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A Gradual Method for Channel Non-Reciprocity Calibration in Cell-Free Massive MIMO
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- Authors
- Nam-I Kim, Chang Wahn Yu, Seung-Eun Hong, Jee-Hyeon Na, Byung Chang Chung
- Issue Date
- 2022-11
- Citation
- IEEE Communications Letters, v.26, no.11, pp.2779-2783
- ISSN
- 1089-7798
- Publisher
- IEEE
- Language
- English
- Type
- Journal Article
- Abstract
- This letter proposes a method for gradually calibrating channel non-reciprocity in an ultra-dense cell-free massive multiple-input multiple-output (MIMO) system. Many studies assume perfect channel reciprocity in time division duplex (TDD) systems. However, reciprocity is not valid in actual channels. Therefore, determining the reciprocity-calibrated precoding matrix is important for the performance of the network. In a cell-free massive MIMO system, user equipment (UE) is served by many access nodes (ANs). Since there are many nodes, it is difficult to calibrate the matrix simultaneously. Using the proposed method, the network sequentially calibrates the precoding matrix in order of influence. Thus, the proposed method can obtain a large gain compared to a system without calibration by performing only minimal channel calibration. To show the capacity gain of the proposed method, a simulation was performed considering the overhead required for channel calibration.
- KSP Keywords
- Capacity gain, Channel Reciprocity, Channel calibration, Large gain, Massive MIMO system, Massive multiple-input multiple-output (MIMO) systems, Time division duplexing(TDD), Ultra-dense, User equipment(UE), cell-free, non-reciprocity