PROPSIM Massive MIMO Test Solution

Introduction

The evolution of 5G networks introduces new challenges in testing and validating base station performance. New base station products support multiple access technologies, are flexible in deployment, and offer substantial capacity to end users. However, this also leads to increased system complexity. Key performance challenges in 5G networks involve beam management procedures and interoperability between user equipment (UEs) and the network. Technologies such as Massive MIMO, multi-user, and beamforming add further complexity to 5G NR testing compared to previous generations.

Massive MIMO Testing Challenges

Massive MIMO technology enhances network capacity and data performance through beamforming and spatial multiplexing. However, successful implementation depends on several factors, including effective beam precoding, management of UE movement, and interference mitigation. Any issues in these areas can lead to degraded and unstable data performance. Massive MIMO testing requires a high number of RF ports, increasing lab test setup complexity. Additionally, beamforming necessitates precise phase coherence, imposing higher requirements on test setup calibration.

Keysight’s S8803A Toolset

Keysight’s S8803A Massive MIMO Base Station Fading Performance Toolset addresses these challenges by providing configurations for comprehensive beam testing. For a full 64TR base station, it supports full spatial, azimuth, and elevation beam testing. A reduced hardware configuration with a single PROPSIM F64 unit and two Antenna Interface Units (AIUs) is also available. The PROPSIM platform offers high spatial accuracy, enabling validation of baseline data performance and quick debugging of field issues.

Channel Emulation

The PROPSIM Channel Emulator replicates real-life radio conditions, including all phenomena between a transmitter and a receiver. This method is reliable and repeatable, providing a significant advantage in ensuring system-level performance. The AIUs combine vertical co-polarized elements, reducing the number of required fader RF ports.

Beamforming and MU-MIMO

Beamforming is a signal processing technology that reduces interference and enhances spectral efficiency by directing targeted beams of data to users. In 5G FR1 Massive MIMO base stations, digital beamforming technology is used, where signals are weighted in base station baseband precoding before RF transmission. This allows for the formation of multiple beams in different shapes and directions simultaneously, essential for Multi-User MIMO (MU-MIMO), which improves network capacity by reusing time-frequency resource blocks for multiple users.

Test Setup Description

The S8803A test setup involves geometric channel profiles combined with antenna arrays in the PROPSIM emulation file. The base station connects to PROPSIM via AIUs, enabling bidirectional and reciprocal use of UE-specific beamforming, 5G link channel estimation methods, and feedback mechanisms.

The physical setup connects 64 base station antenna ports to two AIUs, with cabling arranged so that polarizations connect to separate AIUs. Each AIU combines multiple BS antenna ports into a single RF line connected to PROPSIM, effectively simulating different UE scenarios and elevations.

Scenario Creation

Test scenarios are created using PROPSIM software tools, including the Channel Studio GCM tool, which defines BS and UE locations, channel models, and antennas. For 5G-NR BTSAtt, the conductive test method is preferred over OTA due to practical constraints and cost considerations. The GCM tool enables the use of 3GPP CDL models and user-defined antennas.

Antenna Definitions and Mapping

A typical 64 port Massive MIMO antenna has dual-polarized elements arranged in an 8x4 topology. Antenna definitions and the mapping of physical antenna ports to the test setup are crucial. AIUs combine vertical columns, reducing the number of physical ports required. The GCM tool aids in defining antenna models and mapping ports, ensuring accurate simulation of real-world scenarios.

Calibration

Phase coherence is critical in massive MIMO setups. The Integrated Setup Calibration aligns PROPSIM port phases and levels, including cables and external RF components. The alignment process involves connecting AIU front-panel ports to UE antenna ports, with the software guiding the user through signal path measurements. This process ensures stable and accurate test setups, with periodic recalibration recommended.

Conclusion

The S8803A Massive MIMO Test Solution by Keysight provides a comprehensive approach to addressing 5G testing challenges. Through precise channel emulation, robust calibration processes, and detailed scenario creation, this toolset ensures reliable and repeatable testing of 5G Massive MIMO base stations, supporting the successful deployment and performance of next-generation networks.