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08) Sub-system testing of Xilinx O-RU
with Keysight O-DU emulator

Companies Participating
in this Scenario

Xilinx provided O-RU

Keysight provided Open RAN Studio (O-DU emulator), N9020B MXA X-Series Signal Analyzer, EXG X-Series Signal Generator

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Testbed setup

The connection details of the hardware in the lab are in the network topology diagram below.

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Device Under Test
Xilinx O-RU Array 4064

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  • • mMIMO O-RU
  • • 64 TRX
  • • LTE TDD Band 40, 2.3-2.4 GHz
  • • CAT A O-RU, functional split 7.2x
  • • 2x 20 MHz
  • • 16 antenna streams DL, 8 streams UL
  • • 2 x 10G Ethernet eCPRI fronthaul
  • • Digital beamforming, real-time weight-based
  • • Block floating point fronthaul compression

Test scenarios introduction

During the 2020 join O-RAN and TIP Plugfest Europe, Xilinx tested its Array 4064, a massive MIMO O-RU. The test setup was Setup #1a: O-RU in isolation, i.e. the O-RU was the device under test.
Test equipment was provided by Keysight in the form of Keysight’s OpenRAN Studio and OpenRAN player, acting as an O-DU emulator to stimulate the O-RU with Control and User plane packets, and a Keysight Spectrum Analyzer acting as a UE emulator to receive and demodulate signals. For synchronization, option LLS-C4 was used, with a GPS emulator feeding both the O-RU and a PTP Grandmaster, the latter in turn providing PTP to the O-DU emulator. With this scenario, the conformant implementation of the O-RAN fronthaul interface on the Xilinx O-RU can be verified. At the same time, it can show RF performance of the O-RU under test, which – although not in the scope of the O-RAN specification – is an important factor to give customers confidence in an O-RU product.
In addition, Xilinx tested its M-Plane implementation by using Keysight’s M-Plane client.

  • Scenarios S-Plane

O-RU synchronizing to GNSS (LLS-C4)

The purpose of this test is to validate that Xilinx O-RU is correctly synchronizing to GPS antenna in LLS-C4 mode.

  • Scenarios C/U -Plane

O-RU Scenario Class
Beamforming 3GPP DL – No Beamforming

The purpose of this test is to ensure the radio can transmit a basic 3GPP test frame with no beamforming
(beamId=0x000) and with one spatial stream (single eAxC). This test focuses on the downlink.

O-RU Scenario Class Compression
Non-Static (NS) Block Floating Point

The purpose of this test is to validate the correct encoding of IQ data under the following conditions.

• RU Non-Static compression configurations
• Block Floating point IQ data format
• Uplink/downlink

O-RU Scenario Class
DLM Downlink – Positive testing

This test case validates that the timing on the air interface is according to requirements
specified in the CUS Specification when the C-Plane and the U-Plane messages are received
within the O-RU’s reception windows.

O-RU Scenario Class
DLM Downlink – Negative testing

This test case validates that the transmission of the U-Plane data in uplink direction is transmitted
correctly by the O-RU within its transmission window.

O-RU Scenario Class Base 3GPP DL - LTE

The purpose of this test is to ensure the radio can transmit a basic 3GPP test frame using the default parameters.

  • Scenarios M-Plane

Retrieval without Filter Applied

This test scenario validates that the O-RU NETCONF Server properly executes a general
get command and replies with all the information elements of the NETCONF SERVER.

Retrieval with the Filter applied

This scenario validates that the O-RU NETCONF Server properly executes a get command with a
filter applied and responds with information elements of the given filter.

Transport and Handshake
in IPv4 Environment (positive case)

This scenario validates that the O-RU NETCONF server properly executes the session establishment procedure
with a TCP three-way handshake and a successfully authenticated SSH session.

Transport and Handshake
in IPv4 Environment (negative case)

This scenario validates that the O-RU NETCONF server rejects the session establishment when a NETCONF
client wants to establish an SSH session to the O-RU NETCONF server with the wrong credentials.

M-Plane connection supervision
(positive case)

This test validates that the O-RU manages the connection supervision process correctly and responds to the
Remote Procedure Call (RPC) "supervision_watchdog_reset"

Subscription to Notifications

The purpose of the test is to validate the O-RU NETCONF server properly handles
a NETCONF subscription to notifications sends a response for the RPC "create subscription".

Testing Results/Summary

In this test, Xilinx O-RU connects to GPS antenna in LLS-C4 mode to do the clock synchronization and connects over O-RAN fronthaul 7-2x split to the Keysight O-DU emulator. The test focus on the RF interface, Keysight VSA (Vector Signal Analyzer) as the Radio analyzer.

Xilinx test cases mainly do C/U Plane conformance tests with block floating point 12 bit no beamforming configuration. Based on the log of Xilinx O-RU and the screenshot of the Keysight VSA output, the Radio KPI (EVM, Power, etc.) achieved the stands of both O-RAN and 3GPP specifications.

We validate the LTE Radio Performance tests as outlined in TestModel3.1 EVM measurements for the 256QAM modulation and Occupied Bandwidth.

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Benefits for the Industry

The main benefit of O-RAN conformant O-RUs is that Network Operators can integrate them with any conformant O-DU, thereby avoiding a vendor lock-in that was often prevalent with older fronthaul solutions. The tests performed covered all the major aspects of an O-RU, including the real-time fronthaul interface (C-/U-/S-Plane), non-real-time capabilities (M-Plane), as well as RF performance. Hence, the participation in the plug-fest increased the confidence in the conformity of the O-RU designed using Xilinx technology.

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