A Low-Power VLSI Architecture for Turbo Decoding

Presented in this paper is a low-power architecture for turbo decodings of parallel concatenated convolutional codes. The proposed architecture is derived via the concept of block-interleaved computation followed by folding, retiming and voltage scaling. Block-interleaved computation can be applied to any data processing unit that operates on data blocks and satisfies the following three properties: 1.) computation between blocks are independent, 2.) a block can be segmented into computationally independent sub-blocks, and 3.) computation within a sub-block is recursive. The application of block-interleaved computation, folding and retiming reduces the critical path delay in the add-compare-select (ACS) kernel of MAP decoders by 50% - 84% with an area overhead of 14% - 70%. Subsequent application of voltage scaling results in up to 65% savings in power for block-interleaving depth of 6. Experimental results obtained by transistor-level timing and power analysis tools demonstrate power savings of 20% - 44% for a block-interleaving depth of 2 in 0.25μm CMOS process.