Performance analysis of PUM codes

Partial unit memory (PUM) codes are low complexity, nonbinary, multimemory codes with competitive performance to standard recursive systematic convolutional (RSC) codes. We design turbo codes using parallel concatenation of two identical systematic recursive PUM codes and compare their performance to equivalent standard RSC-based turbo codes. Our analysis of extrinsic information transfer (EXIT) charts shows that the designed PUM-based turbo codes outperform equivalent standard turbo codes at the error-floor region, with comparable performance in the waterfall region. Simulated bit error rate (BER) performance curves of the two codes confirm the behavior predicted using EXIT charts. For example, our PUM-based turbo code design outperforms the standard Inmarsat turbo code by 0.5 dB for the same number of decoder iterations. Similarly, the UMTS standardized turbo code loses roughly 0.5 dB in the error-floor region compared to the PUM-based turbo code of same complexity.