A unified turbo/Viterbi channel decoder for 3GPP mobile wireless in 0.18-μm CMOS

A channel decoder chip compliant with the 3GPP mobile wireless standard is described. It supports both data and voice calls simultaneously in a unified turbo/Viterbi decoder architecture. For voice services, the decoder can process over 128 voice channels encoded with rate 1/2 or 1/3, constraint length 9 convolutional codes. For data services, the turbo decoder is capable of processing any mix of rate 1/3, constraint length 4 turbo encoded data streams with an aggregate data rate of up to 2.5 Mb/s with 10 iterations per block (or 4.1 Mb/s with six iterations). The turbo decoder uses the logMAP algorithm with a programmable logsum correction table. It features an interleaver address processor that computes the 3GPP interleaver addresses for all block sizes enabling it to quickly switch context to support different data services for several users. The decoder also contains the 3GPP first channel de-interleaving function and a post-decoder bit error rate estimation unit. The chip is fabricated in a 0.18-μm six-layer metal CMOS technology, has an active area of 9 mm², and has a peak clock frequency of 110.8 MHz at 1.8 V (nominal). The power consumption is 306 mW when turbo decoding a 2-Mb/s data stream with ten iterations per block and eight voice calls simultaneously.