|Abstract: ||5G通道特性的了解是設計5G通訊系統的重要依據。為了滿足5G之高傳輸率及高系統容量的需求，使用高頻段以取得數百MHz之頻寬，勢不可免。而高頻段之電波傳播特性與現行2-3GHz低頻段有顯著的不同。因此，在5G系統設計之初，實有必要針對5G高頻段通道進行完整的分析。分析5G高頻段通道的方法有許多種，利用射線追蹤(ray-tracing)技術準確預測電波傳播特性之模擬平台，是5G網路佈建及5G產品測試不可或缺之工具，只要模擬環境建立夠精細，射線追蹤技術的準確性就無庸置疑。本論文建立了都市、校園及室內開放式辦公室之射線追蹤系統模擬平台，其中室內開放式辦公室結合工研院資通所以及本校電機工程研究所之毫米波通道量測團隊，以量測及模擬結果，從功率延遲剖面圖(power delay profile)來分析平台之準確性。由於高頻段電波繞射(diffraction)能力微弱、易被遮障(blockage)，一旦被物件遮障，鏈路預算(link budget)將下降20至30分貝，抗遮障效應之技術是未來5G通訊系統發展的重點。本論文第二部份基於上述之射線追蹤模擬平台及3GPP New Radio (NR)應用場景及天線架構，提出波束候選之抗遮障技術，包括： I. 單一傳送波束、多接收波束技術II. 同基站下多傳送波束、多接收波束技術III. 不同基站下多傳送波束、多接收波束技術模擬結果顯示，使用者受到遮障後，有20%的使用者會通訊中斷(outage)。方法一改善了2%的outage機率，此方法的好處是使用者切換接收波束不須回報至基站，波束管理(beam management)複雜度最低；方法二比起方法一改善outage的比例約8%，此方法須付出的代價是，使用者須回報基站更換傳送波束，此動作會造成波束管理上較高之複雜度；方法三之改善幅度最大，outage機率下降至7%，因不同基站之傳送波束意味著空間上相隔更開，抗遮障之能力越好，但須基站之間的合作，以及更高的波束管理複雜度。|
Understanding of 5G channel characteristics is a must prior to design 5G communication systems. To meet the explosive growth of mobile traffic demand, the exploitation of large bandwidth in the millimeter wave (mmWave) band is inevitable. However, there are fundamental differences between mmWave and low-frequency channel characteristics. Therefore, it is necessary to analyze 5G channel characteristics in high-frequency band at the beginning of designing 5G systems.There are several ways to characterize the 5G channel in mmWave band, for example, channel measurements and ray-tracing techniques. In particular, site-specific ray-tracing simulation platform is preferable due to its accuracy. The more detailed the environment construction is, the more accurate the simulation result will be. In this work, we construct three ray-tracing based simulation platforms for urban, campus and indoor open office, respectively. Especially, we collaborate with ITRI/ICL and department of electrical engineering/CCU in verifying the site-specific simulation platform.With a small wavelength, propagation rays in the mmWave band are sensitive to blockage by obstacles (e.g., humans and furniture). Blockage by a human penalizes the link budget by 20-30 dB. Consequently, the anti-blockage technique will play a vital role in the design of 5G communication systems.In this work, in addition to the ray-tracing based simulation platforms mentioned above, we propose three beam selection methods for anti-blockage, including I. Fixed one transmit beam, multiple receive beamsII. Multiple transmit beams, multiple receive beams under same base stationIII. Multiple transmit beams, multiple receive beams under different base stationsAs the numerical results show, about 20% of users are in outage without any remedy after being blocked. The first method improves outage probability by 2%, and its advantage is the lowest complexity because switching candidate received beams doesn’t need to inform base station. Method 2 improves outage probability by 8% but it results higher complexity because the switching of transmit beams needs to inform base station. The method 3 has best performance with outage probability decreasing of 7% due to wider angular separation of beam-pair-links (BPLs). However, it also needs inter-base-station cooperation to be operable.