Survey Paper on Massive MIMO System based on Beamforming Technology for mmWave Communication

Multipath propagation, mobility of transmitter, receiver and local scattering cause the signal to spread in frequency, time and angle, resulting in ISI in the received signal. Possible potential gain in spectral efficiency is challenged by the receiver’s ability to accurately detect the symbol in the presence of ISI. Even though OFDM mitigates the problem of time dispersion, still it is necessary to effectively remove the amplitude/phase shift caused by channel and to solve this problem, channel estimation based equalization in the receiver, beam forming (BF) in the transmitter and relay in channel can be invoked. Among the various equalization methods for OFDM and Massive MIMO, minimum mean square error (MMSE) is considered to be a good solution for data recovery in spite of its complexity. MMSE can effectively utilize the diversity of the frequency selective channel and reduce the ISI. The MMSE equalization alone is not an efficient way of reduction of ISI, as the equalization is not carried out with the knowledge of channel impairments. To strengthen the effect of equalization for reducing ISI, channel estimation is used to estimate the amplitude/phase shift caused by the wireless channel impairments.