The massive use of transmit and receive antennas with perfect channel state information (CSI) in massive multiple-input multiple-output (mMIMO) systems can lead array power gain increments proportional to the number of antennas. For CSI estimation pilots can be used, but in multi-user scenarios pilot contamination may occur which may compromise estimation, even when are used orthogonal sequences such as Chu sequences. In such conditions improvements achieved by mMIMO systems can be compromised. Therefore, it is important to assure good channel estimation even when pilot contamination exits without sacrificing spectral efficiency and complexity. For that purpose, methods such as a complexity-reduced adaptive semi-blind channel estimator or a decision directed scheme based on a iterative block frequency domain equalizer (IB-DFE) could be used to compensate the pilot contamination impact on channel estimation. Moreover, when the the number of channels involved in communication the first method has comparable performance to second one, for a lower complexity which could. To support this assumption it is also presented a set of performance results comparing both methods.