Sheng-Tzong Cheng

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?????????????
Sheng-Tzong Cheng ??? stcheng_at_mail.ncku.edu.tw
http//plato.iie.ncku.edu.tw 06-2757575 ext. 62529
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Outline

• ?????? - IEEE 802.11
• ???????? - WAP

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?????????? Wireless Local Area Network (IEEE
802.11)
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????????-IEEE 802.11

• Specifies a single Medium Access Control (MAC)
  sublayer and 3 Physical Layer Specifications.
• Stations can operate in two configurations
• Ad-hoc mode
• Infrastructure mode
• Three PHY specifications
• Frequency Hopping Spread Spectrum (FHSS).
• Direct Sequence Spread Spectrum (DSSS).
• Infrared PHY.

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IEEE 802.11??
Application Layer

• IEEE Project 802 Charter
• Local Metropolitan Area Network
• 1Mbps to 100Mbps and higher
• 2 lower layers of 7 Layer OSI Reference Model
• IEEE 802.11 Working Group scope
• Wireless connectivity for fixed, portable and
  moving stations within a limited area
• Appear to higher layer (LLC) the same as existing
  802 standards

. . .
Network Layer
LLC
MAC
Physical Layer
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IEEE 802.11??

• 1997/6/26????IEEE 802????

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Ad Hoc??

• One Basic Service Set
• Directed Connection
• Limited Coverage Area

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Infrastructure??
Other LANs
AP
Basic Service Set
Extend Service Set
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Infrastructure?? (cont.)

• Access Point and Mobile Station
• Distributed System Interconnect Multiple Cells
  via Access Points to form a single network
• Extends Wireless Coverage Area
• Multiple Basic Service Sets connected together
  form an Extended Service Set
• Allow Mobile Station to access fixed resource
• Support Roaming for Mobile Stations via Access
  Point
• Point Coordination Function, Power Management,
  Time Synchronization support through Access Point

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IEEE 802.11 Services

• Provides services with the following
  functionality roaming within a ESS, multiple
  data rates in BSSs and Power Management.
• The MAC protocol is Carrier Sense Multiple Access
  with Collision Avoidance (CSMA/CA)
• MAC services
• Association service
• Authentication service
• Distribution service
• Integration service
• Deauthentication/Deassociation service

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Spread Spectrum Technology

• DSSS(Direct Sequence Spread Spectrum)
• 11channels
• PN-code???11-bit
• ?????11MHz
• FHSS(Frequency Hopping Spread Spectrum)
• 78 hop sequences
• ?????1MHz,
• ????????2.5?
• Infrared Ray
• ????DHSS?????????????,?????????FHSS??????????,??
  SOHO???????????????????

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??????(DSSS)
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????(FHSS)
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IEEE 802.11 TGa

• The TGa is working on the high data-rate
  extension in the 5 GHz band, project 802.11a, was
  able to produce a new draft standard that has the
  support of at least 80 of the members.
• TGa is looking at a candidate for worldwide
  standardization!

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IEEE 802.11 TGa (cont.)

• The specifications of the Physical Layer
  encompass data rates from 6 Mbit/s up to 54
  Mbit/s, with 20 MHz spacing between adjacent
  channels.
• All implementations are required to support 6, 12
  and 24 Mbit/s. Optional extensions are for 9, 18,
  36, 48 and 54Mbit/s.
• The multi-rate mechanism of the MAC protocol
  ensures that all devices communicate with each
  other at the best data rate in the present
  channel.

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IEEE 802.11 TGb

• The TGb is working on the extension of the 1 and
  2 Mbit/s data rates in the 2.45 GHz band with 5.5
  and 11 Mbit/s has reached a technical compromise
  solution to improve the co-existence and
  interoperability characteristics between options.
  
• The multi-rate mechanism warrants that the 11
  Mbit/s operation can switch back to 5.5Mbit/s.
  Stations that are even further could switch back
  to the 2 and 1 Mbit/s capabilities of the DSSS
  modulation.

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CSMA/CD (LAN)

• Send data if the medium is sensed idle
• If collides with other host(s),
• then backoff for a random number of times
• Re-send data later

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Hidden Terminal Problem
data
data
B
A
C
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Solution to HTP
Request
B
A
C
Grant
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Detection of Collision
Request
Request
B
A
C
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Collision Avoidance
D
Request
B
A
C
A is Grant
A is Grant
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RTS/CTS/data/ACK and NAV setting
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Some IFS relationships and basic access method
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Random backoff time

• Backoff time INT(CW Random())aSlotTime
• INT(x) ?????x?????
• CW(contention window parameter )
  ??CWmin?Cwmax???? , CW????????(7,15,31,63,127,255,
  255,255)
• Random() ??0?1????
• aSlotTime ??????? ?????? ??????????

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An example of exponential increase of CW
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Backoff procedure
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Transmission of a multi-fragment MPDU using SIFS
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RTS/CTS with fragmented MSDU
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RTS/CTS with transmitter priority and missed
acknowledgment
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Direct data/ACK MPDU
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????????????
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???????? Wireless Application Protocol (WAP)
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??????

• ??NTT?DoCoMo ?2/1999????????,?????3????,????10??
• WAP Forum?1997???,?1999?12?????200???????????(95?
  ????????)
• 1999?,WAP?????????????

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?????? (?)

• 1999??????180????????- Motorola ?
  2000???WAP???40 ,???100??Nokia ??30?
• ??????????????WAP??
• ?????1000???????,?PC?????3?4??
• ????-95 5 (2000) 40 60 (2005)

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??????????
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????WAP??????
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????????
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Whats WAP for?

• bring the internet content and advanced services
  to ?PC ???users
• create a global wireless protocol to work across
  differing wireless network technologies
• enable applications to scale across a variety of
  transport options and device types

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What is defined in WAP?

• Micro-Browser
• Scripting to enhance MS capabilities
• WTA/WTAI for telephone functionality (e.g. call
  chains)
• Content Formats
• business card (vCard )
• calendar event (vCalendar )
• Layered Telecommunication Stack

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Comparison
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Goals for WTP (WAP v1.1)

• a common interface to physical transport
  mechanisms
• provide a port- based abstract interface to upper
  layer protocols
• allow applications designed independent from
  specific transports
• extensible to a variety of digital wireless
  networks and future transport options

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Goals for WTP (cont.)

• supports connection- oriented, transaction, and
  datagram modes
• optimize for narrow to medium bandwidth channels
• to be capable of implementation in a low memory
  footprint, suitable for standard or low- IQ
  handsets

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Requirements for WTP

• WTP/ C provides a reliable connection- oriented
  service to the upper layer
• WTP/ T provides a reliable transaction- oriented
  service suitable for web browsing
• WTP/ D provides a datagram service
• lightweight implementable in lt 10Kb (low
  memory / computational needs)

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WTP/D features (WDP in WAP v 1.2)

• WTP/ D (Datagram) provides a connection- less,
  unreliable datagram service
• WTP/ D is replaced by UDP when used over an IP
  network layer.
• uses the Service Primitive
• T- UnitData. req .ind

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WAP v 1.2
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WTP/T features (WTP in WAP v 1.2)

• WTP/ T (Transaction) provides reliable data
  transfer based on request/ reply paradigm
• no explicit connection setup or tear down
• data carried in first packet of protocol exchange
• seeks to reduce 3- way handshake on initial
  request

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WTP/T features (cont.)

• supports
• retransmission of lost packets
• selective- retransmission
• segmentation / re- assembly
• port number addressing (specific to WTP/ T)
• flow control
• message oriented (not stream)
• supports an Abort function for outstanding
  requests

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Wireless Session Protocol

• WSP/ B provides upper layers with session
  services and management
• WSP/ B Provides semantics and mechanisms based on
  HTTP 1.1
• WSP provides means to
• establish a reliable session from client to
  server
• agree on common level of protocol functionality
  by capability negotiation
• compact encoding
• suspend and resume

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WSP features

• HTTP 1.1 functionality
• Exchange of client and server session headers
• Interrupt mechanism for transactions in process
• Content Push from server to client
• Negotiation for multiple, simultaneous
  asynchronous transactions

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WTLS Record Protocol

• 4 record protocol clients
• The handshake protocol
• The change cipher spec protocol
• The alert protocol
• The application data protocol
• WTLS connection state the operating environment
  for record protocol
• compression/ encryption algorithm
• MAC algorithm -- keys

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Record Protocol Usage

• Handshake protocol
• Negotiate secure attributes of a secure session
• authentication, security parameter settings
• Change cipher spec protocol
• Signal transitions in ciphering strategies
• sent before verifying finished message
• Alert protocol
• convey the severity of the message and a
  description of the alert

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Wireless Application Environment (WAE)

• An Internet (WWW) programming model
• Vendor- controlled MMI
• Initial focus on phones
• Slow bearers
• Small memory
• Limited CPU
• Small screen
• Limited input model

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WAE Components

• Architecture
• Application model
• Browser, Gateway, Content Server
• WML (Wireless Markup Language)
• Display language
• WMLScript
• Scripting language
• Content Formats
• Data exchange

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WAE In- Device Architecture
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WML

• Tag- based browsing language
• Screen management (text, images)
• Data input (text, selection lists, etc.)
• Hyperlinks navigation support
• Syntax W3C XML (SGML derivative)
• Inherits technology from HDML and HTML

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WML (cont.)

• Card metaphor
• User interactions are split into cards
• Navigation occurs between cards
• State management and variables
• Reduce network traffic
• Results in better caching
• Explicit inter- card navigation model
• Hyperlinks
• UI Event handling
• History

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WML Example
lt?xml version"1.0"?gt lt!DOCTYPE wml PUBLIC
"-//WAPFORUM//DTD WML 1.1//EN"
"http//www.wapforum.org/DTD/wml_1.1.xml"gt ltwmlgt
ltcard id"main"gt ltdo type"accept"gt ltgo
href"ecard"/gt lt/dogt ltpgtWelcome!lt/pgt lt/car
dgt ltcard id"ecard"gt ltdo type"accept"gt
ltgo href"ecard N(N)S(S)" /gt lt/dogt
ltpgt Enter name ltinput name"N"/gt
speed ltselect name"S"gt
ltoption value"0"gtFastlt/optiongt
ltoption value"1"gtSlowlt/optiongt
lt/selectgt lt/pgt lt/cardgt lt/wmlgt
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WMLScript

• Scripting language
• Procedural logic, loops, conditionals, etc.
• Optimized for small- memory, small- cpu devices
• Derived from JavaScript
• Integrated with WML
• Powerful extension mechanism
• Reduces overall network traffic

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WMLScript (cont.)

• Bytecode-based virtual machine
• Stack-oriented design
• ROM-able
• Designed for simple, low-impact implementation
• Compiler in network
• Better network bandwidth use
• Better use of terminal memory/ cpu

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WAP Gateway
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WAP Application Server
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WAP Push Technology
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WAP????

• ??????????10??WAP??,????????????(according to
  IDC)
• T-Mobile1 out of 1300?????????1??1/3????,??????
  ??????(??????)
• ??WAP????(????)?????????????????

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WAP????

• ?????
• ??????
• ISP
• ?????
• ??????
• ? ?????????????????

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???????

• ??????????
• ??????DBA????
• ??????????
• ??????????????
• ?????WAP Gateway Server
• ????????????Linux????
• ??????????????

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Technology Support

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