# On-off Analog Beamforming for Massive MIMO

## TL;DR

This paper introduces on-off analog beamforming (OABF) for massive MIMO, replacing complex phase shifters with simple switches, achieving good performance with lower hardware and algorithmic complexity.

## Contribution

It proposes a novel on-off analog beamforming architecture that reduces hardware complexity and provides theoretical guarantees of full diversity and array gains.

## Key findings

- OABF achieves full diversity and array gains.
- OABF reduces hardware complexity by replacing phase shifters with switches.
- Numerical results confirm theoretical performance predictions.

## Abstract

This paper investigates a new analog beamforming architecture for massive multiple-input multiple-output (MIMO) systems, where each of the multiple transmit antennas is switched to be on or off to form a beam according to the channel state information at transmitters. This on-off analog beamforming (OABF) scheme has the advantages in terms of both hardware complexities and algorithmic complexities. OABF can completely remove the high-cost, power-consuming and bulky analog phase-shifters that are extensively employed by traditional analog beamforming schemes; it only requires the deployment of low-cost analog switches that are easy to implement. Moreover, we show that the beams formed by such simple antenna on-off switch operations can achieve rather good performances with low-complexity beamforming algorithms. Specifically, we first propose two optimal signal-to-noise ratio maximization algorithms to determine the on-off state of each switch under the per-antenna power constraint and the total power constraint, respectively. After that, we theoretically prove that OABF can achieve the full diversity gain and the full array gain with complexities up to a polynomial order. Numerical results are consistent with our theoretical analysis. We believe that the simple structure of OABF makes massive MIMO much easier to implement in real systems.