CSC8530: Distributed Systems
Paul Schweitzer
March 28, 2000

Wireless Application Protocol

Terminology

CDMA - (ITU IS-95) Code Division Multiple Access
CDMA 2000 = ITU IS-136
CDPD - Cellular Digital Packet Data
CTIA - Cellular Telecommunications Industry Association
CSD - Circuit Switched Data
ETSI - Europe Telecommunications Standards Institute
HTTP-NG - HyperText Transport Protocol Next Generation
HTML-NG - HyperText Markup Language Next Generation
HDML - Handheld Device Markup Language
HDTP - Handheld Device Transport Protocol
GSM - Global System for Mobile Communications
GPRS - General Packet Radio Service
IETF - Internet Engineering Task Force
IMT-2000 = 3G International Mobile Telecommunication 2000
ITU - International Telecommunications Union
MExE - Mobile Execution Environment (Mobile Group 4)
PDC-P - Personal Digital Cellular Phone
PDA - Personal Digital Assistant
SMS - Short Message Services
TIA - Telecommunications Industry Association
TDMA - Time Division Multiple Access
USSD - Unstructured Supplementary Service Data (channel)
UMTS - Universal Mobile Telecommunication Services
WAP - Wireless Application Protocol
WAE - Wireless Application Environment
WBXML - Wireless Binary eXtnesible Markup Language
WDP - Wireless Datagram Protocol
WML - Wireless Markup Language
WSP - Wireless Session Protocol
WTP - Wireless Transaction Protocol
WTLS - Wireless Transport Layer Security
WTA - Wireless Telephony Application
W3C - WWW Consortium
XSL - Exstensible Style Language
XML - Exstensible Markup Language

Overview

The Wireless Application Protocol is designed as a comprehensive and scalable protocol developed for use with:

Any existing or planned wireless services such as SMS, CSD, USSD, and GPRS.
Any mobile phone from those with a one line display to a smartphone.
Any mobile network standard such as CDMA, GSM, UMTS. WAP has been designed to work with all cellular standards and is supported by world-wide wireless leaders such as AT&T Wireless and NTT DoCoMo.
Multiple input terminals such as keypads, keyboards, touch-screens and stylus

WAP takes a client server approach. It put the intelligence in WAP Gateways while adding just a microbrowser to the mobile phones, requiring only limited resources. Microbrowser services and applications reside temporarily in servers, not permanently in phones. WAP is aimed at turning a mass-market mobile phones into network-based smartphones.

WAP Forum was founded in June of 1997. The following companies are founding members:
    1. Motorola
    2. Nokia
    3. Ericsson
    4. Phone.com (formerly Unwired Planet)

WAP Forum market requirements:

Ease of use
Market size
Price sensitivity
Usage patterns
Essential tasks

The WAP Forum has the following goals:

To bring Internet content and advanced data services to wireless phones and other wireless terminals.
To enable the creation of content and applications that scale across a wide range of wireless bearer networks and device types.
To create a global wireless protocol specification that works across all wireless network technologies.
To embrace and extend existing standards and technology wherever possible and appropriate.

The WAP Forum does not develop products, but instead creates license-free standards for the entire industry to use to develop products. Each company's product line can then offer its own unique features, while still conforming to the WAP specification. Since the WAP Forum is not a handset manufacturer, voicemail vendor, or infrastructure provider, all companies in the telecommunications industry are assured that they are not competing with WAP, because WAP does not promote any particular product or product line. Instead, the WAP Forum promotes and supports all companies that are developing products based on the WAP specification and
how data should be transmitted over the air interface. The WAP specification is intended to sit on top of existing bearer channel standards so that any bearer standard can be used with the WAP protocols to implement complete product solutions.

WAP Architecture

Wireless Application Environment

WML Microbrowser
WMLScript Virtual Machine
WMLScript Standard Library
Wireless Telephony Application Interface
WAP Content Types

Wireless Protocols

WSP - Wireless Session Protocol
WTLS - Wireless Transport layer Security
WTP - Wireless Transaction Protocol
WDP - Wireless Datagram Protocol
Wireless network interface definitions.

Why WAP?

WAP enables any data transport

TCP, UDP, IP4 (IPV6 soon) , SMS, USSD

WAP utilizes standard Internet markup languages (i.e. XML)
WAP utilizes plain Web HTTP 1.1 servers

leveraging existing development methodologies
CGI, ASP, NSAPI, JAVA, Servlets, PHP3, etc.
all WML content is accessed via HTTP 1.1 requests

WAP is actively working with the W3C and IETF

HTML-NG
HTTP-NG

ETSI / WAP compliance profile for GSM and UMTS

WAP architecture development issues

End-to-end security
Billing
Asynchronous Applications
Bearer channel selection
Gateway switching
PUSH requirements
Wireless Telephony Application Delayed
Lack of Cookies for Session Management
Premature Encryption Endpoint
Small Downloadable Unit Size

Less bandwidth
More latency
Less connection stability
Less predictable availability

WAE development

WML

Tag-based browsing language:

Screen Management (images and text)
Data input (selection lists, text, etc.)
Hyperperlinks and navigation support

W3C XML-based language
Inherit tools from HDML and HTML
Card metaphor

User interactions are split into cards
navigation occurs between cards

Explicit inter-card navigation model

Hyperlinks
UI Event handling
History

State management and variables

Reduce network traffic
Results in better caching

Task Binding Rules

User actions are defined at three levels

Deck
Card
Anchored links & select list options i.e. ACCEPT

When tasks are bound to an action at different levels the action with narrower scope takes precedence
Default task bindings

User Action (ACCEPT, PREV, others)
Task (PREV, NOOP)

Wireless Session Protocol

Provides Application Layer (of WAP) with interface for two session services.

1. connection oriented service that operates above WTP
2. connectionless service that operates above WDP (secure or non secure)

WSP consists of services suited for browsing applications (WSP/B)
Enhancements for WAE, wireless networks and low-end devices

Compact encoding (over the air)
Long lived session state
Session suspend and resume with session migration
Push (common facility)
Efficient protocol feature negotiation
Provide mechanisms based on HTTP 1.1

Wireless Transaction Protocol

Provides light-weight transaction-oriented protocol for "thin" client (mobile) implementations suitable to operate over networks with low-med BW.
Three classes of transaction service:

Unreliable one-way requests
Reliable one-way requests
Reliable two-way request-reply transactions

PDU delayed acknowledgement
Asynchronous transactions
Opportunity for optional features (i.e. OOB ACKS)
Advantages: Operator perspective -

Load more subscribers on the the same network due to reduced BW utilization.
Individual User - performance is improved and cost is reduced.

Wireless Transport Layer Security

Based on SSL
Optimized for use over narrow-band comm. channels
Features:

Data Integrity (ensure data is unchanged)
Privacy (ensure transmitted data is secure)
Authentication (facilitate client - application server validation)
DoS protection (makes typical denial-of-service attacks harder to accomplish, therefore protecting upper layer protocols)

Wireless Datagram Protocol

Transport Layer protocol
Provides a connection-less, unreliable datagram server
Operates above the data capable bearer services
WDP is replaced by UDP when used over an IP network layer

WDP over IP is UDP/IP

leftmost stack - typical

middle stack - applications that require transaction services

rightmost stack - applications that only require datagram transport

Summary

WAP is a protocol suite that endures many dependencies and development issues. It would appear that the benefits would be rewarding especially for the demanding mobile users, but it remains apparent that wireless digital services are not robust at every geographical area. There are many promising implementations to support services and lower layer protocols, making it more access transparent to the applications. As a result, wireless technology will make a big impact when it becomes fully reliable and provides satisfactory performance. There are more future implementation issues to be resolved. For example:

QOS of WAP stack
Wider scope of security architecture
Support for multicast data
Downloadable applications
Compression
Downloadable WMLScript libraries
Additional integration with telephone network
Others

For current updates of approved WAP specifications: http://www.wapforum.org/what/technical.htm

Success Stories

MeritaNordbanken introduced WAP equity trading
MeritaNordbankens WAP banking services continue to expand. From January 31 th MeritaNordbanken customers in Finland have been able to buy and sell securities over their WAP telephone. MeritaNordbanken customers were in October 1999 the first in the world to handle their banking business via WAP phones.

MITSUBISHI ELECTRIC AND PHONE.COM ANNOUNCE WAP INTEROPERABILITY TESTING
PARIS, France and REDWOOD CITY, Calif. (February 24, 2000) - Mitsubishi Electric, one of the worlds leading manufacturers of mobile handsets, and Phone.com, Inc. (Nasdaq: PHCM), a leading provider of mobile Internet software and services, announced today that they have initiated a project to verify the interoperability between their products. Wireless Application Protocol (WAP) interoperability tests will be conducted between Phone.coms UP.Link Server and Triums Geo-@ (WAP) from Mitsubishi Electric France.

PHONE.COM ANNOUNCES NEW E-COMMERCE AND AUTOMATED PROVISIONING FEATURES FOR UP.LINK SERVER RELEASE 4.2
New features enable operators to facilitate and take part in e-commerce transactions and simplify WAP provisioning
NEW ORLEANS, CTIA Wireless 2000 (February 28, 2000) - Phone.com, Inc. (Nasdaq:PHCM), a leading provider of WAP-based mobile Internet software and services, today announced that it expects to begin shipping the UP.Link Server Suite Release 4.2 during early 2nd quarter 2000. With this release, Phone.com continues its commitment to provide leading edge, WAP-compliant wireless Internet solutions

Q&A

Is WAP considered a Middleware product? Explain.
Has WAP provided any transparency? Explain.

References

http://www.handytel.com/technology/wap01.htm
http://www.wapforum.com
http://www.ericsson.se/developerszone/#
http://virtuacom.com/wap/
http://www.wap.net/