改良型粒子群演算法於直序式超寬頻多用戶偵測器之應用研究

Application of Modified Particle Swarm Optimization Algorithm to Multi-user Detection in DS-UWB System

鄭秋君(Chiu-Chun Cheng)

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

超寬頻無線通訊的多重路徑效應在多用戶情況下，容易影響展頻碼之間的正交特性，造成嚴重的多重存取干擾（Multi-Access Interference, MAI）。為了消除MAI，最佳多用戶偵測器雖能達到極佳的系統效能，但因計算複雜度太高，故無法實現。為了在效能與複雜度之間取得平衡，若干研究提出了次佳的方法，例如應用基因演算法之多用戶偵測器（Genetic algorithm-based multi-user detector, GA-MUD），但GA-MUD仍然存在著BER效能未盡理想及收斂速度不夠快等問題。
為改善收斂速度及提升BER之效能，我們應用粒子群演算法(Particle swarm optimization algorithm, PSO)取代GA，提出了一種新的PSO-MUD系統架構，此架構利用Rake Receiver來產生PSO初始解。另外，為了增加粒子在搜尋空間中的多元性，PSO結合了GA的突變(Mutation)機制，我們稱為PSO_Mutation-MUD。模擬結果顯示，PSO_Mutation-MUD在越惡劣通道環境中其效能改善之效果越顯著。我們比較了PSO_Mutation、PSO_CW、PSO_TCAV，以及GA等MUD之效能，模擬結果證實我們提出的PSO_Mutation-MUD架構有最好的效能。

關鍵字

直序超寬頻 ； 粒子群演算法 ； 基因演算法 ； 突變 ； 多用戶偵測器

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 degrades system performance. Though optimum multi-user detector (OMD) can achieve remarkable performance, its computational complexity is too high to implement. Therefore, many sub-optimal multi-user detectors (MUDs) have been proposed to attain best trade-off between performance and complexity, such as Genetic algorithm-based multi-user detector (GA-MUD). However, BER performance of GA-MUD is not good enough and its convergence rate is slow.
In order to increase the convergence rate and BER performance, we apply Particle Swarm Optimization algorithm (PSO) to replace GA to develop a new PSO-based MUD. This MUD employs rake receiver to generate initial solution for PSO-based optimization. Moreover, we combine mutation mechanism of GA to PSO for increasing diverseness of particles in searching space which is called PSO_Mutation-MUD. Experimental results show that the proposed PSO_Mutation-MUD attains highest gain in the CM4 environment. We also compare the performances between PSO_Mutation-MUD, PSO_CW-MUD, PSO_TCAV-MUD, and GA-MUD. The result reveals that our proposed PSO_Mutation-MUD yields the best performances over UWB channels.

並列關鍵字

Direct-sequence Ultra-Wide Band (DS-UWB) ； Particle Swarm Optimization (PSO) ； Genetic Algorithm (GA) ； Mutation ； Multi-user Detector (MUD)

參考文獻

[2] S. Stroh, “Ultra-Wideband: Multimedia Unplugged,” IEEE Spectrum, 2003.

[8] S. R. Saunders, “Antennas and Propagation for Wireless Communication Systems,” Published by John Wiley & Sons. 1999.

[11] M. Pendergrass, “Empirically Based Statistical Ultra-Wideband Channel Model,” IEEE P802.15-02/240-SG3a.

[16] A. Molisch, M. Win and D. Cassioli, “The Ultra-Wide Bandwidth Indoor Channel: from Statistical Model to Simulations,” IEEE P802.15-02/284-SG3a and IEEE P802.15-02/285-SG3a.

[17] J. Cramer, R. Scholtz and M. Win, “Evaluation of an Indoor Ultra-Wideband Propagation Channel,” IEEE P802.15-02/286-SG3a and IEEE P802.15-02/325-SG3a.