超星 - 第2章书面作业 - 查题吧

简答题

What is the difference between noise and interference?噪声和干扰之间的差异是什么？Answer:Interference: Interference disrupts a signal that travels over a channel and usually adds unwanted signals to the desired signal. Several famous interference examples include co-channel interference (CCI), also known as crosstalk, inter-symbol interference (ISI), and intercarrier interference (ICI).Noise: Noise is a random fluctuation of an analog signal, such as electronic noise,thermal noise, induced noise, impulse noise, and quantization noise. Noise interferes with receivers in retrieving data from the received signal. To compensate for the impact of noise on the transmitted data, we may either raise the signal power or lower the transmission bit rate. In addition, modulation techniques can be used because they are more robust against noise.

简答题

Explain what sdr (signal-to-data-ratio) and SNR (signal-to-noise-ratio) mean and how they can be used for evaluation.解释什么是sdr（信号数据比）和SNR（信号噪声比）?他们是被如何用于评估的？Answer:sdr(signal-to-data ratio): a ratio of the number of signal elements to the number of data elements. If sdr > 1, a signal may contain self-synchronization information. SNR (Signal-to-noise ratio): a ratio of the average of signal power to the average of noise power. It is a measure to limit the theoretical bit rate.

简答题

Compare the capability of high-frequency signals and low-frequency signals in straight-line propagation, reflection, refraction, and diffraction.比较高频信号和低频信号分别在直线传播、反射、折射和衍射的功能？Answer:Low-frequency signals can travel around the lower part of the atmosphere by ground propagation. They can travel with diffraction, refraction, reflection, or straight-line propagation.Higher-frequency signals can travel up to the ionosphere and reflect down to the earth by sky propagation. Most of them can also travel with refraction, diffraction, reflection, and straight-line propagation.Very high-frequency signals which are very unidirectional are transmitted from the source to the destination directly only by straight-line propagation.

简答题

1. Among unipolar NRZ-L, Polar NRZ-L, NRZ-I, and RZ, Manchester, differential Manchester, AMI, and MLT-3, which schemes have no issues on synchronization, baseline wandering, and DC components, respectively?Answer:With self-synchronization problem: unipolar NRZ-L, polar NRZ-L, polar NRZ-I, AMI, MLT-3With baseline problem: unipolar NRZ-L, polar NRZ-L, polar NRZ-IWith DC components problem: unipolar NRZ-L, polar NRZ-L, polar NRZ-IWithout self-synchronization problem: polar RZ, Manchester, differential ManchesterWithout baseline wandering problem: Manchester, differential ManchesterWithout or with very little DC components problem: polar RZ, Manchester, differential Manchester, AMI

简答题

8．使用单极性NRZ-L，极性NRZ-L，NRZ-I和RZ分别绘制以下数据流的波形。计算sdr值（信号-数据比率）和平均波特率。a. 101010101010b. 111111000000c. 111000111000d. 000000000000e. 111111111111

简答题

9．使用曼彻斯特和差分曼彻斯特方案绘制以下数据流的波形。计算sdr值（信号到数据的比例）和平均波特率。a. 101010101010b. 111111000000c. 111000111000d. 000000000000e. 111111111111

简答题

10．使用MLT-3方案绘制以下数据流的波形。计算sdr值（信号与数据的比率）和平均波特率。a.101010101010b. 111111000000c.111000111000d.000000000000e.111111111111

简答题

11．给定数据流的位速率为1 Mbps、2 Mbps或54 Mbps，计算使用BASK，BPSK，QPSK，16-PSK，4-QAM的BFSK 16-QAM和64-QAM调制的波特率。

简答题

12．给定波特率为8 kBd和64 kBd，计算BFSK, BASK, BPSK, QPSK, 16-PSK, 4-QAM, 16-QAM和64-QAM调制的比特率。

简答题

13．给定比特率56 kbps或256 kbps的数据流，如果将11-bit或13-bit Barker码用做PN码来扩展数据流，那么码片速度和处理增益为多少？

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