Pilot frequency distribution method for twice clustering and classifying of large-scale MIMO system

Abstract

The invention discloses a pilot frequency distribution method for twice clustering and classifying of a large-scale MIMO (Multiple Input Multiple Output) system. The pilot frequency distribution method specifically comprises the following steps: step 1, L cell base stations respectively calculate large-scale fading factors of all users in a cell where the L cell base stations are located; step 2,the L cell base stations calculate a user primary clustering threshold value, and perform primary clustering classification on all users in the cell according to the user primary clustering thresholdvalue; 3, the L cell base stations calculate secondary clustering thresholds of the users; step 4, the L cell base stations classify all the user categories of the primary clustering edge category inthe cell again according to the secondary clustering threshold of the users; step 5, the L cell base stations sort the secondary clustering center type users; step 6, a pilot frequency set is divided;step 7, the pilot frequency is distributed. The method has the beneficial effects that the quality of service (Quality of Service. QoS) of edge group users is improved on the premise of reducing theperformance loss of central group users; and pilot pollution is effectively suppressed.

Description

technical field [0001] The invention relates to the technical field, in particular to a pilot allocation method for two clustering divisions of a massive MIMO system. Background technique [0002] Massive MIMO (multiple-input multiple-output, MIMO) technology configures a large-scale antenna array on the base station side, and utilizes spatial degrees of freedom to improve the spectrum efficiency and energy efficiency of the system. One of the keys to take advantage of the massive MIMO technology is that the base station must obtain accurate channel state information (CSI). [0003] In a multi-cell multi-user massive MIMO system, due to the limited channel coherence time, pilot multiplexing between cells is inevitable, and the resulting pilot contamination (PC) seriously affects the accuracy of channel estimation, so it is necessary to allocate pilots reasonably It is the key to suppress pilot pollution. [0004] In the prior art, there are many documents mentioning relate...

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Problems solved by technology

[0010] Document 8 (Zhu Xudong, Wang Zhaocheng, Qian Chen, et al.Soft Pilot Reuse and Multicell Block Diagonalization Precoding for Massive MIMO Systems[J], IEEE Transactions on Vehicular Technology, 2016, 65(5):3285-3298.) proposed a Based on the pilot allocation algorithm of soft pilot reuse (SPR), the users in the cell are divided into central group users and edge group users, and different pilot allocation strategies are adopted for different users, which can improve the edge of poor channel quality. The channel estimation accuracy of the group users, but this strategy uses the method of randomly multiplexing pilots for the central group users, which will inevitably cause performance loss, and the pilot overhead will increase with the number of edge users.

[0011] Document 9 (Chang Wenson, Chan Hanwei, Hua Yunkuei. Weighted Graph Coloring Based Soft Pilot Reuse for TDD Massive MIMO Systems[J], IEEE Transactions on Vehicular Technology, 2018, 67(7): 6272-6285.) proposed a joint soft pilot Frequency multiplexing and graph coloring pilot allocation algorithm, but requires inter-cell cooperation and high information exchange overhead

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