In future practical deployments of massive multi-input multi-output (MIMO)systems, the number of radio frequency (RF) chains at the base stations (BSs)may be much smaller than the number of BS antennas to reduce the overallexpenditure. In this paper, we propose a novel design framework for joint dataand artificial noise (AN) precoding in a multiuser massive MIMO system withlimited number of RF chains, which improves the wireless security performance.With imperfect channel state information (CSI), we analytically derive anachievable lower bound on the ergodic secrecy rate of any mobile terminal (MT),for both analog and hybrid precoding schemes. The closed-form lower bound isused to determine optimal power splitting between data and AN that maximizesthe secrecy rate through simple one-dimensional search. Analytical andnumerical results together reveal that the proposed hybrid precoder, althoughsuffers from reduced secrecy rate compared with theoretical full-dimensionalprecoder, is free of the high computational complexity of large-scale matrixinversion and null-space calculations, and largely reduces the hardware cost.
展开▼
