With the rapidly increasing demand for high-speed data transmission and a growing number of terminals, massive\nmultiple-input multiple-output (MIMO) has been shown promising to meet the challenges owing to its high\nspectrum efficiency. Although massive MIMO can efficiently improve the system performance, usage of orthogonal\npilots and growing terminals causes large resource consumption especially when the coherence interval is short. This\npaper proposes a semi-orthogonal pilot design with simultaneous data and pilot transmission. In the proposed\ntechnique, we exploit the asymptotic channel orthogonality in massive MIMO systems, with which a successive\ninterference cancellation (SIC)-based channel estimation is applied to mitigate the mutual interference between data\nand pilot. We derived the theoretical expressions of the achievable rates in massive MIMO systems with our proposed\npilot design. Further discussion on performance verifies the superiority of our proposed pilot design for high or low\nsignal-to-noise-ratios (SNRs) with any coherence interval length. And simulation results show that the proposed pilot\ndesign can achieve a significant performance improvement with reduced pilot resource consumption compared with\nthe conventional orthogonal pilots.
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