A method of operation of a wireless transmitter in a wireless communication network, the method comprising: encoding a set of information carrying data bits u of length K with a linear outer code to generate a set of outer parity bits p along with the data bits u, wherein the linear outer code is a cyclic redundancy code, CRC, and the outer parity bits are CRC bits; interleaving the set of outer parity bits p and the data bits u using a predetermined interleaving mapping function that depends on the number of data bits K and is operable to distribute some bits of the set of parity bits p in front of some data bits u; and encoding the interleaved bits using a polar encoder to generate a set of encoded bits x, and wherein the predetermined interleaving mapping function comprises a template interleaver for a largest value of K, referred to as K max , and the template interleaver comprises a high-index bit mapper wherein: the K data bits are loaded at the high-index positions of the input of the template interleaver, where u = [ u 0 , u 1 , ···, u K -1 ] and the input of the template interleaver, denoted by v = [ v 0 , v 1 , ···, v K max - 1 ], is given by the following bit mapping: v i = { u i − K max + K K max − K ≤ i < K max p i − K max i ≥ K max NULL otherwise and wherein K max is 140 and the template interleaver uses the following interleaving pattern, wherein indices corresponding to CRC bits are underlined: φ T =[0 2 4 7 9 14 19 20 24 25 26 28 31 34 42 45 49 50 51 53 54 56 58 59 61 62 65 66 67 69 70 71 72 76 77 81 82 83 87 88 89 91 93 95 98 101 104 106 108 110 111 113 115 118 119 120 122 123 126 127 129 132 134 138 139 140 1 3 5 8 10 15 21 27 29 32 35 43 46 52 55 57 60 63 68 73 78 84 90 92 94 96 99 102 105 107 109 112 114 116 121 124 128 130 133 135 141 6 11 16 22 30 33 36 44 47 64 74 79 85 97 100 103 117 125 131 136 142 12 17 23 37 48 75 80 86 137 143 13 18 38 144 39 145 40 146 41 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 ]. encoding a set of information carrying data bits u of length K with a linear outer code to generate a set of outer parity bits p along with the data bits u, wherein the linear outer code is a cyclic redundancy code, CRC, and the outer parity bits are CRC bits; interleaving the set of outer parity bits p and the data bits u using a predetermined interleaving mapping function that depends on the number of data bits K and is operable to distribute some bits of the set of parity bits p in front of some data bits u; and encoding the interleaved bits using a polar encoder to generate a set of encoded bits x, and wherein the predetermined interleaving mapping function comprises a template interleaver for a largest value of K, referred to as K max , and the template interleaver comprises a high-index bit mapper wherein: the K data bits are loaded at the high-index positions of the input of the template interleaver, where u = [ u 0 , u 1 , ···, u K -1 ] and the input of the template interleaver, denoted by v = [ v 0 , v 1 , ···, v K max - 1 ], is given by the following bit mapping: v i = { u i − K max + K K max − K ≤ i < K max p i − K max i ≥ K max NULL otherwise and wherein K max is 140 and the template interleaver uses the following interleaving pattern, wherein indices corresponding to CRC bits are underlined: φ T =[0 2 4 7 9 14 19 20 24 25 26 28 31 34 42 45 49 50 51 53 54 56 58 59 61 62 65 66 67 69 70 71 72 76 77 81 82 83 87 88 89 91 93 95 98 101 104 106 108 110 111 113 115 118 119 120 122 123 126 127 129 132 134 138 139 140 1 3 5 8 10 15 21 27 29 32 35 43 46 52 55 57 60 63 68 73 78 84 90 92 94 96 99 102 105 107 109 112 114 116 121 124 128 130 133 135 141 6 11 16 22 30 33 36 44 47 64 74 79 85 97 100 103 117 125 131 136 142 12 17 23 37 48 75 80 86 137 143 13 18 38 144 39 145 40 146 41 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 ]. <EOS>