Multilevel coded modulation for unequal error protection and multistage decoding - Part I: Symmetric constellations

In this paper, theoretical upper bounds and computer simulation results on the error performance of multilevel block coded modulations for unequal err or protection (UEP and multistage decoding are presented. The paper is divi ded into two parts. In part I, symmetric constellations are considered, whi le in the sequel, asymmetric constellations are analyzed, It is shown that nonstandard signal set partitionings and multistage decoding provide excell ent UEP capabilities beyond those achievable with conventional coded modula tion. The coding scheme is designed in such a way that the most important i nformation bits have a lower error rate than other information bits, The la rge effective error coefficients, normally associated with standard mapping by set partitioning, are reduced by considering nonstandard partitionings of the underlying signal set. The bits-to-signal mappings induced by these partitionings allow the use of soft-decision decodings of binary block code s. Moreover, parallel operation of some of the staged decoders is possible, to achieve high data rate transmission, so that there is no error propagat ion between these decoders. Hybrid partitionings are also considered that t rade off increased intraset distances in the last partition levels with lar ger effective error coefficients in the middle partition levels. The error performance of specific examples of multilevel codes over 8-PSK and 63-QAM signal sets are simulated and compared with theoretical upper bounds on the error performance.