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Diffstat (limited to 'chapter07/content_ch07.tex')
| -rw-r--r-- | chapter07/content_ch07.tex | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/chapter07/content_ch07.tex b/chapter07/content_ch07.tex index f332b10..56871e7 100644 --- a/chapter07/content_ch07.tex +++ b/chapter07/content_ch07.tex @@ -1887,15 +1887,21 @@ However, not each $L_1$ code is orthogonal to any $L_2$ code. The relation of or \label{fig:ch07:ovsf_code_tree} \end{figure} -The rules for creating the \acs{OVSF} code tree are (derived from the construction rules of the Hadamard matrix):
-\begin{itemize}
- \item The parent node in the tree is $\vect{C}_{n,k}$ ($n$ is the code length, $k$ is the index).
- \item The child nodes are:
- \begin{itemize}
- \item $\vect{C}_{2n,2k-1} = \left[\vect{C}_{n,k}, \vect{C}_{n,k}\right]$
- \item $\vect{C}_{2n,2k} = \left[\vect{C}_{n,k}, -\vect{C}_{n,k}\right]$
- \end{itemize}
-\end{itemize}
+The rules for creating the \acs{OVSF} code tree are (derived from the construction rules of the Hadamard matrix): +\begin{itemize} + \item The parent node in the tree is $\vect{C}_{n,k}$ ($n$ is the code length, $k$ is the index). + \item The child nodes are: + \begin{itemize} + \item $\vect{C}_{2n,2k-1} = \left[\vect{C}_{n,k}, \vect{C}_{n,k}\right]$ + \item $\vect{C}_{2n,2k} = \left[\vect{C}_{n,k}, -\vect{C}_{n,k}\right]$ + \end{itemize} +\end{itemize} + +The different code lengths have benefits and drawbacks. +\begin{itemize} + \item Longer codes have lower data rates. But they have a higher processing gain and better noise immunity. Data decoding works in noisy environments with low \ac{SNR}. + \item Short codes give a higher data rate. However, the processing gain is less as well as the noise immunity. Data decoding may not work in noisy environments. A proper \ac{SNR} is required. +\end{itemize} \subsection{Asynchronous \acs{DS-CDMA}} |