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Modelling Unequal Error Protection in BICM Systems.


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Chowdhury, Thomas (2010). Modelling Unequal Error Protection in BICM Systems. Mémoire. Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 74 p.

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Bit-interleaved coded modulation (BICM) is one of the popular modulation techniques used in most of the existing wireless communication standards, e.g., HSPA, IEEE 802.11a/g/n etc. In BICM, the channel encoder and the modulator are separated by a bit-level interleaver which allows the designer to choose the code rate and the constellation independently. BICM maximizes the code diversity, and therefore is better than trellis coded modulation in fading channel. However its flexibility and ease of implementation makes it popular in non-fading channel too. In BICM, receiver considers the reliability metrics of the transmitted bit which are calculated in the form of log likelihood ratios (L-values) and the main goal of this research is to find the probabilistic model of L-values that allows for a simple and accurate evaluation of the performance of (BER) considering the effect of unequal error protection. To this end we proceed in two steps. First we replace the exact form of the PDFs of L-values with simple to manipulate Gaussian functions. Next we interpret these simplified form into the BER evaluation based on the saddle point approximation. To deal with multiple terms appearing in the expressions which complicate the solution of the so-called saddlepoint equation; we use quadratic approximations which lead to the closed form solutions. The resulting formulas are validated in the case of M-QAM and M-PSK constellation with arbitrary labellings e.g. Gray, Set Partitioning (SP), Modified Set Partitioning Labelling (MSP) and Mixed labelling (ML).

Type de document: Thèse Mémoire
Directeur de mémoire/thèse: Szczecinski, Leszek
Mots-clés libres: modulation codée par bit entrelacé; BICM; modèles probabilistes; approximation du point de selle; transmission
Centre: Centre Énergie Matériaux Télécommunications
Date de dépôt: 06 août 2014 20:55
Dernière modification: 05 nov. 2015 19:13
URI: https://espace.inrs.ca/id/eprint/2135

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