Using Exit Charts to Develop an Early Stopping Criterion for Turbo Decoding

Early stopping criteria are used to determine when additional decoder iterations result in little or no improvement in the bit- error-rate (BER) at the output of a Turbo decoder. This paper proposes a stopping criterion based on Extrinsic Information Transfer (EXIT) charts. The generation and properties of EXIT charts are discussed. Convergence and BER predictions obtained using EXIT charts are compared to results obtained using Turbo decoder simulation. Finally this paper describes the use of convergence and BER predictions obtained from EXIT charts to develop a stopping criterion for Turbo decoding