Gradient BitFlipping LDPC Decoder for ATSC 3.0 This paper presents the mathematical representation and the numerical results of the Gradient BitFlipping Algorithm (GBF) that is derived from the BitFlipping Algorithm (BFA).The experimental simulation results for the proposed decoder of the LowDensity ParityCheck (LDPC) codes of ATSC 3.0 demonstrate an enhancement of up to 3.55 dB in error correction performance without an increase in the decoding complexity. The proposed decoder has the ability to decode an erroneous LDPC message in fewer iterations than the traditional BFA due to the employment of the values of the LogLikelihood Ratio (LLR) as an input, unlike the BFA that uses binary values ignoring the channel estimation output.

Improved MinSum Algorithm for RaptorLike LDPC codes in ATSC 3.0 In order to improve the performance of lowrate LDPC codes, ATSC 3.0 adopted raptorlike structure. Minsum (MS) algorithm and improved versions can be used directly, but their performance on raptorlike LDPC codes are disappointing. In this paper, we introduce an improved minsum(IMS) algorithm for raptorlike LDPC codes in ATSC 3.0. Simulation results of frame error rate show that the IMS algorithm not only has a noticeable gain in waterfall region over normalized minsum (NMS) algorithm and offset minsun (OMS) algorithm, but also has almost the same time complexity. Different from OMS algorithm, the proposed algorithm is not sensitive to the imperfect channel estimation. Meanwhile, the IMS algorithm is easier to realize than those variable factors based algorithms.