Patent ID: 9432059
Filing Date: 2016-08-30
CPC Classification: H03M,H04B,H04L

Claim Text:
1. A turbo equalizer comprising: a first noise variance estimator that calculates a first noise variance estimation value based on a channel estimation value of a received signal; a minimum mean squared error (MMSE) filter that performs equalization processing on a residual interference component that is obtained by subtracting an interference component and a desired signal component from the received signal; a second noise variance estimator that calculates a second noise variance estimation value by using the equalized residual interference component that is output from the MMSE filter; a first noise variance selector that selects either one of the first noise variance estimation value or the second noise variance estimation value, or selects a mean value of the first noise variance estimation value and the second noise variance estimation value, based on a first judgment criterion that is different between a first round and a second or subsequent round of repetitive processing of turbo equalization, and outputs the selected value as a first selected noise variance value; a second noise variance selector that selects either one of the first noise variance estimation value or the second noise variance estimation value, or selects the mean value of the first noise variance estimation value and the second noise variance estimation value, based on a second judgment criterion that is different between the first round and the second or subsequent round of repetitive processing of the turbo equalization, and outputs the selected value as a second selected noise variance value; a filter coefficient calculator that calculates a filter coefficient for the MMSE filter by using the first selected noise variance value; and a logarithmic likelihood ratio calculator that calculates a logarithm of likelihood ratio to be used for low density parity check (LDPC) decoding by using the second selected noise variance value.