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Low-density parity check (LDPC) codes have gained much attention due to their use of various belief-propagation (BP) decoding algorithms to impart excellent error-correcting capability. The BP decoders are quite simple; however, their computation-intensive and repetitive process prohibits their use in energy-sensitive applications such as sensor networks. Bit flipping-based decoding algorithms, especially implementation-efficient, reliability ratio-based, weighted bit-flipping (IRRWBF) decoding; have shown an excellent tradeoff between error-correction performance and implementation cost. In this paper, we show that with IRRWBF, iterative re-computation can be replaced by iterative selective updating. When compared with the original algorithm, simulation results show that, decoding speed can be increased by 200 to 600 percent , as the number of decoding iterations is increased from 5 to 1,000. The decoding steps are broken down into various stages such that the update operations are mostly of the single-instruction, multiple-data (SIMD) type. In this paper, we show that by using Intel Wireless MMX 2 accelerating technology in the proposed algorithm, the speed increased by 500 to 1,500 percent. The results of implementing the proposed scheme using an Intel/Marvell PXA320 (806 MHz) CPU are presented. The proposed scheme can be used effectively in real-time LDPC codes for energy-sensitive mobile devices.