Title
Linear Precoding Based on Polynomial Expansion: Reducing Complexity in Massive MIMO
Abstract
Massive multiple-input multiple-output (MIMO) techniques have the potential to bring tremendous improvements in spectral efficiency to future communication systems. Counterintuitively, the practical issues of having uncertain channel knowledge, high propagation losses, and implementing optimal non-linear precoding are solved more or less automatically by enlarging system dimensions. However, the computational precoding complexity grows with the system dimensions. For example, the close-to-optimal and relatively "antenna-efficient" regularized zero-forcing (RZF) precoding is very complicated to implement in practice, since it requires fast inversions of large matrices in every coherence period. Motivated by the high performance of RZF, we propose to replace the matrix inversion and multiplication by a truncated polynomial expansion (TPE), thereby obtaining the new TPE precoding scheme which is more suitable for real-time hardware implementation and significantly reduces the delay to the first transmitted symbol. The degree of the matrix polynomial can be adapted to the available hardware resources and enables smooth transition between simple maximum ratio transmission and more advanced RZF. By deriving new random matrix results, we obtain a deterministic expression for the asymptotic signal-to-interference-and-noise ratio (SINR) achieved by TPE precoding in massive MIMO systems. Furthermore, we provide a closed-form expression for the polynomial coefficients that maximizes this SINR. 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.
Year
DOI
Venue
2016
10.1186/s13638-016-0546-z
EURASIP J. Wireless Comm. and Networking
Keywords
Field
DocType
Linear precoding,Massive MIMO,Multiuser systems,Polynomial expansion,Random matrix theory
Mathematical optimization,Computer science,Matrix (mathematics),MIMO,Degree of a polynomial,Spectral efficiency,Zero-forcing precoding,Matrix polynomial,Polynomial expansion,Precoding
Journal
Volume
Issue
ISSN
2016
1
1687-1499
Citations 
PageRank 
References 
15
0.84
34
Authors
4
Name
Order
Citations
PageRank
Axel Müller1535.38
Abla Kammoun220430.92
Emil Björnson33446171.49
Merouane Debbah465034.40