在毫米波異質性網路下用戶連結覆蓋率與傳輸量之基本關係研究

Abstract

近期使用的毫米波異質性網路，包含數層特高頻(UHF)大型基地台以及一層毫米波小型基地台，已經普遍成為探討基礎的用戶連結狀態、訊號覆蓋率以及平均通道傳輸量的模擬分析架構。我們首先策劃了一個能夠反映不同路徑損耗通道的整體性用戶連結方案，在此前提下的用戶連結狀態到將具有最大效益，並以此對訊號覆蓋率及通道傳輸量進行數學上的推導。在冪律路徑損耗模型的使用下，特高頻層與毫米波層基地台的訊號覆蓋率以及通道傳輸量雙雙受到障礙物遮蔽影響，其特徵可大致分為視線可及(LOS)及非視線可及(NLOS)的通道模型、用戶連結參數以及多重天線傳接的衰減的影響。綜上所述，每一層基地台對於整體網路貢獻的訊號覆蓋率以及通道傳輸量都可以被清楚的表示，接著再以此為基礎進行基地台分布配置最佳化的研究。最後，為了顯示高頻寬毫米波所提供的好處，傳輸能量偵測用戶連結(PAUA)方案呼之欲出。在此方案下，整體的通道傳輸率得到最顯著的改善。

In this thesis, a generalized modeling and analysis framework is proposed to explore the fundamental interactions between user association, coverage probability and ergodic link throughput in multiple tiers of the ultra-high-frequency (UHF) macrocell and a single tier of mmWave small cell BSs. We first propose a generalized user association scheme that can cover many pathloss-based user association schemes and derive the distribution of the largest user association function that facilitates the derivations of the coverage probability and the ergodic link throughput. Using a power-law pathloss model, the coverage probability and the ergodic link throughput are both derived in a very general and compact form that characterizes the line-of-sight (LOS) and non-line-of-sight (NLOS) channel models in the UHF and mmWave bands due to blockage effects, user association parameters, and multiple-input-single-output(MISO) fading impacts. They can be used to study how to deploy BSs in each tier in order to efficiently enhance the coverage and throughput since they explicitly show how the BSs in each tier contribute the overall coverage probability and link throughput. To exploit the advantage of the large bandwidth in the mmWave band, the power-aware user association (PAUA) scheme is proposed. Under this scheme, the ergodic link throughput can be remarkably improved.