An Area-Efficient and Low-Power Multirate Decoder for Quasi-Cyclic Low-Density Parity-Check Codes

The quasi-cyclic low-density parity-check (QC-LDPC) codes are widely applied in digital broadcast and communication systems. However, the decoders are still difficult to be put into practice due to their large area and high power, especially in the wireless mobile devices. This paper presents an improved all-purpose multirate iterative decoder architecture for QC-LDPC codes, which can largely reduce their area and power. The architecture implements the normalized min-sum algorithm, rearranges the original two-phase message-passing flow, and adopts an efficient quantization method for the second minimum absolute values, an optimized storing scheme for the position indexes and signs, and an elaborate clock gating technique for substantive memories and registers. It is also configurable for any regular and irregular QC-LDPC codes, and can be easily tuned up to different code rates and code word lengths. The chip is fabricated in an SMIC 0.18- six-metal-layer standard CMOS technology. It attains a throughput of 104.5 Mb/s, and dissipates an average power of 486 mW at 125 MHz, and 15 decoding iterations. The core area is only 9.76 mm
²
. The chip has been applied into the China digital terrestrial/television multimedia broadcasting system.