# Efficient Linear Precoding for Massive MIMO Systems using Truncated Polynomial Expansion

Conference Paper

### Authors:

Axel Müller; Abla Kammoun; Emil Björnson; Mérouane Debbah

### Source:

IEEE 8th Sensor Array and Multichannel Signal Processing Workshop (SAM), Coruna, Spain (2014)

### Abstract:

Large-scale multi-user multiple-input multiple-output techniques have been proposed as a solution to satisfy many requirements of next generation cellular systems. One downside of this approach is the increased computation complexity of the precoder, especially when relatively antenna-efficient'' regularized zero-forcing (RZF) is preferred to simple maximum ration transmission.
We introduce in this paper a new class of truncated polynomial expansion (TPE) based precoder for single cell systems. This technique mimics the advantages of RZF, while offering reduced and scalable computational complexity that can be implemented in a convenient pipelined fashion.
Using random matrix theory we provide a closed form expression of the received signal to interference and noise ratio under TPE precoding and compare it to the known optimal large scale RZF performance. Furthermore, the sum rate maximizing large scale polynomial coefficients are calculated.
By simulation, we find that to maintain a fixed per-user rate loss as compared to RZF, the polynomial degree does not need to scale with the system, but it should be increased with the quality of the channel knowledge and the signal-to-noise ratio.