Song Tiecheng

Separating cyclostationary signals from spectrally overlapping interference

This paper studies an algorithm about separating spectrally overlapping signals using the cyclostationary properties of signals. On the basis of direct sequence spread system (DSSS), frequency shift filter is added into the receiver of the communication system. Although the structure of frequency shift filter is more complicated than the time-domain filter, it uses both time correlations and frequency spectrum correlations so it can achieve better performances on separating the overlapping signals. After the analysis of cyclostationary characteristic and frequency spectrum correlation, the structure of the frequency shift filter can be gained. Then, a self-adaptive algorithm is utilized for the purpose of achieving optimum multidimensional tap weights of frequency shift components. The simulation results indicate that this method can efficiently separate overlapping signals, and its error rate is lower than the time-domain filter or DSSS system by two orders of magnitude on the condition that high-power interference is added into the system.

Performance analysis for keyhole channel of a quaternion quasi-orthogonal space time block code

Performance analysis for keyhole channel of a new kind of quaternion quasi-orthogonal space time block code is introduced in this paper. First the transmission model is formulated. Then the new code of four transmit antennas is designed, the new code can provide full transmission rate. And zero-forcing linear decoding method is adopted. Lastly the new code is compared with the quaternion quasi-orthogonal space-time block code of four transmit antennas for Rayleigh channel and with the traditional quasi-orthogonal space-time block code of four transmit antennas for keyhole channel. Simulation results show that the new code can increase bit error rate compared with the quaternion quasi-orthogonal space-time block code for Rayleigh channel, and can reduce bit error rate compared with the traditional quasi-orthogonal space-time block code for keyhole channel.Performance analysis for keyhole channel of a new kind of quaternion quasi-orthogonal space time block code is introduced in this paper. First the transmission model is formulated. Then the new code of four transmit antennas is designed, the new code can provide full transmission rate. And zero-forcing linear decoding method is adopted. Lastly the new code is compared with the quaternion quasi-orthogonal space-time block code of four transmit antennas for Rayleigh channel and with the traditional quasi-orthogonal space-time block code of four transmit antennas for keyhole channel. Simulation results show that the new code can increase bit error rate compared with the quaternion quasi-orthogonal space-time block code for Rayleigh channel, and can reduce bit error rate compared with the traditional quasi-orthogonal space-time block code for keyhole channel.