A reduced-complexity demapping algorithm for BICM-ID systems

Gaussian Mixture Learning for LDPC Coded BICM Receivers With Blanking Nonlinearity

“…Hence, we focus on the calculation of the extrinsic LLR L e,dem in the MAP demodulator, which is directly related to complexity comparison for both two demapping schemes. For the standard MAP demodulator, the calculation of L e,dem in equation 7requires a complexity on the order of O(2 M ), since the channel conditional probability p(Y k |S k ) needs 2 M times Euclidean distance calculations for all the 2 M constellation points [30]. Moreover, the maximization operation involves 2 M − 2 comparisons, which is the same as that of the GMM-based demodulator.…”

Universal soft demodulation schemes for M ‐ary phase shift keying and quadrature amplitude modulation

“…The complexity of the ML scheme can be reduced by eliminating the log and exponential operations, resulting in a scheme called Max-log soft demodulation, but this scheme still has exponential-order complexity. A number of soft demodulation schemes have been proposed to reduce the complexity [3][4][5][6][7][8][9][10][11][12][13][14][15]; these can be classified into three classes as follows.…”

“…The third class of soft demodulation schemes comprises those based on a modified Max method, which eliminates the searching process to find the symbol with the minimum distance among the 2 m symbols in the constellation [12][13][14][15][16]. These methods determine the location of its detected symbol by comparison with the HDT lines, thereby requiring only m comparisons to find the nearest symbol, i.e.…”

“…Afterwards, another equation is applied to each bit to find the symbol with opposite bit value to that of the nearest symbol, so that a Max equation can be applied. Especially, an iterative demapping algorithm for BICM-ID was proposed in [13], and thus the idea in [12] is a special case of [13] in the absence of a priori log-likelihood ratios (LLRs) obtained from the decoder.…”

“…This may require multiple demodulators, and the system may subsequently incur hardware complexity. For this reason, universal demodulators have been presented [10,12,13,17].…”