- Email: [email protected]
Industrial Control Applications using the Wireless Application Protocol (WAP)
Copyright ® IFAC Telematics Applications in Automation and Robotics, Weingarten, Germany, 2001
INDUSTRIAL CONTROL APPLICATIONS USING THE WIRELESS APPLICATION PROTOCOL (W AP)
Prof. Dr.-Ing. Andreas Linke
Hochschule Magdeburg-Stendal University of Applied Sciences FB Elektrotechnik Breitscheidstr. 2 39114 Magdeburg Phone: ++49391/8864491 Fax.: ++49391/8864 126 [email protected]
Abstract: Telemetry seIVices becomes more and more important in the field of automation. The WAP-Protocol, which is closely related to the internet protocols and standards, offers new opportunities for remote and mobile data access. This article deals with the principles of WAP and gives an outlook on future applications. An example illustrates a remote control application using a microcontroller with an embedded WEB-seIVer and a cellular phone. Copyright @20011FAC Keywords: Remote control, mobile data access, W AP, internet protocols, microcomputer
1 INTRODUCTION
standard published by the WAP-Forum (www.wapforum.com). The WAP-Forum was founded by telecommunication firms like Nokia, Ericson, Motorola and phone. corn and is now joined by all important software companies, device manufacturers and network operators as Microsoft, lntel or Deutsche Telecom. The goals of the WAP-Forum were to define a communication protocol and an application environment who suites best the requirements for mobile communications, namely
New technologies in wireless data transmission offer new challenges for automation in the fields of telemetry and remote control. The Wireless Application Protocol is such a new technology which comes along with the development of a new generation of mobile phones. The intention is to increase the mobility of people or simply speaking "to access information and seIVices anytime, anyhow, anywhere". Putting instead of the phone a mobile modern using the same standards and principles, a large variety of new applications seem to be possible in the field of automation.
•
a low bandwidth,
•
a high latency,
•
unpredictable bearer availability and
•
bounds of wireless devices concerning data input and representation.
2 WHAT IS WAP?
The Wireless Application Protocol (WAP) is an open
53
WTLSlWireless Transport Layer Security provides security features like authentication and encryption.
The WAP-Standard uses the concepts found on the Internet. This allows the use of already proven methods of content distribution, e.g., like the GETrequest in HTIP. The standard includes •
Wireless Datagram Protocol is the interface between the bearers and the upper layers.
WML - The Wireless Markup Language Bearers are the connection services between the mobile phone and the base station.
WML is based directly on XML and could be seen as HTML for wireless applications including WML-Script language. • •
WTA - Wireless Telephony Applications
WAP protocols The WAP-Standard also defines an interface called WT AIlWireless Telephony Application Interface which allows to load functions from a WTA-Server somewhere in the internet and execute them on the mobile phone. Functions can include the preparation of phone book entries for instance. Additionally, a push function has defined to send information to a phone without being requested, e.g. traffic information or stock news. Since this technique has not yet been fully adopted, this article is not dealing with WTA.
The architecture of the WAP protocol stack is similar to the well-known internet stack, but optimized for mobile communication. The WAP protocol stack consists of several layers related to the ISO/OSI network model, see Fig. I below.
. ' , -. '
--
---
. , . --
.....----
. . . . . . .... -- _ ._-
: :.m~~ffi.~t :
\
.
One might say, if WAP is so close to the internet protocols, why not use them instead for wireless communications as well. One reason is the overhead of internet protocols. TCP uses a three-wayhandshake and a lot of control data to ensure that data packets will put together in a right order. The WTP compared with TCP reduced the number of transactions significantly (Arehart, 2000).
Application Layer HTML, JavaScript etc.
HTTP ......
Transaction Layer (WAE)
:.:.
-~""""""'--.., ..•..
Another reason is the constrained bandwidth in wireless communication. WML and WML-Scripts are binary encoded into a compact form to minimize the data flow. Moreover, WSP is a binary form of HTIP, which is the standard internet protocol on WEB-servers.
:<:::::::::::.:.;.: :.... ;-:.:.:.;.;.:::.::::::::::: ...-..... -.-.-.-.-.-.-.-...-.
Security Layer (WTLS) Transport Layer (WDP)
Bearers SMS, GRPS, CSD
lITML, the internet standard language is not suitable for mobile devices. WML is a lightweight markup language designed for devices with limited displays. WML works with desks and cards. A W AP-browser displays one card at a time. However, due to the high latency in a wireless connection, it is necessary to return several cards, which are called desk, on a single req nest.
IP Datalink Layer Physical Layer
Fig. 1. WAP-protocol stack.
W AElWireless Application Environment provides an user environment for mobile data communication.
3 HOW DOES W AP WORK? The general concept of data transmission using W AP is shown in Fig.2. A mobile terminal like a mobile phone or a data modem dials the number of a Remote Access Server (RAS) provided by a network operator. After the connection is established, the client data is forwarded to the WAP-gateway. The gateway sets up a session with the WAP-client on the mobile phone, e.g., a W AP-browser. A Browser request is translated and forwarded by the gateway to an inter-
WSPlWireless Session Protocol provides connection and connectionless session services for data exchange. WTPlWireless Transaction Protocol supplies reliable and non-reliable transactions between a W AP client and a server.
54
net origin server. The server sends a WML-desk which is then passed by the gateway to the client browser to be displayed.
Some processes can operate at a remote location witilout being permanently observed, e.g. traffic lights. But in case of a failure, tile service center has to be informed. To send a SMS-message does not mean using W AP. However, if a service technician needs additional information about the situation on-site he can use his W AP-Browser of his mobile phone. •
Facility/Utility Management
Mobile Client
NE;~~~~ OP~ATOR
11-
By using a HTTP-Server it is very easy to bring some in-house information to a mobile phone, e.g. the temperature, and control it by a W APBrowser. Automatic meter reading of utility meters is anotller future application using W APbased data communication.
J 1
Voice/Data Switch Base Station
•
RAS-Server
Telemetry / Remote Control Utilities often have remote located stations equipped witil pumps or valves which have to be integrated in a central SCADA-system. As tilese stations are often far away from public telephone networks, it is clearly tlle best solution to use wireless data processing over WAP.
•
HTTP Origin Server
5 EXAMPLE: REMOTE CONTROL WITH W AP
HTTP Origin Server
The following example demonstrates a remote control application using W AP, see figure 3. A small 11controller hosts a WEB-server, an ethernet and a serial interface and an 1I0-port of 8 bits. To read and write the bits, the following procedure is used
Fig. 2. Data flow using W AP.
4 APPLICATIONS IN TELEMATICS As W AP is supported by the most telecommunication and software firms it is likely that W AP becomes the new standard in wireless and mobile data communication in the future. There are many applications in process automation where data communication plays an important role. The advantage of using W AP instead of some proprietary protocols means to take advantage of the well-known internet concepts and using a standard interface to the application environment. Some applications where W AP is used or will be used in the near future will be outlined here •
Telematics / Fleet management It is assumed that every car will be equipped with an IP-Address in 2010 (Durlacher, 2000). After tilat WAP-based applications like tele-diagnostics and route-planing arc possible. A modem combined witil a GPS-receiver can be used for fleet management, whereas GSMlGPS modems are already available.
Supervisory / Alaml monitoring
55
•
A cOIDlection is established by diaIing tlle network operator's RAS-number which is then followed by a GET -request for an URL hosted on the l1-controller.
•
The WAP-gateway forwards the request of the W AP-client to the WEB-server. The WEBserver addresses a C-program which produces WML-code containing infornlation of the 110Port.
•
The WML-code is trdnsmitted to the WAP-client to be displayed. To control tile 1I0-Port, an URL-request has to be send witil additional control infoffilation used by the C-progranl to change tile bits.
The network operator's infrastructure consists of the voice/data switch, an RAS-Server to handle concurrent users and the WAP-Gateway. For security reasons the WAP-gateway of the network operator can also be situated in the company which rules the micro-controller applications.
Network operator's infrastructure
l j
~~"
J
INTERNET ~
/'
)
~).micro-controller mcludmg .
t-
.
I
~ embedded WEB-server
I I
O
~
Network operator 's infrastructure
~
r~
I/O-Ports
~/
Fig. 3. Data flow using to remote controller. With the configuration of Fig. 3, only the WAPclient is mobile but not the remote controller which could be useful in some applications. In this case we need an additional Dial-up-server which serves as a proxy and establishes a PPP-connection with the remote controller via a GSM-modem, see Fig. 4.
l
rnTERNET
~J-
)
Dial-Up-serve~ f~~ Public Telephone
)
NetworkJ-)
~
~
The Dial-up-server hosts a modified WEB-server. After receiving a GET-request, which addresses the micro-controller, the Dial-up-server calls the controller via the public telephone network and establishes a PPP-Connection with full User- and Password-verifications. Using this connection, the Dialup-server forwards the GET-request to the WEBserver hosted on the micro-controller asking for the content. At last, the content is send to the WAPclient, see Fig. 5.
micro-controller including embedded WEB-server
rtL:;;;::q ;:;;::!::O
/'
The concept seems to be very complicated and one may ask: Why not installing a WAP-server respectively a WAP-gateway on the controller instead? First of all, mobile users are not reachable all the time so that messages and data have to be stored somewhere, for instance on the dial-up server. Additionally, a new software release, e.g. for the WMLcodes or CGI-scripts, will cause a lot of updates in a distributed solution.
Fig. 4. Data flow to remote mobile controller.
56
6 CONCLUSIONS This article deals with the wireless application protocol WAP. Although it is a very new standard, it is supported by many firms from U.S. and Europe and seems to have a great future . WAP was created for m-commerce closely related to the internet principles of data transmission Although it is not created with telematics applications in mind, it is easy to apply WAP as a secure and reliable mechanism for data processing including an open interface to the internet.
1
NTT DoCoMo (Durlacher, 2000) estimates that only in Japan nearly 240 million wireless units including cars, portable PCs, boats, vending machines and industrial equipment can be connected over a long distance in the near future. This seems to be a challenge for developing telematics applications based on WAP. However, Western Europe is the only continent which has adopted GSM respectively CSD and SMS as a bearer standard which makes it easier for WAP to succeed. The D.S. have not been able to find a unique solution. On the other hand, Japan is very successful by using its own wireless communication stack called iMode.
call --"
GETURl WIT (Bmary)
GETURL HITP (ASCII )
call
ppp Authentif.
write
Usemame Password
WML
I.L
read
I'
HITP (ASCII)
WML I' WTP (Binary ! ASCII)
WML
With respect to the success of iMode it is expected that the use of GPRS and UMTS - also based on the principle of packet switched datal - is another asset for mobile remote control applications. As a WAPclient is continuously connected to the network operator, the data access time can be reduced significantly.
HITP (ASCII)
1
Fig. 5. Sequence diagram for data access.
For security reasons the WAP-gateway of the network operator can be replaced by a gateway of the company which is responsible for the microcontroller applications. In this case, the company needs to install a router which allows concurrent calling users to access the ...
In such a case, the company has two alternatives •
installing a RAS-Server and their own WAPGateway in-house
•
installing their own W AP-Gateway and using the RAS-Server of the network operator. The data from the Server to the Gateway is then transmitted via UDP over lP.
The question is: Can WAP reaches the critical number of users to make it commercially attractive for developing new applications? The answer seems to be yes, as WAP is strongly being pushed in the market by m-commerce applications. Additionally, the growing use of TCPIIP in automation also backs WAP to be adopted as a standard protocol for long distance remote control applications, since WAP offers an easy-to-use interface to the internet.
Data encryption could be done by the WTSLProtocol which is based on the internet standard TSL, formerly SSL. WTSL is used from the WAP-Client (mobile client) to the Gateway, TSL is the protocol of choice for a secure connection from the Gateway to the micro-controller over the internet. The transformation from WTSL to TSL takes place in the Gateway. Therefor, it could be useful to install the WAP-Gateway under the control of the company because during the transformation the data is decrypted. This could cause security problems when the Gateway is hosted by the Network operator.
I On contrast to GSM which is based on circuit switched data (CSD).
57
8 REFERENCES
7 ABBREVIATIONS CGI CSD GPRS GPS GSM
HTTP IP PPP
RAS SCADA
SMS SSL TCP TSL
UDP UMTS URL
XML
Arehart et. al (2000). W AP-Gateways. In: Professional W AP, page 79. Wrox press Ltd, Birmingham, Great Britain, ISBN 1-8610044)-44. Durlacher Research Ltd. (2000). Mobile Commerce Report. In: Mobile Networking with WAP, page 316, Vieweg Veriag, Gennany, ISBN 3-528-03149-2. WAP-Forum www.wapforum.com
Common Graphics Interface Circuit Switched Data General Packet Radio Service Global Positioning System Global System for Mobile communications HyperText Transfer Protocol Internet Protocol Point-to-Point Protocol Remote Access Server Supervisory, Control and Data Acquisition Short Message Service Secure Socket Layer Transmission Control Protocol Transport Layer Security User Datagram Protocol Universal Mobile Telecommunication Systems Uniform Resource Locater eXtensible Markup Language
58
INDUSTRIAL CONTROL APPLICATIONS USING THE WIRELESS APPLICATION PROTOCOL (W AP)
Prof. Dr.-Ing. Andreas Linke
Hochschule Magdeburg-Stendal University of Applied Sciences FB Elektrotechnik Breitscheidstr. 2 39114 Magdeburg Phone: ++49391/8864491 Fax.: ++49391/8864 126 [email protected]
Abstract: Telemetry seIVices becomes more and more important in the field of automation. The WAP-Protocol, which is closely related to the internet protocols and standards, offers new opportunities for remote and mobile data access. This article deals with the principles of WAP and gives an outlook on future applications. An example illustrates a remote control application using a microcontroller with an embedded WEB-seIVer and a cellular phone. Copyright @20011FAC Keywords: Remote control, mobile data access, W AP, internet protocols, microcomputer
1 INTRODUCTION
standard published by the WAP-Forum (www.wapforum.com). The WAP-Forum was founded by telecommunication firms like Nokia, Ericson, Motorola and phone. corn and is now joined by all important software companies, device manufacturers and network operators as Microsoft, lntel or Deutsche Telecom. The goals of the WAP-Forum were to define a communication protocol and an application environment who suites best the requirements for mobile communications, namely
New technologies in wireless data transmission offer new challenges for automation in the fields of telemetry and remote control. The Wireless Application Protocol is such a new technology which comes along with the development of a new generation of mobile phones. The intention is to increase the mobility of people or simply speaking "to access information and seIVices anytime, anyhow, anywhere". Putting instead of the phone a mobile modern using the same standards and principles, a large variety of new applications seem to be possible in the field of automation.
•
a low bandwidth,
•
a high latency,
•
unpredictable bearer availability and
•
bounds of wireless devices concerning data input and representation.
2 WHAT IS WAP?
The Wireless Application Protocol (WAP) is an open
53
WTLSlWireless Transport Layer Security provides security features like authentication and encryption.
The WAP-Standard uses the concepts found on the Internet. This allows the use of already proven methods of content distribution, e.g., like the GETrequest in HTIP. The standard includes •
Wireless Datagram Protocol is the interface between the bearers and the upper layers.
WML - The Wireless Markup Language Bearers are the connection services between the mobile phone and the base station.
WML is based directly on XML and could be seen as HTML for wireless applications including WML-Script language. • •
WTA - Wireless Telephony Applications
WAP protocols The WAP-Standard also defines an interface called WT AIlWireless Telephony Application Interface which allows to load functions from a WTA-Server somewhere in the internet and execute them on the mobile phone. Functions can include the preparation of phone book entries for instance. Additionally, a push function has defined to send information to a phone without being requested, e.g. traffic information or stock news. Since this technique has not yet been fully adopted, this article is not dealing with WTA.
The architecture of the WAP protocol stack is similar to the well-known internet stack, but optimized for mobile communication. The WAP protocol stack consists of several layers related to the ISO/OSI network model, see Fig. I below.
. ' , -. '
--
---
. , . --
.....----
. . . . . . .... -- _ ._-
: :.m~~ffi.~t :
\
.
One might say, if WAP is so close to the internet protocols, why not use them instead for wireless communications as well. One reason is the overhead of internet protocols. TCP uses a three-wayhandshake and a lot of control data to ensure that data packets will put together in a right order. The WTP compared with TCP reduced the number of transactions significantly (Arehart, 2000).
Application Layer HTML, JavaScript etc.
HTTP ......
Transaction Layer (WAE)
:.:.
-~""""""'--.., ..•..
Another reason is the constrained bandwidth in wireless communication. WML and WML-Scripts are binary encoded into a compact form to minimize the data flow. Moreover, WSP is a binary form of HTIP, which is the standard internet protocol on WEB-servers.
:<:::::::::::.:.;.: :.... ;-:.:.:.;.;.:::.::::::::::: ...-..... -.-.-.-.-.-.-.-...-.
Security Layer (WTLS) Transport Layer (WDP)
Bearers SMS, GRPS, CSD
lITML, the internet standard language is not suitable for mobile devices. WML is a lightweight markup language designed for devices with limited displays. WML works with desks and cards. A W AP-browser displays one card at a time. However, due to the high latency in a wireless connection, it is necessary to return several cards, which are called desk, on a single req nest.
IP Datalink Layer Physical Layer
Fig. 1. WAP-protocol stack.
W AElWireless Application Environment provides an user environment for mobile data communication.
3 HOW DOES W AP WORK? The general concept of data transmission using W AP is shown in Fig.2. A mobile terminal like a mobile phone or a data modem dials the number of a Remote Access Server (RAS) provided by a network operator. After the connection is established, the client data is forwarded to the WAP-gateway. The gateway sets up a session with the WAP-client on the mobile phone, e.g., a W AP-browser. A Browser request is translated and forwarded by the gateway to an inter-
WSPlWireless Session Protocol provides connection and connectionless session services for data exchange. WTPlWireless Transaction Protocol supplies reliable and non-reliable transactions between a W AP client and a server.
54
net origin server. The server sends a WML-desk which is then passed by the gateway to the client browser to be displayed.
Some processes can operate at a remote location witilout being permanently observed, e.g. traffic lights. But in case of a failure, tile service center has to be informed. To send a SMS-message does not mean using W AP. However, if a service technician needs additional information about the situation on-site he can use his W AP-Browser of his mobile phone. •
Facility/Utility Management
Mobile Client
NE;~~~~ OP~ATOR
11-
By using a HTTP-Server it is very easy to bring some in-house information to a mobile phone, e.g. the temperature, and control it by a W APBrowser. Automatic meter reading of utility meters is anotller future application using W APbased data communication.
J 1
Voice/Data Switch Base Station
•
RAS-Server
Telemetry / Remote Control Utilities often have remote located stations equipped witil pumps or valves which have to be integrated in a central SCADA-system. As tilese stations are often far away from public telephone networks, it is clearly tlle best solution to use wireless data processing over WAP.
•
HTTP Origin Server
5 EXAMPLE: REMOTE CONTROL WITH W AP
HTTP Origin Server
The following example demonstrates a remote control application using W AP, see figure 3. A small 11controller hosts a WEB-server, an ethernet and a serial interface and an 1I0-port of 8 bits. To read and write the bits, the following procedure is used
Fig. 2. Data flow using W AP.
4 APPLICATIONS IN TELEMATICS As W AP is supported by the most telecommunication and software firms it is likely that W AP becomes the new standard in wireless and mobile data communication in the future. There are many applications in process automation where data communication plays an important role. The advantage of using W AP instead of some proprietary protocols means to take advantage of the well-known internet concepts and using a standard interface to the application environment. Some applications where W AP is used or will be used in the near future will be outlined here •
Telematics / Fleet management It is assumed that every car will be equipped with an IP-Address in 2010 (Durlacher, 2000). After tilat WAP-based applications like tele-diagnostics and route-planing arc possible. A modem combined witil a GPS-receiver can be used for fleet management, whereas GSMlGPS modems are already available.
Supervisory / Alaml monitoring
55
•
A cOIDlection is established by diaIing tlle network operator's RAS-number which is then followed by a GET -request for an URL hosted on the l1-controller.
•
The WAP-gateway forwards the request of the W AP-client to the WEB-server. The WEBserver addresses a C-program which produces WML-code containing infornlation of the 110Port.
•
The WML-code is trdnsmitted to the WAP-client to be displayed. To control tile 1I0-Port, an URL-request has to be send witil additional control infoffilation used by the C-progranl to change tile bits.
The network operator's infrastructure consists of the voice/data switch, an RAS-Server to handle concurrent users and the WAP-Gateway. For security reasons the WAP-gateway of the network operator can also be situated in the company which rules the micro-controller applications.
Network operator's infrastructure
l j
~~"
J
INTERNET ~
/'
)
~).micro-controller mcludmg .
t-
.
I
~ embedded WEB-server
I I
O
~
Network operator 's infrastructure
~
r~
I/O-Ports
~/
Fig. 3. Data flow using to remote controller. With the configuration of Fig. 3, only the WAPclient is mobile but not the remote controller which could be useful in some applications. In this case we need an additional Dial-up-server which serves as a proxy and establishes a PPP-connection with the remote controller via a GSM-modem, see Fig. 4.
l
rnTERNET
~J-
)
Dial-Up-serve~ f~~ Public Telephone
)
NetworkJ-)
~
~
The Dial-up-server hosts a modified WEB-server. After receiving a GET-request, which addresses the micro-controller, the Dial-up-server calls the controller via the public telephone network and establishes a PPP-Connection with full User- and Password-verifications. Using this connection, the Dialup-server forwards the GET-request to the WEBserver hosted on the micro-controller asking for the content. At last, the content is send to the WAPclient, see Fig. 5.
micro-controller including embedded WEB-server
rtL:;;;::q ;:;;::!::O
/'
The concept seems to be very complicated and one may ask: Why not installing a WAP-server respectively a WAP-gateway on the controller instead? First of all, mobile users are not reachable all the time so that messages and data have to be stored somewhere, for instance on the dial-up server. Additionally, a new software release, e.g. for the WMLcodes or CGI-scripts, will cause a lot of updates in a distributed solution.
Fig. 4. Data flow to remote mobile controller.
56
6 CONCLUSIONS This article deals with the wireless application protocol WAP. Although it is a very new standard, it is supported by many firms from U.S. and Europe and seems to have a great future . WAP was created for m-commerce closely related to the internet principles of data transmission Although it is not created with telematics applications in mind, it is easy to apply WAP as a secure and reliable mechanism for data processing including an open interface to the internet.
1
NTT DoCoMo (Durlacher, 2000) estimates that only in Japan nearly 240 million wireless units including cars, portable PCs, boats, vending machines and industrial equipment can be connected over a long distance in the near future. This seems to be a challenge for developing telematics applications based on WAP. However, Western Europe is the only continent which has adopted GSM respectively CSD and SMS as a bearer standard which makes it easier for WAP to succeed. The D.S. have not been able to find a unique solution. On the other hand, Japan is very successful by using its own wireless communication stack called iMode.
call --"
GETURl WIT (Bmary)
GETURL HITP (ASCII )
call
ppp Authentif.
write
Usemame Password
WML
I.L
read
I'
HITP (ASCII)
WML I' WTP (Binary ! ASCII)
WML
With respect to the success of iMode it is expected that the use of GPRS and UMTS - also based on the principle of packet switched datal - is another asset for mobile remote control applications. As a WAPclient is continuously connected to the network operator, the data access time can be reduced significantly.
HITP (ASCII)
1
Fig. 5. Sequence diagram for data access.
For security reasons the WAP-gateway of the network operator can be replaced by a gateway of the company which is responsible for the microcontroller applications. In this case, the company needs to install a router which allows concurrent calling users to access the ...
In such a case, the company has two alternatives •
installing a RAS-Server and their own WAPGateway in-house
•
installing their own W AP-Gateway and using the RAS-Server of the network operator. The data from the Server to the Gateway is then transmitted via UDP over lP.
The question is: Can WAP reaches the critical number of users to make it commercially attractive for developing new applications? The answer seems to be yes, as WAP is strongly being pushed in the market by m-commerce applications. Additionally, the growing use of TCPIIP in automation also backs WAP to be adopted as a standard protocol for long distance remote control applications, since WAP offers an easy-to-use interface to the internet.
Data encryption could be done by the WTSLProtocol which is based on the internet standard TSL, formerly SSL. WTSL is used from the WAP-Client (mobile client) to the Gateway, TSL is the protocol of choice for a secure connection from the Gateway to the micro-controller over the internet. The transformation from WTSL to TSL takes place in the Gateway. Therefor, it could be useful to install the WAP-Gateway under the control of the company because during the transformation the data is decrypted. This could cause security problems when the Gateway is hosted by the Network operator.
I On contrast to GSM which is based on circuit switched data (CSD).
57
8 REFERENCES
7 ABBREVIATIONS CGI CSD GPRS GPS GSM
HTTP IP PPP
RAS SCADA
SMS SSL TCP TSL
UDP UMTS URL
XML
Arehart et. al (2000). W AP-Gateways. In: Professional W AP, page 79. Wrox press Ltd, Birmingham, Great Britain, ISBN 1-8610044)-44. Durlacher Research Ltd. (2000). Mobile Commerce Report. In: Mobile Networking with WAP, page 316, Vieweg Veriag, Gennany, ISBN 3-528-03149-2. WAP-Forum www.wapforum.com
Common Graphics Interface Circuit Switched Data General Packet Radio Service Global Positioning System Global System for Mobile communications HyperText Transfer Protocol Internet Protocol Point-to-Point Protocol Remote Access Server Supervisory, Control and Data Acquisition Short Message Service Secure Socket Layer Transmission Control Protocol Transport Layer Security User Datagram Protocol Universal Mobile Telecommunication Systems Uniform Resource Locater eXtensible Markup Language
58