Communications Questions

Hey can anyone please help me as I have been given the following
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 :)


(please note ^ means 'to the power of')


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

cwynnes@hotmail.com wrote:

> Hey can anyone please help me as I have been given the following
> 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 :)
> 
> 
> (please note ^ means 'to the power of')
> 
> 
> 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
> 
I have a choice between giving you answers that will be correct but 
meaningless to you without context, or directing you to books that will 
give you context.  Try these (and if they absolutely hit the spot, think 
about what is wrong with your literature search).

Questions 1 through 3 are error-correcting code problems, and should 
come out of such a book.  "The Theory of Error-Correcting Codes" by 
MacWilliams & Sloane and "Error Correcting Coding for Digital 
Communications" by Clark & Cain are the books on my shelf.  It's been so 
long that I can't remember which one of these books was the more useful, 
but they'll both answer all three questions.

Questions 4 and 5 are simple modulation questions.  The ARRL Handbook 
will answer 4, "Information Transmission, Modulation and Noise" by 
Schwartz should answer both.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Hey Tim,
Thanks for your help in responding, as iam in college now and i have
researched the library catalogue but unfortunately the books you
recommended are not there, have you any further ideas on what i could
do as the deadline this nears and i find myself still as far away
Thanks again

Hello,

Wouldn't the answers be in your text or class notes or assigned reading? I 
bet they are there.

Clay


<cwynnes@hotmail.com> wrote in message 
news:1105372258.567700.283990@c13g2000cwb.googlegroups.com...
> Hey Tim,
> Thanks for your help in responding, as iam in college now and i have
> researched the library catalogue but unfortunately the books you
> recommended are not there, have you any further ideas on what i could
> do as the deadline this nears and i find myself still as far away
> Thanks again
> 

Hey,
My course notes are here in the link below, iam unable to find the
relevant material and i dont know where to start, the password for them
is CSN287

http://www.electronics.dit.ie/staff/bfaust/notes_DT287.htm

A quick look, and I found the answers to your last 2 questions in these 
notes. For analog modulation, try looking at the analog nots.




<cwynnes@hotmail.com> wrote in message 
news:1105373347.371617.46770@c13g2000cwb.googlegroups.com...
> Hey,
> My course notes are here in the link below, iam unable to find the
> relevant material and i dont know where to start, the password for them
> is CSN287
>
> http://www.electronics.dit.ie/staff/bfaust/notes_DT287.htm
> 

<cwynnes@hotmail.com> wrote in message 
news:1105366353.748870.167460@c13g2000cwb.googlegroups.com...
> Hey can anyone please help me as I have been given the following
<snip>
 Questions 1 and 2 look like they might have something to do with shift 
registers - try :

http://homepage.mac.com/afj/lfsr.html
http://iroi.seu.edu.cn/books/asics/Book/CH14/CH14.7.htm

best of luck  - Mike

I was looking at question 5 and iam struggling to find the modulating
frequency which is needed for the modulation index,
Any help would be great

Does anyone know how i could do the bessel function question????

<cwynnes@hotmail.com> wrote in message 
news:1105377187.000191.317340@c13g2000cwb.googlegroups.com...
>I was looking at question 5 and iam struggling to find the modulating
> frequency which is needed for the modulation index,
> Any help would be great
>
3142/2/pi  Hz assuming that t is in seconds and that you have a second 
bracket ")" closing out your equation.

Best of Luck - Mike