SOFT-INPUT SOFT-OUTPUT EUCLIDEAN DISTANCE METRIC ITERATIVE DECODER FOR LDPC CODES

FARRELL, P. G.; CASTIÑEIRA MOREIRA, J.

Santa Fe

Congreso; AST 37 JAIIO; 2008

JAIIO

In this paper a soft-input soft-output (SISO) Euclidean distance metric decoder for a LDPC code is presented. This decoding algorithm performs very close to the original decoding algorithm introduced by D. J. C. MacKay and R. M. Neal, reducing highly the complexity and overflow and underflow effects of the iterative procedure, being suitable for practical implementations in programmable logic technology like FPGA. On the other hand, the decoder does not require the knowledge of the channel information. Simulations of the BER performance are provided for the Additive White Gaussian Channel. The proposed algorithm can be simplified to operate by using only additions and comparisons, if a correction factor involved in the calculations is not taken into account. This simplification sometimes can produce degradation in the BER performance. Exact application of the calculations in the proposed algorithm drives to the best BER performance, requiring the use of the correction factor, which can be easily implemented by means of a look-up table.