Fig. 2

Polar code with \(N=8\) can be considered as two concatenated codes: a Two length-4 outer codes \({\mathcal {C}}_1\) and \({\mathcal {C}}_2\) with the inner code \({\mathcal {C}}_0\). b Four length-2 outer codes \({\mathcal {C}}^{'}_1\), \({\mathcal {C}}^{'}_2\), \({\mathcal {C}}^{'}_3\), and \({\mathcal {C}}^{'}_4\) with the inner code \({\mathcal {C}}^{'}_0\)