Massive MIMO With Circular Antenna Array: Design, Implementation, and Validation

Massive MIMO is a key technology for the current and next-generation cellular standards to achieve multi-fold improvements in the spectral efficiency of the network. Various demonstrations of this Massive MIMO technology in the existing literature transmit data to a maximum of 15 users simultaneously in the downlink while using 64 to 100 antenna ports at the base station. In this paper, we present in detail the design and implementation of our Large-scale Massive MIMO testbed, where we demonstrate a further maximization of the user pairing to realize the high network capacities achievable with massive MIMO technology. This is the first testbed implementation that demonstrates as high as 24 user pairing in downlink by utilizing 192 antenna elements (48 antenna ports) at the base station. This high user pairing capability helps the network operators to support as many users in a limited amount of spectrum and achieve multifold improvement in the network capacity. Further, this is a first step in the direction of understanding the real-world limitations of Massive MIMO systems in a variety of deployment scenarios and under constraints such as antenna array sizes, antenna array types such as circular versus rectangular, and indoor versus outdoor deployment, among others. All the analysis is backed by detailed experiments that are described in this paper.