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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