Irregular M-SC-MPC codes for wireless applications

In this paper, we elaborate on our previous proposal of Multiple Serially-Concatenated Multiple-Parity-Check (M-SC-MPC) codes, that are a class of structured LDPC codes obtained as the serial concatenation of M very simple codes. They have been shown able to achieve good error correction performance while allowing the usage of a very simple encoder architecture, and to compare favorably with the previously proposed M-SC-SPC codes, based on Single Parity-Check components. However, we have observed that, in order to avoid error floors in the original M-SC-MPC codes, rather high values of M are needed, that may produce non-optimal performance in the waterfall region. So, we propose a solution to improve the error rate of M-SC-MPC codes without renouncing their structural simplicity. The proposed technique, based on the cancellation of some parity checks within the MPC component codes, permits us to design irregular codes and, in several cases, to reduce the number of nodes having short local cycles in their Tanner graph. We design codes compliant with the IEEE 802.16e specification, and compare them with the codes included in the standard.