tikz: how to draw this flowchart

Question

I would like to draw a flowchart similar to the one in the picture, but have absolutely no idea as to how go about it. I have only used tikz-qtree for drawing trees thus far, so I would be immensely grateful for any help.

Answer 1

As starting point can serve this illustration (from one of my textbooks):

\documentclass[border=3mm]{standalone}
\usepackage[edges]{forest}

\begin{document}
    \begin{forest}
    for tree={              
% style of nodes in the tree
      draw, rounded corners, semithick,
             font = \scshape\linespread{.84}\selectfont,
        top color = teal!10,
     bottom color = teal!50,
   minimum height = 11mm,
       text width = 24mm, text badly centered,
        inner sep = 2mm,
% style of tree (edges, distances, direction)
             edge = {draw, semithick, -stealth},
           anchor = north,
             grow = south,
    forked edge,            % for forked edge
            s sep = 8mm,    % sibling distance
            l sep = 8mm,    % level distance
         fork sep = 3.5mm,  % distance from parent to branching point
               }
[kanalsko kodiranje
    [ponovno pošiljanje
        [tekoče kodiranje]
        [kodi s pomnjenjem]
    ]
    [vnaprejšnje popravljanje napak]
]
    \end{forest}
\end{document}

Since your flowchart is actually tree diagram, in above MWE for drawing code is used forest package. Above MWE produce:

Real text in nodes I left to you. Inserting them should be straight forward.