4.2.5 1st interleaving

25.2223GPPMultiplexing and channel coding (TDD)Release 17TS

The 1^st interleaving is a block interleaver with inter-column permutations. The input bit sequence to the block interleaver is denoted by , where i is TrCH number and X_i the number of bits. Here X_i is guaranteed to be an integer multiple of the number of radio frames in the TTI. The output bit sequence from the block interleaver is derived as follows:

1) select the number of columns C1 from table 4 depending on the TTI. The columns are numbered 0, 1, …, C1 – 1 from left to right.

2) determine the number of rows of the matrix, R1 defined as

R1 = X_i / C1.

The rows of the matrix are numbered 0, 1, …, R1 – 1 from top to bottom.

3) write the input bit sequence into the R1 C1 matrix row by row starting with bit in column 0 of row 0 and ending with bit in column C1 – 1 of row R1 – 1:

4) Perform the inter-column permutation for the matrix based on the pattern shown in table 4, where P1_C1(j) is the original column position of the j-th permuted column. After permutation of the columns, the bits are denoted by y_i,k:

5) Read the output bit sequence of the block interleaver column by column from the inter-column permuted R1 C1 matrix. Bit corresponds to row 0 of column 0 and bit corresponds to row R1 – 1 of column C1 – 1.

Table 4 Inter-column permutation patterns for 1st interleaving

TTI	Number of columns C1	Inter-column permutation patterns <P1C1(0), P1C1(1), …, P1C1(C1-1)>
5ms(*1), 10 ms	1	<0>
20 ms	2	<0,1>
40 ms	4	<0,2,1,3>
80 ms	8	<0,4,2,6,1,5,3,7>

^(*1) can be used for PRACH for 1.28 Mcps TDD

4.2.5.1 Relation between input and output of 1^st interleaving

The bits input to the 1^st interleaving are denoted by , where i is the TrCH number and T_i the number of bits. Hence, x_i,k = t_i,k and X_i = T_i.

The bits output from the 1^st interleaving are denoted by , and d_i,k = y_i,k.