REVIEW EXERCISES
145
Table 6.7
Controlled Slip Performance on a 64-kbps
International Connection Bearer Channel
Performance
Category
Mean Slip Rate
Proportion
of Time
a
(a)
b
5 slips in 24 h
>98.9%
(b)
>5 slips in 24 h and
<1.0%
30 slips in 1 h
(c)
>30 slips in 1 h
<0.1%
a
Total time
1 year.
b
The nominal slip performance due to plesiochronous operation alone
is not expected to exceed 1 slip in 5.8 days.
Source: CCITT Rec. G.822 (Ref. 14).
REVIEW EXERCISES
1.
What is the major overriding advantage of binary digital transmission? Give at least
two secondary advantages.
2.
Name the three steps to develop a PCM signal from an analog signal.
3.
Based on the Nyquist sampling theorem, what is the sampling rate for a nominal
4-kHz voice channel? for a 56-kHz radar product signal?
4.
If I'm transmitting 8000 frames per second, what is the duration of one frame?
5.
Give a simple definition of quantization distortion.
6.
Our system uses linear quantization. How can we reduce quantization distortion
(noise)?
7.
What is the negative downside to increasing quantization steps?
8.
Companding used in PCM systems follows one of two laws. Identify each law--its
name and where is it applied.
9.
How many bits are there in a PCM word? How many different binary possibilities
can be derived from a PCM word or codeword?
10.
If a PCM code received starts with a 0, what do we know about the derived volt-
age sample?
11.
Bits 2, 3, and 4 of the PCM codeword identify the segment. How many total seg-
ments are there?
12.
In DS1, of what use is the framing bit?
13.
How is the identification of frame beginning carried out in E1?
14.
How is signaling carried out in DS1? in E1?
15.
How do we arrive at 1.544 Mbps for DS1?
16.
With the AMI line code, how is the zero coded?
17.
If, with bipolar transmission, under "normal" circumstances, the first 1 is a
-1.0 V,
what would the second "1" be?
18.
Where does a wire-pair cable or light-wave regenerative repeater derive its tim-
ing from?