Performance Evaluation on Orthogonal Frequency Division Multiplexing System in Very High Mobility Environment

• Main Authors: Ming-Dao Chuang, 莊明道
• Other Authors: 張進福
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/87156629519673657864

碩士 === 國立臺灣大學 === 電信工程學研究所 === 95 === 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.