在毫米波通信中，波束成形是克服毫米波頻帶中極高路徑損耗的關鍵技術之一。在實際應用中，基站和移動站將根據不同應用的需求分別使用適當的波束成形矢量。藉由使用波束成形，對於落在波束方向上的路徑，可以獲得較大的接收功率，也就是說較大的接收功率會集中在特定的角度和時間範圍內。不同的波束方向圖在每個方向上具有不同的波束成形增益，並導致接收功率的分佈在角度和時域上不同。結果使得延遲擴散和角度擴散不同。在本文中，我們考慮了第三代合作夥伴計劃提出的基於群集的三維通道模型和具有三維增益模式的方向性天線，以獲得更實際的結果。首先。我們展示了方向性天線對波束成形的影響，並將其與使用各向同向性天線的波束成形進行了比較。各個波束的性能以波束洩漏比和增益方差來衡量。接著，我們比較了使用不同碼本方案時的延遲擴散和角度擴散以探討波束洩漏比、增益方差、延遲擴散和角度擴散之間的關係。模擬結果顯示，對於相同的波束寬度，通道特性主要受所用波束的波束洩漏比影響。通過使用具有較高波束洩漏比的波束，可以減少在非視距通道中的延遲擴散和角度擴散。

In millimeter-wave (mmWave) communication, beamforming is one of the key technologies to overcome high path loss in the mmWave frequency band. In practical applications, the base station and the mobile station will use appropriate beamforming vectors respectively according to the requirements of different applications. By using beamforming, a larger received power can be obtained for paths falling in the beam direction, which means that the larger received power is concentrated in a specific angle and time region. Different beam patterns have different beamforming gains in each direction, and cause the distribution of received power to be different in the angle and time domain. As a result, the delay spread and the angle spread are different. In this thesis, we considered the cluster-based 3D channel model proposed by 3rd Generation Partnership Project (3GPP) and the directional antenna with 3D gain pattern to obtain more practical results. We show the effect of directional antennas on beamforming and compare it with beamforming using isotropic antennas. The performance of each beam is measured by the beam to leakage ratio (BLR) and gain variance. Then, we compare the delay spread and angle spread when using different codebook schemes to explore the relationship between BLR, VAR, delay spread and angle spread. The simulation results show that for the same beamwidth, the channel characteristics are mainly affected by the BLR of the beam used. By using beams with higher BLR in non-line-of-sight (NLOS) channel, delay spread and angle spread can be reduced.

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