Modified HTRCI with Variable Pulse Generation for Pilot De-contamination

Massive Multiple-Input-Multiple-Output (MIMO) systems, where the base station (BS) is equipped with hundred antennas, is expected to be one of the key technologies for the next generation wireless systems. Pilot contamination is one of performance degradation factors for massive MIMO. This paper aims to eliminate this pilot contamination impact. High time resolution carrier interferometry (HTRCI) was previously proposed which can perform highly accurate channel estimation with reducing the number of pilot signals. The original HTRCI generated the impulses in 1/4 equal interval. With regarding the current OFDM system design, more fine and variable impulse allocation is available, e.g. the guard interval (GI) length of Long-Term-Evolution-Advanced (LTE-A) is 1/8 or 1/16 of the OFDM symbol duration. This paper proposes the modified HTRCI with variable pulse generation at 1/8 interval which can estimate channel state information (CSI) of the 4 access per received antenna. This paper expands the concept of HTRCI to estimate more channels and these CSIs can be separated by time-domain signal processing in the same manner. It is applied to the pilot de-contamination on downlink multi-cell MIMO transmission. Computer simulation results confirm that the BER performance can be improved as compared with the conventional method.