Search

Design and test results for a fully integrated translinear tail-biting MAP error-control decoder are presented. Decoder designs have been reported for various applications which make use of analog computation, mostly for Viterbi-style decoders. MAP decoders are more complex, and are necessary components of powerful iterative decoding systems such as TUrbo codes. Analog circuits may require less area and power than digital implementations in high-speed iterative applications. Our (8, 4) Hamming decoder, implemented in an AMI 0.5-µm process, is the first functioning CMOS analog MAP decoder. While designed to operate in subthreshold, the decoder also functions above threshold with a small performance penalty. The chip has been tested at bit rates up to 2 Mb/s, and simulations indicate a top speed of about 10 Mb/s in strong inversion. The decoder circuit size is 0.82 mm², and typical power consumption is 1 mW at 1 Mb/s. Index Terms—Analog decoding; error-control codes; iterative decoders; maximum a posteriori (MAP) decoding; translinear circuits. [ABSTRACT FROM AUTHOR]

Abstract: We present a low power, dual-function encode/decode circuit for a class of reversible low-density parity-check codes. The circuit offers a small silicon footprint, by operating as an analog decoder and reusing resources to switch into a digital encode mode. In order to achieve this behaviour from a single circuit we have developed mode-switching gates. These logic gates are able to switch between analog (soft) and digital (hard) computation. Only a small overhead in circuit area is required to transform the analog decoder into a full codec. The encode operation can be performed two orders of magnitude faster than the decode operation, making the circuit suitable for full-duplex applications. The low power and small area of the circuit make it an attractive option for battery powered wireless devices. Circuit simulations indicate a decoding latency of with negligible SNR loss with respect to digital sum–product decoders. [Copyright &y& Elsevier]