Convergence performance and EXIT analysis of 4-state partially-systematic Turbo codes

The error-rate performance of punctured turbo codes may be significantly improved by puncturing data symbols as well as parity symbols, yielding partially-systematic turbo codes (PSTCs). In this paper, it is shown that relatively simple 4-state PSTCs are able to achieve convergence (i.e., waterfall) performance that is 0.26 dB from the binary channel capacity limit at rate 1/2 and 0.18 dB from the limit at rate 8/9. It is also demonstrated that extrinsic information transfer (EXIT) charts do not accurately predict convergence performance for 4-state PSTCs.