張進福臺灣大學：電信工程學研究所許嘉倫Hsu, Chia-LunChia-LunHsu2007-11-272018-07-052007-11-272018-07-052007http://ntur.lib.ntu.edu.tw//handle/246246/58541本研究的目的在於探討“在高速鐵路環境下，提供正交分頻多工無線通訊系統有效的通道估測方式”。在高速移動環境下，由於無線通道中多重路徑干擾及都卜勒效應所產生的種種現象，使得無線通訊信號會遇到許多干擾，造成傳輸困難。雖然有直視波的存在，且郊區之延遲路徑較少可簡化問題，但This paper focuses on “effective channel estimations for OFDM wireless communication system in high speed train environment.” Because of multi-path interference and Doppler effect, wireless communication signals are interfered and hard to be transmitted. Although there are the existence of line of sight and fewer delay paths in high speed train environment to improve the situation, we still have to use more known signals to estimate the channel state correctly, which will lower the transmission efficiency. In this paper, we will discuss some methods to improve this situation. We first use traditional linear channel estimation to figure out how many known signals are in use, and how much space do we need to set for the pilots in high mobility environment. Then, we use the method of updating channel state information to achieve lower bit error rate and higher transmission efficiency in high mobility environment. In order to improve the transmission efficiency, we also try many kinds of methods to solve the problems under different situations to achieve our goal. Finally, we compare each method of channel estimation by simulation, and we propose some ways that we can further improve the system in the future.目 錄 口試委員會審定書........................................................................................i 誌謝................................................................................................................i 中文摘要......................................................................................................iii 英文摘要.......................................................................................................v 第一章 緒論.................................................................................................1 1.1 前言.................................................................................................1 1.2 研究動機.........................................................................................3 1.3 研究背景.........................................................................................3 1.4 無線連結之架構.............................................................................4 1.5 本章結論與論文架構...................................................................11 第二章 高速鐵路環境對正交分頻多工系統之影響及線性通道估測之參數設計.....................................................................................................15 2.1 正交分頻多工(OFDM)系統介紹.................................................15 2.2 通道環境的介紹...........................................................................17 2.3 高速鐵路通道環境對OFDM訊號傳輸的影響............................24 2.4 高速鐵路環境下OFDM線性通道估測的調配............................27 2.5 結論...............................................................................................35 第三章 通道估測更新系統在高速鐵路環境下系統效能之改進...........37 3.1 以資料驅動的方式作通道估測...................................................37 3.2 利用兩邊夾擠方式的資料反饋通道更新系統...........................46 3.3 利用高速鐵路環境特性做通道估測更新的改善.......................50 3.4 在頻域做資料反饋的通道估測更新技術...................................54 3.5 結論...............................................................................................62 第四章 利用鐵路路徑已知資訊修正都卜勒偏移對傳輸效能之改進...65 4.1 行進方向夾角的討論...................................................................65 4.2 利用已知路徑補償都卜勒偏移...................................................71 4.3 對通道已知架構之實際模擬與比較...........................................72 4.4 結論...............................................................................................78 第五章 結論...............................................................................................81 5.1 結論...............................................................................................81 參考文獻.....................................................................................................85 圖 目 錄 圖1-1 系統架構............................................................................................4 圖1-2 單鏈架構示意圖................................................................................5 圖1-3 單鏈使用中繼器之架構....................................................................6 圖1-4 雙鏈使用集中器之架構....................................................................7 圖1-5 雙鏈列車使用完整基地台之架構....................................................7 圖1-6 大涵蓋範圍全向性天線的一維細胞規劃........................................9 圖1-7 小涵蓋範圍系統示意圖..................................................................10 圖1-8 整體系統架構圖..............................................................................12 圖2-1 OFDM系統方塊圖...........................................................................16 圖2-2 保護區間示意圖..............................................................................17 圖2-3 CP示意圖..........................................................................................17 圖2-4 都卜勒效應示意圖..........................................................................18 圖2-5 多重路徑干擾延遲分布圖..............................................................19 圖2-6 同步誤差與保護區間示意圖..........................................................26 圖2-7 各種不同的領航字元擺放方式......................................................29 圖2-8 高速移動環境下載波數64的線性通道估測比較圖......................32 圖2-9 高速移動環境下載波數512的線性通道估測比較圖....................33 圖2-10 高速移動環境下載波數1024的線性通道估測比較圖................33 圖2-11 高速移動環境下不同載波數的通道線性估測比較圖................34 圖3-1 以資料驅動方式作通道估測之傳送機及接收機方塊圖..............38 圖3-2 傳送資料必須先分解為數個編碼區塊..........................................40 圖3-3 載波數64之線性估測與通道估測更新在高速鐵路環境下之效能 表現................................................................................................41 圖3-4 線性通道估測與通道估測更新對通道變化速度的適應力比較..42 圖3-5 載波數512之線性估測與通道估測更新在高速鐵路環境下之效能表現................................................................................................43 圖3-6 載波數512之通道估測更新在移動速度較低時之效能表現........44 圖3-7 載波數1024之線性估測與通道估測更新在高速鐵路環境下之效能表現............................................................................................45 圖3-8 通道估測更新系統之頁框格式示意圖..........................................47 圖3-9 不同頁框長度在高速移動環境下的效能表現..............................48 圖3-10 載波數512之兩邊夾擠通道估測更新在高速鐵路環境下之效能表現................................................................................................49 圖3-11 載波數1024之兩邊夾擠通道估測更新在高速鐵路環境下之效能表現................................................................................................50 圖3-12 利用高速鐵路環境特性通道估測更新系統之頁框格式示意圖....................................................................................................51 圖3-13 利用高速鐵路環境特性之通道估測更新系統的效能比較(短符碼數) ..............................................................................................52 圖3-14 利用高速鐵路環境特性之通道估測更新系統的效能比較(長符碼數) ..............................................................................................53 圖3-15 利用高速鐵路環境特性且兩邊夾擠之通道估測更新系統的效能比較................................................................................................54 圖3-16 完全追跡通道時域變化之領航字元擺放方式............................55 圖3-17 在頻率以資料驅動方式作通道估測之傳送機及接收機方塊圖....................................................................................................56 圖3-18 載波數1024之線性估測與在頻域通道估測更新在較短頁框時效能表................................................................................................58 圖3-19 載波數1024之線性估測與在頻域通道估測更新在較長頁框時效能表現............................................................................................59 圖3-20 串連加密擾亂之示意圖................................................................60 圖3-21 以新加密方式在頻域領航字元間隔較小之通道估測更新的效能表現................................................................................................61 圖3-22 以新加密方式在頻域領航字元間隔較大之通道估測更新的效能表現................................................................................................62 圖4-1 鐵路環境架構示意圖......................................................................66 圖4-2 載波數1024時域間隔1之不同行進夾角下的線性通道估測效能表現....................................................................................................67 圖4-3 載波數1024時域間隔4之不同行進夾角下的線性通道估測效能表現....................................................................................................68 圖4-4 載波數512都卜勒偏移50之不同行進夾角下的通道估測更新效能表現................................................................................................69 圖4-5 載波數1024高速移動時不同行進夾角下的通道估測更新效能表現....................................................................................................70 圖4-6 傳統接收機架構..............................................................................72 圖4-7 接收機都卜勒偏移補償架構..........................................................72 圖4-8 載波數64之直視波都卜勒偏移已知線性通道估測頻域間隔比較圖....................................................................................................73 圖4-9 載波數64之直視波都卜勒偏移已知線性通道估測時域間隔比較圖....................................................................................................74 圖4-10 載波數512之直視波都卜勒偏移已知線性通道估測時域間隔比較圖................................................................................................75 圖4-11 載波數1024之直視波都卜勒偏移已知線性通道估測時域間隔比較圖................................................................................................76 圖4-12 直視波都卜勒偏移已知通道估測更新在不同載波數之比較圖....................................................................................................77 圖4-13 直視波都卜勒偏移已知線性通道估測與通道估測更新之比較圖....................................................................................................78 表 目 錄 表2-1 COST259的通道模型......................................................................22 表2-2 減化之COST259 RA通道模型.......................................................23 表2-3 不同載波數的領航位元適當的時間以及頻率間隔......................31en-US多重路徑干擾都卜勒效應線性通道估測通道估測更新傳輸效率multi-path interferenceDoppler effecttransmission efficiencylinear channel estimationupdating channel state informationthesis