A generalized QS-CDMA system and the design of new spreading codes

Author

Long, Biqi ; Zhang, Ping ; Hu, Jiandong

Author_Institution

YOZAN Inc., Tokyo, Japan

Volume

47

Issue

4

fYear

1998

fDate

11/1/1998 12:00:00 AM

Firstpage

1268

Lastpage

1275

Abstract

A generalized quasi-synchronous code-division multiple-access (QS-CDMA) system for digital mobile radio communications is proposed. In a QS-CDMA system, the relative time delay between the signals of different users is random and restricted in a certain time range, that is, the signals are quasi-synchronous. The analysis shows that the multiple-access interference (MAI) of the QS-CDMA system is determined by the cross-correlation between spreading codes around the origin. To minimize the MAI of the QS-CDMA system, we design a new set of spreading codes. The performance is evaluated according to the criteria of the bit error rate (BER). Analytic results of the BER are obtained by using two methods: Gaussian approximation and characteristic function approaches, which are checked by modified Monte Carlo computer simulations known as “importance sampling.” The results indicate that the performance of the QS-CDMA system using the spreading codes we construct is much improved

Keywords

AWGN channels; Gaussian processes; approximation theory; cellular radio; code division multiple access; codes; correlation methods; delays; digital radio; error statistics; importance sampling; personal communication networks; radiofrequency interference; spread spectrum communication; AWGN channel; BER; Gaussian approximation; bit error rate; cellular radio system; characteristic function; cross-correlation; digital mobile radio communications; generalized QS-CDMA system; importance sampling; modified Monte Carlo computer simulations; multiple-access interference; performance evaluation; personal communication networks; quasi-synchronous code-division multiple-access; quasi-synchronous signal; random time delay; spreading codes design; Bit error rate; Computer simulation; Delay effects; Gaussian approximation; Land mobile radio; Mobile communication; Monte Carlo methods; Multiaccess communication; Multiple access interference; Performance analysis;

fLanguage

English

Journal_Title

Vehicular Technology, IEEE Transactions on

Publisher

ieee

ISSN

0018-9545

Type

jour

DOI

10.1109/25.728516

Filename

728516