  Conventionally, interference and noise are treated as catastrophic elements
in wireless communications. However, it has been shown recently that exploiting
known interference constructively can even contribute to signal detection
ability at the receiving end. This paper exploits this concept to design
artificial noise (AN) beamformers constructive to the intended receiver (IR)
yet keeping AN disruptive to possible eavesdroppers (Eves). The scenario
considered here is a multiple-input single-output (MISO) wiretap channel with
multiple eavesdroppers. Both perfect and imperfect channel information have
been considered. The main objective is to improve the receive
signal-to-interference and noise ratio (SINR) at IR through exploitation of AN
power in an attempt to minimize the total transmit power, while confusing the
Eves. Numerical simulations demonstrate that the proposed constructive AN
precoding approach yields superior performance over conventional AN schemes in
terms of transmit power as well as symbol error rate (SER).
