Fast Log-Likelihood Ratio (LLR) Computation for Decoding High-Order and High-Dimensional Modulation Schemes

摘要

A method receives the symbol transmitted over a channel, selects, from a constellation of codewords, a first codeword neighboring the received symbol and a set of second codewords neighboring the first codeword, and determines a relative likelihood of each second codeword being the transmitted symbol with respect to a likelihood of the first codeword being the transmitted symbol. Next, the method determines an approximation of a log-likelihood ratio (LLR) of each data bit in the received symbol as a log of a ratio of a sum of the relative likelihoods of at least some of the second codewords having the same value of the data bit to a sum of the relative likelihoods of at least some of the second codewords having different value of the data bit and decodes the received symbol using the LLR of each data bit.

主权项

1. A method for decoding a symbol transmitted over a channel, wherein the symbol is encoded and modulated to include data bits and parity bits, comprising:
receiving the symbol transmitted over a channel, wherein the received symbol includes the transmitted symbol modified with noise of the channel; selecting, from a constellation of codewords, a first codeword neighboring the received symbol and a set of second codewords neighboring the first codeword; determining a relative likelihood of each second codeword being the transmitted symbol with respect to a likelihood of the first codeword being the transmitted symbol; determining an approximation of a log-likelihood ratio (LLR) of each data bit in the received symbol as a log of a ratio of a sum of the relative likelihoods of at least some of the second codewords having the same value of the data bit to a sum of the relative likelihoods of at least some of the second codewords having different value of the data bit; and decoding the received symbol using the LLR of each data bit, wherein steps of method are performed using a processor of a decoder.