Signature and Chip Waveform Designs for Asynchronous CDMA Systems(Wireless Communication Technology)

概要

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In this paper, the design of signature wave forms for asynchronous CDMA systems equipped with a correlation receiver is first considered. Optimal signature wave forms that minimize the average multiple access interference (MAI) at the output of a correlation receiver are found, while satisfying the constraint on available transmission bandwidth. Comparison to signature wave forms previously obtained for synchronous systems is also made to justify the superior performance of the designed signature wave forms in asynchronous systems. Furthermore, for direct-sequence CDMA (DS-CDMA) systems with random signature sequences, the use of multiple chip wave forms is also proposed as a means of suppressing MAI. Bandwidth constrained multiple chip wave forms that maximize the signal-to-interference ratio (SIR) at the output of each correlation receiver are found. Numerical results show that by using double chip wave forms instead of a single chip wave form, it is possible to reduce the MAI by 10% for a fixed transmission bandwidth (or equivalently, to save about 10% of transmission bandwidth for a given SIR requirement). The advantage of using double chip wave forms is also demonstrated in terms of the bit error rate (BER), whose calculation is based on our extension to Holtzman's approximation in [1].
社団法人電子情報通信学会の論文
2004-05-01