Source Correlation in Randomly Excited Complex Media

International audienceWhen dealing with modal representations of the Green's function of a complex medium, the modal coefficients are often assimilated to random variables, where statistical independence is justified on heuristic arguments supported by the complexity of the propagation in multiple-scattering scenarios. This letter addresses this assumption when the randomness originates from an uncertain positioning of the sources, proving under what conditions the modal coefficients can be regarded as uncorrelated, showing that this special condition should not be taken for granted, even in complex media

Exploiting 2-Dimensional Source Correlation in Channel Decoding with Parameter Estimation

Traditionally, it is assumed that source coding is perfect and therefore, the redundancy of the source encoded bit-stream is zero. However, in reality, this is not the case as the existing source encoders are imperfect and yield residual redundancy at the output. The residual redundancy can be exploited by using Joint Source Channel Coding (JSCC) with Markov chain as the source. In several studies, the statistical knowledge of the sources has been assumed to be perfectly available at the receiver. Although the result was better in terms of the BER performance, practically, the source correlation knowledge were not always available at the receiver and thus, this could affect the reliability of the outcome. The source correlation on all rows and columns of the 2D sources were well exploited by using a modified Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm in the decoder. A parameter estimation technique was used jointly with the decoder to estimate the source correlation knowledge. Hence, this research aims to investigate the parameter estimation for 2D JSCC system which reflects a practical scenario where the source correlation knowledge are not always available. We compare the performance of the proposed joint decoding and estimation technique with the ideal 2D JSCC system with perfect knowledge of the source correlation knowledge. Simulation results reveal that our proposed coding scheme performs very close to the ideal 2D JSCC system

Variable Length Space Time Coded Modulation

A Variable Length Space Time Coded Modulation (VL-STCM) scheme capable of simultaneously providing coding, multiplexing and diversity gains is proposed. The scheme advocated achieves its best performance for correlated sources, where the source symbols exhibit a nonuniform probability of occurrence. The source symbols are encoded using an optimal trellis encoder into variablelength modulated signals and mapped to both the spatial and time domains. More explicitly, the proposed VL-STCM arrangement is a jointly designed source coding, channel coding, modulation and spatial diversity/multiplexing scheme. It is shown that the higher the source correlation, the higher the achievable performance gain of the scheme. Furthermore, the performance of the VL-STCM scheme is about 6 dB better than that of the Fixed Length STCM (FL-STCM) benchmarker at a source symbol error ratio of 10?4