台灣高鐵沿線行動通信基地台佈建策略及通訊品質改善之研究

Abstract

綜觀世界各國交通運輸發展趨勢，高速鐵路無疑是中、長程陸運之最佳選擇。因此，解決高速移動情況下行動通信可能遭遇的問題，實為一項重要課題。本論文首先探討各國高速移動通信所採用的可行技術，進而說明台灣高速鐵路所使用的非專屬基地台涵蓋方式。考量高速移動環境下可能的訊號衰減及列車金屬外殼所造成之穿透損失等因素，透過鏈路預算及傳播路徑損耗模型的推導，求出高速移動環境下GSM及WCDMA系統基地台合理的涵蓋半徑；同時以細胞重選及交遞所需最小時間，算出基地台間最小的重疊覆蓋區域以得到基地台最佳佈建方式。其次透過調整GSM及WCDMA系統基地台細胞重選及交遞參數使其適合服務於高速移動狀況，降低通話建立失敗率、交遞失敗率等品質指標。論文最後提出於車站引入階層式細胞架構(HCS)並配合基地台參數設計，以解決車站周邊基地台之交遞及建立失敗率因車站內人潮爆增導致偏高的問題。藉由基地台涵蓋範圍及Handover、Cell Reselection參數的調整規劃，以期用戶於乘坐高鐵列車時，能享有一般情況下的語音及數據服務通訊品質。

Looking at the trends of the world transportation,the high-speed railway is with no doubt, the best choice for medium and long distances transport mode.Therefore,it is the most important thing to solve the problems that people communicated in the high mobility environments.This study first discussed the mobile communication technologies using in the high mobility environments,and then described the shared infrastructure using in Taiwan high-speed railway(THSR). Considering the impacts such as signal attenuation due to fast moving of THSR and penetration loss caused by metal shell of the train, through the derivation of link budget and propagation model to calculate the reasonable GSM and WCDMA BTS coverage area.Meantime we also calculated the shortest overlapping area between two cells accordin to the needed time of handover or cell reselection procedure.Secondly we adjusted the cell reselection and handover parameters of GSM and WCDMA systems for adapting the high mobility environments to reduce call drop and handover failure ratio. In the end,the study proposed a method of hierarchical cell structure(HCS) and BTS parameters design using in the railway stations to reduce the handover and establishment failure ratio due to the shortage of base station radio resources. By way of adjusting the handover and cell reselection parameters and well planning base stations coverage area,the subscribers taking THSR could have better quality for voice and data services.