應用於大規模多輸入多輸出系統在數位及混和式架構下基於波束成型之最佳空間預編碼

Optimal Beamforming-Based Spatial Precoding under Digital and Hybrid Structures for Massive MIMO Systems

孫偉恩(Wei-En Sun)

指導教授 ： 李枝宏

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802313

摘要

為了降低在frequency-division duplex (FDD)大規模多輸入多輸出(massive multiple-input multiple-output ,massive MIMO)系統之downlink training 以及channel state information(CSI)回傳的負擔(overhead)，之前的學者提出了beamforming-based spatial precoding (BBSP)方法，本實驗室先前提出了一種方法修正BBSP，稱為beamforming selection spatial precoding (BSSP)，運用了粒子最佳化演算法(PSO)及合作式共同粒子群最佳化演算法( CCPSO2)去調整precoding matrix之大小(amplitude)及相位(phase)參數，如此便可以減少使用者間的干擾，不但保留了原本BBSP擁有較低的downlink training 以及CSI回傳的負擔(overhead)的優點，比起原本的BBSP可以達到更好的位元錯誤率(BER)。我們發現在考慮空間相關性以及交互耦合現象的情況下，天線所擺放的位置也會影響BSSP的位元錯誤率(BER)，我們將天線位置的參數與precoding matrix之大小(amplitude)及相位(phase)參數放入合作式共同粒子群最佳化演算法( CCPSO2)做調整，會發現比起固定天線位置為Uniform Linear Array(ULA)或是Uniform Circular Array(UCA)有更低的位元錯誤率(BER)。我們發現BSSP可以運用在混合式波束成型(Hybrid beamforming)系統，以降低毫米波多輸入多輸出系統(mm-wave multiple-input multiple-output)之硬體成本及功率消耗，我們將Analog precoder 當作CCPSO2要調整的參數，用MMSE法則計算出Baseband precoder，我們稱此方法為Hybrid MMSE CCPSO-BSSP ，在傳輸資料時我們加入了Quasi-orthogonal Space–time block code(QOSTBC)，並針對在多用戶的情況下改良了傳統QOSTBC在Single user情況下的解碼方式，並在大規模多輸入多輸出(massive multiple-input multiple-output ,massive MIMO)系統與不同的通道環境下還有交互耦合現象(Mutual Coupling) 的影響情況下模擬結果發現Hybrid MMSE CCPSO-BSSP與加入QOSTBC的Hybrid MMSE CCPSO-BSSP-QOSTBC都可以比以前所提出的CCPSO-BSSP有更佳的系統效能。

關鍵字

大規模多輸入多輸出系統 ； 空間預編碼 ； 波束成型 ； 空間相關性 ； 交互耦合 ； 粒子群最佳化演算法

並列摘要

To reduce the overhead of downlink training and channel state information (CSI) in frequency-division duplex (FDD) massive multiple-input multiple-output (massive MIMO) systems, previous scholars proposed a beamforming-based spatial precoding (BBSP) method. Our laboratory previously proposed a beamforming selection spatial precoding (BSSP) method to modify BBSP, using a particle swarm optimization algorithm (PSO) and cooperatively coevolving particle swarm optimization algorithm (CCPSO2) to adjust the amplitude and phase parameters of the beamforming coefficients, and hence reduce the interference between users. It not only retains the original BBSP with lower downlink training and CSI feedback overhead, but also achieves better bit error rate (BER) performance than the original BBSP. In the presence of the spatial correlation(SC) and the mutual coupling(MC) effects, the antennas positions affect the bit error rate (BER) of the BSSP. We have found that adjusting the antenna positions, the amplitude and phase of the precoding matrix can simultaneously achieve lower bit error rate (BER) than that of using Uniform Linear Array (ULA) or Uniform Circular Array (UCA). We also found that the BSSP can be used in hybrid beamforming systems to reduce the hardware cost and power consumption for mm-wave MIMO systems. We used CCPSO to adjust Analog precoder, and used the MMSE criterion to calculate the Baseband precoder. We call this method Hybrid MMSE CCPSO-BSSP. We use the Quasi-orthogonal Space-time block code (QOSTBC) to transmit data in BSSP. Under the circumstances, the decoding method of the traditional QOSTBC in the case of Single user was improved. From the simulation results, we observe that Hybrid MMSE CCPSO-BSSP and Hybrid MMSE CCPSO-BSSP-QOSTBC outperform the existing methods for in Massive MIMO systems under several channel environments with the SC and MC effects.

並列關鍵字

massive multiple-input multiple-output systems ； spatial precoding ； beamforming ； spatial correlation ； mutual coupling ； particle swarm optimization algorithm

參考文獻

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