MMSE-Based Precoding for Rate Splitting Systems With Finite Feedback

In this letter, to tackle the inevitable effects of imperfect channel state information caused by finite feedback, we investigate a rate splitting transmission scheme proposed recently, which splits one symbol into a common part and a private part, and transmits signals simultaneously after superposition. First, we propose a minimum mean square error precoding to further suppress the imperfectness of the channel, in which random vector quantization is considered and a closed-form expression is derived. Then, utilizing an approximate expression of the quantization error, we develop a modified power allocation scheme for different parts of symbols by minimizing the sum-rate loss. Numerical results demonstrate the performance gains of the proposed schemes.