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Performance of Turbo Coded 64-QAM with Joint Source Channel Decoding, Adaptive Scaling and Prioritised Constellation Mapping

Authors:
Tulsi Pawan Fowdur
Yogesh Beeharry
K.M. Sunjiv Soyjaudah

Keywords: Turbo Code; QAM; JSCD; SDR; Priortised Mapping.

Abstract:
Turbo coded 64-QAM systems have been adopted by standards such as CDMA-2000 and Long Term Evolution (LTE) to achieve high data rates. Although several techniques have been developed to improve the performance of Turbo coded QAM systems, combinations of these techniques to produce hybrids with better performances, have not been fully exploited. This paper proposes a combination of Joint Source Channel Decoding (JSCD), adaptive Sign Division Ratio (SDR) based scaling and prioritised constellation mapping, to improve the performance of Turbo coded 64-QAM. JSCD exploits a-priori source statistics at the decoder side and SDR based scaling provides a scale factor for the extrinsic information as well as a stopping criterion. Additionally, prioritised constellation mapping exploits the inherent Unequal Error Protection (UEP) characteristic of the 64-QAM constellation and provides greater protection to the systematic bits of the Turbo encoder. Simulation results show that at Bit Error Rates (BERs) above 10-1, the combination of these three techniques achieves an average gain of 2.5 dB over a conventional Turbo coded 64-QAM system. However, at BERs below 10-1, the combination of only JSCD and SDR scaling provides an average gain of 1 dB.

Pages: 35 to 41

Copyright: Copyright (c) IARIA, 2013

Publication date: April 21, 2013

Published in: conference

ISSN: 2308-4022

ISBN: 978-1-61208-263-9

Location: Venice, Italy

Dates: from April 21, 2013 to April 26, 2013