5G蜂巢網路下針對協調多點傳輸之毫米波回程鏈路流量最小化

Abstract

協同式多點傳輸(Coordinated multipoint; CoMP)被認為是5G蜂巢式網路中一個有潛力且重要的技術。此技術可以用來減少基地台之間的干擾並改善基地台邊緣用戶可接收到的資料率。聯合傳輸(joint transmission)是其在下行傳輸的主要分類之一，透過多個基地台在同一時間及同一頻率上傳輸相同資料給使用者，來提高使用者所接收到的訊號強度。然而，這些協作的基地台必須共享相同的使用者資料，這造成了骨幹網路嚴重的負擔。因此，許多研究開始探討在基地台加入儲存(cache)的功能，以減少骨幹網路的資料流量。在本文中，我們考慮一個新穎的小型基地台回程架構(small cell mmWave mesh backhaul)，每個基地台皆配有一個cache，彼此之間藉由毫米波鏈結形成網格狀拓墣。如此一來，基地台可以從鄰居取得使用者要求的檔案，而不必透過遙遠的內容伺服器。但我們發現在這樣的架構下，如果無法針對聯合傳輸做出適當的基地台叢集選擇，將會導致不必要的無線資源消耗。為了解決這個問題，我們提出一個基於動態規劃的演算法，目的是在有限的資源和滿足使用者需求的前提下，最小化骨幹網路的資源消耗量。最後，我們進行一系列的模擬，結果證實提出的方法能有效地減少無線資源消耗量。

Coordinated multipoint joint trasmission (CoMP JT) is an attractive technique used to increase cell-edge user throughput. However, it will cause a huge burden on network backhual because the same user data must distribute to multiple base stations of the JT cluster. Thus, many studies have explored how to reduce backhual data traffic by means of caching user data at the base stations. In this paper, we consider a cache-enabled small cell mesh backhaul in millimeter wave band, which is a suggested backhaul solution for small cell deployment. User data can be directly received from neighboring base station through mmWave links without having to obtain from the original content server. Under this novel system architecture, we observe that an inappropriate clustering selection will result in unnecessary backhaul bandwidth consumption. Therefore, we study the joint transmission clustering problem and propose a two-stage algorithm based on dynamic programming approach. The objective is to minimize total backhaul cost while satisfy the data rate requirement of each user under limited radio resource units. Finally, a serious of evaluations are conducted, the simulation results show that compared to the baselines, our proposed algorithm can significantly reduce more backhaul bandwidth consumption.