When the variable k exceeds the specified number (S4: Yes), the signal generator 12 performs mapping for each symbol of each series in S7. In the example depicted in FIG. 5, the mapper 23 generates a modulated signal indicating the data series, the mapper 24 generates a modulated signal indicating the artificial noise series AN1, and the mapper 25 generates a modulated signal indicating the artificial noise series AN2. The signal combiner 13 combines these modulated signals.
FIG. 7 is a flowchart illustrating an example of a method for generating an artificial noise series. The processes of this flowchart correspond to S3 in FIG. 6. Thus, the correlation series generator 21 generates an artificial noise series AN1 from a data series.
In S11, the correlation series generator 21 makes initial settings for a process of generating an artificial noise series. In particular, the correlation series generator 21 initializes and sets a variable i as 1. The variable i is used to identify the symbols of a data series. The correlation series generator 21 also obtains a threshold C. In the example depicted in FIG. 5, the threshold C corresponds to a coefficient CS-AN indicating the correlation between the data series and the artificial noise series. The threshold C is determined in advance through, for example, a simulation and stored in a memory provided for the wireless device 10.
