On the interpretation of the APP algorithm as an LLR filter

Author

Land, Ingmar ; Hoeher, Peter ; Sorger, Ulrich

Author_Institution

Inf. & Coding Theory Lab., Kiel Univ., Germany

fYear

2000

fDate

2000

Firstpage

415

Abstract

A channel decoder employing the a posteriori probability (APP) algorithm can be formulated so that its inputs and its outputs are log-likelihood-ratios (LLR): channel LLRs of the code bits are accepted, and a posteriori LLRs of the info bits and/or the code bits are delivered. Since decoding improves the reliability, the APP algorithm can be interpreted as a non-linear filter for LLRs. The “LLR amplification” depends on the distance properties of the channel code; for high signal-to-noise ratios it is dominated by the minimum distance

Keywords

binary codes; channel coding; convolutional codes; decoding; filtering theory; linear codes; nonlinear filters; probability; APP algorithm; LLR amplification; LLR filter; SNR; a posteriori LLR; a posteriori probability algorithm; binary linear convolutional encoder; channel LLR; channel code; channel decoder; code bits; decoding; distance properties; high signal-to-noise ratio; information bits; log-likelihood-ratios; minimum distance; nonlinear filter; Communications technology; Concatenated codes; Convolution; Convolutional codes; Filtering; Filters; Iterative decoding; Memoryless systems; Signal to noise ratio; Transfer functions;

fLanguage

English

Publisher

ieee

Conference_Titel

Information Theory, 2000. Proceedings. IEEE International Symposium on

Conference_Location

Sorrento

Print_ISBN

0-7803-5857-0

Type

conf

DOI

10.1109/ISIT.2000.866713

Filename

866713