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Through simulation analysis, the influence of feedback overhead on system throughput is compared, and the effects of traditional DFT precoding methods in 2D and 3D environments and improved 3D precoding schemes on system BER and throughput are compared. An improved 3D precoding scheme based on horizontal emission angle and vertical down-tilt is proposed. According to the quantization error and statistical characteristics of the random distribution of the system, the influence of feedback overhead and base station density on system performance is analyzed using stochastic geometry. This paper proposes a novel codebook design for 3D based MIMO system in heterogeneous network scenarios. Therefore, in FDD massive MU-MIMO systems, codebook-based Multi-user precoding scheme, in which codebook design and multi-user scheduling strategy, are particularly important. In an actual system, the feedback link bandwidth is limited. In a Frequency Division Duplex (FDD) system, CSI acquisition relies on a feedback link. For Time Division Duplexing (TDD) systems, CSI can be obtained through the reciprocity of uplink and downlink channels, but susceptible to pilot contamination.
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However, to make full use of the role of precoding, the transmitter must obtain enough channel state information (CSI). As a key technology of the MU-MIMO system, precoding can effectively suppress multi-user interference and improve the Signal-to-Noise Ratio (SNR). The combination of Massive Multi-user MIMO (MU-MIMO) systems can further utilize spatial freedom to significantly increase system throughput and spectrum efficiency. Compared with the existing 4G technologies, it can significantly improve the spectrum efficiency and energy efficiency of the communication system and has become a research hotspot at home and abroad. Massive MIMO technology is one of the candidate key technologies for 5G. Therefore, academia and industry have successfully conducted research on 5G mobile communication. In recent years, with the widespread use of smartphones such as mobile phones and tablets, the volume of mobile data services has exploded, and existing wireless communication systems can no longer meet such huge business demands. Three Dimensional MIMO (3D-MIMO) is a type of Massive MIMO Technology which has the ability to move the beam horizontally as well as vertically. Compared with the precoding scheme based on 2D and 3D discrete Fourier transform (DFT) codebooks, this scheme greatly reduces the system’s BER, improves the system’s throughput, and optimizes system performance. The results show that the feedback overhead and the micro base station density affect the system throughput and even affect the bit error rate (BER) of the 3D precoding scheme. Based on the deployment of a uniform planar array (UPA) at the base station, a 3D-MIMO multiuser codebook design scheme based on horizontal transmission angle and the vertical down-tilt angle is proposed, and the codebook design scheme is simulated and analyzed. To solve this problem, in the frequency-division duplex (FDD) 3D-MIMO Heterogeneous network system, the influence of feedback overhead on system performance under limited feedback mechanism is studied using random geometry. The 2D precoding technology can only adjust the beam in a horizontal direction through data processing, which will cause serious problems for multiuser systems, especially at the edge of the base station it will cause serious inter-cell interference.