Lower Power in Scalable Cell-Free Massive MIMO with Symbol Level Precoding

Cell-free massive multiple-input multiple-output (CF mMIMO) system can eliminate cell boundary effect and provide more uniform service by cooperation of mass distributed access points (APs) at the cost of high power consumption. To address this issue, symbol-level precoding (SLP) can be used as an effective technique to reduce power consumption in CF mMIMO systems by using constructive interference (CI). In this paper, we consider a scalable CF mMIMO system (SCF) that clusters APs into multiple user-centric groups that can overlap. Then, an SCF system based on SLP is proposed, the minimum power consumption model of the system is established, and optimal solution is obtained by the convex optimization method. Finally, we compare and analyze the power consumption of traditional SCF system and the SLP-based SCF system. The simulation results show that the latter can greatly reduce the power consumption of the system compared with the former; when CF mMIMO system adopts SLP precoding, the number of UEs, APs and the order of the modulation scheme will all affect the power consumption.