Verifying O-RAN radio units that support M-MIMO beamforming

Your task: O-RUs supporting M-MIMO beamforming

Our O-RU test solution

Rohde & Schwarz is working with VIAVI Solutions to offer a powerful O-RU validation solution that supports M-MIMO with beamforming. The solution is in line with O-RAN ALLIANCE WG4.CONF and verifies that an O-RU can transmit a basic 3GPP test frame with predefined spatial beams. Comprehensive O-RU testing is possible – from functional verification and conformance to performance validation. The solution supports all beamforming variants, offering the broadest coverage on the market.

Existing O-RU tester users can easily upgrade a setup by adding a phase shift matrix (PSM) and an R&S®RTO oscilloscope to test M-MIMO with beamforming. The simple upgrade lets users maximize their test investments.

How to measure O-RU conformance

The VIAVI TM500 O-RU Tester (O-DU emulator) synchronizes and configures the O-RU under test. A Rohde & Schwarz signal generator, such as the R&S®SMW200A vector signal generator, provides the RF signals and waveforms, while a signal and spectrum analyzer such as the FSW signal and spectrum analyzer captures transmitted signals and analyzes I/Q data in the uplink and downlink.

By adding an R&S®RTO oscilloscope and connecting a PSM to the M-MIMO antenna ports on the O-RU, you can sequentially measure both downlink and uplink beamforming:

• The R&S®SMW200A vector signal generator produces an uplink signal that is injected into the PSM
• The PSM forms the appropriate uplink beam toward the O-RU
• The resulting I/Q data is captured and evaluated using the R&S®VSE vector signal explorer software

The whole test setup is fully automated and controlled by the O-RU Test Manager Application (O-TMA) from VIAVI to simplify O-RU conformance testing. Select the test case you want to run, and the test manager automatically triggers the configurations, runs the test case and provides a test report.

How to measure M-MIMO beamforming downlink/uplink (DL/UL) conformance

Once the test setup is configured, DL measurements start with the O-DU emulator inserting beam ID information into the I/Q packets and sending them over the open fronthaul (O-FH) interface to the O-RU.

After receiving and decoding the I/Q data stream, the O-RU reconstructs the waveform and transmits the RF signal over its antenna array. The signal is routed through the PSM to the R&S®RTO oscilloscope, where it is captured for analysis. Measurements are first taken across all antenna ports, followed by detailed evaluations of ports 2 through to the highest number supported by the O-RU (16, 32 or 64). The captured data is processed with R&S®VSE software and checked using predefined pass/fail thresholds.

Once all ports are measured, the system automatically generates result logs and summary files, with final values presented in a convenient table. If any antenna port exceeds the limits set by the test engineer, the test is flagged as a failure.

For uplink testing, the R&S®SMW200A vector signal generator creates the UL signal and feeds it into the PSM, which forms the matching uplink beam to the O-RU. The O-RU processes the received signal, and the resulting I/Q data is captured and analyzed by the TM500 O-RU Tester. The VIAVI O-TMA then provides a clear pass/fail report for all test results.