在這個資訊爆炸的時代，智慧型的個人行動裝置也愈來愈普及。隨著這些裝置硬體設備的提升，普通的撥打電話、收發簡訊、瀏覽網頁已無法滿足需求。下一代行動通訊網路4G便朝著高傳輸率、低延遲及無縫換手的目標持續改進。雖然在台灣LTE-Advance還尚未啟動，但有許多相關的研究持續在進行。如:異質網路(Heterogeneous Network, HetNet)、載波聚合(Carrier Aggregation, CA)、協調型多點傳輸(Coordinated MultiPoint, CoMP)等等。 本篇論文著重在異質網路換手的議題上，異質網路為傳統的基地台覆蓋範圍內，再加入一些低功率的小型基地台，如何有效地增加整體使用者的傳輸量，並不會對傳統基地台產生顯著的干擾。而3GPP提出了Cell Range Eepansion及Almost Blank Subframe兩種機制來解決這個問題，本篇進一步加入了動態調整使用者設備換手參數的機制，TTT(Time-to-trigger)、HOM(Handover Margin)以及使用了動態調整CRE的機制，以達到更好的傳輸量，並降低斷線(Radio Link Failure)的發生率。 ;In the age of information explosion, intelligent personal mobile devices are also increasingly popular. With hardware of these devices upgrading, traditional dial phone, sending and receiving text messages, and browsing the web have been unable to fit demand. The next generation 4G mobile network will have high transmission rate, low latency and seamless handover that we should be improved toward these goals. For the LTE-Advanced system, there are many relating researches developed step by step. For example, there are many issues such as heterogeneous networks, Carrier Aggregation, Coordinated Multipoint and so on to study. This thesis focuses on the handover issues in heterogrneous networks. Heterogeneous networks mean the environment that put number of low-power eNodeBs under the traditional eNodeB coverage. Therefore, how to effectively increase overall performance of user traffic, and not to generate significant interference to traditional eNodeB are important issues for study. The 3GPP proposed two mechanisms, CRE and ABSF to solving these problems, and this thesis further deliver a dynamic handover parameter mechanism and a dynamic CRE in the system, to achieve much better throughput and lower probability of cutoff (Radio Link Failure).
