在長程演進技術升級版(Long Term Evolution Advanced ; LTE-A)中，異質網路(Heterogeneous Networks)為解決在訊號範圍死角或人口稠密的地方通訊不佳的問題，可佈建不同發射功率的基地台，利用成本較低的小型基地台增強通訊範圍不佳的環境；且由於無線頻寬資源有限，如何有效分配頻段給不同等級的基地台，是一相當重要的議題。
許多文獻已針對此問題進行探討，研究方法可概分為分割、共享及混合配置三種。其中分割式頻段限制各基地台可用頻寬會降低資源利用的彈性，而共享及混合配置會造成基地台間的干擾問題；本論文針對毫微微型基地台(Femtocell)，首先分析這三種頻寬配置之優劣，在考慮到各基地台服務範圍內用戶移動的情形，提出適應性頻寬調整之資源分配機制(Adaptive Frequency Allocation ; AFA)，根據前次資源分配情形做為調整的參考因素，目的是期望當用戶從大型基地台移動至毫微微型基地台時，能藉由頻段分配的調整，改善頻寬資源的使用率，有效提升系統傳輸量及減少封包丟棄率。
其模擬結果顯示，本論文提出的適應性頻段調整方法在系統負荷輕載時能有效的改善系統整體傳輸量，同時大幅改善封包丟棄率，且隨著用戶改變越多，提升情況越明顯，儘管系統負荷滿載時改善幅度較不明顯，然而相較於分割式及共享式配置，系統仍明顯有較好的傳輸量。

In Long Term Evolution Advanced, the low-power base stations can be deployed to eliminate coverage holes in macro-only system and improve capacity in hot spots which is called Heterogeneous Networks. And because of the limited resources in network, it’s a very important issue on how to effectively allocate spectrum to different levels of the base station especially in heterogeneous networks.
Many studies have focused on this issue. Most of the research methods can be divided into three kinds, which are partitioned spectrum usage, shared spectrum usage and hybrid spectrum usage. Partitioned spectrum usage which limited the available bandwidth for each base station will reduce the flexibility of frequency reuse. On the other hand, shared spectrum usage and hybrid spectrum usage may cause interference between base stations when using the same spectrum. Firstly, we analyze this three spectrum allocation of the pros and cons, and consider the scenario of user movement. We proposed resource allocation scheme of Adaptive Frequency Allocation (AFA) and establish the adjustment of spectrum allocation according to the distribution of resource allocation in every base station. And expecting when more users move to femto base station, we can adaptively decide the best scheme of allocation for next time to improve utilization of bandwidth resource, increase system throughput and improve drop ratio.
The simulation result shows that AFA can effectively improve overall system throughput and drop ratio while the system traffic is low. And as more users move to different base station, the more improvement can achieve in throughput. However, when the system in high traffic loads, the improvement by AFA seems not obvious. But compared to other schemes, AFA still can get better throughput.

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