A Reconfigurable LDPC Decoder Optimized for 802.11n/ac Applications

This paper presents a high data-rate low-density parity-check (LDPC) decoder, suitable for the 802.11n/ac (WiFi) standard. The innovative features of the proposed decoder relate to the decoding algorithms and the interconnection between the processing elements. The reduction of the hardware complexity of decoders based on the min-sum (MS) algorithms comes at the cost of performance degradation, especially at high-noise regions. We introduce more accurate approximations of the log sum-product algorithm that also operate well for low signal-to noise ratio values. Telecommunication standards, including WiFi, support more than one quasi-cyclic LDPC codes of different characteristics, such as codeword length and code rate. A proposed design technique derives networks, capable of supporting a variety of codes and efficiently realizing connectivity between a variable number of processing units, with a relatively small hardware overhead over the single-code case. As a demonstration of the proposed technique, we implemented a reconfigurable network based on barrel rotators, suitable for LDPC decoders compatible with WiFi standard. Our approach achieves low complexity and high clock frequency, compared with related prior works. A 90-nm application-specified integrated circuit implementation of the proposed high-parallel WiFi decoder occupies 4.88 mm2 and achieves an information throughput rate of 4.5 G bit/s at a clock frequency of 555 MHz.