同济大学通信系统原理(英文班)练习题附答案

Chapter 1

Homework:

Fill-in Questions:

log M) bits 1. In a M-ary communication system, each symbol contains ( 2

information content.

2. The purpose of communication is to ( transfer information ). Efficiency of the digital communication system can be measured by the specifications such as (R B) , (R b) , ( η). And reliability can be measured by ( P e) , (P b).

3. The basic factors for measuring the merit of a communication system are (efficiency ), and ( reliability ).

4. The main influence of constant parameter channel on signal transmission are usually described by their ( Amplitude-Frequency ) and ( Phase-Frequency ) characteristics.

5. Common characteristics of random parameter channels are (transmission attenuation of the signal is varying with time ), (transmission delay of the signal varies with time ), and (signal arrives at the receiver over several paths ).

Multiple-Choice Questions:

1.For analog and digital communications, which is (are) true? ( A B C D ).

A. digital communication typically uses more bandwidth.

B. analog communication cares more about fidelity

C. digital communication cares more about probability for correct decision

D. digital communication typically uses analog carrier to carry baseband signals

Single-Choice Questions:

1. The symbol rate of 16-ary digital signal is 1200Bd, then the corresponding information rate is ( D ); If with the same information rate, the symbol rate of 8-ary digital signal is ( D ).

A. 1600b/s, 1200Bd

B. 1600b/s, 3200Bd

C. 4800b/s, 2400B

D. 4800b/s, 1600B

2. Assume the delay difference of two paths in a random parameter channel is τ, the frequencies of maximum transmission loss are ( B ), the frequencies =

1

ms

of minimum transmission loss are ( B ).

A. n kHz, (n+0.5)kHz

B. (n+0.5)kHz, n kHz

C. n kHz, (n+0.2)kHz C. (n+0.2)kHz, n kHz

True or False

When there is no input signal, the additive interference doesn’t exist, but the multiplicative interference still exists. ( F )

Homework: 2.1, 2.4, 2.5, 2.6, 2.8, 2.11

Fill-in Questions:

1. AWGN noise is short term for ( Additive White Gaussian Noise ).

2. The power spectral density and ( the autocorrelation function ) of a stationary random

process are a pair of Fourier transform.

3. If bandwidth is 10 MHz, signal-to-noise ratio is 20dB, the Shannon capacity is C=( 66.6

Mbps ).

Single-Choice Questions:

1. Assume X(t) is a generalized stationary random process with zero mathematical expectation, then the average power of X(t) is ( D ).

A. E[X (t )]

B. E 2[X (t )]

C. R(∞)

D. D[X (t )]

2. For a narrow band random process 00()()cos ()sin C S X t X t t X t t ωω=-, if ()X t is a Gaussian process, then ( A ).

(A) ()C X t and ()S X t are also Gaussian processes; (B) Only ()C X t is also Gaussian process;

(C) ()C X t and ()S X t are not Gaussian processes; (D) Only ()S X t is also Gaussian processes.