Diversity techniques for a free-space optical communication system in correlated log-normal channels

International audiencePerformance analysis of free-space optical (FSO) communication systems in different channel conditions has gained significant attention in literature. Nevertheless, most existing studies consider uncorrelated channel conditions. An uncorrelated channel requires sufficient spacing between transmitters and limits the receiver field of view and link distance. However, this might not be feasible in all applications. Thereby, this paper studies repetition code (RC) and orthogonal space time block code (OSTBC) performance in correlated log-normal FSO channels using intensity modulation and direct detection. An approximate analytical expressions using moment generating function for the average bit error probability are derived. Our simulation results show that RCs are superior to OSTBCs in correlated channel conditions

Spatial Modulation applied to Optical Wireless Communications in Indoor LOS Environments

International audienceIn this paper, we study the performance of Spatial Modulation (SM) applied to optical wireless communications (OWC) in indoor environments with line-of-sight (LOS) characteristics. To this end, we consider setup scenarios with different numbers of optical transmitters and receivers which are arranged within a room. SM is compared to repetition coding (RC). Because RC is known to achieve very good performance in OWC systems due to the use of intensity modulation and the resulting constructive superposition of the power signals. The results show that SM can outperform RC when high spectral efficiencies are desirable, e.g. 4 bit/s/Hz and greater, since it can operate with reduced signal modulation orders by conveying additional data bits in the spatial domain. We also demonstrate that SM benefits from receive-diversity to a larger extent while at the same time requiring less computational complexity. Furthermore, we give a general framework to numerically approximate the average bit error probability of both SM and RC

Sphere Decoding for Spatial Modulation

International audienceIn this paper, Sphere Decoding (SD) algorithms for Spatial Modulation (SM) are developed to reduce the computational complexity of Maximum-Likelihood (ML-) optimum detectors, which foresee an exhaustive search of the whole search space and have a complexity that linearly increases with the product of number of transmit-antenna, receive-antenna, and size of the modulation scheme. Three SDs specifically designed for SM are proposed and analyzed in terms of Bit Error Probability (BEP) and computational complexity. By judiciously choosing some key parameters, e.g., the radius of the sphere centered around the received signal, it is shown that the proposed algorithms offer the same BEP as ML-optimum detection, with a significant reduction of the computational complexity. Also, it is shown that none of the proposed SDs is always superior to the others, but the best SD to use depends on the system setup, i.e., the number of transmit-antenna, receive-antenna, and the size of the modulation scheme. The computational complexity trade-off offered by the proposed solutions is studied via analysis and simulation, and numerical results are shown to validate our findings

The performance of space shift keying for free-space optical communications over turbulent channels

International audienceThis paper evaluates the performance of space shift keying (SSK) free-space optical communication (FSO) over moderate and strong turbulent channels. It has been shown previously that repetition codes (RCs) using intensity modulation with direct detection techniques are superior to SSK system for a spectral efficiency of 1 bit/s/Hz. It is shown in this study that SSK outperforms RCs using M-ary pulse amplitude modulation for spectral efficiencies of 3 bits/s/Hz or larger. Analytical expressions for the bit error rate for the SSK system under study are derived and extensive simulation results corroborate the correctness of the conducted analysis. The performance of space shift keying for free-space optical communications over turbulent channels. Available from: https://www.researchgate.net/publication/275647868_The_performance_of_space_shift_keying_for_free-space_optical_communications_over_turbulent_channels [accessed Apr 30, 2015]

Upper Bounds for the Analysis of Trellis Coded Spatial Modulation over Correlated Fading Channels

International audienceTrellis Coded Spatial Modulation (TCSM) is a novel transmission technology for Multiple–Input-Multiple–Output (MIMO) systems, which has been recently proposed to improve the performance of Spatial Modulation (SM) over correlated fading channels. The fundamental principle of TCSM is to use convolutional encoding and Maximum–Likelihood Sequence Estimation (MLSE) decoding to increase the free distance between sequences of spatial constellation points, thus improving, especially over spatially correlated fading channels, the end–to–end system performance. In this paper, we propose tight analytical bounds for performance analysis of TCSM over correlated fading channels. In particular, the contributions of this paper are as follows: i) we propose two asymptotically tight (for high Signal–to–Noise–Ratios, SNRs) upper bounds for the analysis of uncoded SM schemes, which offer a better accuracy than already existing frameworks, ii) we propose a simple Chernoff bound for performance analysis of TCSM, which, although weak, can well capture the diversity order of the system, and iii) we propose an asymptotically tight (for high SNRs) true union bound for the accurate performance prediction of TCSM over correlated fading channels. Analytical frameworks and findings will also be substantiated via Monte Carlo simulations