Several gaps and errors in (B. Fang et al., “AN-aided secrecy precoding for SWIPT in cognitive MIMO broadcast channels,” IEEE Commun. Lett., vol. 19, no. 9, pp. 1632–1635, Sep. 2015)… Click to show full abstract
Several gaps and errors in (B. Fang et al., “AN-aided secrecy precoding for SWIPT in cognitive MIMO broadcast channels,” IEEE Commun. Lett., vol. 19, no. 9, pp. 1632–1635, Sep. 2015) are identified. Their corrections as well as new results are reported. After these corrections in the analysis, the successive convex approximation algorithm for secrecy rate maximization with artificial noise is shown to generate an increasing, converging sequence of secrecy rates. For a degraded channel, (i) this sequence converges to the maximum secrecy rate of the channel, and (ii) it is optimal to use no artificial noise. For a reversely-degraded channel, the maximum achievable secrecy rate is zero.
               
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