# Efficient Channel AoD/AoA Estimation Using Widebeams for Millimeter Wave MIMO Systems

## TL;DR

This paper introduces a high-resolution, low-overhead method for estimating channel AoD and AoA in mmWave MIMO systems using widebeams and auxiliary-beam-pair techniques, optimized for hybrid transceivers.

## Contribution

It proposes a novel widebeam-based channel estimation method with auxiliary-beam-pair for hybrid transceivers, reducing overhead while maintaining high resolution.

## Key findings

- Achieves high-resolution AoD/AoA estimates with lower overhead.
- Uses linear combination of DFT vectors to construct widebeams.
- Numerical results demonstrate improved efficiency over previous methods.

## Abstract

Using millimeter-wave (mmWave) bands is expected to provide high data rates through large licensed and unlicensed spectrum. Due to large path loss and sparse scattering propagation properties, proper beam alignment is important in mmWave systems. Small carrier wavelengths at mmWave bands let wireless communication systems use large antenna arrays to provide sufficient beamforming gain with highly directional beams. Hence, high resolution channel angle-of-departure (AoD) and angle-of-arrival (AoA) estimation is crucial for beam alignment to get the advantages of large beamforming gain. Using large antenna arrays, however, can lead to high system complexity and channel estimation overhead. This paper proposes a channel AoD/AoA estimation technique using widebeams to lower estimation overhead and auxiliary-beam-pair (ABP) to get high resolution channel AoD/AoA estimates considering hybrid transceiver structures. To fully use the hybrid transceiver structures, the linear combination of discrete Fourier transform (DFT) vectors is considered to construct widebeams. Numerical results show that the proposed estimator can get high resolution channel AoD/AoA estimates with lower overhead compared to previous estimators.