Improved SOVA and APP decoding algorithms for serial concatenated codes

Chuan Xiu Huang, Ali Ghrayeb

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In this paper, we propose a simple remedy for the exaggerated extrinsic information produced by the soft-output Viterbi algorithm (SOVA). We argue that what leads to these optimistic extrinsic values is the inherent strong correlation between the intrinsic information (input to the SOVA) and extrinsic information (output of the SOVA). The proposed remedy involves employing two attenuators, one applied to the immediate output of the SOVA and another applied to the extrinsic information before it is passed to the other decoder (assuming iterative decoding). We examine the modified SOVA (MSOVA) on additive white Gaussian noise (AWGN) and fading channels for serial concatenated codes (SCCs). We show that the MSOVA provides substantial performance improvements over both channels. For example, it provides improvements of about 0.8 to 1.0 dB at P b = 10-5 in AWGN, and about 1.4 to 2.0 dB at Pb = 10-5 on fading channels, all relative to the SOVA. We extend the proposed modifications to the aposteriori probability (APP) algorithm with favorable results. We demonstrate that the modified APP (MAPP) provides performance improvements between 0.3 to 0.6 dB at Pb = 10 -5 relative to the APP.

Original languageEnglish
Title of host publicationGLOBECOM'04 - IEEE Global Telecommunications Conference
Number of pages5
Publication statusPublished - 2004
Externally publishedYes
EventGLOBECOM'04 - IEEE Global Telecommunications Conference - Dallas, TX, United States
Duration: 29 Nov 20043 Dec 2004


OtherGLOBECOM'04 - IEEE Global Telecommunications Conference
CountryUnited States
CityDallas, TX


ASJC Scopus subject areas

  • Engineering(all)

Cite this

Huang, C. X., & Ghrayeb, A. (2004). Improved SOVA and APP decoding algorithms for serial concatenated codes. In GLOBECOM'04 - IEEE Global Telecommunications Conference (Vol. 1, pp. 189-193)