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<>1并行传输的特点:距离短,速度快。
串行传输的特点:距离长,速度慢
所以在计算机内部传输应选择并行传输
<>2曼彻斯特编码既传输时钟信号也传输数字信号
<>3非归零编码不包含同步信息
<>4波特率等于信号每秒变化的次数
<>5曼彻斯特编码20baud相当于10b/s
<>6比特率等于波特率乘以每码元所含比特数
离散值个数等于2的n次方,n为每码元所含比特数
<>7无噪音通道超过2W则没有意义
<>8数据传输速率既受到奈奎斯特定理限制,也受到香农定理限制
<>9波特的数据传输速率取决于log2n
相位振幅等于变化
如果题目中给出的是波特率,那么直接用波特率log2n即可,如果题目中给出的是带宽,那就需要要奈奎斯特定理
<>10电路交换建立连接时间长,通信时延小;
电路交换不会在存储转发浪费时间
<>11报文交换不能用于实时通信
分组交换相对于报文交换,传输单位更小而且有固定的最大长度,这降低了传输时延
<>12分组交换分为有连接的虚电路和无连接的数据报(由网络层提供)
虚电路分为两种,既包括临时性的也包括永久性的
<>13交换机转发的延迟等于主机发送的延迟