- 學位論文
空-時碼於無線部份干擾環境之研究
Space-Time Coding for Wireless Channels with Partial-Band Noise Jammers
摘要
在無線干擾的環境中，由於通道衰減的效應以及故意的干擾源，使得在接收端所收到的傳送訊號產生嚴重的失真。 跳頻展頻技術是一般最常用來抑制干擾效應的系統；而空時碼(space-time codes)具有分集增益(diversity gain)和編碼增益(coding gain)可以有效的降低通道衰減的效應。 因此，本篇論文中，我們在具有衰減及干擾的環境中傳輸訊號，然後藉由空時碼與跳頻的技術來降低干擾的影響 ，提高整體的系統效能。 在解碼上，我們推導出在路徑增益(path gain)已知或未知條件下的最大可能性解碼(maximum likelihood decoding)，由於ML 解碼相當的複雜，且基於複雜度和實現難易程度的考量，因此，我們提出了一些次佳碼來降低複雜度，並將其對應的結果作模擬。 除此之外，我們也提出在無線干擾通道下好的空時碼準則，且利用電腦尋找出好的空時碼。 最後經由模擬結果證明出在高傳輸速率下空時碼比傳統單進單出(SISO)編碼效能來的更佳。
並列摘要
In wireless jamming environments, the transmitted signals suffer from intentional jammers and undesired channel impairments. Conventionally, frequency-hopping spread spectrum (FHSS) are employed to mitigate the jamming effect. Space-time coding (STC) introduces a temporal and spatial correlation into the transmitted signals by using multiple antennae and has been shown to provide excellent performance against multipath fading. In this thesis, space-time coding is combined with FHSS to improve the system performance. With respect to the STC/FHSS system, we first derive the maximum likelihood decoding no matter whether the channel state information is available or not. Some suboptimal decoding schemes are invented for complexity reduction. In addition, we analyze the performance of the STC/FHSS system and propose the design criteria of space-time codes for the wireless jamming channels. Good codes are then obtained by a computer search. Verified by the simulation results, the suboptimal decoding schemes achieve near-optimum performance and the STC/FHSS system outperforms the conventional schemes in terms of both signal-to-noise ratio and bandwith efficiency.
參考文獻
延伸閱讀
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