wireless application protocol - sns courseware
TRANSCRIPT
Wireless Application
Protocol
addresses issues higher up the protocol
stack
data links on wireless networks are
lower than wired networks
radio spectrum (bandwidth) limited
internet applications not designed with
wireless links in mind
wireless links less reliable
Wireless Application
Protocol cont.
wireless devices limited in power (batteries)
compromised features;
small keypad/keyboard
small display
limited data storage
standard IP cannot be used with mobile
devices efficiently - in some cases not
possible at all (800 x 600 page on a mobile in
true colour)
WAP
Packet Data
Infrastructure
WAP
Gateway
Internet
WAP IP
Applications:
Banking, e-
business, weather,
news
Cellular
(GPRS,
SMS)
Provides
translation
between WAP
and IP
Bluetooth technology
access
to LAN
cellular
networkmobile
phone
printer
laptop
laptop
mouse
2.4 GHz
Licence-free
Low Tx
power, low
cost, battery
operation
symmetric and
assymetric
connections
1600 frequency
hops per second
* replaces proprietary cables that
connect devices together *
Establishing a
connection
two units within range can set up a
connection (piconet)
share a channel
unit that initiates connection is master
other unit assumes role of slave
any unit can be a master or a slave
can only be one master in a piconet
Establishing a
connection cont.
before connection, each unit in standby
scanning frequencies every 1.28 secs
keeps power demands low
after initiation, full duty cycle implemented
communicates using 2.4 GHz wavelength
global compatibility
two bands available; 23 channels and 79
channels
selected by software depending on geography
Bluetooth Applications
automatic synchronisation of email, calendar,
telephone book, smartcard data
3-in-1 phone
home cordless phone - when in proximity of home
base unit
business cordless phone - use internal network
conventional cellular phone
cordless headset
mobile computer conferencing
automatic tolling - quite controversial!
WAP Technology
Massive growth in Internet usage
Rapid growth in mobile voice/data
services
Everyone has a mobile!
Data transfer rates limited
Key features
licence-free standard of adapting
internet technology to meet wireless
constraints
Wireless Markup Language (WML) for
authoring
optimised protocol stack based on
HTTP and TCP
usable over a broad range of cellular
data bearers
Architecture
HTML
JavaScript
HTTP
TLS SSL
TCP/IP
UDP/IP
Wireless Application Environment
(WAE)
Wireless Session Protocol (WSP)
Wireless Transaction Protocol (WTP)
Wireless Transport Layer Security (WTLS)
Wireless Diagram Protocol
(WDP)
User Datagram Protocol
(UDP)
Bearers: SMS, GPRS, 3G
etc.
WML
used
here
Internet Model
Web
ServerClient
Web Browser
IP Stack
CGI scripts
etc.
HTML,
JavaScript
The
Internet
HTTP Request (URL)
HTTP Response (HTML)
Internet Protocols
WAP Model
The
Internet
CGI scripts
etc.
WML,
JavaScript
Client WAP
GatewayWeb
Server
Wireless
Network
Encode/
decode
WAP user
agents
WAP
Protocol
stack
Protocol
conversion
WSP
Request
(URL)
HTTP
Request
(URL)
WSP
Response
(WML) HTTP
Response
(WML)
WAP Protocol Internet Protocol
What’s so special about
WAP?
WML is binary encoded so compact over
airwaves
Extensive use of caching during sessions to
minimise traffic
Handles data requests asynchronously
avoids waiting for responses before handling next
user request
Designed to hold ‘long’ sessions
session resumed at last point if radio link fails
WTP only sends broken packets of data
TCP always sends entire message again
Wireless device issues
Small display - WML structures docs in
‘decks’ and ‘cards’
card represents a single unit of interaction
with user
deck is a service, represented by a
collection of cards
well suited to small displays
Limited input - WML requires minimal
keyboard functionality