DEVELOPMENT OF AN IMPROVED PILOT DECONTAMINATION SCHEME USING ORTHOGONAL UPLINK PILOT SEQUENCE BASED ON LARGE SCALE FADING MASSIVE MIMO SYSTEMS

Pilot contamination (PC) is the major challenge in Massive Multiple Input Multiple Output (M-MIMO) systems of work of previous researchers because it reduces the achievement of numerous benefits of the M-MIMO system. In this proposed scheme, users are classified into center cell and edge cell users based on their large-scale fading. The center cell users suffer less or no interference which not the case with the edge cell users. Pilot sequences are assigned to the center cell users, which are shared sequentially with new users after being exhausted. The edge cell users are assigned distinct Orthogonal Variable Spreading Factor (OVSF) and multiplied then by Zadoff Chu Pilot Sequence (ZCPS), thereby creating orthogonality across the cells as well as across the neighboring cells. This process reduces or eliminates interference, resulting in improved performance of the M-MIMO system as evident from both the plots of the results of the work of Ali et al., (2017a) and that of the developed scheme. When the plots of the sum-rate against standard deviation of AoA, number of antennae, cross gain, and number of cells of both schemes are compared, the developed scheme outperformed the existing work with improvements of 6.8%, 11.11%, 12.20%, and 11.90%, respectively.