結合空時編碼傳送分集與可適性調變之正交多載波系統在多路徑瑞雷衰減通道下之性能分析與研究

Performance Analysis and Study of Orthogonal Multicarrier System with Space-Time Coded Transmit Diversity and Adaptive Modulation over Multipath Rayleigh Fading Channels

謝育林(Yuth-Lin Hsieh)

指導教授 ： 黃正光

元智大學/工程學院/電機工程學系/碩士(2002年)

摘要

在本論文中，吾人考慮了結合可適性調變與空間時間編碼傳送分集之正交多載波系統的性能分析與探討。首先，我們假設通道為多路徑瑞雷衰減通道，而OFDM傳送訊號的保護區間大於最大通道延遲，在這個條件之下，吾人可推導出SISO CP-OFDM以及2ISO STC-OFDM系統在不同之BPSK/QPSK/Square-QAM調變下之性能，且經由電腦模擬實驗驗證無誤。同樣地，有了SISO CP-OFDM系統以及2ISO STC-OFDM系統之瞬時訊雜比的機率分布函數，以及固定調變下，每種調變的位元錯誤機率BER之公式，吾人即可推導出這兩種系統使用可適性調變時之位元錯誤率性能，以及系統平均Throughput之BPS（bits/symbol）。最後，吾人再根據這些推導值，用電腦模擬來評估這兩種系統在各種狀況下的性能表現。除此之外，我們也論及了SISO MC-CDMA系統，以及具空時編碼之2ISO MC-CDMA系統在下鏈路多用戶傳輸時的性能，並以電腦模擬比較之。

關鍵字

多載波 ； 空時編碼 ； 正交分頻多工 ； 多載波分碼多工 ； 可適性調變 ； 分集階數 ； 傳送分集 ； 多路徑瑞雷衰減

並列摘要

In this thesis, we study and analyze the error performance of the technique of space-time coded transmit diversity and combined it with adaptive modulation in the orthogonal multicarrier system over multipath Rayleigh fading channels. First of all, we assume that our target system is over multipath Rayleigh fading channels, and the guard interval of the transmitted OFDM signal is larger than the maximum path delay spread. Under above assumptions and applying the property of frequency ergodicity, the upper bound error performance of the SISO OFDM/2IMO STC-OFDM system with M-ary QAM is desired and the performance is just equal to that of single carrier systems with the same diversity order over flat fading channels. Furthermore, using Monte-Carlo trials to simulate every channel condition and according it to switch the appropriate modulation level, then a semi-analysis method for calculating the average BER and BPS, i.e. bits per symbol, is also introduced for the OFDM system with adaptive modulation. Finally, computer simulation results will meet the same conclusion of our performance analysis. Besides, using pure Monte-Carlo simulation, comparisons between the performance of multiuser SISO MC-CDMA system and 2ISO STC-MC-CDMA system are also represented.

並列關鍵字

multicarrier ； space-time coding ； OFDM ； MC-CDMA ； adaptive modulation ； diversity order ； transmit diversity ； multipath Rayleigh fading

參考文獻

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