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International Journal of

Recent Trends in Engineering

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International Journal of Recent Trends in Engineering (IJRTE)

ISSN 1797-9617

Volume 1, Number 3, May 2009

Issue on Electrical & Electronics

Page(s): 47-51

Application of Scaling factors for MAP and SOVA for Robust Performance in Forward Error Correction

T.Gnanasekaran and Dr K.Duraiswamy

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Abstract

This paper proposes a method to improve performance of Maximum A-posteriori Probability (MAP) algorithm and Soft Output Viterbi (SOVA) algorithm. Previously the performance of turbo decoder is improved by means of scaling the channel reliability value (LC). In the proposed method, scaling the extrinsic information of both decoders of turbo decoder gives better performance. Optimum scaling factor is found from empirical value. The optimum scaling factor is extended for traditional turbo decoder called Equal error protection (EEP) and Unequal error protection (UEP).The simulation result shows the modified MAP and SOVA improves the Bit Error Rate (BER) both EEP and UEP. In UEP the class 1 and class 2 gained 0.8 dB and 0.6 dB respectively in AWGN channel where as in fading channel class 1 and 2 gained 0.4 dB and 0.6 dB respectively.

Index Terms

AWGN, MAP, SOVA, Turbo Code, UEP

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