隨著近年用戶端設備數量與其無線網路需求量急遽增加，未來在基地台的佈建上將會傾向密集建設低傳輸率的小基地台，然而低傳輸率的小基地台可提供的覆蓋範圍遠小於大基地台所提供的覆蓋範圍，這樣的佈建方式將會導致高速移動的使用者在移動過程中換手次數急遽增加，以及浪費大量的時間在解決網路連線問題。因此我們提出了在控制面和用戶面分離之異質性網路下，藉由架設於車廂上之移動式中繼站，於高速鐵路上之位置輔助換手程序。在控制面和用戶面分離式網路架構下，大基地台可清楚地掌握其覆蓋範圍下小基地台之位置訊息，並管理其連線狀況，進而指派合適的基地台給用戶端。由於高速鐵路有移動路徑固定的特性，因此我們可以準確的預測即將經過的基地台並且即時地完成換手程序。我們將大基地台的覆蓋範圍區分為中心區及邊界區域，並藉由期演進技術所提供的使用者定位方法，判斷使用者即時的所在區域，位於中心區域時優先換手連線至同個大基地台訊號品質較佳的扇區，若位於邊界區域則優先換手至由大基地台透過位置訊息所選定的小基地台，為了更即時換手至大基地台所選定的目標基地台，位置輔助換手程序將不計算事件觸發時間，直接進入換手準備階段。
我們透過系統層級模擬器來模擬實際連線情況，並利用使用者接收資料的吞吐量及連線需花費的時間，評斷位置輔助換手程序，是否有效改善使用者在傳統長期演進技術網路架構下標準換手程序所造成的問題。

Recently, network densification is considered an important solution to the unrelentingly increased of mobile users and their traffic demands. However, User Equipment (UE) in High Speed Railway (HSR) suffer from frequently handovers that cause dramatical network overhead since the coverage region of small Base Stations (BSs) are far less than that of macro BSs. We propose a location-assisted handover for C/U-plane split network architecture. In the considered scenario, a Mobile Relay (MR) is installed on the HSR and serves in-train UEs who execute handover simultaneously. Based on C/U-plane split network architecture, the macro BS assigns an appropriate target BS for the MR during movement. We consider the unique characteristic of HSR, i.e., the train moves in a fixed trajectory, and it is thus possible to predict the forthcoming BSs and complete the handover procedure in a timely fashion. We divide the coverage of the macro BS into the center region and border region. When the MR is in the center region, the handover request is sent immediately when macro BS detects a target sector with better Received Signal Received Power (RSRP). For the MR in the border region, the approaching BS is chosen as the target BS and counting Time to Trigger (TTT) used in the standard handover procedure is eliminated to speed up the handover procedure. System-level simulations are conducted and the results indicate that the proposed handover scheme provides higher UE throughput and reduce the connection cost compared to the standard Long Term Evolution (LTE) handover scheme.

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