Massive MIMO for Massive Industrial Internet of Things Networks: Operation, Performance, and Challenges

Massive MIMO systems have received a great deal of attention as a means to improve both spectral efficiency (SE) and energy efficiency (EE) of wireless networks. While applying Massive MIMO to cellular networks has drawn significant attention, much less attention has been given to applying Massive MIMO to industrial Internet of things (IIoT) networks. The devices for IIoT networks have been continually growing, and to simultaneously support a large number of IIoT devices, orthogonal uplink reference signals (RSs) can be heavily reused, which severely compromises the quality of the channel estimation for all devices. This RS reuse Massive MIMO system can be successfully applied to IIoT networks to support a vast number of devices. In this paper, we provide the special characteristics of Massive MIMO applied to massive IIoT networks with respect to the operation, performance, and challenges. We present the technical overview of RS reuse Massive MIMO to realize low power, low latency, and low cost IIoT network, and then provide the performance using numerical results to verify the effectiveness of the system. Following this, we elaborate on the challenges associated with implementing these systems in reality, and offer insights into related issues that arise.