# Sequential Hybrid Beamforming Design for Multi-Link mmwave Communication

## TL;DR

This paper introduces a sequential hybrid beamforming method for multi-link mmWave communication, enabling simultaneous multi-stream transmission with minimal disruption and improved robustness against signal blockage.

## Contribution

It proposes a novel two-step hybrid beamforming design with a parallel beam search scheme for efficient multi-link mmWave communication.

## Key findings

- Enables secondary link establishment without interrupting baseline communication.
- Provides a method for beam search that avoids system disruption.
- Offers a backup beam selection strategy for signal blockage scenarios.

## Abstract

In this paper, we propose a sequential hybrid beamforming design for multi-link transmission over mmwave frequency bands. As a starting point, a baseline data communication link is established via traditional analog beamforming at both the BS and UE. If an extra RF chain is available at the UE, it can continue to probe the propagation environment at the same frequencies. In case the environment is favorable and system resources allow, a secondary data communication link is established to enable multi-stream transmission. In principle, the secondary link could be served by the same BS and/or one or several other BS(s). To initialize the secondary data communication link, a parallel beam search scheme is proposed, which helps the UE/BS to find a suitable beam pair with given optimization criteria without interrupting the baseline data communication. By applying the proposed two-step approach, hybrid beamforming becomes an add-on feature that can be easily switched on over an analog beamforming enabled system without interrupting its operation whenever system requires. Meanwhile, the information obtained by deploying the proposed parallel beam search scheme can also be used for deciding a back-up beam pair if signal blockage occurs to the baseline data communication link.

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Source: https://tomesphere.com/paper/1705.04946