Performance of Slotted ALOHA in User-Centric Cell-Free Massive MIMO

TL;DR

This paper analyzes the performance of slotted ALOHA in user-centric cell-free massive MIMO, highlighting its efficiency in IoT scenarios with sporadic traffic and comparing it with other network types.

Contribution

It provides a sum-throughput expression for slotted ALOHA in user-centric cell-free massive MIMO and compares its performance and limitations with other network architectures.

Findings

Good trade-off between performance and fronthaul load at low activation probabilities

User-centric cell-free massive MIMO outperforms other networks in certain regimes

The scheme effectively supports sporadic IoT traffic

Abstract

To efficiently utilize the scarce wireless resource, the random access scheme has been attaining renewed interest primarily in supporting the sporadic traffic of a large number of devices encountered in the Internet of Things (IoT). In this paper we investigate the performance of slotted ALOHA -- a simple and practical random access scheme -- in connection with the grant-free random access protocol applied for user-centric cell-free massive MIMO. More specifically, we provide the expression of the sum-throughput under the assumptions of the capture capability owned by the centralized detector in the uplink. Further, a comparative study of user-centric cell-free massive MIMO with other types of networks is provided, which allows us to identify its potential and possible limitation. Our numerical simulations show that the user-centric cell-free massive MIMO has a good trade-off between performance and fronthaul load, especially at low activation probability regime.