  In this paper, we investigate the artificial noise-aided jamming design for a
transmitter equipped with large antenna array in Rician fading channels. We
figure out that when the number of transmit antennas tends to infinity, whether
the secrecy outage happens in a Rician channel depends on the geometric
locations of eavesdroppers. In this light, we first define and analytically
describe the secrecy outage region (SOR), indicating all possible locations of
an eavesdropper that can cause secrecy outage. After that, the secrecy outage
probability (SOP) is derived, and a jamming-beneficial range, i.e., the
distance range of eavesdroppers which enables uniform jamming to reduce the
SOP, is determined. Then, the optimal power allocation between messages and
artificial noise is investigated for different scenarios. Furthermore, to use
the jamming power more efficiently and further reduce the SOP, we propose
directional jamming that generates jamming signals at selected beams (mapped to
physical angles) only, and power allocation algorithms are proposed for the
cases with and without the information of the suspicious area, i.e., possible
locations of eavesdroppers. We further extend the discussions to multiuser and
multi-cell scenarios. At last, numerical results validate our conclusions and
show the effectiveness of our proposed jamming power allocation schemes.
