直序式超寬頻通訊系統在多路徑通道環境下之效能分析

Performance Analysis of a Multi-User DS-UWB System under Multipath Effects

沈允中(Yun-Chung Shen)

指導教授 ： 譚旦旭

國立臺北科技大學/電資學院/電機工程系所/碩士(2007年)

摘要

在多用戶情況下，超寬頻(UWB)通道的多重路徑效應將使得展頻碼間不再是正交，進而衍生嚴重的多重存取干擾(MAI)，造成系統效能的大幅下降。過去幾年中，已有若干有關超寬頻系統效能的分析研究。然而，這些研究僅只考慮可加性高斯白雜訊(AWGN)的通道效應，而忽略超寬頻系統中嚴重的多重路徑效應，因而導致不精確的結果。為補前人研究之不足，本論文將納入多重路徑的影響，以推導出更精確的理論。所推導的內容包括位元錯誤率(BER)效能、系統可以支援的用戶人數，以及系統可以允許的傳輸位元率。

關鍵字

多重存取干擾 ； 多重路徑通道 ； 直序式分碼多工超寬頻通訊

並列摘要

For the multi-user application the multiple access interference (MAI) due to imperfect orthogonality between spreading codes induced by UWB dense multi-path significantly degrades system performance. Over the past few years, performance analyses for various UWB systems in an AWGN environment have been presented. However, those works did not consider the multipath effect of UWB channel; thus leading to an unacceptable analytical result. To compensate for the shortage of previous works, this research aims to theoretically derive accurate performance of DS-UWB system in the presence of AWGN, MAI, and multipath effect. The BER performance will be analyzed in terms of the number of active users. An upper bound on the maximum number of users supported by the system will be derived. In addition, the allowed multiple access transmission rate will also be evaluated.

並列關鍵字

Multiple Access Interference (MAI) ； Multipath Channel ； Direct Sequence Ultra-Wideband (DS-UWB)

參考文獻

[2] M. Z. Win and R. A. Scholtz, “On the robustness of ultra wide bandwidth signals in dense multipath environments,” IEEE Communications Letters, pp. 51-53, 1998.

[5] M. Z. Win and R. A. Scholtz, “Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple-access communications,” IEEE Transactions on Communications, pp. 679-691, 2000.

[6] A. Taha and K. M. Chugg, “A theoretical study on the effects of interference on UWB multiple access impulse radio,” in Proc. Asilomar Conf. Signals, Systems and Computers, pp. 728-732, 2002.

[7] N. Boubaker and K. B. Letaief, “Ultra wide-band DSSS for multiple access communications using antipodal signaling,” in Proc. of IEEE International Conference on Communications, pp. 2197-2201, 2003.

[8] V. S. Somayazulu, “Multiple access performance in UWB systems using time hopping versus direct sequence spreading,” in Proc. IEEE International Conference on Wireless Communications and Networking Conference, pp. 522-525, 2002.