Abstract
The Wireless
Application Protocol (WAP) is the world standard for presentation and delivery
of wireless information and telephony services on mobile phones and other
wireless terminals. Wireless devices represent the ultimate constrained
computing device with limited CPU, memory, battery life and simple user
interface. Wireless networks are constrained by low bandwidth, high latency,
unpredictable availability and stability. However most important of all
Wireless subscribers have a different set of essential desires and needs than
desktop or even internet laptop users.
WAP enabled
devices are companion products that will deliver timely information and accepts
transactions and enquiries when the user is moving around. WAP services provide
pin point information access and delivery when all the full screen environment
is either not available or not necessary. The WAP specification addresses these
issues by using the best of existing standards and developing new extensions
where needed. It enables industry participants to develop solutions that are air
interface independent, device independent, and fully interoperable. The WAP
revolution leverages the tremendous investment in Web Servers, Web Development
tools, Web Programmers and Web Applications while solving uique problems
associated with the wireless domain. It enables developers to use existing
tools to produce sophisticated applications that have an intuitive user
interface.
1.
Introduction
WAP bridges the gap between the mobile world and the
Internet as well as corporate intranets and offers the ability to deliver an
unlimited range of mobile value-added services to subscribers—independent of
their network, bearer, and terminal. Mobile subscribers can access the same
wealth of information from a pocket-sized device as they can from the desktop.
WAP is a global standard and is not controlled by any
single company. 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.. There are now over one hundred members representing
terminal and infrastructure manufacturers, operators, carriers, service
providers, software houses, content providers, and companies developing
services and applications for mobile devices.
WAP also defines a wireless application environment
(WAE) aimed at enabling operators, manufacturers, and content developers to
develop advanced differentiating services and applications including a
microbrowser, scripting facilities, e-mail, World Wide Web
(WWW)–to-mobile-handset messaging, and mobile-to-telefax access.
The WAP specifications continue to be developed by
contributing members, who, through interoperability testing, have brought WAP
into the limelight of the mobile data marketplace with fully functional
WAP–enabled devices (see Figure 1).
Figure 1. WAP–Enabled Devices
Based on the Internet model, the wireless device
contains a microbrowser, while content and applications are hosted on Web
servers.
2. Why WAP is necessary?
A.
Ease Of Use: -despite the fact that using a
desktop computer has become progressively easier over the last five years, a
wireless computing device must be dramatically easier to use than even simplest
desktop computer
These devices
are used by people who potentially have no desktop computing experience.
Further more they will often be used in dynamic environment where user is
engaged in multiple activities. Subscriber won’t be focused on their handset.
The way they are when they are sitting in front of a desktop computer.
Therefore the devices must be extremely simple and easy to use.
Application built for these
devices must there fore present the best possible user interface. For quick and
simple usage. There can be no installation script, complicated menu structure,
application errors, general protection faults or complicated key sequences such
as ‘Ctrl+Alt+Del’ or ‘Alt+Shift F5.’
B.
Market size: the growth and the size of the
wireless subscriber, market has been phenomenal. According to global mobile
magazines, there are more than 200 million wireless subscribers in the world
today. According to NOKIA there will be more than 1 billion wireless
subscribers by the year 2005. The wireless market is enormous; it can afford
and will demand optimized solution.
C.
Usage patterns: - subscribers expect wireless
data access to perform like the rest of their handset: the service should be
instantly available, easy to use and designed to be used for a few minutes at a
time. Hourglass icons telling subscribers to wait will not be acceptable.
D.
Essential Tasks: - they will have small,
specific tasks that need to be accomplished quickly. Subscribers will want to
scan email rather than read it all, or see just the top stock quotes of
interest.
3. The network
is different
Wireless
data network present a more constrained communication environment compared to
wired network because of fundamental limitations of power, available spectrum
and ability, wireless data network tend to have:
1)
Less Bandwidth
2)
More Latency
3)
Less Connection Stability
4)
Less Predictable Availability
Different
similarly, mass market, handheld devices present a more constraint computing
environment compared to desktop computer. Also because fundamental limitations
of battery life and form factor, mass market handheld devices tend to have:
1)
Less Powerful CPUs
2)
Less Memory(ROM/RAM)
3)
Restricted Power Consumption
4)
Smaller Displays
5)
Different input devices (e.g. a phone keypad, voice
input etc.)
4. 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 (e.g., Web
servers, XML tools, etc.). Optimizations 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.
Figure 2. WAP Programming
Model
WAP content and
applications are specified in a set of well-known content formats based on the
familiar WWW content formats. Content is transported using a set of standard
communication protocols based on the WWW communication protocols. A micro
browser in the wireless terminal co-ordinates the user interfaces and is analogous
to a standard web browser. WAP defines a set of standard components that enable
communication between mobile terminals and network servers, including:
Ø 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, e.g. call control functions.
Ø 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.
Ø 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.
Ø Standard communication protocols – WAP communication
protocols enable the communication of browser requests from the mobile terminal
to the network web server.
The WAP content types and
protocols have been optimized for mass market, hand-held wireless devices. WAP utilizes
proxy technology to connect between the wireless domain and the WWW. The WAP
proxy typically is comprised of the following functionality:
Ø 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).
Ø Content Encoders and Decoders – The content encoders
translate WAP content into compact encoded formats to reduce the size of data
over the network.
This infrastructure ensures
that mobile terminal users can browse a wide variety of WAP content and
applications, and that the application author is able to build content services
and applications that run on a large base of mobile terminals. The WAP
proxy allows content and applications to be hosted on standard WWW servers and
to be developed using proven WWW technologies such as CGI scripting.
While the nominal use of WAP will include a web
server, WAP proxy and WAP client, the WAP architecture can quite easily support
other configurations. It is possible to create an origin server that includes
the WAP proxy functionality. Such a server might be used to facilitate
end-to-end security solutions, or applications that require better access
control or a guarantee of responsiveness, e. g, WTA.
5. Architecture
of the WAP Gateway
Figure 3: Example WAP 1 Gateway
Wireless Datagram
Protocol (WDP) –
WDP is a general datagram service, offering a
consistent service to the upper layer protocols and communicating transparently
over one of the available underlying bearer services. This consistency is
provided by a set of adaptations to specific features of these bearers. This
thus provides a common interface to the upper layers that are then able to
function independently of the services of the wireless network.
Wireless
Transport Layer Security (WTLS) –
The WTLS layer is designed to provide privacy, data
integrity and authentication between two communicating applications. It
provides the upper-level layer of WAP with a secure transport service interface
that preserves the transport service interface below it. In addition, WTLS provides
an interface for managing (e.g., creating and terminating) secure connections.
It provides functionality similar to TLS 1.0 and incorporates additional
features such as datagram support, optimized handshake and dynamic key
refreshing.
Wireless Session
Protocol (WSP) –
WSP provides HTTP/1.1 functionality and incorporates
new features, such as long-lived sessions and session suspend/resume. WSP
provides the upper-level application layer of WAP with a consistent interface
for two session services. The first is a connection-mode service that operates
above the transaction layer protocol, and the second is a connectionless
service that operates above a secure or non secure datagram transport service.
HTTP Interface
The HTTP interface serves to retrieve WAP
content from the Internet requested by the mobile device. WAP content (WML and
WMLScript) is converted into a compact binary form for transmission over the
air (see Figure 4).
Figure 4. WAP Content in Compact Binary Form
The WAP
microbrowser software within the mobile device interprets the byte code and
displays the interactive WAP content (see Figure 5).
Figure 5. Mobile Device Display
6. Example WAP Network
The following is for illustrative purposes only. An
example WAP network is shown in Figure 7.
Figure 7. 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. For example, the HTML filter would translate HTML
into WML.
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.
6.1. Mobile-Originated Example of WAP Architecture
WAP will provide multiple applications, for business
and customer markets such as banking, corporate database access, and a
messaging interface (see Figure 6).
Figure 6. Messaging Interface
The request from the mobile device is sent as a URL
through the operator's network to the WAP gateway, which is the interface
between the operator's network and the Internet.
7. The Future of
WAP
The tremendous surge of interest and development in
the area of wireless data in recent times has caused worldwide operators,
infrastructure and terminal manufacturers, and content developers to
collaborate on an unprecedented scale, in an area notorious for the diversity
of standards and protocols. The collaborative efforts of the WAP Forum have
devised and continue to develop a set of protocols that provide a common
environment for the development of advanced telephony services and Internet
access for the wireless market. If the WAP protocols were to be as successful
as transmission control protocol- (TCP)/Internet protocol (IP), the boom in
mobile communications would be phenomenal. Indeed, the WAP browser should do
for mobile Internet what
Netscape did for the Internet.
As mentioned earlier, industry players from content
developers to operators can explore the vast opportunity that WAP presents. As
a fixed-line technology, the Internet has proved highly successful in reaching
the homes of millions worldwide. However, mobile users until now have been
forced to accept relatively basic levels of functionality, over and above voice
communications and are beginning to demand the industry to move from a fixed to
a mobile environment, carrying the functionality of a fixed environment with
it. Initially, services are expected to run over the well-established SMS
bearer, which will dictate the nature and speed of early applications. Indeed,
GSM currently does not offer the data rates that would allow mobile multimedia
and Web browsing. With the advent of GPRS, which aimed at increasing the data
rate to 115 kbps, as well as other emerging high-bandwidth bearers, the reality
of access speeds equivalent or higher to that of a fixed-line scenario become
evermore believable?. GPRS is seen by many as the perfect partner for WAP, with
its distinct time slots serving to manage data packets in a way that prevents
users from being penalized for holding standard circuit-switched connections.
8. WAP in the
Competitive Environment
Competition for WAP protocols could come from a
number of sources:
Ø Subscriber Identity Module (SIM) toolkit— The use of
SIMs or smart cards in wireless devices is already widespread and used in some
of the service sectors.
Ø
Windows CE— This is a multitasking, multithreaded operating
system from Microsoft designed for including or embedding mobile and other
space-constrained devices.
Ø
Java Phone™—Sun Microsystems is developing
PersonalJava™ and a Java Phone™ API, which is embedded in a Java™ virtual
machine on the handset. NEPs will be able to build cellular phones that can
download extra features and functions over the Internet; thus, customers will
no longer be required to buy a new phone to take advantage of improved
features.
The advantages that WAP can offer over these
other methods are the following:
- open standard, vendor independent
- network-standard independent
- transport mechanism–optimized for wireless
data bearers
- application downloaded from the server,
enabling fast service creation and
introduction, as opposed to embedded software
9. Conclusion
WAP provides a markup language and a transport
protocol that opens the possibilities of the wireless environment and give
players from all levels of the industry the opportunity to access an untapped
market that is still in its infancy.
The bearer-independent nature of WAP has proved
to be a long-awaited breath of fresh air for an industry riddled with multiple
proprietary standards that have suffocated the advent of a new wave of
mobile-Internet communications. WAP is an enabling technology that, through
gateway infrastructure deployed in mobile operator's network, will bridge the
gap between the mobile world and the Internet, bringing sophisticated solutions
to mobile users, independent of the bearer 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.
References
1)
“Computer
Networks” by Andrew S. Tanenbaum,
Fourth edition
