1、网络课后作业Chap.23.Television channels are 6 MHz wide. How many bits/sec can be sent iffour-level digital signals are used? Assume a noiseless channel.电视频道的带宽是6MHz。如果使用4级数字信号，则每秒钟可以发送多少位？假设电视频道为无噪声信道。4. If a binary signal is sent over a 3-kHz channel whose signal-to-noise ratio is 20dB, what i
2、s the maximum achievable data rate?如果在一条3kHz信道上发送一个二进制信号，该信道的信噪比为20dB，则最大可达到的数据传输率为多少？28.Ten signals, each requiring 4000 Hz, are multiplexed on to a single channelusing FDM. How much minimum bandwidth is required for the multiplexedchannel? Assume that the guard bands are 400 Hz wide.有10
3、个信号，每个都要求4000Hz，现在用FDM将它们复用在一条信道上。对于被复用的信道，最小要求多少带宽？假设防护频段为400Hz宽。43.Suppose that x bits of user data are to be transmitted over a k-hop path in apacket-switched network as a series of packets, each containing p data bits and hheader bits, with x >>p + h. The bit rate of the lines is b bp
4、s and the propagationdelay is negligible. What value of p minimizes the total delay?假定x位用户数据将以一系列分组的形式，在一个分组交换网络中沿着一条共有k跳到路径向前传输，每个分组包含p位数据和h位的头，这里x>>p+h。线路的传输率为b bps，传播延迟忽略不计。请问什么样的p值使总延迟最小？Chap.3 3.The following data fragment occurs in the middle of a data stream for whichthe byte-stuff
5、ing algorithm described in the text is used: A B ESC C ESC FLAGFLAG D. What is the output after stuffing?下面的数据片段发生数据流用于文本中所述的梯段字节填充算法 ︰ B ESC C ESC FLAGFLAG D.在填料后的输出是什么？5. A bit string, , needs to be transmitted at the data linklayer. What is the string actually transmitted after bit stu
7、用一个奇偶校验位为检查所有奇数位和第二的奇偶校验位。此代码的汉明距离是什么？17.A channel has a bit rate of 4 kbps and a propagation delay of 20 msec. Forwhat range of frame sizes does stop-and-wait give an efficiency of at least 50percent? 一个信道的位速率为4kbps，传输延迟为20ms。请问帧的大小在什么范围内，停-等协议才可以获得至少50％的效率？29. Fra
