an adequate bearer for WAP because of the weight protocol of the protocol. The overhead of the WAP protocol that would be required to be transmitted in an SMS message would mean that even for the simplest of transactions several SMS messages may in fact have to be sent. This means that using SMS as a bearer can be a time consuming and expensive exercise. Only one network operator- SBC of the US- is known to be developing WAP services based on SMS. Circuit Switched Data Most of the trial WAP based services use CSD as the underlying bearer. Since CSD has relatively few users currently, WAP could kickstart usage of and traffic generated by this bearer. However, CSD lacks immediacy- a dial up connection taking about 10 seconds is required to connect the WAP client to the WAP Gateway, and this is the best case scenario when there is an complete end to end digital call- in the case of the need for analog modem handshaking (because the WAP phone does not support V.110 the digital protocol, or the WAP Gateway does not have a digital direct connection such as ISDN into the mobile network), the connect time is increased to about 30 seconds. Unstructured Supplementary Services Data USSD has some advantages and disadvantages as a tool for deploying services on mobile networks: • Turnaround response times for interactive applications are shorter for USSD than SMS because of the session-based feature of USSD, and because it is NOT a store and forward service. According to Nokia, USSD can be up to seven times faster than SMS to carry out the same two-way transaction. • Users do not need to access any particular phone menu to access services with USSD - they can enter the Unstructured Supplementary Services Data (USSD) command direct from the initial mobile phone screen. • Unstructured Supplementary Services Data (USSD) works on all existing GSM mobile phones. • USSD strings are typically complicated for the user to remember, involving the use of the "*" and "#" characters to denote the start and finish of the USSD string. However, USSD strings for regularly used services can be stored in the phonebook, reducing the need to remember and reenter them. As such, USSD could be am ideal bearer for WAP on GSM networks. General Packet Radio Service The General Packet Radio Service (GPRS) is a new packet-based bearer that is being introduced on many GSM and TDMA mobile networks from the year 2000 onwards. It is an exciting new bearer because it is immediate (there is no dial up connection), relatively fast (up to 177.2 kbps in the very best theoretical extreme) and supports virtual connectivity, allowing relevant information to be sent from the network as and when it is generated. Since all but the early WAP enabled phones will also support the General Packet Radio Service, WAP and GPRS could well be synergistic and be used widely together. For the kinds of interactive, menu based information exchanges that WAP anticipates, Circuit Switched Data is not immediate enough because of the need to set up a call. Early prototypes of WAP services based on Circuit Switched Data were therefore close to unusable. SMS on the other hand is immediate but is ALWAYS store and forward, such that even when a subscriber has just requested information from their microbrowser, the SMS Center resources are used in the information transfer. As such, GPRS and WAP are ideal bearers for each other. 5.7. Other Services and Applications The WAP layered architecture enables other services and applications to utilise the features of the WAP stack through a set of well-defined interfaces. External applications may access the session, transaction, security and transport layers directly. This allows the WAP stack to be used for applications and services not currently specified by WAP, but deemed to be valuable for the wireless market. For example, applications, such as electronic mail, calendar, phone book, notepad, and electronic commerce, or services, such as white and yellow pages, may be developed to use the WAP protocols. 5.8. Sample Configurations of WAP Technology WAP technology is expected to be useful for applications and services beyond those specified by the WAP Forum. Figure 5 depicts several possible protocol stacks using WAP technology. These are for illustrative purposes only and do not constitute a statement of conformance or interoperability. The leftmost stack represents a typical example of a WAP application, i.e., WAE user agent, running over the complete portfolio of WAP technology. The middle stack is intended for applications and services that require transaction services with or without security. The rightmost stack is intended for applications and services that only require datagram transport with or without security. 6. Comparison WAP is based on existing Internet standards. The WAP architecture was designed to enable standard off-the-shelf Internet servers to provide services to wireless devices. While communicating with wireless devices, WAP uses many Internet standards such as XML, UDP, and IP. The WAP wireless protocols are based on Internet standards such as HTTP and TLS, but have been optimized for the unique constraints of the wireless environment. networks like intermittent coverage, long latencies and limited bandwidth, which, with wireless transmission latencies, results in a very slow response for the user. WAP uses binary transmission for greater compression of data and is hence optimized for long latency and low to medium bandwidth. WAP sessions cope with intermittent coverage and can operate over a wide variety of wireless transports using IP where possible and other optimized protocols where IP is impossible. The WML language used for WAP content makes optimum use of small screens and allows easy navigation with one hand. It also includes a built-in salability from two-line text displays to the full graphic screens on smart phones and communicators. 7. Future Outlook For WAP The point brought about by many analysts against WAP is that with the emergence of next generations networks (including GPRS), as the data capabilities of these networks evolve, it will make possible the delivery of full-motion video images and high-fidelity sound over mobile networks. On the other hand many believe that with the introduction of packet-switched data networks will kick-start the take-up of WAP services. Japan and South Korea are forging ahead, having already introduced packet data on their networks. What should be understood is that the limitations in mobile Internet access are not just the low bandwidths available. The very nature of mobile devices presents limitations like display etc. Internet access via WAP should infact become much easier with WAP. Currently, WAP access needs a specific connection via an Internet service provider (ISP) in much the same way as a PC accesses. But the system will come into its own with the introduction of another enabling technology, general packet radio services (GPRS), a method of sending Internet information to mobile telephones at high speed. At present, services such as BT Cell net’s Genie deliver information at a speed of 9,600 bits of information a second. With GPRS the speed will rise to 100,000 bits. Mobile commerce is one such application that can open up lots of opportunities for WAP. By 2004, there could be more than 700m mobile commerce users. M-commerce is emerging more rapidly in Europe and in Asia, where mobile services are relatively advanced, than in the US where mobile telephony has only just begun to take off. WAP is one of the families of technologies that have the potential of bringing about the convergence of mobile communications and the Internet. Technologies like Bluetooth will connect the mobile to the personal computers. GPRS has the potential to deliver Internet information to mobile phones many times faster than conventional GSM technology. By allowing mobile to be in always connected state GPRS (or other services like CDPD) will bring Internet more closely to mobile. Conclusion: Some critics and second-guessers have pondered the need for a technology such as WAP in the marketplace. With the widespread proliferation of HTML, is yet another markup language really required? As we’ve discussed here, in a word, YES! WAP’s use of the deck of cards “pattern” and use of binary file distribution meshes well with the display size and bandwidth constraints of typical wireless devices. Scripting support gives us support for client-side user validation and interaction with the portable device again helping to eliminate round trips to remote servers. WAP is a young technology that is certain to mature as the wireless data industry as a whole matures; however, even as it exists today, it can be used as an extremely powerful tool in every software developer’s toolbox Bibliography: http://www.wirelessdevnet.com/ http://www.altavista.com/ http://www.wapforum.org/ http://www.wap.net/ Reference books: Professional Wap (Programmer to Programmer) (Paperback) by Charles Arehart (Author),
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