Key Technologies Of Two-dimensional Spread Spectrum

Direct sequence spread spectrum (DSSS) technology is the key technology for the third generation mobile communication systems. In this paper, we discuss the general two-dimensional spread spectrum (2DSS) technology, which is the combination of DSSS and multi-carrier code division multiple access (MC-CDMA). This is a novel spread spectrum access method in mobile communication.2DSS applies orthogonal frequency division multiplexing (OFDM) into CDMA, thus it has advantages of both of them. It spreads the original data stream by DSSS, then spreads the spread signal by discrete multi-carrier (DMC) technology, finally, modulates them to orthogonal sub-carrier for transmission. This technology will have brilliant future for its efficiency in canceling ISI and its advantage of frequency diversity.A whole model of 2DSS is present in the second chapter and its function is showed by analysis of its receiver and transmitter.In order to improve the rate of transmitting information, the M-ary 2DSS is proposed in the third chapter. It is the combination of M-ary spread spectrum and 2DSS. The models of its receiver and transmitter are drawn. And we analyze its performance under Rayleigh channel.Among technologies concerning the third generation mobile communication, the rake receiving technology is accepted in order to counteract the frequency selective fading caused by the signal multi-path propagandizing. The rake receiver detects all the multi-path signals respectively, and combines all the detected signals to recover the transmitted information by the transmitter. When the delay between multi-paths is less than the resolving power of the rake receiver, the receiver can't acquire each path accurately, and the receiver has to acquire each path that makes the receiver complicated. Considering that the DSSS technology is a special example of the 2DSS technology, a de-spread method of DS-CDMA based on time-frequency 2DSS is brought forward in the paper.The basal principle of the de-spread method of DS-CDMA based on...