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:...

無線網路無線網路 (1)(1)長庚大學資訊工程所陳仁暉

Tel : (03) 211-8800 ext. 5990

E-mail: [email protected]

CGU NDSLCGU NDSL LAN-LAN-22

Outline

Midterm Exam 30% Final Exam 30% Presentation 40%


Course Outline Wireless PAN

IEEE 802.15.1 (Bluetooth) IEEE 802.15.2 (Ultra-Wide Band, UWB) IEEE 802.15.4 (ZigBee)

Wireless LAN IEEE 802.11a/b/g/n (Wi-Fi)

Wireless MAN IEEE 802.16d/e/j (WiMAX, BWA)

Wireless Networks Research Issues Routing Protocol Enhancement QoS Transmissions


Introduction to Local Area Networks (LANs)


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.


Basic Requirements of a LAN

Data rate of 1 to 1000 Mbps Geographic distances spanning at most 1-5 km Ability to support several hundredseveral hundred independent devices Minimal dependenceMinimal dependence on any centralized components or

control EfficientEfficient use of shared resources, including the network

channel StabilityStability under high load FairFair access (bandwidth, delay) to the network by all devices ReliabilityReliability and good error characteristics EasyEasy installation, reconfiguration and maintenance Low costLow cost


LAN Components

Computers (Networking devices) Transmission System (Network Cards, Cabling)

傳輸媒介 :同軸電纜 , 雙絞線 , 光纖 , rad

io

工作站

工作站

工作站

工作站

工作站


LAN Extension

網路區段 1 網路區段 2訊號增益器訊號增益器


Network Topologies

Star Single Star (IEEE 802.12 100VG-AnyLAN, ATM) Multiple Star (Snowflake) (ATM)

Bus Single Bus (IEEE 802.3 CSMA/CD, IEEE 802.4 Token-Bus) Dual Bus (IEEE 802.6 DQDB)

Tree Ring

Single Ring (IEEE 802.5 Token Ring) Dual Ring (FDDI, FDDI-II)

Mesh Random (IEEE 802.11 CSMA/CA)


Network Topologies

A C E

A

E

B

D

B D F

A

E

B

D

A

E

B

D

C E

B D

F

A

A B C

C C C

Star Ring Dual Ring

Bus Tree Dual Bus


Network Topologies

A B C

A B C D

A

C E

B

DF

Dual Bus

A

G

B

E

D

F

C

H

SnowflakeMesh

Dual Bus


Network Topologies

A

E

B

D

C F

J

G

I

H

K

O

L

N

M

橋接器

橋接器橋接器

Bridged Ring Networks

C

A

BF

D

E

G

H

...

Hub, Switch or Concentrator

Wireless LAN ?Wireless LAN ?


Open System Interconnection (OSI) Model

Physical LayerPhysical Layer. Responsible for transmission of bit streams across a particular physical transmission medium. Retransmission is not supported.

Encoding/Decoding Scrambling/Descrambling

Data Link LayerData Link Layer. Responsible for providing reliable data transmission from one node to another. Provides error-free transmission of frames.

Network LayerNetwork Layer. Concerned with routing data from one network node to another. Provides routing path selection.

Establishing/Maintaining/Terminating network connection Transport LayerTransport Layer. Responsible for providing data transfer between two

end users at an agreed on level of quality. Establishing/Maintaining/Terminating transport layer connection


Open System Interconnection (OSI) Model

Session LayerSession Layer. Providing services used to organize and synchronize the dialog that takes place between users and to manage the data exchange.

Presentation LayerPresentation Layer. Responsible for the presentation of information to the network users.

Character code translation/ Data conversion Data compression/expansion Encryption/Decryption

Application LayerApplication Layer. Provides services to application processes or users. File Transfer Protocol (FTP) Remote Login (Telnet) Transaction Server Network Management WWW Server/VoD Server


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)


Layering Protocols

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用軟體 X 應用軟體 Y

系統 A 系統 B

鏈結層通訊協定

傳輸媒介

網路層通訊協定

傳輸層通訊協定

會議層通訊協定

表達層通訊協定

應用層通訊協定

實體層通訊協定


Basic Functions of Protocols

Encapsulation/Decapsulation Segmentation/Reassembly Connection Establishing Flow Control Error Control Multiplexing/Demultiplexing


Encapsulation/Decapsulation Mechanisms

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用軟體 X

AH

PH

SH

TH

NH

資料

資料

資料

資料

資料

資料

資料 F A C FCS F

位元串

通訊路徑

應用軟體 Y

往下送時訊框包裝往上送時訊框拆裝


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 ControlIEEE 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 IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access with Collision

DetectionDetection 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


IEEE Project 802 Standards IEEE 802.11 CSMA/CA Wireless LANIEEE 802.11 CSMA/CA Wireless LAN

IEEE 802.11a High-Speed Physical Layer in the 5GHz BandIEEE 802.11a High-Speed Physical Layer in the 5GHz Band IEEE 802.11b Higher-Speed Physical Layer Extension in the 2.4 GHz BandIEEE 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) – IEEE 802.11e Medium Access Control (MAC) Enhancements for Quality of Service (QoS) – Draft Draft

D2.0D2.0 IEEE 802.11f Inter-Access Point Protocol (IAPP) – IEEE 802.11f Inter-Access Point Protocol (IAPP) – Draft D3Draft D3 IEEE 802.11g IEEE 802.11g Further Higher-Speed Physical Layer Extension in the 2.4 GHz BandFurther Higher-Speed Physical Layer Extension in the 2.4 GHz Band – – Draft D2.1Draft D2.1 IEEE 802.11h Spectrum and Transmit Power Management extensions in the 5GHz band in EuropIEEE 802.11h Spectrum and Transmit Power Management extensions in the 5GHz band in Europ

e e -Draft D1.1-Draft D1.1 IEEE 802.11i IEEE 802.11i Enhanced SecurityEnhanced Security – – Draft D1.8Draft D1.8

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 IEEE 802.15 Wireless Personal Area Networks Access Method and Physical

Layer SpecificationsLayer Specifications IEEE 802.15.1 Wireless Personal Area Networks (Bluetooth)IEEE 802.15.1 Wireless Personal Area Networks (Bluetooth) IEEE 802.15.2 CoexistenceIEEE 802.15.2 Coexistence IEEE 802.15.3 WPAN Higher RateIEEE 802.15.3 WPAN Higher Rate IEEE 802.15.4 WPAN Low Rate (Zigbee)IEEE 802.15.4 WPAN Low Rate (Zigbee)

IEEE 802.16 Broadband Wireless Access Method and Physical Layer Specifications


IEEE Project 802 Standards

MACMAC

WLANWLAN

無線網路無線網路 (2)(2)

長庚大學資訊工程所陳仁暉

Tel : (03) 211-8800 ext. 5990E-mail: [email protected]


IEEE 802.3

Carrier Sense Multiple Access with

Collision Detection (CSMA/CD)


Typical CSMA/CD Network

A C E

B D F

同軸電纜收發器電纜

終端器

終端器

收發器


IEEE 802.3 Architecture

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

OSI 參考模式

媒介擷取控制邏輯鏈結控制 LLC (IEEE 802.2)LLC (IEEE 802.2)

MAC (IEEE 802.3)MAC (IEEE 802.3)

PLS實體層訊號處理

高層通訊協定 (IP, TCP, HTTP,

FTP, SMTP, etc.,)

CSMA/CD

傳輸媒介

PMA MAUAUI

MDI


CSMA/CD Protocol

Carrier SenseCarrier Sense beforebefore transmission Carrier SenseCarrier Sense whilewhile transmission CollisionCollision: Two or more stations transmitting simultaneo

usly BackoffBackoff: Random delay after collision DeferenceDeference: Defers transmission if channel is sensed bus

y Collision WindowCollision Window (Slot timeSlot time): Round-trip propagation

delay time plus some carrier sense time. In IEEE 802.3, this value is defined to be 51.2 us51.2 us.


CSMA/CD Collision Handling

Collision Signal is generated by Physical layer. Jam signalJam signal (collision enforcement): To make sure that all stati

ons involved in the collision will detect collision. A pattern of 32 bits.

Collision backoff and retransmission method (Truncated Bina(Truncated Binary Exponential Backoff Algorithm, BEBAry 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 effectLast-in-First-out effect: Stations with no or few collisions will have a better chance to transmit before stations that have waited longer.


IEEE 802.3 Frame Format

Preamble SFD DA SA LEN LLC PAD FCS

7 1 2, 6 2, 6 2 4 位元組

I/G

I/G U/L

15- 位元地址

46- 位元地址

I/G = 0 Individual Address （個別地址）I/G = 1 Group Address （群體地址）U/L = 0 Globally Administered Address （整體性地址）U/L = 1 Locally Administered Address （區域性地址）

Preamble: (101010...1010) for Synchronization SFD: Start Frame Delimiter (10101011) DA: Destination Address SA: Source Address Length: Length of LLC-Frame LLC-Frame: Up to 15001500 bytes PAD: Padding when LLC-Frame < 46 46 bytes FCS: Frame Check Sequence (CRC-32) MAC-frame size -- from DA to FCS

Min 64 bytesMin 64 bytes to distinguish from collision Max 1518 bytesMax 1518 bytes to prevent dominating bandwidth


Flow Chart

傳送訊框

組成訊框 , i=1

線上有訊號

傳送訊框

發生衝撞送出擾亂訊號

傳送完畢

i > 16

Y

Y

Y

N

N

N

N

Y

i = i + 1

計算延遲時間

等待延遲時間

傳送成功傳送失敗

接收訊框

開始接收

接收完畢

訊框過短（衝撞）

位址辨識成功

Y

Y

N

N

Y

訊框錯誤接收成功

檢查碼正確

尚有多餘位元

對齊錯誤

長度欄位內容正確

刪除訊框頭尾

長度錯誤

Y

Y

N

N

Y

N


Collision Detection Window for Baseband CSMA/CD (=2a)

BA

a = 0.5, 傳輸時間＝ 1

t0

BA

t0+a-e

BA

t0+a

BA

t0+2a-e

衝撞

Ａ開始傳送訊框

Ｂ開始傳送訊框

Ｂ偵測出衝撞

Ａ偵測出衝撞


Network Configuration(Single segment)

同軸電纜區段（最長 500 公尺）

（每區段最多接 100 個）

A C E

B D F

同軸電纜收發器電纜

終端器

終端器

收發器

（最長 50 公尺）


Network Configuration (Two segments)

D

B C A

第一段同軸電纜


第二段同軸電纜

G H I

FE


收發器電纜（最長 50 公尺）

訊號增益器


Network Configuration (Five segments, maximum)

C

A

B

F

D

E

G H

J

K

I

N

L

M

訊號增益器

半訊號增益器

半訊號增益器間電纜（最長 1000 公尺）區段 4

區段 1區段 2

區段 3

區段 5

1

2

3

4

5

6

Remind :Remind :

Slot Time = 51.2 usSlot Time = 51.2 us


Alternative Physical Layers

資料傳輸速率

參數 10BASE5 10BASE 2 1BASE5 10BASET 10BROAD36

傳輸媒介同軸電纜（ 50 歐姆）

同軸電纜（ 50 歐姆）

同軸電纜（ 75 歐姆）

無遮蔽式雙絞線

無遮蔽式雙絞線

訊號處理技術基頻

（Manchester）寬頻

（ DPSK）

1 Mbps10 Mbps 10 Mbps 10 Mbps 10 Mbps

每段最大長度 185 公尺500 公尺 185 公尺500 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

每段最多可連接工作站數目工作站間距電纜線直徑

100 30

2.5 公尺 0.5 公尺

10 公厘 5 公厘 0.4-0.6 公厘 0.4-0.6 公厘

基頻（Manchester）



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:...

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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:...