異質網路中利用頻率重複使用與功率控制 技術達成流量卸載的設計

Abstract

異質網路是目前廣為應用的網路技術，其利用空間重用的特點來增加系統的頻譜效率。然而這個優勢卻因為大型基地台與小型基地台的傳輸功率差距受到限制。此外異質網路也帶來了關於頻譜使用效率和接收信號強度之間的權衡問題。在近來的相關研究中，有三種可增進網路效能的基礎技術，分別是用戶連結選擇、頻率或時間資源的分配、以及傳輸功率控制。我們發現大部分現有的研究中缺少同時針對以上三種要素和異質網路的特性做出完整考量的設計 為了解決這個問題，我們提出了一種新的機制，其包含1) 在異質網路中的部分頻率重用，讓頻譜使用效率和降低干擾之間取得一個較好的平衡；2) 一個基地台功率控制的遞迴演算法，其依據系統目前的效能調整傳輸功率，在不犧牲接收訊號強度的條件下實現流量卸載的功能；3)一個基地台的頻率資源分配演算法，其會根據負載和通道狀況分配給用戶適當的頻帶。在網路模擬的結果中顯示出我們提出的是一個有效率的流量卸載機制，其無論在網路的產出效能和公平性都有優良的表現。

Heterogeneous network (HetNet) is a promising technique to improve the system spectral efficiency by exploiting the benefit of spatial reuse. However, the benefit of HetNet is limited by the asymmetry of transmit power between macro BSs and small cells. Moreover, it leads to a natural tradeoff between SINR and spectral efficiency. In recent studies, there are three basic mechanisms to improve the network performance, user association, resource allocation, and transmit power control. On the other hand, there are rare studies take all of these three elements into accounts in HetNet. To tackle the problem, we propose a novel mechanism which is combined with 1) a partial frequency reuse (PFR) scheme in HetNet, which achieve a balance between spectral efficiency and interference mitigation, 2) a iterative transmit power control algorism (TXPC) for macro BSs, which realize the traffic offloading from macro cell to pico cell without sacrificing the SINR performance, 3) a load-aware frequency allocation algorithm (LAA), which allocate proper frequency considering the load and channel condition. The simulation results show that our algorithm is indeed an efficient mechanism which has better network performance in average throughput and fairness.