Reconfigurable hardware architectures for sequential and hybrid decoding

A novel reconfigurable sequential decoder architecture based on the Fano algorithm is presented in which the constraint length, the threshold spacing, and the time-out threshold are all run time reconfigurable. To maximize decoding performance, a maximum possible backward depth (of a whole frame) is performed. This is achieved by using shift registers combined with memory to store the information of an entire visited path. A field-programmable gate array) prototype of the decoder is built and actual hardware decoding performances in terms of decoding speeds, bit error rates (BERs), and buffer overflow rates, are obtained and comparisons made. To overcome the decoding delay that is inherent in sequential decoders, a hybrid scheme, including simple block codes and cyclic redundancy check is proposed to limit the number of backward search operations that the sequential decoder has to execute. As a result, a significant reduction in decoding delay and buffer overflow rate is achieved while maintaining comparative decoding performance in terms of BER.