Semi-orthogonal pilot design for massive MIMO systems using successive interference cancellation

With the rapidly increasing demand for high speed data transmission and a growing number of terminals in one cell, massive multiple-input multiple-output (MIMO) has been shown promising owing to its high spectrum efficiency. Although massive MIMO can efficiently improve the system performance, usage of orthogonal pilots and growing terminals cause large resource consumption especially when the coherence interval is short. This paper presents a semi-orthogonal pilot design with simultaneous data and pilot transmission. In the proposed technique, we exploit the asymptotic channel orthogonality in massive MIMO systems, with which the mutual interference between data and pilot can be mitigated by successive interference cancellation (SIC). Theoretical analysis and simulation results show that the proposed pilot design can achieve a significant performance improvement with reduced pilot resource consumption compared with the popular orthogonal pilots.