Multi-RU Joint Precoding With Rate Guarantee Constraint and Erroneous Channel Estimation

To meet stringent service requirements in 5G at reasonable CapEx/OpEx, multi radio unit (RU) joint transmission has gained great attention. Optimal precoding design is a main concern in multi-RU joint transmission. In this paper, a new multi-RU joint precoding scheme is newly designed for sum-r ate-maximization with a minimum rate guarantee constraint under imperfect channel estimation. Owing to non-convexity of minimum rate guarantee constraints which causes huge computational complexity, we decouple the non-convex rate guarantee constraint into two convex constraints; desired signal constraint and interference constraint. And then, we propose a computationally efficient algorithm to find the suboptimal solution by iteratively solving two convex suboptimization problems. Through intensive simulations, the performance of the proposed scheme is evaluated and found to be superior compared with two previous schemes as well as the small-cell base station (SBS) transmission scheme.