臺灣大學: 電信工程學研究所謝宏昀張政邦Chang, Cheng-PangCheng-PangChang2013-03-272018-07-052013-03-272018-07-052011http://ntur.lib.ntu.edu.tw//handle/246246/253016　　在由Macrocells和Femtocells組成的二階層無線網路中，Femtocells大量且隨意的佈建常導致使用者遭到鄰近Femtocells一定程度的干擾，進而造成使用者的傳輸品質下降甚至是服務中斷。在本實驗室之前的研究中，我們提出以IEEE 802.16m中的低負載模式（LDM）來實作降低二階層網路下的干擾。藉由交錯的LDM傳輸週期，錯開Femtocells之間的傳輸，使得使用者受到的干擾量可以被大幅的降低。 　　在這個架構下，由於Femtocells的資源會根據其被分配到的LDM傳輸週期而調整，某些Femtocells可能會因為被分配到較少的資源，造成無法滿足底下所有使用者的需求。有鑑於此，在本論文中，我們提出了一種由網路主動觸發的換手機制，藉由主動要求網路中的某些使用者換手到鄰近的基地台，使得網路中所有的使用者都能獲得足夠的資源。首先，我們將這個問題建構成一個最佳化的問題，期望在滿足網路中所有使用者的情況下，最小化被要求換手的使用者個數。接著，在同時考量到服務使用者的基地台和使用者周圍可用的基地台之資源狀況下，我們提出了Best　Candidate和Average　Candidate這兩個方法來降低求解的複雜度並達到趨近最佳解的效能。本論文的研究結果發現，在Macrocells和Femtocells組成的二階層無線網路中，藉由網路主動觸發的換手機制，基地台可以在不犧牲部分使用者的情況下提供所有使用者更好的通訊品質，進而提昇系統整體的服務品質。In the Macro-Femto two-tiered wireless networks, due to the large amounts and random distributed of Femtocells, the interference among users is quite large, which could lead to users'' communication quality drop or even service terminated. In our previous work, an operation in IEEE 802.16m called low-duty operation mode (LDM) is applied to implement interference mitigation for the two-tiered network. By assigning “interlaced” LDM patterns to neighboring Femtocells, the interference among users could be largely reduced. However, because of the resource adjustment on Femtocells according to their assigned LDM patterns, some of the Femtocells might not satisfy all of its subordinate users due to their less assigned resource. Thus, in this thesis, we proposed a network-initiated handover scheme which initiates some of the users in the two-tiered network to handoff to neighboring cells in order to satisfy all the users'' requirements. The problem is first formulated as an optimization problem, and our goal is to minimize the overall handoff user number in the two-tiered network while at the same time satisfying all users'' requirements. Thereafter, two methods, Best Candidate and Average Candidate, which consider every user''s serving and candidate base stations'' situations are proposed in order to approximate the performance of optimal solution while at the same time reducing the complexity of finding solutions. From the results in this thesis, we find out that in Macro-Femto two-tiered wireless network, by applying the network-initiated handover scheme, base stations could create a better communication quality without sacrificing some users'' performance, which leads to an overall increase of system service quality.3504780 bytesapplication/pdfen-US換手資源管理802.16二階層網路handoverresource managementfemtocellthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/253016/1/ntu-100-R97942130-1.pdf