A modular bit-serial architecture for large constraint length Viterbi decoding

A node-parallel Viterbi decoding architecture with bit-serial processing and communication is presented. This structure allows short constraint-length decoders to be expanded, without loss of throughput, to implement a Viterbi decoder of larger constraint length. A variety of generating codes can be accommodated by appropriate wiring of the decoder. Bit-serial communication between processing nodes requires only a single wire; thus on-chip and off-chip wiring requirements are quite small. A constraint-length K=4 `proof of concept´ chip was developed using 9860 transistors in 3-μm CMOS. The circuit supports any rate-1/2 or rate-1/3 code with 8-level soft decision. Performance measurements on two rate-1/2 interconnected chips confirm the expected 3.8-dB coding gain at a 10^-4 error rate