6 CHAPTER 1.INTRODUCTION ·1995年，Gallager提出“Combining queueing theory with information theory for multiaccess;l9g8年，Ephremidus?发表了论文Information theory and commu- i2000 N.9 (Networ 和PR.K ion flo 文TeC 提出了传送容量 a tv的 腐念202后，研究正向若大规模网的信总理论发展T large networks) 1.5 A model of digital communication systems Channel encoder 信湖一→信湖编码洛 →EC的 数字方制器 Char 信道 ECC译码器 数字解器 symbols waveform Figure1.2:数字通信系统示意图 .source:discrete/continuous;memoryless/with memory encoder:convert the messages into the signal which is suitable for transmission over physical channels. .channel:wireless/cable,disk. ·interference,. ·sink:destination. 1.6 Review of Probability Baves rule: P(AIB)=P(AOB)=P(BIA)P(A) P(B) P(B) For a discrete random variable(r.v.), Probability Mass Function (PMF) Px(x)=P(X=z) denotes the Prob.of the event that X takes on the value For a continuous r.v. 6 CHAPTER 1. INTRODUCTION • 1995年，Gallager提出“Combining queueing theory with information theory for multiaccess”; 1998年，Ephremidus发表了论文“Information theory and commu￾nication networks: An unconsummated union”; 2000年，R. Alshwede, N. Cai, S.-Y. R. Li, and R. W. Yeung发表了著名论文“Network information flow”,提出 了网络编码(Network coding)的思想; 2000年，P. Gupta和P. R. Kumar发表了论 文“The Capacity of wireless networks”，提出了传送容量(Transport capacity)的 概念；2003之后，研究正向着大规模网络的信息理论发展（Towards an IT of large networks）。 1.5 A model of digital communication systems 信源 信源编码器 ECC 编码器 数字调制器 信 道 干 扰 信宿 信源译码器 ECC 译码器 数字解调器 调制信道 Channel decoder n(t) bits Channel encoder symbols waveform Figure 1.2: 数字通信系统示意图 • source: discrete/continuous; memoryless/with memory • encoder: convert the messages into the signal which is suitable for transmission over physical channels. • channel: wireless/cable, disk. • interference. • sink: destination. 1.6 Review of Probability Bayes rule: P(A|B) = P(A ∩ B) P(B) = P(B|A)P(A) P(B) For a discrete random variable (r.v.), • Probability Mass Function (PMF) PX(x) = P(X = x) denotes the Prob. of the event that X takes on the value x. For a continuous r.v