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| Effect of Relative Delay on Performance of Multiuser Detection in Asynchronous DS-CDMA Systems: Analysis and Evaluation |
| Wang Ling①;Jiao Li-cheng①;Tao Hai-hong②; Liu Fang③ |
| ①Institute of Intelligent Information Processing, Xidian University, Xi’an 710071, China;②National Key Lab. for Radar Signal Processing, Xidian University, Xi’an 710071, China;③School of Computer Science and Technology, Xidian University, Xi’an 710071, China |
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Abstract Multiuser detection is a key technique in DS CDMA systems. The received signal of uplink receiver is superposition of the spreading signal transmitted by users over asynchronous channels. Many multiuser detectors deal with discrete signal sampled at symbol or chip rate after passing through matched filterers. However, different relative delay between users results in distinct partial correlation coefficients thus bringing about distinct performance of multiuser detectors. It is very important to effectively evaluate the average and extreme performance of system. In this paper, the expression of average partial correlation coefficients is analyzed and the corresponding numerical computation method is proposed. On the other hand, relative delay corresponding to the maximal and minimal correlation coefficients is also solved by the evolution algorithm. Based on the obtained results, the performance of the decorrelating and Minimum Mean Square Error (MMSE) multiuser detectors in asynchronous DS-CDMA systems are evaluated by numerical simulation.
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Received: 08 May 2004
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2005, Vol. 27 
