he output bit sequence of the bit-interleaving function is the input to code block concatenation. The code block concatenation consists of sequentially concatenating the rate-matched outputs of different code blocks. The output bit sequence of code block concatenation is denoted by go,g1, gG-1 where G is the total number of coded bits for transmission [7]. Rate matching is performed separately for each code block by puncturing a fraction of sys- tematic bits. Depending on the code block size, the fraction of punctured systematic bits can be up to one-third of the systematic bits. The remaining coded bits are written into a circular buffer, starting with the non-punctured systematic bits and continuing with parity bits as shown in Fig. 4.36. The selection of the bits for transmission is based on reading the Transport block (TB) Code block segmentation Code block (CB) Code block (CB) Code block (CB) CRC addition Code block (CB) Code block (CB) Code block (CB) Zero padding Code block (CB) LDPC encoding Code block (CB) Parity bits Punctured Rate matching Systematic Systematic Parity bits Parity bits Transmitted bits Puncturing Repetition Systematic Systematic Systematic Systematic Parity bits Parity bits Parity bits Parity bits 1st Transmission 2nd Transmission 3rd Transmission 4th Transmission Figure 4.36 Example of rate-matching and code block concatenation processes 14]. New Radio Access Physical Layer Aspects (Part 2) 491 Circular Bit-level Code block encoded buffer interleaver concatenation LDPC encoded bits Bits for the 1st Bits for the 2nd Bits for the 3rd Bits for the 4th 1st 2Z group group group group 256QAM 256QAM 256QAM 256QAM symbol 0 symbol 0 symbol 0 symbol 0 Figure 4.37 Example bit-level interleaving for 256QAM modulation. Table 4.9: Starting position of different redundancy versions [7]. LDPC Base Graph 1 LDPC Base Graph 2 17Ncb 13N cb 25Nc6 43Nch required number of bits from the circular buffer where the exact set of bits to transmit depends on the RV corresponding to different starting positions in 