本节讨论4个问题 1、通信的方式； 2、多路复用技术； 3、数据的分类； 4、数据的编码；

1. 通信与通信系统的基本概念 2. 无线通信

Fundamental aspects of network Design and Analysis: – Architecture Layering Topology design – Protocols Pt.-to-Pt. Multiple access End-to-end

Responsible for reliable transmission of packets over a link – Framing: Determine t he star t and end of packets (sec 2.5) – Error Detection: Determine w hen a packet contains errors (sec 2.3) – Error recovery: Retransmissio n of packets containing errors (sec 2..4)

Multiple Access Shared Transmission Medium a receiver can hear multiple transmitters a transmitter can be heard by multiple receivers the major problem with multi-access is allocating the channel between the users; the nodes do not know when the other nodes

RESERVATION SYSTEMS Single channel shared by multiple users Only one user can use t he channel at a time

DestinationAddress Output port number or VC number A packet switch consists of a routing engine (table look-up), a switch scheduler, and a switch fabric

Broadcast Routing Route a packet from a source to all nodes in the network Possible solutions: – Flooding: Each node sends packet on all outgoing links Discard packets received a second time – Spanning Tree Routing: Send packet along a tree that includes all of the nodes in the network

Routing Must choose routes for various origin destination pairs (O/D pairs) or for various sessions – Datagram routing: route chosen on a packet by packet basis Using datagram routing is an easy way to split paths – Virtual circuit routing: route chosen a session by session basis

一、数据编码类型及方法 二、基带传输及数据通信中的主要技术指标 三、频带传输与调制解调器原理 四、多路复用