Question

3. (a) Explain briefly the 3 main multiplexing techniques used in mobile communication systems, Frequency Division Multiplexing (FDMA), Time Division Multiplexing (TDMA) and Code Division Multiplexing (CDMA). [4] (b) A number of Mobile Communication Systems use Orthogonal Frequency Division Multiplexing (OFDM) to provide higher communication rates, explain why ODFM is less affected by fading and so supports higher data [6] rates. (c) Using the code generator matrix G (6,3), redraw and complete the table by calculating the codewords (c) and the Hamming weight for each sequence of data (d). $\begin{bmatrix} 1 & 0 & 0 & 1 & 1 & 0\\ 0 & 1 & 0 & 1 & 0 & 1\\ 0 & 0 & 1 & 0 & 1 & 1 \end{bmatrix}$ G = \begin{tabular}{|c|c|c|} \hline d & c & Hamming\\& & weight\\\hline 000 & & \\ 001 & & \\ 010 & & \\ 011 & & \\ 100 & & \\ 101 & & \\ 110 & & \\ 111 & & \\ \hline \end{tabular} 3 [5] (d) Using an example of two codewords from the table, describe what is meant by Hamming distance. [2] (e) Using the result from part 3(c), what is the minimum Hamming distance? [2] (f) Calculate the Hamming matrix for the code (6,3) in 3(c) and use it to determine whether the following received data streams are correct or contain an error: i) 111001 [3] ii) 010101 [3]

          3.
(a) Explain briefly the 3 main multiplexing techniques used in mobile
communication systems, Frequency Division Multiplexing (FDMA), Time
Division Multiplexing (TDMA) and Code Division Multiplexing (CDMA).
[4]
(b)
A number of Mobile Communication Systems use Orthogonal Frequency
Division Multiplexing (OFDM) to provide higher communication rates,
explain why ODFM is less affected by fading and so supports higher data
[6]
rates.
(c) Using the code generator matrix G (6,3), redraw and complete the table
by calculating the codewords (c) and the Hamming weight for each
sequence of data (d).
$\begin{bmatrix} 1 & 0 & 0 & 1 & 1 & 0\\ 0 & 1 & 0 & 1 & 0 & 1\\ 0 & 0 & 1 & 0 & 1 & 1 \end{bmatrix}$ 
G = 
\begin{tabular}{|c|c|c|}
\hline
d & c & Hamming\\& & weight\\\hline
000 &  & \\
001 &  & \\
010 &  & \\
011 &  & \\
100 &  & \\
101 &  & \\
110 &  & \\
111 &  & \\
\hline
\end{tabular}
3
[5]
(d) Using an example of two codewords from the table, describe what is
meant by Hamming distance.
[2]
(e) Using the result from part 3(c), what is the minimum Hamming distance?
[2]
(f) Calculate the Hamming matrix for the code (6,3) in 3(c) and use it to
determine whether the following received data streams are correct or
contain an error:
i) 111001
[3]
ii) 010101
[3]

3.
(a) Explain briefly the 3 main multiplexing techniques used in mobile
communication systems, Frequency Division Multiplexing (FDMA), Time
Division Multiplexing (TDMA) and Code Division Multiplexing (CDMA).
[4]
(b)
A number of Mobile Communication Systems use Orthogonal Frequency
Division Multiplexing (OFDM) to provide higher communication rates,
explain why ODFM is less affected by fading and so supports higher data
[6]
rates.
(c) Using the code generator matrix G (6,3), redraw and complete the table
by calculating the codewords (c) and the Hamming weight for each
sequence of data (d).
< b m a t r i x >
G =

d c Hamming
weight
000

001

010

011

100

101

110

111

3
[5]
(d) Using an example of two codewords from the table, describe what is
meant by Hamming distance.
[2]
(e) Using the result from part 3(c), what is the minimum Hamming distance?
[2]
(f) Calculate the Hamming matrix for the code (6,3) in 3(c) and use it to
determine whether the following received data streams are correct or
contain an error:
i) 111001
[3]
ii) 010101
[3]

Added by Jenna R.

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