vides the shift coefficient design to be used in the encoding. Since the number of bits in a code block may not perfectly match the dimension of the encoding matrix, some amount of padding is done before TB-CRC Transport block CB-CRC Code block #1 Code block #2 Code block #3 Figure 6.49 CRC attachment (TB-level and CB-Level) and code block segmentation. 6.13 Channel Coding with 5G the encoding procedure. However, these padding bits are removed after the encoding. In channel encoding, the LDPC design explained in the earlier section is used for each code block. After the encoding, the coded, bits of each code block are copied to a circular buffer and rate matching is performed. The rate matching in 5G has two different components: the first is bit selection from the rate matcher, and the second is the bit interleaver of the selected bits. The length of the circular buffer is defined on the basis of the encoded block size or the limited buffer rate matching (LBRM). The former is applied for large TBSs, where a limit in the TBS is used as the LBRM TBS, which is determined from the code rate (2/3), resource allocation (depending on the active BWP), and other assumptions which are required in the transport block determination procedure in 5G. As LBRM is not the main topic of discussion in this section, we do not go into the details here. The selection of the bits is made sequentially from predefined positions in the circular buffer, and these predefined starting positions usually provide different redundancy versions. Redundancy versions are defined as RV0, RV1, RV2, and RV3. In 5G, RVs are not uni- formly separated as in LTE. For base graph #1, the starting positions of RVs are 0, 17/66, 33/66, and 56/66 in fractions of the circular buffer. For base graph #2, they are 0, 13/50, 25/50, and 43/50 in portions. An illustration of different RVs and retransmission options is given in Figure 6.50. After the bit selection, each coded block goes through a bit interleaver to increase the robustness of the performance in wirele