Wireless Internet Protocols
Design Considerations
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Small memory: Typical case: 128-512Kbytes RAM and 512K-1Mbytes ROM
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Low power CPU: Typical case: 1-10 MIPS class CPU for embedded systems
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Small display: Typical case: 50x30 dots, 100x72 dots, and 150x100 dots
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Restricted colors: Typical case: mono-color (black and white)
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Restricted character fonts: Typical case: only single font
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Restricted input method: Typical case: several control buttons and number
buttons (0-9)
Wireless Protocols
• I-mode (cHTML)
• Wireless Application Protocol (WAP)
• J2ME Clients
i-Mode
• First introduced in Japan in 1999
• Used by Pixo Internet Microbrowser
(Currently using version 2.1)
• Mime type is text/html for cHTML clients
(compact HTML)
• Capable of sending and receiving text
i-Mode can use the KVM
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Although I-Mode devices have their own built in browser, they
are capable of running Java applications through the KVM.
Advantages to i-Mode
• Bosts the most web sites and applications of
all the protocols
• Able to send e-mail as well as browse iMode web sites.
• Very little translation is required to convert
HTML sites into cHTML sites.
• Emerging support for color screen
Disadvantages to i-Mode
• Applications are currently concentrated in Japan
and Europe.
• Screen format is designed for Japanese characters,
so English words may wrap to next line. Need to
designate breaks in order to get nice word wraps.
• Basically a monopoly, users get charged on a per
packet download rate.
• Maximum packet send size is 500 bytes
3.2 Features of Compact HTML
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The Compact HTML is a subset of HTML 2.0, HTML 3.2 and HTML 4.0. The
major features which are excluded from Compact HTML, as follows.
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JPEG image
Table
Image map
Multiple character fonts and styles
Background color and image
Frame
Style sheet
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cHTML includes support for .gif images
Benefits of cHTML
• Ensures that small information devices will
be able to connect to the WWW.
• Maintains the advantage of HTML (i.e.
cHTML can be refered to by HTML
authoring tools).
• Servers can act as filter agents for cHTML
clients.
Wireless Application Protocol
Wireless application protocol (WAP) is an application environment
and set of communication protocols for wireless devices designed to
enable manufacturer-, vendor-, and technology-independent access
to the Internet and advanced telephony services.
Ericsson, Nokia, Motorola, and Unwired Planet founded the WAP
Forum in the summer of 1997 with the initial purpose of defining an
industry-wide specification for developing applications over wireless
communications networks.
Applications are written in wireless markup language (WML), which
is a subset of extensible markup language (XML)
WAP Connection
Advantages of WAP
• Standard HTML content cannot be effectively displayed on the smallsize screens of pocket-sized mobile phones and pagers.
• WAP utilizes binary transmission for greater compression of data and
is optimized for long latency and low bandwidth.
• WML and wireless markup language script (WMLScript) are used to
produce WAP content.
• The lightweight WAP protocol stack is designed to minimize the
required bandwidth and maximize the number of wireless network
types that can deliver WAP content.
Disadvantages to WAP
• Applications must be modified to create WML instead of
HTML.
• It does not provide a centralized solution.
• Developers have to handle all the processes associated
with recognizing the browser and providing suitable
content.
• It may be more difficult to customize content for specific
devices.
• Security “break” at WAP gateway. The encrypted
information is decrypted and then re-encrypted at the
gateway transition.
3-tier WAP architecture
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Applications appear the same from the user's perspective. The Web server,
though, gets content from an application server in XML. The Web server can
then transform the XML into WML or HTML, depending on the client.
J2ME client
• Targeting mobile devices, runtime of equivalent size to WAP 2.0 / imode 3.0 browser stacks
• Devices need 128K available memeory
• Designed for devices < 512K in memory
• MIDlets offer persistence, offline use
• Licensing of J2ME requires passing compatibility test suite
Java Packages
Advantages of MIDP
• Security [supports https protocol for end-to-end security]
• No gateways [lower costs, simpler testing, etc.]
• MIDlet GUI offers uniform behavior across devices
• Adopted by handset manufacturers and carriers globally (KVM will
run the same code on any device)
• MIDlet GUI components familiar to Swing developers
• Clients can download MIDlets over the wireless network.
Disadvantages of MIDP
• Slow loading
• All information must be “streamed” including .gif images.
• If a “User-Agent” field in the packet header is not set by
the client, then the server will not know the type of client it
is.
• Application will probably be split across the client and
server.
On the Horizon
• VoiceXML for MIDP devices: an XML speech recognition
and synthesis application.
• WTA (Wireless Telephony Application) interface: allows
applications to have links that initiate phone calls.
• WML script: burned into the devices memory, prevents
multiple downloads of commonly used routines.
• Qualcomm’s BREW (Binary Runtime Environment for
Wireless): introduced in Europe, accepts applications
written in Java/C/C++, supports virtual machines (i.e.
KVM), as well as Qualcomm’s Wireless Game Engine
(WGE).