# RIS and Cell-Free Massive MIMO: A Marriage For Harsh Propagation Environments

@article{Chien2021RISAC, title={RIS and Cell-Free Massive MIMO: A Marriage For Harsh Propagation Environments}, author={Trinh Van Chien and Hien Quoc Ngo and Symeon Chatzinotas and Marco di Renzo and Bj{\"o}rn E. Ottersten}, journal={ArXiv}, year={2021}, volume={abs/2109.05444} }

This paper considers Cell-Free Massive Multiple Input Multiple Output (MIMO) systems with the assistance of an RIS for enhancing the system performance. Distributed maximum-ratio combining (MRC) is considered at the access points (APs). We introduce an aggregated channel estimation method that provides sufficient information for data processing. The considered system is studied by using asymptotic analysis which lets the number of APs and/or the number of RIS elements grow large. A lower bound… Expand

#### One Citation

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

- Computer Science, Mathematics
- ArXiv
- 2021

An aggregated channel estimation approach is introduced that provides sufficient information for data processing with the main benefit of reducing the overhead required for channel estimation and a simple control scheme for controlling the configuration of the scattering elements of the RIS is shown to increase the channel estimation quality, and, hence, the system performance. Expand

#### References

SHOWING 1-10 OF 13 REFERENCES

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

- Computer Science, Mathematics
- ArXiv
- 2021

An aggregated channel estimation approach is introduced that provides sufficient information for data processing with the main benefit of reducing the overhead required for channel estimation and a simple control scheme for controlling the configuration of the scattering elements of the RIS is shown to increase the channel estimation quality, and, hence, the system performance. Expand

Cell-Free Massive MIMO Versus Small Cells

- Computer Science, Mathematics
- IEEE Transactions on Wireless Communications
- 2017

Under uncorrelated shadow fading conditions, the cell-free scheme provides nearly fivefold improvement in 95%-likely per-user throughput over the small-cell scheme, and tenfold improvement when shadow fading is correlated. Expand

Achievable Rate Optimization for Aerial Intelligent Reflecting Surface-Aided Cell-Free Massive MIMO System

- Computer Science
- IEEE Access
- 2021

This article considers a new application scenario for the IRS — an aerial IRS (AIRS)-aided cell-free massive MIMO system where multiple APs serve several users through an AIRS, and proposes a fast optimal location search algorithm base on the path loss model to determine the optimal location of the AIRS and decrease the computational complexity. Expand

Capacity Improvement in Wideband Reconfigurable Intelligent Surface-Aided Cell-Free Network

- Computer Science, Engineering
- 2020 IEEE 21st International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
- 2020

The proposed RIS-aided cell-free network is inspired by the recently proposed technique called reconfigurable intelligent surface (RIS), and the network capacity of the proposed scheme can be improved significantly. Expand

Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming

- Computer Science, Mathematics
- IEEE Transactions on Wireless Communications
- 2019

Simulation results demonstrate that an IRS-aided single-cell wireless system can achieve the same rate performance as a benchmark massive MIMO system without using IRS, but with significantly reduced active antennas/RF chains. Expand

Robust Probabilistic-Constrained Optimization for IRS-Aided MISO Communication Systems

- Computer Science
- IEEE Wireless Communications Letters
- 2021

This letter formulates and solves a joint active/passive beamforming optimization problem in multiple-input single-output systems with the support of an intelligent reflecting surface and introduces an optimization problem to minimize the total transmit power subject to maintaining the users’ signal-to-interference-plus-noise-ratio coverage probability above a predefined target. Expand

Random Variables and Probability Distributions

- Mathematics
- 1962

A random variable is a function with a certain restrictive property. This chapter provides an overview of the random variables and probability distributions. It illustrates algebraic operations on… Expand

Fundamentals of statistical signal processing: estimation theory

- Mathematics
- 1993

Minimum variance unbiased estimation Cramer-Rao lower bound linear models general minimum variance unbiased estimation best linear unbiased estimators maximum likelihood estimation least squares… Expand

Intelligent Reflecting Surface Enhanced Wireless Networks: Two-Timescale Beamforming Optimization

- Computer Science, Mathematics
- IEEE Transactions on Wireless Communications
- 2021

A new two-timescale (TTS) transmission protocol is proposed to maximize the achievable average sum-rate for an IRS-aided multiuser system under the general correlated Rician channel model and a general TTS stochastic successive convex approximation (SSCA) algorithm is proposed. Expand

Achievable Rate Optimization for MIMO Systems With Reconfigurable Intelligent Surfaces

- Computer Science, Mathematics
- IEEE Transactions on Wireless Communications
- 2021

This work proposes an iterative optimization algorithm that is based on the projected gradient method (PGM) and derives the step size that guarantees the convergence of the proposed algorithm and defines a backtracking line search to improve its convergence rate. Expand