RC bits can be used (see Figure 3.5.20). The key idea of Polar codes relies on the "polarization" of binary input channels into "low". and "high"-quality channels after linear transformation, where the number of "high"-quality channels will be determined by the channel capacity. In practice, such "polarization" of the channels is exploited by transmitting information bits using "high"-quality channels, while predetermined "frozen" bits (e.g. fixed to 0) are transmitted for the "low"-quality channels. The knowledge of the "frozen" bits is used at the receiver to correct the errors in the received signal. The linear transformation for Polar codes is determined by a special square matrix (often denoted as Kernel), which typically has a dimension of 2N, N : 5, 6, 10. In NR the sequence of indices determining the set of "frozen" bits is common for all supported lengths of 2N The structure of Polar codes used in NR is shown in Figure 3.5.21. First, depending on the length of the information sequence the input information sequence can be segmented into multiple blocks. Code block segmentation is followed by CRC attachment, with CRC in Polar coding being used to detect false decoding (as in conventional procedures) as well as to improve the error rate performance through CRC-aided list decoding algorithms. Unlike CRC polar code Zero padding DCI, MIB 24 bits CRC Polar code CRC polar code Block codes PC, 6 bits CRC 11 bits CRC Payload, bits Figure 3.5.20 Polar coding control information in NR. 3.5 NR Physical Layer Sub-block Codeblock Channel Parity check Polar coding interleaving, segmentation interleaving Rate matching Figure 3.5.21 Polar coding chain supported in NR. LTE where the CRC bits are always contiguous and transmitted as the last bits of the block, in Polar codes the CRC bits can be distributed across the input sequence of DCI bits to facilitate early detection of false decoding. Depending on the length of the information sequence, parity check outer coding can be used to obtain some of the "frozen" bits based 