Fidelity Charts and Stopping/Termination Criteria for Iterative Multiuser Detection

Conference: TURBO - CODING - 2006 - 4th International Symposium on Turbo Codes & Related Topics; 6th International ITG-Conference on Source and Channel Coding
04/03/2006 - 04/07/2006 at Munich, Germany

Proceedings: TURBO - CODING - 2006

Pages: 6Language: englishTyp: PDF

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Shepherd, David P.; Reed, Mark C. (National ICT Australia, Australian National University, Canberra, Australia)
Brännström, Fredrik (Dept. of Signals and Systems, Chalmers University of Technology, 412 58 Göteborg, Sweden)

An iterative multiuser detection (IMUD) receiver is considered for a code-division multiple-access (CDMA) system with turbo codes. Fidelity is considered as a metric for convergence analysis and an approximation of fidelity as a function of variance of the log-likelihood ratios is introduced. Fidelity charts are compared with extrinsic information transfer (EXIT) charts as tools for convergence analysis and a close approximation of the relationship between fidelity and mutual information is proposed. We then use this function to approximate a closed form expression for the EXIT function of an interference canceller. Further, we propose a new stopping criterion for the turbo decoder and the IMUD receiver which achieves complexity saving of up to 50% over conventional designs.