2014年宁波大学考博试题 3807数字通信 A

入学考试试题(A卷)(答案必须写在答题纸上)

考试科目:数字通信科目代码：3807

适用专业:通信与信息系统、信号与信息处理、移动计算与人机

交互、微纳信息系统

一、填空（16分）

1、数字通信系统的有效性指标有（）和（），可靠性指标有（）。

2、信道容量是信道无差错传输时的（）。

3、信道噪声通过一个带通滤波器后，将是一个（）噪声。

4、QAM信号的解调通常采用（）相干解调。

5、数字通信的任务是（）、（）地传递信息。

二、选择题（24分）

从下面所列答案中选择出最合理的答案，填入后面的答题中。每个空格只能选一个答案，不排除某一个答案被多次选择的可能性。

示例题：3+2=（s），2×0=（q）

(a)6(b)降低(c)快速(d)调制信号

(e)模拟(f)准确(g)时域均衡(h)慢

(i)7(j)不变(k)数字(l)窄带

(m)码间干扰(n)循环平稳(o)提高(p)2

(q)0(r)9(s)5(t)3

(u)4(v)小(w)大(x)1

1、某二进制信源中连续出现的0的个数最多是6个，此信源经过AMI、HDB3、数字分相码编码后，编码结果中连续出现的0的个数最多分别是（）、（）和（）个。

2、设到达接收端的已调信号功率和信道噪声的功率谱密度已经给定。降低调制指数后，FM解调器的输入信噪比（）、输出信噪比（）；对于AM，包络检波器输入的信噪比（），输出信噪比（）。

入学考试试题(A卷)(答案必须写在答题纸上)

考试科目:数字通信科目代码：3807

适用专业:通信与信息系统、信号与信息处理、移动计算与人机

交互、微纳信息系统

3、出现概率越（）的消息，其所含的信息量越大；出现概率越（）的消息，其所含的信息量越小。

4、二进制PAM信号的眼图中，居中的水平线一般对应最佳判决门限。如果已知发送+A的机会比发送-A的机会多，那么最佳判决门限应该（）。

5、对于传输信道所引入的码间干扰，一种基本的解决方法是采用（）。

6、某个线性双端口网络的功率增益是3dB，噪声系数是3dB。若其输入端的噪声源是常温电阻，那么它的输出噪声功率将是输入噪声功率的（）倍。

三、设某信源的输出由160个不同的符号组成，其中32个出现的概率为1/64，其余128个的出现概率为1/256。信源每秒发出3000个符号，且每个符号彼此独立。请计算该信源的平均信息速率。（10分）

四、Translate the following from English into Chinese（英译汉）.And，say something about your understanding of digital communications,communication system,or information system.（对系统或模块的理解与看法）.(50分)

The rationale and structure of this volume is centred around the following‘story-line’.The conception of parallel transmission of data over dispersive channels dates back to the seminal paper of Doelz et al. published in1957,leading to the OFDM philosophy,which has found its way into virtually all recent wireless systems,such as the Wi-Fi,WiMAX,LTE and DVB as well as DAB broadcast standards. Although MIMO techniques are significantly‘younger’than OFDM,they also reached a state of maturity and hence the family of recent wireless standards includes the optional employment of MIMO techniques,which motivates the joint study of OFDM and MIMO techniques in this volume.

The research of MIMO arrangements was motivated by the observation that the MIMO capacity increases linearly with the number of transmit antennas,provided that the number of receive antennas is equal to the number of transmit antennas.With the further proviso that the total transmit power is increased proportionately to the number of transmit antennas,a linear capacity increase is achieved upon increasing the transmit power.This is beneficial since,according to the classic Shannon–Hartley law,the achievable channel capacity increases only logarithmically with the transmit power.Thus MIMO-OFDM may be considered a‘green’transceiver solution.

This volume therefore sets out to explore the recent research advances in MIMO-OFDM techniques as well as their limitations.The basic types of multiple-antenna-aided OFDM systems are classified and their benefits are characterized.Space-Division Multiple Access(SDMA),Space-Division Multiplexing(SDM)and space–time coding MIMOs are addressed.We also argue that under realistic propagation conditions,when for example the signals associated with the MIMO elements become correlated owing to shadow fading,the predicted performance gains may substantially erode.