About using Walsh matrix as spreading sequence I'm asking about some details about using the Walsh matrix as spreading sequence code. For example, suppose I'm using a $4\times 4$ Walsh matrix given by

$$H = \begin{pmatrix}
1 &amp; 1 &amp; 1 &amp; 1 \\
1 &amp; -1 &amp; 1 &amp; -1 \\
1 &amp; 1 &amp; -1 &amp; -1 \\
1 &amp; -1 &amp; -1 &amp; 1
\end{pmatrix}$$
and I have data $x$ which will be spread on that Walsh matrix.

My question: what is the length of $x$ supposed to be? Must it be less than 4? Or can it be more than 4 too? In other words, suppose I have a signal $x = 10$ , it's supposed that is easy to spread the signal $x$ on the first column of $H$. The question is,  What's about if the signal $x = 101101$ , can we do the spread on the first column too? where the signal $x$ has length larger than the first column.
Yes you can, because you do spreading for each bit of data. So, regardless the length of your data, you are going to spread every bit on your code. In case if you have $x = 10$ you will have data after spreading with length 8, and if $x=101101$ you will have data  to send with length 4 x 6 = 24. Just try to understand the process of spreading (I think it's by XOR), then you do spread for each bit of data, not for all data. 

Good luck