In this letter, we propose a novel manifold-based algorithm to solve theconstant envelope (CE) precoding problem with interference exploitation. For agiven power budget, we design the precoded symbols subject to the CEconstraints, such that the constructive effect of the multi-user interference(MUI) is maximized. While the objective for the original problem isnon-differentiable on the complex plane, we consider the smooth approximationof its real representation, and map it onto a Riemannian manifold. By using theRiemmanian conjugate gradient (RCG) algorithm, a local minimizer can beefficiently found for the problem. The complexity of the algorithm isanalytically derived in terms of floating-points operations (flops) periteration. Numerical results show that the proposed algorithm outperforms theconventional methods on both symbol error rate and computational complexity.
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