非理想通道的調變技術

Modulation Techniques for Non-ideal Channels

卓世明(Shih-Ming Cho)

指導教授 ： 鐘嘉德 ； 魏瑞益

國立中央大學/資訊電機學院/電機工程學系/博士(2006年)

摘要

在這本論文裡，我們針對三種非理想通道（non-ideal channels），分別提出新的調變技術。第一部分，探討對多載波信號（multicarrier signals）設計一種恆定封蓋（constant envelope）的相位調變（phase modulation），以解決多載波信號OFDM（orthogonal frequency division multiplexing）於傳送時，高峰均功率比值（peak-to-average power ratio）所產生的問題。新的信號經過功率放大器時，可使得信號傳送時能被能有效地被功率放大器放大。
在本文第二部分中，假設傳送端不知通道訊息時，我們針對使用傳送端多天線（multiple transmit antennas）系統，在flat Rayleigh衰落通道（fading channel）裡，設計一種可選擇部份天線傳送的編碼調變（coded modulation）。因為只有部份天線被使用，我們發現某些新的設計除了可以降低硬體複雜度外，而且得到近似於使用全部天線時的系統錯誤性能（error performance）。
本文第三部分，我們對頻譜嚴重衰弱的通道（fading channel with spectral nulls），討論一種新的多載波信號來取代OFDM系統。由於使用新的多載波信號基底（signal basis），我們發現某些原在OFDM系統裡為頻譜嚴重衰弱通道，在新的系統中不再為嚴重衰弱通道。同時，對系統進行預編碼（precoding）時，新的系統會比OFDM系統，較能得到與通道條件無關的預編效果與錯誤效能。

關鍵字

非理想通道 ； 多載波信號 ； 傳送端多天線系統 ； 預編碼

並列摘要

In this dissertation, we propose three novel modulation techniques for the non-ideal channels. The first part of dissertation is to investigate a constant envelope design by phase modulating the multicarrier signals, which generally involves the problem of large peak-to-average power ratio. The resultant constant-envelope signal enables the operation of the transmitter’s power amplifier at the saturation point and thus maximizes the achievable power efficiency.
In the second part of this dissertation, a coded modulation in conjunction with transmitter antenna selection is designed for the flat Rayleigh fading channel, when the transmitter is lack of the channel state information. Despite the hardware complexity is reduce since only partial transmitter’s antennas are used, it found some coded designs can also provide the competitive error performance to the schemes of using all transmit antennas.
In the third part of this dissertation, the novel multicarrier signals by using a set of orthogonal sinusoidally pulsed carriers set of novel subcarrier signal basis waveforms for the multicarrier OFDM system are studied. Since the use of new multiplexing signal bases, the spectral nulls in OFDM system are not deep faded any more in new multicarrier modulation system. Moreover, when the precoding is used for both systems, it is found that the new system can offer the precoding gain and error performance independent to the channels than the OFDM system.

並列關鍵字

Non-ideal Channels ； Multi-carrier ； Multiple Antenn

參考文獻

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