As depicted in FIG. 4, the wireless device 10 includes a receiver 11, a signal generator 12, a signal combiner 13, a transmitter 14, and a plurality of transmission antennas A1-A3. However, the wireless device 10 may include functions or elements that are not depicted in FIG. 4. For example, the wireless device 10 may include one or more reception antennas.

The receiver 11 receives a wireless signal transmitted from another wireless device. Each wireless device periodically transmits a pilot signal. The pilot signal has a known transmission power and a known bit pattern. Thus, the receiver 11 can estimate the state of a wireless channel by receiving and demodulating the pilot signal. In this example, the receiver 11 receives and demodulates a pilot signal transmitted from the destination node 2 so as to estimate the wireless channel H between the wireless device 10 and the destination node 2. Channel information indicating the wireless channel H is supplied from the receiver 11 to the signal combiner 13.

The signal generator 12 generates a data series and artificial noise series from data S. In this example, a data series S and artificial noise series AN1 and AN2 are generated. Data S is supplied from an application (or application layer) to the wireless device 10. There are correlations between the data series and the artificial noise series, as will be described hereinafter in detail. When a plurality of artificial noises are generated, there will also be correlations between these artificial noises.