A Practical Implementation of mmWave NOMA With IRS-Aided Indoor Coverage Extension

This work presents a practical implementation that integrates three emerging wireless technologies: millimeter-wave (mmWave) communications, non-orthogonal multiple access (NOMA), and intelligent reflective surfaces (IRS). The goal is to provide multi-user mmWave indoor coverage in an indoor setting. Coverage in the mmWave band, often affected by blind spots, is extended by the ad-hoc design and deployment of a fully passive IRS that requires no power supply. Contrary to the use of a reconfigurable intelligent surface (RIS), this solution lacks the dynamic reconfigurability of the relay but offers a low-cost, easy-to-deploy alternative with zero power consumption. The integration with power-domain NOMA provides increased spectral efficiency by multiplexing two users in the same frequency, time and code slot. To the best of our knowledge, this is the first mmWave NOMA implementation and the first prototype that includes both NOMA and IRS. The radio frequency (RF) design ensures a bandwidth of 400 MHz centered at 24.45 GHz, with the IRS covering an angular synthesized margin of 10 degrees when illuminated by a half-power beamwidth of less than 3 degrees. The communication link is evaluated through over-the-air (OTA) measurements of channel power, error vector magnitude (EVM) and symbol error rate (SER), considering different user positions and superposition coding strategies. The system achieves a spectral efficiency of up to 4.62 bps/Hz while serving two users per frequency subchannel with a SER below 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup>.