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 error protection (UEP) and multistage decoding are presented. It is shown that nonstandard signal set partitionings and multistage decoding provide excellent UEP capabilities beyond those achievable with conventional coded modulation. The coding scheme is designed in such a way that the most important information bits have a lower error rate than other information bits. The large 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 decoding of binary block codes. Moreover, parallel operation of some of the staged decoders is possible, to achieve high data rate transmission, so that there is no error propagation between these decoders. Hybrid partitionings are also considered that trade off increased intraset distances in the last partition levels with larger effective error coefficients in the middle partition levels. The error performance of specific examples of multilevel codes over 8-PSK and 64-QAM signal sets are simulated and compared with theoretical upper bounds on the error performance

Communication Over MIMO Broadcast Channels Using Lattice-Basis Reduction

A simple scheme for communication over MIMO broadcast channels is introduced which adopts the lattice reduction technique to improve the naive channel inversion method. Lattice basis reduction helps us to reduce the average transmitted energy by modifying the region which includes the constellation points. Simulation results show that the proposed scheme performs well, and as compared to the more complex methods (such as the perturbation method) has a negligible loss. Moreover, the proposed method is extended to the case of different rates for different users. The asymptotic behavior of the symbol error rate of the proposed method and the perturbation technique, and also the outage probability for the case of fixed-rate users is analyzed. It is shown that the proposed method, based on LLL lattice reduction, achieves the optimum asymptotic slope of symbol-error-rate (called the precoding diversity). Also, the outage probability for the case of fixed sum-rate is analyzed.Comment: Submitted to IEEE Trans. on Info. Theory (Jan. 15, 2006), Revised (Jun. 12, 2007

Multilevel Block Coded 8-PSK Modulations Using Unequal Error Protection Codes for the Rayleigh Fading Channel

This paper introduces new block coded 8-PSK modulations with unequal error protection (UEP) capabilities for Rayleigh fading channels. The design of efficient block coded modulations (BCM) over 8-PSK signal sets, for the specific purpose of UEP, over Rayleigh fading channels is considered. UEP is desirable in communications systems where part of the source information is more important, or error sensitive, such as the transmission of coded speech and data broadcasting. The proposed block modulation codes are based on the multilevel construction of Imai and Hirakawa (1977). It is shown that the use of binary linear UEP (LUEP) codes as component codes in one or two of the encoding levels provides, in addition to superior UEP capabilities, a higher error performance, at the expense of a very modest reduction in bandwidth efficiency, with respect to conventional multilevel codes. Computer simulation results show that, over a Rayleigh fading channel, a significant improvement in the coding gain is obtained by the use of binary LUEP codes as constituent codes in the multilevel construction

King of the Hill Positional Dynamics in Contests

In a contest with positional dynamics between an incumbent and a challenger i) inequality of power may magnify conflicts, ii) more severe conflicts can go together with lower turnover of incumbents, and iii) power can be self defeating as cost advantages can reduce pay-offs. These three propositions of our paper are contrary to the implications of static conflict models. They follow from incorporating positional dynamics into the standard static approach. Such positional dynamics are relevant for competition in battlefields, politics, and market places.Contests;political stability;war;incumbency advantage

QPSK Block-Modulation Codes for Unequal Error Protection

Unequal error protection (UEP) codes find applications in broadcast channels, as well as in other digital communication systems, where messages have different degrees of importance. Binary linear UEP (LUEP) codes combined with a Gray mapped QPSK signal set are used to obtain new efficient QPSK block-modulation codes for unequal error protection. Several examples of QPSK modulation codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes, of the same rate and length, are given. In the new constructions of QPSK block-modulation codes, even-length binary LUEP codes are used. Good even-length binary LUEP codes are obtained when shorter binary linear codes are combined using either the well-known |u¯|u¯+v¯|-construction or the so-called construction X. Both constructions have the advantage of resulting in optimal or near-optimal binary LUEP codes of short to moderate lengths, using very simple linear codes, and may be used as constituent codes in the new constructions. LUEP codes lend themselves quite naturally to multistage decoding up to their minimum distance, using the decoding of component subcodes. A new suboptimal two-stage soft-decision decoding of LUEP codes is presented and its application to QPSK block-modulation codes for UEP illustrated