  We propose a new location-based beamforming (LBB) scheme for wiretap
channels, where a multi-antenna source communicates with a single-antenna
legitimate receiver in the presence of a multi-antenna eavesdropper. We assume
that all channels are in a Rician fading environment, the channel state
information from the legitimate receiver is perfectly known at the source, and
that the only information on the eavesdropper available at the source is her
location. We first describe how the optimal beamforming vector that minimizes
the secrecy outage probability of the system is obtained, illustrating its
dependence on the eavesdropper's location. We then derive an easy-to-compute
expression for the secrecy outage probability when our proposed LBB scheme is
adopted. We also consider the positive impact a friendly jammer can have on our
beamforming solution, showing how the path to optimality remains the same.
Finally, we investigate the impact of location uncertainty on the secrecy
outage probability, showing how our solution can still allow for secrecy even
when the source only has a noisy estimate of the eavesdropper's location. Our
work demonstrates how a multi-antenna array, operating in the most general
channel conditions and most likely system set-up, can be configured rapidly in
the field so as to deliver an optimal physical layer security solution.
