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無線網路 (1)
長庚大學資訊工程所 陳仁暉
Tel : (03) 211-8800 ext. 5990
E-mail: [email protected]
Outline



Midterm Exam 30%
Final Exam 30%
Presentation 40%
CGU NDSL LAN-2
Course Outline

Wireless PAN




Wireless LAN


IEEE 802.11a/b/g/n (Wi-Fi)
Wireless MAN


IEEE 802.15.1 (Bluetooth)
IEEE 802.15.2 (Ultra-Wide Band, UWB)
IEEE 802.15.4 (ZigBee)
IEEE 802.16d/e/j (WiMAX, BWA)
Wireless Networks Research Issues



Routing
Protocol Enhancement
QoS Transmissions
CGU NDSL LAN-3
Introduction to
Local Area Networks (LANs)
CGU NDSL LAN-4
What is a LAN ?

A LAN is a data communication system
allowing a number of independent devices
to communicate directly with each other,
within a moderately sized geographic area
over a physical communications channel of
moderate data rates.
CGU NDSL LAN-5
Basic Requirements of a LAN










Data rate of 1 to 1000 Mbps
Geographic distances spanning at most 1-5 km
Ability to support several hundred independent devices
Minimal dependence on any centralized components or
control
Efficient use of shared resources, including the network
channel
Stability under high load
Fair access (bandwidth, delay) to the network by all devices
Reliability and good error characteristics
Easy installation, reconfiguration and maintenance
Low cost
CGU NDSL LAN-6
LAN Components


Computers (Networking devices)
Transmission System (Network Cards, Cabling)
工作站
工作站
傳輸媒介:
同軸電纜, 雙絞線, 光纖, radio
工作站
工作站
工作站
CGU NDSL LAN-7
LAN Extension
網路區段 2
網路區段 1
訊號增益器
CGU NDSL LAN-8
Network Topologies

Star



Bus






Single Bus (IEEE 802.3 CSMA/CD, IEEE 802.4 Token-Bus)
Dual Bus (IEEE 802.6 DQDB)
Tree
Ring


Single Star (IEEE 802.12 100VG-AnyLAN, ATM)
Multiple Star (Snowflake) (ATM)
Single Ring (IEEE 802.5 Token Ring)
Dual Ring (FDDI, FDDI-II)
Mesh
Random (IEEE 802.11 CSMA/CA)
CGU NDSL LAN-9
Network Topologies
C
A
E
Star
C
A
C
A
D
E
B
B
B
E
D
Ring
D
Dual Ring
A
D
B
F
D
B
A
A
C
Bus
E
C
E
Tree
B
C
F
Dual Bus
CGU NDSL LAN-10
Network Topologies
A
A
B
B
C
D
C
Dual Bus
Dual Bus
B
B
A
E
Mesh
A
D
H
E
D
F
C
C
F
G
Snowflake
CGU NDSL LAN-11
Network Topologies
G
B
橋接器
C
A
H
F
A
E
J
D
I
H
B
D
F
...
G
C
E
橋接器
橋接器
L
Hub, Switch or Concentrator
M
K
O
N
Wireless LAN ?
Bridged Ring Networks
CGU NDSL LAN-12
Open System Interconnection
(OSI) Model

Physical Layer. Responsible for transmission of bit streams across a
particular physical transmission medium. Retransmission is not
supported.




Data Link Layer. Responsible for providing reliable data transmission
from one node to another. Provides error-free transmission of frames.
Network Layer. Concerned with routing data from one network node
to another. Provides routing path selection.


Encoding/Decoding
Scrambling/Descrambling
Establishing/Maintaining/Terminating network connection
Transport Layer. Responsible for providing data transfer between two
end users at an agreed on level of quality.

Establishing/Maintaining/Terminating transport layer connection
CGU NDSL LAN-13
Open System Interconnection
(OSI) Model


Session Layer. Providing services used to organize and
synchronize the dialog that takes place between users and to
manage the data exchange.
Presentation Layer. Responsible for the presentation of information
to the network users.




Character code translation/ Data conversion
Data compression/expansion
Encryption/Decryption
Application Layer. Provides services to application processes or
users.





File Transfer Protocol (FTP)
Remote Login (Telnet)
Transaction Server
Network Management
WWW Server/VoD Server
CGU NDSL LAN-14
Open System Interconnection
(OSI) Model - Seven Layers
應用層 (Application Layer)
表達層 (Presentation Layer)
會議層 (Session Layer)
傳輸層 (Transport Layer)
網路層 (Network Layer)
鏈結層 (Data Link Layer)
實體層 (Physical Layer)
CGU NDSL LAN-15
Layering Protocols
系統 A
系統 B
應用軟體 Y
應用軟體 X
應用層
應用層通訊協定
應用層
表達層
表達層通訊協定
表達層
會議層
會議層通訊協定
會議層
傳輸層
傳輸層通訊協定
傳輸層
網路層
網路層通訊協定
網路層
鏈結層
鏈結層通訊協定
鏈結層
實體層
實體層通訊協定
實體層
傳輸媒介
CGU NDSL LAN-16
Basic Functions of Protocols






Encapsulation/Decapsulation
Segmentation/Reassembly
Connection Establishing
Flow Control
Error Control
Multiplexing/Demultiplexing
CGU NDSL LAN-17
Encapsulation/Decapsulation
Mechanisms
往下送時訊框包裝
往上送時訊框拆裝
應用軟體 X
應用層
AH
表達層
鏈結層
實體層
NH
F
A C
應用層
表達層
會議層
傳輸層
資料
TH
網路層
資料
資料
SH
傳輸層
應用軟體 Y
資料
PH
會議層
資料
網路層
資料
資料
位元串
FCS F
鏈結層
實體層
通訊路徑
CGU NDSL LAN-18
IEEE Project 802 Standards

IEEE 802.1 High Level Interface














IEEE 802.1D Local Bridge (Spanning Tree Algorithm)
IEEE 802.1G Remote Bridge
IEEE 802.1P Traffic Class Expediting and Dynamic Multicast Filtering
IEEE 802.1Q Virtual LANs
IEEE 802.1X Port Based Network Access Control
IEEE 802.2 LLC (Logical Link Control)
IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access with Collision
Detection
IEEE 802.4 Token-Bus
IEEE 802.5 Token-Ring
IEEE 802.6 DQDB (Distributed Queue Dual Bus)
IEEE 802.7 Broadband Technical Advisory Group
IEEE 802.8 Fiber Optic Technical Advisory Group
IEEE 802.9 Integrated Voice and Data LAN Working Group
IEEE 802.10 Interoperable LAN/MAN Security
CGU NDSL LAN-19
IEEE Project 802 Standards

IEEE 802.11 CSMA/CA Wireless LAN











IEEE 802.12 Demand-Priority (100VG-AnyLAN)
IEEE 802.13
IEEE 802.14 Standard Protocol for Cable-TV Based Broadband Communication
Network
IEEE 802.15 Wireless Personal Area Networks Access Method and Physical
Layer Specifications





IEEE 802.11a High-Speed Physical Layer in the 5GHz Band
IEEE 802.11b Higher-Speed Physical Layer Extension in the 2.4 GHz Band
IEEE 802.11e Medium Access Control (MAC) Enhancements for Quality of Service (QoS) – Draft
D2.0
IEEE 802.11f Inter-Access Point Protocol (IAPP) – Draft D3
IEEE 802.11g Further Higher-Speed Physical Layer Extension in the 2.4 GHz Band – Draft D2.1
IEEE 802.11h Spectrum and Transmit Power Management extensions in the 5GHz band in
Europe -Draft D1.1
IEEE 802.11i Enhanced Security – Draft D1.8
IEEE 802.15.1 Wireless Personal Area Networks (Bluetooth)
IEEE 802.15.2 Coexistence
IEEE 802.15.3 WPAN Higher Rate
IEEE 802.15.4 WPAN Low Rate (Zigbee)
IEEE 802.16 Broadband Wireless Access Method and Physical Layer Specifications
CGU NDSL LAN-20
IEEE Project 802 Standards
MAC
WLAN
CGU NDSL LAN-21
無線網路 (2)
長庚大學資訊工程所 陳仁暉
Tel : (03) 211-8800 ext. 5990
E-mail: [email protected]
IEEE 802.3
Carrier Sense Multiple Access with
Collision Detection (CSMA/CD)
CGU NDSL LAN-23
Typical CSMA/CD Network
B
收發器
D
F
終端器
同軸電纜
收發器電纜
A
C
E
終端器
CGU NDSL LAN-24
IEEE 802.3 Architecture
OSI參考模式
應用層
表達層
CSMA/CD
高層通訊協定
(IP, TCP, HTTP,
FTP, SMTP, etc.,)
會議層
傳輸層
網路層
邏輯鏈結控制
LLC (IEEE 802.2)
媒介擷取控制
MAC (IEEE 802.3)
實體層訊號處理
鏈結層
實體層
PMA
PLS
AUI
MAU
MDI
傳輸媒介
CGU NDSL LAN-25
CSMA/CD Protocol






Carrier Sense before transmission
Carrier Sense while transmission
Collision: Two or more stations transmitting simultaneously
Backoff: Random delay after collision
Deference: Defers transmission if channel is sensed busy
Collision Window (Slot time): Round-trip propagation delay
time plus some carrier sense time. In IEEE 802.3, this
value is defined to be 51.2 us.
CGU NDSL LAN-26
CSMA/CD Collision Handling



Collision Signal is generated by Physical layer.
Jam signal (collision enforcement): To make sure that all
stations involved in the collision will detect collision. A
pattern of 32 bits.
Collision backoff and retransmission method (Truncated
Binary Exponential Backoff Algorithm, BEBA):





n : number of collisions experienced (n <= 16)
k : Min (n,10) -- Truncation
r : Random delay time (unit: slot time) between 0 <= r < 2k
Slot time = 51.2 us.
Disadvantage of BEBA:

Last-in-First-out effect: Stations with no or few collisions will
have a better chance to transmit before stations that have
waited longer.
CGU NDSL LAN-27
IEEE 802.3 Frame Format









7
1
2, 6
2, 6
2
Preamble
SFD
DA
SA
LEN
4
LLC
PAD
位元組
FCS
Preamble: (101010...1010) for Synchronization
I/G
15-位元地址
SFD: Start Frame Delimiter (10101011)
DA: Destination Address
I/G U/L
46-位元地址
SA: Source Address
Length: Length of LLC-Frame
I/G = 0 Individual Address （個別地址）
LLC-Frame: Up to 1500 bytes
I/G = 1 Group Address （群體地址）
PAD: Padding when LLC-Frame < 46 bytes
U/L = 0 Globally Administered Address （整體性地址）
U/L = 1 Locally Administered Address （區域性地址）
FCS: Frame Check Sequence (CRC-32)
MAC-frame size -- from DA to FCS
 Min 64 bytes to distinguish from collision
 Max 1518 bytes to prevent dominating bandwidth
CGU NDSL LAN-28
Flow
Chart
Y
傳送訊框
接收訊框
組成訊框, i=1
開始接收
線上有
訊號
接收完畢
Y
N
傳送訊框
發生衝撞
訊框過短
（衝撞）
送出擾亂訊號
Y
傳送完畢
位址辨識
成功
i=i+1
N
Y
Y
i > 16
N
N
計算延遲時間
尚有多餘
位元
Y
傳送失敗
檢查碼
正確
Y
長度欄位
內容正確
N
Y
刪除訊框頭尾
等待延遲時間
傳送成功
Y
N
Y
N
N
N
訊框錯誤
對齊錯誤
接收成功
長度錯誤
CGU NDSL LAN-29
Collision Detection Window for
Baseband CSMA/CD (=2a)
a = 0.5, 傳輸時間 ＝ 1
t0
A
Ａ 開始傳送訊框
B
t0+a-e
Ｂ 開始傳送訊框
A
B
衝撞
t0+a
Ｂ 偵測出衝撞
A
B
t0+2a-e
A
Ａ 偵測出衝撞
B
CGU NDSL LAN-30
Network Configuration
(Single segment)
同軸電纜區段（最長 500 公尺）
（每區段最多接 100 個）
B
收發器
D
F
終端器
同軸電纜
收發器電纜
A
（最長 50 公尺）
C
E
終端器
CGU NDSL LAN-31
Network Configuration
(Two segments)
同軸電纜區段（最長 500 公尺）
B
A
C
第一段同軸電纜
收發器電纜 （最長 50 公尺）
D
訊號增益器
E
F
第二段同軸電纜
G
H
I
同軸電纜區段（最長 500 公尺）
CGU NDSL LAN-32
Network Configuration
(Five segments, maximum)
A
1
D
區段 1
區段 2
B
E
C
F
訊號增益器
2
H
G
3
區段 3
4
L
半訊號增益器
5
I
J
區段 4
K
Remind :
Slot Time = 51.2 us
半訊號增益器間電纜
（最長 1000 公尺）
區段 5
M
N
6
CGU NDSL LAN-33
Alternative Physical Layers
參 數
10BASE5
傳輸媒介
同軸電纜
（50 歐姆）
訊號處理技術
資料傳輸速率
10BASE 2
1BASE5
10BASET
10BROAD36
同軸電纜
（50 歐姆）
無遮蔽式
雙絞線
無遮蔽式
雙絞線
同軸電纜
（75 歐姆）
基頻
基頻
基頻
基頻
（Manchester） （Manchester） （Manchester） （Manchester）
寬頻
（DPSK）
10 Mbps
10 Mbps
1 Mbps
10 Mbps
10 Mbps
每段最大長度
500 公尺
185 公尺
500 公尺
185 公尺
1800 公尺
網路最大長度
2500 公尺
925 公尺
2500 公尺
500 公尺
3600 公尺
0.4-0.6公厘
0.4-0.6公厘
每段最多可連接
工作站數目
100
30
工作站間距
2.5 公尺
0.5 公尺
電纜線直徑
10 公厘
5 公厘
CGU NDSL LAN-34