超高速移動環境下正交多頻分工系統之效能評估

在超高速的移動環境下，接收端易遭受到極大的都卜勒效應，系統遭受到的快速衰減影響相當大，傳統用的非時變通道傳送解調架構會造成錯誤率大幅提昇，因此針對了快速衰減影響我們在接收端用了針對時變通道效應而做的解調方式(ML通道估測或MMSE通道估測+時域通道內插改良+LMMSE等化器)來做效能評估，傳送端的領航符元分別使用梳狀跟塊狀排列方式傳送，在能夠忍受的錯誤率下計算出整體領航符元至少需擺放的比例，再跟傳統未考慮時變通道的接收端做比較。在高速鐵路的環境能夠利用各種部分已知的資訊，例如列車行進路線的可預測性、通道脈衝響應的各個多路徑延遲已知特性對運算量的簡化以及效能的提升，還有討論ML及MMSE通道估測的通道脈衝響應最長延遲格數設定有誤差時所造成的影響。

關鍵字

超高速移動環境；時變通道；都卜勒； OFDM ；通道估測

並列摘要

In very high mobility environments, it is easy for the receiver to have large Doppler effects. The influence on the system caused by fast fading is very large. The traditional non-time-varying channels may increase bit error rate. According to fast fading channels, we use decoding methods aim at time-varying channels at receiver ( ML channel estimation or MMSE channel estimation + time-domain interpolation refinement + LMMSE equalizer ) to do performance evaluation. Pilot symbols at transmitter use comb type and block type to transmit. We compute overall pilot symbol ratios at least to transmit for tolerable bit error rate, and compare to traditional receiver which doesn’t consider time-varying channels. In high-speed trains environment, we can use partial known information, for example, predictability of progress routes of train, every multipath delay spread of channel impulse response known characteristics for the complexity reduction and the performance advance. Besides these, we also discuss channel impulse response longest delay spread grid of ML and MMSE channel estimation which sets inaccuracy to see the influence.

並列關鍵字

very high mobility environment ； time-varying channels ； Doppler ； OFDM ； channel estimation

參考文獻

[4]Theodre S. Rappaport, “Wireless Communications: Principles and Practice”,2nd Edition, Prentice Hall PTR, 2002

[5] S. Coleri, M. Ergen, A. Puri, and A. Bahai, “Channel estimation techniques based on pilot arrangement in OFDM systems,” IEEE Trans. Broadcast., vol. 48, no. 3, pp. 223–229, Sept. 2002.

[6]袁文浩,”A study on channel estimation algorithms for WCDMA systems in very high mobility environment”, 國立台灣大學電信工程學研究所碩士論文, June 2006.

[7] J. Irvine, J. -P. Couvy, F. Graziosi, J. Laurila, G. Mossakowski and P. Robin,“System architecture for the MOSTRAIN project (mobile services for high speed trains)”, VTC 1997 IEEE 47th Volume 3, pp. 1917 – 1921, 1997.

[8] C. Kuo and J. F. Chang, “Equalization and channel estimation for OFDM systems in time-varying multipath channels”, IEEE PIMRC’04, pp. 474-478, Sep. 2004.

國際替代計量

超高速移動環境下正交多頻分工系統之效能評估

全文下載

主題瀏覽