Volume 33, Issue 1, July 2016

Implementation scenarios for an adaptable LTE turbo decoder based on BLER [Full Text]

C. Chaikalis

Abstract—The idea of an adaptable SOVA/log-MAP turbo decoder has been well addressed and discussed in published literature. This work shows that such a decoder can be implemented in LTE standard for AWGN and uncorrelated Rayleigh fading channels. For physical shared channel (uplink and downlink) we use pipeline turbo decoder architecture and we consider BLER or FER performance in our analysis. We examine two data rates and for each one we consider the nine possible QCIs using five frame lengths. Considering BLER and delay limitations for each QCI, log-MAP is proposed for small frames for all data rates, QCIs and AWGN channel. SOVA represents the proposed choice for larger frame lengths for both AWGN and uncorrelated Rayleigh fading channels and for low data rates. Comparison with already published results considering BER performance shows similar findings for uncorrelated Rayleigh fading channel, whereas for AWGN channel there are different findings only for log-MAP. 

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Optimal Pilot Matrix Design for Training- Based Channel Estimation in MIMO Communications [Full Text]

Y. EL Mouden, N. Abdulaziz

Abstract—This paper considers pilot-based (or training-based) channel matrix estimation in downlink multiuser multiple input multiple output (MIMO) wireless communication systems under Rician fading. The Bayesian approach is used to analyse and derive closed-form mathematical expressions for the minimum mean square estimator (MMSE) and the mean square error (MSE) in estimating the channel state information (CSI) where the long-term channel statistics are known a priori. It is shown how the pilot matrix can be designed to maximize the estimation performance. MATLAB simulation examples are used to evaluate the performance of the MMSE channel estimator for different training sequences and system statistics and to show how both the optimal length of the training sequence (number of columns of the pilot matrix) and the channel estimation error decreases with the spatial correlation.