Here, the authors propose a robust blind digital modulation classification (BDMC) algorithm for space time block coding (STBC)‐based MIMO‐OFDM system in the presence of carrier frequency offset (CFO) and channel estimation errors. Previous papers published on the topic of modulation identification were limited to single‐carrier systems operating over frequency‐flat channels. The problem of joint channel and CFO estimation in conjunction with blind digital modulation classification for STBC‐OFDM in frequency selective channel and in the presence of the impulsive noise has not been addressed before to the best of their knowledge. To cope with performance degradation of BDMC due to CFO and channels errors, they propose joint semi‐blind CFO and channels estimation methods. Higher order statistics (HOS), used for feature extraction, are combined with pattern recognition methods to solve the modulation identification problem. The main contribution of their work is the development of estimators, the study of their impacts on the blind classification capability, and the use of simulations to demonstrate the superior performance of the proposed algorithms.

This paper introduces new blind time domain equalization (TEQ) techniques for downlink multicarrier code division multiple access (MC-CDMA) systems. This equalization exploits the guard interval (GI) redundancy together with the excess codes (EC) to restore the structural properties of MC-CDMA signal destroyed by multipath fading channels. Indeed, since in CDMA based wireless systems, the number of users per cell is significantly less than the spreading factor, a base station can set apart a subset of the codes, the excess codes that will not be used for spreading. It is shown that the joint use of the EC and GI redundancy improves significantly the equalization performance compared to the GI only or EC only cases. A second contribution consists in exploiting the previous information together with the one given by a pilot sequence in a semi blind scheme to further improve the performance. Finally, we propose a new adaptive algorithm for the estimation and tracking of the equalizer that has a faster convergence rate compared to existing algorithms of similar complexity order. Simulation based performance evaluations are given at the end of this paper to assess the effectiveness of the proposed methods in MC-CDMA.