Studies On Two-dimensional Spread Spectrum Technology

Direct sequence spread spectrum (DSSS) technology is the central technology for the third generation mobile communication systems. In this paper, we discuss the two-dimensional spread spectrum technology (2D-CDMA), which is the combination of DSSS and multi-carrier code division multiple access (MC-CDMA). This is a novel spread spectrum multiple access method in mobile communication.2D-CDMA applies orthogonal frequency division multiplexing (OFDM) into CDMA, thus has advantages of both of them. It copies the original data stream to several parallel data streams, spreads them in both time and frequency domain, then modulates them to orthogonal sub-carriers for transmission. This technology will have brilliant future for its efficiency in canceling ISI and its advantage of frequency diversity.A whole model of 2D-CDMA is presented in this paper and it function is showed by mathematical analysis of its transmitter and receiver.It is the performance of the communication system that determines its application value. Therefore, the performance of 2D-CDMA in both AWGN and Rayleigh fading channel is analyzed and the results show that this technology has the ability to counteract Rayleigh fading.Frequency diversity is a main advantage of this system, because of the employment of multi-carrier. This paper applies different combination methods into the system and gets their performance comparison.At the end of this paper, we focus on the channel estimator. Several estimation methods, such as linear Interpolation estimation, estimation based on DFT and estimation based on transform domain, are analyzed and simulated. The computer simulation results show that the estimator based on transform domain is better than the other two.