# Downlink Goodput Analysis for D2D Underlaying Massive MIMO Networks

## TL;DR

This paper analyzes the downlink goodput in massive MIMO networks with co-channel device-to-device communications, providing analytical expressions for performance and trade-offs, validated by simulations.

## Contribution

It derives asymptotic signal-to-interference ratios and closed-form goodput approximations for D2D underlay massive MIMO, enabling system design insights.

## Key findings

- Analytical expressions match simulation results.
- Trade-offs between downlink and D2D communications are characterized.
- Performance region for improved spectral efficiency identified.

## Abstract

The performance of downlink massive multiple-input-multiple-output networks with co-channel device-to-device communications is investigated in this paper. Specifically, we consider a cellular network with sufficient number of antennas at the base station and typical hexagonal cell coverage, where the cell users and device-to-device transmitters are randomly and uniformly distributed. To obtain the analytical expressions of system-level performance, the asymptotic signal-to-interference ratios for both downlink and device-to-device links are first obtained, which depend on the pathloss and small-scale fading of the interference channels. Since these information may not be available at the service base station or device-to-device transmitters, there exists a chance of packet outage. Therefore, we continue to derive the closed-form approximation of the average goodput, which measures the average number of information bits successfully delivered to the receiver. Hence, the system design trade-off between downlink and co-channel device-to-device communications can be investigated analytically. Moreover, the performance region in which the co-channel device-to-device communications could lead to better overall spectral efficiency can be obtained. Finally, it is shown by simulations that the analytical results matches the actual performance very well.