目 錄

2.2 數據通信理論基礎 ·····················25

2.2.1 傅立葉分析 ····················25

2.2.2 尼奎斯特定理 ·················25

2.2.3 香農公式 ·······················26

2.3 傳輸介質 ·································26

2.3.1 有綫介質 ·······················27

2.3.2 無綫介質 ·······················30

2.4 編碼和傳輸 ······························34

2.4.1 數字-數字編碼 ···············34

2.4.2 模擬-數字編碼 ···············39

2.4.3 數字-模擬編碼 ···············40

2.4.4 模擬-模擬編碼 ···············45

2.5 傳輸技術 ·································45

2.5.1 多路復用技術 ·················46

2.5.2 同步控製技術 ·················49

2.5.3 壓縮和壓縮方法 ··············52

2.6 交換技術 ·································53

2.6.1 電路交換 ·······················53

2.6.2 存儲轉發 ·······················54

2.6.3 幾種交換方式的比較 ········58

2.7 流量控製技術 ···························58

2.7.1 停等協議 ·······················59

2.7.2 滑動窗口協議 ·················59

2.8 差錯控製技術 ···························61

2.8.1 奇偶校驗碼 ····················62

2.8.2 海明碼 ··························63

IV 網絡工程師考試輔導

2.8.3 CRC 碼 ·························66

2.8.4 差錯控製的基本方式 ········68

2.8.5 ARQ ·····························68

2.9 公用網絡和租用綫路 ··················71

2.9.1 公用網絡 ·······················71

2.9.2 租用綫路 ·······················71

2.9.3 其他網絡 ·······················72

2.10 物理層接口協議 ······················72

2.10.1 RS-232 簡介 ··················72

2.10.2 V.35 簡介 ·····················73

2.10.3 G.703/G.704 簡介 ···········74

2.10.4 USB 簡介 ·····················74

2.10.5 1394 接口簡介 ···············75

2.11 網絡設備 ·······························75

2.11.1 按邏輯功能劃分網絡設備 ··76

2.11.2 按體係結構劃分網絡設備 ···76