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

TL;DR

This paper investigates the performance of slotted ALOHA in connection with the grant-free random access protocol applied for user-centric cell-free massive MIMO, and shows that the user-centric cell-free massive MIMO has a good trade-off between performance and fronthaul load, especially at low activation probability regime.

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.

Figures (4)

• Figure 1: Comparison between cellular networks, small-cell networks and user-centric cell-free networks. In our study, we ensure a fair comparison by maintaining the same number of base station antennas in each network system and an equal mean of active users over the same area size.
• Figure 2: The sum-throughput of various networks as a function of activation probability $\pi$ for $L=16$ and $N=4$
• Figure 3: The sum-throughput with respect to the number of antennas at each AP $N$ for $\pi=0.1$, $L=16$.
• Figure 4: The sum-throughput with respect to the number of APs $L$ for $\pi=0.1$, $L=16$.