Transcript PowerPoint 簡報

校園無線網路技術與應用發展
Sheng-Tzong Cheng
鄭憲宗
2015/7/17
[email protected]
http://plato.iie.ncku.edu.tw
06-2757575 ext. 62529
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Outline
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無線區域網路 ─ IEEE 802.11
無線應用通訊協定 ─ WAP
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無線區域網路通訊協定
Wireless Local Area Network
(IEEE 802.11)
2015/7/17
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無線區域網路標準-IEEE
802.11
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Specifies a single Medium Access Control (MAC)
sublayer and 3 Physical Layer Specifications.
Stations can operate in two configurations :
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Three PHY specifications
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Ad-hoc mode
Infrastructure mode
Frequency Hopping Spread Spectrum (FHSS).
Direct Sequence Spread Spectrum (DSSS).
Infrared PHY.
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IEEE 802.11規範
Application Layer
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IEEE Project 802 Charter:
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Local & Metropolitan Area Network
1Mbps to 100Mbps and higher
2 lower layers of 7 Layer OSI
Reference Model
IEEE 802.11 Working GroupData
Link
scope:
Layer
Wireless connectivity for fixed,
portable and moving stations within
a limited area
 Appear to higher layer (LLC) the
2015/7/17same as existing 802 standards
.
.
.
Network Layer
LLC
MAC
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IEEE
802.11
Physical Layer
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IEEE 802.11架構
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1997/6/26通過成為IEEE 802系列標準
Logical Link Control
Media Access Control
Infrared
Physical Layer
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FHSS
Physical Layer
DSSS
Physical Layer
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Ad Hoc網路
• One Basic Service Set
• Directed Connection
• Limited Coverage Area
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Infrastructure網路
Existing
Wired LAN
Other
LANs
Distribution System
AP
AP
BSS
Basic
Service
Set
Extend Service Set
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Infrastructure網路 (cont.)
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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
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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
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Association service
Authentication service
Distribution service
Integration service
Deauthentication/Deassociation service
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Spread Spectrum Technology
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DSSS（Direct Sequence Spread Spectrum）
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FHSS（Frequency Hopping Spread Spectrum）
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11channels
PN-code長度為11-bit
展頻寬度為11MHz
78 hop sequences
頻帶範圍為1MHz，
跳頻的頻率為每秒2.5次
Infrared Ray
發展趨勢：DHSS往高速無線區域網路系統發展，適合辦
公室環境使用；FHSS會往低價網路應用發展，提供SOHO
及家庭應用、或周邊設備之無線網路連結。
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直接序列展頻（DSSS）
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跳頻展頻（FHSS）
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IEEE 802.11 TGa
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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.)
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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
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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 coexistence 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)
3.
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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1.
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Hidden Terminal Problem
data
A
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B
data
C
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Solution to HTP
Request
A
B
C
Grant
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Detection of Collision
Request
A
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B
Request
C
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Collision Avoidance
D
Request
A
A is Grant
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B
C
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
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Backoff time = INT(CW *
Random())*aSlotTime
INT(x) : 小於或等於x的最大整數
CW(contention window parameter ) : 介於
CWmin和Cwmax間的整數 , CW依序遞增的順
序為(7,15,31,63,127,255,255,255……)
Random() : 介於0到1間的實數
aSlotTime : 傳送器開啟延遲 + 媒介傳遞延遲
+ 媒介忙碌偵測反應時間
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An example of exponential
increase of CW
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Backoff procedure
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Transmission of a multifragment 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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無線區域網路軟體技術架構
Network
Applications
WLAN
Management
Utility
File
Transfer
E-Mail
Mobile IP
SNMP
Agent
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Security
Mobile
Data
Distributed
Service
Socket Interface
Network Driver (NDIS)
Embedded
Control
Software
WLAN
Platform
Remote
Access
Media Access Control
U-NII or ISM band
DSSS
FHSS
ETSI
DECT
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無線應用通訊協定
Wireless Application Protocol
(WAP)
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無線上網趨勢
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日本NTT的DoCoMo 於2/1999推出無線上網服務，
一年內累積3百萬用戶，每週增加10萬人
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WAP Forum於1997年成立，至1999年12月全世界
有200家無線通訊事業成為會員(95%市場之相關業
者投入)
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1999年，WAP是手機使用者最熱門話題之一
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無線上網趨勢
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(續)
1999年在台灣銷售180萬隻手機前兩大廠─ Motorola
於 2000上半年WAP手機佔40% ，下半年100%投入；
Nokia 則佔30%。
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國內新上市的手機六到七成內建WAP功能
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台灣已超過1000萬人有行動手機，而PC上網人數約
3至4百萬
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語音：數據─95% : 5% (2000) ; 40% : 60% (2005)
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全球無線通訊用戶成長
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預估未來WAP手機的佔有率
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手持型元件之延革
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What’s WAP for?
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bring the internet content and advanced
services to 後PC 時代之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?
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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
Wired Internet
HTML
JavaScript
HTTP
Wireless Network
Application
Layer
Wireless Application
Environment (WAE)
Wireless Transaction
Protocol (WTP)
Security
Layer
Transport
Layer
TCP/IP
UDP/IP
Network
Layer
Applications
Wireless Session
Protocol (WSP)
Session
Layer
Transaction
Layer
TLS - SSL
Other Services
and
Wireless Transport
Layer Security (WTLS)
Datagrams(UDP/IP)
Datagrams (WDP)
Wireless Bearers:
SMS
USSD CSD
IS-136 CDMA
IDEN
CDPD PDC-P
GPRS
WAP
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gateway
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Goals for WTP (WAP v1.1)
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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.)
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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
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WTP/ C provides a reliable connectionoriented service to the upper layer
WTP/ T provides a reliable transactionoriented service suitable for web browsing
WTP/ D provides a datagram service
lightweight : implementable in <= 10Kb
(low memory / computational needs)
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WTP/D features
(WDP in WAP v 1.2)
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WTP/ D (Datagram) provides a connectionless, unreliable datagram service
WTP/ D is replaced by UDP when used over
an IP network layer.
uses the Service Primitive
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T- UnitData. req .ind
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WAP v 1.2
Wireless Application
Environment (WAE
Other Services
and
)
Applications
Wireless Session
Protocol (WSP)
Wireless Transaction
Protocol (WTP)
Wireless Transport
Layer Security (WTLS)
Datagrams
(UDP/IP)
Datagrams
(WDP)
Wireless Bearers:
SMS
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USSD
CSD
IS -136
CDMA
IDEN
CDPD
PDC -P
GPRS
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WTP/T features
(WTP in WAP v 1.2)
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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.)
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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
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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 :
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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
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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
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4 record protocol clients:
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handshake protocol
change cipher spec protocol
alert protocol
application data protocol
WTLS connection state : the operating
environment for record protocol
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The
The
The
The
compression/ encryption algorithm
MAC algorithm -- keys
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Record Protocol Usage
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Handshake protocol
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Change cipher spec protocol
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Signal transitions in ciphering strategies
sent before verifying finished message
Alert protocol
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Negotiate secure attributes of a secure session
authentication, security parameter settings
convey the severity of the message and a description
of the alert
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Wireless Application
Environment
(WAE)
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An Internet (WWW) programming model
Vendor- controlled MMI
Initial focus on phones
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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
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Tag- based browsing language:
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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.)
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Card metaphor
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State management and variables
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Reduce network traffic
Results in better caching
Explicit inter- card navigation model
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User interactions are split into cards
Navigation occurs between cards
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Hyperlinks
UI Event handling
History
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WML Example
<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>
<card id="main">
<do type="accept">
<go href="#ecard"/>
</do>
<p>Welcome!</p>
</card>
<card id="ecard">
<do type="accept">
<go href="#ecard N=$(N);S=$(S)" />
</do>
<p>
Enter name: <input name="N"/>
speed:
<select name="S">
<option value="0">Fast</option>
<option value="1">Slow</option>
</select>
</p>
</card>
2015/7/17 </wml>
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WMLScript
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Scripting language:
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Derived from JavaScript™
Integrated with WML
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Procedural logic, loops, conditionals, etc.
Optimized for small- memory, small- cpu
devices
Powerful extension mechanism
Reduces overall network traffic
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WMLScript (cont.)
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Bytecode-based virtual machine
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Compiler in network
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Stack-oriented design
ROM-able
Designed for simple, low-impact
implementation
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
Push Overthe-Air
Protocol
Push
Access
Protocol
WAP Client
Push
Initiator
Push Proxy
Gateway
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WAP怎麼了？

歐洲在兩年內至少應有10億隻WAP手機，實際上只
有六百萬之使用量(according to IDC)
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T-Mobile:1% out of 1300萬人採購上網手機。1%
者有1/3從未上網，大部份人一週上網不到一次(北
歐情形較佳)
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影響WAP三大因素(訊通國際)：連線速度慢、通信
費用高、服務項目少
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WAP整體環境
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手機製造業
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電信系統業者
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ISP
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設備供應商
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網路軟體業者
 提供個人的、即時的、必須的資訊內容
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行動圖書館操作模式
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行動網路圖書館示意圖
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行動網路圖書館架構
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行動圖書館運作流程
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行動圖書館服務功能
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行動圖書館優點
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穩定強大的後端資料庫
友善使用者的DBA管理介面
跨平台執行之服務程式
充滿創意之各項行動圖書館服務
自行架設之WAP Gateway Server
伺服器皆採用開放原始碼之Linux作業系統
革命性跨介面存取的多元圖書館
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行動圖書館網頁範例
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Technology Support
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跨元件(介面)資訊存取
個人化資訊服務
智慧型資料傳輸
高效能執行平台
高可靠度系統支援
生物特徵辨識
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