Is this figure a correct (O)QPSK waveform?
i think, for OQPSK with the convention that the even-indexed data samples go into \$i(t)\$ and the odd-indexed data samples go into \$q(t)\$ , the IQ waveforms, in terms of the data is :

$$\begin{align}
i(t) &amp;= \sum\limits_{m=-\infty}^{\infty} x[2m] \, p(t-2m T_c) \\
\\
q(t) &amp;= \sum\limits_{m=-\infty}^{\infty} x[2m+1] \, p(t-(2m+1) T_c) \\
\end{align}$$

in the waveforms shown in the OP, the definition of the pulse shape \$p(t)\$ is:

$$ p(t) = \begin{cases} 
 0 \qquad &amp; t &lt; 0 \\
 \sin\left(\tfrac{\pi}{2 T_c} t \right) \qquad &amp; 0 \le t &lt; 2T_c \\
 0 \qquad &amp; 2T_c \le t \\
\end{cases} $$

and the bipolar binary data is:

$$ x[n] = 2 a[n] - 1 $$

and \$a[n] \in \{0,1\}\$ are the raw bit data.

The nice thing about Offset-QPSK is that it naturally separates the even and odd samples because the \$i(t)\$ depends only on the even samples and switches at times of even multiples of \$T_c\$.  \$q(t)\$ depends only on the odd samples and switches at times of odd multiples of \$T_c\$.

A smarter pulse shape to simply constrain the IQ signal to a bandwidth of \$\frac{1}{T_c}\$ is:

$$ p(t) = \operatorname{sinc}\left(\tfrac{t - T_c}{2 T_c} \right) w\left(\tfrac{t-T_c}{N T_c}\right) $$

and 

$$ \operatorname{sinc}(u) \triangleq \begin{cases} 
 1 \qquad &amp; u = 0 \\
 \frac{\sin(\pi u)}{\pi u} \qquad &amp; 0 &lt; |u| \\
\end{cases} $$.

I didn't bother to define the window function here, but suggest a Kaiser of width \$2N\$ samples.