# Massive MIMO Extensions to the COST 2100 Channel Model: Modeling and Validation

## TL;DR

This paper extends the COST 2100 channel model for massive MIMO systems by introducing visibility regions at both the base station and mobile station sides, supported by measurement-based statistical analysis and validation.

## Contribution

It proposes new models for cluster and MPC visibility regions, including their statistical distributions, and validates these extensions through analysis and simulations.

## Key findings

- BS-VR lifetimes are exponentially distributed.
- Number of BS-VRs follows a Poisson distribution.
- MPC lifetimes and radii are lognormally distributed.

## Abstract

To enable realistic studies of massive multiple-input multiple-output systems, the COST 2100 channel model is extended based on measurements. First, the concept of a base station-side visibility region (BS-VR) is proposed to model the appearance and disappearance of clusters when using a physically-large array. We find that BS-VR lifetimes are exponentially distributed, and that the number of BS-VRs is Poisson distributed with intensity proportional to the sum of the array length and the mean lifetime. Simulations suggest that under certain conditions longer lifetimes can help decorrelating closely-located users. Second, the concept of a multipath component visibility region (MPC-VR) is proposed to model birth-death processes of individual MPCs at the mobile station side. We find that both MPC lifetimes and MPC-VR radii are lognormally distributed. Simulations suggest that unless MPC-VRs are applied the channel condition number is overestimated. Key statistical properties of the proposed extensions, e.g., autocorrelation functions, maximum likelihood estimators, and Cramer-Rao bounds, are derived and analyzed.