Nested Hybrid Cylindrical Array Design and DoA Estimation for Massive IoT Networks

TL;DR

This paper introduces a novel hybrid cylindrical array design and a tensor-based DoA estimation algorithm for massive IoT networks, achieving high accuracy with reduced RF chains and computational complexity.

Contribution

It proposes a nested hybrid beamforming structure and a channel estimation method that preserve array DoF, along with a new tensor-based 2-D DoA estimation algorithm tailored for hybrid arrays.

Findings

Accurately estimates 2-D DoAs of many IoT devices.

Reduces RF chains while maintaining array DoF.

Improves DoA estimation accuracy with low complexity.

Abstract

Reducing cost and power consumption while maintaining high network access capability is a key physical-layer requirement of massive Internet of Things (mIoT) networks. Deploying a hybrid array is a cost- and energy-efficient way to meet the requirement, but would penalize system degree of freedom (DoF) and channel estimation accuracy. This is because signals from multiple antennas are combined by a radio frequency (RF) network of the hybrid array. This paper presents a novel hybrid uniform circular cylindrical array (UCyA) for mIoT networks. We design a nested hybrid beamforming structure based on sparse array techniques and propose the corresponding channel estimation method based on the second-order channel statistics. As a result, only a small number of RF chains are required to preserve the DoF of the UCyA. We also propose a new tensor-based two-dimensional (2-D) direction-of-arrival (DoA) estimation algorithm tailored for the proposed hybrid array. The algorithm suppresses the noise components in all tensor modes and operates on the signal data model directly, hence improving estimation accuracy with an affordable computational complexity. Corroborated by a Cramer-Rao lower bound (CRLB) analysis, simulation results show that the proposed hybrid UCyA array and the DoA estimation algorithm can accurately estimate the 2-D DoAs of a large number of IoT devices.