在巨量天線系統下使用部分通道資訊達成最大化最小增益之使用者之混和式波束成型設計

Abstract

巨量天線(Large-Scale Antenna) 系統極有可能成為下一世代的無線通訊架構。隨著天線數量的增加，獲取完整通道資訊(CSIT) 的難度也隨之提高。除此之外，傳統數位波束成型技術(Fully Digital Beamforming)，因受限於每支天線都需要有專屬射頻電路(RF Chain)，而射頻電路的高成本與高功率的損耗使得傳統數位波束成型技術在巨量天下系統下並不切實際。在本論文中，提出了一種在分頻多工下(Frequency Division Duplex)，混和波束成型(Hybrid Beamforming)預編碼的演算法。藉由上行(Uplink) 與下行(Downlink) 通道的互惠性(Reciprocity)，可以有效率地獲得部分的通道資訊。為了避免任何使用者遇到不好的傳輸品質，演算法考慮到公平性的問題。模擬結果顯示了我們所提出的混和波束成型演算法，在比較少的射頻電路下, 其表現可以非常接近傳統數位波速成型。與此同時，對所有使用者也保持了公平的傳輸品質。

Large-scale antenna (LSA) holds a huge potential for the next-generation communication systems. However, the acquisition of full channel state information at transmitter (CSIT) becomes a big challenge when the scale of antenna arrays gets larger. Furthermore, conventional fully digital beamforming (FDB) requires a dedicated radio frequency (RF) chain for each antenna, which leads to high cost and critical power consumption in LSA. In this thesis, a hybrid beamforming (HB) design method in frequency-division duplex (FDD) LSA systems with partial CSIT condition is proposed. By exploiting the FDD channel reciprocity, partial CSIT can be acquired effectively. To avoid any user equipment (UE) experiencing poor quality of service (QoS), the fairness constraint is considered. Simulation results show that the proposed HB design can achieve nearly the same performance compare to that of the optimal FDB and less number of RF chain is needed. Meanwhile, the QoS is maintained for each UE.