Example Soft Value Mapping for LDPC Decode Input - 1.1 English

The following table provides an example for the case of LDPC decoder of how a 5-bit integer range of input is mapped to the soft value (that is, no fractional bits). Note that inputs that are out of range have been saturated (symmetrically).

Note that values in the previous table assume a direct mapping without scaling. Better performance might be achieved by scaling the input by a value less than 1 to reduce or completely avoid saturation. System simulations should be performed to determine the best use of input range for a particular code, channel and symbol mapping. Also, adjustment of the normalization factor might improve performance (where 0.75 is a good starting point).

When LLR input is for turbo decode, then LLRs for Systematic, Parity and Parity Interleaved are provided interleaved for the K inputs, followed by 12 tail bits as shown in the following table.