# Techniques for System Information Broadcast in Cell-Free Massive MIMO

## TL;DR

This paper investigates system information broadcast in cell-free massive MIMO, focusing on outage rate, coverage, and pilot/data power optimization without channel state information, using space-time codes and grouping strategies.

## Contribution

It introduces a heuristic power optimization method and analyzes access point grouping for improved system information broadcast in cell-free massive MIMO.

## Key findings

- Space-time codes enhance performance in system info broadcast.
- Heuristic power optimization improves outage rate.
- Access point grouping affects coverage probability.

## Abstract

We consider transmission of system information in a cell-free massive MIMO system, when the transmitting access points do not have any channel state information and the receiving terminal has to estimate the channel based on downlink pilots. We analyze the system performance in terms of outage rate and coverage probability, and use space-time block codes to increase performance. We propose a heuristic method for pilot/data power optimization that can be applied without any channel state information at the access points. We also analyze the problem of grouping the access points, which is needed when the single-antenna access points jointly transmit a space-time block code.