頻率選擇性衰減通道之結合通道估計與錯誤更正的四相相位偏移調變碼之設計

Abstract

本篇論文，我們探討頻率選擇性衰減通道之結合通道估計與錯誤更正的四相相位偏移調變碼之設計。經過分析發現：在接收端對通道一無所知的情況下，QPSK調變碼效能受相位干擾的影響比受振幅影響來的大。如果通道間的相位彼此是同步的，並建立一個調變碼的錯誤率聯集上界之閉合形式作為搜尋最佳化調變碼的標準。模擬結果顯示，根據提出的假設與搜尋標準，四相相位調變碼比起二相相位調變碼，效能上有所提升。

In this thesis, we design and examine the QPSK-modulated codes for combined channel estimation and error protection over frequency-selective channels. We found that when QPSK modulation is considered, phase information of the channel coefficients is more essential than the respective amplitude information, particularly for the blind receiver we are interested in. Under the assumption that the unknown phases are synchronized among different channel taps, we establish a close-form-expressed union bound for the error performance and later use it as a criterion to search for the optimal code design. Our simulations show that the QPSK-modulated codes can provide an acceptable improvement over the BPSK-modulated codes.