# Real-Time Millimeter-Wave MIMO Channel Sounder for Dynamic Directional Measurements

arXiv: https://arxiv.org/abs/1807.11921 · HTML: https://mlsanity.com/paper/1807.11921/

## Key facts

- Cited by 3 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 31 Jul 2018.

## Built on by (most cited first, 3 of 3)

- [Multiverse at the Edge: Interacting Real World and Digital Twins for Wireless Beamforming](https://mlsanity.com/paper/2305.10350/) (2023)
- [AirLLM: Diffusion Policy-based Adaptive LoRA for Remote Fine-Tuning of LLM over the Air](https://mlsanity.com/paper/2507.11515/) (2025)
- [Multi-User mmWave Beam and Rate Adaptation via Combinatorial Satisficing Bandits](https://mlsanity.com/paper/2604.14908/) (2026)

## Abstract (arXiv)

In this paper, we present a novel real-time multiple-input-multiple-output (MIMO) channel sounder for the 28 GHz band. Until now, most investigations of the directional characteristics of millimeter-wave channels have used mechanically rotating horn antennas. In contrast, the sounder presented here is capable of performing horizontal and vertical beam steering with the help of phased arrays. Due to its fast beam-switching capability, the proposed sounder can perform measurements that are directionally resolved both at the transmitter(TX) and receiver (RX) in 1.44 milliseconds compared to the minutes or even hours required for rotating horn antenna sounders. This not only enables measurement of more TX-RX locations for a better statistical validity but also allows to perform directional analysis in dynamic environments. The short measurement time combined with the high phase stability limits the phase drift between TX and RX, enabling phase-coherent sounding of all beam pairs even when TX and RX have no cabled connection for synchronization without any delay ambiguity. Furthermore, the phase stability over time enables complex RX waveform averaging to improve the signal to noise ratio during high path loss measurements. The paper discusses both the system design as well as the measurements performed for verification of the sounder performance. Furthermore, we present sample results from double directional measurements in dynamic environments.