• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.274-279
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• 2021

Since conventional massive antenna systems require too many RF chains, they have disadvantages of high implementation cost and complexity. To overcome this problem, hybrid precoding schemes have been proposed. But, they are still of high implementation cost and complexity because RF chains are connected to all antenna elements. In this paper, we consider massive MIMO systems with overlapped sub-array (OSA) structure and then, propose a hybrid precoding scheme. In the overlapped subarray structure, RF analog precoding matrix has a sparse structure where many elements of RF analog precoding matrix are zeros. Using this sparse property, we propose a GTP-based precoder design method for RF and baseband digital precoding. Through simulation, we show that the proposed scheme has more than 85% of the spectral efficiency of the fully-connected structure while having 20~30% of complexity of it.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.49-55
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• 2022

In the next generation mobile communication systems, hybrid massive multiple-input multiple output (MIMO) can be used to highly improve an achievable rate without increasing the number of RF chains. Recently, successive-interference-cancellation (SIC) based hybrid precoder design scheme was proposed to reduce the complexity. However, since this scheme uses simple diagonal matrix for baseband precoding, it cannot solve an interference problem between the transmitted streams. Also, there is a limitation for improving the data rate because of the use of one phase shifter for analog precoding. To solve these problems, in this paper we propose a digital precoding based on the SVD of the effective channel and an analog precoding using two phase shifters. Through simulation, we show that the proposed scheme has better achievable rate and SINR performances than the conventional one.