室內環境下直接序列分碼多工之超寬頻系統的多用戶偵測技術

Linear Multiuser Detection for Asynchronous DS-CDMA UWB in the Indoor Environments

陳紀憲(Chi-Hsien Chen)

指導教授 ： 陳光禎

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.00194

摘要

針對超寬頻脈波直序展頻多工存取系統，我們說明了可適性最小均方誤差多用戶接收器可以有效地收集由多路徑而來的能量而消減多重存取及符際間和位元間的干擾如同參考文獻[10]所言。因為超寬頻系統的路徑解析度相當細微，而使通道分解成相當高程度的多路徑是此系統的最主要的問題所在，也是我們在此論文中探討的重點。在可控制的複雜度之下，可適性地實現最小均方誤差多用戶接收器被我們證實出有能力在表現上提供可預期增益。再者，我們提出非同調最小均方誤差接收器如果通道的相位是隨時間而變化。我們證實用來調整濾波器係數的非同調可適性演算法在相位變化的環境下仍可以收斂到所欲求的結果，反之，傳統的可適性演算法卻發散掉。最後，我們提出可適性濾波器組當作M維二相正交鍵直序展頻分碼多工系統的多用戶接收器。我們也算出理想上最小均方誤差接收器的表現，其中也包括了二維二相正交鍵，也就是一開始我們提到的架構。我們證實此可適性接收器相對於理想情況下付出幾dB的損失。而理想上的最小均方誤差接收器也大概比AWGN通道下的情況少6dB。所以，在此考慮的接收器架構是可以抗近-遠效應的

關鍵字

超寬頻 ； 多用戶偵訊 ； 直序分碼多工

並列摘要

We demonstrate that the adaptive MMSE multiuser receiver can effectively gather multipath energy and eliminate the multiple-access, intersymbol and interchip interference for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access following on the early work [10]. A high level of multipath fragmentation caused by the fine path resolution of wideband (3.1-5.15 GHz) channel is the dominant problem, which we treat in this thesis. We prove that the adaptive implementation of MMSE receiver has the potential of providing the anticipated performance gains with a complexity that would be manageable. Also, we propose a noncoherent MMSE receiver if the channel phase is time-variant. We show that the noncoherent adaptive algorithms for filter adjustment can converge in the presence of phase variations, whereas their conventional counterparts diverge. Finally, we propose adaptive filter banks as the multiuser receiver for MBOK DS-CDMA UWB systems. We also compute the analytic performance of ideal MMSE for MBOK system from the idea of its special case, 2-BOK. The adaptive MMSE receiver shows only an additional decibel of loss over the ideal version. And the ideal MMSE receiver also showed only a 6-dB penalty versus the AWGN channel case. Hence, the regarded linear MBOK adaptive multiuser receiver is near-far resistant.

並列關鍵字

UWB ； MUD ； MBOK ； DS-CDMA

參考文獻

[2] Moe Z. Win and Robert A. Scholtz, “Ultra-wide bandwidth time-hopping spread spectrum impulse radio for wireless multiple-access communications,” IEEE Transactions on Communications, vol. 48, issue: 4, pp. 679-689, April 2000.

[4] M. Win and R.A. Scholtz, “On the Robustness of Ultra-Wide Bandwidth Signals in Dense Multipath Environments,” IEEE Comm. Letters, Feb. 1998, no.2, vol. 2

[5] Verdu, Sergio, Multiuser Detection, New York: Cambridge University Press; 1998.

[6] H. Poor and S. Verdu, “Probability of error in MMSE multiuser detection.” IEEE Transactions on Information Theory, vol. 43, pp. 858–71, May 1997.

[7] John G. Proakis, Digital Communications, McGraw Hill, 4th edition, 2001.