3GPP長期演進技術中室內小型基地台之無線電干擾分析與迴避機制設計

Abstract

低成本與寬頻無線接入的特性讓家用基地台在室內環境更顯優勢，然而家用基地台與大型基地台間之干擾問題將嚴重影響服務品質。為了避免採用增加硬體成本的改善方法，本研究針對頻譜配置的演算法進行研究。採用跨層級網路設備協調的機制，來避免不佳的電源控管造成的干擾問題，進而讓有效率的分散式頻譜配置演算法能有效作用，以提供良好的訊號品質。 本研究針對Femtocell之間的共用頻譜分配，並根據各QoS服務類型需求做有效的資源分配。本方法使用集中式資源配置之演算法，並將最終資源配置之裁量權交由Femtocell的管理系統(FMS)，由於其管理Femtocell的群體數量不至於太多，因此不會有壅塞的情況發生。同時，欲套用此機制，硬體方面僅需在FMS端加上足夠的Cache memory紀錄資源之使用狀況，再行實作FMS端的管理及兩者間的溝通協定，Femtocell端不需為因應新機制而變更現有規格，對於供應商而言是可行的升級方案。

Minimizing femtocell interference, maximizing resource efficiency and ensuring quality of service (QoS) are important challenges in the design of protocols for femtocell networks. Techniques of interference avoidance, resource efficiency improvement, and QoS guarantee consist in finding an optimal assignment of physical resource blocks (PRBs). For example, in dense area deployments, only resources that are not occupied by interfering neighbors can be assigned with considerations of employed resources and required service qualities. In this thesis, we address the optimal PRB assignments in orthogonal frequency division multiple access (OFDMA) femtocell networks. Typically, all femtocells operate in the co-channel deployment, and schedule for different connections dynamically. We seek a resource-optimal distribution that maximizes spectral efficiency while ensuring simultaneous femtocell connectivity quality to femtocell management systems, which are constrained to form an interference graph used as an assignment distribution. First, we formulate this problem as an Integer Linear Programming model. Then, we implement a greedy algorithm to solve the allocation problems. Experimental results show that the proposed model provides optimal spectral efficiency values according to the dynamic femtocell loading.