# Communications systems and networks

Discussion in 'Cisco' started by cwynnes@hotmail.com, Jan 7, 2005.

1. ### Guest

questions to do an iv researched some books but still haven't got a
clue, The subject is communications systems and networks, any help
would be greatly appreciated

Question 1

Assume the following wing polynomial is the generator polynomial for a
cyclic code and design a syndrome testing circuit using feedback shift
registers.

G(X) = 1 + X + X^4 + X^6

Question 2

The generator polynomial of a (15,11) Hamming code is defined as:

G(X) = 1 + X + X^4

(i) Design a feedback register encoder implementing this coding scheme.
(ii) Illustrate the encoding procedure with the message 11001101011, by
listing the successive states of the registers

Question 3

Consider a systematic block code that forms its codewords by adding to
the bits mi of the messages, the parity bits pi defined by the
following equations (called parity check equations):

P1 = m1 + m2 + m4
P2 = m1 + m3 + m4
P3 = m1 + m2 + m3
P4 = m2 + m3 + m4

a) Find the generator matrix and the parity check matrix for the code.
b) How many errors can the code correct?
c) Is 10101010 a valid codeword?
d) Is 01011100 a valid codeword?

Question 4

The maximum and minimum values taken by the envelope of an AM signal
are 3.5 and 0.5 volts. What is the modulation index?
The ratio transmitter radiates 10kW. How much is the carrier power?

Question 5

An angle-modulated wave is described as:

V(t) = 10cos(2pi10^8t + sin(3142t)

Determine:

(i) The modulation index
(ii) The frequency deviation
(iii) The frequency components of the spectrum using Bessel function
tables

, Jan 7, 2005

2. ### Walter RobersonGuest

In article <>,
<> wrote:
:questions to do an iv researched some books but still haven't got a
:clue, The subject is communications systems and networks, any help
:would be greatly appreciated

None of those questions are Cisco specific. None of them
are even TCP or UDP or ethernet specific. comp.dcom.sys.cisco is thus
not an appropriate newsgroup. Those look like Electrical Engineering
or Digital Logic or Computer Science questions. I would suggest
that you would be better searching for a forum that deals with
the topics.

:Question 1

:Assume the following wing polynomial is the generator polynomial for a
:cyclic code and design a syndrome testing circuit using feedback shift
:registers.

:G(X) = 1 + X + X^4 + X^6

Yes? And -your- question is what, exactly? What part of that are
you stuck on? The definition of 'wing polynomial'? Of 'generator
polynomial'? Of 'cyclic code'? Of 'syndrome testing circuit' ?
Do you know what 'feedback shift registers' are?

In that context, what do the operators '+' and '^' mean? 'bitwise or',
'addition', 'raised to the power of', 'bitwise exclusive or' ? How many
bits of precision for intermediate results? How many bits of precision
for the final answer? Could the result be different if you were to
perform the operations in a different order instead of left-to-right ?
What is the range of X that the generator is valid over?

We don't do homework for people here. We might, though, if we
weren't busy, answer something if you clarify what it is you already
know and if you then discuss the parts you do not understand, presenting
the alternative interpretations that you have thought of and asking
which one is correct.

--
I've been working on a kernel
All the livelong night.
I've been working on a kernel
And it still won't work quite right. -- J. Benson & J. Doll

Walter Roberson, Jan 7, 2005

3. ### Hansang BaeGuest

On 7 Jan 2005 13:31:42 -0800, wrote:

>questions to do an iv researched some books but still haven't got a
>clue, The subject is communications systems and networks, any help
>would be greatly appreciated
>
>Question 1
>
>Assume the following wing polynomial is the generator polynomial for a
>cyclic code and design a syndrome testing circuit using feedback shift
>registers.
>
>G(X) = 1 + X + X^4 + X^6
>

[snip]

>Question 4
>
>The maximum and minimum values taken by the envelope of an AM signal
>are 3.5 and 0.5 volts. What is the modulation index?
>The ratio transmitter radiates 10kW. How much is the carrier power?
>
>Question 5
>
>An angle-modulated wave is described as:
>
>V(t) = 10cos(2pi10^8t + sin(3142t)
>
>Determine:
>
>(i) The modulation index
>(ii) The frequency deviation
>(iii) The frequency components of the spectrum using Bessel function
>tables

Question 6
If I flunk this exam/homework, what will my GPA be?

Just suck it up an take the "F" for the take home exam/homework.
Chock it up to lessons learned and don't wait to the last minute next
time.

the *LEAST you could've done was to a) post it in the right newsgroup
b) tell us what you understand or don't understand. c) why you think

At least you had enough sense to not post from your .edu account.

hsb

"Somehow I imagined this experience would be more rewarding" Calvin
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