  In this paper, wireless power transfer and cooperative jamming (CJ) are
combined to enhance physical security in public transportation networks. First,
a new secure system model with both fixed and mobile jammers is proposed to
guarantee secrecy in the worst-case scenario. All jammers are endowed with
energy harvesting (EH) capability. Following this, two CJ based schemes, namely
B-CJ-SRM and B-CJ-TPM, are proposed, where SRM and TPM are short for secrecy
rate maximization and transmit power minimization, respectively. They
respectively maximize the secrecy rate (SR) with transmit power constraint and
minimize the transmit power of the BS with SR constraint, by optimizing
beamforming vector and artificial noise covariance matrix. To further reduce
the complexity of our proposed optimal schemes, their low-complexity (LC)
versions, called LC-B-CJ-SRM and LC-B-CJ-TPM are developed. Simulation results
show that our proposed schemes, B-CJ-SRM and B-CJ-TPM, achieve significant SR
performance improvement over existing zero-forcing and QoSD methods.
Additionally, the SR performance of the proposed LC schemes are close to those
of their original versions.
