Efficient pilot reuse algorithms for massive MIMO cellular system

Summary Pilot contamination has come up as one of the major limitations of massive multiple‐input multiple‐output. In the recent past, the pilot contamination resulted by the pilot reuse in inter‐cell system has been successfully handled. In this paper, three efficient algorithms have been proposed to reduce the pilot contamination in intra‐cell system. These schemes emphasize on assigning the available pilots to the users based upon their channel qualities by considering the interfering degree of the various pilot sequences. The first proposed algorithm is based on water filling approach, which attains the system throughput very close to that of brute‐force exhaustive search algorithm (ESA) and performs the best among the three proposed algorithms in terms of system throughput. The second algorithm is designed for achieving better user fairness (by assigning less interfering pilots to the poor channel conditioned users). The third algorithm improves the system throughput as compared to the second algorithm without losing much in terms of user fairness. Furthermore, the computational complexity incurred by all the proposed algorithms is much less than that of ESA. Throughput maximization algorithm (TMA) achieves system throughput higher than both smart pilot scheme (SPS) and greedy scheme (GS), attains complexity higher than SPS but much less than GS, and achieves the least minimum uplink SINR among all schemes. User fairness algorithm (UFA) achieves the highest minimum uplink SINR among all schemes and attains the least throughput among proposed schemes. Greedy user fairness algorithm (G‐UFA) achieves system throughput better than UFA but less than TMA and attains better minimum uplink SINR than TMA.