An Optimal Transmission of Improper-Complex Second-Order Stationary Data Sequence in Cyclostationary Interference

In this paper, the transmission of an improper complex second-order stationary data sequence is considered over a strictly band-limited and frequency-selective channel whose output is corrupted by an additive proper-complex cyclostationary interference. It is assumed that the data symbols are linearly modulated by a transmit waveform and that the received signal is demodulated by a widely linear filter with two receive waveforms. As the objective function and the constraint of the optimization problem, the mean-squared estimation error of the improper complex data symbols and the average transmit power are chosen, respectively. The problem is solved in the frequency domain by introducing the notion of the impropriety frequency function of a discrete-time random process and by performing a line search combined with an iterative algorithm. It is shown that the optimal system well exploits the cyclostationarity and the impropriety of the received signal in effectively suppressing the inter symbol interference and the cyclostationary interference.