Unequal Error Protection Scheme Based on Implicit Partial Product-LDPC Codes

This paper proposes an unequal error protection (UEP) scheme based on implicit partial product-LDPC codes. All rows of the source data array are encoded by a low-density parity-check (LDPC) code, while only a prescribed subset of information columns is further protected by a Bose-Chaudhuri-Hocquenghem (BCH) code. The check information generated by the column code is not transmitted explicitly. Instead, it is superimposed on the row LDPC codewords through a free-ride coding mechanism. In this way, the selected columns, referred to as the most important data (MID), are protected by both the row code and the column code, whereas the remaining columns, referred to as the less important data (LID), are protected only by the row code. A turbo-like iterative decoding algorithm is then adopted for the proposed scheme, consisting of free-ride decoding, row decoding, column decoding, and row re-decoding. We further present an approximate performance characterization for the doubly protected MID and a genie-aided lower bound for the singly protected LID. Simulation results show that the proposed scheme provides a substantial reliability gain for the MID, while the LID performance is not sacrificed and can even outperform that of standalone LDPC coding in the medium-to-high signal-to-noise ratio (SNR) region.