| Summary: | 碩士 === 國立成功大學 === 電腦與通信工程研究所 === 104 === By deploying an extremely large number of antennas at base station (BS), the massive multiple-input multiple-output (MIMO) technique can provide sufficient degrees of freedom such that the intra- and inter-cell interference can be thoroughly eliminated. However, this ideal merit is seriously restrained by the well-known pilot contamination problem caused by using the non-orthogonal pilot sequences. Traditionally, the time-shifted pilot (TSP) technique was proposed to partition cells into several groups; and only the cells within the same group are allowed to transmit pilots simultaneously. Unfortunately, using the TSP scheme restricts the number of accommodating users.
In this paper, we aim to find a better tradeoff between the orthogonality of pilots and the number of users by proposing the partial-time-shifted pilot (PTSP) scheme. Specifically, the cells belonging to different groups are allowed to transmit pilot signals using the overlapped symbol intervals. To achieve this, the pilot symbols rather than the pilot sequences are adopted in this paper. Although it can result in the stronger IGI, the larger number of accommodating users can contribute to higher sum rates. Moreover, a well-designed downlink transmission power can further raise the performance enhancement. The simulation results demonstrate the significant sum rate improvements for the downlink and uplink cases, respectively. It is believed that the contributions of this paper can provide helpful information for developing a massive MIMO system.
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