由於兩層macro/femto異質網路下不同基地台的特性會導致基地台間負載的不平衡，而此種情形將會嚴重地影響異質網路的效能，如何設計理想的負載平衡策略是異質網路中的關鍵議題。因此我們需要一個有效的模型來評估這些負載平衡策略的效能。此篇論文使用隨機幾何的方式以求能夠更精準地模擬各層基地台不規則的分佈情形，並使用自我配置門檻值且不透過後端網路溝通的基本負載平衡策略。此篇論文提出兩個新的效能指標，switch probability和isolated probability來分析所使用之基本負載平衡策略。最後我們使用了OpencellID網站所提供的資料進行模擬，並證實了此數學模型在兩層異質網路的成效。

The diverse characteristics of base stations (BSs) in two-tier macro/femto heterogeneous cellular networks (HCN) might lead unbalanced loading among them, which significantly affects the performance of HCN. How to design a suitable load balancing strategy is a critical issue and obviously we need an efficient model to evaluate the performance of proposed model. To precisely model the behaviors of BSs in each tier deployed in irregular fashion, this thesis adopts stochastic geometry. A self-configured threshold-based strategy without communication overheads among BSs in each tier is proposed as the baseline load balancing strategy. Two novel performance metrics, switch probability and isolated probability, are proposed to evaluate the performance of the threshold-based strategy. We also conduct simulation experiments according to data from OpenCellID web site to prove the effectiveness of the proposed mathematical models in the realistic two-tier HCNs.

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