| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 102 === Multi-carrier code division multiple Access (MC-CDMA) is a promising approach to the challenge of providing high data rate wireless communication. It can be interpreted as CDMA with the spreading taking place in the frequency rather than temporal domain. However, one of drawbacks of MC-CDMA systems is high peak-to-average power ratio. Recently, the comb-spectrum (CS)
CDMA system was proposed. One user’s data are spread on an assigned interleaved subcarrier group. In addition, the corresponding CS codes in the time domain are of equal magnitude. Therefore, the peak-to-average power ratio can be reduced. However, the spectrum of the CS code is not flat and parts of spectrum are zeros which cause the bit error rate (BER) degradation. A sequence of complex number is called sparse Gaussian integer perfect sequence (SGIPS) whose real parts and imaginary parts are both integers and whose any cyclic shift is orthogonal to each other. Moreover, the number of nonzero elements of GIPS is independent on the sequence length and much less than the sequence length. In this paper, the SGIPS is utilized as the spreading codes and a novel comb-spectrum code division multiple access system is proposed. From simulation results, the BER of the proposed systems is better than the traditional CS-CDMA systems. For quadrature phase shift keying, the proposed scheme gains about 3dB when BER = 10-4.
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